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

β-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 (5:1w/w) and characterization of prepared composite carrier was done by FTIR, TGA and SEM analysis. β-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°C to 45°C after immobilization. The Km and Vmax values for immobilized β-glucosidase calculated as 5.55mM and 7.14U/mg protein respectively. Immobilized β-glucosidase showed better pH and storage stability than free enzyme. After storage at +4°C for 50days, the immobilized enzyme retained its 68.4% of the initial activity. The calculated half-life (t1/2) of immobilized enzyme was 115.8min. After 10 cycles of reuse, immobilized β-glucosidase showed 72.83% of its initial activity.