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).