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The pulp and paper industry in Sweden annually produce millions of tons of side-stream materials as black liquor, pulp and paper mill sludge, sulfite liquor and lignosulfonate. These lignocellulosic based materials can be more utilized today in biorefinery processes with microorganisms to produce high-value products as lipids, proteins and biofuels. In this work, we used five side-stream materials as carbon source in fermentation with two oleaginous yeasts, Lipomyces starkeyi and Rhodotorula toruloides. We analyzed lipid production, fatty acid profiles, inhibitors, phenolics, free sugars and metals before and after batch fermentation in 2 L bioreactors. Steam-exploded hardwood media was used as reference as it’s known to be a good substrate for the oleaginous yeast species and after fermentation the lipid yield for R. toruloides was 17 % (w/w) and for L. starkeyi 13 % (w/w). The side-stream materials contained less than 30 % of free sugar compared to the reference media and the total lipid yield was thus less than 2.7 %, (w/w). R. toruloides utilized various sugars during fermentation and L. starkeyi mostly consumed glucose and xylose. Both yeast species also showed a possible ability to utilize various phenolics indicating their metabolic potential to convert depolymerized lignin along with wood-based sugars to lipids and proteins. [ABSTRACT FROM AUTHOR]

Research on enhancing the production of lipids, particularly polyunsaturated fatty acids that are considered important for health, has focused on improvement of metabolism as well as heterologous expression of biosynthetic genes in the oleaginous fungus Aspergillus oryzae. To date, the productivity and production yield of free fatty acids have been enhanced by 10-fold to 90-fold via improvements in metabolism and optimization of culture conditions. Moreover, the productivity of ester-type fatty acids present in triacylglycerols could be enhanced via metabolic improvement. Culturing A. oryzae in a liquid medium supplemented with non-ionic surfactants could also lead to the effective release of free fatty acids from the cells. The current review highlights the advancements made in this field so far and discusses the future outlook for research on lipid production using A. oryzae. I hope the contents are useful for researchers in this field to consider the strategy of increasing production of various valuable metabolites as well as lipids in A. oryzae. [ABSTRACT FROM AUTHOR]

In this study, wastewater from a sewage treatment plant was used to culture the microalga, Verrucodesmus verrucosus. The ability of microalgae to adapt to adverse environments and produce high lipid concentrations was evaluated using different media, including sterile and non-sterile media and a control medium. The analysis showed that the control medium (distilled water sample enriched with fertilizer) removed 80.35% ammonium, 32.71% phosphate, and 83.86% nitrate. The sterile raw effluent removed 78.91% of ammonium, 83.44% of phosphate, and 98.82% of nitrate. The optimal conditions for biomass production were sterile raw wastewater, which produced 383.3 mg L−1 of biomass, 2.5% of total lipids, and an average lipid production of 9.31 mg L−1. Microalgae can grow and consume inorganic nutrients under adverse environmental conditions such as in raw wastewater, which is of great importance because it is a pollutant that negatively affects the environment and society. However, wastewater may represent a viable alternative substrate, allowing the generation of high-value products, such as lipids. Furthermore, the specificity of microalgal morphotypes must be evaluated, because each has specific metabolic plasticity. Verrucodesmus verrucosus is a microalga that has not been evaluated in bioremediation processes of wastewater with and without the presence of biotic factors. Therefore, the present study provides a viable alternative for this biological process, with the potential to store metabolites of interest in the industry. [ABSTRACT FROM AUTHOR]

Microalgae are considered valuable bioresources due to their ability to produce high lipid content and grow under a variety of environmental conditions, making them strong candidates for sustainable biofuel production. However, the economic feasibility of microalgae-based biofuels depends on optimizing growth conditions in large-scale cultivation systems. This study investigates the effects of varying inoculum cell concentrations on the growth, lipid yield, and fatty acid composition of the locally isolated microalga Chlorella sp. SW5 in 2 L and 5 L cultivation systems. The results indicate that higher inoculum concentrations generally enhance biomass accumulation, with the 2 L system achieving the highest growth rate of 0.42 ± 0.01 day⁻1 at an inoculum concentration of 10⁶ cells/mL. Interestingly, while higher inoculum concentrations reduced lipid production in the 2 L system, the 5 L system showed the highest lipid yield (51.23% ± 4.71% dry weight) at the highest inoculum concentration (10⁷ cells/mL). Despite its moderate growth rate, the 5 L culture with a starting inoculum concentration of 10⁷ cells/mL was selected for fatty acid profiling due to its superior lipid yield and productivity. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that the culture produced a total of 93.18% C14-C18 fatty acids, with a profile dominated by saturated (56.33%) and monounsaturated (16.85%) fatty acids, which are essential for biodiesel quality. These findings provide valuable insights into the potential for scaling up microalgal systems for commercial biofuel production, highlighting strategies to optimize productivity. [ABSTRACT FROM AUTHOR]

Oleaginous microorganisms have the unique ability to accumulate lipids that can exceed 20% of their dry cell weight under certain conditions. Despite their potential for efficient lipid production, the metabolic pathways involved are not yet fully understood, largely due to the complexity of intracellular processes and the challenges in phenotypic prediction. This review synthesizes the latest research on the application of Genome‐scale Metabolic Network Models (GSMMs) to study oleaginous microorganisms, including bacteria, cyanobacteria, yeast, microalgae, and fungi, and provides a comprehensive analysis of how GSMMs have been utilized to decipher the metabolic mechanisms behind lipid accumulation and to identify key genes involved in lipid synthesis. The review highlights the role of GSMMs in predicting cellular behavior, optimizing metabolic engineering strategies, and discusses the future directions and potential of GSMMs in enhancing lipid production in microorganisms. This comprehensive overview not only summarizes the current state of research but also identifies gaps and opportunities for further investigation in the field. [ABSTRACT FROM AUTHOR]

