Degradation of Orange G by laccase: fungal versus enzymatic process.

Biodegradation of the Orange G azo dye by pellets of Trametes versicolor in a fluidized bioreactor operating under conditions of laccase production was studied. The percentage of decolorization obtained was 97% in batch mode and both the biomass and the broth, were colorless. In vitro degradations carried out with purified commercial laccase from Trametes versicolor demonstrated that laccase is able to degrade the dye. In spite of the high level of decolorization reached in both processes, an important difference between the fungal and enzymatic treatments was detected. At the end of the experiments carried out in vitro, a final residual color appears (different to the initial one). Consequently, measuring the yield of decolorization as a percentage of absorbance lambdamax variation is not the best indicator of the treated wastewater quality, but the analysis of the visible color spectrum makes it possible to detect changes in color. The results demonstrate that better results are obtained with fungal Orange G biodegradation because a further breakdown of the enzymatic products is achieved with the fungus.