Immobilization of horseradish peroxidase on electrospun poly(vinyl alcohol)–polyacrylamide blend nanofiber membrane and its use in the conversion of phenol

Abstract

Electrospun nanofibers, with their porous structures, high surface-to-volume ratio, and good mechanical properties, are used as a support material for enzyme immobilization. In this study, the poly(vinyl alcohol) and polyacrylamide bicomponent (PVA–PAAm) nanofibers were fabricated via the electrospinning method. Synthesized PAAm was characterized with size exclusion chromatography (SEC). Nanofibers were characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). DSC and TGA analyses showed that the nanofibers were more durable than PVA and PAAm polymers. SEM images demonstrated that all nanofibers possessed uniform and smooth structures (average diameter about 300 nm). FTIR results have shown that PAAm successfully participates in nanofiber structure. The produced nanofibers were used as support material for covalent immobilization of horseradish peroxidase (HRP). The optimum temperature for free HRP was 45 °C, whereas it was 50 °C for the immobilized enzyme. The immobilized HRP showed better storage and thermal stability than free HRP. The kinetic parameters (K m and V max) were found to be 2.42 mM and 0.027 U for the immobilized HRP and 1.86 mM and 0.079 U for the free HRP, respectively. The immobilized enzyme could be used effectively for 25 cycles with 54% retention of the activity. The immobilized HRP was also used for the conversion of phenol. Phenol removal was found to be about 29.68% at 180 min in real wastewater. The novel PVA–PAAm nanofibrous material was successfully used as a support material for covalent immobilization of HRP. Immobilized enzymes such as oxido-reductases onto the PVA–PAAm bicomponent nanofiber could be recommended in the treatment of organic pollutants in industrial effluents.