METHOD FOR THE PRODUCTION OF ALCOHOL FROM A PRETREATED LIGNOCELLULOSIC FEEDSTOCK

• US 20090035826A1
• Filed: 07/29/2008
• Published: 02/05/2009
• Est. Priority Date: 08/02/2007
• Status: Active Grant

• Current Assignee: Iogen Energy Corporation (Iogen Corporation)
• Original Assignee: Iogen Energy Corporation (Iogen Corporation)
• Inventors: Rowland, Stephen, Tolan, Jeffrey S., Foody, Brian
• Granted Patent: US 8,980,599 B2
• Time in Patent Office: Days
• US Class Current: 435/99
• CPC Class Codes: B01D 3/001 Processes specially adapted for distillation or rectification of fermented solutions
• CPC Class Codes: C07H 3/02 Monosaccharides
• CPC Class Codes: C07K 14/195 from bacteria
• CPC Class Codes: C08H 8/00 Macromolecular compounds derived from lignocellulosic materials pretreatment thereof B27N
• CPC Class Codes: C12P 19/02 Monosaccharides 2-ketogulonic acid C12P7/60
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02P 20/582 Recycling of unreacted starting or intermediate materials

Abstract

A process for the production of glucose from a pretreated lignocellulosic feedstock is provided. The method comprises enzymatically hydrolyzing the pretreated lignocellulosic feedstock with cellulase enzymes to produce a hydrolyzate slurry comprising glucose and unhydrolyzed cellulose and fermenting the hydrolyzate slurry in a fermentation reaction to produce a fermentation broth comprising alcohol. A process stream is obtained comprising unhydrolyzed cellulose, which is then subjected to a denaturing step, preferably comprising exposing the unhydrolyzed cellulose to elevated temperatures, thereby producing a heat-treated stream comprising the unhydrolyzed cellulose. The heat-treated stream comprising unhydrolyzed cellulose is then further hydrolyzed with cellulase enzymes to hydrolyze the cellulose to glucose.

Claims

1. A process for the production of alcohol from a lignocellulosic feedstock which comprises the steps of:

(i) pretreating a lignocellulosic feedstock under conditions to disrupt fiber structure and increase accessibility of the feedstock to being hydrolyzed in order to produce a composition comprising a pretreated lignocellulosic feedstock;

(ii) enzymatically hydrolyzing the pretreated lignocellulosic feedstock with cellulase enzymes to produce a hydrolyzate slurry comprising glucose and unhydrolyzed cellulose;

(iii) fermenting said hydrolyzate slurry to produce a fermentation broth comprising alcohol and unhydrolyzed cellulose;

(iv) separating the alcohol from the fermentation broth by distillation to obtain a stream comprising concentrated alcohol and a still bottoms stream comprising the unhydrolyzed cellulose, said distillation resulting in heat treatment of the unhydrolyzed cellulose; and

(v) further hydrolyzing at least a portion of the still bottoms stream with cellulase enzymes to convert at least a portion of the unhydrolyzed cellulose present in said still bottoms stream to glucose.

2. The process according to claim 1, wherein the step of further hydrolyzing comprises recycling at least a portion of the still bottoms stream back to step (ii).

3. The process according to claim 1, wherein the step of further hydrolyzing comprises introducing at least a portion of the still bottoms stream to a downstream hydrolysis reactor.

4. The process according to claim 1, wherein the step of enzymatically hydrolyzing the pretreated lignocellulosic feedstock and the step of fermenting said hydrolyzate slurry are carried out in separate reactors.

5. The process according to claim 1, wherein the pretreatment is carried out with a pH adjustant.

6. The process according to claim 5, wherein the pH adjustant is acid or alkali.

7. The process according to claim 1, wherein the enzymatic hydrolysis of the pretreated lignocellulosic feedstock is carried out in a hydrolysis system comprising a hydrolysis reactor selected from the group consisting of one or more agitated tanks, unmixed tanks, agitated towers and unmixed towers.

