Poster Presentation 2-28

Effect of Over-Expression of Phosphoglucose Isomerase in Zymomonas mobilis Fermenting Glucose and Xylose

Christina K. Eddy^1*, Mete Altintas², Mary Ann Franden¹, Jim McMillan¹, Dhinakar S. Kompala² and Min Zhang¹

¹National BioEnergy Center

National Renewable Energy Laboratory

1617 Cole Boulevard

Golden, Colorado 80401

Phone: 303-384-7768

Fax 303-384-7752

E-mail: christina_eddy@nrel.gov

²Department of Chemical Engineering

University of Colorado

Boulder CO 80309-0424

Recombinant Zymomonas mobilis expressing a functional pentose phosphate pathway efficiently ferment xylose to ethanol. Only two intermediates, fructose-6 phosphate (F6P) and glyceraldehyde-3-phosphate (Ga-3P) can flow from the pentose phosphate pathway into the glycolytic pathway. These intermediates are acted upon by phosphoglucose isomerase (PGI) and glyceraldehyde-3-phosphate dehydrogenase (Ga-3PDH). In this study, a shuttle vector was constructed for expressing individual genes from an Escherichia coli tac promoter in Z mobiils and E. coli. PGI activity was 6-fold higher in Z. mobilis expressing the pgi gene from the tac promoter on the plasmid than in Z. mobilis containing the plasmid without pgi. However, the over-expression of PGI had little effect on growth and fermentation performance in rich medium with 2% glucose or 2% xylose. This strain is being evaluated for performance on higher concentrations of glucose and xylose. The results will be discussed in context of a kinetic metabolic model which predicted that over-expression of PGI would have little effect on xylose and glucose metabolism.