Organic solvent pretreatment of biomass to enhance enzymatic saccharification

• US 8,304,213 B2
• Filed: 12/16/2009
• Issued: 11/06/2012
• Est. Priority Date: 12/19/2008
• Status: Expired due to Fees

• Current Assignee: Sustainable Technology Corporation
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Diner, Bruce A., Fan, Janine
• Primary Examiner(s): Lilling, Herbert J
• Application Number:
  US12/639,045
• Publication Number:
  US 20100159518A1
• Time in Patent Office: 1,056 Days
• Field of Search: 435/72, 435/136, 435/155, 435/158, 435/160, 435/161, 536/18, 536/128
• US Class Current: 435/72
• CPC Class Codes: C08H 6/00 Macromolecular compounds derived from lignin, e.g. tannins, humic acids
• CPC Class Codes: C08H 8/00 Macromolecular compounds derived from lignocellulosic materials pretreatment thereof B27N
• CPC Class Codes: C12P 2201/00 Pretreatment of cellulosic or lignocellulosic material for subsequent enzymatic treatment or hydrolysis
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: D21C 11/0007 Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for volatile compounds obtained by decomposition of spent liquors in order to regenerate them D21C11/125; compounds obtained by fractionating the liquors in order to regenerate them D21C11/0042
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

Biomass is pretreated using an organic solvent solution under alkaline conditions in the presence of one of more sulfide (hydrosulfide) salt and optionally one or more additional nucleophile to fragment and extract lignin. Pretreated biomass is further hydrolyzed with a saccharification enzyme consortium. Fermentable sugars released by saccharification may be utilized for the production of target chemicals by fermentation.

Claims

1. A method for producing carbohydrate-enriched biomass comprising:

(a) providing lignocellulosic biomass comprising lignin;

(b) contacting the biomass of (a) in an organic solvent solution comprising water and one or more sulfide salt under alkaline conditions whereby a biomass-solvent suspension is formed;

(c) heating the biomass-solvent suspension to a temperature of about 100°

C. to about 220°

C. for about 5 minutes to about 5 hours whereby lignin is fragmented and is dissolved in the suspension; and

(d) filtering free liquid whereby the dissolved lignin is removed and whereby carbohydrate-enriched biomass is produced.

2. The method of claim 1 further comprising:

(e) washing the biomass produced in step (d) with an organic solvent.

3. The method of claim 2, further comprising:

(f) washing the biomass produced in step (e) with water to produce readily saccharifiable carbohydrate-enriched biomass.

4. The method of claim 2 further comprising drying biomass produced in step (e) to produce readily saccharifiable carbohydrate-enriched biomass.

5. The method of claim 3, further comprising repeating steps (e) and (f) one or more times.

6. The method of claim 1 wherein the heating step of (c) occurs in a sealed pressure vessel.

7. The method of claim 1 wherein the filtering step of (d) occurs under pressure.

8. The method of claim 1 wherein the organic solvent solution further comprises an additional nucleophile selected from the group consisting of NH₃, one or more alkylamines, NaOH, and combinations thereof.

9. The method of claim 8 wherein the additional nucleophile is one or more alkylamine and said one or more alkylamine is at a concentration of about up to 20% by weight of dry biomass.

10. The method of claim 1 wherein in step (b) the biomass dry weight is at an initial concentration of at least about 9% up to about 80% of the weight of the biomass-solvent suspension.

11. The method of claim 1, wherein the heated suspension of step (c) is cooled to room temperature before filtering in step (d).

12. The method of claim 2 further comprising evaporating off the solvent under vacuum of the filtered and washed biomass after step (e).

13. The method of claim 3, 4 or 12, further comprising saccharifying the biomass with an enzyme consortium whereby fermentable sugars are produced.

14. The method of claim 3, further comprising saccharifying the biomass without drying by contacting said biomass with an enzyme consortium after washing in step (f), whereby fermentable sugars are produced.

