Microbial Lipid Production Research Articles

Treatment of sewage sludge with γ‐ray irradiation for volatile fatty acids and lipid production

AbstractThe production of value‐added products from sewage sludge is considered to be one of the solutions for the sustainable management of sludge in wastewater treatment plants (WWTPs). The presence of carbon, nitrogen, and phosphorus sources has made the sewage sludge of WWTPs a valuable and low‐cost substrate for the production of fermentative products. In the current study, a process was developed for microbial lipid production from two types of sewage sludge from a WWTP in northern Isfahan: anaerobic digester inlet sludge (DIS) and anaerobic digester outlet sludge (DOS). This process was based on the release of volatile fatty acids (VFAs) from the sludge by combinations of γ‐ray irradiation, anaerobic digestion, and acidogenic fermentation followed by utilization of VFAs in a microbial process by the oleaginous yeast Cryptococcus aureus UIMC65. After γ‐ray irradiation, the acidogenic fermentation of the treated sludge released 72% of the organic matter content of the sludge with acidification efficiency of 12% leading to 0.516 g L−1 VFAs. The oleaginous fermentation of the released VFAs for 7 days was accompanied by production of 1.58 g L−1 dry cell biomass with 40% lipid content. The results of this study indicate that the sewage sludge from urban WWTP has the potential to be used for the production of microbial lipids.

Integrated lipidomic and transcriptomic analyses provide insights into the positive effect of hydrogen peroxide treatment on lipid synthesis in oleaginous red yeast Sporobolomyces pararoseus

Microbial lipids are a group of promising renewable sources that are highly demanded by the food, feed, pharmaceutical, and biofuel industries. Sporobolomyces pararoseus is a well-studied oleaginous yeast that is usually considered superior for the industrial production of microbial lipids over other conventional microorganisms. The objective of this study was to investigate the specific effect of hydrogen peroxide treatment on the biosynthesis of microbial lipids in S. pararoseus via lipidomics and transcriptomics technologies. These results showed that hydrogen peroxide treatment significantly enhanced lipid production in S. pararoseus CJR, especially the triacylglycerols. The up-regulation of several key lipogenic genes might be one of the main reasons for this enhancement. Integrative analysis of the lipidome and transcriptome revealed that some key protein-encoding genes and transcription factors might play a crucial regulatory role in lipid biosynthesis under hydrogen peroxide stress. Together, the results presented herein not only provided a feasible fermentation process for boosting the yield of certain lipids but also deepened our understanding of the lipid biosynthesis in S. pararoseus CJR. This could serve as a molecular cornerstone for enhancing their yield through genetic engineering and then further facilitate commercial applications of microbial lipids synthesized by S. pararoseus in more industrial sectors.

Biorefinery of waste activated sludge: Nutrient recovery and microbial lipid production by Yarrowia lipolytica

The rising generation of waste activated sludge (WAS) demands a fundamental shift towards resource reuse and recovery. The conventional methodologies used to manage this by-product derived from wastewater treatment plants are increasingly constrained due to stringent regulatory measures aimed at mitigating its adverse impacts on the environment and public health. Therefore, this work evaluated a promising strategy for the efficient management of WAS, transforming it into a valuable renewable source to produce high-value-added compounds, such as lipids and a slow-release fertilizer (struvite). Wet oxidation (WO) was identified as a suitable technique for solubilising WAS while generating short-chain fatty acids (primarily acetic acid). It was found that conducting WO at 200 °C for 120 min resulted in a 65% reduction of the total suspended solids (TSS) content and 87% of the volatile suspended solids (VSS) content. Additionally, under these conditions, 4440 ± 105 mg/L and 593 ± 21 mg/L of acetic and propionic acid were obtained, respectively, which were assimilated by Yarrowia lipolytica to produce biolipids. Furthermore, the rupture of WAS flocs also led to the solubilisation of 980 ± 8 mg/L of ammonium. During the struvite precipitation stage, a NH4:PO4:Mg ratio of 1:1.5:1.5 was found to be the most effective for removing soluble ammonium (97.4 ± 0.8%), resulting in a high-purity struvite formation, and enhancing the carbon/nitrogen (C/N) ratio of the oxidised WAS from 3 to 105. This improvement in the C/N ratio raised the lipid content from 36 ± 1% to 49 ± 1% during the cultivation of Y. lipolytica. The application of the sequencing batch culture strategy further increased lipid content to 59 ± 1%, with 6.0 ± 0.3 g/L as the final concentration after the fifth cycle. The lipids produced, mainly monounsaturated fatty acids with 40% of oleic acid, offer potential as biodiesel feedstock. This lipid composition led to biodiesel properties, including cetane number, iodine value, kinematic viscosity and density that met international standards. Therefore, this research presents a promising alternative not only for WAS management but also for harnessing valuable resources, thereby establishing a basis for large-scale studies.

