Enhancement stability and catalytic activity of immobilized α-amylase using bioactive phospho-silicate glass as a novel inorganic support.

α-Amylase enzyme was immobilized on bioactive phospho-silicate glass (PS-glass) as a novel inorganic support by physical adsorption and covalent binding methods using glutaraldehyde and poly glutaraldehyde as a spacer. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) studies confirmed the glass-enzyme linkage. Dissolution of PS-glass in acidic and neutral pH is higher than that of alkaline pH. Some immobilization variables were optimized using statistical factorial design (Central Composite Design). Optimized immobilization variables enhanced the immobilization yield (IY) from 27.9 to 79.9% (2.9-fold). It was found that the immobilized enzyme had higher optimum temperature, higher half-life time (t1/2), lower activation energy (Ea), lower deactivation constant rate (kd) and higher decimal reduction time (D-values) within the temperature range of 40-60°C. Differential scanning calorimetry analysis (DSC) confirmed the thermalstability of the immobilized enzyme. The immobilized enzyme was stable at a wide pH range (5.0-8.0). Kinetic studies of starch hydrolysis demonstrated that immobilized enzyme had lower Michaelis constant (Km), maximum velocity (Vmax) and catalytic efficiency (Vmax/Km) values. The storage stability and reusability of the immobilized enzyme were found to be about 74.7 and 62.5% of its initial activity after 28days and 11cycles, respectively. Enhanced α-amylase stabilities upon immobilization make it suitable for industrial application.