Decolorization of a tannery dye: From fungal screening to bioreactor application

In the present work, the potential of three white-rot fungi (WRF) (Trametes versicolor, Ganoderma lucidum and Irpex lacteus) to decolorize the commercial tannery dye - Black Dycem - was investigated. The decolorization ability of the three strains was studied in primary and secondary screenings. The results indicated that T. versicolor displayed the greatest decolorization ability, both in terms of extent and rapidity. To assess the potential of T. versicolor, decolorization tests were performed in single and repeated batches in an air-pulsed bioreactor with biomass reuse. Although low enzyme activity was detected during the repeated batches, the decolorization capability of the fungus did not decrease, and T. versicolor was able to remove 86-89% of the dye. Further experiments were conducted in order to elucidate the enzymatic activities involved in the dye biodegradation process. The results proved that the biodegradation mechanism plays a noticeable role in the decolorization process of the dye, in addition to adsorption phenomenon occurring on the fungal surface. Moreover, it was shown that laccase is involved in the decolorization process, although a mediator is required. Killed fungus presented an appreciable color removal even in repeated batches, suggesting that dead cells are an effective biosorbent. (C) 2011 Elsevier B.V. All rights reserved.