Different derivatives of a lipase display different regioselectivity in the monohydrolysis of per-O-acetylated 1-O-substituted-β-galactopyranosides

Different immobilized preparations of three different lipases – those from Aspergillus niger (ANL), Candida rugose (CRL) and Candida antarctica B (CAL-B) – have been used in the regioselective monohydrolysis of different peracetylated-β-galactopyranosides. Three very different immobilization strategies – covalent attachment, anionic exchange and interfacial activation on a hydrophobic support – were employed for each lipase. The role of the immobilization strategy on the hydrolytic activities, specificities and regioselectivities of the lipases were investigated. Moreover, the effect the biocatalysts performance of the presence of different moieties in the anomeric position of the substrate was analyzed. The PEI-ANL immobilized preparation was six times more active than the CNBr-ANL in the hydrolysis of 1-thioisopropyl-2,3,4,6-tetra-O-acetyl-β-d-galactopyranoside whereas the CNBr-ANL showed 2 times more activity than the PEI-ANL in the hydrolysis of galactal. Using CRL, the octyl-CRL was completely specific and regioselective in the hydrolysis of galactal, producing the C-6 monohydroxylated product in 99% yield. The PEI-CRL showed low specificity and poor regioselectivity, hydrolyzing in C-6 but also in C-3 positions whereas the PEI-CRL preparation showed good specificity although low regioselectivity, hydrolyzing in C-6, C-4 and C-3 positions.