A biochemically structured model for Saccharomyces cerevisiae

A biochemically structured model for the aerobic growth of Saccharomyces ce revisiae on glucose and ethanol is presented. The model focuses on the pyru vate and acetaldehyde branch points where overflow metabolism occurs when t he growth changes from oxidative to oxido-reductive. The model is designed to describe the onset of aerobic alcoholic fermentation during steady-state as well as under dynamical conditions, by triggering an increase in the gl ycolytic flux using a key signalling component which is assumed to be close ly related to acetaldehyde. An investigation of the modelled process dynami cs in a continuous cultivation revealed multiple steady states in a region of dilution rates around the transition between oxidative and oxido-reducti ve growth. A bifurcation analysis using the two external variables, the dil ution rate, D, and the inlet concentration of glucose, S-f as parameters, s howed that a fold bifurcation occurs close to the critical dilution rate re sulting in multiple steady-states. The region of dilution rates within whic h multiple steady states may occur depends strongly on the substrate feed c oncentration. Consequently a single steady state may prevail at low feed co ncentrations, whereas multiple steady states may occur over a relatively wi de range of dilution rates at higher feed concentrations. (C) 2001 Elsevier Science B.V. All rights reserved.