Enzymatic Activity of Fungi for Hydrolysis of Wheat Bran and Cultivation of Oleaginous Yeasts

Sustainable alternatives to petrochemical raw materials in oleochemical, laundry detergent and personal care industry need to be implemented. Presently, palm oil is the predominant cost-efficient option. While it is a renewable source, it has negative environmental and socioeconomic implications. Therefore, the request for ecologically certified and palm oil-free cleaning agents and household care products is rapidly growing, supported by concepts of waste-free biorefinery. Oleaginous yeasts are currently the most promising source for microbial lipid production. Additionally, wheat bran is a cereal milling by-product, which is available in high quantities and provides an excellent feedstock. Enzymatically generated wheat bran hydrolysate provides an excellent microbial cultivation medium for the sustainable production of high value biological additives. Indeed, wheat bran consists predominantly of lignocellulose, and therefore of cellulose, hemicellulose and lignin, which can be hydrolyzed by established enzyme systems. Currently, such enzymatic systems are mainly obtained for the market from genetically modified organisms (GMO). This represents a problem because GMO products or process components cannot be included in eco-certified household care formulations. Therefore, innovative GMO-free biotechnological processes need to be implemented, as well as the isolation of novel GMO-free hydrolase enzyme systems. Fungal strains are an interesting source for the efficient screening and isolation GMO-free hydrolases (see figure).This contribution is part of a project, which aims to use a holistic biotechnological approach to convert mill residues into customized specialty ingredients of eco-certified detergents. The project focuses on three main tasks:investigation of a microbial group of eight Ascomycete fungi,production of enzymes for hydrolysis of wheat bran, anduse of the resulting biomass hydrolysate to cultivate oleaginous yeasts.Hydrolase producing fungal strains were cultivated on different substrates to investigate their ability to generate specific enzyme systems capable of hydrolyzing wheat bran. The activity of the enzymes was qualitatively and quantitatively characterized to determine the optimal strains for the degradation of wheat bran and suited to implement a large-scale process. Supernatants of different fungal strains cultivations were tested in the hydrolysis step to compare the hydrolysis performances of differently active enzyme mixes. The biomass hydrolysate was used to cultivate lipid generating yeasts to investigate their ability to grow on the microbial cultivation medium.

Food waste recycling to Yarrowia biomass due to combined hydrothermal carbonization and biological treatment

Food waste (FW) to value-added application represents a demanding opportunity in the circular economy. As one of the approaches, FW hydrothermal carbonization (HTC) delivers an aqueous phase (HTC-AP), which would be suitable when applied to microbial growth and lipid production. In this context, this current work explored HTC-AP from FW obtained through HTC (temperatures 200 to 260 °C) for microbial growth of 14 different Yarrowia species. Among these strains, Y. lipolytica, Y. keelungensis, Y. porcina, and Y. galii showed the ability to utilize HTC-AP. In HTC from 200 °C high optical density (OD600) reaching above 1.2 for the 4 species was observed. An increase in the temperature by 20 °C declined the growth of Y. lipolytica, Y. porcina, and Y. galii by 17%. However, Y. keelungensis showed good growth regardless of the HTC temperature. Further, the lipid produced better at higher biomass 240 °C compared to 260 °C during the HTC. Further, Y. yakushimensis showed the highest growth rate among all the analyzed media (0.12 – for medium 2 (0.45 NH4+ and 200 °C). Although the composition of HTC-AP is very diverse and often toxic, some analyzed yeast species can use the contained compounds as a carbon source for biomass and lipid biosynthesis. The presented possibilities are a very good starting point for developing processes on a larger scale.

Production of docosahexaenoic acid by a novel isolated Aurantiochytrium sp. 6-2 using fermented defatted soybean as a nitrogen source for sustainable fish feed development.

