Dynamic effects related to steady-state multiplicity in continuous Saccharomyces cerevisiae cultivations.
The behavioral differences between chemostat and productostat cultivation of aerobic glucose-limited Saccharomyces cerevisiae were investigated. Three types of experiments were conducted: a chemostat, where the dilution rate was shifted up or down in stepwise manner; and a productostat, with either stepwise changed or a rampwise increased ethanol setpoint, i.e., an accelero-productostat. The transient responses from chemostat and productostat experiments were interpreted using a simple metabolic flux model. In a productostat it was possible to obtain oxido-reductive steady states at dilution rates far below Dcrit due to a strong repression of the respiratory system. However, these steady states could not be obtained in a chemostat, since a dilution rate shift-down from an oxido-reductive steady state led to a derepression of the respiratory system. It can therefore be concluded that the range of dilution rates where steady-state multiplicity can be obtained differs depending on the operation mode and that this dilution rate multiplicity range may appear larger in a productostat than in a chemostat. A more narrow multiplicity range, however, was obtained when the productostat was operated as an accelero-productostat.
Lei
Frede
F
CAPEC, Department of Chemical Engineering, Building 227, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Olsson
Lisbeth
L
Jørgensen
Sten Bay
SB
D019149:Bioreactors / Q000382:microbiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D018929:Cell Culture Techniques / Q000379:methods*; D049109:Cell Proliferation; D003198:Computer Simulation; D000431:Ethanol / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism*
D002245:Carbon Dioxide; D000431:Ethanol; D010100:Oxygen