Bacterial decolorization of azo dyes by Rhodopseudomonas palustris

The ability of Rhodopseudomonas palustris AS1.2352 possessing azoreductase activity to decolorize azo dyes was investigated. It was demonstrated that anaerobic conditions were necessary for bacterial decolorization, and the optimal pH and temperature were pH 8 and 30-35 degrees C, respectively. Decolorization of dyes with different molecular structures was performed to compare their degradability. The strain could decolorize azo dye up to 1250 mg 1(-1), and the correlation between the specific decolorization rate and dye concentration could be described by Michaelis-Menten kinetics. Long-term repeated operations showed that the strain was stable and efficient during five runs. Cell extracts from the strain demonstrated oxygen-insensitive azoreductase activity in vitro.