In glucose-limited continuous cultures, a Crabtree positive yeast such as Saccharomyces cerevisiae displays respiratory metabolism at low dilution rates (D) and respirofermentative metabolism at high D. We hypothesized that the onset of fermentative metabolism is related with the catabolite repression or glucose repression effect. To test this hypothesis, we have investigated the physiological behaviour in glucose-limited continuous cultures of S.cerevisiae strain CEN.PK122 and isogenic mutants, snf1 (cat1) and snf4 (cat3), defective in proteins involved in the release from glucose repression and the mutant in glucose repression mig1. We analyzed the behaviour of the wild type and mutant strains at steady state in chemostat cultures as a function of D. Wild-type cells displayed respiratory metabolism up to a D of 0.2 h-1. snf1 and snf4 mutants started fermenting after a D of 0.1 and 0.15 h-1, respectively. The latter behavior was not due to an impairment of respiration since their specific rate of oxygen consumption was similar or even higher than that shown by the wild type and the other mutants in the whole range of D studied. We conclude that the onset of fermentative metabolism in yeast growing in chemostat cultures is related with glucose repression.
- Catabolite repression mutants
- Chemostat cultures
- Saccharomyces cerevisiae
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology