Valorisation of sugarcane molasses for the production of microbial lipids via fermentation of two <i>Rhodosporidium</i> strains for enzymatic synthesis of polyol esters

Abstract BACKGROUND Bioprocess development for microbial oil production using cane sugar and sugarcane molasses via fermentation followed by enzymatic conversion into fatty acid esters is presented in this study. RESULTS Microbial oil was initially evaluated in shake flask fermentations of Rhodosporidium toruloides NRRL Y‐27012 and R. kratochvilovae Y‐43 using either very high polarity (VHP) cane sugar or sugarcane molasses. Supplementation of phosphate salts, trace elements and nitrogen sources in molasses‐based cultures influenced yeast growth and microbial oil production. R. kratochvilovae had different nutrient requirements than R. toruloides . Fed‐batch bioreactor cultures of R. toruloides in molasses‐based cultures without any phosphate salts and trace element supplementation led to a microbial oil concentration of 25 g L −1 and an intracellular lipid content of 61% ( w / w ). Nutrient supplementation influenced the fatty acid composition of microbial oils indicating that enrichment in oleic acid could be achieved (up to 65.1%). The microbial oil produced by R. toruloides was enzymatically converted into polyol esters with a conversion yield of more than 85% ( w / w ). CONCLUSION This study demonstrates that Rhodosporidium sp. can be cultivated in molasses for the production of oleic acid enriched microbial lipids by adjusting medium composition. The polyol esters derived from microbial lipids could be used as a renewable feedstock for oleochemical production. © 2019 Society of Chemical Industry