For a successful application of any industrial Z. mobilis facility, it is necessary to have an efficient and simple control strategy. This paper analyzes the control and optimization problem of a continuous ZM bioreactor modeled by Jöbses et al. (1986). This system has steady state multiplicity in part of the operating range. The idea is to maintain the process close to the manifold border where is achievable the highest ethanol production. Based on a systematically analysis of the operational controllability using the nonlinear RPN indices it is identified that the process can be controlled using a linear controller. Finally the paper proposes a variable transformation that makes easy to maintain the bioreactor close to the optimum.