Biodecolorization of azo dye acid red B under high salinity condition.

The study was conducted by a novel salt tolerant bacterium Gracilibacillus sp. GTY. The strain was identified on the basis of morphological and physio-biochemical characteristics, and 16S rDNA sequence analysis. Decolorization was performed by growing and resting cells, as well as by extracted azo reductase. Strain grown in the media containing 15% (w/v) of NaCl showed the best performance in decolorization. Decolorization was observed by the UV-visible absorbance spectra. The maximum absorption peak in the visible area decreased to a minimum level after 96 h of incubation. On the other hand, strain grown in very low, or high concentrations, of salt did not show good performance in decolorization; suggesting that salt concentrations in the surroundings control the production of azo reductase.