Biodegradation of textile dyes by immobilized laccase from Coriolopsis gallica into Ca-alginate beads

Synthetic dyes are extensively used in a number of industries, such as textile dyeing. Due to their low biodegradability, they cause serious environmental pollution. Thus, in the present paper a partiallypurified acid fungal laccase from the white-rot basidiomycete Coriolopsis gallica was entrapped into calcium alginate beads and applied to the decolorization of different synthetic dyes. Effects of immobilization conditions such as alginate concentration, CaCl2 concentration and the ratio enzyme/alginate (E/A) on the loading efficiency and immobilization yield were investigated. The optimal conditions for C gallica laccase immobilization into Ca-alginate beads were 2% (w/v) sodium alginate, 2% (w/v) CaCl2, and 1:4 E/A (v/v). It was also found that laccase stability to pH and temperature increased after immobilization. Both the free and immobilized laccase alone showed a high efficiency to decolorize the anthraquinone dye Remazol Brilliant Blue R (RBBR) while a low decolorization yield was observed for the diazo dyes Reactive Black 5 (RB5) and Bismark Brown R (BBR) and the metal textile dye Lanaset Grey G (LG). The addition of the redox mediator 1-hydroxybenzotriazole (HBT) to the decolorization reaction increased significantly dye removal. The immobilized laccase retained 70% of its activity after four successive decolorization cycles except for BBR (51.2%). The results obtained showed that the immobilized laccase from C. gallica has potential for its application in dyestuff treatment. (C) 2014 Elsevier Ltd. All rights reserved.