COMPARATIVE CHARACTERIZATION OF THE FERMENTATION PATHWAY OF SACCHAROMYCES-CEREVISIAE USING BIOCHEMICAL SYSTEMS-THEORY AND METABOLIC CONTROLANALYSIS - MODEL VALIDATION AND DYNAMIC BEHAVIOR

In the first two papers of this series (immediately preceding, this is sue), we characterized the steady-state properties of a model of a fer mentation pathway in Saccharomyces cerevisiae in four experimental con ditions. In each of these conditions, the pictures obtained by metabol ic control analysis and biochemical systems theory were coincident, wh ich illustrates the relatedness of the two approaches, In this paper w e analyze the quality of this description by means of the tools availa ble within biochemical systems theory, and we show that in some of the experimental conditions studied the system is poorly characterized. T he most critical condition corresponds to the immobilization of the ce lls at pH 5.5, in which the kinetic characterization appears to be ina ccurate. Furthermore, sensitivity analysis and the study of the local steady-state stability identify the most critical parameters. The resu lts of these analyses are confirmed by the predictions of the dynamic response of the model using its S-system representation. This illustra tes the utility of these tools and warns against using the steady-stat e characterization without testing its validity.