Co-fermentation of glucose, xylose and/or cellobiose by yeast
Provided herein are methods of using yeast cells to produce ethanol by contacting a mixture comprising xylose with a Spathaspora yeast cell under conditions suitable to allow the yeast to ferment at least a portion of the xylose to ethanol. The methods allow for efficient ethanol production from hydrolysates derived from lignocellulosic material and sugar mixtures including at least xylose and glucose or xylose, glucose and cellobiose.
1. A method of producing ethanol comprising contacting a mixture comprising xylose and glucose with a Spathaspora passalidarum yeast under conditions suitable to allow the yeast to ferment at least a portion of the xylose to ethanol either before or during the same time the yeast is fermenting the glucose; wherein the yeast is Spathaspora passalidarum NN245, deposited with the Agricultural Research Service as Deposit Number NRRL Y-50740.
2. The method of claim 1 , wherein the yeast is Spathaspora passalidarum adapted for growth in a hydrolysate.
3. The method of claim 1 , wherein the glucose is less than or equal to about 30 g/l of the mixture.
4. The method of claim 1 , wherein the conditions are suitable for fermentation of at least a portion of the glucose to ethanol.
5. The method of claim 1 , wherein the mixture further comprises cellobiose.
6. The method of claim 5 , wherein the conditions are suitable for fermentation of at least a portion of the cellobiose to ethanol.
7. The method of claim 6 , wherein the conditions include oxygen limitation.
8. The method of claim 7 , wherein the oxygen is less than or equal to about 2.1% in the mixture.
9. The method of claim 1 , wherein the mixture further comprises cellobiose.
10. The method of claim 9 , wherein the conditions are suitable for fermentation of at least a portion of the glucose and a portion of the cellobiose to ethanol.
11. The method of claim 10 , wherein the conditions include oxygen limitation.
12. The method of claim 10 , wherein the oxygen is less than or equal to about 2.1% in the mixture.
13. The method of claim 1 , wherein the mixture is a hydrolysate.
14. The method of claim 13 , wherein the hydrolysate is from corn stover, grain hulls, corn cobs, sugarcane bagasse, wood chips, wood pulp, softwood, hardwood, pine, loblolly pine, maple, switchgrass ( Pancium virgatum ), Miscanthus , date palm ( Phoenix dectylifera ), oil palm, Sorghum , or Arundo donax.
15. The method of claim 13 , wherein the hydrolysate is an enzymatic or acid hydrolysate.
16. The method of claim 13 , wherein the hydrolysate is an acid hydrolysate, and wherein the yeast is adapted to growth in acidic conditions prior to contact with the mixture.
17. The method of claim 16 , wherein the yeast is adapted to growth in at least 3.0 acetic acid.
18. The method of claim 13 , wherein the hydrolysate is subjected to saccharification either before or simultaneous with the method.
19. The method of claim 1 , wherein the rate of ethanol production is greater than or equal to about 0.5 g/lh.
20. The method of claim 1 , wherein the amount of ethanol produced per gram of sugar in the mixture is greater than or equal to about 0.3 grams per gram sugar.