Kinetics and mechanism of reactive red 141 degradation by a bacterial isolate Rhizobium radiobacter MTCC 8161

A bacterium identified as Rhizobium radiobacter MTCC 8161 was isolated from effluent treatment plant of textile and dying industry of Ichalkaranji, India. The bacterial isolate Rhizobium radiobacter MTCC 8161 was capable of decolorizing various azo, triphenylmethane (TPM), disperse and reactive textile dyes with decolorizing efficiency varying from 80-95%. This strain decolorized (90%) a deep red sulfonated diazo dye Reactive Red 141 (50 mg/L) with 0.807 mg of dye reduced/g of dry cells/h of specific decolorization rate in static anoxic condition at optimum pH 7.0 and temperature 30 degrees C with 83.33% reduction in COD. The degradation efficiency of this strain using urea and yeast extract showed fast decolorization among different carbon, nitrogen source. The induction of various oxidative and reductive enzymes indicates involvement of these enzymes in color removal. Phytotoxicity studies revealed less toxic nature of decolorized products (1000 mg/L) as compared to original dye. FTIR spectroscopy and GC-MS analysis indicated naphthalene diazonium, p-dinitrobenzene and 2-nitroso naphthol as the final products of Reactive Red 141.