Pure Pseudomonas putida (DSM 6978) culture was used for biodegradation of 2,4 dichlorophenol (DCP) in batch shake flasks. The rate and extent of biodegradation were quantified at different initial DCP concentrations between 30 and 300 mg l(-1). Increasing initial DCP concentrations resulted in increasing effluent concentrations and decreasing percent biodegradation at the end of the incubation period. The initial rate of biodegradation of DCP increased with the initial concentrations up to 160 mg l(-1). Further increases in DCP concentrations resulted in decreases in the rate of biodegradation because of DCP inhibition. A substrate-inhibited kinetic model was used to correlate the experimental data and to determine the kinetic and inhibition constants. Toxicity of DCP on pure P. putida culture was quantified by using the Resazurin method. The IC50 value for the organisms was found to be approximately 250 mg DCP l(-1). (C) 2004 Elsevier Inc. All rights reserved.