Laccase immobilization onto MIL–100 (Fe) and chitosan nanofibers: Fabrication, characterization, and investigation of the potential for bisphenol A removal

Bisphenol A (BPA), a micropollutant in water sources, poses serious environmental and health threats. Due to the limitations of conventional removal methods, enzymatic degradation using laccase has gained attention. This study aimed to enhance laccase stability and reusability by encapsulating it within MIL–100(Fe) metal-organic frameworks (MOFs), followed by immobilization in chitosan nanofibers. The resulting laccase@MIL–100(Fe)@chitosan nanocomposite was evaluated for BPA removal. The enzyme loading capacity was measured, and the activity of the free enzyme and the enzyme immobilized in the nanocomposite matrix was compared at different temperatures, pH levels, and times. The ideal pH for both free and immobilized enzymes in the nanocomposite was found to be 4. The enzyme activity storage time showed that laccase immobilized on a nanocomposite substrate was able to maintain 30 % of its activity over 28 days. Compared to chitosan and MIL–100(Fe)@chitosan, the final composite showed 1.5- and 1.3-times higher removal efficiency, respectively. The nanocomposite removed 94 % of BPA at an initial concentration of 1 mg/L and 90 % at 10 mg/L under optimal conditions (pH 4.0, 30 °C, 12 h), primarily via adsorption. The system retained over 80 % of its removal capacity after five reuse cycles. These findings demonstrate that laccase immobilization in MIL–100(Fe)@chitosan significantly enhances enzymatic degradation of BPA, offering a promising eco-friendly approach for wastewater treatment.