Enhanced lipid production from acetate by oleaginous yeast co-cultivation and transcriptomic characterization

Microbial lipids are promising alternative oil sources, particularly for biodiesel production, but their industrial application is limited by high fermentation costs and low lipid yields. Volatile fatty acids (VFAs) derived from organic waste represent potential low-cost substrates for microbial lipid production. This study investigated the co-cultivation of oleaginous yeasts using acetic acid as a carbon source to enhance lipid production. Four oleaginous yeast strains were evaluated under mono- and co-cultivation conditions, and the combination of Yarrowia lipolytica and Rhodotorula glutinis showed the highest lipid production performance among the tested combinations. Response surface methodology was applied to optimize cultivation parameters, including acetate concentration, C/N ratio, and inoculation ratio. Under the optimized conditions, co-cultivation achieved a lipid concentration of 1.04 ± 0.05 g/L, with increases of 18.07% and 26.83% in dry cell weight and lipid concentration, respectively, compared with Y. lipolytica mono-cultivation, and increases of 47.47% and 30.00%, respectively, compared with R. glutinis mono-cultivation. Transcriptomic analysis revealed co-cultivation-associated changes in lipid metabolism-related gene expression in Y. lipolytica . Genes associated with fatty acid and triglyceride biosynthesis, including HTD2, MECR, FAS1, FAS2, AGPAT1_2, and DGAT1, showed increased transcript abundance, whereas TGL3 and TGL4 showed decreased expression. These transcriptional changes were associated with enhanced lipid accumulation under co-cultivation and provide insights into the metabolic responses of oleaginous yeasts during co-cultivation.