The Effect of Zeolite/Chitosan Hybrid Matrix for Thermal-stabilization Enhancement on the Immobilization of Aspergillus fumigatus α-Amylase

Abstract

In this paper, the A. fumigatus α-amylase had been immobilized onto zeolite/chitosan hybrid to improve its thermal-stabilization for industrial needs. The methods applied enzyme production, isolation, partial purification, immobilization, and characterization. The optimum temperatures of the native and immobilized enzymes were 50 and 55˚C, respectively. The native enzyme has KM of 3.478 ± 0.271 mg mL-1 substrate and Vmax of 2.211± 0.096 µmole mL-1 min-1, while the immobilized enzyme has KM value of 12.051 ± 4.949 mg mL-1 substrate and Vmax of 1.602 ± 0.576 µmole mL-1 min-1. The residual activity of the immobilized enzyme retained up 10.97% after fifth reuse cycles. The native enzyme has ΔGi of 104.35 ± 1.09 kJ mole-1 and t½ of 38.75 ± 1.53 min, while the immobilized enzyme has ΔGi of 108.03 ± 0.05 kJ mole-1 and t½ of 180.03 ± 3.31 min. According to the increase in half-life (t½), stability improvement of the A. fumigatusα-amylase was 4.65 times greater than the native enzyme. Thus, the zeolite/chitosan hybrid is used as a new supporting matrix for further enzyme immobilization to stabilize the enzymes. Doi: 10.28991/ESJ-2022-06-03-06 Full Text: PDF

Immobilization and Stabilization of Aspergillus Fumigatus α-Amylase by Adsorption on a Chitin

“…This variable was determined since each enzyme has a temperature range, known as optimum temperature, for achieving the maximum rate of reaction [2]. According to the previous findings, the optimum temperature of the A. fumigatus α-amylase was in the range of 50-55 o C, but higher range was reported after immobilization [5,22,24]. In this present study, determination of optimum temperature was carried out by performing the experiments at different incubation temperatures as specified in Mandel's assay, which are 50, 55, 60, 65, 70, and 75 o C. The experiments were run for 30 min, and the incubation temperature at which the highest enzyme activity was achieved was taken as the optimum temperature.…”

“…In addition, this enzyme exhibits the ability to control starch de-polymerization, working at physiological pH and temperature conditions, preventing the formation of side products such as 5-hydroxy-2-methylfurfuraldehyde. The ability to fix the color and taste of the product, reduce activation energy, and unnecessary purification process are other advantageous features of α-amylase [3][4][5].…”

“…Previous workers reported a method to improve the stability of α-amylase isolated from Aspergillus sp. using an enzyme mobilization method, which means improvement of α-amylase stability is possible [5]. The A. oryzae α-amylase was reported to have optimum temperature of 45 o C and its activity decreased significantly at 60 o C [4].…”

“…The A. oryzae α-amylase was reported to have optimum temperature of 45 o C and its activity decreased significantly at 60 o C [4]. Slightly higher optimum temperature (50 o C) was reported for the A. fumigatus α-amylase but it showed a significant decrease of the activity to only 21.50% when applied at 60°C for 80 min [5].…”

“…After immobilization, the enzyme was found to become more resistant to thermal denaturation, as indicated by increased energy required for the thermal denaturation from 108.27 to 111.21 kJ mole -1 [12]. In another study, significant improvement of thermal stability of the A. fumigatus α-amylase immobilized on zeolite/chitosan hybrid was reported, as indicated by increased of ΔGi from 104.35 to 108.03 kJ mole -1 , and extension of half-life from 38.75 to 180.03 min [5].…”