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

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 degrees C. Kinetic parameters K-m and V-max for CTS-Lac were calculated to be 120 mu M 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.

Automated summary

Immobilized laccases have shown potential application in wastewater treatment due to enhanced catalytic activity and stability. Immobilization of laccase on high-quality spherical chitosan beads using the cross-linking method was effective, with the enzyme showing high decolorization efficiencies and stable dye degradation performance in repeated cycles. The treatment with immobilized laccase resulted in significant reductions in BOD, COD, and TOC levels in dye solutions, indicating an improvement in water quality parameters.