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

Abstract

The stability of the <i>α</i>-amylase enzyme has been improved from <i>Aspergillus fumigatus</i> using the immobilization method on a bentonite matrix. Therefore, this study aims to obtain the higher stability of <i>α</i>-amylase enzyme from <i>A. fumigatus</i>; 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 (<i>K</i> _<i>M</i> ), maximum velocity (<i>V</i> _max), thermal inactivation rate constant (<i>k</i> _i), half-life (<i>t</i> _1/2), and the change of energy due to denaturation (Δ<i>G</i> _<i>i</i> ). The results showed that the soluble enzyme has an optimum temperature of 55°C, <i>K</i> _<i>M</i> of 3.04 mg mL^-1 substrate, <i>V</i> _max of 10.90 <i>μ</i>mole mL^-1 min^-1, <i>k</i> _i of 0.0171 min^-1, t_1/2 of 40.53 min, and Δ<i>G</i> _<i>i</i> of 104.47 kJ mole^-1, while the immobilized enzyme has an optimum temperature of 70°C, <i>K</i> _<i>M</i> of 8.31 mg mL^-1 substrate, <i>V</i> _max of 1.44 <i>μ</i>mole mL^-1 min^-1, <i>k</i> _i of 0.0060 min^-1, <i>t</i> _1/2 of 115.50 min, and Δ<i>G</i> _<i>i</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 <i>α</i>-amylase enzyme by immobilization on a bentonite matrix, based on the increase in half-life, was three times greater than the soluble enzyme.