Biomass pretreatment

• US 20080227162A1
• Filed: 03/13/2008
• Published: 09/18/2008
• Est. Priority Date: 03/14/2007
• Status: Active Grant

• Current Assignee: Suganit Systems, Inc., University of Toledo
• Original Assignee: Suganit Systems, Inc.
• Inventors: Anderson, Jared, Rao, Kripa, Varanasi, Sasidhar, Schall, Constance Ann, Dadi, Anantharam Prasad
• Granted Patent: US 8,030,030 B2
• Time in Patent Office: Days
• US Class Current: 435/96
• 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: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

A method for lignocellulose conversion to sugar with improvements in yield and rate of sugar production has been developed by using ionic liquid pretreatment. This new pretreatment strategy substantially improves the efficiency (in terms of yield and reaction rates) of saccharification of lignocellulosic biomass. Cellulose and hemicellulose, when hydrolyzed into their sugars, can be converted into ethanol fuel through well established fermentation technologies. These sugars also form the feedstocks for production of variety of chemicals and polymers. The complex structure of biomass requires proper pretreatment to enable efficient saccharification of cellulose and hemicellulose components to their constituent sugars. Current pretreatment approaches suffer from slow reaction rates of cellulose hydrolysis (by using the enzyme cellulase) and low yields.

Claims

1. A method for the conversion of lignocellulosic biomass to sugars comprising the steps of:

providing any lignocellulosic biomass comprising ligin, cellulose, and hemicellulose as major components;

incubating the biomass in an ionic liquid (IL) for a sufficient time at an appropriate temperature to remove or redistribute a substantial portion of the lignin so that the IL is able to penetrate the hemicellulose as well as the crystalline cellulose buried in the hemicellulose and swell these structures significantly;

replacing all or most of the IL from the biomass by washing the IL-incubated biomass with a liquid non-solvent for cellulose that is miscible with the IL and water;

contacting the above washed biomass in an aqueous buffered melieu containing enzymes capable of hydrolyzing both cellulose and hemicellulose and converting a substantial portion of these polysaccharides to hexose and pentose sugars.

4. A method according to claim 1 wherin the sugars from the hydrolysis can be converted to fuels, chemicals, polymers and other materials.

6. A method according to claim 1 wherein the time and temperature during the step of IL-incubation of biomass is optimized so as to minimize the dissolution of hemicellulose and cellulose portions of biomass in the IL, while swelling these matrices sufficiently to enhance the penetration of hydrolyzing enzymes and water during the hydrolysis step.

7. A method according to claim 1 further comprising the step of washing the pretreated biomass with a non-solvent of cellulose that is miscible with the IL prior to the step of converting the biomass to sugar.

9. A method according to claim 1 wherein the step of pretreating incubates the biomass for a time ranging from 5 minutes to 8 hours at a temperature ranging from 50°

C. to 200°

C.

10. A method according to claim 1 wherein the ionic liquid is molten during incubation.

11. A method according to claim 1 wherein the IL is any ionic liquid that is capable of disrupting the hydrogen-bonding structure of cellulose or hemicelullose represented by a cation structure that includes imidazolium, pyrroldinium, pyridinium, phosphonium, or ammonium and all functionalized analogs thereof.

12. A method according to claim 1 wherein the IL is represented by the structure:

13. A method according to claim 1 wherein the IL is represented by the structure:

14. A method according to claim 12 and 13 wherein the halide is a chloride, fluoride, bromide or iodide.

15. A method according to claim 1 wherein the IL is 1-n-butyl-3-methylimidazolium chloride, 1-allyl-3-methyl imidazolium chloride, 3-methyl-N-butylpyridinium chloride, 1-ethyl-3-methyl imidazolium acetate, or 1-ethyl-3-methyl imidazolium propionate.

19. A method according to claim 4 wherein the cellulase is a mix of endo-gluconases, exo-glucanases, and β

-glucosidases.

wherein the enzyme mixture can be modified to include other enzymes such as xylanases, arabinases, or simplified from conventional cellulase systems to achieve hydrolysis of IL-treated biomass.

20. A method according to claim 4 wherein the cellulase is supplemented with β

-glucosidase.

21. A method according to claim 4 wherein the improved hydrolysis rates allows saccharification with low enzyme loadings.

22. A method according to claim 4 wherein enzymes can be recovered from biomass hydrolysates.

23. A method according to claim 1 wherein the cellulose is converted to six carbon sugars.

24. A method according to claim 1 wherein the hemicellulose is converted to five and six carbon sugars.

25. A method according to claim 1 wherein the optimal contact time and temperature during the IL-incubation step might depend on the means of heating during incubation.

26. A method according to claim 1 wherein the optimal contact time and temperature during the IL-incubation step will change depending on the size and nature of the biomass particles used.

wherein large particles of wide size distribution can be effectively pretreated with ionic liquid.

27. A method according to claim 1 wherein the time required for complete enzymatic hydrolysis is within 16 to 36 hours for two of the representative biomass samples—

corn stover, poplar.

28. A method according to claim 1 wherein the incubation of biomass with ionic liquid can tolerate at least 10% dissolved water.

29. A method according to claim 1 wherein the swelling is at least 30%.

31. A method according to claim 25 wherein the optimal conditions might vary depending on whether the mixture was subjected to conventional heating with agitation or microwave irradiation with intermittent agitation.

32. A method according to claim 1 wherein an ionic liquid mixture with a composition described by Equation 1 can be used:

2. A method for the disruption of the structure of lignocellolosic biomass and swelling of the cellulose and hemicellulose portions comprising the steps of:

incubating the biomass in an ionic liquid (IL) for a sufficient time at an appropriate temperature to remove or redistribute a substantial portion of the lignin so that the IL is able to penetrate the hemicellulose as well as the crystalline cellulose buried in the hemicellulose and swell these structures significantly;

replacing all or most of the IL from the biomass by washing the IL-incubated biomass with a liquid non-solvent for cellulose that is miscible with the IL and water;

processing the above washed biomass with appropriate chemical and biochemical reagents to affect the conversion of the swollen biomass to useful chemicals efficiently.

3. A method according to claim 2 wherin the post-saccharification solid residue is predominantly lignin, thus providing a method of its separation.

5. A method according to claim 3 wherin the lignin can be converted to fuels, chemicals, polymers and other materials.

8. A method according to claim 3 further comprising the step of adding cellulase to the washed biomass to hydrolyze the cellulose and hemicellulose to sugar.

16. A method according to claim 3 wherein the wash-solvent is water, an alcohol or acetonitrile or any solvent which dissolves the IL and thereby extracts the IL from the biomass.

17. A method according to claim 16 wherein the alcohol is ethanol or methanol or butanol or propanol.

wherein the IL can be recovered from the wash-solvent and any dissolved biomass components from the wash-step through suitable separation methods including one or more of the following:

activated charcoal treatment, distillation, membrane separation, electro-chemical separation techniques, solid phase extraction, and liquid-liquid extraction.

18. A method according to claim 17 wherein the IL recovered will be reused for pretreatment of more biomass.

30. A method according to claim 2 wherein the swelling is at least 30%.