Organic solvent pretreatment of biomass to enhance enzymatic saccharification

• US 8,460,898 B2
• Filed: 07/02/2012
• Issued: 06/11/2013
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• 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:
  US13/539,696
• Publication Number:
  US 20120270269A1
• Time in Patent Office: 344 Days
• Field of Search: 435/72, 435/106, 435/136, 435/155, 435/157, 435/16, 435/161, 435/163, 536/128
• US Class Current: 435/72
• CPC Class Codes: C08H 8/00 Macromolecular compounds derived from lignocellulosic materials pretreatment thereof B27N
• CPC Class Codes: C10G 2300/1011 Biomass
• CPC Class Codes: C10G 2300/1014 of vegetal origin
• CPC Class Codes: C10G 2300/44 Solvents
• CPC Class Codes: C10G 2300/805 Water
• CPC Class Codes: C10L 1/02 essentially based on components consisting of carbon, hydrogen, and oxygen only
• 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: C12P 7/16 Butanols
• CPC Class Codes: C12P 7/18 polyhydric
• 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: D21C 3/024 with NH3 or H2O
• CPC Class Codes: D21C 3/20 with organic solvents or in solvent environment
• 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
• CPC Class Codes: Y02P 30/20 using bio-feedstock

Abstract

Biomass is pretreated using an organic solvent solution under alkaline conditions in the presence of ammonia and optionally an additional nucleophile to fragment and extract lignin without loss of hemicellulose. 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 fermentable sugars comprising:

(a) providing lignocellulosic biomass comprising lignin, cellulose and hemicellulose;

(b) suspending the biomass of (a) in an organic solvent solution comprising water, ammonia in an amount of about 2% to about 20% relative to weight of dry biomass and one or more nucleophile, whereby a biomass-solvent suspension is formed under alkaline conditions;

(c) heating the biomass-solvent suspension to a temperature of about 100-220°

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

(d) filtering free liquid under pressure after heating the suspension in (c) whereby the dissolved lignin is removed and whereby carbohydrate-enriched biomass with high retention of hemicellulose is produced;

(e) optionally washing the carbohydrate-enriched biomass of (d) with an organic solvent solution producing a solvent-washed carbohydrate-enriched biomass;

(f) removing solvent from the carbohydrate-enriched biomass of (e), or of (d) when (e) is omitted;

wherein a readily saccharifiable carbohydrate-enriched biomass is produced; and

(g) contacting the readily saccharifiable carbohydrate-enriched biomass of (f) with an enzyme consortium,

whereby fermentable sugars are produced.

2. The method of claim 1 wherein removing solvent is by washing with water or drying.

3. The method of claim 1 wherein step (e) is repeated one or more times.

4. The method of claim 1 further comprising fermenting the sugars to produce a target product.

5. The method of claim 4 wherein the target product is selected from the group consisting of alcohols, organic acids, amino acids and gases.

6. The method of claim 5 wherein the target product is selected from the group consisting of ethanol, butanol, or 1,3-propanediol.

7. The method of claim 1, wherein said one or more nucleophile is selected from the group consisting of NaOH, one or more alkylamines, sulfide, hydrosulfide, polysulfide, hydropolysulfide, thiol reagents, and combinations thereof.

8. The method of claim 7 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.

9. The method of claim 8 wherein R is independently methyl, ethyl, propyl or butyl.

10. The method of claim 8 wherein the alkylamine is methylamine.

11. The method of claim 8 wherein the alkylamine is at a concentration of less than about 20% relative to dry weight of biomass.

12. The method of claim 1 wherein the solvent solution to biomass in step (b) has a weight ratio of about 10 to 1 to 0.5 to 1.

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

14. 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.

15. The method of claim 1 wherein the organic solvent solution of (b) further comprises one or more additional components selected from the group consisting of alkali or alkaline earth hydroxides or carbonates, ammonia, thiols, sulfides, hydrosulfides, polysulfides, hydropolysulfides, and combinations thereof.

16. The method of claim 1 wherein the organic solvent solution of (b) and any ammonia or other unreacted components are recyclable.

17. The method of claim 1 wherein the organic solvent solution of (b) and the organic solvent solution of (e) comprise a solvent independently selected from the group consisting of alcohols, diols and aprotic solvents.

18. The method of claim 17 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.

19. The method of claim 18 wherein the organic solvent solution comprises from about 40% to about 70% ethanol in water.