In the present study, the effects of various quinone compounds on the decolorization rates of azo dyes by the E. coli strain CD-2 were investigated. The results showed that Lawsone was the most effective redox mediator. The optimum concentration for Lawsone is 0.1 mmol/L. The effects of physic-chemical parameters on the Methyl Orange degradation by the strain were determined. The results indicated that, in the quinone mediated decolorization system, strain CD-2 exhibited a good degradation ability in the range of pH from 4 to 9, temperature from 20°C to 50°C and salinity from 1% to 6%. With Lawsone as a redox mediator, a broad spectrum of azo dyes with different structures could be decolorized by the strain. All the results showed that the addition of a redox mediator can be valuable for treating dye-colored wastewaters.
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