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.
Govindaswamy
Shekar
S
National Risk Management Research Laboratory, US Environmental Protection Agency (MS 443), 26 W. Martin Luther King Dr., Cincinnati, OH 45268, USA.
Vane
Leland M
LM
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