Microbial Lipid Research Articles

Maximising biotransformation of pine needles to microbial lipids using Lipomyces starkeyi MTCC 1400T

Pine needles are relatively less explored lignocellulosic forest waste which can be saccharified to fermentable sugars and be used in subsequent conversion to biofuels. Microbial lipids were produced from pine needles hydrolysate and recovered lipid liquor. Ultrasound assisted pretreatment increased the cellulose content by 20.679%, 27.17%, 32.21%, and 35.61% when treated for 60 min at varying NaOH concentrations (1–4%). The 4-feed batch sachharification was performed to investigate the effect of increasing substrate loadings and fixed initial concentration (5% w/v) and yielded maximum increase of 70.23% in reducing sugars. The pine needle hydrolysate yielded 19.581 g/L total lipids, 35.888 g/L biomass concentration and lipid concentration at 67.46% g/g. Simultaneously, at equimolar ratios of HCl and liquor resulted in highest yields for total lipids (6.92 g/L) and traces of inhibitors. The fatty acids distribution and biodiesel properties revealed a similar biodiesel quality to that of palm oil. Findings from this study facilitate the complete utilisation of pine needles for microbial lipid production to resolve forest fires, and in keeping view of climate, fuels and inorganic resources towards developing a circular bioeconomy.

Mastering targeted genome engineering of GC-rich oleaginous yeast for tailored plant oil alternatives for the food and chemical sector

BackgroundSustainable production of triglycerides for various applications is a major focus of microbial factories. Oleaginous yeast species have been targeted for commercial production of microbial oils. Among all the oleaginous yeasts examined in a previous comparative study, Cutaneotrichosporon oleaginosus showed the highest lipid productivity. Moreover, a new lipid production process for C. oleaginosus with minimal waste generation and energy consumption resulted in the highest lipid productivity in the history of oleaginous yeasts. However, productivity and product diversity are restricted because of the genetic intractability of this yeast. To date, successful targeted genetic engineering of C. oleaginosus has not yet been reported.ResultsThe targeted gene editing was successfully carried out in C. oleaginosus using CRISPR/Cas system. A tailored enzyme system isolated to degrade the C. oleaginosus cell wall enabled the isolation of viable spheroplasts that are amenable to in-cell delivery of nucleic acids and proteins. The employment of both Cas9 protein and Cas mRNA was effective in obtaining strains with URA5 knockout that did not exhibit growth in the absence of uracil. Subsequently, we successfully created several strains with enhanced lipid yield (54% increase compared to that in wild type) or modified fatty acid profiles comparable with those of cocoa butter or sunflower oil compositions.ConclusionThis study establishes the first targeted engineering technique for C. oleaginosus using the CRISPR/Cas system. The current study creates the foundation for flexible and targeted strain optimizations towards building a robust platform for sustainable microbial lipid production. Moreover, the genetic transformation of eukaryotic microbial cells using Cas9 mRNA was successfully achieved.

Study of Gelatin and Peppermint Oil Nanoemulsion Coating Against Food-Borne Pathogens, as Well as Its Effect on Shrimp Quality and Preservation

ABSTRACT Shrimps are perishable food that can degrade quickly. The effects of a gelatin-based nontoxic antimicrobial compound combined with a peppermint oil nanoemulsion on the quality and shelf life of shrimp during storage were examined. The prepared nanoemulsion has satisfactory physical characteristics like size (115 ± 3.7 nm), polydispersity index (0.632), ζ-potential (−24.76 mV), and whiteness index (86.19). The nanoemulsion has antibacterial and antibiofilm activities in vitro against two important food-borne pathogens, Escherichia coli O157:H7 and Staphylococcus aureus. Nanoemulsion coating could be an excellent choice for preservation of shrimp as it reduces the overall microbial load, protein oxidation, melanosis, lipid oxidation, and pH of shrimp.

