Production of Biofuel from Oleaginous Microorganisms

Abstract

The increasing demand for sustainable and eco-friendly energy sources has driven significant interest. Production of biodiesel from oleaginous microorganisms is growing along with improvation. These microorganisms, including certain species of yeast, microalgae, fungi, and bacteria, are capable of accumulating of lipids, especially yeast will accumulate high amounts of lipids, primarily in the form of triacylglycerols (TAGs), which can be transesterified into biodiesel. Unlike conventional feedstocks, microbial lipid production does not compete with food crops for arable land, making it a more sustainable alternative. This study shows the isolation, cultivation, and lipid accumulation potential of oleaginous microorganisms under various nutritional and environmental conditions. Factors influencing lipid productivity, such as carbon and nitrogen sources, C/N ratio, temperature, and pH, are critically analysed. Additionally, downstream processing methods, including cell harvesting, lipid extraction, and transesterification, are discussed. The results shows the feasibility of utilising microbial lipids for biodiesel production and suggest that oleaginous microorganisms represent a promising avenue for the development of next-generation biofuels. Biodiesel can be mixed with normal diesel.

Introduction

The text reviews the growing need for sustainable energy alternatives due to rising global energy demand, heavy reliance on fossil fuels, and associated greenhouse gas emissions that drive climate change. Biodiesel is highlighted as a cleaner renewable fuel with properties similar to conventional diesel, but its large-scale production from edible plant oils raises concerns related to food security, land use, and high costs.

To overcome these limitations, oleaginous microorganisms (OMs)—including microalgae, yeasts, fungi, and some bacteria—are presented as promising alternative lipid sources. These microbes can accumulate large amounts of lipids (20–80% of dry cell weight), grow rapidly, require less land and water than oil crops, and can utilize low-cost substrates such as lignocellulosic biomass, agro-residues, glycerol, and industrial wastewaters. Among them, oleaginous yeasts (e.g., Yarrowia lipolytica, Rhodosporidium toruloides, Lipomyces starkeyi) are particularly attractive due to their metabolic flexibility, robustness, and high lipid productivity.

The text emphasizes brewery wastewater (BWW) as a nutrient-rich, low-cost growth medium that can support microbial growth while simultaneously addressing wastewater treatment challenges. Using such wastes supports a circular bioeconomy by coupling waste management with biofuel and bioproduct generation (e.g., biodiesel, carotenoids).

Key factors influencing microbial lipid production include substrate type, carbon-to-nitrogen (C:N) ratio—especially nitrogen limitation—fermentation strategy, and cultivation conditions. Advances in metabolic and genetic engineering (e.g., CRISPR-based modifications) have further improved lipid yields. The document also outlines lipid extraction methods, biodiesel conversion processes, and fuel properties, demonstrating that microbial biodiesel can meet or exceed international fuel standards.

Conclusion

The present study successfully demonstrated the isolation, screening, and utilisation of oleaginous microorganisms from brewery wastewater for lipid accumulation and biodiesel production. The characterisation of waste water was d successfully done by checking various factors like COD,BOD,TDS and TSS and it was suitable to harvest the oleaginous microorganisms. The Sudan Black B staining method effectively confirmed the presence of lipid-accumulating microbes, indicated by the appearance of black inclusions under microscopic observation and the rest of non lipid accumulating part will be of no colour. Various carbon sources—glucose, sucrose, lactose, and maltose—were tested to evaluate their influence on microbial growth and lipid accumulation. Among these, lactose and glucose were found to be the most effective substrates, resulting in higher biomass yields and lipid content. This shows that simpler or more accessible metabolic pathways. The lipid extraction using a methanol–chloroform mixture was efficient, producing clear separation of lipid layers, which were further processed through transesterification. Transesterification process which is the conversion of extracted lipids into biodiesel through methanol and sodium hydroxide catalysis was successful, cultures yielding the highest quantities of biodiesel. The quality of the biodiesel was confirmed through combustion, which produced a clean flame with slight black ash, indicating the presence of combustible esters. In conclusion, this study demonstrates a sustainable and cost-effective method for biodiesel production using brewery wastewater and low-cost carbon sources. The process not only save the cost of treating the waste water but also supports renewable energy by converting microbial lipids into valuable biofuels.

Copyright

Copyright © 2025 Shobhan Majumder, Krithika Alanahally, Deepali Sagar, Dhanyashree S, R Janardhan, Sahana Mohan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.