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Nanomaterials for biofuel production using lignocellulosic waste
Abstract
Production of biofuels using second-generation, non-food, lignocellulosic waste biomass is a sustainable approach that solve the economic issues of fossil fuels and environmental pollution. The major issues of biofuel production are biomass complexity, pretreatment, enzyme denaturation and cost. This article reviews the application of nanomaterials for biofuel production from various lignocellulosic wastes.
... Physicochemical processes are reported expensive and produce toxic inhibitors (Prasad et al., 2020c). In converting biomass to sugars and further its transformation to ethanol, cellulase enzymes play a crucial role (Srivastava et al., 2017). However, enzyme production itself is the most cost-intensive step in the entire process and contributes B40% of the total cost (Srivastava et al., 2017;. ...
... In converting biomass to sugars and further its transformation to ethanol, cellulase enzymes play a crucial role (Srivastava et al., 2017). However, enzyme production itself is the most cost-intensive step in the entire process and contributes B40% of the total cost (Srivastava et al., 2017;. A significant challenge in making cellulosic ethanol economically viable is lowering enzymes' costs required to convert biomass to ethanol (Prasad et al., 2020c). ...
Nanotechnology for Biorefinery
2023, Pages 27-87
Chapter 2 - Nanomaterials used in biorefineries: types, properties, and synthesis methods
Author links open overlay panelBrandon Lowe, Amina Muhammad Ahmad, Jabbar Gardy, Ali Hassanpour
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https://doi.org/10.1016/B978-0-323-95965-0.00004-4
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Abstract
Countries are increasingly becoming aware of the urgent need to transition toward lower carbon dioxide emitting societies. While certain industries such as the transportation sector have been difficult to decarbonize thus far, continued development into biomass-derived fuels such as biodiesel will likely aid this transition. Traditionally, biodiesel has been made via a two-step homogeneous process, with acidic or basic catalysts required to improve reaction kinetics. More recent explorations into heterogeneous catalysis have facilitated simpler separation and recovery of catalyst from the produced biodiesel, without expensive cleanup prior to use.
The application of nanotechnology however has the potential to achieve even greater catalytic performances. By careful design of the nanomaterial, successful nanoscale catalysts have been synthesized with impressive yields, reaction kinetics, stability, impurity tolerance, and even magnetic separability. The field of nanocatalysis for biodiesel production continues to develop at pace and proves an exciting area of current research. The present chapter is focused on various types of nanomaterials that have been produced to date and their catalytic properties to the future potential for full-scale, industrial biorefinery operation.
... Cost-effectiveness The removal of nanoarchitectures by photons so that they reach the reactive site Previous studies also indicate that the addition of magnetic nanoparticles could influence the thermal stability and pH of cellulase enzymes and reduce the lag phase of microorganisms leading to improved hydrolysis [98]. In addition, the incorporation of magnetic nanoparticles (specifically Fe and Ni) to the bioreactor can enhance hydrogen yield because of their ability to bond to the active sites of the enzymes [99]. ...
... Nanomaterials could also be impactful in elevating the hydrogen yield of photo-fermentation [104]. The nitrogenase enzymes used during photo-fermentation are dominated by Fe acting as a major co-factor at the enzyme's active site [99]. Besides, the inclusion of Fe and Ni during photo-fermentation helps maintain the enzymes' structural integrity. ...
Nanomaterials are beginning to play an essential role in addressing the challenges associated with hydrogen production and storage. The outstanding physicochemical properties
of nanomaterials suggest their applications in almost all technological breakthroughs
ranging from catalysis, metal-organic framework, complex hydrides, etc. This study outlines the applications of nanomaterials in hydrogen production (considering both thermochemical, biological, and water splitting methods) and storage. Recent advances in
renewable hydrogen production methods are elucidated along with a comparison of
different nanomaterials used to enhance renewable hydrogen production. Additionally,
nanomaterials for solid-state hydrogen storage are reviewed. The characteristics of various nanomaterials for hydrogen storage are compared. Some nanomaterials discussed include carbon nanotubes, activated carbon, metal-doped carbon-based nanomaterials, metal-organic frameworks. Other materials such as complex hydrides and clathrates are outlined. Finally, future research perspectives related to the application of nanomaterials for hydrogen production and storage are discussed.
... Nanotechnology has the potential to be used in a variety of domains, including biosensors, biomedicine, and biomedical areas. In comparison to traditional materials, nanomaterials, such as nanofibers, NPs, nanosheets, and nanocomposites (NCs), are highly effective in catalysis and adsorption because they have a huge surface area and a small quantum size [53]. Since their small size and ability to permeate bacterial membranes make them useful in the breakdown of LCB, they are commonly utilized in this process. ...
... To immobilize enzymes, such as cellulases, cellobiose, and hemicellulases, which are required for the hydrolysis of LCB, nanomaterials are utilized [52]. With the use of NPs to immobilize enzymes, the LCB treatment has become viable and cost-effective [53]. ...
The development of low-cost bioenergy from the world's most abundant lignocellulosic biomass (LCB) is critical, as is tackling the issue of environmental contamination. In this context, nanomaterials have been used as catalysts for the production of sugars and derivative compounds that are easily absorbed by LCB cells. NPs derived from microorganisms can protect fermenting strains, hence increasing biofuel yield. Enzymes immobilised on nanoparticles or coupled with nanomaterials can be used to hydrolyze LCB in unique and ecologically friendly methods. Nanomaterials improve the efficiency, reusability, and stability of enzymes. Magnetic nanoparticles, in particular, have carved out a place for themselves through the process of downstreaming LCB effluents at a significant cost savings and increased efficiency. The role of nanotechnology and nanoparticles in the refining of LCB into a variety of commercially valuable products and precursors is highlighted in this review. This article successfully illustrates the relationship between nanotechnology concepts and the LCB refinery process.
... Moreover, by employing nanomaterials at pre-treatment step of lignocellulosic biomass may improve the removal of lignin thereby enhances the yield of sugar and also speed up the entire process (Wei et al., 2015). Further, nanomaterials can enhance the production, influence the thermal and pH stability of cellulase enzymes for efficient hydrolysis i.e. for cellulose to sugar conversion process (Srivastava et al., 2017;Ladole et al., 2017;Bilal et al., 2018). ...
... Nanomaterials play a significant role in catalyzing the dark fermentative biohydrogen reaction due to their small, large surface area and bio-compatibility (Mohanraj et al., 2014a,b;Taherdanak et al., 2015;Srivastava et al., 2017;Patel et al., 2018). Biohydrogen production via dark fermentation is carried out by versatile range of microorganisms with hydrogenase enzymes which degrades the organic substrate under the anaerobic condition but in the absence of light (Sambusiti et al., 2015). ...
... Physicochemical processes are reported expensive and produce toxic inhibitors (Prasad et al., 2020c). In converting biomass to sugars and further its transformation to ethanol, cellulase enzymes play a crucial role (Srivastava et al., 2017). However, enzyme production itself is the most cost-intensive step in the entire process and contributes B40% of the total cost (Srivastava et al., 2017;. ...
... In converting biomass to sugars and further its transformation to ethanol, cellulase enzymes play a crucial role (Srivastava et al., 2017). However, enzyme production itself is the most cost-intensive step in the entire process and contributes B40% of the total cost (Srivastava et al., 2017;. A significant challenge in making cellulosic ethanol economically viable is lowering enzymes' costs required to convert biomass to ethanol (Prasad et al., 2020c). ...
Biodiesel is considered an important and alternative source of renewable energy because of advantages such as biodegradability, decreased pollutant emission, lack of toxicity, and improved combustion efficiency. However, the existing technology for biodiesel production faces various challenges, such as expensive separation methods, impossibility of catalyst recovery, and high wastewater generation due to the use of homogeneous catalysts. To overcome these challenges, researchers are focusing on the development of more efficient processes for biodiesel production. The use of a low-cost catalyst is one of the main focuses in efficient biodiesel production. Calcium oxide (CaO) is a cheap, readily available, high-basicity, and solid heterogeneous catalyst used for the transesterification of different oil feedstocks to biodiesel. Development of CaO catalysts in nanoform (CaO nanocatalysts) has attracted a great deal of attention around the globe due to its enhanced catalytic activity and higher specific surface area. Thus, this chapter gives an overview of the synthesis of CaO-based nanocatalyst and its application in biodiesel production. It also illustrates the role of the functionalization of CaO nanocatalyst in increasing biodiesel efficiency and examines its preparation from waste material containing CaO. Moreover, it assesses the potentiality of CaO nanocatalyst as a solid heterogeneous catalyst for biodiesel production
... The first step in LB conversion is a pre-treatment which disrupts the complex structure of LB to release polymers. A number of pre-treatment methods, such as physical (e.g., steam explosion), chemical (e.g., acid, alkaline), physicochemical, biological, or combinations thereof [28], have been broadly studied and regularly used for isolating carbohydrates (cellulose and hemicellulose) from LB materials [29]. Still, the application of pre-treatment approaches on a commercial scale is a challenging task. ...
... Nickel cobaltite (NiCo 2 O 4 ) NPs were evaluated for their influence on cellulase production, and this study showed maximum cellulase production using NPs at a concentration of 1 mM [71]. In addition, cellulase immobilized on NiCo 2 O 4 NPs improved thermostability at 80 • C for 8 h compared to free enzymes, which can be one of the viable options for cellulase production from cheap sources such as LB materials [29]. Various enzymes immobilized using different types of NPs/nanomaterials are mentioned in Table 1. ...
The conversion of lignocellulosic biomass (LB) to sugar is an intricate process which is the costliest part of the biomass conversion process. Even though acid/enzyme catalysts are usually being used for LB hydrolysis, enzyme immobilization has been recognized as a potential strategy nowadays. The use of nanobiocatalysts increases hydrolytic efficiency and enzyme stability. Furthermore, biocatalyst/enzyme immobilization on magnetic nanoparticles enables easy recovery and reuse of enzymes. Hence, the exploitation of nanobiocatalysts for LB to biofuel conversion will aid in developing a lucrative and sustainable approach. With this perspective, the effects of nanobiocatalysts on LB to biofuel production were reviewed here. Several traits, such as switching the chemical processes using nanomaterials, enzyme immobilization on nanoparticles for higher reaction rates, recycling ability and toxicity effects on microbial cells, were highlighted in this review. Current developments and viability of nanobiocatalysts as a promising option for enhanced LB conversion into the biofuel process were also emphasized. Mostly, this would help in emerging eco-friendly, proficient, and cost-effective biofuel technology.
... Moreover, by employing nanomaterials at pre-treatment step of lignocellulosic biomass may improve the removal of lignin thereby enhances the yield of sugar and also speed up the entire process (Wei et al., 2015). Further, nanomaterials can enhance the production, influence the thermal and pH stability of cellulase enzymes for efficient hydrolysis i.e. for cellulose to sugar conversion process (Srivastava et al., 2017;Ladole et al., 2017;Bilal et al., 2018). ...
... Nanomaterials play a significant role in catalyzing the dark fermentative biohydrogen reaction due to their small, large surface area and bio-compatibility (Mohanraj et al, 2014;Taherdanak et al, 2015;Srivastava et al, 2017;Patel et al., 2018). Biohydrogen production via dark fermentation is carried out by versatile range of micro-organisms with hydrogenase en Fig 1. Role of nanomaterials in different modes of hydrogen production and their advantages to enhance the hydrogen production. ...
Recent advances on biohydrogen production using different types of cellulosic waste biomass with the implementation of nanomaterials are summarized. Inspired by exceptional physicochemical and catalytic properties of nanomaterials, the present review focuses on several approaches including impact of nanomaterials on cellulosic biohydrogen production, possible pretreatment technology, as well as improved enzyme & sugar production in order to enhance the biohydrogen yield. Particularly, impacts of nanomaterial are elaborated in detail on different pathways of biohydrogen production (e.g. dark fermentation, photo-fermentation and hybrid-fermentation) using variety of waste biomass. Additionally, emphases are made on the feasibility of nanomaterials for making the biohydrogen production process more economical and sustainable and hence to develop advanced techniques for biohydrogen production using waste biomass.
