Uniform mixing is one of the expected operational conditions in a fermentation process because it provides essential conditions for the microorganisms in the bioreactor in producing desired products. Different stirring speeds and aeration rates will be the critical factors for a different mixing mechanism. Thus in this work, comparisons were made between different stirring speeds as well as aeration rates to study the impact of both parameters with respect to ethanol production in bioreactor. Experiments were conducted in a laboratory scale bioreactor, where the produced ethanol was analyzed using UV spectrometer. Our experiment results reveal that the ethanol production in a bioreactor is dependent on both stirring speed and aeration rate. Saccharomyces cerevisiae was able to produce approximately 13% of ethanol in 64 hours in a fully aerated fed-batch process in laboratory scale with a 150rpm stirring speed. On the other hand, under the same experimental setup, Saccharomyces cerevisiae was able to produce around 20% of ethanol with the implementation of 250rpm stirring speed. In general, the level of production was found to be increasing with time for both stirring speeds and aeration rates. CFD modeling and simulation approach will be employed to gain better understanding of the impacts of aeration rates and stirring speeds on mixing, and hence bioreactor productivity.