Method of processing lignocellulosic feedstock for enhanced xylose and ethanol production

• US 20040231661A1
• Filed: 01/12/2004
• Published: 11/25/2004
• Est. Priority Date: 02/28/2001
• Status: Active Grant

• Current Assignee: Iogen Energy Corporation (Iogen Corporation)
• Original Assignee: Iogen Energy Corporation (Iogen Corporation)
• Inventors: Anand, Vijay, Tolan, Jeffrey S., Griffin, Robert, Nicholson, Colin, Mott, Corinne
• Granted Patent: US 7,901,511 B2
• Time in Patent Office: Days
• US Class Current: 127/1
• CPC Class Codes: A23L 33/21 Addition of substantially indigestible substances, e.g. dietary fibres
• CPC Class Codes: C12P 19/02 Monosaccharides 2-ketogulonic acid C12P7/60
• 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 2201/00 Pretreatment of cellulosic or lignocellulosic material for subsequent enzymatic treatment or hydrolysis
• 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

Abstract

The present invention provides a method of producing xylose from lignocellulosic feedstock. The method comprises disrupting lignocellulosic feedstock; leaching the lignocellulosic feedstock by contacting the feedstock with at least one aqueous solution for a period greater than about 2 minutes to produce a leached feedstock and a leachate; removing the leachate from the leached feedstock; acidifying the leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock, and; reacting the acidified feedstock under conditions which disrupt fiber structure and hydrolyze a portion of hemicellulose and cellulose of the acidified feedstock, to produce a composition comprising xylose and a pretreated feedstock. The xylose may be purified from the pretreated feedstock or it may be converted to ethanol with the pretreated feedstock.

Claims

1. A method of producing xylose comprising,

a) leaching a lignocellulosic feedstock prior to any pre-treatment of the feedstock, the feedstock comprising greater than about 20% (w/w) cellulose and having a temperature of about 20°

C. to about 80°

C., said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes at a temperature of about 25°

C. to about 80°

C. to produce a leached feedstock and a leachate;

b) removing said leachate from said leached feedstock; and

c) reacting said leached feedstock under conditions which disrupt fiber structure and hydrolyze a portion of hemicellulose and cellulose of said leached feedstock, to produce a composition comprising xylose and a pretreated feedstock.

2. The method of claim 1, wherein following said step of removing (step b)), is a step of acidifying said leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock.

3. The method of claim 2, wherein said lignocellulosic feedstock is selected from the group consisting of a C4 grass, sugar cane bagasse, soybean stover, corn stover, rice straw, rice hulls, barley straw, corn cobs, wheat straw, oat hulls, corn fiber, wood fiber, and a combination thereof, said C4 grass selected from the group consisting of switch grass, cord grass, rye grass, miscanthus, and a combination thereof.

4. The method of claim 3, wherein said lignocellulosic feedstock comprises mechanically disrupted feedstock.

5. The method of claim 4, wherein said mechanically disrupted feedstock is capable of passing through about 20 mesh.

6. The method of claim 3, wherein said lignocellulosic feedstock comprises an AX/NSP ratio of about 0.35 to about 0.45.

7. The method of claim 6, wherein said feedstock comprises wheat straw, wheat chaff, switch grass, corn stover, corn cobs, oat hulls, or a combination thereof.

8. The method of claim 4, wherein said disrupted feedstock is produced by shredding, milling, chopping, chipping, grinding or a combination thereof.

9. The method of claim 8, wherein said milling comprises Szego milling, Hammer milling, Wiley milling, or a combination thereof.

10. The method of claim 2, wherein said leaching is performed for a period between about 2 minutes and about 2 hours.

14. The method of claim 2, wherein said leaching comprises contacting said lignocellulosic feedstock with an aqueous solution, said aqueous solution comprising a volume of about 0.25 times the maximum water holding capacity of said feedstock to about 10 times the maximum water holding capacity of said feedstock.

15. The method of claim 14, wherein said volume is about 1.5 to 3 times the maximum water holding capacity of said feedstock.

16. The method of claim 2 wherein said aqueous solution comprises water, mill water, process water, a leachate or a combination thereof.

17. The method of claim 16, wherein said aqueous solution is of a pH from about 3 to about 9.

18. The method of claim 17, wherein said pH is adjusted using NaOH, H₂SO₄, or a combination thereof.

19. The method of claim 2, wherein said leaching comprises a plurality of leaching stages.

20. The method of claim 19, wherein said leaching stages comprise 2 to 4 leaching stages.

21. The method of claim 19 wherein said plurality of leaching stages are performed in countercurrent fashion.

22. The method of claim 2, wherein said leaching removes between about 50% to about 100% of the total leachable buffering agents from the lignocellulosic feedstock.

23. The method of claim 2, wherein said leaching removes between about 70% to about 100% of the total leachable buffering agents from the lignocellulosic feedstock.

24. The method of claim 23, wherein said leaching removes between about 90% to about 100% of the total leachable buffeting agents from the lignocellulosic feedstock.

25. The method of claim 2, wherein said acidifying is performed using an acid selected from the group consisting of sulfuric acid, nitric acid and hydrochloric acid.

26. The method of claim 25, wherein said acid is sulfuric acid.

27. The method of claim 2, wherein said leachate is sampled during leaching, following leaching or both, and said leaching parameters are adjusted accordingly.

28. The method of claim 2, wherein the composition comprising xylose comprises xylose polymer, xylose monomer or a combination thereof.

29. The method of claim 2, wherein said composition produced from said method comprises a xylose concentration in the range of about 150 mg to about 260 mg of xylose per gram of feedstock.

