Simulation and optimization of fed-batch culture for ethanol production from molasses

Two simulation methods for ethanol production from molasses by a flocculating yeast, Saccharomyces cerevisiae AM12, were investigated and molasses feeding was optimized. The first method was based on a deterministic model with fixed kinetic parameters and the second was based on regression analysis. The amount of ethanol produced in a fed-batch culture with multiple additions of molasses was simulated by both of these two methods. Simulated results of a fed-batch culture were compared with those of a simple batch culture by a model of regression analysis. The intermittent addition of molasses gave better production than a single addition at the beginning; more frequent addition may further improve production. The experimental results suggested the same. The effect of the amount of the added molasses on ethanol production was investigated by simulation. Repeated batch culture with and without intermittent addition of molasses in each batch was also done.List of Symbols C_e deviation of calculated results from experimental results - F m³ volume of feed medium added to the fermentor - P kg/m³ concentration of ethanol - P_M kg total amount of ethanol - S kg/m³ concentration of sugar - S₀ kg/m³ concentration of sugar in the molasses feed medium - S_M kg total amount of sugar - V m³ culture volume - X kg/m³ concentration of cells - X_M kg total amount of cells - x_c calculated data - x_e experimental data - h^–1 specific rate of growth - kg-sugar/(kg-cell h) specific rate of sugar consumption - kg-ethanol/(kg-cell h) specific rate of ethanol production