Withania somnifera fruit extract is effective in controlling microbial growth and lipid oxidation and improves the functional value of cheese

Withania somnifera is a plant well known for its antioxidant, antimicrobial and medicinal properties and has been widely used for these benefits. W. somnifera fruit extract was used to improve the functional value and storage stability of cheese using kalari, a popular Himalayan cheese, as a food-model system. Different levels (0.0–0.7%) of the extract were used for preparing the cheese and an optimum level of 0.5% (T0.5) was found. The cheese samples (T0.5 and control) were evaluated for various storage-stability parameters during 4 weeks of refrigerated storage (4 ± 1 °C). The functional value of the product (T0.5) was evaluated in oxidative-stress-induced rats in 4 weeks feeding trial. The addition of the extract (T0.5) significantly (P < 0.05) improved the lipid-oxidative and microbial-stability of the treated samples and also improved sensory quality at the end of the storage period. Inclusion of the extract-enriched cheese in the rats’ feed ameliorated the impact of oxidative stress on the Wistar rats and showed a significant decrease in liver marker enzymes, lipid-peroxidase activity and relative liver and spleen weights whereas a significant increase was observed in endogenous antioxidant enzymes levels and body weight. Thus, the addition of the extract improved the storage stability and functionality of the cheese.

High-energy diet modify rumen microbial composition and microbial energy metabolism pattern in fattening sheep

Higher dietary energy is often used to achieve better animal performance in mutton sheep production. Notably, changing the diet formula affects rumen fermentation and the microbiota of ruminants. In this study, we investigated the effect of dietary energy on rumen fermentation and ruminal microbiota in fattening sheep. Fifteen 2-month-old white-headed Suffolk sheep (♂) × Hu sheep (♀) crossbred lambs were randomly divided into three treatments based on the dietary energy of the feeds fed: 8.67 MJ/kg (Low energy (LE); n = 5), 10.38 MJ/kg (standard energy (CON); n = 5), and 12.31 MJ/kg (high energy (HE); n = 5) groups. After 70 days of feeding, sheep were slaughtered and the ruminal fluids were collected and analyzed to determine fermentation parameters. Microbiota was determined using metagenomics sequencing. Notably, the microbial cell protein (MCP) and butyric acid concentrations were significantly high in the HE group. Metagenomic sequencing revealed that ACE and Chao indexes of the HE group were significantly decreased. Four genera among the major classified taxa across all the kingdoms differed in relative abundance in the three dietary energy levels. The relative abundances of Prevotella_brevis, Succiniclasticum_ruminis, Prevotellace-ae_bacterium, and Lachnospiraceae_bacterium were significantly correlated with rumen fermentation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis further revealed that a high-energy diet increased lipid metabolism of microbiota. The Carbohydrate Active enzymes (CAZy) gene, which participates in energy metabolism, was upregulated, while genes regulating plant cell wall degradation were downregulated in the HE group. These results suggest that a high-energy diet had minimal influence on the rumen fermentation pattern but altered the composition of the rumen microbiota, enhancing microbial lipid metabolism and limiting crude fiber metabolism. The findings of this study provide scientific evidence of the effect of dietary energy on ruminant fermentation and fattening sheep production.

Integrated Multi-Cohort Analysis of the Parkinson's Disease Gut Metagenome.

The gut microbiome is altered in several neurologic disorders, including Parkinson's disease (PD). The aim is to profile the fecal gut metagenome in PD for alterations in microbial composition, taxon abundance, metabolic pathways, and microbial gene products, and their relationship with disease progression. Shotgun metagenomic sequencing was conducted on 244 stool donors from two independent cohorts in the United States, including individuals with PD (n=48, n=47, respectively), environmental household controls (HC, n=29, n=30), and community population controls (PC, n=41, n=49). Microbial features consistently altered in PD compared to HC and PC subjects were identified. Data were cross-referenced to public metagenomic data sets from two previous studies in Germany and China to determine generalizable microbiome features. We find several significantly altered taxa between PD and controls within the two cohorts sequenced in this study. Analysis across global cohorts returns consistent changes only in Intestinimonas butyriciproducens. Pathway enrichment analysis reveals disruptions in microbial carbohydrate and lipid metabolism and increased amino acid and nucleotide metabolism in PD. Global gene-level signatures indicate an increased response to oxidative stress, decreased cellular growth and microbial motility, and disrupted intercommunity signaling. A metagenomic meta-analysis of PD shows consistent and novel alterations in functional metabolic potential and microbial gene abundance across four independent studies from three continents. These data reveal that stereotypic changes in the functional potential of the gut microbiome are a consistent feature of PD, highlighting potential diagnostic and therapeutic avenues for future research. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Biotechnology process for microbial lipid synthesis from enzymatic hydrolysate of pre-treated sugarcane bagasse for potential bio-oil production