Microalgae are microorganisms that in recent years have become protagonists in research because they are potential candidates for use in obtaining compounds of interest such as lipids, which may be transformed into bioenergy compounds like biodiesel. Nannochloropsis oculata is a marine microalga whose main characteristic is its high lipid content. In this work, the effect of salinity intensity on the growth of N. oculata was investigated in the photobioreactor batch cultures incubated with a salinity ranging from 20 to 40 ppt to analyze its growth profile and chlorophyll pigment to obtain dry biomass and biofuel produced as lipid extraction. The results indicated specific growth rate maximum values of 0.343 day-1, obtained at 35 ppt salinity. Chlorophyll pigment increases with salt concentration between 25 and 35 ppt. The total lipid extracted increases considerably at moderate salinities condition (25-35) ppt, the maximum dry biomass harvest and productivity, accomplished after the microalgae cultivation salinity at 30 ppt was 0.623 g/l and 62.3 mg/l respectively. Same applies to the maximum total lipid content and productivity, which was 221 mg/l and 22.1 mg/l. day, respectively. These findings show that a variety of salinities support optimal biomass yield and biochemical composition in N. oculata cultivation. Salinity monitoring is crucial for successful cultivation. Furthermore, the advantages of N. oculata microalga, including its large cell size (facilitating harvest and grazer tolerance) and its salinity resilience, should be considered. [ABSTRACT FROM AUTHOR]

In the present study, the microalga Arthrospira platensis DHR 20 was cultivated in vertical flat-plate photobioreactors (FPBRs) to bioremediate anaerobically digested cattle wastewater (ACWW) and used as a growth substrate. The final objective was to evaluate the properties of the oil extracted from this biomass to determine its potential for biodiesel production. The process was divided into five phases, varying the volume of the applied substrate: 1 L (Phase I), 5 L (Phase II), 10 L (Phase III), 15 L (Phase IV), and 20 L (Phase V). Dry biomass reached a maximum of 5.7 g L−1, and productivity peaked at 0.74 g L−1d−1. The highest rate of CO2 biofixation was 1213.5 mg L−1 day−1, showing good potential for purifying the air. The highest specific maximum growth rate (μmax) and the shortest doubling time (Dt) were found during Phase I. The removal of pollutants and nutrients during the experimental phases ranged from 65.8% to 87.1% for chemical oxygen demand (COD), 82.2% to 85.8% for total organic carbon (TOC), 91% to 99% for phosphate (PO43−), 62.5% to 93% for nitrate (NO3−), 90.4% to 99.7% for ammoniacal nitrogen (NH4+), and 86.5% to 98.5% for total nitrogen (TN). The highest lipid production recorded was 0.172 g L−1 day−1. The average cetane number recorded in Phase IV of 51 suggests that the fuel will ignite efficiently and consistently, providing smooth operation and potentially reducing pollutant emissions. The analysis of fatty acids revealed that the produced biodiesel has the potential to be used as an additive for other low-explosive biocombustibles, representing an innovative and sustainable approach that simultaneously offers bioremediation and carbon sequestration. [ABSTRACT FROM AUTHOR]

Wastewater from different sources with excessive nutrient loading, which is a major contributor to eutrophication, can be a promising medium alternative for microalgae cultivation with effective removal of NH4+-N, PO43--P and organic matter. In this study, three groups of synthetic wastewater (SWW), an ammonium-rich stream (60 to 250 mg L-1 NH4+) containing a specific type of organic matter, such as petroleum effluent (SWW1: 300 mg L-1 glucose and 10 mg L-1 phenol), molasses wastewater (SWW2: 600 mg L-1 glucose), and agro-industrial wastewater (SWW3: no organic matters) were used for growing Chlorella sp. and for investigating its potential for nutrient removal as well as the production of biomass and lipid. The findings showed that Chlorella sp. grown in SWW2 (i.e., the auto/mixotrophic culture with 14 days) served as efficient feedstock for lipid production, and showed the maximum lipid content and yield of 53 % DCW and 188 mg L-1, respectively. Additionally, the maximum removal of 76 % NH4+-N was observed under this condition. Higher removal of NH4+-N with 100 % efficiency was seen in Chlorella sp. under SWW1 and SWW3 conditions. However, under SWW2 the cells had higher NH4+ uptake rate than that under SWW1 and SWW3, resulting in highest biomass productivity in SWW2 grown cells. The spent media after Chlorella sp. cultivation were used for growing the N2-fixing cyanobacterium Fischerella muscicola TISTR 8215 for the production of hydrogen. Among different spent media, F.muscicola TISTR 8215 cultivated in SWW1 spent medium obtained from 7-day Chlorella sp. cultivation had the highest hydrogen production of 200.8 µmol H2 mg-1 chlorophyll a. Overall, the present study employed biorefinery approach using the microalga biomass as feedstock for lipid production with subsequent utilization of spent medium for growing the cyanobacterium for enhanced production of hydrogen. [ABSTRACT FROM AUTHOR]

Research on enhancing the production of lipids, particularly polyunsaturated fatty acids that are considered important for health, has focused on improvement of metabolism as well as heterologous expression of biosynthetic genes in the oleaginous fungus Aspergillus oryzae. To date, the productivity and production yield of free fatty acids have been enhanced by 10-fold to 90-fold via improvements in metabolism and optimization of culture conditions. Moreover, the productivity of ester-type fatty acids present in triacylglycerols could be enhanced via metabolic improvement. Culturing A. oryzae in a liquid medium supplemented with non-ionic surfactants could also lead to the effective release of free fatty acids from the cells. The current review highlights the advancements made in this field so far and discusses the future outlook for research on lipid production using A. oryzae. I hope the contents are useful for researchers in this field to consider the strategy of increasing production of various valuable metabolites as well as lipids in A. oryzae.

