Decolourization and detoxification of Reactive Red-195 azo dye by Staphylococcus caprae isolated from textile effluent.

Abstract

Azo dyes are used as coloring agent in textile industries at larger scale. As a result, large quantity of dye-enriched waste water is generated which subsequently poses environmental problems. Biological tool involving bacteria having azoreductase enzyme has proved to be more effective and efficient in dye effluent treatment. Current work focuses on Staphylococcus caprae (S. caprae) for degradation and decolorization of Reactive Red-195 (RR-195) azo dye. For this purpose, factors such as pH, temperature, inoculums, carbon and nitrogen sources, and dye concentrations have been optimized for maximum decolorization and degradation. S. caprae (4 mg/mL) efficiently resulted into 90% decolorization of RR-195 dye under static condition at 100 µg/mL concentration, 30 °C and pH 7.0 at a 12-h contact period. FTIR analysis has revealed the formation of new functional groups in the treated dye such as O-H stretch at 3370 cm^-1, C-H band stretching at 2928 cm^-1, and new band at 1608 cm^-1 which specify the degradation of aromatic ring, 1382 and 1118 cm^-1 represents desulfonated peaks. Biodegraded metabolites of RR-195 dye such as phenol, 3, 5-di-tert-butylphenol, and phthalic acid have been identified respectively that find industrial applications. Phytotoxicity test has shown non-toxic effects of treated dye on germination of Vigna radiata and Triticum aestivum seeds. Further, antibiotic diffusion assay has confirmed the biosafety of S. caprae.