Sugarcane bagasse is a lignocellulosic biomass waste produced from sugar and alcohol production. The aim of this study was to produce cellular lipids from sugarcane bagasse with a biotechnology process using microbial enzymes and lipid-accumulating yeast. Sugarcane bagasse, pre-treated with a steam explosion method, was subjected to enzymatic hydrolysis by a separate hydrolysis and fermentation (SHF) system, using crude enzymes from a new strain of Trichoderma SG2 (T. SG2) with or without supplementation with a commercial enzyme (Cellic CTec2). The mixture of both enzymes produced substantial amounts of sugar from pretreated sugarcane bagasse. In a multistage SHF process, in the second stage (21 + 21 h), a total of 26.92 g L−1 of sugar was converted. In another stage-wise process (21 + 21+21 h) of hydrolysis of residual biomass, 26.23 g L−1 of sugar was recorded; thus maximizing the production of fermentable sugars from bagasse. The cultivation of Rhodotorula sp. R1 in sugarcane bagasse enzymatic hydrolysate (BH) for lipid production was evaluated. The enrichment of the hydrolysate with d-glucose, Y-yeast extract, and P-peptone (BH + P20D20/N0.93) and (BH + Y10D20/N0.2) produced 7.69% and 10.50% of lipids, respectively. Similar to vegetable oils and other yeasts, the lipids accumulated by Rhodotorula R1 contain mainly elaidic acid, palmitic acid, stearic acid, linoleic acid, and a lower percentage of other fatty acids, indicating a suitable composition for biodiesel production.

Microbial lipid production from soybean hulls using Lipomyces starkeyi LPB53 in a circular economy

Soybean hulls are lignocellulosic residuesgeneratedinthe industrial processing of soybean, representing about 5 % of the mass of the whole bean. This by-product isan importantsource of polymers suchas cellulose(34 %) and hemicellulose (11 %),which could bevalorizedvia biotechnology to improvethe economic returnof the oilseed chain. In the present work,soybean hulls were evaluated as a carbon sourcefor biolipid productionbyLipomycesstarkeyi LPB 53. Initially the hulls were treated physicochemically and enzymatically to obtain fermentable sugars. Subsequently, biomass growth was evaluated using different nitrogen sources andthe lipid production was optimized, reaching a maximum cell biomass concentration of 26.5 g/L with 42.5 % of lipids. Around 65 % of the xylose content was consumed.The obtained oil wasmajorlycomposed of oleic, palmitic, palmitoleic, linoleic and stearic fatty acids in a proportion of 54 %, 32 %, 4 %, 3 % and 2 %, respectively.

Oleaginous yeasts for biochemicals, biofuels and food from lignocellulose-hydrolysate and crude glycerol.

Microbial lipids produced from lignocellulose and crude glycerol (CG) can serve as sustainable alternatives to vegetable oils, whose production is, in many cases, accompanied by monocultures, land use changes or rain forest clearings. Our projects aim to understand the physiology of microbial lipid production by oleaginous yeasts, optimise the production and establish novel applications of microbial lipid compounds. We have established methods for fermentation and intracellular lipid quantification. Following the kinetics of lipid accumulation in different strains, we found high variability in lipid formation even between very closely related oleaginous yeast strains on both, wheat straw hydrolysate and CG. For example, on complete wheat straw hydrolysate, we saw that one Rhodotorula glutinis strain, when starting assimilatingD-xylosealso assimilated the accumulated lipids, while a Rhodotorula babjevae strain could accumulate lipids onD-xylose.Two strains (Rhodotorula toruloides CBS 14 and R. glutinis CBS 3044) were found to be the best out of 27 tested to accumulate lipids on CG. Interestingly, the presence of hemicellulose hydrolysate stimulated glycerol assimilation in both strains. Apart from microbial oil, R. toruloides also produces carotenoids. The first attempts of extraction using the classical acetone-based method showed that β-carotene is the major carotenoid. However, there are indications that there are also substantial amounts of torulene and torularhodin, which have a very high potential as antioxidants.

Microbial membrane lipid adaptations to high hydrostatic pressure in the marine environment.