Microalgae are considered valuable bioresources due to their ability to produce high lipid content and grow under a variety of environmental conditions, making them strong candidates for sustainable biofuel production. However, the economic feasibility of microalgae-based biofuels depends on optimizing growth conditions in large-scale cultivation systems. This study investigates the effects of varying inoculum cell concentrations on the growth, lipid yield, and fatty acid composition of the locally isolated microalga Chlorella sp. SW5 in 2 L and 5 L cultivation systems. The results indicate that higher inoculum concentrations generally enhance biomass accumulation, with the 2 L system achieving the highest growth rate of 0.42 ± 0.01 day⁻1 at an inoculum concentration of 10⁶ cells/mL. Interestingly, while higher inoculum concentrations reduced lipid production in the 2 L system, the 5 L system showed the highest lipid yield (51.23% ± 4.71% dry weight) at the highest inoculum concentration (10⁷ cells/mL). Despite its moderate growth rate, the 5 L culture with a starting inoculum concentration of 10⁷ cells/mL was selected for fatty acid profiling due to its superior lipid yield and productivity. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that the culture produced a total of 93.18% C14-C18 fatty acids, with a profile dominated by saturated (56.33%) and monounsaturated (16.85%) fatty acids, which are essential for biodiesel quality. These findings provide valuable insights into the potential for scaling up microalgal systems for commercial biofuel production, highlighting strategies to optimize productivity.

Microalgal lipids hold significant potential for the production of biodiesel and dietary supplements. To enhance their cost-effectiveness and commercial competitiveness, it is imperative to improve microalgal lipid productivity. Metabolic engineering that targets the key enzymes of the fatty acid synthesis pathway, along with transcription factor engineering, are effective strategies for improving lipid productivity in microalgae. This review provides a summary of the advancements made in the past 5 years in engineering the fatty acid biosynthetic pathway in eukaryotic microalgae. Furthermore, this review offers insights into transcriptional regulatory mechanisms and transcription factor engineering aimed at enhancing lipid production in eukaryotic microalgae. Finally, the review discusses the challenges and future perspectives associated with utilizing microalgae for the efficient production of lipids. [ABSTRACT FROM AUTHOR]

A continuous stirred tank bioreactor (CSTB) with cell recycling combined with ceramic membrane technology and inoculated with Rhodococcus opacus PD630 was employed to treat petroleum refinery wastewater for simultaneous chemical oxygen demand (COD) removal and lipid production from the retentate obtained during wastewater treatment. In the present study, the COD removal efficiency (CODRE) (%) and lipid concentration (g/L) were predicted using two artificial intelligence models, i.e., an artificial neural network (ANN) and a neuro-fuzzy neural network (NF-NN) with a network topology of 6-25-2 being the best for NF-NN. The results revealed the superiority of NF-NN over ANN in terms of determination coefficient (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE). Three learning algorithms were tested with NF-NN; among them, the Bayesian regularization backpropagation (BR-BP) outperformed others. The sensitivity analysis revealed that, if solid retention time and biomass concentrations were maintained between 35 and 75 h and 3.0 g/L and 3.5 g/L, respectively, high CODRE (93%) and lipid concentration (2.8 g/L) could be obtained consistently. [ABSTRACT FROM AUTHOR]

Present dependence on fossil sources for meeting energy demand globally is unsustainable as a result of non‐renewable and depleting supplies. Therefore, this study focuses on production and characterization of biodiesel by Chlorococcum littorale (Chlorococcum sp.) isolated from fish pond in Owode fish farm, Nigeria. Biomass concentration, lipid extraction and quantification were determined by filtration, solvent extraction and gravimetric methods. Extracted lipid was transesterified to diesel through process catalyzed by concentrated tetraoxosulphate (VI) acid. The constituents of fats in biodiesel produced were examined through chromatography of gas and spectroscopy of mass. Model prediction was used to assess physical and chemical parameters of biodiesel. The data gathered was subjected to statistical analysis. Chlorococcum sp. had biomass concentration (4.42 ± 0.02 g/L), Lipid content (67.75% and biodiesel yield (96.33%). Biodiesel had 48.3%, 29.20%, and 22.50% fatty acids that are saturated, monounsaturated and polyunsaturated, respectively. The biodiesel produced has the kinematic viscosity (2.74 mm2/s at 40°C); point of flash (245°C); point of cloud (7°C); point of pour (−2°C) and density (0.8760 g/cm3). Furthermore, the acidity level (0.44 mgKOH/g), value of saponification (186.49 mgKOH/g), value of peroxide (3.25 meq/kg), iodine content (38.27 mgI2/g) as well as the free fatty acid (1.34%), number of cetane (65.78), oxidative resistance (7.33 h), saturated factor of long chain (28.16°C), plugging point of cold filter (35.62°C) and high heating value (43.24°C) fell within required standard by international body. Thus, Chlorococcum sp. is ideal microalgae isolate for the biodiesel production. The biodiesel produced conform satisfactorily with the acceptable global standard. HIGHLIGHTS: Biodiesel exhibited good stability of oxidation and a high number of cetane.Presence of C16 and C18 fatty acids as well as saturated fat.Physicochemical characterization tests for biodiesel produced show that the quality of biodiesel produced was of high standard.Biodiesel produced has properties that met standard by international bodies. [ABSTRACT FROM AUTHOR]

The use of fossil fuels has increasingly become associated with negative influences like detrimental environmental effects. This has made renewables, especially biofuels like biodiesel, a highly attractive substitute for energy generation. The industrial and economic potential of biodiesel—a lipid-based fuel—has increased interest and research into oleaginous microorganisms to synthesise and produce lipids. Effective identification and characterisation of a vast array of oleaginous microorganisms have led them to be employed for their efficient lipogenesis capability and ability to use a wide range of synthetic and non-expensive substrates. However, low lipid production has limited the use of microbially sourced lipids for biodiesel production at the industrial level. Nevertheless, the improvement and engineering of robust strains of these microbes through metabolic engineering have increased their lipid production capacity, leading to commercialising the lipids. This review provides a comprehensive outlook into the identification of different oleaginous microorganisms and their unique characteristics, which makes them highly valuable. An insight into the lipid biosynthesis pathways is provided and the role that several enzymes and regulators play in the metabolism of lipid accumulation. A detailed outlook is provided on the broad range of metabolic engineering approaches with regard to enhanced lipid production in several oleaginous microorganisms. [ABSTRACT FROM AUTHOR]

