Microbial Oil Research Articles

Studying microbial triglyceride production from corn stover saccharides unveils insights into the galactose metabolism of Ustilago maydis

The global demand for plant oil has reached unprecedented levels and is relevant in all industrial sectors. Driven by the growing awareness for environmental issues of traditional plant oils and the need for eco-friendly alternatives, microbial oil emerges as a promising product with significant potential. Harnessing the capabilities of oleaginous microorganisms is an innovative approach for achieving sustainable oil production. To increase economic feasibility, it is crucial to explore feedstocks such as agricultural waste streams as renewable resource for microbial bioprocesses. The fungal model Ustilago maydis is one promising organism in the field of microbial triglyceride production. It has the ability to metabolize a wide variety of carbon sources for cell growth and accumulates high amounts of triglycerides intracellularly. In this study we asked whether this large variety of usable carbon sources can also be utilized for triglyceride production, using corn stover saccharides as a showcase.Our experiments revealed metabolization of the major saccharide building blocks present in corn stover, demonstrating the remarkable potential of U. maydis. The microorganism exhibited the capacity to synthesize triglycerides using the saccharides glucose, fructose, sucrose, xylose, arabinose, and galactose as carbon source. Notably, while galactose has been formerly considered as toxic to U. maydis, we found that the fungus can metabolize this saccharide, albeit with an extended lag phase of around 100 hours. We identified two distinct methods to significantly reduce or even prevent this lag phase, challenging previous assumptions and expanding the understanding of U. maydis metabolism.Our findings suggest that the two tested methods can prevent long lag phases on feedstocks with high galactose content and that U. maydis can produce microbial triglycerides very efficiently on many different carbon sources. Looking forward, exploring the metabolic capabilities of U. maydis on additional polymeric components of corn stover and beyond holds promise for innovative applications, marking a significant step toward environmentally sustainable bioprocessing technologies.

Microbial Decontamination of Cuminum cyminum Seeds Using "Intensification of Vaporization by Decompression to the Vacuum": Effect on Color Parameters and Essential Oil Profile.

Cumin seeds are frequently utilized in herbal infusions and as flavoring agents in home cuisine. Nevertheless, studies have demonstrated that spices are frequently contaminated with pathogenic bacteria, including bacterial spores. The aim of this study was to assess the effectiveness of a new decontamination method called "Intensification of Vaporization by Decompression to the Vacuum" (IVDV) on intentionally contaminated Cuminum cyminum seeds. The study also examined the impact of this treatment on the color and oil profile of the treated samples. The untreated samples were inoculated with Escherichia coli (ATCC 25922) and Salmonella Typhimurium (ATCC 14028) and then subjected to IVDV treatment. Response surface methodology was employed to obtain safe, high-quality cumin seeds presenting a balance between microbial load, color, and oil profile. The optimal IVDV conditions were achieved at a pressure of 3.5 bar and a time of 133.45 s, resulting in typical 4 log reductions observed with 99.99% of Escherichia coli and Salmonella Typhimurium inactivation. The treated spices presented a mild color modification compared to the untreated ones, manifested by a darker shade (decreased L* value), reduced greenness (increased a* value), and heightened yellowness (increased b* value). The GC-MS analysis detected the existence of seven compounds in the treated cumin, with cuminaldehyde being the primary compound (83.79%). Furthermore, the use of IVDV treatment resulted in an increase in the total content of essential oils in some samples, whereby six monoterpenes were identified in the untreated sample compared to seven monoterpenes in IVDV-treated samples. This innovative technology demonstrated high efficacy in decontaminating C. cyminum seeds, improving the extractability of the essential oils while only slightly affecting the color.