... Moreover, previous research suggests that the inclusion of magnetic nanoparticles may affect the pH and heat stability of cellulase enzymes, as well as shorten the lag phase of MOs, improving hydrolysis (Ladole et al., 2017). Moreover, the inclusion of magnetic NPs to the bioreactor (more specifically, Ni and Fe) can increase H 2 yield due to their capacity to bind to the active sites of the enzymes (Srivastava et al., 2017). The HG enzymes are used in DF to degrade organic substrates that are high in sugar in the absence of oxygen. ...
The urgent need to address greenhouse gas (GHG) emissions, particularly in relation to climate change, is driving the demand for new sustainable renewable fuels. This demand is promoting the expansion of de-carbonization efforts, which hold tremendous potential as a renewable energy source. One area of focus is the production of hydrogen (H2), which has long been a popular subject of discussion. Currently, large quantities of H2 are generated using conventional fossil fuels. However, the finite nature of these resources has compelled the global community to explore alternative, more environmentally friendly options like biomass. Generating H2 on a large scale from various biomasses presents a complex challenge. Researchers have identified thermochemical (TC) and biological (BL) processes as the primary methods for converting biomass into H2, although other techniques exist as well. Commercializing H2 as a fuel presents significant technological, financial, and environmental hurdles. Nevertheless, nanomaterials (NMs) have shown promise in overcoming some of the obstacles associated with H2 production. This review focuses on the use of NMs in TC and BL processes for H2 generation. Additionally, the paper provides a brief overview of the methods and financial considerations involved in enhancing biomass-based H2 production. Studies indicate that the production of bio-H2 is relatively expensive. Direct bio-photolysis costs range from $2.13 kg-1 to $7.24 kg-1, indirect bio-photolysis costs range from $1.42 kg-1 to $7.54 kg-1, fermentation costs range from $7.54 kg-1 to $7.61 kg-1, biomass pyrolysis costs range from $1.77 kg-1 to $2.05 kg-1, and gasification costs $1.42 kg-1. The paper also explores various challenges related to biomass conversion and utilization for H2 production, aiming to better understand the feasibility of a biomass-based H2 economy.
... The development of processes to convert lignocellulose into valuable chemicals, polymers, and energy is crucial for utilizing renewable sources. It is indeed the role of renewable sources to replace traditional fossil fuels and the chemicals derived from them, and lignocellulosic biomass is a valuable feedstock for these processes as it does not compete with food production [50][51][52][53][54][55][56]. ...
The sustainable management of lignocellulosic agricultural waste has gained significant attention due to its potential for the production of valuable products. This paper provides an extensive overview of the valorization strategies employed to convert lignocellulosic agricultural waste into economically and environmentally valuable products. The manuscript examines the conversion routes employed for the production of valuable products from lignocellulosic agricultural waste. These include the production of biofuels, such as bioethanol and biodiesel, via biochemical and thermochemical processes. Additionally, the synthesis of platform chemicals, such as furfural, levulinic acid, and xylose, is explored, which serve as building blocks for the manufacturing of polymers, resins, and other high-value chemicals. Moreover, this overview highlights the potential of lignocellulosic agricultural waste in generating bio-based materials, including bio-based composites, bio-based plastics, and bio-based adsorbents. The utilization of lignocellulosic waste as feedstock for the production of enzymes, organic acids, and bioactive compounds is also discussed. The challenges and opportunities associated with lignocellulosic agricultural waste valorization are addressed, encompassing technological, economic, and environmental aspects. Overall, this paper provides a comprehensive overview of the valorization potential of lignocellulosic agricultural waste, highlighting its significance in transitioning towards a sustainable and circular bioeconomy. The insights presented here aim to inspire further research and development in the field of lignocellulosic waste valorization, fostering innovative approaches and promoting the utilization of this abundant resource for the production of valuable products.
... Biofuels, compared to the other sources of renewable energy, constitute the most popular source as they can be transported and stored, and can be used for power generation on demand (Srivastava et al. 2017). The initial copious views on the production of biofuels were challenged due to the dawdled pace of development and the varied understanding of the impacts of this technology on sustainability. ...
As a result of global population growth and technological improvements, a huge amount of agricultural waste is produced worldwide. Despite being the most numerous and renewable source of biomass on earth, these wastes are mostly unexplored because of the absence of commercial technology. The most of these wastes are either burned or piled up in municipal landfills, which is harmful to the ecosystem and detrimental to the human and animal. In order to handle the enormous substantial quantities of agricultural waste that are produced sustainably, prevent environmental damage, and reflect a closed-loop economy that turns waste into a useful significant value-added product, viable ways for the exploitation of agricultural wastes have been needed. Here, we reviewed the various sources of agro-wastes and their potential as raw materials, owing to their lignocellulosic nature, easy availability, and economical bioprocessing, for the production of industrially important chemicals and products like (1) biofuels, (2) organic acids, (3) enzymes, (4) aroma compounds, etc., and their role as adsorbents for removal of contaminants for environmental applications. We also reviewed the different physico-chemical and biological routes for the agricultural biomass valorization towards the production of significant value-added products production within the scope of a circular economy. Thus, this chapter summarized the sources, processing, and application of agro-wastes as a veritable resource for the production of industrially important products for commercialization and environmental applications with their simultaneous management via biotechnological applications.KeywordsAgro-wastesManagementValorizationValue-added productsBiotechnology
... Nickel has the properties of efficient catalysis, surface reactiveness, and adsorption capability (Kobayashi et al., 2014), and thus catalyses biofuel production from lignocellulosic material. The stability of the cellulase enzyme at various temperatures is reduced with nickel-cobaltatite nanoparticles; at 1 mM concentration, nanoparticles illustrated enzyme balance at 80°C for eight hours, while enzyme stability was decreased with the absence of nanoparticles, indicating that nanoparticles can be a useful resource in the manufacturing of cellulase enzyme (Srivastava et al., 2017). ...
Book chapter from Taylor and Francis upcoming book on "Bionanotechnology towards Green Energy".
... A matrix pre-treatment is a crucial step enabling three major objectives: reducing cellulose crystallinity, removing lignin and hemicellulose parts, and increasing the porosity of the biomaterial [16,27]. Different procedures were developed, such as the use of physical pretreatments (mechanical comminution, irradiation-based, and microwave-assisted technologies), chemical agents (acid/ alkaline hydrolysis, organosolv processes, ozonolysis, ionic liquids), physicochemical pretreatments (pyrolysis, steam explosion, Ammonia Fiber Explosion, wet oxidation, liquid hot water, CO 2 supercritical/explosion), biocatalysis, emergent technologies such as nanocatalysis-assisted chemical or enzymatic depolymerizations, or a combination of multiple ones (Table 1), [26,27,[72][73][74][75][76][77][78][79][80][81][82][83][84][85]. Interestingly, the diversity of pretreatment systems has shown an advantage in being adapted to the variety of biomass characteristics, in a way that there is no absolutely single perfect strategy/ technology but the one or the combination which confers increasing sugar release and hydrolysis yields, escaping a loss in polysaccharides and the formation of fermentation inhibitors, and surely, the most cost-effective. ...
Lignocellulosic biomass is the most abundant renewable resource on earth, composed of agricultural waste, food processing byproducts, and other wastes which are thrown in nature and, unfortunately, non-valorized. It is a rich substrate recognized for its compositional and structural diversities, with a high interest in the production of green biofuels and chemical platform molecules, which are extremely sought after in the actual world energetic transition scenario. Although it represents a great opportunity for green industries, breaking down the plant cell wall (PCW) is technically not as affordable as thought before, and the development of green biorefineries depends on optimizing plant resources, process fluxes, prioritizing integrated strategies, and before all the above-mentioned, solving the plant recalcitrance issue. Converting biomass starts with the dissociation of its elements, which should be figured out in light of its compositional and structural complexities. Field and postharvest strategies like the genome-wide selection of biorefinery crops and the knowledge-based choice of appropriate harvesting periods were suggested to answer this challenge. Although these practices helped improve the processability of bioenergy crops, they did not reach promising levels and should be further improved by their combination with state-of-art engineering technologies. In this sense, genetic tailoring of the PCW biosynthetic genes and the application of integrated pretreatment strategies are interesting and in-depth explained here. In this comprehensive review, we discuss novel aspects related to the importance and richness of lignocellulose feedstock in the biorefinery concept, the recalcitrance of PCW and biomarkers as a roadmap approach to diagnosing it, and finally, state-of-art strategies to overcome it towards an enhanced delignification and saccharification. All with the same main perspective: making the most of lignocellulose in added-value biorefinery applications.
... The advantages of using NMs will undoubtedly add importance to the biofuels synthesis procedures, allowing it to become more sustainable by lowering expenses and having a positive ecological impact. 19 This chapter mainly focuses on the green synthesized BNMs, their different architectures, applications, and utilization as catalysts for bioenergy production. ...
A novel class of materials, “bimetallic nanoparticles” (BNPs), for catalysis have intensively investigated by integrating two different metals, which offer synergistic or novel features surpassing that of monometallic nanoparticles (MNPs). The green route of synthesizing BNPs is attracted immensely as a substitute to vanquish the drawbacks in conventional physical and chemical routes as the green route appears eco-friendly, inexpensive, and less time-consuming to synthesize. Among them, employing plants toward the synthesis of BNPs is emerging as advantageous compared to microbes. The application of BNPs as catalysts is a widespread, providential area considering their larger surface area, and thus utilizing the catalytic properties in altering the biomass into biofuel is a potential area to achieve maximum economic and environmental benefits. Hence, this chapter is a comprehensive contribution of the green synthesis of BNPs, the parameters that affect the synthesis of BNPs, characterization, practical applicability, and their application in bioenergy production.KeywordsGreen synthesisBimetallic nanoparticlesPhytochemicalsMicrobesCatalystBioenergy
... As reported by Seelert et al. (2015), the immobilization of Clostridium beijerinckii NCIMB8052 on magnetite nanoparticles reduced lag phase of microbial growth and then enhanced the biohydrogen production. Moreover, nanomaterials can be used for cellulase enzymes' immobilization to enhance hydrolysis of lignocellulosic waste in the pretreatment process thereby accelerating biohydrogen production of DF (Srivastava et al., 2017). For instance, Amin et al. (2018) showed that the immobilized laccase supported on modified Fe 3 O 4 @SiO 2 @Kit-6 magnetite nanoparticles enhanced the delignification of olive pomace biowaste and had high recyclability and stability. ...
Clean energy like hydrogen can be a promising strategy to solve problems of global warming. Photo-fermentation (PF) is an attractive technology for producing biohydrogen from various biowastes cost-effectively and environmentally friendly. However, challenges of low light conversion efficiency and small yields of biohydrogen production still limit its application. Thus, advanced strategies have been investigated to enhance photo-fermentative biohydrogen production. This review discusses advanced technologies that show positive outcomes in improving biohydrogen production by PF, including the following. Firstly, genetic engineering enhances light transfer efficiency, change the activity of enzymes, and improves the content of ATP, ammonium and antibiotic tolerance of photosynthetic bacteria. Secondly, immobilization technology is refined. Thirdly, nanotechnology makes great strides as a scientific technique and fourthly, integration of dark and photo-fermentation technology is possible. Some suggestions for further studies to achieve high levels of efficiency of photo-fermentative biohydrogen production are mentioned in this paper.
... Biological routes to the production of biohydrogen include photolysis (direct and indirect), electrolysis, and fermentation, including dark fermentation and photo-fermentation [4,12,13]. Diverse organic substrates and microorganisms are used for different biohydrogen production routes [6]. The natural biomass which are from lignocellulose have emerged as a potential substrate for the biological production of biohydrogen at a large scale [14]. ...
Renewable energy research has gained momentum due to the fast consumption and lack of sustainability in conventional fuels. As biohydrogen emits no greenhouse gases and can be generated from a variety of waste biomass or feedstocks, it has been referred to as the most effective and cleanest form of energy among all biofuels. In spite of the success of photobiological and dark fermentation methods in generating biohydrogen, they are known to produce lower yields, creating serious obstacles for commercial production. The role of nanoscience and technology in improving the biohydrogen production is achieved through the use of nanomaterials with specific physiochemical and structural properties. In this review, metals, metal oxides, metal alloys, and inorganic nanomaterials are explored in order to improve biohydrogen production. Initial studies have focused on nano materials evaluation in biomass conversion and addressing the current status of nanomaterials in biohydrogen production. The best bio-H2 yield is obtained in the presence of metal nanoparticles (NPs) such as Ag (2.4 mol H2/ mol glucose), Cu (1.74 mol H2/ mol glucose), Fe (3.10 mol H2/ mol malate), alloys of Al/Cu/Fe (4.2 mol H2/ sucrose) and Ni (2.54 mol H2/glucose). The review also addressed the mechanisms involved in changing feedstock into hydrogen through various microbial biorefineries. The life cycle analysis of various nanoparticles applications in biohydrogen production was discussed.
