The Stability Improvement of -Amylase by Immobilization onto Chitin-Bentonite Hybrid.

Enzyme immobilization is a powerful method to improve the stability, reuse, and enzymatic properties of enzymes. The immobilization of the -amylase enzyme from on a chitin-bentonite (CB) hybrid has been studied to improve its stability. Therefore, this study aims to obtain the higher stability of -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 ( ), maximum velocity ( ), thermal inactivation rate constant ( ), half-life ( ), and transformation of free energy because of denaturation (Δ ). The free enzyme has optimum temperature of 55°C,  = 3.04 mg mL substrate, =10.90 molemLmin,  = 0.0171 min,  = 40.53 min, and Δ  = 104.47 kJ mole. Meanwhile, the immobilized enzyme has optimum temperature of 60°C,  = 11.57 mg mL substrate, =3.37 molemLmin,  = 0.0045 min,  = 154.00 min, and Δ  = 108.17 kJ mole. After sixth cycle of reuse, the residual activity of the immobilized enzyme was 38%. The improvement in the stability of -amylase immobilized on the CB hybrid based on the increase in half-life was four times of the free enzyme.