Isolation of Oleaginous Yeast and Media Optimization for Enhanced Lipid Production from Soil Samples

Aim: The aim of this study was to isolate oleaginous yeast from soil and to optimize media components for enhanced lipid accumulation using different carbon and nitrogen sources, followed by statistical analysis at a 5% significance level. Study Design, Place, and Duration: An experimental laboratory-based study was conducted in the Microbiology laboratory of the institution. The study was carried out over a period of several months. Methodology: Oleaginous yeasts are defined as yeasts capable of accumulating more than 20% lipid of their dry biomass. Soil samples were collected and subjected to enrichment culture, followed by plating on Yeast Extract Peptone Dextrose (YPD) agar for yeast isolation. The enrichment culture yielded 2.22 × 10⁸ CFU/mL. White, creamy, round colonies were considered as yeast and selected for further screening. Screening for oleaginous yeast was performed using nitrogen-limited medium (NLM), as nitrogen limitation is known to be the most effective condition for inducing lipogenesis. Media optimization was carried out using different carbon sources (glucose, molasses, and agricultural waste) and nitrogen sources (ammonium sulphate and peptone). Lipids were extracted from yeast biomass using the Bligh and Dyer method. The obtained data were statistically analyzed using one-way ANOVA at a 5% significance level. Results: The isolated yeast strains accumulated lipid content exceeding 20% of dry biomass, confirming their oleaginous nature. Media containing glucose, molasses, and ammonium sulphate resulted in significantly higher lipid accumulation compared to media containing peptone and agricultural waste. Among the carbon sources tested, molasses supported the highest lipid yield. Conclusion: The study successfully isolated oleaginous yeast from soil and demonstrated that nitrogen limitation significantly enhances lipid accumulation. Media optimization revealed that glucose, molasses, and ammonium sulphate are effective substrates for lipid production, with molasses showing the highest potential. These findings highlight the applicability of low-cost substrates for sustainable microbial lipid production.