... As reported by Seelert et al. (2015), the immobilization of Clostridium beijerinckii NCIMB8052 on magnetite nanoparticles reduced lag phase of microbial growth and then enhanced the biohydrogen production. Moreover, nanomaterials can be used for cellulase enzymes' immobilization to enhance hydrolysis of lignocellulosic waste in the pretreatment process thereby accelerating biohydrogen production of DF (Srivastava et al., 2017). For instance, Amin et al. (2018) showed that the immobilized laccase supported on modified Fe 3 O 4 @SiO 2 @Kit-6 magnetite nanoparticles enhanced the delignification of olive pomace biowaste and had high recyclability and stability. ...
As a clean energy carrier, hydrogen is a promising alternative to fossil fuel so as the global growing energy demand can be met. Currently, producing hydrogen from biowastes through fermentation has attracted much attention due to its multiple advantages of biowastes management and valuable energy generation. Nevertheless, conventional dark fermentation (DF) processes are still hindered by the low biohydrogen yields and challenges of biohydrogen purification, which limit their commercialization. In recent years, researchers have focused on various advanced strategies for enhancing biohydrogen yields, such as screening of super hydrogen-producing bacteria, genetic engineering, cell immobilization, nanomaterials utilization, bioreactors modification, and combination of different processes. This paper critically reviews by discussing the above stated technologies employed in DF, respectively, to improve biohydrogen generation and stating challenges and future perspectives on biowaste-based biohydrogen production.
... The tool of nanotechnology in the biofuel industry participates in numerous applications like hydrogenation, transesterification, pyrolysis, anaerobic digestion and gasification (Zhang et al. 2013b). Some of the applications of nanotechnology in the bioindustry are shown in Fig. 12.1 (Srivastava et al. 2017). The choice of nanoparticle depends on the type of bioprocess and required yield of biofuels. ...
The high lipid-accumulating fungi have a unique physiology that makes them promising oil resource of fatty acid-based biofuels and oleochemicals with diverse applications as biodiesel, bio lubricants and in food, feed, cosmetic industries. Fungal lipids specifically intended for biodiesel synthesis constitute a bulk product (high volume, low value) and need to be produced at low cost, unlike the functional lipids such as n-3/n-6 polyunsaturated fatty acids. Several factors (including scalability and minimized costs) give solid-state fermentation a biotechnological advantage over submerged processes. Fungal lipids produced in solid-state cultures do hold a great potential for biodiesel production at an industrial scale. This chapter briefly overviews the agro-industrial residues (renewable carbon sources) and solid-state fermentation as two effective ways to increase the commercialization potential of single-cell oil-derived biodiesel production.KeywordsBiofuelsBiodieselFungal lipidsSolid-state fermentationAgro-industrial residues
... The tool of nanotechnology in the biofuel industry participates in numerous applications like hydrogenation, transesterification, pyrolysis, anaerobic digestion and gasification (Zhang et al. 2013b). Some of the applications of nanotechnology in the bioindustry are shown in Fig. 12.1 (Srivastava et al. 2017). The choice of nanoparticle depends on the type of bioprocess and required yield of biofuels. ...
Abundance and renewable nature of lignocellulosic biomass (LCB) make it a viable candidate for future biofuel production. However, LCB cannot be directly converted to biofuel due to its complex lignin structure leading to sustainable biomass process and value addition is a global challenge and requires pretreatment. Recent economic and social-political factors have stimulated the development of biofuels and bioenergy. Not only this but also the vital need of energy security as well as growing environmental concerns are the main drivers behind the growth in this sector. EU directive issued in 2009 specified that 20% of all energy in the EU-27 should come from renewable energy resources of which particular emphasis is on replacing 10% energy used in the transportation sector through the use of biofuels. However, this would not be possible if we are not able to use diverse range of available biomass for future biofuel production. This includes lignocellulosic biomass and this has further challenges before it can be transformed into the value product. This book chapter focuses on the current state of the art of lignocellulosic biomass (LCB) and its role in shaping future biofuels.KeywordsLignocellulosic biomassLigninBioenergy cropsDelignification
... The selection of required lignocellulosic biomass depends on the targeted end product. For the synthesis of most commodity biochemicals, biomass rich in polysaccharides and containing a low amount of lignin is preferred (Srivastava et al. 2017;Pattanaik et al. 2019). However, depolymerization of lignin also results in some aromatic monomers, which are of significance for biofuel generation and other applications (Gall et al. 2017). ...
The applications of green chemistry and industrial bioprocessing are becoming more popular to address concerns of pollution, climate change, global warming, circular bioeconomy, sustainable development goals and energy security. Both biological and thermochemical routes can play vital roles in transforming waste lignocellulosic biomass to high-value bioproducts. Lignocellulosic biomass contains essential building blocks that could be tapped to generate biofuels, biochemicals and biomaterials to replace petroleum-derived fuels and chemicals. Besides containing extractives and ash, lignocellulosic feedstocks are made up of cellulose, hemicellulose and lignin typically in the ranges of 35–55 wt%, 20–40 wt% and 10–25 wt%, respectively. Catalytic thermochemical approaches are effective for biomass conversion with a significant yield of various platform chemicals, such as furfural, 5-hydroxymethylfurfural, levulinic acid and other furan or non-furan-based chemicals. These chemicals play a crucial part in the synthesis of different fuel-based materials, which can successfully replace petroleum-based chemicals or fuels. Lignocellulosic biomass and their derived monomeric sugars can be catalytically converted into various platform chemicals using different homogeneous and heterogeneous catalysts. In this review paper, we have highlighted some promising catalysts such as mineral acids, mesoporous silica materials, zeolites, metal–organic frameworks, metal oxides and ionic liquids used in biorefining to generate biochemicals. We have also reviewed a few pieces of notable literature presenting the catalytic conversion of cellulose, hemicellulose, cellobiose, glucose, fructose and xylose into various high-value chemicals.
... The molecular examinations will help to know the basic mechanisms of the interaction of nanoparticles in the reaction process. All these challenges need to be overcome for use in industrial applications (Srivastava et al. 2017a(Srivastava et al. , 2017b. ...
Demand for alternative and renewable sources of energy is gaining worldwide attention due to fast depletion of fossil fuels and growing population. At present the global needs of energy are largely fulfilled by fossil fuels resulting into their depletion. However, the burning of fossil fuels contributes towards environmental issues like global warming and pollution. Biofuels like bioethanol and biodiesel are gaining popularity worldwide due to being renewable, eco-friendly and environmentally safe. Lignocellulosic biomass is available in plenty and can be transformed into bioethanol by steps including pretreatment, hydrolysis and fermentation. Various physical, chemical and biological pretreatments are used for making biomass accessible for enzymatic hydrolysis, however, these approaches are having some limitations which can be overcomes by alternative, cost-effective and environmental friendly technologies like nanotechnology. In enzymatic hydrolysis process, magnetic nanoparticles can be used for immobilization of enzymes, which makes the process more effective. The microorganisms can also be immobilized in various matrix including magnetic nanoparticles, which can enhance ethanol production. Moreover, magnetic nanomaterials can be recycled by using magnetic field and can be reused again. Nanocatalyst can also be employed in transesterification process for biodiesel production and for ameliorating the yields. Nanotechnology can play a key role in biofuel production by reducing processing cost and enhancing productivity. The present review discusses the role of nanotechnology and nanomaterials in pretreatment, enzymatic hydrolysis and fermentation steps during bioethanol production, and in transesterification for enhancing efficiency of the biodiesel production process.
... Often, the existence of strong magnetic dipole-dipole attractions between the nanoferrite particles leads to aggregation, posing a substantial limitation to their use as catalysts (Rana et al. 2015;Liu et al. 2016). Researchers have been developing and investigating different types of nanoferrites for their application as heterogeneous catalysts facilitating a high catalyst recovery rate (Srivastava et al. 2017;Gardy et al. 2018). ...
Fossil fuel depletion and pollution are calling for alternative, renewable energies such as biofuels. Actual challenges include the design of efficient processes and catalysts to convert various feedstocks into biofuels. Here, we review nanoferrites heterogeneous catalysts to produce biodiesel from soybean and canola oil. For that, transesterification is the main synthesis route and offers simplicity, cost-effectiveness, better process control, and high conversion yield. Catalysis with nanoferrites and composites allow to obtain yields higher than 95% conversion with less than 5.0 wt.% of catalyst loading at 80 °C in 1–2 h. More than 90% conversion yields can be achieved with a moderate alcohol/oil molar ratio, i.e., between 12:1 to 16:1. Catalyst recovery is easy due to the magnetic properties of nanoferrite, which can be effectively reused up to 4 times with less than 10% loss of catalytic efficiency.
... Bioethanol is produced from three biological materials based on the type of biomass. They are i) sugar and starchcontaining crops like wheat, beetroot, palm juice, sugar cane, fruits, and grains such as rice, corn, sweet sorghum, barley, wheat, etc. (Mohanty and Swain 2019;Naik et al. 2010;Srivastava et al. 2020); ii) cellulosic and lignocellulosic biomass primary derived from wood and wood waste (Limayem and Ricke 2012; Mood et al. 2013;Srivastava et al. 2017); iii) algae and microalgae (Filote et al. 2020;Pavithra et al. 2020); marine bacteria (Greetham et al. 2018; Ramachandra and Hebbale 2020), blue-green algae (Luo et al. 2010), etc. Wheat, corn, and sugar feedstocks are widely used to produce bioethanol (Mohanty and Swain 2019;. Corn, as a strategic bioresource of energy that is extensively used worldwide, has a significant percentage of bioethanol production . ...
Bioethanol produced from biological resources is considered as an alternative, renewable, and sustainable energy source in the context of the circular economy. Moreover, bioethanol is a biofuel that has similar energy content to gasoline, but emits less toxic pollutants compared to fossil fuels. Yet bioethanol must be anhydrous to be mixed with regular gasoline and is then utilized as a vehicle fuel. Different techniques have been developed to obtain anhydrous ethanol. Here, we compare techniques for dehydration of bioethanol, including adsorption and distillation. We present the performance of the process, product recovery, and energy consumption of the pressure swing adsorption method, which is effective and widely used.
... An array of modern renewable energy technologies is discussed throughout the literature. The most prominent technologies include photovoltaic solar power, concentrated solar power, solar thermal power for heating and cooling applications, onshore and offshore wind power, hydropower, marine power, geothermal power, biomass power and biofuels (Mathy et al. 2018;Shinnar and Citro 2008;Hache 2015;REN21 2019;Hussain et al. 2017;Østergaard et al. 2020;Shivakumar et al. 2019;Collura et al. 2006;Gude and Martinez-Guerra 2018;Akalın et al. 2017;Srivastava et al. 2017). ...
Climate change is defined as the shift in climate patterns mainly caused by greenhouse gas emissions from natural systems and human activities. So far, anthropogenic activities have caused about 1.0 °C of global warming above the pre-industrial level and this is likely to reach 1.5 °C between 2030 and 2052 if the current emission rates persist. In 2018, the world encountered 315 cases of natural disasters which are mainly related to the climate. Approximately 68.5 million people were affected, and economic losses amounted to $131.7 billion, of which storms, floods, wildfires and droughts accounted for approximately 93%. Economic losses attributed to wildfires in 2018 alone are almost equal to the collective losses from wildfires incurred over the past decade, which is quite alarming. Furthermore, food, water, health, ecosystem, human habitat and infrastructure have been identified as the most vulnerable sectors under climate attack. In 2015, the Paris agreement was introduced with the main objective of limiting global temperature increase to 2 °C by 2100 and pursuing efforts to limit the increase to 1.5 °C. This article reviews the main strategies for climate change abatement, namely conventional mitigation, negative emissions and radiative forcing geoengineering. Conventional mitigation technologies focus on reducing fossil-based CO2 emissions. Negative emissions technologies are aiming to capture and sequester atmospheric carbon to reduce carbon dioxide levels. Finally, geoengineering techniques of radiative forcing alter the earth’s radiative energy budget to stabilize or reduce global temperatures. It is evident that conventional mitigation efforts alone are not sufficient to meet the targets stipulated by the Paris agreement; therefore, the utilization of alternative routes appears inevitable. While various technologies presented may still be at an early stage of development, biogenic-based sequestration techniques are to a certain extent mature and can be deployed immediately.
