Zein recovery using non-porous membranes

• US 20040230041A1
• Filed: 05/14/2003
• Published: 11/18/2004
• Est. Priority Date: 05/14/2003
• Status: Active Grant

• Current Assignee: Membrane Technology and Research, Inc.
• Original Assignee: Membrane Technology and Research, Inc.
• Inventors: Wijmans, Johannes G., Ng, Alvin, Mairal, Anurag P.
• Granted Patent: US 6,846,909 B2
• Time in Patent Office: Days
• US Class Current: 530/373
• CPC Class Codes: C07K 14/425 Zeins

Abstract

A membrane process for treating zein solutions to increase the zein concentration in the solution. The process uses a non-porous membrane that preferentially permeates the solvent and rejects the zein. Optionally, the process can be operated as a diafiltration process to yield a concentrate of high zein purity.

Claims

1. A process for heating a rein solution comprising zein and a solvent, comprising the steps of:

(a) providing a first composite membrane having a first feed side, a first permeate side, and a first dense, non-porous selective layer that is selective in favor of the solvent over zein;

(b) passing the zein solution across the first feed side;

(c) withdrawing from the first feed side a first residue stream enriched in zein compared to the zein solution;

(d) withdrawing from the first permeate side a first permeate stream depleted in zein compared to the zein solution.

2. The process of claim 1, wherein the first dense, non-porous selective layer is hydrophilic.

3. The process of claim 1, wherein the first dense, non-porous selective layer comprises a polymer including a polyether segment.

4. The process of claim 1, wherein the first dense, non-porous selective layer comprises a polymer including a polyether segment and a hydrophilic segment.

5. The process of claim 1, wherein the first dense, non-porous selective layer comprises a polyamide-polyether block copolymer.

6. The process of claim 1, wherein the first composite membrane comprises a support layer for supporting the first dense, non-porous selective layer and a top layer coated on the first dense, non-porous selective layer.

7. The process of claim 1, wherein the solvent is non-aqueous based.

8. The process of claim 1, wherein the solvent comprises an alcohol.

9. The process of claim 1, wherein the solvent comprises ethanol.

10. The process of claim 1, wherein the solvent comprises an ethanol/water mixture.

11. The process of claim 1, operated under an applied feed pressure of no higher than about 150 psig.

12. The process of claim 1, operated under an applied feed pressure between about 50 psig and 150 psig.

13. The process of claim 1, operated in a feed-and-bleed mode by recirculating a portion of the first residue stream and adding it to the zein solution.

14. The process of claim 1, operated in a diafiltration mode by diluting and further processing at least a portion of the first residue stream.

15. The process of claim 14, wherein a diluent is used for the diluting step, and the diluent has a different composition than the solvent.

16. The process of claim 1, wherein the first composite membrane exhibits a zein rejection, averaged over the duration of the process, of at least about 80%.

17. The process of claim 1, wherein the first composite membrane exhibits a zein rejection, averaged over the duration of the process, of at least about 90%.

18. The process of claim 1, wherein the zein solution further comprises at least one sugar and the first composite membrane exhibits a total sugars rejection, averaged over the duration of the process, of no more than about 40%.

19. The process of claim 1, wherein the first composite membrane exhibits a pressure-normalized permeate flux, averaged over the duration of the process, of at least about 0.05 L/m²·

h·

psi.

20. The process of claim 1, wherein the first residue stream has a residue volume flow and the zein solution has a feed volume flow and the residue volume flow is no more than about 30 vol % of the feed volume flow.

21. The process of claim 1, wherein the first residue stream has a residue volume flow and the zein solution has a feed volume flow and the residue volume flow is no more than about 20 vol % of the feed volume flow.

22. The process of claim 1, wherein the zein solution has a first zein concentration and the first residue stream has a second zein concentration that is between about five and 10 times greater than the first zein concentration.

23. The process of claim 1, wherein the first residue stream has a total dissolved solids content and a zein content, and wherein the zein content is at least about 70% of the total dissolved solids content.

24. The process of claim 1, wherein the first residue stream has a total dissolved solids content and a zein content, and wherein the zein content is at least about 80% of the total dissolved solids content.

25. The process of claim 1, wherein the first composite membrane has a molecular weight cut-off above about 2,000 dalton and below about 12,000 dalton.

26. The process of claim 1, wherein the first composite membrane has a molecular weight cut-off above about 12,000 dalton and below about 22,000 dalton.

27. The process of claim 1, wherein the first residue stream is subjected to farther treatment.

28. The process of claim 27, wherein the further treatment comprises at least one additional membrane treatment using at least one additional composite membrane having a dense, non-porous selective layer.

