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This review presents the main directions and experimental data aimed at searching for active producers of lipids among different species of microorganisms and ways to optimize the lipidogenesis process in the most promising stains. It was shown that enzymatic processes can be directed by maintaining the necessary cultivation conditions. The influen...
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... storing reserve energy and is accumulated by different microbes (e.g., Alcaligenes, Azotobacter, Bacillus, Nocardia, Pseudomonas, and Rhizobium). Under cerr tain conditions, several species, particularly Alcalii genes eutrophus and Azotobacter beijerinckii, are able to accumulate this polymer in such an amount reaching up to 70% of their dry mass (Fig. ...
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This review presents the main directions of domestic and foreign research, also experimental data to search among the different species of yeasts – active producers of lipids and the ways to lipidogenesis process optimization in the most promising strains. It was shown that maintaining the necessary conditions of cultivation can direct enzymatic pr...
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... Then, phosphatidic acid phosphatase (PAP) dephosphorylates phosphatidic acid, resulting in the formation of diacylglycerol. Finally, diacylglycerol acyltransferases (Dga1, Dga2) attach an acyl group from acyl-CoA to the diacylglycerol's to produce TAG (Tkachenko et al., 2013). Later on, wax esters are converted to TAGs in cells. ...
Background:
Population expansion, global warming, and food scarcity have all increased the demand for alternative lipid sources to ensure food and energy security. Furthermore, over the last few decades, industrialization has posed a significant environmental risk to the world through its waste. Utilization of agri-food waste and byproducts as a substrate by oleaginous microorganisms for production of microbial lipids could be a phenomenal approach.
Scope and approach:
Oleaginous microorganisms have numerous advantages, including a shorter life span, rapid growth rate, ease of cultivation, ability to use a variety of substrates, and adaptability to metabolic/genetic changes. Exploiting oleaginous microorganisms for the production of microbial lipids can be viewed as an alternative sustainable food source as well as a versatile raw material for the production of food additives, surfactants, and tailored triacylglycerol's.
Key Findings and Conclusion:
Microbial oil production processes that mimic plant, animal, and marine lipids are non-toxic, sustainable, and adaptable, as well as energy efficient. Recent research on oleaginous microorganisms, as well as recent interventions in waste management, have resulted in microbial oils being the next and most viable product for a variety of end-user applications and an efficient way of waste management.
... The variations in FAME proportions could be due to the depletion of nutrition in the SWW [25], impacting the growth and the FAME profile of yeast. Tkachenko et al. [47], as well as Athenstaedt and Daum [48], reported that the fatty acid profile of oleaginous yeast depends entirely on its growth conditions, including environmental stress or physical stress. Similarly, Yen et al. [49] observed a variation in fatty acid profile when oleaginous yeast, Rhodotorula mucilaginosa, was cultivated in a 5-L airlift bioreactor using seawater instead of pure water. ...
The cost of biodiesel production and the requirement of raw ingredients are the primary constraints that need to be addressed while searching for viable alternative fuels to petrol and diesel. Oleaginous yeasts are gaining wider acceptance as biofuel candidates among oil-rich crops/microbes. The present investigation aimed to integrate the agro-industrial wastewater stream as a nutrient source for the cultivation of oleaginous yeast and to use the resultant biomass and lipid as a feedstock for biofuel synthesis. The yeast biomass grown in sago processing wastewater contained 7.21% moisture content, 69.01% volatile matter, 12.61% fixed carbon, and 11.16% ash content. The ultimate analysis determined the contents of carbon (40.43%), nitrogen (5.14%), hydrogen (4.62%), sulfur (0.54%), and oxygen (49.27%). The heating value of yeast biomass was 16.54 MJ kg⁻¹. The thermal behavior of yeast biomass also suggests its potential use as an energy source. The FTIR spectrum of biomass had major lipid (3030–2800 cm⁻¹ and 1500–1350 cm⁻¹) and carbohydrate (1250 cm⁻¹ and 1000 cm⁻¹) functional peaks. Further FAME profiling revealed that the yeast biomass is primarily composed of stearic, oleic, linoleic, and linolenic acids, similar to the vegetable oils. The fuel characteristics of yeast biodiesel (SV, 168.87 mg KOH g⁻¹; IV, 120 mg I2 100 g⁻¹; CN, 61.79; and KV, 3.16 mm² s⁻¹) are also within the ASTM standard limits, suggesting that yeast biomass could be a sustainable and economically viable feedstock for both solid and liquid biofuel production.
