Cross-Linked and Encapsulated Laccase from Trametes sp.: Optimized Degradation of Bisphenol A and Diclofenac in Aqueous Solution

Abstract

Abstract

The presence of micropollutants, such as bisphenol A (BPA) and diclofenac, poses significant environmental challenges, as conventional treatment methods are often ineffective in degrading them. This study examined the potential of laccase from the white-rot fungus Trametes sp. to degrade these micropollutants. To enhance stability and reusability, laccase was cross-linked with glutaraldehyde and subsequently encapsulated within calcium alginate beads. The immobilized cross-linked laccase demonstrated enhanced stability, retaining 66% of its activity at 70°C compared to only 42% for free laccase. Furthermore, cross-linking led to a fourfold reduction in enzyme leakage and a 1.4-fold increase in activity recovery. The stabilized laccase was then evaluated for BPA and diclofenac removal (25 ppm each) under optimal conditions (pH=5, 30°C, 10 U/mL enzyme activity), achieving 97% removal within 5 hours for BPA and 6 hours for diclofenac. Reusability testing showed the immobilized enzyme retained over 40% of its initial removal efficiency after seven cycles. Kinetic analysis revealed an increased Km (1.172 mM) and decreased Vmax (0.256 mM/min) for the immobilized laccase, indicating diffusion limitations imposed by the support matrix. Structural and stability characteristics were confirmed using scanning electron microscopy. In summary, this study demonstrates the significant potential of stabilized, cross-linked laccase for the efficient environmental remediation of hazardous micropollutants.