The deep-sea is characterized by extreme conditions, such as high hydrostatic pressure (HHP) and near-freezing temperature. Piezophiles, microorganisms adapted to high pressure, have developed key strategies to maintain the integrity of their lipid membrane at these conditions. The abundance of specific membrane lipids, such as those containing unsaturated and branched-chain fatty acids, rises with increasing HHP. Nevertheless, this strategy is not universal among piezophiles, highlighting the need to further understand the effects of HHP on microbial lipid membranes. Challenges in the study of lipid membrane adaptations by piezophiles also involve methodological developments, cross-adaptation studies, and insight into slow-growing piezophiles. Moreover, the effects of HHP on piezophiles are often difficult to disentangle from effects caused by low temperature that are often characteristic of the deep sea. Here, we review the knowledge of membrane lipid adaptation strategies of piezophiles, and put it into the perspective of marine systems, highlighting the future challenges of research studying the effects of HHP on the microbial lipid composition.

Application of sodium diacetate, potassium lactate and calcium lactate as a microbial decontaminant during processing and storage of the traditional meatballs (rista)

The traditional meat products undergo microbial spoilage and lipid oxidation like other meat products because of their suitability as a medium for microbial growth, which in turn affect safety, quality and shelf life. In the case of traditional meat products like rista, ghostabha, kebab and several other products prepared in Kashmiri wazwan, organic acids or their salts have not been used to date. The present study was therefore aimed to evaluate the effect of different organic acid salts and storage conditions on various quality parameters of traditional meat products. Sodium diacetate (0.25%), potassium lactate (2.5%) and calcium lactate (2.5%) were used in three batches of traditional meat products. Sodium diacetate (SDA) treated samples showed lower total plate count (TPC) under refrigerated storage as compared to ambient storage. The SDA-treated sample retained the lowest value for TBARS (1.9 mg MDA/kg) and free fatty acid (3.2%) on the 15th day of refrigerated storage. Significantly (P ≤ 0.05) higher values for L*, a* and b* were maintained by SDA treated samples as compared to control, potassium lactate (PL) and calcium lactate (CL) treated samples under refrigeration conditions throughout the storage period. Organic acid treatment improved the quality attributes of the meat product during the storage period. The use of organic acids as a preservative in these products will help in reducing the use of synthetic agents. Further increase in the shelf life of traditional meat products by application of organic acids will help in their commercialization, marketing and round the year availability.Graphical

Diversity investigation of cultivable yeasts associated with honeycombs and identification of a novel Rhodotorula toruloides strain with the robust concomitant production of lipid and carotenoid

Oleaginous yeasts-derived microbial lipids provide a promising alternative feedstock for the biodiesel industry. However, hyperosmotic stress caused by high sugar concentration during fermentation significantly prevents high cell density and productivity. Isolation of new robust osmophilic oleaginous species from specific environment possibly resolves this issue to some extent. In this study, the cultivable yeast composition of honeycombs was investigated. Totally, 11 species of honeycomb-associated cultivable yeast were identified and characterized. Among them, an osmophilic yeast strain, designated as Rhodotorula toruloides C23 was featured with excellent lipogenic and carotenogenic capacity and remarkable cell growth using glucose, xylose or glycerol as feedstock, with simultaneous production of 24.41 g/L of lipids and 15.50 mg/L of carotenoids from 120 g/L glucose in 6.7-L fermentation. Comparative transcriptomic analysis showed that C23 had evolved a dedicated molecular regulation mechanism to maintain their high simultaneous accumulation of intracellular lipids and carotenoids and cell growth under high sugar concentration.

Antibacterial, Antioxidant, and in silico NADPH Oxidase Inhibition Studies of Essential Oils of Lavandula dentata against Foodborne Pathogens.

Food is always subjected to microbial infection and lipid peroxidation, which frequently leads to serious food intoxications. In the present study, essential oils (EOs) extracted from Lavandula dentata Moroccan species and its major component (linalool) were chemically characterized and their antioxidant potential and antibacterial properties against foodborne pathogenic bacteria were examined. EOs phytochemical profile was carried out using gas chromatography-mass spectrometry analysis (GC-MS). The antioxidant potential was evaluated, in vitro, by use of the β-carotene discoloration assay and in silico vs. NADPH oxidase enzymatic complex as an antioxidant marker. The antibacterial proprieties were assessed by use of minimal inhibitory concentration (MIC) and disc diffusion methods, against Gram (-) bacteria (Pseudomonas aeruginosa, Salmonella enterica, and Escherichia coli) and Gram (+) bacteria (Bacillus subtilis and Staphylococcus aureus). Linalool (49.71%) was the major component among the eighteen components identified in Lavandula dentate EO, followed by camphor (14.36%) and borneol (8.21%). The studied EO and linalool compounds showed important antioxidant activity through the β-carotene discoloration test with IC50 values of 35.72 ± 1.21 mg/mL and 30.32 ± 1.23 mg/mL, respectively. Among all the analyzed compounds of lavender EOs, thymol, carvacrol, and α-terpineol were the most active compounds against NADPH oxidase with a glide score of -6.483, -6.17, and -4.728 kcal/mol, respectively. 2D and 3D views showed the formation of hydrogen bonds between the most active compounds and the active site of NADPH oxidase. The antibacterial data showed a significant activity of Lavandula dentata essences against tested foodborne pathogenic bacteria, especially against S. aureus and B. subtilis. Linalool proved active toward the same bacteria and had closer activity to that of lavender essential oil. In light of the obtained findings, the essential oil of Lavandula dentata Moroccan species can be used in the packaging sector as a promising natural food conservative to limit lipid oxidation and treat foodborne infections.