30. The method of claim 2, wherein said pretreated feedstock has increased accessibility to being digested during a treatment with cellulase enzymes.

31. The method of claim 1, wherein said method further comprises cellulase treatment of said pretreated feedstock.

32. The method of claim 2, wherein said method further comprises cellulase treatment of said pretreated feedstock.

33. A pretreated feedstock produced according to the method of claim 1.

34. A pretreated feedstock produced according to the method of claim 2.

35. The method of claim 2 wherein said aqueous solution comprises less than about 10 g/l impurities.

36. A lignocellulosic composition produced according to the method of claim 1.

37. A lignocellulosic composition produced according to the method of claim 2.

38. The method of claim 1 wherein said feedstock comprises cellulose in an amount greater than about 30% (w/w).

39. The method of claim 1 wherein said feedstock comprises a lignin content in an amount greater than about 5% (w/w).

40. The method of claim 1, wherein said feedstock comprises a combined sugar content of sucrose, fructose and starch of less than about 20% (w/w).

41. The method of claim 1, wherein said lignocellulosie feedstock comprises oat hulls, wheat straw, switch grass, or a combination thereof.

47. The method of claim 1, wherein prior to said step of leaching (step a)) said lignocellulosic feedstock is heated to about 80°

C. for about 1 minute.

48. The method of claim 1, wherein in said step of leaching (step a)), debris is removed.

49. The method of claim 1, wherein in said step of leaching (step a)), said feedstock is incubated from about 5 to about 30 minutes.

50. The method of claim 1, wherein in said step of removing (step b)), said leachate comprises soluble protein which is further processed for animal feed.

11-13. -13. (cancelled)

42. A method of producing xylose comprising,

a) leaching a mechanically disrupted lignocellulosic feedstock prior to any pretreatment of the feedstock, the feedstock comprising greater than about 20% (w/w) cellulose and having a temperature of about 20°

C. to about 80°

C., said leaching comprising contacting said feedstock with at least one aqueous solution for a period of about 2 minutes to about 2 hours at a temperature of about 25°

C. to about 80°

C. using a volume of aqueous solution which is between about 0.25 and about 10 times the maximum water holding capacity of said disrupted lignocellulosic feedstock, to produce a leached feedstock and a leachate;

b) removing said leachate from said leached feedstock;

c) acidifying said leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock; and

d) reacting said acidified feedstock under conditions which disrupt fiber structure and hydrolyse a portion of hemicellulose and cellulose of said acidified feedstock, to produce a composition comprising xylose and a pretreated feedstock.

43. A method of producing ethanol comprising,

a) leaching a lignocellulosic feedstock prior to any pretreatment of the feedstock, the feedstock comprising greater than about 20% (w/w) cellulose and having a temperature of about 20°

C. to about 80°

C., said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes at a temperature of about 25°

C. to about 80°

C. to produce a leached feedstock and a leachate;

b) removing said leachate from said leached feedstock;

c) acidifying said leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock;

d) reacting said acidified feedstock under conditions which disrupt fiber structure and hydrolyze a portion of hemicellulose and cellulose of said acidified feedstock, to produce a composition comprising xylose and a preheated feedstock;

e) treating said composition comprising xylose and pretreated feedstock with cellulase under conditions which hydrolyse cellulose in said pretreated feedstock to glucose, producing a sugar solution comprising xylose and glucose; and

f) fermenting said sugar solution to ethanol.

44. A method of producing ethanol comprising,

a) leaching a lignocellulosic feedstock prior to any pretreatment of the feedstock, the feedstock comprising greater than about 20% (w/w) cellulose and having a temperature of about 20°

C. to about 80°

C., said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes at a temperature of about 25°

C. to about 80°

C. to produce a leached feedstock and a leachate;

b) removing said leachate from said leached feedstock;

c) acidifying said leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock;

d) reacting said acidified feedstock under conditions which disrupt fiber structure and hydrolyze a portion of hemicellulose and cellulose of said acidified feedstock, to produce a composition comprising xylose and a pretreated feedstock; and

e) treating said composition with a microrganism under conditions which permit fermentation of said xylose in said composition to ethanol.

45. A method of producing ethanol comprising,

a) leaching a lignocellulosic feedstock prior to any pretreatment of the feedstock, the feedstock comprising greater than about 20% (w/w) cellulose and having a temperature of about 20°

C. to about 80°

C., said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes at a temperature of about 25°

C. to about 80°

C. to produce a leached feedstock and a leachate;

b) removing said leachate from said leached feedstock;

c) acidifying said leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock;

d) reacting said acidified feedstock under conditions which disrupt fiber structure and hydrolyze a portion ofhemicellulose and cellulose of said acidified feedstock, to produce a composition comprising xylose and a pretreated feedstock;

e) separating said pretreated feedstock from said composition;

f) treating said pretreated feedstock with cellulase under conditions which hydrolyse cellulose in said pretreated feedstock to glucose, producing a sugar solution comprising glucose; and

g) fermenting said sugar solution to ethanol.

46. (cancelled)

51. A lignocellulosic feedstock processing system comprising, a feedstock handling device;

a preconditioner capable of receiving said feedstock from said handling device, said preconditioner in communication with a steam source, said steam source for heating said feedstock, a first transfer device, for conveying said feedstock within, and from, said preconditioner to a leaching bath, a second transfer device for mixing said feedstock within said leaching bath and conveying said feedstock from said leaching bath to a press, a third transfer device for conveying pressed feedstock from said press to a second leach stage, and multi-press, to produce processed lignocellulosic feedstock.