Closed carbon balance in calculation of metabolic fluxes – Application to the central metabolism of Saccharomyces cerevisiae in wine-making fermentation

This paper presents the metabolic-fluxes calculation of a metabolic network representing the central metabolism of the yeast Saccharomyces cerevisiae in the wine-making context. Two solution methods are compared: a metabolic flux analysis (MFA) using convex analysis and providing narrow intervals of variation for the fluxes, and a flux balance analysis (FBA) based on an objective function. The constraints allowing the solution of the underdetermined set of algebraic equations are typically originating from measurements of uptake and secretion rates of external metabolites, and/or the use of an objective function, and/or metabolic constraints. It is shown here that converting reactions schemes in Cmol unit combined with data reconciliation provides a convenient formulation of closed carbon balance. In this form, the constraint formulation is natural and facilitates the understanding of the carbon distribution within the yeast metabolism.