Biological decolorization of textile dyestuff Reactive Orange 16 was investigated in a fed-batch reactor by using facultative anaerobic bacterial consortium called PDW. Effects of different operating parameters like flow rate (Q = 50-300 ml/h), dyestuff concentration (50-600 mg/l) and yeast extract concentration (1-5 g/l) on decolorization efficiency were studied. Reaction cycle was varied between 2 and 7 h depending on the feeding rate. System was operated at room temperature (T = 19 +/- 1 degreesC) and at pH = 7. The experimental results indicated that over 90% efficiency can be obtained up to 350 mg/l dyestuff concentration and 200ml/h feeding rate. Three grams per liter yeast extract concentration as sole carbon source was enough to obtain around 95% color removal. (C) 2003 Elsevier Inc. All rights reserved.