3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
HO HO
OH
O
OH
R= α/β-H 1a
α-CH3 1b
OR
HO O
HO HO
Yeast lipases gave low yields of pure 3 a,b, thus showing
high specifity for acetylation of primary hydroxyl (Tables
3,4). However, Lipolyve CC was reactive only with the glucoside
1 b and did not acetylate free glucose within 3 days.
On the other side, Amano Lipase A (Aspergillus niger)
as a representative of fungal lipases gave 10% yield of an
equimolar mixture of 2 a, and 3 a. Interestingly, acetylation
O
O
HO HO
O
HO O
O
OH
O
O
OH
2 a,b
O
OH
3 a,b
OH
4 a,b
O
5 a ,b
Scheme 1
Summarization of products created by enzymatic acetylations of
glucose and methyl α-D-glucopyranoside with vinyl acetate or
isoprenyl acetate
Table III
Enzymatic acetylations of glucose by vinyl acetate (VA) and
isopropenyl acetate (IPA) in water
enzyme
acetyl
donor
O
O
O
O
OH
OR
OR
OR
OR
mono-
diacetates reaction
acetates
[%]
time
[%] [days]
Celluclast VA
19.7
2 a : 3 a
12 : 1
0 1
Lipolyve CC IPA 0 0 3
novozym 735 VA
2.0
9.6
3 a
3
not
determined
Amano
Lipase A
IPA
10.0
2 a : 3 a
1:1
4.2
5 a
2
s550
did continue to create only one diacetate (3,6-di-O-acetyl
glucose, 5 a), thus keeping the original specifity for positions
3-O- and 6-O- (Table III). Acetylations of methyl α-Dglucopyranoside
(1 b) with isopropenyl acetate proceeded
with the same positional specifity to produce 2 b and 3 b.
When isopropenyl acetate was replaced by vinyl acetate as
acetyl donor, selectivity increased markedly in favor of 2 b
(Table IV). no reaction was observed when another fungal
lipase – Lipolase 100T – was used as biocatalyst.
Acetylations of 1 b catalyzed by bovine serum albumin
and Ultraflo L (an enzyme cocktail from Humicola insolens)
were unselective, giving mixtures of three monoacetates
(Table IV).
The best results were achieved by use of Celluclast, a
cellulase preparation from Trichoderma reesei RUT C-30
comprising the same acetyl esterase as reported earlier 1 . Acetylations
gave 19.7 % and 10 % of monoacetylated glucose
and methyl glucoside, respectively (Tables III, IV). The selectivity
was exclusively to position 3-O- in acetylation of 1 b
while in acetylation of glucose, almost 8% of 6-O- acetate 3 a
was found in the monoacetate fraction.
Table IV
Enzymatic acetylations of methyl glucoside by vinyl acetate
(VA) and isopropenyl acetate (IPA) in water
enzyme
acetyl
donor
Celluclast IPA
10.0
2 b
Lipolyve CC IPA
2.2
3 b
Lipase AYS IPA
1.9
3 b
Amano
Lipase A
IPA
10.5
2 b : 3 b
2,5 : 1
Amano
Lipase A
VA
6.4
2 b : 3 b
13 : 1
2.1
BSA VA 3 b : 4 b : 2 b
2.0 : 1.3 : 1.0
3.9
Ultraflo L IPA 3 b : 4 b : 2 b
4.5 : 2.5 : 1.0
mono-
diacetates
reaction
acetates
[%]
time
[%] [days]
0 1
0 0.9
0 0.16
1.7
5 b
0.7
5 b
Conclusions
Our results proved Celluclast to be the best catalyst for
acetylations of glucose and methyl α-D-glucopyranoside
according to its selectivity, product yields, availability and
price. Since Celluclast has significantly lower acetyl esterase
activity comparing to the other enzymes tested in this study,
the enzyme seems rather unique. The enzyme selectivity to
position 3-O- gives a promiss of its use in two step enzymatic
1
1
0 5
0 1