15. The method of claim 13 or 14, further comprising fermenting the sugars to produce a target product.

16. The method of claim 15 wherein the target product is selected from the group consisting of alcohols, organic acids, amino acids and gases.

17. The method of claim 1 wherein the biomass is selected from the group consisting of switchgrass, waste paper, sludge from paper manufacture, corn fiber, corn cobs, corn husks, corn stover, grasses, wheat, wheat straw, hay, barley, barley straw, rice straw, sugar cane bagasse, sugar cane straw, yellow poplar, sorghum, soy, components obtained from processing of grains, trees, branches, roots, leaves, wood chips, sawdust, shrubs and bushes, vegetables, fruits, flowers, animal manure and combinations thereof.

21. The method of any one of claim 1 or 18, wherein the organic solvent solution further comprises one or additional component selected from the group consisting of alkali or alkaline earth hydroxides or carbonates, ammonia, thiols, and combinations thereof.

22. The method of claim 1 or 18 wherein the solvent solution, and any unreacted sulfide salts or other unreacted components are recyclable.

23. The method of claim 1 wherein said organic solvent solution comprises a solvent selected from the group consisting of alcohols, diols and aprotic solvents.

24. The method of claim 23 wherein the organic solvent solution comprises a solvent selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol and hexanol, isomers thereof, and diols thereof.

25. The method of claim 1 or 18 wherein the lignocellulosic biomass of step (a) has a carbohydrate content that is highly conserved through steps (a) through (d).

29. The method of claim 1 or 18 where the sulfide salt is selected from the group consisting of alkali metal and alkaline earth sulfides (e.g. Na₂S), alkali metal and alkaline earth hydrosulfides (e.g. NaHS), alkali metal and alkaline earth polysulfides (e.g., Na₂S_n), alkali metal and alkaline earth hydropolysulfides (e.g., NaHS_n), ammonium sulfide, hydrosulfide, polysulfides, and hydropolysulfides, alkylammonium sulfide, hydrosulfide, polysulfides, and hydropolysulfides.

30. The method of claims 1 and 18 wherein the temperature of step (c) is from about 165°

C. to about 195°

C.

18. A method of simultaneous fragmentation and selective extraction of lignin from lignocellulosic biomass to produce a substantially lignin-free biomass comprising:

(a) providing;

1) an amount of lignocellulosic biomass;

2) a multi-component organic solvent solution comprising from about 40% to about 70% ethanol in water;

3) one or more sulfide salt(s); and

4) one or more alkylamine(s) under alkaline conditions;

(b) contacting said biomass with the multi-component solvent solution of (a) whereby a solvent-biomass mixture is produced;

(c) placing the solvent-biomass mixture in a sealed pressure vessel whereby the mixture of (b) is heated from about 100°

C. to about 220°

C. for about 5 minutes to about 5 hours whereby lignin is fragmented and dissolved in the solvent;

(d) removing the dissolved lignin of (c) by filtration; and

(e) washing the residual biomass with organic solvent, whereby substantially lignin-free biomass is produced.

19. The method of claim 18 wherein the solvent at step (e) may contain water.

20. The method of claim 18 wherein the substantially lignin-free biomass is from about 60% to about 100% original weight of the biomass.

26. The method of claim 8 or 18 wherein the one or more alkylamines is selected from the group consisting of R—

NH₂, R₂—

NH, R₃N, (H₂N—

R—

NH₂), (H₂N—

R(NH₂)₂), (HO—

R—

NH₂), ((HO)₂—

R—

NH₂), (HO—

R—

(NH₂)₂), (HS—

R—

NH₂), ((HS)₂—

R—

NH₂), (HS—

R—

(NH₂)₂) and (H₂N—

R(OH)(SH) and combinations thereof, wherein R is independently a monovalent, divalent or trivalent 1-6 carbon alkane, alkene or alkyne, linear, cyclic or branched.

27. The method of claim 26 wherein R is independently methyl, ethyl, propyl or butyl.

28. The method of claim 26 wherein the alkylamine is methylamine.