Appropriate characterization of reservoir properties and investigation of their effect on microbial enhanced oil recovery through simulated laboratory studies

Appropriate characterization of reservoir properties and investigation of the effect of these properties on microbial metabolism and oil recovery under simulated reservoir conditions can aid in development of a sustainable microbial enhanced oil recovery (MEOR) process. Our present study has unveiled the promising potential of the hyperthermophilic archaeon, identified as Thermococcus petroboostus sp. nov. 101C5, to positively influence the microenvironment within simulated oil reservoirs, by producing significant amounts of metabolites, such as biosurfactants, biopolymers, biomass, acids, solvents, gases. These MEOR desired metabolites were found to cause a series of desirable changes in the physicochemical properties of crude oil and reservoir rocks, thereby enhancing oil recovery. Furthermore, our study demonstrated that the microbial activity of 101C5 led to the mobilization of crude oil, consequently resulting in enhanced production rates and increased efficiency in simulated sand pack trials. 101C5 exhibited considerable potential as a versatile microorganism for MEOR applications across diverse reservoir conditions, mediating significant light as well as heavy oil recovery from Berea/carbonaceous nature of rock bearing intergranular/vugular/fracture porosity at extreme reservoir conditions characterized by high temperature (80–101 °C) and high pressure (700–1300 psi). Core flood study, which truly mimicked the reservoir conditions demonstrated 29.5% incremental oil recovery by 101C5 action from Berea sandstone at 900 psi and 96 °C, underscoring the potential of strain 101C5 for application in the depleted high temperature oil wells.

The effect of microencapsulation of microbial oil containing CLA by the complex coacervation on the physicochemical and sensory characteristics of buttermilk

Conjugated Linoleic Acid (CLA) is known for their positive impact on reducing various diseases, including cardiovascular diseases and blood lipid levels. This study aims to produce enriched buttermilk with stable physicochemical properties via complex coacervation. To address the inherent instability of oils in liquid systems, microcapsules were prepared using sodium alginate and xanthan gum, with optimization achieved through the response surface method (RSM). The buttermilk, enriched at optimal levels of 0 %, 0.04 %, 0.07 %, and 0.1 %, was then incubated at 48 °C for 42 days. Under the optimized conditions, the choice and quantity of gums used for enrichment significantly influenced the properties of the enriched buttermilk. A decrease in pH, along with an increase in acidity, led to enhanced viscosity in the buttermilk. The flow behavior of the buttermilk exhibited pseudoplastic characteristics. Enrichment caused an increase in particle size, with only minimal changes in odor, taste, and color parameters, while the buttermilk remained free from protein agglutinates. Chromatography results showed an increase in unsaturated fatty acids after enrichment. In summary, this study demonstrates the feasibility of producing nutritionally enriched buttermilk with high stability and desirable sensory characteristics. The recommended concentrations for enrichment are 0.04 % and 0.07 %.

High-throughput screening of non-conventional yeasts for conversion of organic waste to microbial oils via carboxylate platform

Converting waste into high-value products promotes sustainability by reducing waste and creating new revenue streams. This study investigates the potential of diverse yeasts for microbial oil production by utilizing short-chain fatty acids (SCFAs) that can be produced from organic waste and focuses on identifying strains with the best SCFA utilisation, tolerance and lipid production. A collection of 1434 yeast strains was cultivated with SCFAs as the sole carbon source. Eleven strains emerged as candidates with promising growth rates and high lipid accumulation. Subsequent fermentation experiments in liquid SCFA-rich media, which focused on optimizing lipid accumulation by adjusting the carbon to nitrogen (C/N) ratio, showed an increase in lipid content at a C/N ratio of 200:1, but with a concurrent reduction in biomass. Two strains were characterized by their superior ability to produce lipids compared to the reference strain Yarrowia lipolytica CECT124: Y. lipolytica EXF-17398 and Pichia manshurica EXF-7849. Characterization of these two strains indicated that they exhibit a biotechnologically relevant balance between maximizing lipid yield and maintaining growth at high SCFA concentrations. These results emphasize the potential of using SCFAs as a sustainable feedstock for oleochemical production, offering a dual benefit of waste valorisation and microbial oil production.