... This is an emerging and auspicious technology for effective utilization of renewable feedstocks in an effort to reduce over-dependence on dwindling non-renewable energy sources (Srivastava et al. 2020;Peng et al. 2020). In recent times, conversion of lignocellulose biomass to produce liquid biofuels and other valuable chemicals has become the focus of research outputs (Stefanidis et al. 2016;Srivastava et al. 2017). This research area has gained global attention for being a cheap, non-edible, renewable and environmentally friendly sources with the aid of different processing approaches (Chauhan et al. 2009). ...
The rise of consumption of traditional fossil fuels has caused emissions of greenhouse gas and deterioration of air quality. Biomass is a promising substitute for fossil fuels because biomass provides biofuels and chemicals by thermochemical conversion such as pyrolysis. In particular, fast pyrolysis of biomass cellulose into chemicals and biofuels has recently drawn attention. Issues of commercialization of fast pyrolysis products include low heating value, low stability, and high oxygen content and acidity. Consequently, new catalysts for enhanced cellulose conversion are sought for. Here, we review the production of biofuel and renewable chemicals from cellulose pyrolysis using acidic and basic catalysts. Acidic catalysts are more suitable to produce biofuels containing about 50% aromatic hydrocarbons, compared to basic catalysts which give biofuels containing 15% aromatic hydrocarbons. Basic catalysts are preferred to produce renewables chemicals, particularly ketone compounds. We explain the mechanism of cellulose pyrolysis with acidic and basic catalysts. The strong acid sites on the catalyst facilitate high selectivity for aromatic compounds in the pyrolysis oil, whereas basic active sites induce double-bond migration, increase carbon-coupling reactions, and ketone production.
... Besides, many environmental problems associated with fossil fuels combustion have proposed pressing needs to develop renewable and environmental-friendly energy sources which are derived from non-fossil sources in ways that can be replenished (Bouabidi et al. 2018;Fu et al. 2018;Guo et al. 2019). Among various renewable energy types, like solar, wind, hydro, geothermal and biofuels (Aravind et al. 2020), the biofuels produced via microbial energy conversion are considered as one of the most promising energy types due to its high energy conversion efficiency, mild operating conditions and environmental remediation ability (Srivastava et al. 2017). ...
Technologies for conversion of microbial energy have recently attracted interest to transform waste into bioenergy, thus addressing simultaneously environmental and energy issues. Nonetheless, actual microbial systems for energy conversion have limitations such as low rate of mass transfer, uneven energy distribution and strong inhibition of products and by-products. These technical bottlenecks can be alleviated by using membranes, which regulate the transfer of mass, heat and energy. Here we review applications of membranes for microbial energy conversion. We discuss mechanisms, functions and development of membranes for feedstock preparation, bioenergy production and bioproduct post-treatment. We present key membrane factors that control the efficiency of microbial fuel cells. We address membrane biofouling problems and anti-fouling approaches, in order to improve future commercialization.
In recent years, an enormous amount of research effort has been devoted to the study of immobilization methods and carrier materials for enhancement of the dark fermentation process. It is shown that immobilization has a complex multifactorial effect on the process of dark fermentation and opens up new technological possibilities, such as better acclimatization of hydrogen producers, a decrease in the lag phase, and an increase in biomass density, which provides greater resistance to inhibitory substances and shock loads. In addition, the use of carriers allows a wider variation of the main technological parameters, such as hydraulic retention time (HRT) and organic loading rate (OLR), and more flexible control. The chapter highlights the main immobilization methods, and their advantages and disadvantages. Parameters affecting attached growth systems, such as type of material, biofilm thickness, pH, substrate characteristics, are discussed. Particular attention is paid to materials that have a complex stimulating effect, such as conductive materials, as well as materials containing trace elements and nanoparticles that affect cell growth, metabolism, and enzyme activation. A comparative analysis of various types of biofilm reactors, their design, and operating modes is given. In conclusion, an assessment is given of the prospects for using immobilization to develop efficient, economical, and stable technologies for producing dark fermentative biohydrogen.
Different generational approaches towards producing biofuels have been established over the years as there is an urgent need to find an alternative to fossil fuels. Most of the developing nations and the countries prioritizing agriculture have achieved commercial production and consumption of biofuels instead of non-renewable resources and therefore significantly avoid serious environmental impacts. But this is not applicable globally, the cheap cost of fossil fuels has been a barrier in the industrial part of biofuel production and its wide-scale application. In order to overcome this barrier, bioprospecting of potential bioenergy sources and research on producing better, convenient, and cost-effective biofuels are the goals set by researchers as we move towards an eco-friendly world. This chapter will provide some insights into the commercial production process including the upstream and downstream parameters involved in the first three generations of biofuels. These biofuels comprise of liquid-based fuels, i.e., bioethanol, biobutanol, biodiesel, and gaseous-based fuels which includes biomethane and biohydrogen. Second-generation biofuel is the most sustainable generation of all currently, as cellulose is widely available. Selection and pretreatment are the key processes in second-generation biofuel as they have an impact on the cost of production. Third-generation biofuel has a major advantage as it can be coupled to treat wastewater and produce biofuel as well. Studies have shown that microalgae growing in wastewater generate more biomass and it is economical.KeywordsEnergy cropsLignocellulosic biomassMicroalgaeLiquid-based biofuelsGaseous-based biofuelsBioreactors
In this study, biodelignification and enzymatic hydrolysis of elephant grass were performed by recombinant and native strain of Trichoderma reesei, respectively. Initially, rT. reesei displaying Lip8H and MnP1 gene was used for biodelignification with NiO nanoparticles. Saccharification was performed by combining hydrolytic enzyme produced with NiO particles. Elephant grass hydrolysate was used for bioethanol production using Kluyveromyces marxianus. Maximum lignolytic enzyme production was obtained with 15 µg/L of NiO nanoparticles and initial pH of 5 at 32°C. Subsequently, about 54% of lignin degradation was achieved after 192 h. Hydrolytic enzymes showed elevated enzyme activity and resulted in 84.52 ± 3.5 g/L of total reducing sugar at 15 µg/mL NiO NPs. About 14.65 ± 1.75 g/L of ethanol was produced using K. marxianus after 24 h. Thus, dual strategy employed for conversion of elephant grass biomass into fermentable sugar and subsequent biofuel production could become potential platform for commercialization.
Nanotechnology is being studied in several sectors, including medical, engineering, the environment, electronics, military, etc. Many studies are being conducted to advance knowledge in terms of size, capacity, and cost. The nanomaterials are synthesized and characterized by different methods, and it is used for the different applications. The review presented here is on the role of nanomaterials in biogas and biohydrogen production. The addition of NP increased the yield of biogas and biohydrogen, the influence of size and shape of metal oxide NP and metallic NP on biogas and biohydrogen production.
Bioenergy that comprises biodiesel, biogasoline, bioethanol, biobutanol, hydrogen, etc. is one of the emerging renewable energies capable of tackling climate change and promising long-term durability. There is an upsurge in the interest in scientific field to enhance the output of the biofuel industry that seeks intervention of nanotechnology to overcome the limitations. Nanotechnology is a tremendously growing field merging and effecting a wide range of technological, biological and pharmacological applications but still its usage for bioenergy production from biomass is at a budding stage. Employing nanomaterials in the production of bioenergy increases efficiency and reduces process cost. Nanosized materials enhance the reaction kinetics of catalysis process by providing more catalytic sites and considerably large surface area for interaction. Wide range of nanomaterials are synthesized with distinct properties and surface features to accommodate the demand of cost-effective and process-efficient biofuel industry. The promising role of nanotechnology in the biofuel industry can be realized from studies like increase in biodiesel production rate by nano-catalyst-based microbial enzymes, use of nanomaterial additives to enhance the biogas yield and improvement of anaerobic digestion process using magnetic nanoparticles. This chapter focuses on the role of bionanomaterials in biofuel production and highlights the impact of nanotechnology-based bioenergy generation through comprehensive literature study.KeywordsBioenergy productionNanomaterialsBiodieselBiogasMicrobial fuel cellsCarbon-based materialsNanostructured materials
Nanotechnology is one of the most promising opportunities for technological development in the 21st century, and with the global increase in nanotechnology, recycling of nanomaterials (NMs) can be a vital step toward achieving sustainability in nanotechnology. This chapter provides a brief introduction of NMs and their properties, such as classification, structure, and physical and chemical properties. Additionally, emphasis is put on the recycling of NMs, fundamentals, and environmental and economic aspects. Finally, the chapter focuses on several approaches, including mechanical properties of different recycled NMs as well as recycling of NMs and its methods. The results confirmed that the application of recycled nanofillers can be an efficient technique for the improvement of mechanical properties of recycled polymers, composites, and blends.
Nanotechnology-based industries are projected to grow from a multimillion-dollar industry to a few billions of dollars in the next few decades. The rate of nanotechnology production is very high as per global market scenario. With increasing penetration of nanomaterials (NMs) in our daily lives through consumer products, nanowastes and nanobyproducts are bound to circulate in the environment and our surroundings. These include the byproducts generated from nanotechnology processed products. This chapter discusses the various NMs or nanostructured byproducts and the nanowaste that is generated by various industries. Nanoparticles that are released into the atmosphere are contemplate as different categories of waste when compared to their bulk counterpart. NMs recycling offers many benefits in both environmental and economic terms. NMs can be recycled from both new and pure products (from nanomanufacturing) and used products (nanowaste from nanointegrated products). This chapter discusses various processes of nanobyproduct generation and utilization that will be part of the evolution toward green technology.
The applications of ILs in the preparation and recovery of several inorganic and hybrid
materials are promising. ILs can be generally applied for several materials, such as
metals, nonmetal elements, silicas, metal oxides, chalcogenides, and porous materials.
ILs offer high recyclability and can be cost-effective after optimization, making them
attractive and receiving a growing number of scientists. ILs can be considered green
solvents. The methods that implement ILs are sustainable and could be effective in
comparison to conventional methods. Future research will explore the synthesis of
cheap ILs, making use of cost-effective methods.
In this work, lignin-based carbon nanofibers (LCNFs) were for the first time served as substrate for in-situ electrodeposition of polyaniline (PANI) and tested as pseudocapacitor. Two LCNFs with different lignin ratios were designed to distinguish their morphology and structural properties. Next, PANI deposition mechanisms on both LCNFs were investigated and the electrochemical performance of the resulting LCNF/PANIs were evaluated. It was found although LCNF2 was composed of less uniform nanofibers due to more presence of lignin in precursor dope, it had higher tensile strength/modulus than LCNF1 (strength: 34.3MPa to 24.2 Mpa; Modulus: 2.4 GPa to 1.45GPa) and was more cost-effective. Particularly, the beaded fibers on LCNF2 contributes to the deposition of PANI with higher specific mass capacitance (612.8 F g-1 to 547.0 F g-1). Upon assembling into solid-state supercapacitors, the Cm of LCNF2/PANI device was determined to be 229 F g-1 and the maximum energy density is 11.13Wh kg-1 at a power density of 0.08 kW kg-1. This work showed LCNF produced from renewable and low-cost lignin can be directly used as substrate for PANI deposition. Moreover, the composition in spinning dope played an important role in determining the performances of resulting pseudocapacitors.
The potential of nanomaterials that are synthesized from nature is considered. These types of material are applicable in many industries, such as environment, wastewater treatment, agriculture, food and food processing, energy, biomedical. In this chapter, we have focused on the types of industry that can use green nanotechnology.
Since the 21st century, the demand for energy has been increasing at an alarming rate due to the limited available renewable fuel resources and the rapid advanced technological development. This has driven countries to focus on the discovery of a new alternative fuel, biofuel, with imperative inherent benefits. Commercial biofuel production exhibits various technical barriers as well as expensive production cost. The exploitation of nanotechnology offers a new potential approach to the generation of biofuel in an ecofriendly manner. Despite its promising advantages, the negative impacts associated with nanomaterials utilized in biofuel production systems have numerous adverse impacts on the environment, living organisms, and the economy. This chapter focuses on the strategic role of nanoparticles in biofuel production systems and the design of various nanocatalysts used in the generation of biofuel. The chapter also advocates the challenges associated with the application of nanotechnology in biofuel production systems. Finally, the chapter summarizes the opportunities and future aspects in the way forward with the utilization of nanoparticles in the generation of biofuel.
