Isolation, identification and decoloring capability of an Acid Red 3R decoloring bacterial strain

A bacterial strain M3 with remarkable ability to decolorize the Acid Red 3R was isolated from anaerobic sludge by the method of the concentration gradient domestication. The strain was identified as Enterobacter cloacae according to its morphological characters and 16S rRNA gene sequences analysis. Experiments on the effect of decolorization conditions were carried out under anaerobic condition. The results showed that the best nutrient source was yeast powder and the optimum conditions were 1% yeast powder, pH=6.5, 35°C, and less than 4% salinity. Under this condition, the decolorization rate of Acid Red 3R (100 mg·L^-1 initial concentration) was over 98% when the strain M3 was cultivated for 72 h. This strain also showed good salt tolerance property in 6%~8% NaCl concentration range. Spectrophotometric analysis demonstrated that the decolorization mechanism of Acid Red 3R was mainly biological degradation. Toxicity tests indicated that the toxicity of Acid Red 3R after decolorization had reduced obviously.