Synthesis and Characteristics of Mesoporous Sol-gels for Lipase Immobilization

Abstract

Enzyme cost is the major problem for industrial scale application. Immobilization is a promising approach to moderate the enzyme cost factor and increase its stability and activity. In this study, sol-gel method was used to prepare the immobilization platform and entrapped lipase as one of the most used enzyme in dairy processing, cosmetics and pharmaceutical industries. Lipase from Candida rugosa was immobilized onto glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS) derived sol-gels and its characteristics and hyrdrolytic activity were investigated. Michaelis-Menten kinetic properties reveal that although free enzyme can catalyze the reaction faster, but it has lower affinity for substrate molecules compared to sol-gel immobilized lipase. Entrapped lipase retained 67 % of its initial activity after six reaction cycles. It showed 100% activity compared to free lipase powder at 40-45 °C. In pH 9, as free enzyme lost 90 % of its initial activity, immobilized lipase lost only 29% of its activity. Immobilized enzyme was more stable toward different pHs (100% activity at pH 7.5 compared to free form). Morphological characteristics of the immobilized enzyme were investigated by SEM images and BET. The sample had specific surface area and mean pore diameter of 2.599 m 2 /g and 46.13 nm, respectively.