Biodegradation of bis-azo dye Reactive Black 5 by white-rot fungus Trametes gibbosa sp WRF 3 and its metabolite characterization

Abstract

The culture of Trametes gibbosa sp. white-rot fungi (WRF) 3 under mesophilic conditions can lead to the degradation of azo dye compounds. This ability of T. gibbosa sp. WRF 3 is attributed to the released enzymes that are able to catalyze the structural degradation of the azo dye compound. The effect of environmental factors such as carbon sources, nitrogen sources, and pH of growth medium were investigated in this research. The addition of 20 g/L glucose (carbon source) and yeast extract (nitrogen source) at pH 5 of growth medium enhanced the decolorization of Reactive Black 5 (RB5) dye up to 87.07% within 30 days of incubation. The decolorization of RB5 can be analyzed using UV-vis spectroscopy and differential pulse cathodic stripping voltammetry (DPCSV). The maximum absorbance of RB5 was at 597 nm and decreased after the dye was treated with T. gibbosa sp. WRF 3. In the voltammetric analysis, we examined the effect of pH of Britton-Robinson buffer (BRB) medium on the detection of bis-azo compound of RB5. A stock solution of RB5 was used in the study, and it showed two reduction peak potentials at -0.5 and -0.7 V which attributed to the bis-azo bond, whereas the metabolic product showed one reduction peak at -0.6 V. The GC-MS mass spectrum confirmed the formation of metabolites at tR 4.63 min and m/z of 73 after 30 days of incubation which was sec-butylamine.