Sterile air was used to adjust the fermentation redox potential as a planned level. In the chemostat fermenter, both intracellular and extracellular factors should reach their respective states as a steady state is attained. Thus a constant growth rate and yeast viability are sustained under the pre-determined redox potential levels, which is helpful to prolong the redox potentialcontrolled duration and to maximize the benefits from redox potential control. The CCACS achieved the
longest controlled period and the highest ethanol yield among all three schemes.