Magnetically recyclable co-immobilized laccase–glucose oxidase nanobiocatalyst for sustainable cleaning of fouled polypropylene membranes

Introduction Membrane fouling remains a major challenge limiting the efficiency and sustainability of membrane-based water and wastewater treatment systems. Therefore, the development of effective and reusable biocatalytic cleaning systems is essential for improving membrane performance and extending membrane operational lifespan. Methods In this study, laccase and glucose oxidase were co-immobilized onto chitosan-coated magnetic iron oxide nanoparticles using the combined cross-linked enzyme aggregate (combi-CLEAs) approach for cleaning organically fouled polypropylene membranes. Maximum enzyme loading values of 189.56 U mg −1 for laccase and 185.69 U mg −1 for glucose oxidase were obtained under optimized immobilization conditions. Results and Discussion The immobilized enzymes exhibited improved pH and thermal stability and retained 69.24% and 77.89% residual activity for laccase and glucose oxidase, respectively, after ten reuse cycles. Following enzymatic treatment, membrane volumetric flux increased nearly three-fold from 32.48 ± 0.31 to 108.40 ± 1.31 L m −2 h −1 . In addition, significant reductions in adenosine triphosphate, total organic carbon, and chemical oxygen demand were observed after treatment, indicating effective removal of biomass-associated and organic foulants. The results demonstrate the potential applicability of co-immobilized oxidoreductase nanobiocatalysts as sustainable membrane-cleaning systems.