Currently, microalgae have become a marvelous and resource-friendly alternative source of advantageous bioproducts, such as lipids, carbohydrates, proteins, or other bioactive compounds. Because of the richness of microalgae in these high-value-added metabolites, still, it is an underdeveloped source of sustainable energy and food. There are some hurdles to profitable production, such as culture contamination and costly harvesting techniques. In the current work, a chrysophyte was isolated from dairy wastewater, identified as Poterioochromonas malhamensis based on its morphology and partial 18S rRNA gene sequences. This isolate was used to remediate dairy waste water (DWW) and to obtain neutral lipids (fatty acids) from microalgae. Microalgal growth was optimized by using different concentrations of DWW, supplemented with all the nutritive requirements for better progression and flourishment. Maximum biomass yield 1.478 g L−1 was achieved by optimized cultural conditions (different concentrations of DWW with BBM media). This strain showed high nitrate and phosphate removal efficiency (87.45% and 88.96%), respectively in 15 days. The experimental results highlighted that the lipid content and the chemical oxygen demand (COD) removal were 31.60% and 88.84%, respectively, and the lipid profile of isolated microalga was C16:0, C16:1, C18:0, C18:1, and C18:2 fatty acids. For growth and treatment purposes, 75% DWW with Bold’s Basal Medium (BBM) media showed better results. This is the first report of DWW treatment using the microalga Poterioochromonas malhamensis, as far as we are aware. Its cultivation prevented the spread of pollution of freshwater sources, remedied the DWW, and generated important lipids for industry.

Microalgal lipids hold significant potential for the production of biodiesel and dietary supplements. To enhance their cost-effectiveness and commercial competitiveness, it is imperative to improve microalgal lipid productivity. Metabolic engineering that targets the key enzymes of the fatty acid synthesis pathway, along with transcription factor engineering, are effective strategies for improving lipid productivity in microalgae. This review provides a summary of the advancements made in the past 5 years in engineering the fatty acid biosynthetic pathway in eukaryotic microalgae. Furthermore, this review offers insights into transcriptional regulatory mechanisms and transcription factor engineering aimed at enhancing lipid production in eukaryotic microalgae. Finally, the review discusses the challenges and future perspectives associated with utilizing microalgae for the efficient production of lipids.

Summary: Central metabolism produces amino and fatty acids for protein and lipids that establish seed value. Biosynthesis of storage reserves occurs in multiple organelles that exchange central intermediates including two essential metabolites, malate, and pyruvate that are linked by malic enzyme. Malic enzyme can be active in multiple subcellular compartments, partitioning carbon and reducing equivalents for anabolic and catabolic requirements. Prior studies based on isotopic labeling and steady‐state metabolic flux analyses indicated malic enzyme provides carbon for fatty acid biosynthesis in plants, though genetic evidence confirming this role is lacking. We hypothesized that increasing malic enzyme flux would alter carbon partitioning and result in increased lipid levels in soybeans.Homozygous transgenic soybean plants expressing Arabidopsis malic enzyme alleles, targeting the translational products to plastid or outside the plastid during seed development, were verified by transcript and enzyme activity analyses, organelle proteomics, and transient expression assays. Protein, oil, central metabolites, cofactors, and acyl‐acyl carrier protein (ACPs) levels were quantified overdevelopment.Amino and fatty acid levels were altered resulting in an increase in lipids by 0.5–2% of seed biomass (i.e. 2–9% change in oil).Subcellular targeting of a single gene product in central metabolism impacts carbon and reducing equivalent partitioning for seed storage reserves in soybeans. See also the Commentary on this article by Schwender, 239: 1539–1541. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mucor circinelloides has the ability to use a wide range of carbon sources to accumulate lipids. The different carbon sources have significantly influenced the total lipids through different metabolic pathways in oleaginous organisms. In the present study, the effects of exogenous oil (soybean oil) at different concentrations as an alternative carbon source on its fungal growth and lipid accumulation were investigated without changing fermentation culture conditions and the original C/N ratio, while using 100% glucose as a control. Total lipids and their fatty acid composition were determined by gas chromatography (GC). Moreover, the expression levels of desaturases genes involved in fatty acid biosynthesis were investigated in the studied strains using real-time fluorescence quantitative PCR. The results showed that a concentration of 35 g/L of glucose mixed with 24.3 g/L of soybean oil were the optimal carbon sources with constant carbon to nitrogen ratio. The biomass, lipid content and lipid yield of M. circinelloides grown in this medium increased rapidly in the early stage of fermentation, and the growth trend gradually slowed down in the late stage of fermentation, decreasing slightly after 72 h of fermentation. It was found that the highest biomass, total lipids, and lipid yields were significantly increased at 19.60 g/L, 42.62%, and 8.35 g/L (33.15%, 23.8%, and 65.10%), respectively. In contrast, the control group (those cultured on glucose as a single carbon source) was only 14.72 g/L, 34.41%, and 5.06 g/L, respectively. The critical step was in which α-linolenic acid (ALA) was stored from the exogenous oil in fungal cells supplying enough soybean oil with mixed substrates for fatty acids synthesis. The overexpression of the △12-desaturase gene in WJ11 significantly (P

Abstract Background Microalgae, with their high adaptability to various stress conditions and rapid growth, are considered excellent biomass resources for lipid production and biodiesel feedstocks. However, lipid yield and productivity of the natural strains are common bottlenecks in their large-scale use for lipid production, which can be overcome by evolving new strains using conventional and advanced mutagenic techniques. It is challenging to generate microalgae strains capable of high lipid synthesis through natural selection. As a result, random mutagenesis is currently considered a viable option in many scenarios. The objective of this study was to explore atmospheric and room temperature plasma (ARTP) as a random mutagenesis technique to obtain high lipid-accumulating mutants of a green microalga for improved biodiesel production. Results A green microalgal species was isolated from the Chinese Yellow Sea and identified as Parachlorella kessleri (OM758328). The isolated microalga was subsequently mutated by ARTP to obtain high lipid-accumulating mutants. Based on the growth rate and lipid content, 5 mutants (named M1, M2, M4, M5, and M8) were selected from 15 pre-selected mutants. These five mutants varied in their growth rate from 0.33 to 0.68 day−1, with the lipid content varying between 0.25 g/L in M2 to 0.30 g/L in M8 at 10th day of cultivation. Among the mutants, M8 showed the maximum biomass productivity (0.046 g/L/day) and lipid productivity (20.19 mg/L/day), which were 75% and 44% higher than the wild strain, respectively. The triglyceride (TAG) content of M8 was found to be 0.56 g/L at 16th day of cultivation, which was 1.77-fold higher than that of the wild strain. Furthermore, M8 had the highest saturated fatty acids (C16-18) with the lowermost polyunsaturated fatty acid content, which are favorable properties of a biodiesel feedstock according to international standards. Conclusion The mutant strain of P. kessleri developed by the ARTP technique exhibited significant improvements in biomass productivity, lipid content, and biodiesel quality. Therefore, the biomass of this mutant microalga could be a potential feedstock for biodiesel production.