29. The process of claim 1, further comprising the steps of:

(e) providing a second composite membrane having a second feed side, a second permeate side, and a second dense, non-porous selective layer that is selective in favor of the solvent over zein;

(f) passing at least a portion of the first residue stream across the second feed side;

(g) withdrawing from the second feed side a second residue stream enriched in zein compared to the first residue stream;

(h) withdrawing from the second permeate side a second permeate stream depleted in zein compared to the first residue stream.

30. The process of claim 29, wherein step (b) is operated under a first applied pressure and step (f) is operated under a second applied pressure and wherein the second applied pressure is lower than the first applied pressure.

31. The process of claim 1, wherein the first residue stream is spray dried to produce zein powder.

32. The process of claim 1, wherein the first residue stream is subjected to evaporation followed by spray drying to produce zein powder.

33. The process of claim 1, wherein the first permeate stream is subjected to further treatment.

34. The process of claim 1, further comprising warming the zein solution prior to step (b).

35. The process of claim 1, further comprising warming the zein solution to a temperature up to about 35°

C. prior to step (b).

36. A process for treating a feed solution comprising a solvent and a solute, the solute comprising zein and a sugar, comprising the steps of:

(a) providing a first composite membrane having a first feed side, a first permeate side, and a first dense, non-porous selective layer that is selective in favor of the solvent over zein and that exhibits a zein rejection and a sugar rejection, the sugar rejection being lower than the zein rejection;

(b) passing the feed solution across the first feed side;

(c) withdrawing from the first feed side a first residue stream enriched in zein compared to the feed solution;

(d) withdrawing from the first permeate side a first permeate stream having a permeate dissolved solids content that is enriched in sugar and depleted in zein compared to the solute.

37. The process of claim 36, wherein the first dense, non-porous selective layer comprises a polyamide-polyether block copolymer.

38. The process of claim 36, wherein the solvent comprises ethanol.

39. The process of claim 36, operated in a diafiltration mode by diluting and further processing at least a portion of the first residue stream.

40. The process of claim 36, wherein the zein rejection, averaged over the duration of the process, is at least about 90%.

41. The process of claim 36, wherein the sugar rejection, averaged over the duration of the process, is no more than about 40%.

42. The process of claim 36, wherein the first composite membrane exhibits a pressure-normalized permeate flux, averaged over the duration of the process, of at least about 0.05 L/m²·

h·

psi.

43. The process of claim 36, wherein the first residue stream has a residue volume flow and the feed solution has a feed volume flow and the residue volume flow is no more than about 30 vol % of the feed volume flow.

44. The process of claim 36, wherein the first composite membrane has a molecular weight cut-off above about 2,000 dalton and below about 12,000 dalton.

45. The process of claim 36, wherein the first residue stream is subjected to at least one additional membrane treatment using at least one additional composite membrane having a dense, non-porous selective layer.

46. The process of claim 36, wherein at least a portion of the first residue stream is spray dried to produce zein powder.

47. A process for treating a zein solution comprising zein and a non-aqueous based solvent, comprising the steps of:

(a) providing a first composite membrane having a first feed side, a first permeate side, and a first dense, non-porous selective layer that is selective in favor of the solvent over zein;

(b) passing the zein solution across the first feed side;

(c) withdrawing from the first feed side a first residue stream enriched in zein compared to the zein solution;

(d) withdrawing from the first permeate side a first permeate stream depleted in zein compared to the zein solution.

48. The process of claim 47, wherein tie first dense, non-porous selective layer comprises a polyamide-polyether block copolymer.

49. The process of claim 47, wherein the solvent comprises ethanol.

50. The process of claim 47, operated in a diafiltration mode by diluting and further processing at least a portion of the first residue stream.

51. The process of claim 47, wherein the first composite membrane exhibits a zein rejection, averaged over the duration of the process, of at least about 90%.

52. The process of claim 47, wherein the zein solution further comprises at least one sugar and the first composite membrane exhibits a total sugars reaction, averaged over the duration of the process, of no more than about 40%.

53. The process of claim 47, wherein the first composite membrane exhibits a pressure-normalized permeate flux, averaged over the duration of the process, of at least about 0.05 L/m²·

h·

psi.

54. The process of claim 47, wherein the first residue stream has a residue volume flow and the zein solution has a feed volume flow and the residue volume flow is no more than about 30 vol % of the feed volume flow.

55. The process of claim 47, wherein the first composite membrane has a molecular weight cut-off above about 2,000 dalton and below about 12,000 dalton.

56. The process of claim 47, wherein the first residue stream is subjected to at least one additional membrane treatment using at least one additional composite membrane having a dense, non-porous selective layer.

57. The process of claim 47, wherein at least a portion of the first residue stream is spray dried to produce zein powder.