Decolorization of synthetic dyes by laccase immobilized on epoxy-activated carriers

The laccase from the ascomycete Myceliophthora thermophila was covalently immobilized on polymethacrylate-based polymers (Sepabeads EC-EP3 and Dilbeads NK) activated with epoxy groups. The enzyme immobilized on Sepabeads EC-EP3 exhibited notable activity (203 U/g) along with remarkably improved stability towards pH, temperature and storage time, but no increased resistance to organic solvents. In addition, the biocatalyst also showed good operational stability, maintaining 84% of its initial activity after 17 cycles of oxidation of ABTS. The immobilized laccase was applied to the decolorization of six synthetic dyes (Reactive Black 5, Acid Blue 25, Methyl Orange, Remazol Brilliant Blue B, Methyl Green and Acid Green 27) with or without the redox mediator 1-hydroxybenzotriazole. The laccase immobilized in Sepabeads EC-EP3 retained 41% activity in the decolorization of Methyl Green in a fixed-bed reactor after five cycles. The features of these biocatalysts are very attractive for their application on the decolorization of dyes in the textile industry in batch and continuous fixed-bed bioreactors.