Fruit wastes can be imperative to elevate economical biomass to biofuels production process at pilot scale. Because of the renewable features, huge availability, having low lignin content organic nature and low cost; these wastes can be of much interest for cellulase enzyme production. This review provides recent advances on the fungal cellulase production using fruit wastes as a potential substrate. Also, the availability of fruit wastes, generation and processing data and their potential applications for cellulase enzyme production have been discussed. Several aspects, including cellulase and its function, solid-state fermentation, process parameters, microbial source, and the application of enzyme in biofuels industries have also been discussed. Further, emphasis has been made on various bottlenecks and feasible approaches such as use of nanomaterials, co-culture, molecular techniques, genetic engineering, and cost economy analysis to develop a low-cost based comprehensive technology for viable production of cellulase and its application in biofuels production technology.
Microbial biotechnology mainly aims to use microorganisms and their biological processes to improve life, through obtaining a direct product for human use or an indirect useful service such as bioremediation and environmental cleanup. The field of microbial nanotechnology as a branch of microbial biotechnology has become more active and attractive for industry, agriculture, health and environment. The environment recently faces serious pollution due to the negative impact of different human activities, which make a real and unconventional prompt efforts to keep the sustainability of the environment. Applications of nanotechnology for environmental applications have many advantages due to the unique properties of nano-sized materials. Hereafter, the concept of environmental nanobiotechnology and sustainable environment will be discussed in regards of microbial-mediated nanoparticles. Also, different and recent environmental applications of nanoparticles that are synthesized via microbial activity will be included. Consequently, this chapter has much information about bio-manufacturing of nanomaterials using various microorganisms as well as applications of biosynthesized nanomaterials for protection of environment. The incorporation of nanotechnology into microbial and environmental biotechnology is a relatively new trend that has shown auspicious results in many areas and applications including environmental issues. In this chapter, the development of the microbial synthesis of nanoparticles and its role in environmental sustainability has been discussed. Several topics were addressed such as microbial synthesis of NPs and its advantages, application of microbial-mediated NPs in bioremediation, agriculture applications, sustainable energy, nano-biosensors, nano-pesticides and nano-fertilizers.
Green synthesis is one of the most valuable and emerging methods for the synthesis of nanoparticles (NPs) nowadays, presenting imperative biological benefits, reduced process time, cost-effectiveness, and environmental benefits, as an alternative to physical and chemical processes. Silver, a noble metal, possess unique properties and potential applications in medicine, requiring the search for novel and suitable tools for its production due to the growing demand. The exploration of plants diversity can be used towards rapid and single-step preparatory methods for various NPs, maintaining the green principle over conventional ones, an important aspect for medical applications. Plants contain bio-organics components, which usually play multiple roles as reducing, capping as well as stabilizing agents for metal compounds into silver nanoparticles (AgNPs). The stability of these NPs is governed by certain parameters, which influence stability and bioavailability. In this perspective, this review aims to provide a comprehensive view to understand the possible induced mechanism, current scenario and future prospects for the bio-inspired synthesis of AgNPs.
The fossil fuel industry faces issues of atmospheric pollution by sulphur and nitrogen compounds, and emerging competition from electricity, solar, wind and hydrogen sectors. As a consequence, green solvents such as ionic liquids and deep eutectic solvents have been recently developed for alternative fuel purification. Deep eutectic solvents are usually more efficient and better biodegradable, whereas ionic liquids display qualities for safety and optimization. Some ionic liquids and deep eutectic solvents allow a 100% removal efficiency of sulphur and nitrogen compounds from petroleum. Biodiesel yields up to 98.1% are reached using green solvents. Pretreatment of biomass with green solvents has been found to increase by 50% the bioethanol yield.
Energy and waste disposal issues are calling for advanced recycling methods such as conversion of organic waste into biohydrogen and biomethane. Here we review factors that influence yields, such as pH, temperature, substrate composition, biocatalyst, nutrient content, volatile fatty acids concentration, organic loading rate, hydraulic retention time and C/N ratio. The optimum pH is 5.5–6 for hydrogen production, and 6.8–7.2 for methane production. Hydrogen yield improved highly after reducing the retention time from 72 to 20 h. The highest methane productivity was achieved with C/N ratio of 16–27. We also discuss methods to improve efficiency such as co-digestion, pre-treatment, application of additives and optimal digester design. Co-digestion synergizes the effects on microbial communities, balances the nutrients, reduces the inhibitory effects and improves the economic viability. Co-digestion has enhanced the productivity by 25–400% compared to mono-digestion. Acid pre-treatment is the best method for lignocellulose hydrolysis, followed by enzyme pre-treatment. Microwave pre-treatment enhances the biomethane production 4–7 times. The batch mode improves the substrate degradation efficiency and hydrogen production by 25% compared to the continuous mode. The addition of trace metals alters the hydrogenase activity during anaerobic fermentation. Reaction kinetics and metabolomics, bioaugmentation, digestate recirculation, frequent feeding and development of bioreactor systems for two-stage anaerobic digestion are also presented.
Biotransformation of organic wastes into value-added products is gaining interest owing to waste management issues, exhaustion of fossil fuels and the demand for biodegradable plastics. Lactic acid is widely used for polymers, foods, beverages, medicines, cosmetics and clothing. However, the major obstacle in large-scale fermentation of lactic acid is achieving enhanced yield, productivity and optical purity with cheap resources. Therefore, we review methods and recovery techniques for production of microbial lactic acid using cheap fermentative substrates. New strategies allow to alleviate limitations associated with substrate inhibition, product inhibition, undesirable by-products, sensitivity to toxic compounds, inefficient utilization of mixed sugars and overuse of neutralizing agents. Efficient utilization of mixed sugars can be achieved with simultaneous saccharification and fermentation using mixed cultures, isolating carbon catabolic repression-negative strains and altering the metabolic pathway. Lactic acid productivity can be improved by co-culture, maintaining high cell density and periodically removing end-products accumulated in the fermentation medium. Inhibition by toxic compounds can be eliminated by using engineered feedstock which releases less inhibitors, by using inhibitor-tolerant microbes and by development of genetically engineered strains. Fed-batch fermentation was found to be better than other operation modes due to less substrate inhibition.
Rise in human population and gradual decline in fossil fuels are increasing the demand for fuels and causing an upsurge in fuel prices and global warming. Concomitantly, consumers have raised their health awareness by taking various supplements, e.g. omega-3 fatty acids, thus calling for advanced nutraceuticals. Both issues are addressed by recent research on microalgae, which can be easily cultivated to produce lipidic biofuels and active drugs. Here, we reviewed the types and biosynthesis of microalgal lipids. We discuss genetic engineering and manipulation of cultivation conditions for enhancing lipid production. We present techniques for lipid extraction, with focus on green techniques. We also discuss the technical and economic challenges in manufacturing microalgae-based biofuels and other bioproducts at the industrial scale. Last, the market potentials and further research directions for future commercialization of microalgae lipids are discussed.
The rising activities of global agriculture and forestry industries are producing huge amounts of lignocellulosic waste, which needs to be well recycled. The management of this waste involves environmental, social, economic and political challenges. Lignocellulosics have been commonly used for construction materials and energy production, thus achieving positive social and environmental impacts. Lignocellulosics represent also a promising feedstock for the production of carriers for enzyme and cell immobilization. Immobilization is a technique in which the biocatalyst is fixed on the surface of an insoluble matrix, allowing to recover the biocatalyst after reaction. The support must have specific characteristics such as inertness, physical strength, stability, renewability and low cost. These characteristics are fulfilled by lignocellulosic materials. Here, we review the applications of lignocellulosic biomass for fermentation, remediation of contaminated water and soil, synthesis of solvents and fine chemicals, juices clarification, and production of fructooligosaccharides. Recycling lignocellulosic waste for the immobilization of enzymes and cells allow to reduce environmental issues. Processes using immobilized cells and enzymes give high rates of solvent productivity, of 1.44–1.67 g/Lh, activity retention, around 90%, and stability, above five cycles of reaction.
The world is paying attention on exploring and establishing alternative modes of energy production instead of utilizing fossil fuels, because of the truth that conventional fuels are being squandered and the liberated chemicals of these fuels have become detrimental to the environment. In this context, production of biofuels can solve the issue, and nanotechnology can play a significant role for biofuel industry. Iron oxide nanomaterials are helpful and have great potential for enhanced production of biofuels. Many investigations have been conducted on the synthesis and use of iron oxide nanomaterials. There are different methods to synthesize iron oxide nanomaterials, and they are efficiently used in biofuel synthesis.
Free enzymes do not possess properties of recovery and reusability, and also they are not stable at wide pH and temperature range. Therefore, new ways which can enhance enzyme stability and reusability should be developed, and hence, the immobilization technique is one such approach. These immobilization techniques offer such materials which have the ability to be active in the much wide range of pH and temperature, and also they are more stable than the free enzymes. Immobilization is carried out on the nanosized material either by adsorption, covalent coupling, entrapment, encapsulation or cross-linking. These nanomaterial-immobilized enzymes show several advances over the free enzymes because of large surface area-to-volume ratio, lower mass transfer resistance and high mobility. Several nanomaterials are used for immobilizing the enzymes; however, their recovery from the reaction mixture is very poor. Therefore, the magnetic nanomaterials are more attractively used in immobilization because the enzyme immobilized through magnetic nanomaterial has the tendency to be easily separated out from the reaction mixture. These nanomaterial-immobilized enzymes show wide range of applications in biotechnology, bioanalysis, biomedicine, pathology and biosensors.
Lignocellulosic biomass is a sustainable alternative to current biofuels. The conversion of biomass-based sugars into biofuels, which emerged in 1970, is gaining more attention due to fossil fuel issues. Biohydrogen and bioethanol from cellulosic wastes is a sustainable and solves economic issues. This chapter reviews the use of nanoparticles for the bioconversion of biomass into biofuels.
Cellulases are the enzymes which are responsible for the hydrolysis of cellulosic biomass. In this study thermal and pH stability of crude cellulase has been investigated in the presence of zinc oxide (ZnO) nanoparticles. We synthesized ZnO nanoparticle by sol-gel method and characterized through various techniques including, X-ray Diffraction, ultraviolet-visible spectroscope, field emission scanning electron microscope and high resolution scanning electron microscope. The crude thermostable cellulase has been obtained from the Aspergillus fumigatus AA001 and treated with ZnO nanoparticle which shows thermal stability at 65°C up to 10 h whereas it showed pH stability in the alkaline pH range and retained its 53% of relative activity at pH 10.5. These findings may be promising in the area of biofuels production.
The extensive use of nanoparticles under different industrial processes and their release into the environment are of major concerns in the present global scenario. In the present study, the effects of activated carbon-based TiO2 (AC-TiO2) nano-composite on the seed germination of Solanum lycopersicum (tomato) and Vigna radiata (mungbean) were investigated. The size of nanoparticles used in the study ranged from 30 to 50 nm, and their concentrations were from 0 to 500 mg L−1. The composites were synthesized by sol–gel method and further characterized by scanning electron microscopy, Energy-dispersive X-rays spectroscopy (EDX), Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction to investigate all the surface structural and chemical properties of AC-TiO2 nano-composite. The results showed that increase in nano-composite concentration improves the germination rate and reduces germination time up to a certain concentration. Therefore, employing AC-TiO2 nano-composites in suitable concentration may promote the seed germination and also reduce the germination time in Solanum lycopersicum and Vigna radiata. Further, it may help to understand the interface of TiO2 nanoparticles with the environment and agriculture before its application to the field.
Cellulases have wide applications in the biofuel industry. The three main components, namely endoglucanase, exoglucanase, and β-glucosidase effectively convert lignocellulosic biomass into fermentable sugar. The commercial production of cellulase is done using the submerged fermentation; however, it is costly and less economic for biofuels production. Moreover, microbial cellulase production process suffers from various bottlenecks. Because of the low cost, production of cellulase using solid-state fermentation by fungi is preferable. Therefore, the present review provides an overview on cellulase, main aspects of cellulase production and present scenario of cellulase production in the biofuels industry.
