Method of processing lignocellulosic feedstock for enhanced xylose and ethanol production

• US 20070148751A1
• Filed: 01/31/2007
• Published: 06/28/2007
• Est. Priority Date: 02/28/2001
• Status: Active Grant

• Current Assignee: Iogen Energy Corporation (Iogen Corporation)
• Original Assignee: Iogen Energy Corporation (Iogen Corporation)
• Inventors: Griffin, Robert, Nicholson, Colin, Mott, Corinne, Tolan, Jeffrey, Anand, VIjay
• Granted Patent: US 7,993,463 B2
• Time in Patent Office: Days
• US Class Current: 435/161
• 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

1-32. -32. (canceled)

33. A pretreated feedstock produced according to a method comprising the steps of:

a) leaching a lignocellulosic feedstock, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes 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 the pretreated feedstock.

34-35. -35. (canceled)

36. A lignocellulosic composition produced according to a method comprising the steps of:

a) leaching a lignocellulosic feedstock, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes 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 the lignocellulosic composition comprising xylose and a pretreated feedstock.

37-42. -42. (canceled)

43. A method of producing ethanol from a lignocellulosic feedstock comprising greater than about 20% (w/w) cellulose, said method comprising:

a) leaching said lignocellulosic feedstock, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes 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;

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 from a lignocellulosic feedstock comprising greater than about 20% (w/w) cellulose, said method comprising:

a) leaching said lignocellulosic feedstock, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes 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 from a lignocellulosic feedstock comprising greater than about 20% (w/w) cellulose, said method comprising:

a) leaching said lignocellulosic feedstock, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes 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;

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. A method for preparing a lignocellulosic feedstock comprising:

a) preconditioning said lignocellulosic feedstock to produce a preconditioned feedstock;

b) incubating said preconditioned feedstock within a leaching bath to produce a leached feedstock; and

c) crushing said leached feedstock to produce a pressate and a solid feedstock.

47. The method of claim 46, wherein said step of preconditioning (step a)) comprises heating said lignocellulosic feedstock by steam to about 80°

C. for about 1 minute.

48. The method of claim 46, wherein in said step of incubating (step b)) debris is removed from said leaching bath.

49. The method of claim 46, wherein in said step of incubating (step b)), said preconditioned feedstock is incubated from about 5 to about 30 minutes.

50. The method of claim 46, wherein in said step of crushing (step c)), said pressate comprises soluble protein which is further processed for animal feed.

51. A lignocellulosic feedstock processing system comprising:

a feedstock handling device; and

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.

52. A method of producing a fermentation product from a lignocellulosic feedstock comprising greater than about 20% (w/w) cellulose, said method comprising:

(a) leaching said lignocellulosic feedstock, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes to produce a leached feedstock and a leachate;

(c) removing said leachate from said leached feedstock;

(d) pretreating the leached feedstock to produce a composition comprising xylose, a pretreated feedstock, or both xylose and a pretreated feedstock; and

(e) further processing the composition comprising xylose, the pretreated feedstock, or both xylose and the pretreated feedstock to produce the fermentation product, said product selected from the group consisting of ethanol, lactic acid, sorbitol, acetic acid, citric acid, ascorbic acid, propanediol, butanediol, acetone, butanol, and a combination thereof, said processing comprising producing glucose by cellulose hydrolysis of the pretreated feedstock and fermenting the glucose to produce said fermentation product.

53. The method of claim 52, further comprising cellulase treating said pretreated feedstock.

54. The method of claim 52, wherein said step of further processing the composition comprises fermenting the glucose to ethanol.

55. The method of claim 52, wherein said step of further processing the composition comprises fermenting the glucose to butanol.

56. The method of claim 52, wherein said step of further processing the composition comprises fermenting the glucose to lactic acid.

57. The method of claim 52, wherein said lignocellulosic feedstock is selected from the group consisting of a C4 grass, sugar beet 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.

58. The method of claim 52, wherein the lignocellulosic feedstock is mechanically disrupted.

59. The method of claim 58, wherein said mechanically disrupted feedstock is capable of passing through about 20 mesh.

60. The method of claim 58, wherein said feedstock is mechanically disrupted by shredding, milling, chopping, chipping, grinding, or a combination thereof.

61. The method of claim 60, wherein said milling comprises Szego milling, Hammer milling, Wiley milling, or a combination thereof.

62. The method of claim 52, wherein said leaching is performed for a period between about 2 minutes and about 2 hours.

63. The method of claim 52, 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.

64. The method of claim 63, wherein said volume is about 1.5 to about 3 times the maximum water holding capacity of said feedstock.

65. The method of claim 52, wherein said aqueous solution is of a pH from about 3 to about 9.

66. The method of claim 52, wherein said leaching comprises a plurality of leaching stages.

67. The method of claim 66, wherein said leaching stages comprise 2 to 4 leaching stages.

68. The method of claim 66, wherein said plurality of leaching stages is performed in countercurrent fashion.

69. The method of claim 52, wherein said leaching removes buffering agents from the lignocellulosic feedstock.

70. The method of claim 69, wherein said leaching removes between about 50% to about 100% of the total leachable buffering agents from the lignocellulosic feedstock.

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

72. The method of claim 71, wherein said leaching removes between about 90% to about 100% of the total leachable buffering agents from the lignocellulosic feedstock.

73. The method of claim 52, wherein said pretreated feedstock has increased accessibility to being digested during a treatment with cellulase enzymes.

74. The method of claim 52, wherein said feedstock comprises a cellulose content in an amount greater than about 30% (w/w).

75. The method of claim 74, wherein said feedstock comprises a lignin content in an amount greater than about 5% (w/w).

76. The method of claim 52, wherein said feedstock comprises a combined sugar content of sucrose, fructose and starch of less than about 20% (w/w).

77. The method of claim 57, wherein said lignocellulosic feedstock comprises oat hulls, wheat straw, switch grass, or a combination thereof.

78. The method of claim 52, wherein, in said step of leaching, said feedstock is incubated from about 5 to about 30 minutes.

79. The method of claim 52, wherein, in said step of removing, said leachate comprises soluble protein which is further processed for animal feed.

80. The method of claim 52, wherein said leaching is performed at a temperature between about 4°

C. and about 95°

C.

81. The method of claim 80, wherein said temperature is between about 20°

C. and about 80°

C.

82. The method of claim 81, wherein said temperature is between about 60°

C. and about 80°

C.

83. The method of claim 52, wherein following said step of removing said leachate, is a step of acidifying said leached feedstock to a pH between about 0.5 and about 3 to produce an acidified feedstock.

84. The method of claim 52, wherein said step of pretreating comprises reacting said leached feedstock at a temperature between about 100°

C. and about 220°

C. and a pH between about 0.5 and 2.5 for about 5 seconds to about 60 minutes.

85. The method of claim 83, wherein said acidifying is performed using an acid selected from the group consisting of sulfuric acid, nitric acid and hydrochloric acid.