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

Rhodotorula bogoriensis produces sophorolipids (SLs) that contain 13‐hydroxydocosanoic acid (OH‐C 22 ) as the lipid moiety. A systematic study was conducted to further understand the fermentative production of SLs containing OH‐C 22 (C 22 ‐SL) by R. bogoriensis . Shake‐flask studies showed that R. bogoriensis consumed glucose at a slow pace. HPLC analysis of the C 22 ‐SL products from shake‐flask fermentations at different glucose concentrations showed a correlation between glucose depletion and the extent of C 22 ‐SL deacetylation. A large‐scale bioreactor fermentation resulted in the isolation of C 22 ‐SL at a volumetric product yield of 51 g/L. HPLC analysis of C 22 ‐SL product from the bioreactor fermentation corroborated the finding that glucose depletion correlated with extensive deacetylation of C 22 ‐SL. The antimicrobial activity of C 22 ‐SL was established for the first time to be stronger than the C 18 ‐SL from Candida bombicola against Propionibacterium acnes in a plate assay. © 2015 American Institute of Chemical Engineers Biotechnol. Prog ., 31:867–874, 2015