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Title: High-titer production and strong antimicrobial activity of sophorolipids from Rhodotorula bogoriensis

Author
item Solaiman, Daniel
item Ashby, Richard - Rick
item Cross, Nicole

Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2015
Publication Date: 5/27/2015
Citation: Solaiman, D., Ashby, R.D., Crocker, N.V. 2015. High-titer production and strong antimicrobial activity of sophorolipids from Rhodotorula bogoriensis. Biotechnology Progress. DOI: 10.1002/btpr.2101.

Interpretive Summary: Sophorolipids (SLs) are eco-friendly detergents produced by some yeast species. The one produced by a particular yeast called Rhodotorula bogoriensis is unique. The water-hating (or hydrophobic) part of its SL contains a longer chain fat molecule than those produced by other yeast. To take advantage of this special molecule, we characterize the production process in order to lay down the groundwork for economical commercial production. Our study led to a drastic reduction in the use of the growth substrate, glucose. We also found that depending on the availability of the glucose, the structure of the SL was modified, suggesting for the first time that SL can be a reserve food for the organism in time of stress. Finally, we established for the first time that the special SL from Rhodotorula bogoriensis not only has an antimicrobial activity, but also seems to be stronger than the ones produced by other yeast.

Technical Abstract: 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.