Biodiesel production capacity of lipids isolated from yeast strains

The effects of nitrogen N- stress and different pH values (3, 4, 5, and 6) on the growth, triacylglycerol (TAG) accumulation, lipid production, fatty acid profile, and biodiesel quality of Starmerella magnoliae X-3 were investigated. TAG and total lipid values were determined using Nile Red fluorescence and the sulfo-phospho-vanillin (SPV) method, respectively. The findings revealed that the combination of N- stress and acidic pH conditions significantly (p < 0.05) enhanced TAG accumulation, total lipid content, and lipid productivity in Starmerella magnoliae X-3 compared to the control. Under N- stress conditions, the highest TAG accumulation was observed at pH 3 and 5 after 72 hours of cultivation. The highest lipid productivity (0.306 g/L/day) was recorded at pH 3 after 48 hours. The dominant fatty acids at four different pH values were oleic acid (63.6%–64%), palmitoleic acid (11.3%–12.5%), stearic acid (9.7%–11.4%), and palmitic acid (9.4%–10%). In addition, both N- stress and low pH conditions resulted in a lower iodine value and a higher cetane number compared to the control. These results suggest that cultivation of Starmerella magnoliae X-3 under N- stress conditions at pH 3 holds promise for enhancing TAG production.