α-amylase immobilized on magnetic nanoparticles: reusable robust nano-biocatalyst for starch hydrolysis

Immobilization of enzymes on magnetic nanoparticles (MNPs) could offer reusability along with increased stability and robust operation at different physicochemical conditions. In this work, magnetically recoverable nano-biocatalyst was prepared by immobilizing industrially important alpha-amylase on chitosan coated Fe3O4 MNPs (AMNPs) and evaluated for its activity and stability. MNPs were characterized by x-ray diffraction, field emission scanning electron microscope and vibrating sample magnetometer. Functional groups on MNPs and chitosan coated MNPs along with immobilization of alpha-amylase on chitosan coated MNPs were analyzed by Fourier transform infrared spectroscopy. Amount of immobilized alpha-amylase was optimized by varying enzyme concentration and incubation time during immobilization process. The activity and stability of the AMNPs and free alpha-amylase were investigated. It was found that AMNPs have better starch digestion capacity at different physicochemical conditions than that of free alpha-amylase. The immobilized enzyme retained 66% activity after 20 days compared to 18% activity of the free enzyme. AMNPs were reused for 20 times, without significant loss of activity, by magnetically separating the nano-biocatalyst from the reaction mixture after each starch hydrolysis cycle.