Immobilization of Pleurotus nebrodensis WC 850 laccase on glutaraldehyde cross-linked chitosan beads for enhanced biocatalytic degradation of textile dyes

Abstract

Immobilized laccases with aggrandized catalytic activity and stability have demonstrated potential applicability in wastewater treatment. Herein, a purified laccase from Pleurotus nebrodensis WC 850 was effectively immobilized onto high-quality spherical chitosan beads using the cross-linking method. The maximum immobilization yield was achieved by chitosan beads developed using a 2.5 % chitosan solution after 6 h of incubation in 1.0 % glutaraldehyde solution. The detection of copper by EDX analysis confirmed the occurrence of the enzyme in the laccase coupled beads. Chitosan-immobilized laccase (CTS-Lac) performed over wide working pH and temperatures with an optimum pH of 7.0 and 50 °C. Kinetic parameters Km and Vmax for CTS-Lac were calculated to be 120 μM and 597 U/mL, respectively. CTS-Lac achieved high decolorization efficiencies for different reactive and disperse dyes (83–90 %). Preservation of 84.19 % and 54.21 % of its initial activity after 3 and 8 consecutive dye removal cycles indicates a stable dye degradation performance in the repeated batches. After treatment with the enzymes, BOD, COD, and TOC levels were reduced to 92.25–96.55 %, 91.90–94.94, and 77.01–93.29 %, respectively, in the dye solutions. Conclusively, immobilized laccase treatment might appear a good choice for bioremediation of dye-laden industrial wastewater due to substantial degradation and appreciable improvement in water quality parameters.