Enhanced biodecolourization of azo dyes by suspended and immobilized quinone-reducing community using kinds of anthraquinone dyes intermediators as redox mediators was investigated. The suspended bacterium community could enhance the biodecolourization of many kinds of azo dyes using bromoamine acid (BAA) as a redox mediator, the optimum conditions for Acid Red 3R were as follows: pH 6-9, glucose, BAA and initial dye concentrations 400-600 mg/L, 19-34.2 mg/L and < or = 900 mg/L, respectively. Under these conditions, the maximal decolourization rate was about 95%, which is reached within 7 h for suspended cells and 14 h for immobilized cells. However, the latter needed 38-57 mg/L BAA as a redox mediator. In addition, after 7 cycles without BAA addition, the decolourization rate of Acid Red 3R by immobilized cells retained over 85%.