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High‐titer production and strong antimicrobial activity of sophorolipids from Rhodotorula bogoriensis

Rhodotorula bogoriensis produces sophorolipids (SLs) that contain 13‐hydroxydocosanoic acid (OH‐C22) as the lipid moiety. A systematic study was conducted to further understand the fermentative production of SLs containing OH‐C22 (C22‐SL) by R. bogoriensis. Shake‐flask studies showed that R. bogoriensis consumed glucose at a slow pace. HPLC analysis of the C22‐SL products from shake‐flask fermentations at different glucose concentrations showed a correlation between glucose depletion and the extent of C22‐SL deacetylation. A large‐scale bioreactor fermentation resulted in the isolation of C22‐SL at a volumetric product yield of 51 g/L. HPLC analysis of C22‐SL product from the bioreactor fermentation corroborated the finding that glucose depletion correlated with extensive deacetylation of C22‐SL. The antimicrobial activity of C22‐SL was established for the first time to be stronger than the C18‐SL from Candida bombicola against Propionibacterium acnes in a plate assay. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:867–874, 2015