Effect of copper and different carbon and nitrogen sources on the decolorization of an industrial dye mixture under solid-state fermentation

Abstract

Abstract The treatment of colored effluents has been addressed using different methodologies, such as the coupling of adsorption to solid-state fermentation (SSF). This work shows for the first time the use of an agricultural by-product (corncob) as the adsorbent for the removal of the binary mixture of dyes, brilliant blue and allura red, and their subsequent decolorization by white-rot fungi. Pleurotus ostreatus, Trametes versicolor and their consortium were the selected fungal species for carrying out the second step of this bioprocess. A 23 full factorial design was adopted, obtaining a maximum decolorization of 90.8 ± 4.1% with T. versicolor at a 20:1 carbon:nitrogen ratio, 80% moisture and the absence of inducer. Moreover, the effect of different carbon and nitrogen sources was evaluated; yeast extract was discovered to be the most efficient nitrogen source, while the supplement of a carbon source was unnecessary to reach high levels of decolorization. Regarding the influence of the inducer, it was found that although copper addition favored enzyme levels of laccase (Lac), no positive effect was observed in either the decolorization rate of the dye mixture or the manganese peroxidase (MnP) activity, and a maximum of 19.8 ± 2.1 U Lac gds−1 and 5.4 ± 1.3 U MnP gds−1 was obtained. These results suggest that the coupled adsorption-SSF methodology using corncob and white-rot fungi represents a promising strategy for the treatment of effluents polluted with dye mixtures.