From crude glycerol and volatile fatty acids to biodiesel and other bioproducts using Yarrowia lipolytica NCYC 2904 as a cell factory

Biodiesel production using microbial lipids derived from low-cost feedstocks could provide a sustainable alternative for the replacement of conventional fossil fuels.

Yeast Lipid Produced through Glycerol Conversions and Its Use for Enzymatic Synthesis of Amino Acid-Based Biosurfactants

The aim of the present work was to obtain microbial lipids (single-cell oils and SCOs) from oleaginous yeast cultivated on biodiesel-derived glycerol and subsequently proceed to the enzymatic synthesis of high-value biosurfactant-type molecules in an aqueous medium, with SCOs implicated as acyl donors (ADs). Indeed, the initial screening of five non-conventional oleaginous yeasts revealed that the most important lipid producer was the microorganism Cryptococcus curvatus ATCC 20509. SCO production was optimised according to the nature of the nitrogen source and the initial concentration of glycerol (Glyc0) employed in the medium. Lipids up to 50% w/w in dry cell weight (DCW) (SCOmax = 6.1 g/L) occurred at Glyc0 ≈ 70 g/L (C/N ≈ 80 moles/moles). Thereafter, lipids were recovered and were subsequently used as ADs in the N-acylation reaction catalysed by aminoacylases produced from Streptomyces ambofaciens ATCC 23877 under aqueous conditions, while Candida antarctica lipase B (CALB) was used as a reference enzyme. Aminoacylases revealed excellent activity towards the synthesis of acyl-lysine only when free fatty acids (FAs) were used as the AD, and the rare regioselectivity in the α-amino group, which has a great impact on the preservation of the functional side chains of any amino acids or peptides. Aminoacylases presented higher α-oleoyl-lysine productivity and final titer (8.3 g/L) with hydrolysed SCO than with hydrolysed vegetable oil. The substrate specificity of both enzymes towards the three main FAs found in SCO was studied, and a new parameter was defined, viz., Specificity factor (Sf), which expresses the relative substrate specificity of an enzyme towards a FA present in a FA mixture. The Sf value of aminoacylases was the highest with palmitic acid in all cases tested, ranging from 2.0 to 3.0, while that of CALB was with linoleic acid (0.9-1.5). To the best of our knowledge, this is the first time that a microbial oil has been successfully used as AD for biosurfactant synthesis. This bio-refinery approach illustrates the concept of a state-of-the-art combination of enzyme and microbial technology to produce high-value biosurfactants through environmentally friendly and economically sound processes.

A robust soft sensor based on artificial neural network for monitoring microbial lipid fermentation processes using Yarrowia lipolytica.

Microbial oils produced by Yarrowia lipolytica offer an environmentally friendly and sustainable alternative to petroleum as well as traditional lipids from animals and plants. The accurate measurement of fermentation parameters, including the substrate concentration, dry cell weight, and lipid accumulation, is the foundation of process control, which is indispensable for industrial lipid production. However, it remains a great challenge to measure the complex parameters online during the lipid fermentation process, which is nonlinear, multivariate, and characterized by strong coupling. As a type of AI technology, the artificial neural network model is a powerful tool for handling extremely complex problems, and it can be employed to develop a soft sensor to monitor the microbial lipid fermentation process of Y. lipolytica. In this study, we first analyzed and emphasized the volume of sodium hydroxide and dissolved oxygen concentration as central parameters of the fermentation process. Then, a soft sensor based on a four-input artificial neural network model was developed, in which the input variables were fermentation time, dissolved oxygen concentration, initial glucose concentration, and additional volume of sodium hydroxide. This provides the possibility of online monitoring of dry cell weight, glucose concentration, and lipid production with high accuracy, which can be extended to similar fermentation processes characterized by the addition of bases or acids, as well as changes of the dissolved oxygen concentration.

