Front Matter

(Tina Sui) #1
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.)

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