Culture fluorescence studies on aerobic continuous cultures ofSaccharomyces cerevisiae

Summary Fluorometric measurements were performed in continuous aerobic cultures ofSaccharomyces cerevisiae in order to study the effect of substrate concentration and residence time on the intracellular NADH-level. A modified Beyelermicrofluorometer probe (Beyeler et al. 1981) was used for the experiments. It was possible to use this sensor continuously up to five weeks without problems. The relative NADH-values obtained by the on-line monitoring of the NADH-dependent culture fluorescence were compared to the enzymatically determined NADH-content. Biomass estimation from fluorescence data was performed. During oxidative-reductive catabolism the deviation between calculated and measured data were below 5%. The differences between oxidative and oxidative-reductive catabolism were studied regarding glucose addition, dilution rate increase and aerobic-anaerobic transition. For synchronized continuous cultures, changes in dilution rate resulted in changes of the oscillating behaviour. Flow cytometric studies in comparison with fluorometric studies showed changes in budding behaviour during the oscillations.