Immobilization of Horseradish Peroxidase on Modified Nylon-6 Fibers

Abstract

Nylon-6 fibers were chemically modified via graft copolymerization reaction to being functionalized and utilized as a carrier for the immobilization of horseradish peroxidase (HRP). First, polyethyl acrylate (PEA) was grafted onto the nylon-6 fibers and the inserted ester groups were transformed to hydrazide groups by treatment with hydrazine hydrate. Then, the obtained hydrazide-containing fibers were activated by glutaraldehyde, which permits the coupling with the HRP protein macromolecules. The modification, activation and HRP immobilization steps were characterized using elemental analysis and FTIR spectra. Also, the morphology of the fibers was visualized by scanning electron microscope (SEM). The optimum pH of the HRP enzyme was found to shift to a higher value compared to the free enzyme. In addition, despite the same optimum temperature displayed by both free and immobilized HRP, the residual activity of the immobilized enzyme was higher than that of the free one at higher temperatures revealing the enhanced thermal stability upon immobilization process. Moreover, the kinetic studies indicated a lower enzyme-substrate affinity upon immobilization. However, the immobilized HRP maintained more than 89% and 55% of its original activity after 5 and 10 reuse cycles, respectively, which could be promising results in the future application in the environmental and biotechnological fields.