In biochemical industry process variables such as pH, temperature, dissolved oxygen and speed are the main parameters that need to be controlled for optimal cellular activity. These control implementations are achieved via regulation of flow rate of acid/base, flow rate of fluid through the cooling coil, and agitation respectively. This paper presents a fuzzy logic controller to optimize the speed of an agitator in a bioreactor system. An open loop test was conducted and model parameters were determined. The identified process was represented by first order plus dead time model (FOPDT). From the model parameters, PI and fuzzy tuned PI controllers were Designed using MATLAB. The closed loop performance was studied for both servo and regulator problems. Based on overshoot, rise time, settling time, and ISE, it was found that the fuzzy tuned PI controller is best suited for this process. © 2014 M. Sridevi, P. Prakasam and P. MadhavaSarma.