This study investigated the impact of 17 alpha-ethinylestradiol, a significant compound among endocrine disrupter on the biodegradation of a synthetic organic substrate-a peptone/meat extract mixture-under aerobic conditions. A laboratory scale sequencing batch reactor was sustained at steady state at a sludge age of ten days with substrate feeding. The reactors were started with the amendment of peptone mixture (600 mgCOD/L) and 17 alpha-ethinylestradiol (EE2) with a concentration of 1 mg/L. Experimental profiles of oxygen uptake rates and polyhydroxyalkanoates (PHAs) were evaluated by calibration of a selected model. 1 mg/L of 17 alpha-ethinylestradiol had no acute effect on process kinetics. However, at the fortieth day of acclimation period to EE2, model simulation results showed that the maximum heterotrophic growth rate and the maximum hydrolysis rate for slowly hydrolysable products increased due to the stimulated enzyme activity.