Declining rate of ethanol production during batch fermentation by Saccharomyces cerevisiae

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6018081

Dombek, K M

As Saccharomyces cerevisiae ferments 20% glucose to ethanol in batch culture the rate of this conversion declines. Previous studies assumed that ethanol caused this inhibition because added ethanol repressed both yeast growth and alcohol production. A nutrient limitation for magnesium in complex fermentation medium was identified as being partially responsible for declining rates of alcohol production. As yeast cells produced ethanol, they did change physiologically, however, becoming more resistant to inhibition of fermentation by added ethanol and to ethanol-induced decreases in ..delta.. pH. Initially, the intracellular levels of phosphorylated glycolytic intermediates decreased as fermentation rate was declining. These results suggested that the rates of glucose uptake and/or phosphorylation were slowing relative to carbon flux through the rest of the pathway. Declining glycolytic intermediate levels probably were not due to inhibition of glycolytic enzymes by declining levels of nicotinamide nucleotides. Initially during fermentation, ATP levels decreased by 60%, while AMP increased by 900%. One possible explanation for the decline in glycolytic intermediates and the corresponding decrease in fermentation rate is that the increased level of AMP inhibits glucose phosphorylation which may slow the rate of glucose uptake. In this study, the roles of inhibition by ethanol, nutrient limitation, and physiological changes in decreasing the rate of fermentation have been defined and characterized. Each of these factors appears to be partially responsible for the decline in ethanol production by S. cerevisiae during batch fermentation.

• Research Organization: Florida Univ., Gainesville (USA)
• OSTI ID: 6018081
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
090222* -- Alcohol Fuels-- Preparation from Wastes or Biomass-- (1976-1989)
550700 -- Microbiology
59 BASIC BIOLOGICAL SCIENCES
ALCOHOLS
ALDEHYDES
ALKALINE EARTH METALS
AMP
BATCH CULTURE
BIOCHEMICAL REACTION KINETICS
BIOCONVERSION
CARBOHYDRATES
CHEMICAL REACTIONS
ELEMENTS
ENZYMES
ETHANOL
EUMYCOTA
FERMENTATION
FUNGI
GLUCOSE
HEXOSES
HYDROXY COMPOUNDS
INHIBITION
KINETICS
MAGNESIUM
METALS
MICROORGANISMS
MONOSACCHARIDES
NUCLEOTIDES
NUTRIENTS
ORGANIC COMPOUNDS
PHOSPHORYLATION
PHYSIOLOGY
PLANTS
PRODUCTION
REACTION INTERMEDIATES
REACTION KINETICS
REMOVAL
SACCHARIDES
SACCHAROMYCES
SACCHAROMYCES CEREVISIAE
VARIATIONS
YEASTS