Automatic bioprocess control. 4. A prototype batch of Saccharomyces cerevisiae.
The recent investigations in our high performance bioreactors have shown that living cells can be extremely sensitive to physical-chemical environmental conditions and their changes. Consequently, the relationship bioreactor-living cell must thoroughly be investigated in order to discuss both: whether bioreactor characteristics are limiting/dominating during cultivation and to what extent controlled changes of the cellular environment can lead the cells to a desired physiological state. For these investigations, a generally accepted biological test organism would be helpful, of which the requirements and reactions under certain conditions are well known. Saccharomyces cerevisiae is a well known, very robust but nevertheless sensitive organism, eligible for this purpose. In this article a typical batch cultivation on glucose is presented, collected from approx. 300 experiments. Regarding metabolite production and consumption, seven different phases are distinguished on the basis of approx. 20 sensor signals and their metabolic background is discussed. Prerequisite, however, was an exhaustive knowledge upon extracellular conditions, a task which could successfully be fulfilled with the highly automated equipment introduced in the preceding articles of this series.