Kinetic study of ethanol production by Zymomonas mobilis

Technical Report · Thu Dec 01 04:00:00 EST 1983

OSTI ID:5380194

Worden, R M; Donaldson, T L; Shumate, II, S E; Strandberg, G W

This study has investigated the effects of temperature, pH, glucose concentration, and ethanol concentration on the fermentation kinetics of the ethanol-producing bacterium Zymomonas mobilis (ATCC 10988). The effects of these parameters on the specific growth rate and the specific ethanol production rate of Z. mobilis were studied in batch and continuous culture. Initial-rate batch experiments were used to investigate the temperature, pH, and glucose concentration parameters. The growth medium was an aqueous solution of glucose (5 to 20%), yeast extract (Difco, 0.5%) and succinate (0.01 M). The effects of temperature on the specific growth and ethanol production rates were consistent with the Arrhenius Law in the range of 24 to 35/sup 0/C. The measured activation energy was 2.5 x 10/sup 4/ J/mol in both cases. The temperature corresponding to maximum specific growth rate was 35/sup 0/C, and the maximum specific ethanol production rate occurred at 37/sup 0/C. At higher temperatures, the rates declined rapidly. At 36/sup 0/C, maximum cell growth rates were found over the pH range 5.6 to 7.5, and maximum ethanol production rates were found over the pH range 5.2 to 7.5. Specific growth rates were more sensitive to acidic conditions than were ethanol production rates. At 36/sup 0/C, reaction rates were shown to increase with increasing glucose concentration up to approximately 10% and then to decline at higher concentrations. Classical kinetic models incorporating substrate inhibition could not be fit to the experimental data, suggesting that simple substrate inhibition may not be the primary mechanism responsible for the declining rates at high glucose concentrations. 53 references, 13 figures, 9 tables.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5380194
• Report Number(s): ORNL/TM-8722; ON: DE84005064
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ALCOHOLS
ALDEHYDES
BACTERIA
BIOCHEMICAL REACTION KINETICS
BIOCONVERSION
CARBOHYDRATES
CULTURE MEDIA
DATA
ETHANOL
EXPERIMENTAL DATA
FERMENTATION
GLUCOSE
GROWTH
HEXOSES
HYDROXY COMPOUNDS
INFORMATION
KINETICS
MICROORGANISMS
MONOSACCHARIDES
NUMERICAL DATA
ORGANIC COMPOUNDS
PH VALUE
PRODUCTION
REACTION KINETICS
SACCHARIDES
TEMPERATURE EFFECTS
ZYMOMONAS MOBILIS