We focused on the production of docosahexaenoic acid (DHA)-containing microbial lipids by Aurantiochytrium sp. using of defatted soybean (DS) as a nitrogen source. Defatted soybean is a plant biomass that could provide a sustainable supply at a low cost. Results showed that Aurantiochytrium sp. could not directly assimilate the DS as a nitrogen source but could grow well in a medium containing DS fermented with rice malt. When cultivated in a fermented DS (FDS) medium, Aurantiochytrium sp. showed vigorous growth with the addition of sufficient sulfate and chloride ions as inorganic nutrients without seawater salt. A novel isolated Aurantiochytrium sp. 6-2 showed 15.8±3.4g/L DHA productivity (in 54.8±12.1g/L total fatty acid production) in 1L of the FDS medium. Therefore, DHA produced by Aurantiochytrium sp. using FDS enables a stable and sustainable DHA supply and could be an alternative source of natural DHA derived from fish oil.

Scale-up of microbial lipid and bioethanol production from oilcane

Microbial oils are a sustainable biomass-derived substitute for liquid fuels and vegetable oils. Oilcane, an engineered sugarcane with superior feedstock characteristics for biodiesel production, is a promising candidate for bioconversion. This study describes the processing of oilcane stems into juice and hydrothermally pretreated lignocellulosic hydrolysate and their valorization to ethanol and microbial oil using Saccharomyces cerevisiae and engineered Rhodosporidium toruloides strains, respectively. A bioethanol titer of 106 g/L was obtained from S. cerevisiae grown on oilcane juice in a 3 L fermenter, and a lipid titer of 8.8 g/L was obtained from R. toruloides grown on oilcane hydrolysate in a 75 L fermenter. Oil was extracted from the R. toruloides cells using supercritical CO2, and the observed fatty acid profile was consistent with previous studies on this strain. These results demonstrate the feasibility of pilot-scale lipid production from oilcane hydrolysate as part of an integrated bioconversion strategy.

Pilot-scale processing of Miscanthus x giganteus for recovery of anthocyanins integrated with production of microbial lipids and lignin-rich residue

Chemical-free hydrothermal pretreatment of Miscanthus x giganteus (Mxg) at the lab scale using high liquid-to-solid ratios resulted in the recovery of anthocyanins and enhanced enzymatic digestibility of residual biomass. In this study, the process is scaled up by using a continuous hydrothermal pretreatment reactor operated at a low liquid-to-solid ratio (50 % w/w solids) as an important step towards commercialization. Anthocyanin yield was 70 % w/w at the pilot scale (50 kg of Mxg), compared to the 94 % w/w yield achieved at the lab scale (0.5 g of Mxg). The pretreated biomass was subsequently refined mechanically using a disc mill to increase the accessibility of cellulose by cellulases. Enzymatic saccharification of the pretreated and disc-milled residue yielded 238 g/L sugar concentration by operating in fed-batch mode at 50 % w/v solids content. Two strains of Rhodosporidium toruloides were evaluated for converting the hydrolysate sugars into microbial lipids, and strain Y-6987 had the highest lipid titer (11.0 g/L). Further, the residue left after enzymatic saccharification was determined to be enriched 1.7-fold in the lignin content. This lignin-rich residue has value as a feedstock for the production of sustainable aviation fuel precursors and other high-value lignin-based chemicals. Hence the proposed biorefinery based on Mxg creates an opportunity for generating revenue from multiple high-value products. As the demand for biofuels and biobased products is rising, the biorefinery products from Mxg would create a niche in the industrial sector.

New trends in microbial lipid-based biorefinery for fermentative bioenergy production from lignocellulosic biomass

Using oleaginous microbial lipid-based biorefinery from lignocellulosic biomass (LCB) to produce fermentative bioenergy (i.e., biodiesel) represents an innovative second-generation fuel production technology. These lipids are predominantly intracellular triglycerides that accumulate through the metabolism of sugars in fermentation following pretreatment and enzymatic hydrolysis of LCB. This review investigates the recent advances in the microbial lipid production from LCB, focusing on the factors influencing the lead microbial lipid producers, different pretreatment methods (i.e., physical, chemical, biological, and combined pretreatment), enzymatic hydrolysis approaches, novel bioprocessing strategies (i.e., microbes-specific and fermentation model specific), and engineering techniques of the oleaginous microbes (i.e., genetic and metabolic alterations). The study demonstrates that oleaginous yeasts can synthesize significantly higher quantities of lipids when incorporated into the system, known as separated hydrolysis and lipid production, following various combined pretreatment methods. Interestingly, CRISPR is found to be the most suitable way of engineering microbes genetically and metabolically for increased lipid synthesis. The study also explores economically viable strategies for fermentative lipid production, addressing associated challenges, and outlines future directions, including comprehensive techno-economic and life cycle assessments. This review offers invaluable insights into microbial lipid production from LCB, highlighting the potential for significant technological and environmental enhancements through ongoing research and development efforts.

