Bioremediation of Congo red using Polyvinyl alcohol - Chitosan Supported Peroxidase as an Efficient and Reusable Catalyst

Abstract

The discharge of textile effluents containing azo dyes is critical due to their persistence in wastewater and carcinogenic, mutagenic impacts on aquatic organisms. Considering the toxicity of azo dye, an effective remediation strategy should be applied before disposing into the environment. Among all the advance techniques like electrochemical degradation, fenton oxidation, photocatalysis, ozonation etc., biodegradation using biocatalyst found to be an eco-friendly and economic process to deal with this problem. Along with advantages, biocatalysts particularly enzymes face limitations like instability, single-use restriction, and reduced efficiency under operational conditions. Immobilization addresses these challenges by enhancing enzyme stability, reusability, and catalytic performance. The present study focuses on the development of an efficient bioremediation approach for the removal of Congo red dye from aqueous solutions using peroxidase (HGP) extracted from germinated Macrotyloma uniflorum (horse gram) seedlings. The enzyme was immobilized on polyvinyl alcohol–chitosan beads through epichlorohydrin-mediated crosslinking, enabling its application as a reusable biocatalyst for dye degradation. The immobilization method achieved high efficiency with 96% enzyme retention. The immobilized peroxidase exhibited enhanced stability and was evaluated for its efficacy in degrading Congo red dye. Under optimized conditions, 26 units of immobilized peroxidase achieved complete decolorization (100%) of a 160 mg/L Congo red solution within 10 minutes at 28°C and pH 4. Environmental safety of the degradation products was confirmed through phytotoxicity and microbial growth assessments. Additionally, the immobilized enzyme retained its catalytic activity across eight successive cycles, underscoring its reusability and potential for practical applications in bioremediation of dye-contaminated wastewater.