Development and Application of a Hybrid Support of Laccase from Trametes versicolor with Zinc Oxide Nanoparticles for Textile Dye Degradation

A hybrid support based on sodium alginate and green-synthesized ZnO nanoparticles was developed for the immobilization of laccase (Trametes versicolor) and applied to textile dye degradation. ZnO nanoparticles were biosynthesized using pecan shell (Carya illinoinensis) extract in combination with a zing precursor salt (Zn-(NO3)2·6H2O) and characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-AR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), confirming their structural and morphological features. Laccase was entrapped in sodium alginate beads and cross-linked with divalent cations (0.2 M CaCl2, BaCl2 or CuSO4) supplemented with glutaraldehyde (100 μL of 50% v/v) during bead formation; beads were kept in the cross-linking solution for 60 min, washed and stored at 4 °C. Immobilized systems were evaluated for immobilization yield, efficiency, enzyme leakage, and storage stability. Among the tested agents, Cu2+ provided the highest immobilization efficiency (52%) with reduced enzyme leakage. The hybrid support containing ZnO nanoparticles (Alg + ZnO-NPs@Lac) exhibited remarkable improvements in enzyme stability, maintaining 153% of its initial activity after 35 days, compared to only 68% for alginate without ZnO. The immobilized biocatalyst demonstrated enhanced tolerance to pH and temperature variations and achieved up to 86% degradation of Reactive Blue 198 under optimized conditions. These findings highlight the synergistic effect of ZnO nanoparticles in strengthening the mechanical and thermal resistance of the alginate matrix and improving laccase stability, offering a sustainable and efficient platform for the enzymatic treatment of textile dyes and emerging micropollutants in wastewater.