Xylitol synthesis mutant of xylose-utilizing zymomonas for ethanol production
View Patent ↗A strain of xylose-utilizing Zymomonas was engineered with a genetic modification to the glucose-fructose oxidoreductase gene resulting in reduced expression of GFOR enzyme activity. The engineered strain exhibits reduced production of xylitol, a detrimental by-product of xylose metabolism. It also consumes more xylose and produces more ethanol during mixed sugar fermentation under process-relevant conditions.
1. A recombinant Zymomonas strain which utilizes xylose to produce ethanol, comprising at least one genetic modification which reduces glucose-fructose oxidoreductase activity.
2. The recombinant Zymomonas strain of claim 1 , wherein the genetic modification which reduces glucose-fructose oxidoreductase activity is selected from the group consisting of insertion, deletion, mutation, cosuppression, and antisense RNA expression.
3. The recombinant Zymomonas strain of claim 1 , wherein the genetic modification which reduces glucose-fructose oxidoreductase activity is an insertion introduced into the glucose-fructose oxidoreductase gene of said strain, by homologous recombination.
4. The Zymomonas strain according to claim 1 , identified as a strain selected from the group consisting of ZW800, ZW801-4 and ZW801-6.
5. The Zymomonas strain of claim 1 , wherein said strain produces a reduced amount of xylitol as compared to a strain with no genetic modification reducing glucose-fructose oxidoreductase activity.
6. The Zymomonas strain of claim 5 , wherein the strain produces substantially no xylitol.
7. A process for generating a Zymomonas strain which utilizes xylose to produce ethanol that has reduced GFOR activity, comprising:
a) providing a recombinant Zymomonas strain which utilizes xylose to produce ethanol under suitable conditions; and
b) introducing at least one genetic modification to the recombinant Zymomonas strain which utilizes xylose to produce ethanol of (a), wherein said modification reduces glucose-fructose oxidoreductase activity.
8. The process according to claim 7 , wherein the recombinant Zymomonas strain which utilizes xylose to produce ethanol of (a) is selected from the group consisting of ATCC31821/pZB5, Z. mobilis 8b, ZW658, ZM4(pZB5) and Z. mobilis CP4:pZB5.
9. The process according to claim 7 , wherein the genetic modification is selected from the group consisting of insertion, deletion, mutation, co-suppression, and antisense RNA expression.