Process for the simultaneous production of xylitol and ethanol

• US 6,846,657 B2
• Filed: 09/12/1997
• Issued: 01/25/2005
• Est. Priority Date: 01/15/1990
• Status: Expired due to Fees

• Current Assignee: Danisco Sweetners Finland Oy
• Original Assignee: Xyrofin Oy
• Inventors: Viljava, Tapio, Hyöky, Göran, Sarkki, Marja Leena, Heikkilä, Heikki, Rahkila, Leena
• Primary Examiner(s): Naff, David M.
• Application Number:
  US08/928,893
• Publication Number:
  US 20030235881A1
• Time in Patent Office: 2,692 Days
• Field of Search: 435/155, 435/161, 435/105, 435/255.2, 435/255.21, 435/158, 435/163, 435/165, 435/255.4, 435/255.5, 435/255.7, 435/924, 435/938, 435/164
• US Class Current: 435/158
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: C12P 7/18 polyhydric
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y10S 435/924 Candida tropicalis
• CPC Class Codes: Y10S 435/938 Pichia

Abstract

The invention relates to a process for the simultaneous production of xylitol and ethanol from a hydrolyzed lignocellulose-containing material starting. The starting material is fermented with a yeast strain, the ethanol produced is recovered, a chromatographic separation is carried out on the remaining xylitol solution, and pure xylitol is crystallized.

Claims

1. A process for the simultaneous production of xylitol and ethanol from a hydrolyzed lignocellulose-containing material, comprising

providing a starting material of hydrolyzed lignocellulose-containing material comprising xylose and glucose in aqueous solution, wherein xylose content is 50-300 g/l;

fermenting said starting material with a yeast strain which is capable of converting xylose to xylitol and glucose present to ethanol to form a fermented product comprising xylitol, ethanol and yeast, wherein during fermentation the xylose in the starting material is converted to xylitol and the glucose in the starting material is converted to ethanol and 22.3 g/l to 51.2 g/l of ethanol is produced in the fermentation solution;

recovering the resulting ethanol by distillation of the fermentation solution to obtain a distillate with ethanol and a remaining solution; and

recovering xylitol from the remaining solution by chromatographic separation.

2. The process according to claim 1, wherein lignocellulose-containing material hydrolyzed is birch or grain hulls.

3. The process according to claim 1, further comprising crystallizing pure xylitol.

4. The process according to claim 1, wherein yeast cells are removed prior or subsequent to the distillation.

5. The process according to claim 1 wherein the yeast strain is of the genus Candida or Debaryomyces.

6. The process according to claim 1, wherein the yeast is Candida tropicalis.

7. The process according to claim 1, wherein the yeast is Debaryomyces hansenii.

8. The process according to claim 1, wherein the hydrolyzed lignocellulose-containing material is produced by steam explosion and enzymatic hydrolysis of lignocellulose-containing material.

9. The process according to claim 1, wherein the chromatographic separation is carried out with a strong cation-exchanging resin as a stationary phase.

10. The process according to claim 1 wherein the fermentation is carried out at a pH of about 4-7.

11. The process according to claim 6, wherein the yeast is Candida tropicalis ATCC 9968.

12. The process according to claim 10, wherein the fermentation is carried out at a pH of about 5.7 and at a temperature of about 25-35°

C.

13. The process according to claim 1, wherein the hydrolyzed lignocellulose-containing material is produced by a process selected from the group consisting of acid hydrolysis, enzymatic hydrolysis and a combination thereof.

14. The process according to claim 13, wherein hydrolysis is carried out by acid hydrolysis.

15. The process according to claim 1 wherein the lignocellulose-containing material is treated by steam explosion followed by hydrolysis.

16. The process according to claim 1, wherein the fermentation is carried out at a pH of about 4-7 and at a temperature of about 25-35 C with a yeast concentration of 1 to 20 g per liter of solution for 24-144 hours in the presence of nutrients.

17. A process for the simultaneous production of xylitol and ethanol from a hydrolyzed lignocellulose-containing material, wherein lignocellulose-containing material hydrolyzed is selected from the group consisting of softwood, birch, beech, poplar, alder, plants, plant constituents, straw, hulls of wheat, corn, oat, barley, corn cobs, corn stems, nutshells, bagasse, cottonseed bran, wood chips, sawdust, sulphite spent liquor from woodpulp processing, waste from paper processing, and waste from woodpulp processing, comprising:

providing a starting material of hydrolyzed lignocellulose-containing material comprising xylose and glucose in aqueous solution, wherein xylose content is 50-300 g/l;

fermenting said starting material to produce a fermented solution with a yeast capable of converting xylose present in the starting material to xylitol and glucose present in the starting material to ethanol, said yeast selected from the group consisting of a yeast of the genera Candida, Pichia, Pachysolen, and Debaryomyces, said fermenting comprising reducing said xylose to xylitol and said glucose to ethanol, and said fermented solution comprising xylitol, ethanol, and spent yeast;

wherein during fermentation the xylose in the starting material is converted to xylitol glucose in the starting material is converted to ethanol and 22.3 g/l to 51.2 g/l of ethanol is produced into the fermentation solution;

separating a substantial portion of said spent yeast from said fermented solution to produce a substantially clarified solution comprising ethanol and xylitol, said clarified solution comprising substantially less spent yeast by weight on a dry solids (substance) basis than said spent yeast in said fermented solution, and said separating comprising at least one separating method selected from group consisting of filtration, centrifugation and decanting;

recovering ethanol by distillation to obtain a distillate with ethanol and a remaining solution;

recovering xylitol from the remaining solution by chromatographic separation; and

crystallizing said xylitol to produce xylitol crystals.

18. A method according to claim 17 wherein hydrolysis to produce lignocellulose-containing material comprises at least one of the following:

i) prehydrolysis of said lignocellulose-containing material by steam explosion of said lignocellulose-containing material and enzymatic hydrolysis of said lignocellulose-containing material with enzymes having a cellulolytic and xylanolytic activity to hydrolyze said lignocellulose-containing material; and

ii) acid hydrolysis of said lignocellulose-containing material.

19. A method according to claim 17 including removing solids comprising lignin from said fermented solution.

20. A method according to claim 17 wherein said yeast is selected from the group consisting of Candida tropicalis strain having an accession number ATCC 9968, and Debaryomyces hansenii.

21. A method according to claim 17 wherein fermenting occurs at a temperature ranging from about 10 to about 45 degrees C at a pH ranging from 4 to 7 with a yeast concentration of about 1 to about 20 g of dry yeast per liter of solution having a xylose content of about 50 to about 300 g/l for about 24 to about 72 hours in the presence of nutrients.

22. A method according to claim 17 wherein said crystallizing is selected from the group consisting of cooling crystallizing and evaporation crystallizing.

23. A method according to claim 17 wherein said xylitol crystals are separated by centrifugation and washed with water to produce substantially pure crystalline xylitol.

24. A method according to claim 17, wherein:

said starting material of hydrolyzed lignocellulose-containing material comprising xylose and glucose further comprises arabinose.