Immobilization of Amylases via Adsorption on Agar-Coated Magnetic Nanoparticles

Abstract

In this study, a new method for simultaneous synthesis and coating of magnetic iron oxide nanoparticles was employed, where ferric and ferrous ions were co-precipitated within an aqueous solution containing agar at room temperature under inert atmosphere. X-ray diffraction (XRD) analysis indicated that synthesized nanoparticles were pure Fe3O4 with a cubic structure and crystallite size ranging between 9.38 and 10.11 nm. The scanning electron microscope (SEM) images demonstrated the increasing surface roughness as concentration of surface coating material increased. The produced magnetic particles were used as a support for α−amylase immobilization by adsorption method. Effects of sonication, immobilization time (0.5; 1; 2; 4; 8; 16 h) concentration of surface coating material (0; 0.5; 1% w/v agar), immobilization pH (pH 3,4,5,6,7) on protein loading, enzyme activity and specific activity were investigated. Sonication did not enhance amylase immobilization. Based on the specific activity of the enzyme, the optimum adsorption was achieved at pH 4 and 5 after 4h-immobilization time, where, compared to the free α−amylase, a 3-fold increase in specific activity and 360% increase in relative activity was measured, respectively.