Front Matter

Native sophorolipids are differently acetylated at C6’and C6“. Therefore, require-

ments exist for the formation of sophorolipids with homogeneous acetylation degree.

A regioselective enzymatic deacetylation of 17-L-([2’-O-b-D-glucopyranosyl-b-D-

glucopyranosyl]-oxy)-cis-9-octadecenoic-1’,4“-lactone-6’,6“-diacetate (Figure 8)

leaving the lactone ring intact is reported by de Koster et al. (1995) and Otto et

al. (1999). The monoacetylated lactonic-SL was synthesized from the diacetylated

one using cutinase fromFusarium solani f. sp.pisior immobilizedCandida rugosa

lipase. The substrate (0.3 g) was incubated with 20 units of cutinase at 40 8 C for 20

min at pH 9. Ayield was not specified. The process usingCandida rugosalipase (200

mg) required a prolonged incubation time of 24 h, though 95 % of the substrate (1 g)

was converted. Both enzymes released only the acetyl group at C6’. Molecular mod-

eling studies showed that the diacetylated substrate fits well into the binding pocket

of cutinase, and that C6’-OAc is well accessible to the active site of the enzyme. In

contrast, the acetyl group at C6“is closed in between nonreducing glucose and fatty

acid chain and, thus, is not susceptible to enzymatic hydrolysis. The mono- and

diacetylated SL showed only a slight difference in surface activity (Table 9) due

to the removal of the exposed C6’-OAc substituent and not to a change in conforma-

17.4 Chemically and enzymatically modified sophoroselipids 383

Table 9.Surface-active properties of sophorolipids and sophorosides.

Compound r(mN m–1) CMC (mg l–1) Reference

Diacetylated 17–OH-C18 : 1lactonic-SL
(Figure 6)

35 40 Rau et al., 1999

Monoacetylated 17-OH-C18 : 1lactonic-SL 40.4 15 Otto et al., 1999

Deacetylated 17-OH-C18 : 1acidic-SL 40 100 Rau et al., 1999

Mixture of C18 : 1and C18 : 0(Figure 6):
Deacetylated 17-OH-C 18 -methyl ester SL
Deacetylated 17-OH-C 18 -ethyl ester SL
Deacetylated 17-OH-C 18 -propyl ester SL

40

39.5

38

Inoue et al., 1980

Acetylated 1-Dodecyl sophoroside
Deacetylated 1-Dodecyl sophoroside
Diacetylated 2-dodecyl-sophoroside
Acetylated 2-dodecyl-glucoside
Acetylated 2-Tetradecyl sophoroside)

31

33

30

40

31.4

100

100

100

• 40

Brakemeier et al.,

1998a,b

Lang et al., 1999

Deacetylated 17-OH-C18 : 1acidic
glucolipid (Figure 9)

40 150 Rau et al., 1999

Deacetylated 17-OH-C18 : 1-diethyl
SL amide
n-butyl SL amide
2-butyl SL amide
n-decyl SL amide
n-hexyl SL amide
Deacetylated 17–OH-C18 : 0-benzyl
SL amide (Figure 7)

47

45

44

63

60

39

5

80

20

20

5

Lang et al., 1999

Ishigami, 1994

r¼Surface tension of water against air at 25 8 C.
CMC¼critical micelles concentration.
SL¼Sophorolipid.