Evaluating oleaginous yeasts for enhanced microbial lipid production using sweetwater as a sustainable feedstock

BackgroundYeasts exhibit promising potential for the microbial conversion of crude glycerol, owing to their versatility in delivering a wide range of value-added products, particularly lipids. Sweetwater, a methanol-free by-product of the fat splitting process, has emerged as a promising alternative feedstock for the microbial utilization of crude glycerol. To further optimize sweetwater utilization, we compared the growth and lipid production capabilities of 21 oleaginous yeast strains under different conditions with various glycerol concentrations, sweetwater types and pH.ResultsWe found that nutrient limitation and the unique carbon composition of sweetwater boosted significant lipid accumulation in several strains, in particular Rhodosporidium toruloides NRRL Y-6987. Subsequently, to decipher the underlying mechanism, the transcriptomic changes of R. toruloides NRRL Y-6987 were further analyzed, indicating potential sugars and oligopeptides in sweetwater supporting growth and lipid accumulation as well as exogenous fatty acid uptake leading to the enhanced lipid accumulation.ConclusionOur comparative study successfully demonstrated sweetwater as a cost-effective feedstock while identifying R. toluroides NRRL Y-6987 as a highly promising microbial oil producer. Furthermore, we also suggested potential sweetwater type and strain engineering targets that could potentially enhance microbial lipid production.Graphical abstract

Biomass and microbial lipids production by Yarrowia lipolytica W29 from eucalyptus bark hydrolysate

Using lignocellulosic biomass hydrolysate as a renewable and abundant feedstock for microbial lipids production is a sustainable and economic high-potential approach. This study investigated the potential of the oleaginous yeast Yarrowia lipolytica to produce lipids-rich biomass from eucalyptus bark hydrolysate (EBH) obtained by enzymatic hydrolysis of the biomass pretreated by steam explosion. The effect of EBH concentration (undiluted and 1:3 v/v diluted) and medium supplementation (CSL and KH2PO4) was evaluated in Erlenmeyer flasks and lab-scale stirred tank bioreactor, respectively. Additionally, the effect of volumetric oxygen transfer coefficient (kLa) and mode of operation (batch and two-stage repeated batch) was also assessed in the bioreactor. Under the best experimental conditions (undiluted EBH, 2 g⋅L−1 CSL, 1.8 g⋅L−1 (NH4)2SO4, and kLa of 66 h−1), Y. lipolytica W29 grown in batch cultures accumulated 26 % (w/w) of intracellular lipids, corresponding to 5.6 g⋅L−1 of concentration. Lipids of Y. lipolytica were highly unsaturated and mainly composed of oleic acid (48 %), followed by palmitoleic (20 %), linoleic (17 %) and palmitic acids (14 %). This composition of Y. lipolytica lipids suggests their potential use as feedstock for biodiesel (a renewable biofuel). This work demonstrated the robust features of Y. lipolytica W29 as a potential lipids production platform to implement lignocellulose-based biorefineries.

Exploring the use of hexadecane by Yarrowia lipolytica: Effect of dissolved oxygen and medium supplementation

This work aimed to evaluate the effect of medium composition and volumetric oxygen transfer coefficient (kLa) on Y. lipolytica growth and production of microbial lipids and enzymes from hexadecane. In the stirred tank bioreactor, increasing kLa from 11 h−1 to 132 h−1 improved the hexadecane assimilation rate, biomass concentration, and lipids synthesis (0.90 g·L−1). A cost-effective hexadecane-based medium supplemented with corn steep liquor and a low amount of ammonium sulfate boosted lipids production up to 2.1 g·L−1, composed of palmitic, palmitoleic, oleic, and linoleic acids. The unsaturated/saturated fraction was dependent on the C/N ratio. Lipids of Y. lipolytica CBS 2075 are promising feedstock for animal feed, food additives, or the biodiesel industry. Simultaneous synthesis of extracellular lipase and protease from hexadecane was observed, which is a new feature that was not previously reported. The highest enzyme activity was obtained at the highest C/N ratio conditions. These results open new perspectives on the application of Y. lipolytica-based cultures for the biotransformation of hexadecane-polluted streams into valuable compounds, fulfilling an interesting strategy towards the circular economy concept.

