Catalytic capabilities of lipase immobilized into organically modified silicates by sol-gel method

The capabilities of Candida rugosa lipase, which was immobilized into organically modified silicates formed on kieselguhr such as Celite 545 are investigated in esterification of (-)- or (+)-menthol with butyric acid. In this study, we optimized the preparation conditions such as a molar ratio of precursors. From these investigations, we find that the optimized hybrid gel-immobilized lipase is derived from a mixture of dimethyldimethoxysilane and tetramethoxysilane at a molar ratio of 4 : 1 and its enantioselectivity, which is defined as a ratio of the initial reaction rate of (-)-menthol to that of (+) -menthol, is enhanced up to 41 at 75 degreesC. In addition, we observe the temperature dependence of these immobilized lipases. Consequently, the optimized hybrid gel-immobilized lipase shows higher activity than deposited lipase on Celite at all temperatures, and it is suggested that this activation results from a remarkable enhancement of the V-max value.