Genetically modified yeast species and fermentation processes using genetically modified yeast
View Patent ↗Yeast cells are transformed with an exogenous xylose isomerase gene. Additional genetic modifications enhance the ability of the transformed cells to ferment xylose to ethanol or other desired fermentation products. Those modifications', include deletion of non-specific or specific aldose reductase gene(s), deletion of xylitol dehydrogenase gene(s) and/or overexpression of xylulokinase.
1. A genetically modified K. marxianus cell having a genome and a functional, exogenous xylose isomerase gene, wherein the exogenous xylose isomerase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell, and the modified yeast cell further has a deletion or disruption of a native gene that produces an enzyme that is specific to the conversion of xylose to xylitol.
2. A fermentation process in which a K. marxianus cell of claim 1 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
3. A genetically modified C. sonorensis cell having a genome and a functional, exogenous xylose isomerase gene, wherein the exogenous xylose isomerase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell, and the modified yeast cell further has a deletion or disruption of a native gene that produces an enzyme that is specific to the conversion of xylose to xylitol.
4. A fermentation process in which a C. sonorensis cell of claim 3 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
5. A genetically modified yeast cell of the genera Kluyveromyces , having integrated into its genome a functional, exogenous xylose isomerase gene, wherein the exogenous xylose isomerase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell.
6. The genetically modified Kluyveromyces yeast cell of claim 5 , further having a deletion or disruption of a native pyruvate decarboxylase gene.
7. The genetically modified Kluyveromyces yeast cell of claim 5 , further having integrated into its genome a functional, exogenous lactate dehydrogenase gene, wherein the exogenous lactate dehydrogenase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell.
8. A fermentation process in which a Kluyveromyces cell of claim 5 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
9. A fermentation process in which a Kluyveromyces cell of claim 6 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
10. A fermentation process in which a Kluyveromyces cell of claim 7 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
11. A genetically modified yeast cell of the genera Kluyveromyces, Candida, Pichia, Brettanomyces or Pachysolen having a genome and a functional, exogenous xylose isomerase gene, wherein the exogenous xylose isomerase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell, and which further contains a functional, exogenous xylulokinase gene operatively linked to promoter and terminator sequences that are functional in the yeast cell.
12. The genetically modified C. sonorensis yeast cell of claim 11 , further having a deletion or disruption of a native pyruvate decarboxylase gene.
13. The genetically modified yeast cell of claim 11 , further having integrated into its genome a functional, exogenous lactate dehydrogenase gene, wherein the exogenous lactate dehydrogenase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell.
14. A fermentation process in which a yeast cell of claim 11 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
15. A fermentation process in which a yeast cell of claim 12 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
16. A fermentation process in which a yeast cell of claim 13 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
17. A genetically modified K. marxianus cell having a deletion or disruption of a native gene that produces an enzyme that catalyzes the conversion of xylose to xylitol.
18. A fermentation process in which a K. marxianus cell of claim 17 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.
19. A genetically modified C. sonorensis cell having a deletion or disruption of a native gene that produces an enzyme that catalyzes the conversion of xylose to xylitol.
20. A fermentation process in which a C. sonorensis cell of claim 19 is cultured under fermentation conditions in a fermentation broth that includes a pentose sugar.