Decolorization of Reactive Black 5 by a newly isolated bacterium Bacillus sp. YZU1

A bacterial strain, YZU1, with remarkable ability to decolorize Reactive Black 5 (RB-5), was isolated from soil samples collected around a textile factory. Phenotypic and phylogenetic analyses of the 16S rDNA sequence indicated that YZU1 belonged to Bacillus sp. Bacillus sp. YZU1 showed great capability to decolorize various reactive textile dyes, including azo dye. Static conditions with pH 7.0 and 40 °C were considered to be optimum for decolorizing RB-5. Bacillus sp. YZU1 grew well in medium containing high concentration of dye (100. mg/l), resulting in approximately 95% decolorization in 120. h, and could tolerate up to 500. mg/1 of RB-5. Enzyme assays demonstrated that Bacillus sp. YZU1 possessed azoreductase and played the most important role in decolorization, while a small percentage of decolorization occurred via passive surface adsorption. High biodegradation extent under a mild condition suggested that Bacillus sp. YZU1 had great potential to be applied in dye effluent treatment.