Enzymatic conversion of diacetylated sophoroselipid into acetylated glucoselipid: surface-active properties of novel bolaform biosurfactants.

Sophoroselipids (SL) are bolaform biosurafactants which are abundantly produced by microorganisms from renewable resources. In this study, four kinds of bolaform biosurfactants were produced, and these derivatives were chemoenzymatically synthesized from "acid form" diacetylated SL (SLdiAc), which are preferentially produced by Candida floricola TM 1502 which was newly found in our group. The effects of the structure of sugar moiety on their surface-active properties were investigated by surface tension measurement. After microbial production of SLdiAc from oleic acid/glucose, SLdiAc was converted into acetylated glucoselipid (GLAc). Among twelve species of glucosidases, pectinase and pectolyase including polygalacturonase were found to cleave the beta-1,2-glycosidic linked disaccharide, especially pectolyase produced GLAc effectively at 40 degrees C and pH 4.0. The structure of the major component of purified GLAc was assigned as 17- [(beta-D-glucopyranosyl)oxy]-cis-9-octadecenoate 6'-acetate by using NMR analyses, MALDI-TOF/MS and GC-MS. Glucoselipid (GL) without acetyl group was also enzymatically converted from SL obtained from alkaline hydrolysis of SLdiAc. Interestingly, the estimated CMC values of SLdiAc, SL, GLAc, GL indicated almost the same values despite their difference in hydrophilic structure. Although the difference in monosaccaride and disaccharide also did not affect gammaCMC, the presence of acetyl group on sugar moiety was found to lower the gammaCMC value slightly, suggesting that the acetyl group on produced bolaform biosurfactant is likely to play more important role to reduce the free energy of air/water interface.