Xanthine oxidase driven bio-Fenton system for advanced pollutant degradation in sustainable wastewater treatment

Advanced oxidation processes such as the Fenton reaction are critical for degrading recalcitrant pollutants in wastewater but face operational bottlenecks. The classical Fenton process relies on hazardous exogenous H₂O₂, inefficient Fe²⁺/Fe³⁺ cycling, and stringent acidic pH, limiting scalability. To address these limitations, this study introduces a sustainable hybrid system integrating human xanthine oxidase (Hu-XO) with Fenton chemistry, enabling self-sufficient H₂O₂ generation, Fe redox cycling, and pH modulation. The Hu-XO-driven hypoxanthine/xanthine oxidation produced H₂O₂ and superoxide radicals, synergizing with Fe²⁺ to amplify hydroxyl radical generation. When optimized via response surface methodology (95 % model accuracy), the system achieved 91.8 % biochemical oxygen demand (BOD) and 86.0 % chemical oxygen demand (COD) reduction in tannery wastewater. The antimicrobial assay using Escherichia coli and Bacillus subtilis demonstrated a removal rate of up to 10⁶ CFU/mL. Posttreatment toxicity assays revealed an 80 % decrease in Aliivibrio fischeri luminescence inhibition and restored seed germination rates for Vigna mungo, Vigna radiata, and Cicer arietinum. This work establishes a self-sustaining Fenton-based system that eliminates exogenous H₂O₂ dependence and strict pH requirements and integrates pollutant degradation with antimicrobial action, offering a scalable, eco-friendly strategy for industrial wastewater remediation.