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. (c) 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:867-874, 2015