Research on Microbial Community Structure in Different Blocks of Alkaline–Surfactant–Polymer Flooding to Confirm Optimal Stage of Indigenous Microbial Flooding

The microbial communities associated with alkaline–surfactant–polymer (ASP)-flooded reservoirs have rarely been investigated. In this study, high-throughput sequencing was used to analyse the indigenous microbial communities in two different blocks, the water flooding after the alkaline–surfactant–polymer flooding block and the alkaline–surfactant–polymer flooding block, and to ascertain the optimal stage for the implementation of indigenous microbial oil recovery technology. The different displacement blocks had significant effects on the indigenous microbial community at the genus level according to an alpha diversity analysis and community composition. In water flooding after alkaline–surfactant–polymer flooding, the dominant genus of Pseudomonas exceeded 30%, increasing to 52.1% in alkaline–surfactant–polymer flooding, but alpha diversity decreased. Through a co-occurrence network analysis, it was found that the complexity of the water flooding after alkaline–surfactant–polymer flooding was higher than that of alkaline–surfactant–polymer flooding. This means that the water flooding ecosystem after alkaline–surfactant–polymer flooding was more stable and less susceptible to external environmental influences. In addition, there were significant differences in the functional redundancy of microbial communities in different blocks. In summary, the optimal stage for implementing local microbial oil recovery technology may be water flooding after alkaline–surfactant–polymer flooding.

Development of oil-producing microbiota and its application in fermenting distiller's grains to obtain microbial oil and ruminant feed

With the depletion of global fossil energy, it is a good choice to produce biodiesel (renewable energy) from waste biomass resources. We tried to domesticate microbiota with distiller's grains as medium, and obtained genetically stable and acid-resistant microbiota JQY1, which could convert lignocellulose into microbial oil. Amplicon sequencing results showed that Proteobacteria (94.05 %) and ascomycetes (100 %) were the main phyla, and Rhizobiaceae_unclassified (41.19 %) and Pseudomonas (24.47 %) were the dominant genera, The fungi are Wickerhamomyces and Meyerozyma, and their abundance accounts for 70.8 % and 26.32 % respectively. Using external carbon sources in the microbial body one-step fermentation of distiller's grains by microbiota JQY1 can yield a microbial oil content of 2.52 g/L. The fatty acid composition, including palmitic acid, stearic acid, oleic acid, and linoleic acid, conforms to the specifications for biodiesel raw materials set by the American ASTM. The contents of distiller's grains after fermentation were detected, in which the crude protein increased by 6.19 % and the crude fiber decreased by 10.18 %. Microbial cooperation can effectively degrade lignocellulose and transform it into microbial oil. In addition, the distiller's grains after fermentation have higher value as ruminant feed. Through one-step fermentation, we can achieve a win-win strategy of efficiently harvesting biodiesel and improving the nutritional components of distiller's grains to feed animals, which not only reduces the production cost of microbial oil, but also solves the final destination problem of distiller's grains and makes important contributions to promoting the circular economy of distiller's grains.

Cell envelope and stress-responsive pathways underlie an evolved oleaginous Rhodotorula toruloides strain multi-stress tolerance

BackgroundThe red oleaginous yeast Rhodotorula toruloides is a promising cell factory to produce microbial oils and carotenoids from lignocellulosic hydrolysates (LCH). A multi-stress tolerant strain towards four major inhibitory compounds present in LCH and methanol, was derived in our laboratory from strain IST536 (PYCC 5615) through adaptive laboratory evolution (ALE) under methanol and high glycerol selective pressure.ResultsComparative genomic analysis suggested the reduction of the original strain ploidy from triploid to diploid, the occurrence of 21,489 mutations, and 242 genes displaying copy number variants in the evolved strain. Transcriptomic analysis identified 634 genes with altered transcript levels (465 up, 178 down) in the multi-stress tolerant strain. Genes associated with cell surface biogenesis, integrity, and remodelling and involved in stress-responsive pathways exhibit the most substantial alterations at the genome and transcriptome levels. Guided by the suggested stress responses, the multi-stress tolerance phenotype was extended to osmotic, salt, ethanol, oxidative, genotoxic, and medium-chain fatty acid-induced stresses.ConclusionsThe comprehensive analysis of this evolved strain provided the opportunity to get mechanistic insights into the acquisition of multi-stress tolerance and a list of promising genes, pathways, and regulatory networks, as targets for synthetic biology approaches applied to promising cell factories, toward more robust and superior industrial strains. This study lays the foundations for understanding the mechanisms underlying tolerance to multiple stresses in R. toruloides, underscoring the potential of ALE for enhancing the robustness of industrial yeast strains.

