Regioselective hydrolysis of different peracetylated beta -monosaccharides by immobilized lipases from different sources. Key role of the immobilization

The effect of the immobilization strategy
on the activity, specificity and regioselectivity of
three different lipases [those from Thermomyces lanuginose
(TLL), Aspergillus niger (ANL) and Candida
antarctica B (CAL-B)] in the hydrolysis of peracetylated
b-monosaccharides has been evaluated.
Three very different immobilization strategies were
utilized, covalent attachment, anionic exchange and
interfacial activation on a hydrophobic support. The
octyl-TLL immobilized preparation was the most efficient
biocatalyst in the hydrolysis of 1,2,3,4,6-penta-
O-acetyl-beta-D-galactopyranose, producing specifically
6-hydroxy-1,2,3,4-tetra-O-acetyl-beta-D-galactopyranose
in 95% overall yield, whereas the CNBr-TLL preparation
was 48 times slower and regioselective towards
the anomeric position, producing the 1-hydroxy
derivative in 70% yield. The PEI-TLL immobilized
preparation was the most efficient catalyzing
the hydrolysis of 1,2,3,4,6-penta-O-acetyl-beta-D-glucopyranose,
permitting us to obtain up to 70% of the
6-hydroxy product. In the hydrolysis of 2-acetamido-
2-deoxy-1,3,4,6-tetra-O-acetyl-beta-D-glucopyranose, the
octyl-CALB preparation was not selective at all for
the production of monohydroxy products whereas
when CAL-B was immobilized on PEI-agarose, the
enzyme was highly specific and regioselective producing
the 6-hydroxy-2-acetamido-2-deoxy-1,3,4-tri-
O-acetyl-beta-D-glucopyranose in 70% yield.