Engineering industrial Saccharomyces cerevisiae strains for xylose fermentation and comparison for switchgrass conversion.
Saccharomyces' physiology and fermentation-related properties vary broadly among industrial strains used to ferment glucose. How genetic background affects xylose metabolism in recombinant Saccharomyces strains has not been adequately explored. In this study, six industrial strains of varied genetic background were engineered to ferment xylose by stable integration of the xylose reductase, xylitol dehydrogenase, and xylulokinase genes. Aerobic growth rates on xylose were 0.04-0.17 h(-1). Fermentation of xylose and glucose/xylose mixtures also showed a wide range of performance between strains. During xylose fermentation, xylose consumption rates were 0.17-0.31 g/l/h, with ethanol yields 0.18-0.27 g/g. Yields of ethanol and the metabolite xylitol were positively correlated, indicating that all of the strains had downstream limitations to xylose metabolism. The better-performing engineered and parental strains were compared for conversion of alkaline pretreated switchgrass to ethanol. The engineered strains produced 13-17% more ethanol than the parental control strains because of their ability to ferment xylose.
U.S. Department of Agriculture, Bioenergy Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA. ronald.hector@ars.usda.gov
Ronald E
RE
Hector
Bruce S
BS
Dien
Michael A
MA
Cotta
Nasib
N
Qureshi
D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism; D050542:D-Xylulose Reductase / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005818:Genetic Engineering; D005947:Glucose / Q000378:metabolism; D007218:Industrial Microbiology; D008897:Panicum / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D014993:Xylitol / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
D005656:Fungal Proteins; D000431:Ethanol; D014994:Xylose; D000449:Aldehyde Reductase; D050542:D-Xylulose Reductase; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D005947:Glucose; D014993:Xylitol