Microbial Biotechnologies to Produce Biodiesel and Biolubricants from Dairy Effluents

The shift from fossil fuels to renewable energy sources is crucial in addressing environmental challenges. Vegetable oils have been focused on as the main potential source for biodiesel and biolubricant production. However, due to their fatty acid (FA) composition they are characterized by low stability to oxidation and variable viscosity. Single-cell oils (SCOs) from oleaginous microorganisms are a possible alternative to vegetable oils: their composition is more suitable, and it can further be improved by controlling the fermentation’s physiological conditions. In the present study, the production of SCOs with targeted technological properties from Lipomyces starkeyi in fermentation under controlled temperatures was assessed. A dairy effluent (scotta) was used as the fermentation substrate to improve the economic sustainability of the process. Batch aerobic fermentations were carried out in a fermenter at two different temperatures (25 °C and 30 °C). The fermentation yields and SCO FA profiles were analyzed. The highest yields of biomass (9.76 g L−1) and microbial oil (1.83 g L−1) were obtained from fermentations carried out at 30 °C. Furthermore, a significantly lower content (46% vs. 55%) of unsaturated FAs and higher content (11% vs. 1.5%) of shorter-chain saturated FAs, with myristic acid almost matching stearic acid, were detected at 30 °C in comparison to 25 °C. Very low peroxide values were also found (0.14 meq O2 kg−1 at 30 °C and 0 meq O2 kg−1 at 25 °C). These results indicate that these SCOs were highly oxidation-resistant, and that a higher fermentation temperature improves their oxidative stability and tribophysical features. The biodiesels’ technological properties, calculated from the FA composition, were within the limits of both U.S. standards and E.U. regulations. Then, SCOs produced from L. starkeyi by fermentation of dairy effluents carried out under controlled temperature can be considered a suitable alternative to vegetable oils to produce biodiesel and biolubricants.

Bioproduction of yeast single cell oil with acute oral toxicity study intended for edible oil application.

Human nutrition and health rely on edible oils. Global demand for edible oils is expanding, necessitating the discovery of new natural oil sources subjected to adequate quality and safety evaluation. However, in contrast to other agricultural products, India's edible oil supply is surprisingly dependent on imports. The microbial oil is generated by fermentation of oleaginous yeast Rhodotorula mucilaginosa IIPL32 MTCC 25056 using biodiesel plant byproduct crude glycerol as a fermentable carbon source. Enriched with monounsaturated fatty acid, nutritional indices mapping based on the fatty acid composition of the yeast SCO, suggested its plausible use as an edible oil blend. In the present study, acute toxicity evaluation of the yeast SCO in C57BL/6 mice has been performed by randomly dividing the animals into 5 groups with 50, 300, 2000, and 5000mg/Kg yeast SCO dosage, respectively, and predicted the median lethal dose (LD50). Detailed blood biochemistry and kidney and liver histopathology analyses were also reported. The functions of the liver enzymes were also evaluated to check and confirm the anticipated toxicity. To determine cell viability and in vitro biocompatibility, the 3T3-L1 cell line and haemolysis tests were performed. The results suggested the plausible use of yeast SCO as an edible oil blend due to its non-toxic nature in mice models.