8. The process according to claim 1, wherein the step of enzymatically hydrolyzing is a batch process.

9. The process according to claim 1, wherein the step of enzymatically hydrolyzing is a continuous process.

10. The process according to claim 1, wherein the alcohol produced in the step of fermenting is ethanol or butanol.

11. The process according to claim 10, wherein the distillation step comprises subjecting the fermentation broth to temperatures between about 70°

C. and about 200°

C.

12. The process according to claim 11, wherein the distillation is carried out with a slurry retention time of between about 0.05 and about 12 hours.

13. The process according to claim 11, wherein the temperatures of the distillation step are between about 70°

C. and about 180°

C.

14. The process according to claim 1, further comprising recycling at least a portion of the fermentation broth back to step (ii).

15. The process according to claim 1, wherein the still bottoms stream has a suspended solids concentration of between about 3 and 40%.

16. The process according to claim 15, wherein the still bottoms stream is concentrated prior to the step of further hydrolyzing.

17. A process for the production of ethanol from a lignocellulosic feedstock which comprises the steps of:

(i) pretreating a lignocellulosic feedstock under conditions to disrupt fiber structure and increase accessibility of the feedstock to being hydrolyzed in order to produce a composition comprising a pretreated lignocellulosic feedstock;

(ii) enzymatically hydrolyzing the pretreated lignocellulosic feedstock with cellulase enzymes to produce a hydrolyzate slurry comprising glucose and unhydrolyzed cellulose;

(iii) fermenting said hydrolyzate slurry to produce a fermentation broth comprising ethanol;

(iv) separating the ethanol from the fermentation broth by distillation to obtain a stream comprising concentrated ethanol and a remaining still bottoms stream comprising unhydrolyzed cellulose, said distillation resulting in heat treatment of the unhydrolyzed cellulose; and

(v) further hydrolyzing at least a portion of the still bottoms stream with cellulase enzymes to convert the unhydrolyzed cellulose to glucose by recycling at least a portion of the still bottoms stream back to step (ii).

18. A process for producing glucose from a lignocellulosic feedstock comprising the steps of:

(i) pretreating the lignocellulosic feedstock under conditions to disrupt fiber structure and increase accessibility of the lignocellulosic feedstock to being hydrolyzed in order to produce a pretreated lignocellulosic feedstock;

(ii) enzymatically hydrolyzing the pretreated lignocellulosic feedstock with cellulase enzymes to produce a hydrolyzate slurry comprising glucose and unhydrolyzed cellulose and fermenting the glucose to produce a fermentation broth comprising alcohol;

(iii) obtaining a process stream comprising the unhydrolyzed cellulose;

(iv) subjecting at least a portion of said process stream to a processing step comprising exposing the unhydrolyzed cellulose to a temperature of between about 70°

C. and about 250°

C., thereby producing a stream comprising heat-treated unhydrolyzed cellulose; and

(v) further hydrolyzing the heat-treated unhydrolyzed cellulose with cellulase enzymes to convert at least a portion of the unhydrolyzed cellulose to glucose.

19. The process according to claim 18, wherein said process stream is the fermentation broth resulting from step (ii).

20. The process according to claim 19, wherein

said processing step is a distillation step which results in a stream comprising concentrated alcohol and a still bottoms stream comprising the unconverted cellulose;

and

said stream comprising the heat-treated unhydrolyzed cellulose is the still bottoms stream.

21. The process according to claim 18, wherein said process stream is the hydrolyzate slurry produced in step (ii) comprising glucose and unhydrolyzed cellulose.

22. The process according to claim 18, wherein the step of further hydrolyzing comprises recycling at least a portion of the hydrolyzate slurry back to step (ii).

23. The process of claim 18, wherein the step of further hydrolyzing comprises introducing at least a portion of the still bottoms stream to a downstream hydrolysis reactor.