Crabtree Effect on Rhodosporidium toruloides Using Wood Hydrolysate as a Culture Media

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.

Carbon/nitrogen ratio as a tool to enhance the lipid production in Rhodosporidium toruloides-1588 using C5 and C6 wood hydrolysates

The interest in microbial lipids has recently increased because of their wide use to produce several value-added compounds in the biofuel, pharmaceutical and food industries. Oleaginous yeast such as Rhodosporidium toruloides could be an efficient option because of its ability to consume five-carbon sugars, high lipid accumulation, and tolerance to toxic compounds such as furans, phenolic compounds, and organic acids. The present study aims to investigate the effect of different initial sugar ratios, in combination with different carbon/nitrogen ratios, and the use of dibasic sodium phosphate (Na2HPO4) as an inducer on cell biomass production, sugar consumption, and lipid accumulation by Rhodosporidium toruloides-1588. The investigation showed a maximum lipid accumulation of 5.35 gL-1 (0.28 g of lipids/g of sugar) under the culture conditions of initial glucose: xylose ratio of 1:1, C/N ratio of 70, and Na2HPO4 concentration of 1.05 gL-1. The predominant lipids composition was palmitic, stearic, oleic, and linoleic acids which could be used as a suitable feedstock for biofuel production. Additionally, under the optimal conditions (initial glucose: xylose ratio of 1:1, 1.19 gL-1 of Na2HPO4 and C/N ratio of 70.50) an increase of 10.5% and 7.5% in lipid accumulation was observed, compared with control treatments (glucose and xylose, respectively). In addition, the study shows the ability of R. toruloides-1588 to tolerate inhibitors, a feature that could be a promising alternative to increase the feasibility of the microbial lipid production process using undetoxified wood hydrolysate as a sustainable culture media.

Phosphate limitation as crucial factor to enhance yeast lipid production from short-chain fatty acids.

Microbial lipids for chemical synthesis are commonly obtained from sugar-based substrates which in most cases is not economically viable. As a low-cost carbon source, short-chain fatty acids (SCFAs) that can be obtained from food wastes offer an interesting alternative for achieving an affordable lipid production process. In this study, SCFAs were employed to accumulate lipids using Yarrowia lipolytica ACA DC 50109. For this purpose, different amounts of SCFAs, sulfate, phosphate and carbon: phosphate ratios were used in both synthetic and real SCFAs-rich media. Although sulfate limitation did not increase lipid accumulation, phosphate limitation was proved to be an optimal strategy for increasing lipid content and lipid yields in both synthetic and real media, reaching a lipid productivity up to 8.95 g/L h. Remarkably, the highest lipid yield (0.30 g/g) was achieved under phosphate absence condition (0g/L). This fact demonstrated the suitability of using low-phosphate concentrations to boost lipid production from SCFAs.

Concept of Batch and Fed-Batch Cultures of Yarrowia lipolytica as a Valuable Source of Sterols with Simultaneous Valorization of Molasses and Post-Frying Rapeseed Oil

Food byproduct streams can potentially be transformed into value-added products such as microbial lipids in bioprocesses based on the non-conventional Yarrowia yeast. The effect of culture conditions of Y. lipolytica KKP 379 wild strain in waste media on the efficiency of lipid accumulation, fatty acid composition, presence of selected sterols, yield and elemental composition of biomass has been studied. Batch and fed-batch bioreactor cultures were carried out in media with molasses hydrolysate (MH) and post-frying rapeseed oil. It was determined that biomass grown in MH contained more minerals than in medium with rapeseed post-frying oil. Considering the PDSC study, the Tmax of oxidation induction ranged from 10.04–26.36 min for the analyzed samples. The biomass from fed-batch cultures with MH had the highest total sterol content (68.40 mg/goil), dominated by ergosterol at 60.16 mg/g. Feeding with post-frying rapeseed oil with new doses of mineral medium promoted maintaining the cellular lipid content at a high level (30.75–31.73%) for 50 h, with maximum yield at 37.50%. The results of the experiment showed that the cellular lipid accumulation efficiency of Y. lipolytica yeast and the content of sterols in the cell membrane can be manipulated by selecting waste substrates and culture mode.