Enhanced dye decolorization efficiency of gellan gum complexed Ziziphus mauritiana peroxidases in a stirred batch process

Abstract

Peroxidases from Ziziphus mauritiana leaves were immobilized via complexation with gellan gum, followed by crosslinking. The impact of combined complexation-crosslinking approach on the activity and stability of the peroxidases was studied by employing the biocatalyst for the degradation of acid black 1. As compared to free peroxidases, complexed and crosslinked peroxidases displayed significantly higher pH and thermal stability. Immobilized peroxidases showed a 3-fold enhancement in thermal stability upon incubation at 60 °C for 2 h. Immobilized peroxidases retained a promising reusability of about 67% when applied for 8 repeated cycles of acid black 1 decolorization and displayed higher catalytic activity than free enzyme when employed in a stirred batch process. Putative degradation scheme of acid black 1 was proposed with the help of degradation products identified by gas chromatography–mass spectrometry which confirmed the degradation of the dye into smaller molecular weight metabolites. Molecular docking studies of peroxidases with gellan gum revealed the binding site of gellan gum resides far away from the active site of the enzyme.