24. The process according to claim 18, wherein the pretreatment is carried out with a pH alterant.

25. The process according to claim 24, wherein the pH alterant is acid or alkali.

26. In a process for the production of alcohol from a lignocellulosic feedstock which comprises the steps of a process stream, the improvement which comprises:

subjecting unhydrolyzed cellulose resulting from a previous pretreatment and cellulase hydrolysis of a lignocellulosic feedstock to exposing said unhydrolyzed cellulose in said process stream to conditions which denature bound cellulase enzyme; and

then hydrolyzing said unhydrolyzed cellulose which has been so exposed to said denaturing conditions to glucose by further hydrolysis with cellulase enzymes.

27. The process according to claim 26, wherein said denaturing step comprises exposing the unhydrolyzed cellulose to a temperature of between about 70°

C. and about 250°

C. to denature cellulase enzymes bound to the unhydrolyzed cellulose.

28. The process according to claim 26, wherein said denaturing step comprises exposing the unhydrolyzed cellulose to a change in pH to denature cellulase enzymes bound to the unhydrolyzed cellulose.

29. A process for producing glucose from a lignocellulosic feedstock comprising the steps of:

(i) pretreating the lignocellulosic feedstock under conditions to disrupt fiber structure and increase accessibility of the lignocellulosic feedstock to being hydrolyzed in order to produce a pretreated lignocellulosic feedstock;

(ii) enzymatically hydrolyzing the pretreated lignocellulosic feedstock with cellulase enzymes to produce a hydrolyzate slurry comprising glucose and unhydrolyzed cellulose and fermenting the glucose to produce a fermentation broth comprising alcohol;

(iii) obtaining a process stream comprising the unhydrolyzed cellulose;

(iv) subjecting at least a portion of said process stream to a processing step comprising exposing the unhydrolyzed cellulose to an enzyme denaturing step to denature cellulase enzymes bound to the unhydrolyzed cellulose; and

(v) further hydrolyzing the process stream comprising the unhydrolyzed cellulose subjected to said denaturing step with cellulase enzymes to convert at least a portion of the unhydrolyzed cellulose to glucose.

30. The process according to claim 29, wherein said denaturing step comprises exposing the unhydrolyzed cellulose to a temperature of between about 70°

C. and about 250°

C. to denature cellulase enzymes bound to the unhydrolyzed cellulose.

31. The process according to claim 29, wherein said denaturing step comprises exposing the unhydrolyzed cellulose to a change in pH to denature cellulase enzymes bound to the unhydrolyzed cellulose

32. The process according to claim 29, wherein said process stream is the fermentation broth resulting from step (ii).

33. The process according to claim 32, wherein said denaturing step is a distillation step to obtain a stream comprising concentrated alcohol and a still bottoms stream comprising the unhydrolyzed cellulose, said distillation resulting in heat treatment of the unhydrolyzed cellulose and wherein said still bottoms stream is further hydrolyzed in step (v).

34. The process according to claim 29, wherein said process stream is the hydrolyzate slurry produced in step (ii) comprising glucose and unhydrolyzed cellulose.

35. The process according to claim 34, wherein said denaturing step is a distillation step to obtain a stream comprising concentrated alcohol and a still bottoms stream comprising the unhydrolyzed cellulose, said distillation resulting in heat treatment of the unhydrolyzed cellulose and wherein said still bottoms stream is further hydrolyzed in step (v).

36. The process according to claim 35, wherein the step of further hydrolyzing comprises recycling at least a portion of the hydrolyzate slurry back to step (ii).

37. A process which comprises exposing unhydrolyzed cellulose in a process stream comprising unhydrolyzed cellulose resulting from a previous pretreatment and cellulase hydrolysis of a lignocellulosic feedstock to conditions which denature bound cellulase enzyme and subsequently hydrolyzing said unhydrolyzed cellulose, which has been exposed to such denaturing conditions, to glucose by further hydrolysis with cellulase enzymes.