Glucose repression in yeast represents a major problem for both the cultivation on industrial substrates and for the breadmaking (leavening) because glucose has to be depleted before the remaining sugars can be utilized. In glucose-derepressed Saccharomyces cerevisiae strains, simultanous, and concomitantly more time-efficient, utilisation of the sugars would be possible resulting in an improved process economy and a lower environmental burden beside better leavening characteristics. Several genes playing key roles in catabolite repression have been deleted in an industrial strain. The physiology of the recombinants will be compared with the wild type in well controlled high performance bioreactors in order to elucidate the respective gene functions in the regulatory cascade of catabolite repression. Measurements of extracellular sugars and metabolites, assays for sugar-cleavaging enzymes and uptake systems, Northern blotting and radioactive techniques will be the analytical tools providing the basis for a metabolic flux analysis.