Process for enzymatically converting a plant biomass

• US 20090042259A1
• Filed: 08/08/2008
• Published: 02/12/2009
• Est. Priority Date: 08/09/2007
• Status: Abandoned Application

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Chundawat, Shishir, Dale, Bruce E., Teymouri, Farzaneh, Balan, Venkatesh
• Application Number:
  US12/221,972
• Publication Number:
  US 20090042259A1
• Time in Patent Office: Days
• US Class Current: 435/105
• 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

Abstract

The present invention describes a process for at least a 90% conversion of a plant biomass preferably by a reduction of the units of cellulase needed and by using a xylanase which acts synergistically with the cellulase to improve the yield of xylose and glucose as sugars. The process enables greater conversion of a lignocellulosic plant biomass to glucose and xylose for use as animal feeds and as fermentation as medium for producing ethanol.

Claims

1. A process for converting disrupted lignocellulosic plant biomass to sugars comprising xylose and glucose, the process comprising:

(a) providing a plant biomass comprising;

(i) cell walls comprising xylans, glucans and pectins; and

(ii) glucans inside the cell walls; and

(b) adjusting a ratio of enzymatic activity of a glucanase to a hemicellulase so that at least 90% by weight of available cellulose and the xylans in the cell wall of the plant biomass are converted to the sugars.

2. The process of claim 1 wherein the plant biomass material is corn stover.

3. The process of claim 1 wherein the ratio of filter paper cellulase units (FPU) as the glucanase to units of hemicellulase is between about 10 to 1 and 2 to 1.

4. The process of claims 1 or 2 wherein the plant biomass is treated with an AFEX process step to disrupt the plant biomass.

5. The process of claims 1 and 2 wherein a reduced amount of the glucanase and the hemicellulase over an amount of each enzyme alone needed to achieve the 90% by weight conversion is used for the converting.

6. The process of any one of claims 1, 2 or 3 wherein the biomass is washed in a liquid after an AFEX process step to remove phenolics in the liquid.

7. The process of any one of claims 1, 2 or 3 with a loading of 7.5 FPU of cellulase as the glucanase and xylanase as the hemicellulase per gram of available glucans and xylans.

8. The process of any one of claims 1, 2 or 3 wherein 5 to 15 International units of xylanase as a hemicellulase and 5 to 15 filter paper units of cellulase as the glucanase are used to achieve the 90% by weight conversion.

9. The process of claim 1 wherein a weight of units of the cellulase as the glucanase with xylanase as the hemicellulase per gram of cellulose and xylan in the plant biomass is less than a weight of units of cellulase alone to achieve the 90% by weight conversion.

10. The process of claim 2 wherein the corn stover is pre-milled to reduce particle size of the biomass to be between 0.05 mm to 0.85 mm.

11. The process of claim 1, wherein step (b) further comprises adjusting a ratio of enzymatic activity by providing a pectinase in addition to the glucanase and the hemicellulase.

12. The process of claim 1 wherein the hemicellulase comprises at least one of xyloglucanase, β

-xylosidase, endoxylanase, α

-l-arabinofuranosidase, α

-glucuronidase, and acetyl xylan esterase.

13. The process of claim 10 wherein the plant biomass is treated with an AFEX process step to expose the xylans and cellulose and then milled to a reduced particle size.

14. The process of claim 4 wherein the AFEX treatment comprises the steps of:

(a) providing the biomass with 60% moisture to a high-pressure reactor with liquid ammonia to a vessel;

(b) raising and maintaining the temperature of the vessel to 90°

C. for up to five minutes; and

(c) explosively relieving the pressure to cause a pressure drop such that the ammonia vaporizes causing explosive decompression of the biomass and fiber disruption.

15. A process for converting a disrupted lignocellulosic plant biomass comprising xylan and cellulose to xylose and glucose, which comprises:

adjusting a ratio of enzymatic activity of cellulase to hemicellulase so that at least 90% by weight of available cellulose and xylan in the plant biomass is converted to glucose and xylose.

16. The process of claim 15 wherein the plant biomass material is corn stover.

17. The process of claim 15 wherein the ratio of filter paper cellulase units (FPU) for cellulase to units of hemicellulase is between about 10 to 1 and 2 to 1.

18. The process of claims 15 or 16 wherein the plant biomass is treated with an AFEX process step to expose the xylan and cellulose.

19. The process of claim 15 and 16 wherein a reduced amount of cellulase with hemicellulase and an amount of cellulase alone needed to achieve the 90% by weight conversion is used for the converting.

20. The process of any one of claims 15, 16 or 17 wherein the biomass is washed after an AFEX process step to remove a liquid comprising phenolics.

21. The process of any one of claims 15, 16 or 17 with a loading of 7.5 FPU of cellulase and hemicellulase per gram of available glucan and xylan.

22. The process of any one of claims 15, 16 or 17 wherein 5 to 15 International units of hemicellulase to xylan loadings and 5 to 15 filter paper units of cellulase are used to achieve the 90% by weight conversion.

23. The process of claim 15 wherein a weight of units of the cellulase with hemicellulase per gram of glucan and xylan in the plant biomass is less than a weight of units of cellulase alone to achieve the 90% by weight conversion.

24. The process of claim 16 wherein the corn stover is pre-milled to reduce particle size of the biomass.

25. The process of claim 24 wherein the particle size is reduced to be between 0.05 mm to 0.85 mm.

26. The process of claim 25 wherein the particle size is reduced to be between 0.15 mm to 0.5 mm.

27. The process of claim 24 wherein the plant biomass is treated with an AFEX process step to expose the xylan and cellulose and then milled to a reduced particle size.

28. The process of claim 18 wherein the AFEX treatment is a pretreatment to the biomass prior to enzymatic hydrolysis comprising the steps of:

(a) providing the biomass with 60% moisture to a high-pressure reactor with liquid ammonia to a vessel;

(b) raising and maintaining the temperature of the vessel to 90°

C. for up to five minutes; and

(c) explosively relieving the pressure to cause a pressure drop such that the ammonia vaporizes causing explosive decompression of the biomass and fiber disruption.

29. A process for converting disrupted lignocellulosic plant biomass to sugars comprising xylose and glucose, the process comprising:

(a) providing a plant biomass comprising;

(i) cell walls comprising xylans, glucans and pectins; and

(ii) glucans inside the cell walls; and

(b) adjusting a ratio of enzymatic activity of a glucanase to a cell-wall degrading lyase enzyme so that at least 90% by weight of available cellulose and the xylans in the cell wall of the plant biomass are converted to the sugars.

30. The process of claim 29, wherein the cell-wall degrading lyase enzyme comprises at least one of a hemicellulase and a pectinase.

31. The process of claim 30, wherein the hemicellulase comprises at least one of xyloglucanase, β

-xylosidase, endoxylanase, α

-l-arabinofuranosidase, α

-glucuronidase, and acetyl xylan esterase.

32. The process of claim 30, wherein the pectinase comprises at least one of pectate lyase, polygalacturonase, and pectin esterase.