Ethanol production using xylitol synthesis mutant of xylose-utilizing zymomonas

• US 7,741,084 B2
• Filed: 09/27/2007
• Issued: 06/22/2010
• Est. Priority Date: 09/28/2006
• Status: Expired due to Fees

• Current Assignee: Alliance For Sustainable Energy LLC, Sustainable Technology Corporation
• Original Assignee: Alliance For Sustainable Energy LLC, E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Emptage, Mark, Chou, Yat-Chen, Caimi, Perry G., Zhang, Min, Viitanen, Paul V., McCutchen, Carol M.
• Primary Examiner(s): VOGEL, NANCY TREPTOW
• Application Number:
  US11/862,736
• Publication Number:
  US 20080187973A1
• Time in Patent Office: 999 Days
• Field of Search: None
• US Class Current: 435/161
• CPC Class Codes: C12P 7/065 with microorganisms other than yeasts
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

Production of ethanol using a strain of xylose-utilizing Zymomonas with a genetic modification of the glucose-fructose oxidoreductase gene was found to be improved due to greatly reduced production of xylitol, a detrimental by-product of xylose metabolism synthesized during fermentation.

Claims

1. A process for producing ethanol comprising,

a) providing a recombinant Zymomonas strain which utilizes xylose to produce ethanol., said strain comprising at least one genetic modification which reduces glucose-fructose oxidoreductase activity, and

b) culturing the strain of (a) in a medium comprising xylose whereby xylose is converted to ethanol.

2. The process according to claim 1, wherein the strain of (a) improves conversion of xylose to ethanol relative to a recombinant Zymomonas strain without at least one genetic modification which reduces glucose-fructose oxidoreductase activity.

3. The process of claim 2, wherein the strain of (a) improves one or more of rate, titer or yield, of xylose conversion to ethanol relative to a recombinant Zymomonas strain without at least one genetic modification which reduces glucose-fructose oxidoreductase activity.

4. The process according to claim 1, wherein the strain of (a) produces a reduced amount of xylitol when metabolizing xylose to ethanol as compared to a Zymomonas strain without at least one genetic modification which reduces glucose-fructose oxidoreductase activity.

5. The process according to claim 4, wherein the strain of (a) produces substantially no xylitol when metabolizing xylose to ethanol.

6. The process according to claim 1, wherein the recombinant Zymomonas strain of (a) is selected from the group consisting of ZW800, ZW801-4 and ZW801-6.

7. The process of claim 1, wherein the medium comprises a mixture of sugars including xylose and a sugar alcohol selected from the group consisting of sorbitol, mannitol, galactitol, ribitol, and a mixture thereof, wherein the mixture of sugars is at a concentration of at least about 120 g/L and wherein the sugar alcohol is at a final concentration that is between about 2 mM and about 100 mM.

8. The process of claim 7, wherein the sugar alcohol is in a concentration that is between about 5 mM and about 20 mM.