Regioselective Hydrolysis of Different Peracetylated β‐Monosaccharides by Immobilized Lipases from Different Sources. Key Role of The Immobilization

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Abstract
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 β‐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‐β‐D‐galactopyranose, producing specifically 6‐hydroxy‐1,2,3,4‐tetra‐O‐acetyl‐β‐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‐β‐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‐β‐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‐β‐D‐glucopyranose in 70 % yield.