Decolorization and detoxification of sulfonated azo dye methyl orange by Kocuria rosea MTCC 1532

Kocuria rosea (MTCC 1532) showed 100% decolorization of methyl orange (50 mg l(-1)) under static condition. The optimum pH and temperature for dye decolorization was 6.8 and 30 degrees C, respectively. The K. rosea (MTCC 1532) showed maximum decolorization of methyl orange when growth medium containing yeast extract as compared to other substrates.

The culture exhibited significant ability to decolorize repeated additions of dye, with reduction in time up to 12 h at eighth dye aliquot addition. Significant induction of reductases (NADH-DCIP reductase and azoreductase) suggests its involvement in decolorization of methyl orange. The metabolites formed after decolorization of methyl orange, such as 4-amino sulfonic acid and N,N'-dimethyl p-phenyldiamine were characterized using FTIR and MS.

Phytotoxicity and microbial toxicity study showed the methyl orange was toxic and metabolites obtained after its decolorization was nontoxic for experimental plants (Triticum aestivum and Phaseolus mungo) and bacteria (K. rosea, Pseudomonas aurugenosa and Azatobacter vinelandii).