tion. A complete deacetylation at C6’and C6“under preservation of the lactone ring is
also possible by the attack of an immobilized acetylesterase. The immobilization of
the acetylesterase prevents side reactions as cleavage of the lactone ring and glyco-
sidic linkages (Asmer et al., 1988).
Recently, Scholz et al. (1998) and Bisht et al. (1999) succeeded in the enzymatic
synthesis of well-defined sophorolipid analogs. A careful spectroscopic analysis was
performed of all modified SL. They used 17–OH-C18 : 1sophorolipids as feedstock
based on a cultivation with glucose/oleic acid as substrates. The alkaline hydrolysis
according to Tulloch et al. (1968) resulted in the deacetylated 17-OH-C18 : 1sophoro-
lipid acid as sole product. Unfortunately, this product was soluble only in highly
polar solvents such as water, dimethylformamide, DMSO or pyridine. The conver-
sion with a mixture of sodium methoxide, ethoxide or butoxide yielded in a sophoro-
lipid ester (Figure 8, top) with enhanced hydrophobic characteristics soluble in an-
hydrous tetrahydrofuran. Lipase B fromCandida antarctica(Novozym 435) was
384 17 Enzymatic Synthesis and Modification of Glycolipids
Figure 8. Enzymatic modification of deacetylated 17-OH C18 : 1ester SL by Novozym 435 lipase.
(Redrawn from Bisht et al., 1999.)