Discontinuities in continuous cultures studied with a recombinant Saccharomyces cerevisiae and two computer models

Chemostat cultures and other continuous cultures, where the feed to the bioreactor was divided in pulses while maintaining the overall dilutions rate by the increased flow in the pulses, were studied by cultivations with Saccharomyces cerevisiae JG176 and by simulations with two computer models, Yeast model SG176 and Yeast model MC176. All three systems gave interesting response surfaces. Deviations from an ideal chemostat may have significant effects on volumetric productivity, which for production of the recombinant protein, proteinase A by Saccharomyces cerevisiae JG176 was positive, while the productivity of biomass and ethanol decreased. In simulations with both models pulsing caused lower production of biomass and ethanol. In simulations with one of the models the effects of pulsing on productivity of a protein were also negative, whereas simulations with the other model suggested clear positive effects of pulsing on a production of a protein though with a somewhat different response surface than with the experiments with Saccharomyces cerevisiae JG176.