A mathematical Model for Bioreactor was developed and the simulated experimental data was used in Identification tool of MATLAB. The transfer function was identified using identification tool. The first order plus time delay (FOPTD) transfer function was obtained for bioreactor. The FOPTD model was used in SIMULINK and a relay feedback test was conducted to obtain a symmetric relay response. Then the Ziegler et al. optimum controller parameter method and Padmasree et al. method were used for estimation of optimum control parameters for the bioreactor system.