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.