... Rhodotorula mucilaginosa was used to produce single-cell lipids (SCOs), and the most suitable medium composition and lipid production conditions were found by exploring the different nutrient elements in the medium. The nature of fatty acids synthesized by oil-producing yeast depends on the nutrient content of the provided medium and on culture conditions [3][4][5][6][7][8][9][10]. Yeast lipids mainly include triglycerides, such as oleic acid (C18:1), linoleic acid (C18:2), stearic acid (C18:0), palmitic acid (C16:0) or palmitoleic acid (C16:1) [11,12]. ...
At the 2021 United Nations Climate Change Conference (COP26), many countries in the world agreed to reach the goal of net-zero greenhouse gas emissions by 2050. This issue constrains energy use, petrochemical use, and related manufacturing production patterns. It is undeniable that the diesel engine of large equipment is still widely used in engineering applications, and it will not disappear in a short time. Many industrial projects still have to face the use of diesel engines. This study was focused on the development of oil-producing microorganisms to generate lipids. The oleaginous yeast Rhodotorula mucilaginosa (R. mucilaginosa) was selected for liquid-state cultivation, and the conditions for growth of the yeast cells were assessed. For the liquid fermentation culture with a fixed inoculation amount of 5%, it was determined that a suitable oil-producing culture was obtained on the sixth day, and the optimum conditions involved a carbon source concentration of 60 g/L, a yeast extract concentration of 0.5 g/L, and a KH2PO4 concentration of 7.0 g/L for each batch of culture experiments. In addition, the extraction method and solvent for the extraction of R. mucilaginosa lipids were chosen. The acid-heat method using the green organic solvent ethyl acetate exhibited the best performance for extraction of yeast lipids under environmentally friendly and safe conditions. The analysis of lipids showed that the fatty acids obtained primarily contained C16:0, C18:1 and C18:2, and especially C18:1 (41%) lipids, indicating that R. mucilaginosa lipids are a good bio-oil source for the production of biodiesel.
... There are several new methods known for increasing lipid production in oil-producing yeast, such as genetic engineering to improve the strain, modifying the culture conditions (temperature, pH, stirring rate), and improving the bioreactor used for culturing (batch or sequencing batch model). The nature of fatty acids synthesized by oil-producing yeast depends on the nutrient content of the provided medium and on culture conditions [9,10]. R. mucilaginosa belongs to the phyla Basidiomycota, Puccinia, and Spore. ...
This study was focused on the development of oil-producing microorganisms to generate lipids. The yeast Rhodotorula mucilaginosa (R. mucilaginosa) was selected for liquid-state cultivation, and the conditions for growth of the yeast cells were assessed. Additionally, the relationships between different nutrient elements and the growth of R. mucilaginosa were explored. The lipid accumulation of R. mucilaginosa is increased under nitrogen-restricted conditions. As the concentration of the carbon source increases, the accumulation of lipids is increased. However, if the carbon source concentration is further increased, the growth of yeast is inhibited. From a large-scale liquid fermentation culture with a fixed inoculation amount of 5%, and from a batch of culture experiments, it was determined that a suitable oil-producing culture was obtained on the 6th day, and the optimum conditions involved a carbon source concentration of 60 g/L, a nitrogen source concentration of 0.5 g/L, and a KH2PO4 concentration of 7.0 g/L. After utilizing different carbon sources in this study, it was found that glucose was the carbon source most conducive to the accumulation of R. mucilaginosa lipids. In addition, the extraction method and solvent for the extraction of R. mucilaginosa lipids were chosen. The acid-heat method using the green organic solvent ethyl acetate exhibited the best performance for extraction of yeast lipids under environmentally friendly and safe conditions. The analysis of lipids showed that the fatty acids obtained primarily contained C16:0, C18:1 and C18:2, and especially C18:1 (41%) lipids, indicating that R. mucilaginosa lipids are a good bio-oil source for the production of biodiesel.
