Biochemical and mathematical modeling of microaerobic continuous ethanol production by Saccharomyces cerevisiae
The effect of the aeration intensity in the vicinity of 10ppb of dissolved oxygen upon the steady state, continuous ethanol production by Saccharomyces cerevisiae is explored. Ethanol productivity increased by 30 to 50% as the aeration rate was reduced, but decreased to the original level as the aeration was further reducted. These metabolic changes occurred when the respiration rate contributed negligibly to ATP energy production, excluding the Pasteur mechanism, and when the residual glucose level saturated the glucose transporter, excluding glucose kinetics as the cause. To expose the mechanism of the metabolic changes, the intracellular concentrations of ethanol, glycerol, ATP, glucose 6-phosphate, pyruvate, and NADH, the activities of the hexokinase, alcohol dehydrogenae, fumarase, and isocitrate dehydrogenase, and the cell viability were assayed. The metabolic acceleration with decreasing aeration was the result of an increasing glucose transporter activity, and ATP was the most likely activator. The reversal as yet lower aerations resulted from the continued accumulation of ATP until the downstream glycolytic kinases were inhibited. High concentrations of silicone polymer antifoam decreased the resistance to glycerol transport across the cell membrane, enhancing glycerol production at the expense of ethanol production. The biomass concentration in the fermentor was occasionally found to undergo hysteresis. This and associated phenomena were prevented by the addition of yeast extract and the removal of the antifoam from the medium. Mathematical models account for all observed phenomena.
- Research Organization:
- California Inst. of Tech., Pasadena, CA (USA)
- OSTI ID:
- 5492625
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BIOREACTORS
MATHEMATICAL MODELS
ETHANOL
BIOSYNTHESIS
SACCHAROMYCES CEREVISIAE
BIOCHEMICAL REACTION KINETICS
AERATION
ATP
ENZYMES
GLUCOSE
GLYCEROL
HYSTERESIS
METABOLISM
PRODUCTIVITY
ALCOHOLS
ALDEHYDES
CARBOHYDRATES
EUMYCOTA
FUNGI
HEXOSES
HYDROXY COMPOUNDS
KINETICS
MICROORGANISMS
MONOSACCHARIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
PLANTS
REACTION KINETICS
SACCHARIDES
SACCHAROMYCES
SYNTHESIS
YEASTS
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