Optimal Control of Saccharomyces cerevisiae. Fermentation Process

This article demonstrates the existence of multiple optimal control profiles for the fermentation process involving Saccharomyces cerevisiae. The Jones-Kompala model is used to model the dynamics of the fermentation process. Both dilution rate and the oxygen mass transfer coefficient are used as the control variables individually and together. While it was demonstrated recently that the steady-state optimization for the Jones-Kompala model would reveal multiple optimum solutions, this work demonstrates the existence of multiple optimum control profiles when dynamic optimization is performed. To perform the dynamic optimization, the differential equations were converted to a nonlinear program (NLP) using Radau collocation with finite elements and the state-of-the-art optimization program CONOPT (constrained optimizer) was used to obtain the local optimum profiles. The global solution was confirmed using the deterministic global optimization program branch-and-reduce optimization navigator. Both the programs were accessed through the network enabled optimization system (NEOS) server.