The objective of this study was to investigate the potential ability of decolorizing Reactive Dark Blue K-R by the synergism of fungal strain Penicillium sp. QQ and bacterial strain Exiguobacterium sp. TL The optimal conditions for decolorization determined by response surface methodology (RSM) were as follows: 12.5% (w/v) of both strains QQ and TL, 0.19% (w/v) of glucose, 0.09% (w/v) of yeast extract, pH 7.0, 37 degrees C and 200 mg/L of initial dye concentration. It was shown that about 97% of 200 mg/L K-R could be decolorized within 24 h under these conditions. Besides, strains QQ and TL co-cultures could decolorize 10 kinds of azo dyes effectively and be still 60% color removal when salinity increased to 15%. And most of the tested metal ions showed little influence on the decolorization except for Ni(2+). The results demonstrated that strains QQ and TL co-cultures could be useful for the practical bioremediation. (c) 2010 Elsevier Ltd. All rights reserved.