... Phosphatidic acid is then dephosphorylated to form diacylglycerol by phosphatidic acid phosphatase. Finally, diacylglycerol acyltransferases (Dga1, Dga2) transfer an acyl group from acyl-CoA to the third carbon of diacylglycerol to form TAG (Tkachenko et al. 2013). Acylation of diacylglycerol also includes an acyl-CoAindependent esterification reaction by phospholipid diacylglycerol acyltransferase (Lro1), which transfers a fatty acid from a phospholipid (Lazar et al. 2018). ...
The oleaginous yeast Lipomyces starkeyi is an excellent sustainable lipid producer, which can convert industrial wastes into lipids and accumulate triacylglycerols (TAG) by > 70% of its dry cell weight. Recent studies using omics technologies applied in L. starkeyi have aided in obtaining greater understanding of the important mechanisms of lipid metabolism in L. starkeyi. Therefore, the development of genetic engineering tools for L. starkeyi has led to accelerated efforts for a highly efficient production of lipids.
This review focuses on the aspects of TAG and fatty acid synthesis pathways in L. starkeyi. We also present a quite effective strategy to obtain L. starkeyi mutants accumulating a larger amount of lipids and having a higher lipid production rate than the wild-type strain. The analysis of these mutants exhibiting high lipid production has led to the identification of important genes for achieving highly effective lipid production and thus advanced improvement in lipid production. Herein, our aim was to provide useful information to advance the development of L. starkeyi as a cost-effective TAG feedstock.Key Points
•Oleaginous yeast Lipomyces starkeyi is an excellent sustainable lipid producer.
•Efficient isolation of lipid-enriched L. starkeyi mutants depends on the low density of lipids.
•Increased acyl-CoA synthesis pathway is important for improving lipid productivity.
... Interestingly, absence of ACL in most of the non-oleaginous microorganisms has been found to be responsible for the synthesis of triacylglycerols as shown in Fig. 2b [88]. Furthermore, the fatty acid profile of oleaginous yeast is dependent on provided culture conditions as environment stress or physical stress [92,93]. Oleaginous yeast usually accumulates high lipid content in its cellular compartment in N-limited condition [94,95], while Gill et al., reported that Candida 107 can accumulate more lipid in phosphate-limited condition corresponding to high C/P molar ratio [96]. ...
Over the last decade, there has been a huge upsurge of interest in sustainable production of biomass-based biofuels to fulfill the existing energy demand and simultaneously reducing the environmental deterioration. Earlier, vegetable oils and animal fats were utilized for biodiesel production, but due to food crisis and environmental sustainability, renewable sources such as neutral lipid derived from microbes are gaining much attention for budding biodiesel industries. Among various types of microorganisms, oleaginous yeasts are more promising feedstock to accomplish the current demand of biodiesel production and utilize a large number of cost-effective renewable substrates for their growth and lipid accumulation. However, biodiesel obtained from oleaginous yeasts have certain restrictions regarding their commercial utilization due to their unstable fuel properties such as oxidative stability, cetane number, viscosity and low-temperature performance etc. Numerous articles have been published in the public domain describing the fatty acid profiles of oleaginous yeast as feedstock for biodiesel production. However, the evaluation of quality parameters of biodiesel obtained from oleaginous yeasts is still in infancy. Although there is a huge disparity in a number of papers published for biodiesel production yet the reporting performance on diesel engines need to be verified in details. In this review article, attempt has been made to assess the important biofuel properties on the basis of the fatty acid profile of oleaginous yeast. Thus this evaluation would provide a guideline to the biodiesel producer to improve the production plans related to feedstocks for oleaginous yeast, culture conditions and biodiesel blending.