Acne is associated with the excessive production of sebum, a complex mixture of lipids, in the sebaceous glands. The transcription factor Krüppel-like factor 4 (KLF4) plays an important role in skin morphogenesis, but its role in sebum production by sebocytes is not well known. In this study, we investigated the possible action mechanism of KLF4 during calcium-induced lipogenesis in immortalized human sebocytes. Sebocytes were treated with calcium, and lipid production was confirmed by thin-layer chromatography (TLC) and Oil Red O staining. To investigate the effect of KLF4, sebocytes were transduced with the KLF4-overexpressing adenovirus, and then lipid production was evaluated. Calcium treatment resulted in increased sebum production in terms of squalene synthesis in sebocytes. In addition, calcium increased the expression of lipogenic regulators such as sterol-regulatory element binding protein 1 (SREBP1), sterol-regulatory element binding protein 2 (SREBP2), and stearoyl-CoA desaturase (SCD). Similarly, the expression of KLF4 was increased by calcium in sebocytes. To investigate the effect of KLF4, we overexpressed KLF4 in sebocytes using recombinant adenovirus. As a result, KLF4 overexpression increased the expression of SREBP1, SREBP2, and SCD. Parallel to this result, lipid production was also increased by KLF4 overexpression. Chromatin immunoprecipitation revealed the binding of KLF4 to the SREBP1 promoter, indicating that KLF4 may directly regulate the expression of lipogenic regulators. These results suggest that KLF4 is a novel regulator of lipid production in sebocytes. • Calcium promotes differentiation of sebocytes and contributes to lipid production. • Calcium regulates the expression of KLF4 during differentiation of sebocytes. • The transcription factor KLF4 regulates the expression of SREBP1 to facilitate lipid formation. [ABSTRACT FROM AUTHOR]

Microalgae provide a potential alternative for high-value products. Integrating microalgae into the landfill leachate valorization process gives the opportunity to save water sources for biomass production. The aim of this study is to investigate the ability of landfill leachate to support microalgal biomass production and to explore how leachate affects the fatty acid and lipid content of microalgae. The wild "Chlorella sp." strain was isolated from a Tunisian natural lake and experimented in standard culture medium (Bold) as well as in different rates of landfill leachate. Results revealed that the leachate rate of 10% produced the highest amount of biomass (2.6 g L−1), which was significantly higher than Bold's medium. The final percentage of lipids recorded was 53% and 78% in Bold's medium and in leachate, respectively. Lipid productivity was stimulated 11 times more than obtained in Bold's medium with 823 mg L−1 d−1 in 10% leachate and 69.6 mg L−1 d−1 for Bold's medium. Characterization of the lipid extract using gas chromatography with a flame ionization detector (GC-FID) showed that around 90% of the total lipid content appeared mainly composed with saturated fatty acids such as palmitic acid (C16:0) and linoleic acid (C18:2) indicating a good quality of biodiesel. The leachate rate of 10% promotes the oleic, linoleic and linolenic acids known as omega 9, 6 and omega 3, respectively, by increasing its production to 10, 37 and 4%, respectively, while it was about only 5, 30 and 2%, respectively, in Bold's culture medium. It could be concluded that the Chlorella strain isolated from natural lake performs as a good tolerant organism to landfill leachate, and its culture in this effluent could be a potential source for lipid and biodiesel production. Using landfill leachate as a culture medium gives the opportunity to save water sources for microalgal biomass production. Growth and lipid production performances of a wild Chlorella sp.microalgae using landfill leachate as a culture medium [ABSTRACT FROM AUTHOR]

Currently, microalgae have become a marvelous and resource-friendly alternative source of advantageous bioproducts, such as lipids, carbohydrates, proteins, or other bioactive compounds. Because of the richness of microalgae in these high-value-added metabolites, still, it is an underdeveloped source of sustainable energy and food. There are some hurdles to profitable production, such as culture contamination and costly harvesting techniques. In the current work, a chrysophyte was isolated from dairy wastewater, identified as Poterioochromonas malhamensis based on its morphology and partial 18S rRNA gene sequences. This isolate was used to remediate dairy wastewater (DWW) and to obtain neutral lipids (fatty acids) from microalgae. Microalgal growth was optimized by using different concentrations of DWW, supplemented with all the nutritive requirements for better progression and flourishment. Maximum biomass yield 1.478 g L−1 was achieved by optimized cultural conditions (different concentrations of DWW with BBM media). This strain showed high nitrate and phosphate removal efficiency (87.45% and 88.96%), respectively in 15 days. The experimental results highlighted that the lipid content and the chemical oxygen demand (COD) removal were 31.60% and 88.84%, respectively and the lipid profile of isolated microalga was C16:0, C16:1, C18:0, C18:1, and C18:2 fatty acids. For growth and treatment purposes, 75% DWW with Bold’s Basal Medium (BBM) media showed better results. This is the first report of DWW treatment using the microalga Poterioochromonas malhamensis, as far as we are aware. Its cultivation prevented the spread of pollution of freshwater sources, remedied the DWW, and generated important lipids for industry. [ABSTRACT FROM AUTHOR]

