Kinetics of growth and ethanol production on different carbon substrates using genetically engineered xylose-fermenting yeast.
Saccharomyces cerevisiae 424A (LNH-ST) strain was used for fermentation of glucose and xylose. Growth kinetics and ethanol productivity were calculated for batch fermentation on media containing different combinations of glucose and xylose to give a final sugar concentration of 20+/-0.8 g/L. Growth rates obtained in pure xylose-based medium were less than those for media containing pure glucose and glucose-xylose mixtures. A maximum specific growth rate micro(max) of 0.291 h(-1) was obtained in YPD medium containing 20 g/L glucose as compared to 0.206 h(-1) in YPX medium containing 20 g/L xylose. In media containing combinations of glucose and xylose, glucose was exhausted first followed by xylose. Ethanol production on pure xylose entered log phase during the 12-24h period as compared to the 4-10h for pure glucose based medium using 2% inoculum. When glucose was added to fermentation flasks which had been initiated on a pure xylose-based medium, the rate of xylose usage was reduced indicating cosubstrate inhibition of xylose consumption by glucose.
National Risk Management Research Laboratory, US Environmental Protection Agency (MS 443), 26 W. Martin Luther King Dr., Cincinnati, OH 45268, USA.
Shekar
S
Govindaswamy
Leland M
LM
Vane
D002244:Carbon / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005818:Genetic Engineering; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D013379:Substrate Specificity; D014994:Xylose / Q000378:metabolism*
D000431:Ethanol; D002244:Carbon; D014994:Xylose; D005947:Glucose