Sunday, May 3, 2009 - 2:00 PM
2-03
Production of a xylose utilizing Zymomonas mobilis strain for ethanol production from high concentrations of mixed sugars
Paul Viitanen1, Carol Mc Cutchen1, Mark Emptage1, Perry Caimi1, Min Zhang2, Yat-Chen Chou2, and Mary Ann Franden2. (1) DuPont/Danisco Cellulosic Ethanol, DuPont Co., Experimental Station, PO Box 80402, Wilmington, DE 19880, (2) National Bioenergy Center, NREL, 1617 Cole Blvd, MS3323, Golden, CO 80401
Maximizing yield of ethanol from C5 utilizing micro organisms requires both high rates of sugar utilization and minimizing the production of by products that detract from carbon yield to ethanol. Zymomonas mobilis that has been engineered to utilize xylose by way of the pathway through xylose isomerase and xylulose kinase to the endogenous sugar phosphate pathway produces xylitol and xylitol phosphate as byproducts. Xylitol production results in loss of ethanol yield and xylitol phosphate is a general metabolic inhibitor as a dead end phosphate sink. In order to correct these deficiencies in xylose utilizing Z. mobilis, the pathway to xylitol and xylitol phosphate was determined and the gene for the enzyme at the head of the pathway was inactivated to produce a strain that has better fermentation properties and a higher ethanol yield. Effective means for achieving osmotic balance in high initial sugar fermentations was also established for the mutant and parent strain.