Over-stabilization of chemically modified and cross-linked Candida antarctica lipase B using various epoxides and diepoxides

Candida antarctica lipase B, Cal-B, was (i) chemically modified with various epoxides or (ii) cross-linked with various diepoxides in order to improve enzyme activity and thermal stability. Modification of the enzyme structure was confirmed by kinetic resolution of p-nitrophenyl acetate with methanol and determination of the kinetic parameters. Thermal stability measurements were carried out for each Cal-B counterpart, proving that Cal-B modified with 1,2-epoxypropane and 1,2epoxypentane, and cross-linked with 1,2,7,8-diepoxyoctane and 1,2,9,10diepoxydecane showed higher stability than soluble enzyme. The influence of the length of the epoxide arm in the modification process, as well as the length of the spacer arm in the cross-linking process, on the final enzyme preparation properties was investigated. The amount of epoxides and diepoxides used for structural rearrangement pronounced an important role for the counterparts’ characteristics. The influence of the precipitant used and presence of additives, such as surfactant or crown-ether, during modification and cross-linking processes was also revealed.