Nutritional and Medicinal Properties of Microbial Oil

Plant and animal oils and fats currently dominate the edible oil market, but a new sustainable alternative of lipids from single-celled organisms has become advantageous in human nutrition and pharmacy. Single-cell oils (SCOs) are lipids biosynthesized and accumulated in the lipid bodies of oleaginous species of bacteria, yeasts, molds, and algae. The review has investigated SCOs’ composition, with a detailed review of the described beneficial impact in medicine, cosmetics, pharmacy, and nutrition. Although microbial oil has been known for more than 100 years, it was not applied until the 21st century, when commercial SCO production for human use started and administrative regulations governing their use were completed. This article discusses the applications of SCOs, which can be easily found in microorganisms, in the pharmaceutical, cosmetic, and food industries. In addition, some aspects of 15- or 17-carbon-atom-long fatty acids were also pointed out. Furthermore, some challenges for heterotrophic single-cell oil synthesis and improvements in its extraction efficiency have also been concluded, which can further contribute to their broadened use in pharmacy, medicine, cosmetics, and food applications.

Unlocking the potential of spent coffee grounds via a comprehensive biorefinery approach: production of microbial oil and carotenoids under fed-batch fermentation.

The valorization of renewable feedstock to produce a plethora of value-added products could promote the transition towards a circular bioeconomy. This study presents the development of cascade processes to bioconvert spent coffee grounds (SCGs) into microbial oil and carotenoids employing sustainable practices. The stepwise recovery of crude phenolic extract and coffee oil was carried out using green or recyclable solvents, i.e., aqueous ethanol and hexane. Palmitic acid (43.3%) and linoleic acid (38.9%) were the major fatty acids in the oil fraction of SCGs. The LC-MS analysis of crude phenolic extracts revealed that chlorogenic acid dominated (45.7%), while neochlorogenic acid was also detected in substantial amounts (24.0%). SCGs free of coffee oil and phenolic compounds were subjected to microwave-assisted pretreatment under different irradiations and solvents to enhance subsequent enzymatic saccharification. Microwave/water pretreatment at 400 W, followed by enzymatic hydrolysis with proteases, hemicellulases, and cellulases, at 50g/L initial SCGs, led to satisfying overall yields of cellulose (75.4%), hemicellulose (50.3%), and holocellulose (55.3%). Mannan was the most extractable polysaccharide followed by galactan and arabinan. SCGs hydrolysate was used in fed-batch bioreactor fermentations with Rhodosporidium toruloides to produce 24.0g/L microbial oil and carotenoids of 432.9μg/g biomass.

Microbial and insect oils: A sustainable approach to functional lipid

AbstractThe increasing global population, coupled with the effects of climate change on agricultural activities has spurred a demand for sustainable food production to meet human needs. In response to this, there has been a growing interest in sustainable food production initiatives. One of such initiatives is harnessing microbial and insect lipids as valuable ingredients to address increase in demand for lipids across various sectors, including functional food, nutritional supplements, and biodiesel production. Over the last decades, there has been increasing scientific investigations exploring lipid from algae, microbes, and insects as alternatives to traditional agro‐ and marine‐based sources. This review, therefore, presents progress made in microbial and insect oils production, with emphasis on sustainability. Emerging extraction techniques, regulatory and safety requirements, and challenges that exist in the production and utilization of these new lipids are also discussed. The review shows that lipids from a wide range of oleaginous microorganisms and insect species have the potential to serve as a valuable ingredient for healthful food preparation. However, challenges such as cultural acceptance, lack of standardized regulations, high cost, and low yield associated with most emerging environmentally friendly extraction technologies continue to hinder widespread use or adoption of microbial and insect lipids on a global scale. These challenges call for innovations to reduce cost of production and improve lipids yield. So far, a substantial progress has been made in the utilization of readily available feedstocks such as industrial food wastes and sugar‐rich industrial wastewater to grow insects and microorganisms which will significantly reduce the processing costs.

