Degradation of Tectilon Yellow 2G (TY2G), an azo dye has been studied by hybrid technique involving pretreatment by sonochemical method and further biological treatment by Pseudomonas putida mutant. Pretreatment experiments were carried out by sonolysis of the dye solution at different concentrations (100-1000 mg/L). Wild type Gram-negative P. putida species isolated from the textile effluent contaminated soil, which was found to be effective towards dye degradation, has been acclimatized so as to consume TY2G as the sole source of nutrition. Mutant strain was obtained from the acclimatized species by random mutagenesis using the chemical mutagen ethidium bromide for various time intervals (6-30 min). The optimum mutagenesis exposure time for obtaining the most efficient species for dye degradation was found to be 18 min. An efficient mutant strain P. putida ACT 1 has been isolated and was used for growth experiments. The mutant strain showed a better growth compared to the wild strain. The substrate utilization kinetics has been modeled using Monod and Haldane model equations of which the Haldane model provided a better fit. The enzyme kinetics of the mutant and wild species was obtained using Michaelis-Menten equation. The mutated species showed better enzyme kinetics towards the degradation of TY2G. (C) 2010 Elsevier Ltd. All rights reserved.