Microbial production, structure elucidation and bioconversion of sophorose lipids

Abstract

Cultivation of Torulopsis bombicola ATCC 22214 on a mixture of glucose and oleic acid (A) or oleic acid alone (B) produced large amounts of sophorose lipids. In the case of A, 38 g/1 of crude product were finally isolated; fermentation B led to 77 g/1. After separation by MPLC and TLC, six glycolipids were obtained and identified by NMR and fast atom bombardment‐mass spectrometry (FAB‐MS). In general, a 17‐hydroxyocta‐decanoic acid at the C‐1’ ‐position and acetate groups at the C‐6’ ‐and C‐6’ ‐positions of sophorose were found as substituents in the lactone and acidic forms of these lipids. The composition of product from A was as follows: 62% of sophorolipid 1’,4’ ‐lactone 6’ ,6’ ‐diacetate (SL‐1), 4% of sophorolipid 1’,4’‐lactone 6’‐monoacetate (SL‐2), 4% of sophorolipid 1’,4 ’‐lactone (SL‐3), 4% of sophorolipid 1’,6’‐and l’,6’‐lactones (SL‐4a,b), 4% of sophorolipid 6’‐monoacetate acid (SL‐5), 4% of sophorolipid acid (SL‐6) and finally 17% of other lipids. In B, the principal lactone (40%) had a double bond in the fatty acid moiety; the other components were identical with the above products. Yields of 13% SL‐2 and of 35% lipids containing no carbohydrate were significant. SL‐1 was deacetylated to SL‐3 (yield: 25‐307c) using acetyl‐esterase in a two‐phase system (cyclohexane/water).