Hexanoic acid improves the production of lipid and oleic acid in Yarrowia lipolytica: The benefit of integrating biorefinery with organic waste management

Microbial oil serves as a sustainable feedstock for producing biodiesel and bio-jet fuels in biorefineries. Sustainable and economical microbial oil production requires the combination of the biorefinery concept and organic waste management. Here, volatile fatty acids (VFAs), by-products of anaerobic digestion of organic waste, have been incorporated as co-substrates in lignocellulosic microbial oil production by an oleaginous yeast of Yarrowia lipolytica. The supplementation of VFAs (acetic, butyric, and hexanoic acids) increased microbial oil production of Y. lipolytica by up to 47%. Specifically, the oleic acid content in microbial oil increased from 41% to 64% with hexanoic acid supplementation, resulting in a 1.5-fold increase in oleic acid titer. Transcriptome analysis showed that hexanoic acid altered fatty acid metabolism (through β- and ω-oxidation) and global transcriptional regulation during microbial oil production. These findings suggest that hexanoic acid is a useful supplement that improves the industrial yield of microbial oil and selectively increases oleic acid content.