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US 8,911,983 B2Granted
Pnp gene modification for improved xylose utilization in Zymomonas
AssigneeE. I. Du Pont de Nemours and Company
InventorsPerry G G Caimi, Min Qi, Luan Tao, Paul V Viitanen, Jianjun Yang
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Abstract
The endogenous pnp gene encoding polynucleotide phosphorylase in the Zymomonas genome was identified as a target for modification to provide improved xylose utilizing cells for ethanol production. The cells are in addition genetically modified to have increased expression of ribose-5-phosphate isomerase (RPI) activity, as compared to cells without this genetic modification, and are not limited in xylose isomerase activity in the absence of the pnp modification.
Claims16
A recombinant bacterial host cell comprising:
- a) a xylose metabolic pathway comprising at least one polypeptide having xylose isomerase activity;
- b) at least one genetic modification which increases ribose-5-phosphate isomerase activity in the host cell as compared with ribose-5-phosphate isomerase activity in the host cell lacking said genetic modification;
- and
- c) at least one genetic modification in the sequence of an endogenous gene encoding polynucleotide phosphorylase that shortens the coding region resulting in expression of a C-terminal truncated protein;
- wherein the bacterial host cell utilizes xylose to produce ethanol, and the xylose isomerase activity is not rate limiting in the bacterial host cell.
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Dependencies are inferred from the claim text.