The review deals with fuel ethanol production from plant-based lignocellulosic biomass as raw materials. In this article, the technologies for producing fuel ethanol with the main research prospects for improving them are discussed. The complexity in the biomass processing is identified by the analysis of various stages involved in the conversion of lignocellulosic biomass into fermentable sugars. Further, the fermentation processes with its important features are explained based on biomass conversion. Comparative index for different types of biomass for fuel ethanol production is listed. Finally, some concluding remarks on current research regarding the pre-treatment along with biological conversion of biomass into ethanol are presented.
In the present study, effect of nickel-cobaltite (NiCo2O4) nanoparticles (NPs) was investigated on production and thermostability of the cellulase enzyme system using newly isolated thermotolerant Aspergillus fumigatus NS belonging to the class Euratiomycetes. The NiCo2O4 NPs were synthesized via hydrothermal method assisted by post-annealing treatment and characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. In the absence of NPs in the growth medium, filter paper cellulase (FP) activity of 18 IU/gds was achieved after 96 h, whereas 40 % higher FP activity in 72 h was observed with the addition of 1 mM concentration of NPs in the growth medium. Maximum production of endoglucanase (211 IU/gds), β-glucosidase (301 IU/gds), and xylanase (803 IU/gds) was achieved after 72 h without NPs (control), while in the presence of 1 mM concentration of NPs, endoglucanase, β-glucosidase, and xylanase activity increased by about 49, 53, and 19.8 %, respectively, after 48 h of incubation, against control, indicating a substantial increase in cellulase productivity with the addition of NiCo2O4 NPs in the growth medium. Crude enzyme was thermally stable for 7 h at 80 °C in presence of NPs, as against 4 h at the same temperature for control samples. Significant increase in the activity and improved thermal stability of cellulases in the presence of the NiCo2O4 NPs holds potential for use of NiCo2O4 NPs during enzyme production as well as hydrolysis. From the standpoint of biofuel production, these results hold enormous significance.
Research and development (R&D) in the field of biofuels in general and biodiesel in particular are not new en-deavours. However, they gained momentum in the last couple of decades due to the increasing economic concerns and environmental awareness about the use of petroleum-derived fossil fuels. In this review article, recent patents and research and studies dealing with the production of biodiesel from bioresources will be investigated and discussed. The main objective is to present the latest research undertakings, findings and innovations in the scientific and industrial communities on biodiesel production for various bioresources and wastes.
Hydrogen is gaining a great deal of attention as an energy carrier as well as an alternative fuel. However, in order to fully
implement the so called ‘hydrogen economy’ significant technical challenges need to be overcome in the fields of production
and storage of hydrogen and its point of use especially in fuel cells for the automotive industry. The purpose of this review
is to present and discuss recent advances in the use of nanomaterials for solar hydrogen production and on-board solid state
storage of hydrogen. The role of nanotechnology in enhancing the efficiency of fuel cells and reducing their cost is also
discussed.
Anode properties are critical for the performance of microbial electrolysis cells (MECs). In the present study, Fe nanoparticle-modified graphite disks were used as anodes to investigate the effects of nanoparticles on the performance of Shewanella oneidensis MR-1 in MECs. Results demonstrated that the average current densities produced with Fe nanoparticle-decorated anodes up to 5.89-fold higher than plain graphite anodes. Whole genome microarray analysis of the gene expression showed that genes encoding biofilm formation were significantly up-regulated as a response to nanoparticle-decorated anodes. Increased expression of genes related to nanowires, flavins, and c-type cytochromes indicates that enhanced mechanisms of electron transfer to the anode may also have contributed to the observed increases in current density. The majority of the remaining differentially expressed genes associated with electron transport and anaerobic metabolism demonstrate a systemic response to increased power loads.
The current global energy situation has demonstrated an urgent need for the development of alternative fuel sources to the continually diminishing fossil fuel reserves. Much research to address this issue focuses on the development of financially viable technologies for the production of biofuels. The current market for biofuels, defined as fuel products obtained from organic substrates, is dominated by bioethanol, biodiesel, biobutanol and biogas, relying on the use of substrates such as sugars, starch and oil crops, agricultural and animal wastes, and lignocellulosic biomass. This conversion from biomass to biofuel through microbial catalysis has gained much momentum as biotechnology has evolved to its current status. Extremophiles are a robust group of organisms producing stable enzymes, which are often capable of tolerating changes in environmental conditions such as pH and temperature. The potential application of such organisms and their enzymes in biotechnology is enormous, and a particular application is in biofuel production. In this review an overview of the different biofuels is given, covering those already produced commercially as well as those under development. The past and present trends in biofuel production are discussed, and future prospects for the industry are highlighted. The focus is on the current and future application of extremophilic organisms and enzymes in technologies to develop and improve the biotechnological production of biofuels.
Biodiesel is an alternative energy source and could be a substitute for petroleum-based diesel fuel. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. Most of the sources, methods and apparatus to produce biodiesel are reviewed here. Some of the patents propose the use of oils and fats of animal or vegetal origin and other kind of sources. Many others focus on the methods for the production or oxidation stability of the biofuel in order to make its production economically competitive. Several apparatus comprising reactors and refineries are also presented. This review article summarizes recent and important patents relating to the production of biodiesel to make its production a viable alternative.
The use of biomass to provide energy has been fundamental to the development of civilisation. In recent times pressures on the global environment have led to calls for an increased use of renewable energy sources, in lieu of fossil fuels. Biomass is one potential source of renewable energy and the conversion of plant material into a suitable form of energy, usually electricity or as a fuel for an internal combustion engine, can be achieved using a number of different routes, each with specific pros and cons. A brief review of the main conversion processes is presented, with specific regard to the production of a fuel suitable for spark ignition gas engines.
Specific cellulose hydrolysis rates (g of cellulose/g of cellulase per h) were shown to be substantially higher (2.7- to 4.7-fold) for growing cultures of Clostridium thermocellum as compared with purified cellulase preparations from this organism in controlled experiments involving both batch and continuous cultures. This “enzyme–microbe synergy” requires the presence of metabolically active cellulolytic microbes, is not explained by removal of hydrolysis products from the bulk fermentation broth, and appears due to surface phenomena involving adherent cellulolytic microorganisms. Results support the desirability of biotechnological processes featuring microbial conversion of cellulosic biomass to ethanol (or other products) in the absence of added saccharolytic enzymes.
• cellulase
• cellulosome
• consolidated bioprocessing
• ethanol
Thermostable enzymes offer potential benefits in the hydrolysis of lignocellulosic substrates; higher
specific activity decreasing the amount of enzymes, enhanced stability allowing improved hydrolysis performance
and increased flexibility with respect to process configurations, all leading to improvement of the overall
economy of the process. New thermostable cellulase mixtures were composed of cloned fungal enzymes for
hydrolysis experiments. Three thermostable cellulases, identified as the most promising enzymes in their
categories (cellobiohydrolase, endoglucanase and β-glucosidase), were cloned and produced in Trichoderma reesei and mixed to compose a novel mixture of thermostable cellulases.
Thermostable xylanase was added to enzyme preparations used on substrates containing residual hemicellulose.
The new optimised thermostable enzyme mixtures were evaluated in high temperature hydrolysis experiments
on technical steam pretreated raw materials: spruce and corn stover. The hydrolysis temperature could
be increased by about 10–15 °C, as compared with present commercial Trichoderma
enzymes. The same degree of hydrolysis, about 90% of theoretical, measured as individual sugars, could
be obtained with the thermostable enzymes at 60 °C as with the commercial enzymes at 45 °C.
Clearly more efficient hydrolysis per assayed FPU unit or per amount of cellobiohydrolase I protein
used was obtained. The maximum FPU activity of the novel enzyme mixture was about 25% higher at the optimum
temperature at 65 °C, as compared with the highest activity of the commercial reference enzyme
at 60 °C. The results provide a promising basis to produce and formulate improved enzyme
products. These products can have high temperature stability in process conditions in the range of 55–60 °C
(with present industrial products at 45–50 °C) and clearly improved specific activity,
essentially decreasing the protein dosage required for an efficient hydrolysis of lignocellulosic substrates.
New types of process configurations based on thermostable enzymes are discussed.
Biological and chemical pretreatment methods using liquid fraction of digestate (LFD), ammonia solution (AS), and NaOH were compared in the process of mesophilic anaerobic co-digestion of cattle manure and corn stover. The results showed that LFD pretreatment could achieve the same effect as the chemical pretreatment (AS, NaOH) at the performance of anaerobic digestion (AD). Compared with the untreated corn stover, the cumulative biomethane production (CBP) and the volatile solid (VS) removal rate of three pretreatment methods were increased by 25.40-30.12% and 14.48-16.84%, respectively, in the co-digestion of cattle manure and corn stover. T80 was 20-37.14% shorter than that of the control test (35±1days). LFD pretreatment not only achieved the same effect as chemical pretreatment, but also reduced T80 and improved buffer capacity of anaerobic digestion system. Therefore, this study provides meaningful insight for exploring efficient pretreatment strategy to stabilize and enhance AD performance for practical application.
Reduced graphene oxide functionalized with magnetic Fe3O4 nanoparticles and –PhSO3H groups (Fe3O4-RGO-SO3H) was reported for environmentally benign hydrolysis of cellulosic materials, which is an important process in integrated utilization of biomass resource. Except for –PhSO3H groups, –COOH and –OH groups derived from graphene oxide (GO) were also expected in the structure of Fe3O4-RGO-SO3H. Fe3O4-RGO-SO3H exhibited outstanding catalytic performance for the hydrolysis of cellulosic materials, due to its crumpling feature with clear layers and the coexistence of –COOH and –OH groups. The unique structure of Fe3O4-RGO-SO3H favors the accessibility of cellulose to the active sites of the material and facilitates the diffusion of the product molecules. –COOH groups on the surface of the material provide a large concentration of acidic functionality for hydrolyzing cellulose, while –OH groups readily adsorb cellulose through forming strong hydrogen bonds between –OH groups and the oxygen atoms in β-1,4 glycosidic bonds. Furthermore, Fe3O4-RGO-SO3H can also be easily separated from the reaction residue with an extra magnetic force and further used at least five times.
Among the three Aspergillus spp. niger, (A. oryzae, and A. fumigatus) screened for cellulolytic enzyme production potential, A. niger produced cellulolytic enzyme in relatively higher concentrations than the other two isolates. Enzyme produced by all three isolates was optimally active at pH 5.0. Celluloses from A niger and A fumigatus were optimally active at 55 degrees C, while the enzyme from A oryzae showed optimum activity at 50 degrees C. Cellulose from A niger and A fumigatus retained more than 80 and 70% activity, respectively, while cellulose from A oryzae could retain only 20% activity at 55 degrees C after 12 h. Cellulose from A niger exhibited better stability at higher temperatures than the enzyme from the other two Aspergillus spp., showing half-life (t(1/2)) of about 5 and 3 h at 70 and 80 degrees C, respectively. Zymogram revealed multiple forms of endoglucanase, cellobiohydrolase, and beta-glucosidase with molecular mass ranging between 28 and 154 kDa for cellulose from all three isolates. Hydrolysis of rice straw at 12.5% (w/v) with crude cellulose from A. niger HO resulted in fermentable sugar concentration and productivity of 66.2 g L-1 and 2.75 g L-1 h(-1) respectively, showing potential for the reported enzyme in biofuel industry.
The development of technology for biodiesel production is one of the attractive and challenging issues due to its possibility for commercial usage. Many patents have been investigated and proposed the intensification technology in order to improve and enhance the performance of biodiesel production process. In general, the invention topics mostly include feedstock materials, reactions, pretreatment technique, reactor/separation/purification technology and quality improvement. Therefore, this patent review summarizes the potential technology, development for biodiesel production presented in the mentioned topic and aims to keep the overview knowledge of the production process. Moreover, this review offers more clear comprehension and provides a guideline for further invention of any technologies for biodiesel production.
