Characterization of β-glucosidase immobilized on chitosan-multiwalled carbon nanotubes (MWCNTS) and their application on tea extracts for aroma enhancement

beta-Glucosidase was covalently immobilized on chitosan-MWCNTs carrier and its aroma enhancement effect in different tea samples was investigated. Chitosan-MWCNTs carrier was prepared by mixing chitosan with MWCNTs (5:1 w/w) and characterization of prepared composite carrier was done by FTIR, TGA and SEM analysis. beta-Glucosidase was covalently immobilized on the composite carrier after glutaraldeyde activation. After optimization of the immobilization conditions, immobilization yield was achieved as 95.22%. Optimum pH was found as pH 6.0 and pH 5.0 for free and immobilized enzyme, respectively. Optimum temperature of the enzyme was shifted from 35 degrees C to 45 degrees C after immobilization. The K-m and V-max values for immobilized beta-glucosidase calculated as 5.55 mM and 7.14 Wing protein respectively. Immobilized beta-glucosidase showed better pH and storage stability than free enzyme. After storage at +4 degrees C for 50 days, the immobilized enzyme retained its 68.4% of the initial activity. The calculated half-life (t(1/2)) of immobilized enzyme was 115.8 min. After 10 cycles of reuse, immobilized beta-glucosidase showed 72.83% of its initial activity. (C) 2016 Elsevier B.V. All rights reserved.