Low biomass yield and nutrient removal efficiency are problems challenging the employment of microorganisms for wastewater remediation. Starch processing effluent (SPE) was used as a fermentation substrate to co-culture Chlorella vulgaris and Rhodotorula glutinis for biofuel feedstock production. Co-culture options were compared, and the optimal conditions were identified. The result shows that microalgae and yeast should be inoculated simultaneously at the beginning of SPE-based fermentation to achieve high biomass yield and the optimal inoculation ratio, light intensity, and temperature should be 2:1, 150 μmol/m2/s, and 25 °C, respectively. Under the optimal conditions, the lipid yield of microorganisms was 1.81 g/L and the carbon–conversion ratio reached 82.53% while lipid yield and the carbon–conversion ratio in a monoculture fell in the range of 0.79–0.81 g/L and 55.93–62.61%, respectively. Therefore, compared to the monoculture model, the co-fermentation of Chlorella vulgaris and Rhodotorula glutinis in starch processing effluent could convert nutrients to single-cell oil in a more efficient way. It should be noted that with the reduced concentration of residual organic carbon in effluent and the increased carbon–conversion ratio, co-fermentation of microalgae and yeast can be regarded as a promising and applicable strategy for starch processing effluent remediation and low-cost biofuel feedstock production. [ABSTRACT FROM AUTHOR]

Oleic acid is increasingly required in many industries, causing the indiscriminate extension of land for the cultivation of certain agricultural products to extract their oil. The current contribution aimed to cultivate Candida wangnamkhiaoensis (CW) for the production of lipids and determine the profile of fatty acids in these lipids. The lipid yield was compared in the yeast when using glucose or glycerol as the substrate, in both cases being over 24%. The main fatty acids in the oil derived from CW were oleic, palmitic, stearic, and linoleic acid. The fatty acid composition of the oil from CW was very similar to that of avocado oil and resembled that of olive oil and palm oil. The advantages of cultivating CW include its relatively high percentage of oleic acid and the balance of other fatty acids, its capacity to generate lipids in a short time (48–72 h), the controlled environment of production (versus the variability of the cultivation of agricultural products), and the relatively limited surface area required. CW shows potential as an alternative and economical source of oleic acid for the food, drug, cosmetics, lubricant, and biofuel industries, and does not require the alteration of large extensions of land. [ABSTRACT FROM AUTHOR]

Abstract Background Schizochytrium sp. is a heterotrophic, oil-producing microorganism that can efficiently produce lipids. However, the industrial production of bulk chemicals using Schizochytrium sp. is still not economically viable due to high-cost culture medium. Replacing glucose with cheap and renewable lignocellulose is a highly promising approach to reduce production costs, but Schizochytrium sp. cannot efficiently metabolize xylose, a major pentose in lignocellulosic biomass. Results In order to improve the utilization of lignocellulose by Schizochytrium sp., we cloned and functionally characterized the genes encoding enzymes involved in the xylose metabolism. The results showed that the endogenous xylose reductase and xylulose kinase genes possess corresponding functional activities. Additionally, attempts were made to construct a strain of Schizochytrium sp. that can effectively use xylose by using genetic engineering techniques to introduce exogenous xylitol dehydrogenase/xylose isomerase; however, the introduction of heterologous xylitol dehydrogenase did not produce a xylose-utilizing engineered strain, whereas the introduction of xylose isomerase did. The results showed that the engineered strain 308-XI with an exogenous xylose isomerase could consume 8.2 g/L xylose over 60 h of cultivation. Xylose consumption was further elevated to 11.1 g/L when heterologous xylose isomerase and xylulose kinase were overexpressed simultaneously. Furthermore, cultivation of 308-XI-XK(S) using lignocellulosic hydrolysates, which contained glucose and xylose, yielded a 22.4 g/L of dry cell weight and 5.3 g/L of total lipid titer, respectively, representing 42.7 and 30.4% increases compared to the wild type. Conclusion This study shows that engineering of Schizochytrium sp. to efficiently utilize xylose is conducive to improve its utilization of lignocellulose, which can reduce the costs of industrial lipid production.

Sucrose non-fermenting 1 (SNF1) protein kinase plays an important role in the utilization of selective carbon sources and regulation of lipid metabolism. In order to further explore the function of SNF1 in regulating lipid accumulation by responding nutritional signals from non-glucose carbon sources, in the present study, the lipid production and SNF1 transcriptional levels of Mucor circinelloides were analyzed and compared on different carbon sources. The results indicated that M. circinelloides could effectively utilize some secondary metabolic carbon sources of monosaccharides and disaccharides for growth and lipids production, such as fructose, maltose and galactose. Snf-β subunit was associated with the regulation of lipid metabolism in response to nutritional signals from different carbon sources. This is the first report on the transcriptional analysis of SNF1 subunits on different carbons metabolism in oleaginous filamentous fungi. This research has suggested that genetic engineering of SNF1 subunits will alter the lipid production of M. circinelloides from alternative carbon sources. [ABSTRACT FROM AUTHOR]

Lipid accumulating fungi are promising tools as alternative lipid source with different applications. In this study, seven oleaginous fungal strains were isolated from dung samples from the Egyptian ecosystem which later investigated for lipid accumulation, and Mucor racemosus AH1 represented the highest one. Statistical optimization of M. racemosus AH1 for lipid production was carried out using Taguchi design. Accordingly, dry biomass, total lipids, and lipid content were 3.72 gL−1, 1.21 gL−1, and 32.4%, respectively. Fatty acid profile of the produced lipids at different temperatures from 5 to 35 °C was investigated using gas chromatography mass spectroscopy GC–MS. Results revealed that the best temperature range for unsaturated fatty acids production particularly polyunsaturated fatty acids (PUFAs) was between 10 and 20 °C in which unsaturated fatty acids (USFAs) were higher than saturated fatty acids (SFAs); 54.47% and 43.67%, respectively. In conclusion, a promising lipid accumulating and cold-adapted M. racemosus MG547571 are considered as hopeful source of USFAs particularly oleic and linoleic acids which can be recruited for pharmaceutical applications, additionally, the high lipid yield could be exploited for biodiesel production. [ABSTRACT FROM AUTHOR]

