Immobilization of peroxidase on polypyrrole-cellulose-graphene oxide nanocomposite via non-covalent interactions for the degradation of Reactive Blue 4 dye

Abstract

In the present study novel polypyrrole-cellulose-graphene oxide nanocomposite (PCeGONC) was employed for the immobilization of ginger peroxidase (GP) via simple adsorption mechanism. Immobilization of enzyme on the obtained support resulted in enhancement of the enzyme activity. The recovery of activity was 128% of the initial activity. Consequently, in 3 h stirred batch treatment, PCeGONC bound GP exhibited higher decolorization efficiency (99%) for Reactive Blue 4 (RB 4) dye as compared to free GP (88%). The immobilized GP exhibited higher operational stability and retained approximately 72% of its initial activity even after ten sequential cycles of dye decolorization in batch process. The kinetic characterization of PCeGONC bound GP revealed slightly lower Km and 3.3 times higher Vmax compared to free GP. Degraded products were identified on the basis of GC-MS analysis and degradation pathway was proposed accordingly which confirms enzymatic breakdown of RB 4 into low molecular weight compounds. Genotoxic assessment of GP treated RB 4 revealed significant reduction of its genotoxic potential. In-silico analysis identified that binding site of PCeGONC on enzyme is distinct and lies far away from the active site of the enzyme. Furthermore, it also revealed higher affinity of 1-hydroxybenzotriazole (a redox mediator) and RB 4 for PCeGONC bound enzyme as compared to the free enzyme. This is in consensus with the observed decrease in Km of the immobilized GP.