Simultaneous enhancement of lignin-derived inhibitor tolerance and lipid accumulation of oleaginous yeast Trichosporon cutaneum by adaptive evolution

Inhibitory compounds should be removed from the pretreated lignocellulose feedstock before fermentative production of microbial lipid by oleaginous yeast. Biodetoxification effectively degrades furan aldehydes and weak organic acids, but is less efficient against complex and various lignin-derived phenolic aldehydes. Residual phenolics in lignocellulose hydrolysates require a tolerant fermentation strain. This study adopted the long-term adaptive evolution combined with centrifugal enrichment in corn stover hydrolysate to simultaneously improve the phenolic inhibitors tolerance and lipid synthesis of Trichosporon cutaneum. The obtained mutant T. cutaneum MS28 showed significant improved performances of phenolic aldehydes tolerance and lipid accumulation. The final cellulosic lipid production of T. cutaneum MS28 utilizing corn stover reached 33.8 ± 0.1 g/L, approximately 6-fold higher than that of the starting strain. Transcriptional analysis suggested that T. cutaneum MS28 had more active lignocellulose-derived sugars metabolism and lipid synthesis shunts. The intracellular contents of lipid synthesis precursors including NADPH and acetyl-CoA increased 1.7–3.0 folds. This adaptive evolution in lignocellulose hydrolysate combined with centrifugal enrichment is an efficient tool to targeted enhancement of inhibitors tolerance and cellulosic lipid production of oleaginous yeast.

Computational assessment of lipid production in Rhodosporidium toruloidesin two-stage and one-stage batch bioprocesses.

Oleaginous yeasts are promising platforms for microbial lipids production as a renewable and sustainable alternative to vegetable oils in biodiesel production. In this paper, a thorough in silico assessment of lipid production in batch cultivation by Rhodosporidium toruloideswas developed. By means of dynamic flux balance analysis, the traditional two-stage bioprocess (TSB) performed by the native strain was contrasted with one-stage bioprocess (OSB) using four designed strains obtained by gene knockout strategies. Lipid titer, yield, content, and productivity were analyzed at different initial C/N ratios as relevant performance indicators used in bioprocesses. By weighting these indicators, a global lipid efficiency metric(GLEM) was defined to consider different scenarios. Under simulated conditions, designed strains for lipid overproduction in OSB outperformed the TSB in terms of lipid title (up to threefold), lipid yield (up to 2.4-fold), lipid content (up to 2.8-fold, with a maximum of 76%), and productivity (up to 1.3-fold), depending on C/N ratios. Using these efficiency parameters and the proposed GLEM, the process of selecting the most suitable candidates for lipid production could be carried out before experimental assays. This methodology holds the potential to be extended to other oleaginous microorganisms and diverse strain design techniques.

Production of Microbial Lipids by Saitozyma podzolica Zwy2-3 Using Corn Straw Hydrolysate, the Analysis of Lipid Composition, and the Prediction of Biodiesel Properties

Production of Microbial Lipids by Saitozyma podzolica Zwy2-3 Using Corn Straw Hydrolysate, the Analysis of Lipid Composition, and the Prediction of Biodiesel Properties

Upstream and downstream processing of essential fatty acids from microbial biomass

Microbial biomass is a promising supply of essential fatty acids (EFAs) for utilization in human and animal nutrition such as fish. EFAs, including polyunsaturated fatty acids (PUFAs), are needed for cell regulation and disease prevention. Oleaginous microorganisms from species like fungi (Cryptococcus, Cunninghamella, and Mortierella), microalgae (Chlorella zofingiensis and Crypthecodinium cohnii), and bacteria (Moritella sp. and Vibrio sp.) can accumulate lipids exceeding 20% of their biomass. Optimizing factors such as nitrogen and carbon sources, cultivation methods, and environmental conditions may improve their lipid production. Efficient lipid extraction methods through mechanical, non-mechanical or chemical methods are essential to obtain EFAs from microbial biomass. Challenges include substrates (carbon and nitrogen sources) cost and downstream processing and overcoming these challenges can provide a sustainable source of EFAs for human and animal nutrition. By advancing metabolic engineering, cultivation techniques, and extraction methods, microbial lipid production holds the potential to offer cost-effective and environmentally friendly EFAs. The utilization of microbial biomass as a source of EFAs can contribute to a healthier future by addressing the limitations of traditional sources and providing a sustainable solution for meeting the increasing demand for EFAs in human and animal diets.

