Immobilization of Horseradish Peroxidase on Macroporous Glycidyl-Based Copolymers with Different Surface Characteristics for the Removal of Phenol

Abstract

Novel macroporous copolymers of glycidyl methacrylate and ethylene glycol dimethacrylate with mean pore size diameters ranging from 150 to 310 nm were synthesized by dispersion polymerization and modified with ethylenediamine. The glutaraldehyde and periodate method were employed to immobilize horseradish peroxidase (HRP) onto these carriers. The activity of the immobilized enzyme was greatly affected by the pore size of the carrier. The highest specific activities of 9.65 and 8.94 U/g of dry weight were obtained for HRP immobilized by the periodate-route onto poly(GMA-co-EGDMA) carriers with pore size diameters of 234 and 297 nm, respectively. Stability studies showed an improved operational stability of immobilized peroxidase at 65 degrees C and in an organic solvent. HRP immobilized on a copolymer with a pore size of 234 nm, showing the highest specific activity and good stability, had higher activities at almost all pH values than the native enzyme and the increased K-m value for pyrogallol oxidation. Immobilized HRP retained 80% of its original activity after five consecutive cycles of the pyrogallol oxidation and 98% of its initial activity in a storage stability study. Enzyme immobilized onto the macroporous copolymer with the pore size diameter of 234 nm showed a substantial degree of phenol removal achieved by immobilized peroxidase.