Method for Regulating Oscillatory Dynamic Behavior in a Zymomonas mobiliz Continuous Fermentation Process

Abstract

Periodically oscillating concentrations of product, biomass, and substrate have been observed in a continuous fermentations process with Zymomonas mobiliz both in experiments and simulations. This paper describes the characteristics of oscillatory phenomena based on Hopf bifurcation analysis and proposes a method to regulate the oscillatory dynamic behavior. In this method, these dynamic behaviors of oscillations in concentrations of product, biomass, and substrate were simulated, the relationship between amplitude/period and operational condition was modeled. This model could be used as a guide to adjust the operating conditions to attenuate unfavorable oscillations and mitigate corresponding operability problems when the oscillation itself is unavoidable.

A New Biochemical Fermentation Process Design Method Considering Bifurcations and Oscillations

“…Figure 6.6 summarizes the basic procedures of regulating the oscillatory phenomena in a dynamic system (Wang et al, 2014a). As each of these Hopf points may generate an oscillatory phenomenon, the characteristics of the oscillatory phenomenon must be properly related to the operating conditions.…”

Strategies for the Analysis of Continuous Bioethanol Fermentation under Periodical Forcing

“…The yeast Saccharomyces cerevisiae or bacterium Zymomonas mobiliz are microorganisms that are particularly important in the production of ethanol from continuous fermentation processes . The growth kinetics of these microorganisms, however, is known to be highly nonlinear, and continuous ethanol fermentation tends to generate steady-state multiplicity or self-sustained oscillations. − Because the richness in dynamic behavior is often considered undesirable from the perspectives of process design and operation, a complete knowledge of the static and dynamic behaviors for such processes is necessary …”

Two‐Parameter Continuation and Bifurcation Strategies for Oscillatory Behavior Elimination from a Zymomonas mobilis Fermentation System

“…The fluctuations in the fermentation process can reduce the ethanol productivity by inhibiting useful metabolic pathways 12. The fluctuation behavior in an ethanol fermentation system leads to an increase in the concentration of the remaining substrate and low rates of ethanol production, yield, substrate conversion, and product quality, in addition to system instability 17, 18. The oscillatory behavior may harm the fermentation systems by inhibiting cell growth and preventing the production of new metabolites.…”

“…Ethanol can affect the kinetics and the steady‐state and dynamic behavior of cells. The latter behavior is negatively affected due to the delayed response of the cells to ethanol inhibition and finally due to the onset of the oscillatory behavior 17.…”