The study evaluated the use of Chlorella vulgaris for bioremediating hydroponic wastewater and producing biomass under different cultivation modes and to explore the economic implications of microalgal biofuels. Total nitrogen (TN) removal efficiency was 98.5% in mixotrophic conditions and 96% in heterotrophic conditions, and total phosphorus (TP) was completely removed (>99%) in both cultivation conditions. TN removal was higher for that which was cultivated under the mixotrophic mode of cultivation. The maximum biomass production (1.26 g/L) and biomass productivity (0.1108 g/L/day) were also reported for mixotrophic conditions. Lipid content was slightly higher for that which was cultivated under heterotrophic conditions: 33 wt% on an ash-free dry weight (AFDW) basis. The highest lipid production was obtained under mixotrophic growth (0.341 g/L). Higher net profit was obtained for both mixotrophic and heterotrophic cultivations: 30.6 million $/year for a plant capacity of 3.29 × 104 tone/year and 30.12 million $/year for a plant capacity of 3.17 × 104 tone/year respectively. Sensitivity analysis showed that biodiesel and nutritious supplements from soluble protein have the greatest impact on the process economics regarding mixotrophic cultivation, while biodiesel and feeds from insoluble protein have the largest effect on the process economics regarding heterotrophic and autotrophic cultivations. HIGHLIGHTS C. vulgaris was cultivated in hydroponic wastewater to remove nutrients and to produce lipid and biomass.; C. vulgaris showed higher TN removal efficiency under mixotrophic growth (TN: 98.5%).; Maximum lipid content was reported for heterotrophic growth (33 wt% AFDW).; Mixotrophic cultivation showed maximum biomass production (1.26 g/L) and biomass productivity (0.1108 g/L/day).; The best economic benefits were obtained for mixotrophic (net profit: 30.6 million $/year) and heterotrophic (net profit: 30.12 million $/year) cultivations.;

Algae exhibit diverse growth strategies, including phototrophy, osmotrophy, and phagotrophy. While phototrophic and osmotrophic growths have been extensively studied, phagotrophic growth remains relatively unexplored. This research delves into the phagotrophic growth of Ochromonas danica on bacteria, evaluating its potential for wastewater and waste sludge treatment. The study reveals that O. danica was able to grow on bacteria without light or additional nutrients, achieving a doubling time of 3.5–3.9 hours and converting 41–45 % of bacterial organic matter into algal biomass. The resultant O. danica cells were lipid-rich, containing 35–46 % lipids by dry weight. The efficiency of O. danica in treating waste sludge was highlighted, achieving a 43 % reduction in organic matter within 36 hours, outperforming conventional aerobic digestion. The study also highlights the potential of O. danica in wastewater treatment. An approach was developed to reclaim organic matter from wastewater through a two-stage process, in which bacteria were first grown on wastewater organic matter and then the grown bacteria were fed to O. danica for growth. Results show that a total of 78.2 % of the initial wastewater organic matter was removed through this approach and 27.3 % of the removed organic matter was converted into lipid-rich algal biomass. The findings underscore the potential of phagotrophic growth for waste treatment and lipid production. The simplicity of the phagotrophic process, independent of light or complex nutrient supplementation, positions it as a promising strategy for industrial applications in waste sludge and wastewater treatment. • The growth of the algae species Ochromonas danica on bacteria was investigated. • O. danica can rapidly grow on bacteria without light. • O. danica can achieve high biomass and lipid yields. • O. danica 's bacterial feeding allows reclaiming organics from waste sludge. • O. danica possesses the potential for sustainable organic waste treatment. [ABSTRACT FROM AUTHOR]

Bioenergy production from algae has gained significant attention due to its potential as a sustainable and renewable energy source. This research investigates the optimization of bioenergy production by focusing on bioreactor design to enhance the efficiency of algal biomass growth and lipid extraction. The study involves analyzing key bioreactor parameters such as light intensity, nutrient concentration, pH levels, and carbon dioxide (CO₂) supply. Experimental results demonstrated a 25% increase in lipid production through optimized conditions, showing promising improvements in biofuel yield. The findings of this research provide valuable insights into the potential scalability of algae-based bioenergy systems.

This article is a Commentary on Morley et al. (2023), 239: 1834–1851. [ABSTRACT FROM AUTHOR]

The interest in microorganisms to produce microbial lipids at large-scale processes has increased during the last decades. Rhodosporidium toruloides-1588 could be an efficient option for its ability to simultaneously utilize five- and six-carbon sugars. Nevertheless, one of the most important characteristics that any strain needs to be considered or used at an industrial scale is its capacity to grow in substrates with high sugar concentrations. In this study, the effect of high sugar concentrations and the effect of ammonium sulfate were tested on R. toruloides-1588 and its capacity to grow and accumulate lipids using undetoxified wood hydrolysates. Batch fermentations showed a catabolic repression effect on R. toruloides-1588 growth at sugar concentrations of 120 g/L. The maximum lipid accumulation was 8.2 g/L with palmitic, stearic, oleic, linoleic, and lignoceric acids as predominant fatty acids in the produced lipids. Furthermore, R. toruloides-1588 was able to utilize up to 80% of the total xylose content. Additionally, this study is the first to report the effect of using high xylose concentrations on the growth, sugar utilization, and lipid accumulation by R. toruloides-1588. [ABSTRACT FROM AUTHOR]

In the present study, Synechococcus elongatus and Anabaena, two cyanobacterial species were cultured using different media conditions such as ASN III, modified ASN III, BG-11, and BBM for the enrichment of biomass and lipid productivity. The experimental result clearly shows that BG 11 was the efficient and cost-effective medium for both the isolated cyanobacterial species such as Synechococcus elongatus and Anabaena. The influence of organic carbon sources on biomass and lipid productivity of the selected cyanobacterial species were studied when cultivated in a BG-11 medium using different organic carbon sources such as sucrose, glucose, sodium acetate and glycerol under mixotrophic conditions. Based on the experimental results, the isolated cyanobacterial strain Synechococcus elongatus and Anabaena showed an enriching effect on lipid production under mixotrophic conditions, but whereas Synechococcus elongatus showed a significant effect three times greater lipid productivity compared with Anabaena cyanobacterial strain, by the addition of glycerol as a supplement to the culture media. [ABSTRACT FROM AUTHOR]