... It was shown that the overall biodiesel production cost was economically competitive (US$ 0.76/l) to that of vegetable biodiesel (US$ 0.81/l) and the yield of biodiesel is 6.3-fold higher (4172 l/ha of cultivated sugarcane) than that obtained from yield of soybean biodiesel (661 l/ha of cultivated soybean) [18]. The nature of fatty acids synthesized by oleaginous yeast relies on the nutritional content of the provided medium and culture conditions [19,20]. There are several new strategies already known to improve the lipid production in oleaginous yeasts such as strain improvement through genetic engineering, optimization of the culture conditions (temperature, pH, agitation rate), and cultivation in a modified bioreactor. ...
In this study oleaginous yeast, Rhodosporidium kratochvilovae HIMPA1 grown in glucose synthetic medium containing different nitrogen (1 g/l and 0.1 g/l) and phosphorus (0.05 g/l and 0.1 g/l) limited conditions. Among various N and P-limited conditions, the highest lipid content (60.34 ± 0.69%) obtained under synchronized limitation of N and P (0.1 g/l N and 0.05 g/l P). Live fluorescent cell imaging of yeast cells after BODIPY505-515nm staining endorses the results of triacylglycerol (TAG) accumulation in lipid droplets. The cells grown in synchronized limitation of N and P exhibited boosted cell size (6.76 ± 0.39 µm) and lipid droplet size (5.62 ± 0.28 µm). Under synchronized limitation of N and P, supersized irregular shaped lipid droplets (LD) coalesced to form big lobules in the cellular compartment of oleaginous yeast having 87.14% enhanced TAG accumulation as depicted by TLC. Synchronized nutrient limitation diverts the CDP-DG pathway of phospholipids synthesis towards de novo TAG synthesis. The maximum increment of oleic acid (C18:1) was reported in synchronized limitation of N and P that improve the biodiesel properties like oxidative stability, viscosity, cetane number and cold filter plugging point.
... The de-novo synthesis of lipids involves both acetyl-Co A and malonyl-CoA adding carbon to form 14 and 16 long fatty acid chains. The fatty acids profile of oleaginous yeast depends on the provided culture condition [62,63]. It has been reported that under nitrogen-limited condition oleaginous yeast accumulates more lipid (>70% of their CDW) than the condition with access nitrogen [64,65]. ...
Current research scenario has been shifted to biomass based bio fuels due to increasing global energy crisis and greenhouse effects. Biodiesel is renewable and alternative to the petroleum diesel, well- defined as a blend of fatty acid alkyl esters. It is biologically decompos able, non-toxic, non-flammable, expedient and free from aromatic contents. Sustainability of biodiesel is major concerned regarding its availability and inherent properties that make it cleaner fuel for polluted cities. It is produced by a chemical reaction known as trans esterification in which fatty acids regardless of its origin (oil derived from plants, animals, and waste cooking oil) react with methanol in the presence of suitable catalysts (homogeneous/heterogeneous). Using vegetable oils for biodiesel production is no more economical and sustainable due to direct competition with human food sources. Microbial oils are noble substitutes, which have similar fatty acid pro files with vegetable oils. Among various microorganisms, oleaginous yeast is considered as microscopic bio-factory for oil generation that can be used as feedstock for biodiesel production. The utilization of oleaginous yeast for biodiesel production has many advantages over other non-conventional renewable sources like higher lipid produc tivity in terms of g/l/day than the algae and plants, easier scale-up of upstream and downstream processing, less affected by the season and climatic variation to grow.
... There are no data on accumulation of neutral lipids in clostridia cells during aceto-butylic (ABE) fermentation. Perhaps this lack happened because it is generally thought that the accumulation of neutral lipids is stimulated in the presence of oxygen [7] and thus this process should be restricted under anaerobiosis. However, lipids serve not only as structural components, but also as a source of energy [8] and therefore the accumulation of neutral lipids is of great importance under anaerobic conditions too. ...
