Journal of biotechnology vol:33 issue:2 pages:147-155
The production of extracellular sophorose lipid by Candida apicola IMET 43747 was studied after growth on glucose as sole carbon source. In the presence of citrate and after 120 h of cultivation, the microcrystalline lactonic sophorose lipid started to appear in the medium. The lipid was shown to accumulate in the cell wall and only a minor part was liberated into the medium. By means of NMR studies it was shown that the cell wall-bound and the liberated lactonic sophorose lipid were identical and had a hydroxy DELTA8-hexadecenoic acid backbone. Biotransformation of D-[1-C-13]glucose revealed that in glucose-grown cells glucose was degraded to trioses which were rearranged and flow backward via the gluconeogenic pathway into the glycolipid as documented by scrambling of the C-13 label from the C-1 position into the D-[6-C-13]glucose of sophorose. A further part of the trioses was used for de novo synthesis of the glycolipid fatty acid moiety via acetyl-CoA. By use of a mixed substrate, i.e., glucose and hexadecane, part of the glucose added was directly incorporated into the carbohydrate moiety of the lipid. These results are discussed in terms of the physiological significance of the sophorose lipid to act as extracellular carbon storage material.