Lipid extraction from microbial and microalgae biomass requires the separation of oil-rich cells from the production media. This downstream procedure represents a major bottleneck in biodiesel production, increasing the cost of the final product. Flocculation is a rapid and cheap system for removing solid particles from a suspension. This natural characteristic is displayed by some microorganisms due to the presence of lectin-like proteins (called flocculins/adhesins) in the cell wall. In this work, we showed, for the first time, that the heterologous expression of the adhesin Cfl1p endows the oleaginous species Cutaneotrichosporon oleaginosus with the capacity of cell flocculation. We used Helm's test to demonstrate that the acquisition of this trait allows for reducing the time required for the separation of lipid-rich cells from liquid culture by centrifugation without altering the productivity. This improves the lipid production process remarkably by providing a more efficient downstream. [ABSTRACT FROM AUTHOR]

POME is an excellent cultivation medium for the production of microalgae because it includes high macro and micronutrients. Nevertheless, microalga cultivation is laborious to maintain under outdoor condition. The aim of this reseasch was to evaluate the potency of co-cultivation strategy to improve growth and lipid production of mixed algae when growing on POME under dynamic outdoor condition. Cultivation was done in outdoor condition by comparing synthetic medium and POME medium, and optimizing the enviromental and nutritional conditions by using Box-behnken response surface methodology (RSM). Results showed that high growth rate (0.35/d) and lipid (40%) were achieved when 75% POME fraction, 30 PSU salinity, and 450 mg/L urea were used. The increasing POME fraction and urea addition enhanced SFA formation to MUFA and PUFA in the fatty acid profiles. We conclude that co-cultivation strategy on POME could promote growth rate and lipid production of mixed algae under outdoor condition. [ABSTRACT FROM AUTHOR]

An effective prototype of photobioreactor namely hollow fiber membrane bioreactor is employed to produce algal biomass for biofuel production. The effect of two-stage cultivation system on the biomass productivity and lipid production is studied using freshwater green microalga Tetradesmus obliquus MT188616.1. The hybrid system combines exponential biomass production in hollow fiber membrane photobioreactor (HFMPBr) and a coordinated high-lipid stimulation phase in nitrogen-deprived medium by the shake flask method. This work is proposed to examine the usefulness of HFMPBr module to enhance the microalgal growth rate through the effective mass transfer by standardizing the culture medium re-circulation flow rates (5 – 45 mL min−1) through the hollow fiber membranes. Cultivation is carried out at continuous mode in HFMPBr containing polysulfone fabricated membranes at fixed light intensity of 50 µmol m−2 s−1 and temperature at 28 °C. Biomass productivity and specific growth rate obtained are 0.44 g L−1d−1 and 1.61 µ d−1 with a lipid yield of 0.1 g L− 1. The key operating parameter i.e., liquid flow rate is optimized based on biomass production. The highest biomass concentration is produced at the flow rate of 45 mL min−1. The results showed that HFMPBr module is a better choice for the algal-cultivation to obtain higher biomass yield. The effect of two-stage cultivation system on the growth rate, biomass productivity, and lipid yield was studied in freshwater green microalga Tetradesmus obliquus MT188616.1. The hybrid system combines exponential biomass production in hollow fiber membrane photobioreactor (HFMPBr) and a coordinated high-lipid stimulation phase in nitrogen deprived medium by the shake flask method. The algal cultivation was carried out at continuous mode in HFMPBr containing polysulfone fabricated membranes at fixed light intensity of 50 µmol m−2 s−1 and temperature at 28 °C. Biomass productivity and specific growth rate obtained were 0.44 g L−1d−1 and 1.61 µ d−1 with a lipid yield of 0.1 g L− 1. The key operating parameter i.e., liquid flow rate was optimized based on biomass production. The highest biomass concentration was produced at the highest flow rate of 45 mL min−1, whereas the lowest biomass was at the lowest flow rate of 5 mL min−1. The results showed that HFMPBr module was a better choice for the cultivation of Tetradesmus obliquus MT188616.1 to obtain higher biomass yield. [Display omitted] • Integrated HFMPBr and shake flask approach to attain higher lipid yield of algae. • Optimized salt medium flow rate in HFMPBr for continuous algal growth. • Attained efficient delivery of nutrients via membranes for algal growth and waste removal by maintaining optimal flow rate. • Achieved close to 0.44 gL-1day-1 biomass productivity under 45 mL min-1 flow rate during 10 h light – 14 h dark photoperiod. [ABSTRACT FROM AUTHOR]

Background: Microalgae, with their high adaptability to various stress conditions and rapid growth, are considered excellent biomass resources for lipid production and biodiesel feedstocks. However, lipid yield and productivity of the natural strains are common bottlenecks in their large-scale use for lipid production, which can be overcome by evolving new strains using conventional and advanced mutagenic techniques. It is challenging to generate microalgae strains capable of high lipid synthesis through natural selection. As a result, random mutagenesis is currently considered a viable option in many scenarios. The objective of this study was to explore atmospheric and room temperature plasma (ARTP) as a random mutagenesis technique to obtain high lipid-accumulating mutants of a green microalga for improved biodiesel production. Results: A green microalgal species was isolated from the Chinese Yellow Sea and identified as Parachlorella kessleri (OM758328). The isolated microalga was subsequently mutated by ARTP to obtain high lipid-accumulating mutants. Based on the growth rate and lipid content, 5 mutants (named M1, M2, M4, M5, and M8) were selected from 15 pre-selected mutants. These five mutants varied in their growth rate from 0.33 to 0.68 day-1, with the lipid content varying between 0.25 g/L in M2 to 0.30 g/L in M8 at 10th day of cultivation. Among the mutants, M8 showed the maximum biomass productivity (0.046 g/L/day) and lipid productivity (20.19 mg/L/day), which were 75% and 44% higher than the wild strain, respectively. The triglyceride (TAG) content of M8 was found to be 0.56 g/L at 16th day of cultivation, which was 1.77-fold higher than that of the wild strain. Furthermore, M8 had the highest saturated fatty acids (C16-18) with the lowermost polyunsaturated fatty acid content, which are favorable properties of a biodiesel feedstock according to international standards. Conclusion: The mutant strain of P. kessleri developed by the ARTP technique exhibited significant improvements in biomass productivity, lipid content, and biodiesel quality. Therefore, the biomass of this mutant microalga could be a potential feedstock for biodiesel production. [ABSTRACT FROM AUTHOR]