One of the great technological challenges in 21st century is the development of renewable energy technologies due to serious problems related with the production and use of energy. A new promising area of research grows rapidly which is called Nanotechnologies are considered nowadays one of the most recommended choices to solve this problem. This review aims to introduce several significant applications of nanotechnology in renewable energy systems. Papers reviewed including theoretical and experimental works related with nanotechnology applications in solar, hydrogen, wind, biomass, geothermal and tidal energies. A lot of literature are reviewed and summarized carefully in a useful tables to give a panoramic overview about the role of nanotechnology in improving the various sources of renewable energies. We think that this paper can be considered as an important bridge between nanotechnology and all available kinds of renewable energies. From the other side, further researches are required to study the effect of nanotechnology to enhance the renewable energy industry especially in geothermal, wind and tidal energies, since the available papers in these fields are limited.
Purified bacterial cellulase and xylanase were activated in the presence of calcium hydroxyapatite nanoparticles (NP) with concomitant increase in thermostability about 35% increment in production of d-xylose and reducing sugars from rice husk and rice straw was obtained at 80°C by the sequential treatment of xylanase and cellulase enzymes in the presence of NP compared to the untreated enzyme sets. Our findings suggested that if the rice husk and the rice straw samples were pre-treated with xylanase prior to treatment with cellulase, the percentage increase of reducing sugar per 100g of substrate (starting material) was enhanced by about 29% and 41%, respectively. These findings can be utilized for the extraction of reducing sugars from cellulose and xylan containing waste material. The purely enzymatic extraction procedure can be substituted for the harsh and bio-adverse chemical methods.
The effect of the Fe2+ concentrations ranging from 0 to 1500mg/L on the fermentative hydrogen production from glucose was investigated in batch tests by mixed cultures at 35°C and initial pH 7.0. The experimental results showed that in certain concentration range, Fe2+ was able to enhance the hydrogen production rate, the cumulative hydrogen quantity, and the hydrogen yield by the mixed cultures. The maximum cumulative hydrogen quantity of 302.3mL and the maximum hydrogen yield of 311.2mL/g glucose were obtained at the Fe2+ concentration of 300 and 350mg/L, respectively. The major soluble metabolites produced by the mixed cultures were ethanol, acetic acid, and butyric acid, with little or no propionic acid. The glucose degradation efficiency had the trend to decrease with increasing Fe2+ concentrations from 0 to 1500mg/L, but when the Fe2+ concentrations were lower than 350mg/L, the glucose degradation efficiency was between 96.25 and 98.78%, which is relatively high and kept unchanged with increasing Fe2+ concentrations. In certain concentration range, Fe2+ was able to enhance the biomass production yield. When the Fe2+ concentrations were between 100 and 750mg/L, there was a high biomass production yield plateau ranging from 259.2 to 334.2mg/g glucose. The final pH value had the trend to decrease with increasing Fe2+ concentrations from 0 to 1000mg/L, and the lowest final pH value was about 4.3 at the Fe2+ concentration of 1000mg/L.
It was the first time to study the enhancement effect of nanometer-sized gold particles on fermentative hydrogen production from artificial wastewater. A biohydrogen production system coupling the polysaccharide degradation by two cultures and hydrogen production using gold nanoparticles as a catalyst was investigated. Data were obtained from tests operating with cultures enriched from natural environment, which included preheat-treated mixed culture and non-heat-treated mixed culture. The percentages and yields of hydrogen produced in the tests using gold nanoparticles were all higher than the corresponding blank test. The tests with 5-nm-gold particles behaved better than others, especially for the preheat-treated one. The maximum cumulative yield of hydrogen obtained at the test with 5-nm-gold particles was 4.48mol per mol sucrose, which represents the conversion efficiency of sucrose to hydrogen reached 56%. The results indicated that gold nanoparticles could remarkably improve the bioactivity of hydrogen-producing microbes and the enhancement effect strongly depended on the size of gold particles. This work suggests a promising method to enhance the catalytic activity of hydrogenases in the microbes and will be of great importance in biohydrogen production.
The covalent binding of cellulase enzyme complex to magnetic (Fe3O4) nanoparticles via carbodiimide activation was investigated. The size, structure, and morphology of the magnetic nanoparticles were determined using transmission electron microscopy (TEM). The micrographs revealed a mean diameter of 13.3nm and showed that the magnetic particles remained discrete with no significant change in size after binding of the enzyme complex. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated binding to the magnetic nanoparticles and suggested a possible binding mechanism. Maximum binding (∼90%) occurred at low enzyme loadings (1–2mg) and the enzyme-to-support saturation point occurred at a weight ratio of 0.02. Thermal measurements for the nanoparticles indicated increased stability over a broader range of temperatures, with a peak relative enzyme activity at 50°C. The ionic forces between the enzyme and support surface caused a shift in the optimum pH from 4.0 to 5.0.
Silver nanoparticles were added into anaerobic batch reactors to enhance acidogenesis and fermentative hydrogen production simultaneously. The effects of silver nanoparticles concentration (0-200nmolL(-1)) and inorganic nitrogen concentration (0-4.125gL(-1)) on cell growth and hydrogen production were investigated using glucose-fed mixed bacteria dominated by Clostridium butyricum. The tests with silver nanoparticles exhibited much higher H2 yields than the blank, and the maximum hydrogen yield (2.48mol/molglucose) was obtained at the silver concentration of 20nmolL(-1). Presence of silver nanoparticles reduced the yield of ethanol, but increased the yield of acetic acid. The high silver nanoparticles had higher cell biomass production rate. Further study using the alkaline pretreated culture as inoculum was carried out to verify the positive effect of silver nanoparticles on H2 production. Results demonstrated that silver nanoparticles could not only increase the hydrogen yield, but reduce the lag phase for hydrogen production simultaneously.
This paper investigated the enhancement effect of nanometre-sized metallic (Pd, Ag and Cu) or metallic oxide (Fe(x)O(y)) nanoparticles on fermentative hydrogen production from glucose by a Clostridium butyricum strain. These nanoparticles (NP) of about 2-3nm were encapsulated in porous silica (SiO(2)) and were added at very low concentration (10(-6)molL(-1)) in batch hydrogen production test. The cultures containing iron oxide NP produced 38% more hydrogen with a higher maximum H(2) production rate (HPR) of 58% than those without NP or with silica particles only. The iron oxide NP were used in a 2.5L sequencing-batch reactor and showed no significant effect on the yields (established at 2.2mol(hydrogen)mol(glucose)(-1)) but an improvement of the HPR (+113%, reaching a maximum HPR of 86mL(hydrogen)L(-1)h(-1)). These results suggest an improvement of the electron transfers trough some combinations between enzymatic activity and inorganic materials.
Second-generation feedstock, especially nonfood lignocellulosic biomass is a potential source for biofuel production. Cost-intensive physical, chemical, biological pretreatment operations and slow enzymatic hydrolysis make the overall process of lignocellulosic conversion into biofuels less economical than available fossil fuels. Lignocellulose conversions carried out at ⩽50°C have several limitations. Therefore, this review focuses on the importance of thermophilic bacteria and thermostable enzymes to overcome the limitations of existing lignocellulosic biomass conversion processes. The influence of high temperatures on various existing lignocellulose conversion processes and those that are under development, including separate hydrolysis and fermentation, simultaneous saccharification and fermentation, and extremophilic consolidated bioprocess are also discussed.
The production of cellulases by Trichodermacitrinoviride fermented on marc of Artemisiaannua, and bioconversion of the same marc by produced cellulase system was studied. The effects of pretreatments, substrate concentration, particle size, initial pH, temperature and concentration of the medium components on production of FPase, endoglucanase and β-glucosidase were monitored and comparatively evaluated. Among the three pretreatment processes, alkali hydrolysis with autoclaving was found to be most suitable for production of all the three enzymes. Optimum production of FPase, endoglucanase and β-glucosidase was obtained at 96 h, 96 h and 72 h of fermentation period, respectively. Substrate concentration of 1% with particle size between 200 μm and 475 μm gave the higher yields. Higher production of all the three enzymes was obtained with initial pH value of 5.5, temperature of 28 °C and 75% of mineral salt solution. Partially purified enzyme system obtained by optimized fermentation procedure, was applied for saccharification. Forty six percent of saccharification was noticed after 48 h of incubation on alkali hydrolyzed and autoclaved substrate which was 3.26 fold more than that of unpretreated substrate.
A novel cellulase gene encoding a thermostable endoglucanase from the thermophilic eubacterium Fervidobacterium nodosum Rt17-B1 was cloned and expressed, which is the first cellulase cloned from the organisms of genus Fervidobacterium and designated as FnCel5A for being a member of glycoside hydrolase family 5, and the enzymatic properties were characterized. The cellulase was overexpressed in Escherichia coli with a high protein content and good solubility in water, and could be easily purified. The purified recombinant cellulase shows high hydrolytic activities on carboxylmethyl cellulose, regenerated amorphous cellulose, β-d-glucan from barley and galactomannan, with the optimum temperature of 80–83 °C and the optimum pH of 5.0–5.5. Furthermore, this enzyme is highly thermostable and has a half-life of 48 h at 80 °C. With such a combination of thermostability and high activities, this cellulase is expected to be useful for hydrolysis of cellulosic and hemicellulosic substrates at high temperatures, and for industrial hydrolysis of plant cellulose during long-time processing at the elevated temperatures, particularly in converting biomass into biofuels.
This paper discusses the perspective of renewable energy (wind, solar, wave and biomass) in the making of strategies for a sustainable development. Such strategies typically involve three major technological changes: energy savings on the demand side, efficiency improvements in the energy production, and replacement of fossil fuels by various sources of renewable energy. Consequently, large-scale renewable energy implementation plans must include strategies of how to integrate the renewable sources in coherent energy systems influenced by energy savings and efficiency measures. Based on the case of Denmark, this paper discusses the problems and perspectives of converting present energy systems into a 100 percent renewable energy system. The conclusion is that such development will be possible. The necessary renewable energy sources are present, if further technological improvements of the energy system are achieved. Especially technologies of converting the transportation and the introduction of flexible energy system technologies are crucial.
Various medium components (carbon and nitrogen sources, iron, inoculum size) and environmental factors (initial pH and the agitation speed) were evaluated for their effects on the rate and the yield of hydrogen production by Clostridium saccharoperbutylacetonicum. Among the carbon sources assessed, cells grown on disaccharides (lactose, sucrose and maltose) produced on the average more than twice (2.81 mol-H2/mol sugar) as much hydrogen as monosaccharides (1.29 mol-H2/mol sugar), but there was no correlation between the carbon source and the production rate. The highest yield (2.83 mol/mol) was obtained in lactose and sucrose but the highest production rate (1.75 mmol/h) in sucrose. Using glucose as carbon source, yeast extract was the best nitrogen source. A parallel increase between the production rate and the yield was obtained by increasing glucose concentration up to 40 g/l (1.76 mol-H2/mol, 3.39 mmol/h), total nitrogen as yeast extract up to 0.1% (1.41 mol/mol, 1.91 mmol/h) and agitation up to 100 rev/min (1.66 mol-H2/mol, 1.86 mmol/h). On the other hand, higher production rates were favoured in preference to the yield at a neutral initial pH 7 (2.27 mmol/h), 1000 mg iron/l or more (1.99 mmol/h), and a larger inoculum size, 10%, (2.36 mmol/h) whereas an initial alkaline pH of 8.5 (1.72 mol/mol), a lower iron concentration of 25 mg/l (1.74 mol/mol) and smaller inoculum size, 1%, (1.85 mol/mol) promoted higher yield over
production rate.
This review summarized several main factors influencing fermentative hydrogen production. The reviewed factors included inoculum, substrate, reactor type, nitrogen, phosphate, metal ion, temperature and pH. In this review, the effect of each factor on fermentative hydrogen production and the advance in the research of the effect were briefly introduced and discussed, followed by some suggestions for the future work of fermentative hydrogen production. This review showed that there usually existed some disagreements on the optimal condition of a given factor for fermentative hydrogen production, thus more researches in this respect are recommended. Furthermore, most of the studies on fermentative hydrogen production were conducted in batch mode using glucose and sucrose as substrate, thus more studies on fermentative hydrogen production in continuous mode using organic wastes as substrate are recommended.
