Treatment of Starch Wastewater by α‐Amylase Immobilized on Silica Infused Magnetite Nanoparticles for Maltose Syrup Preparation

Abstract Casein decorated silicainfused magnetite (Fe 3 O 4 ‐SiO 2 ) nanoparticles are employed to immobilize commercial α‐amylase, where glutaraldehyde serves as a cross linker. The optimal concentration of variables, such as casein (1.4%w/v), Fe 3 O 4 ‐SiO 2 (106 µl), glutaraldehyde (55µl) and amylase (1 mg/ml) are defined by a Box Behnken design. The binding of casein, glutaraldehyde and enzyme over the nanoparticles are further confirmed structurally by fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). The loading capacity is 37 µg amylase over 1 µg of silica infused magnetite nanoparticles. The optimum pH for the catalysis of soluble and immobilized amylases is the same, i.e. pH 7. However, the pH range for catalysis is improved upon immobilization. The temperature optimum of soluble and immobilized amylases are 40 and 70 °C, respectively. The amylase stability is improved upon immobilization, as shown by enhanced half‐life and reduced deactivation rate constant. The immobilized amylase is used for 17 consecutive cycles with retention of 52% of the residual activity. The immobilized amylase produces high maltose syrup using the industrial wastewater containing corn starch. The ISO 5377 protocol determines dextrose equivalence values to be 36% and 24% during cycle 1 and cycle 2, respectively. The findings point out its possible commercial use.