β-d-Galactosidase is an important enzyme in the dairy industry, and the enzyme from the yeast Kluyveromyces lactis is most widely used. Here, we report immobilization of the enzyme on a silica/chitosan composite support, devised to have 10% and 20% chitosan (SiQT10 and SiQT20, respectively). Morphological and textural characterizations showed that chitosan is dispersed in micrometric regions in silica. For comparison, a silica organofunctionalized with 3-aminopropyltrimethoxysilane (SiO2aptms) was prepared. Performance of the biocatalysts was tested for lactose hydrolysis, and the enzyme immobilized in SiQT10 and SiQT20 composites showed higher efficiency (62% and 47%, respectively) compared with the enzyme in SiO2aptms. Operational stability in this system was evaluated for the first time. After 200 h of continuous use in a fixed-bed reactor, SiQT10 remained with approximately 90% activity. Thus, in addition to demonstrating compatibility for food processing, these results align the enzyme stabilization properties of chitosan with the mechanical resistance of silica.
Keywords: Biocatalysis; Continuous operation system; Enzyme immobilization; Heterogeneous biocatalyst; Inorganic-organic composite materials; Lactose hydrolysis reaction.
Copyright © 2017 Elsevier Ltd. All rights reserved.