Influence of redox mediators and media on methyl red decolorization and its biodegradation by Providencia rettgeri

Abstract

Developing efficient, effective and low-cost procedure for color removal in wastewater is a serious environmental concern. In this study, we investigated the possibility of enhancing the activities of dyes decolorizing bacterium using selected redox mediators and media (nutrient broth, yeast, glucose, starch and peptone). The isolated organism identified using 16S rRNA gene as Providencia rettgeri showed the highest decolorization of a model dye, methyl red by 97% within 6 h using nutrient broth. Preferred redox mediator was found to be quinol (95% within 5 h) than other (nicotinamide adenine dinucleotide (NAD+), reduced NAD+, nicotinamide adenine dinucleotide phosphate (NADP+) and reduced NADP+). In addition, the biodegradation of methyl red was investigated by subjecting its metabolites to UV–visible, high-performance liquid chromatography and Fourier transform infrared analyses that suggested the biodegradation. This was confirmed by the removal of signature peaks of aromatic C–H bending (645, 759 and 831 cm−1) and the N=N peak at 1509 cm−1 of the FTIR spectrum of the metabolites. In conclusion, introduction of minute amount of hydroquinone (1 mM) into wastewaters could enhance their biotreatment by this strain of P. rettgeri.