Degradation of the organophosphorus pesticide has been studied using the marine isolate, Streptomyces venezuelae ACT1. The organism exhibited a specific growth rate of 0.371 h(-1) and the organophosphorus hydrolase activity rate as 0.273 h(-1). Hence the organism was found to be very effective towards the pesticide degradation. Further the substrate assimilation and inhibition model of the organism were demonstrated using Monod and Haldane model equations which depicted that the inhibition model fits well for both the cell growth and enzyme activity. The maximum specific growth rate and the enzyme activity rate were found to be 0.571 h(-1) and 0.472 h(-1), respectively. Effect of P-0/X-0 ratio on degradation and COD reduction rate revealed that higher these ratios raise the degradation rate and the COD reduction rate. (C) 2012 Elsevier Ltd. All rights reserved.