The stability of the α-amylase enzyme has been improved from Aspergillus fumigatus using the immobilization method on a bentonite matrix. Therefore, this study aims to obtain the higher stability of α-amylase enzyme from A. fumigatus; 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 (KM), maximum velocity V max , thermal inactivation rate constant (ki), half-life (t1/2), and the change of energy due to denaturation (ΔGi). The results showed that the soluble enzyme has an optimum temperature of 55°C, KM of 3.04 mg mL−1 substrate, V max of 10.90 μmole mL−1 min−1, ki of 0.0171 min−1, t1/2 of 40.53 min, and ΔGi of 104.47 kJ mole−1, while the immobilized enzyme has an optimum temperature of 70°C, KM of 8.31 mg mL−1 substrate, V max of 1.44 μmole mL−1 min−1, ki of 0.0060 min−1, t1/2 of 115.50 min, and ΔGi 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 α-amylase enzyme by immobilization on a bentonite matrix, based on the increase in half-life, was three times greater than the soluble enzyme.

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 (KM), maximum velocity V max , thermal inactivation rate constant (ki), half-life (t1/2), and transformation of free energy because of denaturation (ΔGi). The free enzyme has optimum temperature of 55°C, KM = 3.04 mg mL−1 substrate, V max = 10.90   μ molemL − 1 min − 1 , ki = 0.0171 min−1, t1/2 = 40.53 min, and ΔGi = 104.47 kJ mole−1. Meanwhile, the immobilized enzyme has optimum temperature of 60°C, KM = 11.57 mg mL−1 substrate, V max = 3.37   μ molemL − 1 min − 1 , ki = 0.0045 min−1, t1/2 = 154.00 min, and ΔGi = 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.

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

Green waste (GW) is an important fraction of municipal solid waste (MSW). The composting of lignocellulosic GW is challenging due to its low decomposition rate. Therefore the use of fungi inoculum as a decomposer inducer on GW composting needs to study. The purpose of this study was to explore the potential of the compost induced by cellulolytic (Aspergillus fumigatus) and ligninolytic fungi (Geotrichum sp.) inoculum application on vegetative growth of red chilly plants (Capsicum annuum l.). This research was conducted in the green house of the Faculty of Agriculture the University of Lampung, Indonesia. Completely Randomized Design was adopted with five treatment dose of cellulolytic and ligninolytic compost amandmend of 0%, 10%, and 20% each (K= control, S1= Cellulose 10%, S2= cellulose 20%, L1= Ligninolytic 10% and L2= ligninolytic 20%). Parameters observed were plant height, dry weight, relative water content and chlorophyll of a, b and total. The results demonstrated that compost induced by cellulolytic fungi (Aspergilus fumigatus) and ligninolytic (Geotrichum sp) produced the optimal effect on growth parameters across all treatments. The compost application could increase significantly plant height, dry weight, relative water content. But not the chlorophyll content of a, b and total. The maximum measurements of plant height, dry weight, relative water content was achieved by S2, L2, L2, K and L2 treatments respectively. These results suggest that the inoculum induced compost has bene cial impacts for the use as organic fertilizer to enhance vegetative growth.

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