Decolourization of recalcitrant dyes with a laccase from Streptomyces coelicolor under alkaline conditions.

Colored wastewater from textile industries is a consequence of dye manufacturing processes. Two percent of dyes that are produced are discharged directly in aqueous effluent and more than 10% are subsequently lost during the textile coloration process. It is not surprising that these compounds have become a major environmental concern. In that context, we have evaluated the potential use of Streptomyces coelicolor laccase for decolourization of various dyes with and without a mediator. Results showed that in all cases the combination of laccase and the mediator acetosyringone was able to rapidly decolourize, to various degrees, all the dyes tested. In 10 min, decolourization was achieved at 94% for acid blue 74, 91% for direct sky blue 6b and 65% for reactive black 5. Furthermore, decolourization was achieved at 21% for reactive blue 19 and at 39% for the direct dye Congo red in 60 min. These results demonstrate the potential use of this laccase in combination with acetosyringone, a natural mediator, for dye decolourization.