Various optimization techniques have been proposed to optimize the feed rate profile to maximize ethanol production. Among them are the differential algebraic system (DAS) approach, Kelly transformation approach, singular control approach, and on-off control approach. These methods are compared and it is shown that the DAS approach and Kelly transformation method are equivalent. A nonsingular transformation approach is presented. The performance obtained with the nonsingular approach is the same as that obtained with the singular approach and better than those obtained with the DAS and on-off control approaches.