Characterization of soybean hull peroxidase immobilized on glycidyl methacrylate copolymers

Abstract

Toxic aromatic pollutants that are found in various industrial wastewaters pose a serious environmental threat. Current methods for phenol removal have certain disadvantages, such as low efficiency, high cost or generation of even more toxic products. On the other hand enzyme-based treatments are highly selective and efficient. Soybean hull peroxidase (SHP) as well as other class III peroxidases catalyzes oxidation reaction in the presence of hydrogen peroxide, resulting in phenol polymerization and formation of less hazardous phenolic polymers. As a by-product of the food industry, soybean hulls are inexpensive and readily available source of large quantities of crude peroxidase. The aim of our research was to isolate SHP from soybean hulls and immobilize it onto a glycidyl methacrylate based carriers using glutaraldehyde method and characterize the resulting product. Immobilized SHP showed dependence upon the pore size of the carrier matrix,with the highest obtained specific activity of 22.8 U g-1 of carrier. Immobilized enzyme proved as an effective phenol removal alternative method with improved thermal and organic solvent stabilities compared to the free form. It also showed greater stability and tolerance to pH fluctuations, showing higher specific activities over a wider pH range. Operational stability was tested by repeated pyrogallol oxidation cycles in a batch reactor. After three cycles, immobilized SHP retained over 60% of the initial activity.