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Poster Presentation 2-09
Characterization of a Novel Ethanologenic Yeast in the Fermentation of Softwood Lignocellulosic Sugars
J.D. Keating1, J. Robinson1, R.J. Bothast2, J.N. Saddler1, S.D. Mansfield1
1Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver, British Columbia V6T1Z4 Canada
2Fermentation Biochemistry, National Center for Agricultural Utilization Research, USDA ARS, 1815 N. University St., Peoria, IL 61604
Telephone: (604) 822-0196; Fax: (604) 822-9104; E-mail: shawnman@interchange.ubc.ca
A novel, genetically unmodified ethanologenic yeast integrated into the pre-hydrolysate fermentation stage of the softwood-to-ethanol bioconversion process was identified as being capable of rapid assimilation and catabolism of all wood-derived hexose sugars (galactose, glucose, and mannose). This yeast strain was shown not to be subject to glucose-mediated catabolite repression and to employ a unique enzymatic mechanism to immediately and concomitantly convert galactose, glucose, and mannose to ethanol within eight hours on synthetic sugar media, and eighteen hours on steam-exploded softwood pre-hydrolysate.
Regardless of substrate conditions, the selected yeast strain immediately initiated galactose metabolism at the onset of fermentation, demonstrating complete consumption of the sugar alongside that of glucose and mannose. The conventional sequential sugar utilization observed in most ethanologenic yeasts consistent with preferential cell membrane transport and catabolism was notably absent, as was the conventional slow rate of galactose consumption. Ethanol yields were comparable with those achieved by current industrially utilized yeast strains.
The unique enzyme found in this yeast strain aided hexose sugar catabolism through rapid activity and specific localization.
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