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.