Stability enhancement of Bacillus subtilis ITBCCB148 originating α-amylase by immobilization using chitin
This study aimed to analyze the influence of chitin as immobilization agent on the stability of purified α-amylase obtained from Bacillus subtilis ITBCCB148, which was immobilized the adsorption method. A series of characterization of immobilized and purified enzymes was conducted to determine optimum temperature, pH, KM, Vmax, thermal stability, and reusability of immobilized enzyme. The enzymatic activity of free and immobilized α-amylase was determined on the basis of glucose formed using Mandels method, and protein content using the Lowry method. The experimental data demonstrated that the immobilized α-amylase can be used up to five times and has an optimum temperature of 75°C, KM=6.04 mg.mL−1 substrate, and Vmax=1277.14 µmol.mL−1 min−1. Stability test conducted at 65°C for 80min indicated that the immobilized enzyme has 76.26% residual activity, which is equivalent to the unit activity of 582.61 U/mL. Purified enzyme had an optimum temperature of 65°C, KM of 1.9 mg/mL substrate, and Vmax of 3,508.77 µmol/mL.min-1. Stability test performed at 65°C for 80min indicated that the residual activity of the native enzyme results in a stability test at 65°C for 80 min was 15.50% with a unit activity of 42.34 U/mL. The immobilized enzyme had t1/2-value=346.5 min, ki=0.002 min−1, and ΔGi was 115.51 kJ.mol−1, while for the purified enzyme, tha data obtained were t½=28.88 min, ki=0.024 min−1, and ΔGi=105.14 kJ.mol−1. Increased stability of the enzyme as a result of immobilization was also indicated by decreased value of ki and increased values of ΔGi and t½.
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