Land-use effects on leaf-litter breakdown in streams in a tropical lowland catchment

The expansion of oil palm and cattle grazing in the tropics continues to alter numerous ecosystem functions. The generated land-use change is potentially impacting stream leaf-litter breakdown, a fundamental process for freshwater ecosystems. To assess the effect of land-use change, we studied breakdown rates of forest (Pachira aquatica, Pouroma aspera, Sloanea ampla, and Hippocratea volubilis) and oil palm (Elaeis guineensis) leaves after a 26-day immersion in streams surrounded by rainforests, grazing lands, or oil palm plantations with and without riparian buffers. In addition, we assessed breakdown drivers by deploying litter bags (248) of two mesh sizes (15 mm and 0.5 mm) allowing or restricting macroinvertebrates’ access (134 coarse-mesh bags and 114 fine-mesh bags). Forest leaf breakdown by microbes (fine-mesh) was lower by 55% in the plantations compared to forests; while microbial oil palm-leaf breakdown was lower by 32% in the unbuffered plantations compared to forests (p < 0.05). Total litter breakdown was lower (p > 0.05) in the plantations but not when these preserved riparian buffers. Litter breakdown was driven primarily by microbes in all land uses except in the buffered plantations, possibly due to increased shredder biomass. These results suggest that oil palm agriculture may decrease microbial stream leaf-litter breakdown, especially in streams with no riparian buffers.

Non-sterile cultivation of oleaginous organisms

Cultivating oleaginous organisms in non-sterile conditions can reduce the energy and cost of microbial oil production. Recent studies use strategies that enable non-sterile cultivation without affecting bioprocess productivity. This forum article discusses the trends, strategies, and prospects of non-sterile cultivation, as successful non-sterile cultivation could make microbial oil production economically viable.

Enhancing the biosynthesis of polyunsaturated fatty acids by Rhodotorula mucilaginosa and Lodderomyces elongisporus

Single-cell oils (SCO) produced by oleaginous yeast hold promise as a sustainable alternative for producing nutritionally and pharmaceutically valuable lipids. However, the accumulation of oils varies substantially between yeast spp. Consequently, identifying well-suited producers with a high innate capacity for lipids biosynthesis is paramount. Equally important is optimizing culturing and processing conditions to realize the total lipids production potential of selected strains. The marine Rhodotorula mucilaginosa and Lodderomyces elongisporus yeast were investigated to explore their potential for polyunsaturated fatty acids (PUFAs) production on high glucose media (HGM) using two-stage culture mode. Both strains accumulated > 20% (w/w) of their dry cell weight as lipids when grown on HGM using a two-stage culture system. Both yeast isolates exhibited a maximal lipid/biomass coefficient (YL/X) of 0.58–0.66 mg/mg at 7 °C and 0.49–0.53 mg/mg at 26 °C when grown on 8% glucose and produced monounsaturated and PUFAs similar to that of Menhaden and Salmon marine oils. For the first time, significant amounts of Eicosapentaenoic acid (19%) and Eicosadienoic acid (19.6%) were produced by L. elongisporus and R. mucilaginosa, respectively. Thus, the SCO derived from these wild strains possesses significant potential as a substitute source for the industrial-scale production of long-chain PUFAs, making them a promising contender in the market.Graphical

The Multifaceted Role of Microbial Biosurfactants in Various Fields

This review paper aims to explore the multifaceted roles and applications of microbial surfactants, also known as biosurfactants. These amphiphilic compounds, synthesized by various microorganisms such as Acinetobacter sp., Bacillus sp., Candida antarctica, and Pseudomonas aeruginosa, exhibit both hydrophobic and hydrophilic properties. Through lowering surface tension and interfacial tension, biosurfactants facilitate fluid phase aggregation, imparting organisms with unique physiological and ecological advantages. The synthesis of biosurfactants in bacteria not only contributes to antimicrobial activity but also enhances substrate availability for cellular absorption, particularly in challenging environmental conditions. Categorized based on molecular weight and chemical composition, biosurfactants offer numerous benefits including biodegradability, reduced toxicity, and versatile applications in agriculture, detergent production, biopesticides, and microbial oil enhancement processes. This review synthesizes current knowledge on microbial surfactants, elucidating their diverse roles and promising applications across various industries.

