A Combined Cell-Cycle and Metabolic Model of Baker's Yeast and its Application in Process Optimization

A cell cycling model for unequal budding yeast Saccharomyces cerevisiae is proposed and verified in the sense of steady state with experimental data available in the literature. As the quality of yeast is strongly influenced by the cycling process, the model can be used to optimize and control the quality of the harvested yeast cells. The input variable of the cell cycling model is the specific growth rate μ, which is obtained from a metabolic model for S. cerevisiae proposed earlier. With this extended model system, simulations were done to optimize the profit of a commercial scale fed-batch baker's yeast production process by dynamically manipulating the substrate feeding rate. Also substrate concentration in the feed, aeration rate, fermentation interval and other operating conditions are subject to optimization. The result of the optimization deviates significantly from usual feeding policies.