Superior stability and pollutant degradation via chitosan-immobilized laccase: A comparative study with NH₂-MIL-125...

The accumulation of emerging pollutants (EPs) in aquatic environments poses significant threats to both human health and ecosystem integrity, highlighting the urgent need for effective and sustainable remediation strategies. Among the available approaches, biological systems such as laccase-based bioremediation have emerged as a promising greener solution, particularly when the enzyme is immobilized to enhance its stability and reusability. Although laccase immobilization on various carriers have been widely studied, published comparisons of their performance remain limited and insufficiently studied. In this study, we evaluated and compared the degradation efficiency of 15 EPs by laccase immobilized on two supports: chitosan and the metal-organic framework NH₂-MIL-125. Our results showed that laccase immobilized on chitosan exhibited superior thermal and pH stability, along with enhanced recyclability, outperforming both free and MOF-immobilized enzymes. In the presence of a model redox mediator hydroxybenzotriazole (HOBT), chitosan-immobilized laccase achieved complete degradation of paracetamol and 48 % degradation of sulfamethoxazole in 1 h, both of which were not degraded by either free laccase or the MOF-immobilized form. While NH₂-MIL-125 allowed for higher enzyme loading and was easier to handle, it significantly compromised the thermal stability of the enzyme. This study demonstrates, for the first time, the superior performance of laccase immobilized on chitosan, as directly compared to NH₂-MIL-125, for the degradation of a diverse class of EPs. By combining enhanced stability, reusability, and broad pollutant coverage, the system highlights strong potential for large-scale and sustainable wastewater treatment, advancing enzyme-based bioremediation as a practical and environmentally friendly technology.