Sugarcane bagasse valorization through integrated process for single cell oil, sulfonated carbon-based catalyst and biodiesel co-production

This study demonstrates the conversion of sugarcane bagasse (SB) into single cell oil (SCO), sulfonated carbon-based catalyst and biodiesel; this process aligns with waste-to-energy and circular bioeconomy concepts. SB was treated with dilute sulfuric acid to achieve SB hydrolysate (SBH) and SB solid residue (SBS). Candida tropicalis KKU-NP1, a newly isolated yeast, accumulated SCO content of 26.5 % from undetoxified SBH medium. A novel sulfonated carbon-based catalyst (SBS@SC) was generated from SBS by a one-step hydrothermal sulfonation process. It showed significant catalytic activity for the conversion of SCO-rich KKU-NP1 wet cell into biodiesel (FAME) under direct transesterification optimal conditions, with a FAME conversion yield of 90.1 %. Based on FAME profile, most of the estimated physicochemical and fuel properties of FAME were within the limits of ASTMD6751 and EN 14214 for biodiesel standards. For integrated process the final production of about 12.0 g SCO, 606.3 g SBS@SC catalyst and 10.8 g biodiesel from 1000 g raw SB were achieved.This study highlights the utilization of SB as a low-cost feedstock for producing multiple value-added products, emphasizing the advantages of waste utilization by integrated biorefinery concept, yielding practically no waste by-products over the whole production process.

Valorization of Sugarcane Vinasse and Crude Glycerol for Single-Cell Oils Production by Rhodotorula glutinis R4: A Preliminary Approach to the Integration of Biofuels Industries for Sustainable Biodiesel Feedstock

Single-cell oils (SCOs) offer a promising alternative to conventional biodiesel feedstocks. The main objective of this work was to obtain SCOs suitable for biodiesel production from the oleaginous yeast Rhodotorula glutinis R4 using sugarcane vinasse from a local sugar-derived alcohol industry as the substrate. Additionally, crude glycerol from the local biodiesel industry was evaluated as a low-cost carbon source to replace expensive glucose and as a strategy for integrating the bioethanol and biodiesel industries for the valorization of both agro-industrial wastes. R4 achieved a high lipid accumulation of 88% and 60% (w/w) in vinasse-based culture media, containing 10% and 25% vinasse with glucose (40 g L−1), respectively. When glucose was replaced with crude glycerol, R4 showed remarkable lipid accumulation (40%) and growth (12.58 g L−1). The fatty acids profile of SCOs showed a prevalence of oleic acid (C18:1), making them suitable for biodiesel synthesis. Biodiesel derived from R4 oils exhibits favorable characteristics, including a high cetane number (CN = 55) and high oxidative stability (OS = 13 h), meeting international biodiesel standards (ASTMD6751 and EN14214) and ensuring its compatibility with diesel engines. R. glutinis R4 produces SCOs from vinasse and crude glycerol, contributing to the circular economy for sustainable biodiesel production.

Exploring the potential of microbial biomass and microbial extracted oils in tribology: a sustainable frontier for environmentally acceptable lubricants

ABSTRACT Mineral oil-derived lubricants, extracted from fossil fuels, account for approximately 90% of the lubricant market. A large proportion of these lubricants end up in the environment through usage, spillage, and disposal, leading to contamination of aquatic systems, ecosystems, and agricultural lands. To address this, new regulations were released (e.g. Vessel General Permit 2013) to promote the use of Environmentally Acceptable Lubricants (EALs) over conventional, toxic, non-biodegradable mineral oils. Today, the range of EAL is limited, particularly affecting the maritime sector. Since 2013, the variety and effectiveness of EALs have improved, but further advancements and cost reductions are essential. This study focuses on developing sustainable bio-based additives from microbial processes to enhance EALs. These additives, sourced through fermentation, avoid using fossil fuels and do not require arable land, preserving water resources and food production areas. The research reveals that yeast, high in sulfur and phosphorus, and microbial oils, mainly carboxylic acids, effectively stabilize EAL formulations, reducing friction and wear in water-based lubricants. Microbial oils are superior in reducing friction, while yeast offers better wear protection. This study opens the possibility of incorporating various bio-based products into EALs, providing a sustainable, environmentally friendly option.