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![Schematic diagram of the lignocellulosic structure, which is composed of cellulose, hemicellulose, and lignin [17].](profile/Saleha-Al-Mardeai/publication/363894209/figure/fig1/AS:11431281086857461@1664368447026/Schematic-diagram-of-the-lignocellulosic-structure-which-is-composed-of-cellulose.png)
Schematic diagram of the lignocellulosic structure, which is composed of cellulose, hemicellulose, and lignin [17].
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The depletion of fossil fuel resources and the negative impact of their use on the climate have resulted in the need for alternative sources of clean, sustainable energy. One available alternative, bioethanol, is a potential substitute for, or additive to, petroleum-derived gasoline. In the lignocellulose-to-bioethanol process, the cellulose hydrol...
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... by hemicellulose, which is estimated to be 25-30%, and lignin, which is 15-20% [13]. A schematic diagram of the lignocellulosic structure is shown in Figure 1. Cellulose is composed of repeating cellobiose units, which comprise two glucose molecules joined together by a β-1,4 glycosidic linkage. ...
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... [13] Various membrane reactor systems using a sieving mechanism, which enabled the retention of unhydrolyzed biomass and enzymes and permeation of reaction products, were previously studied to overcome the barriers mentioned above. [14][15] The improvement in substrate conversion by applying membrane separation to product removal has been proven in many investigations. [16][17][18] The main advantage of using membrane reactors is the ability to recover and reuse enzymes and receive pure monosaccharides in the permeate. ...
This paper presents the study concerning the impact of the basic operational parameters on the performance of an innovative microfiltration membrane reactor applied for enzymatic hydrolysis of lignocellulosic biomass. The concept and basic hydrody-namics of the reactor with tubular ceramic membranes and a propeller agitator were shown. Besides, the efficiency of enzymatic hydrolysis of corn straw was studied to check reactor functionality. It has been proven that the proposed reactor construction can improve the microfiltration of lignocellulosic suspension by reducing the cake layer on the membrane surface. Increasing the rotational speed of the propeller agitator also improved the filtration efficiency. The permeate flux during the microfiltration experiments was lower for smaller lignocellulose biomass fraction (D < 425 μm) when compared to the less fragmented corn straw (425 < D < 900 μm). For larger solid fractions, a stirring speed increase enhanced the separation efficiency regardless of the differences in biomass concentration. In contrast, this trend for the finer biomass fraction was only noticeable for the highest used biomass concentration (C = 2.0%). Considering the enzymatic hydrolysis of corn straw, membrane separation of reaction products positively influenced the process yield, and the results depended on the applied operational parameters.
... Complete LB breakdown often needs many combinations of hydrolytic enzymes, such as cellulases, hemicellulases, and other enzymes (Himmel et al., 1997). Cellulases are classified into three major types (endoglucanase, exoglucanases, and β-glucosidase); based on their mechanism of action, they convert the cellulose polymer into glucose monomers units (Al-Mardeai et al., 2022). Besides these, other biocatalysts that break hemicelluloses include glucuronide, β-xylosidase, acetylesterase, xylanase, galactomannase, and glucomannase (Guo et al., 2022). ...
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.
... [24,25]. These enzymes are essential for the hydrolysis of plant biomass as they cause complete cellulose hydrolysis by their consecutive actions to form a glucose monomer for bioethanol production [60]. Additionally, cellulases have been widely applied in brewing, bread, detergents, textiles, pulp, and paper industries. ...
The grave environmental, social, and economic concerns over the unprecedented exploitation of non-renewable energy resources have drawn the attention of policy makers and research organizations towards the sustainable use of agro-industrial food and crop wastes. Enzymes are versatile biocatalysts with immense potential to transform the food industry and lignocellulosic biorefineries. Microbial enzymes offer cleaner and greener solutions to produce fine chemicals and compounds. The production of industrially important enzymes from abundantly present agro-industrial food waste offers economic solutions for the commercial production of value-added chemicals. The recent developments in biocatalytic systems are designed to either increase the catalytic capability of the commercial enzymes or create new enzymes with distinctive properties. The limitations of low catalytic efficiency and enzyme denaturation in ambient conditions can be mitigated by employing diverse and inexpensive immobilization carriers, such as agro-food based materials, biopolymers, and nanomaterials. Moreover, revolutionary protein engineering tools help in designing and constructing tailored enzymes with improved substrate specificity, catalytic activity, stability, and reaction product inhibition. This review discusses the recent developments in the production of essential industrial enzymes from agro-industrial food trash and the application of low-cost immobilization and enzyme engineering approaches for sustainable development.
... Complete LB breakdown often needs many combinations of hydrolytic enzymes, such as cellulases, hemicellulases, and other enzymes (Himmel et al., 1997). Cellulases are classified into three major types (endoglucanase, exoglucanases, and β-glucosidase); based on their mechanism of action, they convert the cellulose polymer into glucose monomers units (Al-Mardeai et al., 2022). Besides these, other biocatalysts that break hemicelluloses include glucuronide, β-xylosidase, acetylesterase, xylanase, galactomannase, and glucomannase (Guo et al., 2022). ...
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
This study aimed to investigate the influence of Tween 80 on the enzymatic hydrolysis of corn straw integrated with two-step membrane separation of reaction products and recovery of enzymes. Supplementation of the reaction mixture with 0.6% (w/v) Tween 80 resulted in an increased yield of hydrolysis carried out with Cellic® CTec2, both in batch and membrane bioreactor, compared to the enzymatic process conducted without surfactant. In the microfiltration membrane bioreactor, the glucan and xylan saccharification yields were, on average 31.2% and 25.5%, respectively, higher than without using Tween 80. Besides, the addition of Tween 80 significantly enhanced membrane permeability during hydrolysis without impacting its retention coefficients toward catalytic proteins. The ultrafiltration enables partial enzyme recovery and supply enzymes for a new hydrolysis process. Results obtained in this study proved the benefits of using Tween 80 in enzymatic hydrolysis of lignocellulosic biomass. Reduction of membrane fouling by surfactant during hydrolysis increases the filtration efficiency and extends the membrane lifetime.
The lignocellulosic biomasses (LBs) are considered to be the most important feedstocks for the production of a wide range of biorefining products, including biofuels. However, the complex and recalcitrant structure of these LBs is the only major concern, because the recalcitrant nature of biomass provides rigidity to the biomass and makes it resistant. In this context, pretreatment of biomass is highly required to release the carbohydrate polymers from the LB. Among the various pretreatments, enzymatic hydrolysis is essentially required to obtain fermentable sugars and it is the most expensive step in biorefinery. The application of cellulolytic enzymes in free form is not sustainable as their recovery and reuse are not possible, whereas immobilization of such enzymes on the solid support can facilitate its recovery and reuse and also helps to reduce the cost of the process. Recently, different nanomaterials such as nanoparticles (including magnetic nanoparticles [MNPs]), carbon nanotubes, nanofibers, and nanographenes have attracted considerable interest due to their novel properties. Immobilization of enzymes on nanomaterials such as MNPs (nanobiocatalysts) can enhance the recovery of enzymes and it can be reused up to 10 cycles of hydrolysis making the process economically viable. In the present chapter, focus is given on recent advances in the application of different nanomaterials for enzyme immobilization and their utilization in the hydrolysis of LBs. In addition, different enzyme immobilization techniques, conventional enzymatic hydrolysis of biomass, etc. are also discussed.