The state of the art of hydrolysis-fermentation technologies to produce ethanol from lignocellulosic biomass, as well as developing technologies, is evaluated. Promising conversion concepts for the short-, middle- and long-term are defined. Their technical performance was analysed, and results were used for economic evaluations. The current available technology, which is based on dilute acid hydrolysis, has about 35% efficiency (HHV) from biomass to ethanol. The overall efficiency, with electricity co-produced from the not fermentable lignin, is about 60%. Improvements in pre-treatment and advances in biotechnology, especially through process combinations can bring the ethanol efficiency to 48% and the overall process efficiency to 68%. We estimate current investment costs at 2.1 k€/kWHHV (at 400 MWHHV input, i.e. a nominal 2000 tonne dry/day input). A future technology in a 5 times larger plant (2 GWHHV) could have investments of 900 k€/kWHHV. A combined effect of higher hydrolysis-fermentation efficiency, lower specific capital investments, increase of scale and cheaper biomass feedstock costs (from 3 to 2 €/GJHHV), could bring the ethanol production costs from 22 €/GJHHV in the next 5 years, to 13 €/GJ over the 10–15 year time scale, and down to 8.7 €/GJ in 20 or more years.
Air-dried samples of sweet sorghum, sugarcane bagasse, wheat straw, maize leaves and silphium were utilized without chemical pretreatment as sole energy and carbon sources for H2 production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus. The specific H2 production rates and yields were determined in the batch fermentation process. The best substrate was wheat straw, with H2 production capacity of 44.7 L H2 (kg dry biomass)−1 and H2 yield of 3.8 mol H2 (mol glucose)−1. Enzymatically pretreated maize leaves exhibited H2 production of 38 L H2 (kg dry biomass)−1. Slightly less H2 was obtained from homogenized whole plants of sweet sorghum. Sweet sorghum juice was an excellent H2 source. Silphium trifoliatum was also fermented though with a moderate production. The results showed that drying is a good storage method and raw plant biomass can be utilized efficiently for thermophilic H2 production. The data were critically compared with recently published observations.
To enhance ethanol production in Thermoanaerobacterium aotearoense, the lactate dehydrogenase (ldh) gene, which is responsible for lactic acid production in a key branch pathway, was successfully disrupted via homologous recombination. ldh-up and ldh-down were designed and amplified based on JW/SL-YS485-AY 278026, and they were subsequently used as homologous fragments with an inserted erythromycin resistance gene to construct the targeted vector based on pBLUESCRIPT II SK(+). Southern hybridization and PCR-based assay definitely confirmed that the ldh gene in the Δldh mutant was disrupted by the insertion of the erythromycin resistance gene. Compared with the wild type, the Δldh mutant exhibited increases of 31.0% and 31.4% in cell yield under glucose and xylose cultivation, respectively, probably because knocking out the ldh gene results in increased acetate and ATP levels. Knockout of lactate dehydrogenase produced 2.37- and 2.1-fold increases in the yield of ethanol (mole/mole substrate) under glucose and xylose cultivation, respectively. Moreover, no lactic acid was detected in Δldh mutant fermentation mixtures (detection limit of HPLC: 0.5 mM), but lactic acid was readily detected for growth of the wild-type strain on both glucose and xylose, with final concentrations up to 59.24 mM and 56.06 mM, respectively. The success of this process thoroughly demonstrates the methodological possibility of gene knockout through homologous recombination in Thermoanaerobacterium.
Hydrolysates resulting from the lignocellulosic biomass pretreatment in bioethanol production may be used to produce biogas. Such hydrolysates are rich in xylose but also contain lignin polymers or oligomers as well as phenolic and furan compounds, such as syringaldehyde, vanillin, HMF, furfural. The aim of this study was to investigate the impact of these byproducts on biomethane production from xylose. The anaerobic digestion of the byproducts alone was also investigated. No inhibition of the anaerobic digestion of xylose was observed and methane was obtained from furans: 430 mL CH(4)/g of furfural and 450 mL CH(4)/g of HMF; from phenolic compounds: 453 mL CH(4)/g of syringaldehyde and 105 mL CH(4)/g of vanillin; and, to a lesser extent, from lignin polymers: from 14 to 46 mL CH(4)/g MV. The use of different natural polymers (lignosulfonates, organosolv and kraft lignins) and synthetic dehydrogenative polymers showed that higher S/G ratios and lower molecular weights in lignin polymers led to greater methane production.
Several new types of carriers and technologies have been implemented in the recent past to improve traditional enzyme immobilization which aimed to enhance enzyme loading, activity and stability to decrease the enzyme biocatalyst cost in industrial biotechnology. These include cross-linked enzyme aggregates, microwave-assisted immobilization, click chemistry technology, mesoporous supports and most recently nanoparticle-based immobilization of enzymes. The union of the specific physical, chemical, optical and electrical properties of nanoparticles with the specific recognition or catalytic properties of biomolecules has led to their appearance in myriad novel biotechnological applications. They have been applied time and again for immobilization of industrially important enzymes with improved characteristics. The high surface-to-volume ratio offered by nanoparticles resulted in the concentration of the immobilized entity being considerably higher than that afforded by experimental protocols based on immobilization on planar 2-D surfaces. Enzymes immobilized on nanoparticles showed a broader working pH and temperature range and higher thermal stability than the native enzymes. Compared with the conventional immobilization methods, nanoparticle based immobilization served three important features; (i) nano-enzyme particles are easy to synthesize in high solid content without using surfactants and toxic reagents, (ii) homogeneous and well defined core-shell nanoparticles with a thick enzyme shell can be obtained, and (iii) particle size can be conveniently tailored within utility limits. In addition, with the growing attention paid to cascade enzymatic reaction and in vitro synthetic biology, it is possible that co-immobilization of multi-enzymes could be achieved on these nanoparticles.
Lignocellulosic biomass contains a variety of carbohydrates, and their conversion into ethanol by fermentation requires an efficient microbial platform to achieve high yield, productivity, and final titer of ethanol. In recent years, growing attention has been devoted to the development of cellulolytic and saccharolytic thermophilic bacteria for lignocellulosic ethanol production because of their unique properties. First of all, thermophilic bacteria possess unique cellulolytic and hemicellulolytic systems and are considered as potential sources of highly active and thermostable enzymes for efficient biomass hydrolysis. Secondly, thermophilic bacteria ferment a broad range of carbohydrates into ethanol, and some of them display potential for ethanologenic fermentation at high yield. Thirdly, the establishment of the genetic tools for thermophilic bacteria has allowed metabolic engineering, in particular with emphasis on improving ethanol yield, and this facilitates their employment for ethanol production. Finally, different processes for second-generation ethanol production based on thermophilic bacteria have been proposed with the aim to achieve cost-competitive processes. However, thermophilic bacteria exhibit an inherent low tolerance to ethanol and inhibitors in the pretreated biomass, and this is at present the greatest barrier to their industrial application. Further improvement of the properties of thermophilic bacteria, together with the optimization production processes, is equally important for achieving a realistic industrial ethanol production.
The effects of hematite nanoparticles concentration (0-1600 mg/L) and initial pH (4.0-10.0) on hydrogen production were investigated in batch assays using sucrose-fed anaerobic mixed bacteria at 35°C. The optimum hematite nanoparticles concentration with an initial pH 8.48 was 200mg/L, with the maximum hydrogen yield of 3.21 mol H(2)/mol sucrose which was 32.64% higher than the blank test. At 200mg/L hematite nanoparticles concentration, further initial pH optimization experiments indicated that at pH 6.0 the maximum hydrogen yield reached to 3.57 mol H(2)/mol sucrose and hydrogen content was 66.1%. The slow release of hematite nanoparticles had been recorded by transmission electron microscopy (TEM). In addition, TEM analysis indicated that the hematite nanoparticles can affect the shape of bacteria, namely, its length increased from ca. 2.0-3.6 μm to ca. 2.6-5.6 μm, and width became narrower.
Lignocellulose is the most abundant carbohydrate source in nature and represents an ideal renewable energy source. Thermostable enzymes that hydrolyze lignocellulose to its component sugars have significant advantages for improving the conversion rate of biomass over their mesophilic counterparts. We review here the recent literature on the development and use of thermostable enzymes for the depolymerization of lignocellulosic feedstocks for biofuel production. Furthermore, we discuss the protein structure, mechanisms of thermostability, and specific strategies that can be used to improve the thermal stability of lignocellulosic biocatalysts.
Biofuel produced from lignocellulosic materials, so-called second generation bioethanol shows energetic, economic and environmental advantages in comparison to bioethanol from starch or sugar. However, physical and chemical barriers caused by the close association of the main components of lignocellulosic biomass, hinder the hydrolysis of cellulose and hemicellulose to fermentable sugars. The main goal of pretreatment is to increase the enzyme accessibility improving digestibility of cellulose. Each pretreatment has a specific effect on the cellulose, hemicellulose and lignin fraction thus, different pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis and fermentation steps. This paper reviews the most interesting technologies for ethanol production from lignocellulose and it points out several key properties that should be targeted for low-cost and advanced pretreatment processes.
Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source for the limited crude oil. There are mainly two processes involved in the conversion: hydrolysis of cellulose in the lignocellulosic biomass to produce reducing sugars, and fermentation of the sugars to ethanol. The cost of ethanol production from lignocellulosic materials is relatively high based on current technologies, and the main challenges are the low yield and high cost of the hydrolysis process. Considerable research efforts have been made to improve the hydrolysis of lignocellulosic materials. Pretreatment of lignocellulosic materials to remove lignin and hemicellulose can significantly enhance the hydrolysis of cellulose. Optimization of the cellulase enzymes and the enzyme loading can also improve the hydrolysis. Simultaneous saccharification and fermentation effectively removes glucose, which is an inhibitor to cellulase activity, thus increasing the yield and rate of cellulose hydrolysis.
The molecular details behind hydrogen evolution during fermentation are reviewed. Hydrogen is evolved by hydrogenase, a class of enzymes containing complex metallo-centers. In most cases, sugars are degraded to pyruvate which in turn is converted to a variety of fermentation products. Various pathways leading to fermentative hydrogen generation are outlined and discussed. Thermophilic fermentations have higher yields than mesophilic ones. Yields are thought to be limited to 4H2 per glucose under standard conditions. The highlights of some actual studies of fermentations are presented and ways of potentially increasing hydrogen yields are discussed. It may be possible to achieve higher hydrogen yields by carrying out fermentations under microaerobic conditions where limited respiration could provide additional reducing power to drive the nearly complete conversion of sugar substrates to hydrogen.
The increased concern for the security of the oil supply and the negative impact of fossil fuels on the environment, particularly greenhouse gas emissions, has put pressure on society to find renewable fuel alternatives. The most common renewable fuel today is ethanol produced from sugar or grain (starch); however, this raw material base will not be sufficient. Consequently, future large-scale use of ethanol will most certainly have to be based on production from lignocellulosic materials. This review gives an overview of the new technologies required and the advances achieved in recent years to bring lignocellulosic ethanol towards industrial production. One of the major challenges is to optimize the integration of process engineering, fermentation technology, enzyme engineering and metabolic engineering.
Lignocellulosic biomass represents a rather unused source for biogas and ethanol production. Many factors, like lignin content, crystallinity of cellulose, and particle size, limit the digestibility of the hemicellulose and cellulose present in the lignocellulosic biomass. Pretreatments have as a goal to improve the digestibility of the lignocellulosic biomass. Each pretreatment has its own effect(s) on the cellulose, hemicellulose and lignin; the three main components of lignocellulosic biomass. This paper reviews the different effect(s) of several pretreatments on the three main parts of the lignocellulosic biomass to improve its digestibility. Steam pretreatment, lime pretreatment, liquid hot water pretreatments and ammonia based pretreatments are concluded to be pretreatments with high potentials. The main effects are dissolving hemicellulose and alteration of lignin structure, providing an improved accessibility of the cellulose for hydrolytic enzymes.
Energy production from biomass (Part2): conversion technologies
- P Kendry
Kendry P (2002) Energy production from biomass (Part2): conversion
technologies. Bioresour Technol 83:47-54. doi:10.1016/S0960-8524(01)00119-5
Production of cellulases using agriculture waste: application in biofuels production
- N Srivastava
- P Jaiswal
Srivastava N, Jaiswal P (2016) Production of cellulases using
agriculture waste: application in biofuels production. In: Gupta
RK, Singh SS (eds) Environmental biotechnology: a new
approach chapter 15. Daya Publishing House, New Delhi,
pp 233-244
Application of thermostable cellulases in biofuels production
- N Srivastava
- R Rawat
- H S Oberoi
Srivastava N, Rawat R, Oberoi HS (2014b) Application of thermostable cellulases in biofuels production. Recent Adv Bioenergy Res III:121-129. ISBN 978-81-927097-2-7