Process for producing sugars and ethanol using corn stillage

• US 20090093027A1
• Filed: 10/03/2008
• Published: 04/09/2009
• Est. Priority Date: 10/03/2007
• Status: Active Grant

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Dale, Bruce, Sousa, Leonardo, Chundawat, Shishir, Balan, Venkatesh
• Granted Patent: US 8,367,378 B2
• Time in Patent Office: Days
• US Class Current: 435/99
• CPC Class Codes: C12P 19/14 produced by the action of a carbohydrase (EC 3.2.x), e.g. by alpha-amylase , e.g. by cellulase, hemicellulase
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

A process for producing sugars from lignocellulosic materials such as corn stover by the addition of corn stillage as a carbon source is disclosed. The sugars are formed by treating the combination of the corn stillage and the lignocellulosic materials with hydrolytic enzymes. The sugars can be fermented to ethanol, and the process improves ethanol production economies with an increased sugar yield from the lignocellulosic materials.

Claims

1. A process for producing sugars from a lignocellulosic material, the process comprising:

(a) adding corn grain stillage to the lignocellulosic material; and

then

(b) treating the lignocellulosic material with one or more hydrolyzing enzymes, thereby hydrolyzing complex carbohydrates in the lignocellulosic material and forming the sugars.

2. The process of claim 1, wherein the corn grain stillage comprises whole grain stillage with solids.

3. The process of claim 1, wherein the corn grain stillage comprises thin stillage.

4. The process of claim 1, wherein the corn grain stillage comprises about 0.05 wt. % to about 50 wt. % crude corn protein.

5. The process of claim 1, wherein the lignocellulosic material comprises corn stover.

6. The process of claim 1, wherein the lignocellulosic material comprises one or more of miscanthus, rice straw, poplar, and bagasse.

7. The process of claim 1, wherein:

treating the lignocellulosic material is performed in an aqueous medium comprising the lignocellulosic material, the corn grain stillage, and the hydrolyzing enzymes;

the lignocellulosic material comprises glucan; and

the aqueous medium has a glucan loading of the lignocellulosic material ranging from about 0.1 wt. % to about 20 wt. %.

8. The process of claim 1, wherein:

treating the lignocellulosic material is performed in an aqueous medium comprising the lignocellulosic material, the corn grain stillage, and the hydrolyzing enzymes; and

the aqueous medium comprises about 0.5 wt. % to about 99 wt. % corn grain stillage relative to the aqueous medium.

9. The process of claim 1, wherein:

treating the lignocellulosic material is performed in an aqueous medium comprising the lignocellulosic material, the corn grain stillage, and the hydrolyzing enzymes;

the corn grain stillage comprises crude corn protein; and

the aqueous medium comprises about 0.02 wt. % to about 5 wt. % crude corn protein relative to the aqueous medium.

10. The process of claim 1, wherein the hydrolyzing enzymes comprise one or more cellulases and, optionally, one or more hemicellulases.

11. The process of claim 1, further comprising pretreating the lignocellulosic material prior to treating the lignocellulosic material, thereby disrupting the lignocellulosic material.

12. The process of claim 11, wherein pretreating the lignocellulosic material comprises performing an ammonia fiber explosion (AFEX) process.

13. The process of claim 11, wherein pretreating the lignocellulosic material comprises performing one or more of a dilute-acid treatment process, a dilute-base treatment process, an ammonia recycle percolation process, a steam explosion process, a high-temperature exposure process, an irradiation process, a lime pretreatment process, an alkaline wet oxidation process, and an ionic liquid pretreatment process.

14. The process of claim 1, wherein step (a) further comprises:

(a-1) separating the corn grain stillage into a thin stillage component and a wet grain component;

(a-2) drying the wet grain, thereby forming distillers dried grains with solubles (DDGS); and

(a-3) adding the thin stillage and the DDGS to the lignocellulosic material.

15. The process of claim 1, further comprising:

(c) fermenting the sugars.

16. The process of claim 15, wherein treating the lignocellulosic material and fermenting the sugars are performed in a single vessel.

17. A process for producing sugars from corn stover, the process comprising:

(a) pretreating the corn stover with an ammonia fiber explosion (AFEX) process, thereby disrupting the corn stover;

(b) adding thin corn grain stillage to an aqueous medium comprising the pretreated corn stover; and

then

(c) treating the corn stover in the aqueous medium with one or more cellulase enzymes, thereby hydrolyzing cellulose in the corn stover and forming the sugars.

18. The process of claim 17, wherein:

the corn stover comprises glucan, and

the aqueous medium has a glucan loading of corn stover ranging from about 1 wt. % to about 4 wt. %.

19. The process of claim 17, wherein:

the corn stover comprises glucan, and the aqueous medium has a glucan loading of corn stover ranging from about 4 wt. % to about 15 wt. %.

20. The process of claim 17, further comprising:

(d) fermenting the sugars.

21. In a process for producing ethanol from corn grain in which dry-ground corn grain is (1) enzymatically treated to convert corn grain starches to sugars, (2) fermented with yeast to convert the sugars to ethanol, and (3) distilled to recover the ethanol, thereby producing solid and liquid bottoms fractions as a corn stillage by-product, the improvement which comprises:

(a) adding the corn stillage from the corn grain processing to a lignocellulosic material.

22. The process of claim 21, wherein the lignocellulosic material comprises AFEX-pretreated corn stover, and the process further comprises:

(b) treating the combination of the corn stillage and the corn stover from step (a) with one or more cellulase enzymes, thereby hydrolyzing cellulose in the corn stover and forming sugars.

23. The process of claim 22, further comprising:

(c) fermenting the sugars, thereby forming ethanol; and

(d) recycling the fermented ethanol for distillation and recovery of the ethanol.