A GENERAL-MODEL OF YEAST ENERGY-METABOLISM IN AEROBIC CHEMOSTAT CULTURE

The pattern of energy metabolism of different types of yeasts (obligat e aerobes and facultative anaerobes) in aerobic chemostat cultures has been evaluated and interpreted on the basis of a coupling of metaboli c fluxes between glycolytic and oxidative components. A model has been formulated which defines glycolytic and oxidative subunits through wh ich the substrate C-flux (gram-atom g(-1) h(-1)) is calculated, statin g that a relative imbalance between glycolytic flux and subsequent oxi dative steps alone is sufficient to account for the onset of oxidoredu ctive metabolism in any type of yeast, irrespective of the maximum res piratory capacity. The model is able to reproduce the patterns of beha viour reported for the different types of yeasts, and the individual f eatures of each strain are explained on the basis of metabolic differe nces which are defined by a set of normalized parameters. The model ca n be applied to different substrates and conditions, providing a metho dological basis for more detailed studies of the steps controlling yea st energy metabolism.