Studies were carried out on the decolorization of textile azo dyes by newly isolated halophilic and halotolerant bacteria. Among the 27
strains of halophilic and halotolerant bacteria isolated from effluents of textile industries, three showed remarkable ability in decolorizing
the widely utilized azo dyes. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparisons indicate
that these strains belonged to the genus Halomonas. The three strains were able to decolorize azo dyes in a wide range of NaCl concentration
(up to 20% w/v), temperature (25–40 C), and pH (5–11) after 4 days of incubation in static culture. They could decolorize the
mixture of dyes as well as pure dyes. These strains also readily grew in and decolorized the high concentrations of dye (5000 ppm) and
could tolerate up to 10,000 ppm of the dye. UV–Vis analyses before and after decolorization and the colorless bacterial biomass after
decolorization suggested that decolorization was due to biodegradation, rather than inactive surface adsorption. Analytical studies based
on HPLC showed that the principal decolorization was reduction of the azo bond, followed by cleavage of the reduced bond.
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