Increasing Stability of a-amylase Obtained from Bacillus subtilis ITBCCB148 by Immobilization with Chitosan

Abstract

In this research, the immobilization of α-amylase from Bacillus subtilis ITBCCB148 by crosslinking method on chitosan matrix has been performed. This research aims to know the effect of immobilization on the thermal stability of α-amylase. The results showed that the native α-amylase has an optimum temperature of  65oC, KM = 1.6 mg mL-1 substrate, and Vmax = 39.7 µmol mL-1 min-1. The immobilized α-amylase has optimum temperature of 75oC, KM = 3.5 mg mL-1 substrate, and Vmax = 7.05 µmol mL-1 min-1. The residual activity of the native and immobilized enzyme on thermal stability test at 65oC for 80 minutes was 58% and 86.15%, respectively. The immobilized enzyme can be reused up to six repeated cycles.The thermodynamic data of native enzyme was t½ = 113.6 min, ki = 6.1x10-3 min-1, and ΔGi = 107.3 kJ mol-1, while the immobilized enzyme was t½ = 433.1 min, ki= 1.6x10-3 min-1, and ΔGi 111.1 kJ mol-1. Based on the decrease of ki, and the increase of ΔGi and half-life(t½) values, the immobilization of α-amylase with chitosan can increase the thermal stability of this enzyme.