Decolorization of azo dye Congo Red by Trametes pubescens pellets without addition of nutrition

Abstract:

[Objective] White-rot fungus Trametes pubescens pellets without addition of nutrition treatment, a novel design, was used to lower the running cost as well as to enhance convenient availability for dye decolorization. [Methods] Liquid cultured pellets of T. pubescens were used to decolorize various dyes without addition of nutrition and then the removal process of the azo dye Congo Red with higher decolorization rate was analyzed. During the decolorization process, the extracellular and intracellular enzyme activities were monitored and the impact factors such as initial pH value, temperature, dye concentration and salinity were optimized. Moreover, metabolites of the dye Congo Red degraded by T. pubescens pellets without addition of nutrition were analyzed by gas chromatography-mass spectroscopy (GC-MS). Phytotoxicity experiment was carried out before and after dye decolorization to assess the toxic nature of the metabolites. [Results] The pellets could decolorize azo dye Congo Red. After a 7-day incubation period, the highest dye removal of 80.52% was observed under 150 r/min shaking speed at initial pH 2.0, temperature at 30 °C, dye concentration 80 mg/L and salinity 2.5% (W/V). The pellets performed good persistence in repetitive decolorization operations, as well as high potentials toward the degradation of dye Congo Red which could be attributed to the presence of biotransformation enzymes. Additionally, degraded metabolites were identified as naphthalene amine, biphenyl amine and naphthalene diazonium, as evidenced by GC-MS. Phytotoxicity experiment confirmed that the azo dye Congo Red degraded by T. pubescens pellets without addition of nutrition resulted in its detoxification. [Conclusion] These findings demonstrate that the T. pubescens pellets have potentials for the azo dye effluents treatment applications without addition of nutrition.