Metabolic regulation and maximal reaction optimization in the central metabolism of a yeast cell

Regulation of ???uxes in a metabolic system aims to enhance the production rates of biotechnologically important compounds. Regulation is held via modi???cation the cellular activities of a metabolic system. In this study, we present a metabolic analysis of ethanol fermentation process of a yeast cell in terms of continuous culture scheme. The metabolic \nregulation is based on the kinetic formulation in combination with metabolic control analysis to indicate the key enzymes which can be modi???ed to enhance ethanol production. The model is used to calculate the intracellular ???uxes in the central \nmetabolism of the yeast cell. Optimal control is then applied to the kinetic model to ???nd the optimal regulation for the fermentation system. The sensitivity results show that there are external and internal control parameters which are adjusted in enhancing ethanol production. As an external control parameter, glucose supply should be chosen in appropriate way such that the optimal ethanol production can be achieved. For the internal control parameter, we ???nd three enzymes as regulation targets \nnamely acetaldehyde dehydrogenase, pyruvate decarboxylase, and alcohol dehydrogenase which reside in the acetaldehyde branch. Among the three enzymes, however, only acetaldehyde dehydrogenase has a signi???cant effect to obtain optimal \nethanol production ef???ciently.