Decolorization and degradation of azo dye Methyl Red by an isolated Sphingomonas paucimobilis: Biotoxicity and metabolites characterization

Azo dyes are recalcitrant and refractory pollutants that constitute a significant burden on the environment. The report here is focused on the decolorization treatment of water soluble azo dye Methyl Red (MR). Sphingomonas paucimobilis, was isolated from the effluent treatment plant of a textile and dyeing industry (SITEX) located in KsarHellal, Tunisia. At shaking condition this strain showed 99.63% decolorization of a toxic azo dye MR (750 ppm) within 10 h in a Mineral Salt Medium (MSM) at 30 °C and pH 9. The degradation of MR was possible through a broad pH (3–11) and temperature (5–40 °C) range. Untreated dye at 750 mg/1 concentration showed 30% germination inhibition in Sorghum bicolor, whereas it was 55% in Triticum aestivum. There was no germination inhibition for both the plants by MR metabolites at 750 ppm concentration. The degradation products were characterized by UV–visible and Fourier Transform Infrared Spectroscopy (FTIR), their toxicity with respect to Artemia salina was evaluated. The scientific relevance of the paper: the azo dye MR (750 ppm) was decolorized by S. paucimobilis within 10 h at shaking condition in MSM. This organism could decolorize MR at wide pH and temperature ranges.

Research highlights
► In the present investigation, the MR was degraded by the Sphingomonas paucimobilis.
► S. paucimobilis, was isolated from the effluent treatment plant of a textile.
► The degradation products were characterized by UV–visible and FTIR Spectroscopy.