Continuous Ethanol Fermentation at High Gravity in the Presence of Saccharomyces Cerevisiae: A Bifurcation Analysis
In this paper, a study of the bifurcation analysis of fermentation of sugar to ethanol in presence of Saccharomyces cerivisiae at very high gravity is described. The bifurcation analysis was done for concentration, 200 gl-1. Three Hopf bifurcations at 200 gl-1. The system exhibits sustained oscillations between two Hopf bifurcations, which are the consequence of synchrony between the daughter and the mother yeast. The first Hopf bifurcation is located at 0.04226 h-1 and the second at 0.1105 h-1 for concentration of sugar 200 gl-1. Indeed, it is better to take a dilution rate between the two Hopf bifurcations (self sustained oscillations), and the concentration at high gravity, in order to increase the ethanol productivity. At low dilution rate, the system exhibits a third Hopf bifurcation at 0.01849 h-1and a pseudo bistability is observed in this resgion. This can be explained as switching between fermentation and respiration of the yeast, caused by the limitation of sugar, and utilization of the ethanol as a poorly substrate.
Keywords - Bifurcation; Ethanol; Fermentation; Saccharomyces Cerevisiae; High Gravity