Decolorization of Reactive Black 5 and Reactive Red 152 Azo Dyes by New Haloalkaliphilic Bacteria Isolated from the Textile Wastewater

Textile wastewaters are usually alkali and saline, so using haloalkaliphilic bacteria can be the best option for the treatment of wastewater. This study aimed at the decolorization of textile Reactive Black 5 and Reactive Red 152 dyes using new haloalkaliphilic bacteria isolated from the textile wastewater. Among 50 strains of bacteria isolated from the effluent of Kashan textile industry, three bacterial strains, namely D1, D2 and E49, exhibited high decolorization abilities for Reactive Black 5 and Reactive Red 152 dyes. Decolorization was evaluated through spectrophotometry at maximum absorbance wavelengths of 607 and 554 nm for Reactive Black 5 and Reactive Red 152, respectively. The highest decolorization percentage was observed at a dye concentration of 50 mg L-1. Aerobic conditions, 5% of the yeast extract and salt, 10% of peptone and glucose as nitrogen and carbon sources, respectively, and a pH range of 9-12 were considered as the optimal conditions for decolorization. The consortium of three haloalkaliphilic isolates showed a remarkable ability for decolorization of the Reactive Black 5 (87%) and Reactive Red 152 (85%) dyes. The consortium exhibited higher decolorization ability for the textile effluent, compared to individual bacterial inoculations. According to phenotypic characterization experiments and phylogenetic analyses based on comparing 16S rDNA sequence, the mentioned strains belonged to the genusHalomonas.