The Stability Improvement of Aspergillus fumigatus alpha-Amylase by Immobilization onto Chitin-Bentonite Hybrid
Biochem Res Int. 2022 Mar 14;2022:5692438. doi: 10.1155/2022/5692438. eCollection 2022.
Enzyme immobilization is a powerful method to improve the stability, reuse, and enzymatic properties of enzymes. The immobilization of the α-amylase enzyme from Aspergillus fumigatus on a chitin-bentonite (CB) hybrid has been studied to improve its stability. Therefore, this study aims to obtain the higher stability of α-amylase enzyme to reduce industrial costs. The procedures were performed as follows: production, isolation, partial purification, immobilization, and characterization of the free and immobilized enzymes. The CB hybrid was synthesized by bentonite, chitin, and glutaraldehyde as a cross-linker. The free enzyme was immobilized onto CB hybrid using 0.1 M phosphate buffer pH 7.5. The free and immobilized enzymes were characterized by optimum temperature, Michaelis constant (K M), maximum velocity (V max), thermal inactivation rate constant (k i ), half-life (t 1/2), and transformation of free energy because of denaturation (ΔG i ). The free enzyme has optimum temperature of 55°C, K M = 3.04 mg mL-1 substrate, V max=10.90 μmolemL-1min-1, k i = 0.0171 min-1, t 1/2 = 40.53 min, and ΔG i = 104.47 kJ mole-1. Meanwhile, the immobilized enzyme has optimum temperature of 60°C, K M = 11.57 mg mL-1 substrate, V max=3.37 μmolemL-1min-1, k i = 0.0045 min-1, t 1/2 = 154.00 min, and ΔG i = 108.17 kJ mole-1. After sixth cycle of reuse, the residual activity of the immobilized enzyme was 38%. The improvement in the stability of α-amylase immobilized on the CB hybrid based on the increase in half-life was four times of the free enzyme.