The immobilization of penicillin G acylase on modified TiO2 with various micro-environments

Abstract

Immobilization of penicillin G acylase (PGA) on carriers is an effective strategy for running away from the drawbacks of free PGA. In this work, modified TiO2 was employed as a carrier for the immobilization of PGA. Firstly, TiO2 was used as a nucleus and modified by two different approaches, one-step modification and two-step modification, to construct and regulate the micro-environment of carrier, particularly by changing the type of functional immobilization groups, and the arm-length of immobilization sites. In the one-step modification approach, TiO2 was altered by glutaraldehyde, 3-glycidoxypropyltrimethoxysilane (3-GCDPTMS) and 3-aminopropyltriethoxysilane (3-APTMS), separately; while in the two-step modification approach, primary TiO2 was firstly altered with a small amount of glutaraldehyde or 3-GCDPTMS, then followed by a secondary modification process using glutaraldehyde and 3-GCDPTMS, respectively. Secondly, the influence of the micro-environments of carrier on the catalytic performance of immobilized PGA, in terms of enzyme loading capacity (ELC), enzyme activity (EA) and activity retention ratio (EAR) was investigated. Results revealed that PGA immobilized on carrier modified by 3-GCDPTMS, with a graft rate of 30 % had the best performance, which had an ELC of 10,800 U, EA of 14,900 U/g. Both of the functional group and arm-length of immobilization site had influence on the catalytic performance of immobilized PGA, and the functional groups of immobilization site was the most essential one responsible for stabilizing PGA and improving its catalytic activity. Then PGA immobilized carrier with longer arm-length had better catalytic performance.