The enzymatic decolorization and detoxification of synthetic dyes by the laccase from a soil-isolated ascomycete, Paraconiothyrium variabile

The enzymatic decolorization of 13 synthetic dyes with azo- and anthraquinone-based chemical structures using the purified laccase from Paraconiothyrium variabile was assessed in the presence and absence of 1-hydroxybenzotriazole (HBT) as a laccase mediator. The highest decolorization percentage was found for Acid Red 18 (97%) followed by Direct Red 81 (68.3%), Reactive Yellow 15 (60.2%), and Disperse Blue 56 (58%) after 15 min of incubation in the presence of 0.1 U mL(-1) of the enzyme. The use of the laccase-HBT system increased decolorization percentage of Reactive Orange 16, Reactive Black 5, Direct Blue 71, Disperse Red 177, and Acid Yellow 36, while other chemical dyes were not affected by an increase of the HBT concentration. The kinetic parameters of the purified laccase for each textile dye were also calculated. A microtoxicity study with respect to the inhibition of bacterial growth showed a decrease in toxicity of the laccase-treated dye solution. (C) 2013 Elsevier Ltd. All rights reserved.