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  65^oC, K_M = 1.6 mg mL^-1 substrate, and V_max = 39.7 µmol mL^-1 min^-1. The immobilized α-amylase has optimum temperature of 75^oC, K_M = 3.5 mg mL^-1 substrate, and V_max = 7.05 µmol mL^-1 min^-1. The residual activity of the native and immobilized enzyme on thermal stability test at 65^oC 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 t_½ = 113.6 min, k_i = 6.1x10^-3 min^-1, and ΔG_i = 107.3 kJ mol^-1, while the immobilized enzyme was t_½ = 433.1 min, k_i= 1.6x10^-3 min^-1, and ΔG_i 111.1 kJ mol^-1. Based on the decrease of k_i, and the increase of ΔG_i and half-life(t_½) values, the immobilization of α-amylase with chitosan can increase the thermal stability of this enzyme.