Single-Cell Oil Production by Engineered Ashbya gossypii from Non-Detoxified Lignocellulosic Biomass Hydrolysate

In this work, microbial lipid production from non-detoxified Eucalyptus bark hydrolysate (EBH) with oleaginous xylose-utilizing Ashbya gossypii strains was explored. The best producing strain from a set of engineered strains was identified in synthetic media mimicking the composition of the non-detoxified EBH (SM), the lipid profile was characterized, and yeast extract and corn steep liquor (CSL) were pinpointed as supplements enabling a good balance between lipid accumulation, biomass production, and autolysis by A. gossypii. The potential of the engineered A. gossypii A877 strain to produce lipids was further validated and optimized with minimally processed inhibitor-containing hydrolysate and high sugar concentration, and scaled up in a 2 L bioreactor. Lipid production from non-detoxified EBH supplemented with CSL reached a lipid titer of 1.42 g/L, paving the way for sustainable single-cell oil production within the concept of circular economy and placing lipids as an alternative by-product within microbial biorefineries.

Two-stage process production of microbial lipid by co-fermentation of glucose and N-acetylglucosamine from food wastes with Cryptococcus curvatus

Microbial lipids were produced through a two-stage process with Cryptococcus curvatus by co-fermenting rice and shrimp shells hydrolysates. In the first stage, biomass production of glucose and N-acetylglucosamine was optimized by response surface methodology with the maximum biomass yield (17.60 g/L) under optimum conditions (43.2 g/L mixed sugar concentration, pH 5.8, 200 rpm, and 28 °C). In the second stage, according to a single-factor optimization setting (43.2 g/L sugar mixture solutions, pH 5.5, and shift time of 36 h), lipid titer of 10.08 g/L with content of 55.30 % was achieved. Scaling up to a 5-L bioreactor increased lipid content to 60.07 % with 0.233 g/g yield. When Cryptococcus curvatus was cultured in the blends of rice hydrolysates and shrimp shells hydrolysate, lipid content and yield were 52.25 % and 0.204 g/g. The fatty acid compositions of lipid were similar to those of typical vegetable oils.

Whey and post-frying oil as substrates in the process of microbial lipids obtaining: a value-added product with nutritional benefits

AbstractYarrowia lipolytica has found many biotechnological applications. The species has a number of regulatory mechanisms to maintain cellular homeostasis, enabling biomass growth in complex media. The aim of this study was to evaluate the use of Y. lipolytica yeast as a platform for the simultaneous management of several industrial by-products and the production of microbial lipids with application potential in the chemical and food industries. Batch cultures of KKP 379 strain were conducted in media with post-frying rapeseed oil (PFO) and a by-product of curd cheese production—acid whey. To evaluate the potential of Yarrowia as a nutraceutical, quantitative and qualitative analyses of microbial sterols were carried out along with an assessment of the biomass mineral composition. It was indicated that the composition and content of sterols varied depending on the phase of cell growth in batch culture. During culture in medium with 20% (v/v) whey and 50 g/L PFO, the cellular lipid content reached 39% (w/w). The highest amount of sterols per dry biomass (7.38 mg/g) and cellular lipids (21.08 mg/g) was recorded after 38 h of culture. The dominant was ergosterol 12.10 mg/g (57%). In addition, the composition of carbon and nitrogen sources in the medium affected the content of selected elements in biomass, indicating that substrate modification can be a tool for manipulating the composition of yeast cells. The results of the study showed that the selection of waste substrates is an important factor in regulation of the cellular lipid accumulation efficiency, as well as the content of certain sterols.

State-of-art engineering approaches for ameliorated production of microbial lipid

State-of-art engineering approaches for ameliorated production of microbial lipid