The Stability Improvement of α-Amylase Enzyme from Aspergillus fumigatus by Immobilization on a Bentonite Matrix.

The stability of the α-amylase enzyme has been improved from Aspergillus fumigatus using the immobilization method on a bentonite matrix. Therefore, this study aims to obtain the higher stability of α-amylase enzyme from A. fumigatus; hence, it is used repeatedly to reduce industrial costs. The procedures involved enzyme production, isolation, partial purification, immobilization, and characterization. Furthermore, the soluble enzyme was immobilized using 0.1 M phosphate buffer of pH 7.5 on a bentonite matrix, after which it was characterized with the following parameters such as optimum temperature, Michaelis constant (K _M ), maximum velocity (V _max), thermal inactivation rate constant (k _i), half-life (t _1/2), and the change of energy due to denaturation (ΔG _i ). The results showed that the soluble enzyme has an optimum temperature of 55°C, K _M of 3.04 mg mL^-1 substrate, V _max of 10.90 μmole mL^-1 min^-1, k _i of 0.0171 min^-1, t_1/2 of 40.53 min, and ΔG _i of 104.47 kJ mole^-1, while the immobilized enzyme has an optimum temperature of 70°C, K _M of 8.31 mg mL^-1 substrate, V _max of 1.44 μmole mL^-1 min^-1, k _i of 0.0060 min^-1, t _1/2 of 115.50 min, and ΔG _i of 107.37 kJ mole^-1. Considering the results, the immobilized enzyme retained 42% of its residual activity after six reuse cycles. Additionally, the stability improvement of the α-amylase enzyme by immobilization on a bentonite matrix, based on the increase in half-life, was three times greater than the soluble enzyme.