Decolorization of Cibacron Black w-55 under Alkaline Conditions by New Strain of Halomonas sp. Isolated from Textile Effluent

Among the 30 strains of moderately halophilic bacteria isolated from the salty effluents of textile industries around Qom city in central Iran, a Gram-negative rod shape bacterium designated as strain IP8 showed a remarkable ability in decolorizing of azo dyes over wide ranges of pH (7-11) and temperature (25-45 ºC), in presence of NaCl and Na2SO4 (0.5-1.5 M) under anaerobic and aerobic conditions. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparisons indicated that this strain was a member of the genus Halomonas with the greatest similarity to Halomonas axialensis. UV-Vis analysis before and after decolorization and the colorless bacterial biomass after treatment suggested that decolorization was due to biodegradation. HPLC analysis of dye treatment confirmed that the principal biodegradation was occurred after 48h of incubation in aeration culture. The effect of metal salts on decolorization showed that AgNO3 and NaAsO4 were of higher and lower effect on decolorization, respectively.