This work proposes a robust control strategy for the optimizing control of fed-batch cultures of S. cerevisae. The process dynamics is characterized by a nonlinear kinetic model based on the bottleneck assumption and ethanol inhibition for a possible excess of substrate feeding. The control strategy is based on the feedback linearization technique, where the resulting free linear dynamics is designed so as to ensure a certain robustness to plant parameter variations. A feedforward loop achieves the correct critical substrate value, which is a function of the ethanol and oxygen in the culture medium. In addition, a robust Luenberger-like observer is designed taking plant parameter variations into account. Numerical experiments demonstrate the potential of the proposed approach as a tool for control design of fed-batch cultures.