Direct fermentation of D-xylose to ethanol by a xylose-fermenting yeast mutant

• US 4,511,656 A
• Filed: 05/11/1982
• Issued: 04/16/1985
• Est. Priority Date: 05/15/1981
• Status: Expired due to Fees

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Gong, Cheng-Shung
• Primary Examiner(s): Yoncoskie, Robert
• Application Number:
  US06/376,731
• Time in Patent Office: 1,071 Days
• Field of Search: 435/161, 435/163-165, 435/921, 435/924, 435/930, 435/940, 435/944
• US Class Current: 435/161
• CPC Class Codes: C12N 1/165 Yeast isolates
• CPC Class Codes: C12N 1/185 Saccharomyces isolates
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: C12R 2001/72 Candida
• CPC Class Codes: C12R 2001/865 Saccharomyces cerevisiae
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y10S 435/921 Candida
• CPC Class Codes: Y10S 435/942 Saccharomyces cerevisiae

Abstract

A process for obtaining ethanol directly from D-xylose through fermentation of D-xylose by xylose-fermenting yeast mutants. The process provides for obtaining ethanol from hemicellulose hydrolyzates through yeast fermentation of D-xylose to ethanol. In addition, a process for producing yeast mutants capable of utilizing D-xylose to ethanol in high yields is described. Furthermore, the process also provides for obtaining ethanol from a mixture of cellulose and hemicellulose hydrolyzates through yeast fermentation of D-glucose and D-xylose directly and simultaneously to ethanol.

Claims

1. A process for the direct fermentation of D-xylose to ethanol which comprises inoculating a medium comprising growth nurients and D-xylose with a yeast mutant having an ability to ferment D-xylose to ethanol with a bioconversion yield of at least 50%, permitting the inoculated medium to ferment for a period of time sufficient to achieve a conversion of D-xylose to ethanol of at least 50% and recovering the ethanol so produced as product, said mutant being obtained from a parent yeast strain selected from the group consisting of Candida sp. and Saccharomyces cerevisiae.

2. The process of claim 1 wherein the conversion of D-xylose to ethanol is at least 80%.

3. A process according to claim 1 wherein the parent yeast strain is Candida sp.

4. A process according to claim 1 wherein the yeast mutant is Candida sp. XF 217.

5. A process according to claim 1 wherein the parent strain is Saccharomyces cerevisiae.

6. A process according to claim 1 wherein the yeast mutant is Saccharomyces cerevisiae SCXF 138.

7. A process according to claim 1 wherein the initial concentration of D-xylose in said medium ranges from 1 to about 40 percent on a weight/volume basis.

8. A process according to claim 7 wherein said initial concentration ranges from about 5 to 30 percent.

9. A process according to claim 1 wherein fermentation is carried out at a temperature ranging from about 22°

to about 40°

C.

10. A process according to claim 9 wherein said temperature is about 30°

C.

11. A process according to claim 1 wherein fermentation is carried out at a pH ranging from about 4 to about 8.

12. A process according to claim 11 wherein said pH is about 6.

13. A process according to claim 1 wherein fermentation is carried out under aerobic conditions.

14. A process according to claim 1 wherein fermentation is carried out under anaerobic conditions.

15. A process according to claim 1 wherein the D-xylose is contained in hemicellulose hydrolyzate.

16. A process according to claim 1 wherein said medium also contains cellulose hydrolyzate material.

17. A process for the direct fermentation of D-xylose to ethanol which comprises inoculating a medium comprising growth nutrients and D-xylose in an amount of from 1 to about 40% by weight/volume of said medium with a yeast mutant having an ability to ferment D-xylose to ethanol with a bioconversion yield of at least 50%, fermenting the inoculated medium at a temperature ranging from about 22°

to about 40°

C. and a pH ranging from about 4 to about 8 for a period of time sufficient to achieve at least a 50% conversion of the D-xylose to ethanol, and recovering the ethanol so produced as product, said mutant being obtained from a parent yeast strain selected from the group consisting of Candida sp. and Saccharomyces cerevisiae.

18. A process according to claim 17 wherein the temperature is about 30°

C. and pH about 6.

21. A process according to claim 17 or 19 wherein said yeast mutant is Candida sp. XF217.

19. A process for the production of ethanol directly and simultaneously from D-glucose and D-xylose which comprises inoculating a medium comprising growth nutrients, D-glucose and D-xylose with a yeast mutant having an ability to ferment D-glucose and D-xylose to ethanol with a bioconversion yield of at least 50%, fermenting the inoculated medium for a period of time sufficient to achieve a conversion of D-xylose to ethanol of at least 50% and recovering the ethanol so produced as product, said mutant being obtained from a parent yeast strain selected from the group consisting of Candida sp. and Saccharomyces cerevisiae.

20. A process according to claim 19 wherein the D-glucose and D-xylose are obtained from cellulose and hemicellulose hydrolyzate.

22. A culture consisting essentially of a mutant strain Candida sp. XF 217.

23. A culture consisting essentially of a mutant strain Saccharomyces cerevisiae SCXF 138.