The aim of the study was to evaluate changes in the portion of polar and neutral lipids in the cells of Clostridium during their cultivation in the presence of butanol. Four natural isolates of Clostridium genus were studied with flow cytometry approaches. Under the optimal culture conditions, the polar lipids prevailed over neutral ones in bacterial cells; the content of neutral lipids doubled in spores of these microorganisms, while the content of polar ones was reduced. Strains No 1 and No 2 were able to grow at 1% butanol in the medium, and the strain No 4 was at 1.5%. When cultivated in the presence of different concentrations of butanol, the bacterial strains did not differ in such cytomorphological features as granularity and cell size. The quantitative content of polar and neutral lipids in the presence of butanol varied depending on the content of butanol in the medium, however this effect had a strain-specific character and did not show a correlation with the resistance of these bacteria to butanol. So, the content of polar and neutral lipids varied depending on butanol content in the medium. However this effect was strain-specific independently of resistance of these bacteria to butanol. The use of bacterial biomass as a source of lipids for the production of biofuels requires further optimization of the process to increase the content of the neutral lipid fraction in bacterial cells.
... Three phosphatidate phosphatase (PAP) isoenzymes are required to convert PA into Diacylglycerol (DAG) through dephosphorylation reaction (Fig. 4). The last steps of denovo lipogenesis in oleaginous yeasts are varied in different strains and show dependency on acetyl-Co-A and binds with DAG backbone by diacylglycerol acyltransferases that finally form TAG [98]. It has been reported that in Rhodotorula glutinis this reaction is performed by a 35 kDa acyl-acyl carrier protein synthetase [99]. ...
... In the de-novo synthesis of lipids, both acetyl-Co-A and malonyl-Co-A are added together to form fatty acid chains between 14 and 16 carbons long (Fig. 4). Moreover, the fatty acid profile of oleaginous yeast is totally dependent on provided culture conditions; it can be either environmental stress or physical stress conditions [98,99]. The fatty acid profile of oleaginous yeasts varies in different species, however, the main fatty acids produced by these yeasts are myristic acid (C 14:0 ), palmitic acid (C 16:0 ), palmitoleic acid (C 16:1 ), stearic acid (C 18:0 ), oleic acid (C 18:1 ), linoleic acid (C 18:2 ) and linolenic acid (C 18:3 ). ...
Biodiesel, as one of the best alternative fuels, has a number of advantages over petro diesel, such as originating from a renewable and domestic feedstock which reduces the net production cost of biodiesel. In the recent years, biodiesel has received increasing interest due to energy crisis worldwide along with exhausting reserves and the shortage of oil supplies. The major problem behind the use of vegetable oil for biodiesel production is sustainability because it directly competes with human food. To combat this problem, the other renewable sources have been developed as microbial oils have similarity to vegetable oils and extensively used for biodiesel production. Oleaginous yeasts have recently been suggested as microscopic biofactories and alternative lipid producer to vegetable oil for a more sustainable biodiesel industry. It is a potential novel technology where non-edible lignocellulosic biomasses are exploited as raw materials for biodiesel production from oleaginous yeasts which drop net greenhouse gas emissions by substituting the practice of fossil fuels and would convey benefits to rural economies and national energy security. The usage of oleaginous yeasts have many advantages over other renewable sources like faster growth rate, shorter life cycle, easier scale-up, with no effects from the season and climate variation, and can serve as the excellent oil accumulating renewable feedstocks which are non-competitive to food resources and do not require arable land. Non-edible lignocellulosic biomass, consists of three different types of natural polymers, namely cellulose, hemicellulose, and lignin, is the most abundant renewable bioresource in the biosphere. The production of fermentable sugars from hydrolysates of various non-edible lignocellulosic biomass, either by physical, chemical or enzymatic hydrolysis has been utilized as feedstock in bioethanol or biodiesel production, extensively. During hydrolysis generation of non-carbohydrate compounds, such as 5- hydroxymethylfurfural (HMF), furfural acetic acid and phenolic compounds have various effects on the growth of microorganisms, their metabolism, as well as on final products, presenting a key challenge in the biological conversion of biomasses.
