WO2005094605A1

WO2005094605A1 - Protein purification

Info

Publication number: WO2005094605A1
Application number: PCT/US2005/010527
Authority: WO
Inventors: Aharon Eyal; Asher Vitner
Original assignee: Cargill, Incorporated
Priority date: 2004-03-29
Filing date: 2005-03-29
Publication date: 2005-10-13

Abstract

A method for the production of at least two purified protein products is disclosed. The method includes providing a plant material comprising at least one protein, at least one sugar and at least one solvent, wherein the protein has a purity P1, and wherein the conditions are adjusted so as to form at least one protein-containing solid having a protein purity is P2 and at least one protein-containing solution having a protein purity is P3, so that P2 > P1 > P3. The method also includes separating at least a fraction of the protein-containing solution from the protein-containing solid to form a separated protein-containing solution and a separated protein-containing solid. The method also includes separating protein from the separated protein-containing solution to form a protein-enriched stream having a protein purity is P4 and a protein-depleted stream having a protein purity is P5, wherein P4 > P3 > P5.

Description

PROTEIN PURIFICATION

CROSS-REFERENCE TO RELATED APPLICATIONS The following patent applications are cross-referenced and are hereby incorporated by reference in their entirety: U.S. Patent Application No. 60/557,204 entitled PROTEIN PURIFICATION SYTEM filed March 29, 2004 as attorney docket no. CGL04/0093USP1 ; PCT Patent Application

No. entitled REDUCED PHYTATE FOOD filed March 29, 2005 as attorney docket no. CGL04/0091WO1 ; PCT Patent Application

No. entitled REDUCED PHYTATE FOOD filed March 29, 2005 as attorney docket no. CGL04/0092WO1 ; PCT Patent Application

No. entitled ISOFLAVONE DISTRIBUTION SYSTEM filed

March 29, 2005 as attorney docket no. CGL04/0049WO1 ; PCT Patent Application

No. entitled ISOFLAVONE DISTRIBUTION SYTEM filed

March 29, 2005 as attorney docket no. CGL04/0049WO2; PCT Patent Application No. PCT/US05/004160 entitled PHENOLIC COMPOUND PURIFICATION filed February 9, 2005 as attorney docket no. CGL04/0008WO1 ; PCT Patent Application No. PCT/US05/04153 entitled PHENOLIC COMPOUND PURIFICATION filed February 9, 2005 as attorney docket no. CGL04/0009WO1 ; PCT Patent Application No. PCT/US05/04166 entitled CYCLITOL SEPARATION METHOD filed February 9, 2005 as attorney docket no. CGL03/0489WO1 ; U.S. Patent Application No. 60/630,137 entitled MONOSACCHARIDE PRODUCTION SYSTEM filed November 22, 2004 as attorney docket no. CGL04/0135USP1.

FIELD OF THE INVENTION The present invention generally relates to a protein purification system and method. The present invention more particularly relates to a method for the production of at least two purified protein products. BACKGROUND OF THE INVENTION Various plants are sources of proteins, particularly soybeans. Typically, soybeans are dehulled, flaked, extracted to separate oil, and desolventized to form defatted flakes containing about 45 percent protein (here and in the following the term "percent" means weight percent). After roasting for deactivation of anti-nutritional factors (ANF), those flakes are incorporated as a protein source in animal feed (e.g. soybean meal also typically referred to as "SBM"). A fraction of the defatted soybeans may be further purified to higher protein concentrations for applications such as food and fish feed in aquaculture. One criterion for protein purity is protein concentration in the product, which may be useful in some applications, e.g. food/feed for infants, young animals, fish, etc. Another criterion is the content of components that interfere with optimal food/feed utilization of the protein. Those are generally referred to as anti-nutritional factors (ANF). Oligosaccharides present in defatted soybean are considered ANF.

There are two known industrial approaches to purifications of proteins. According to one such known approach, sugars (mainly mono-, di-, tri- and tetra- saccharides) and other water-soluble components are washed out of SBM at conditions that minimize protein dissolution. Typically, those conditions are either conducting the washing at a pH of about the isoelectric point or washing with an aqueous ethanol solution of 60-80 percent ethanol. As used in this disclosure, the resulting product of such known process is referred to as "protein concentrate." However, such known protein concentrate has several disadvantages including relatively low protein concentration and presence of undesired components, such as polysaccharides and phytate.

The other known industrial method of protein purification involves the following steps: (i) extraction (dissolution) of the protein and of other soluble components (e.g. from defatted and desolventized soybean flakes) into a slightly alkaline aqueous solution; (ii) separation of the extract from the insolubles (e.g. fibers and other non-protein insoluble components); and (iii) separation of the protein in the extract from other soluble components. Such separation typically uses precipitation at about the isoelectric point or ultrafiltration. As used in this disclosure, the resulting product is referred to as "protein isolate." While such known protein isolate is of high purity and high concentration, it has a major disadvantage in that its production is relatively costly.

Accordingly, there is a need for protein products of higher quality than conventional protein concentrate. There is also a need for protein products that are relatively inexpensive to produce. There is also a need for a process for minimizing protein losses and enabling converting practically all the protein content of a relatively low-grade source into relatively high-grade products. There is also a need for a process for minimizing reagents consumption and related waste-treatment cost. There is also a need for an integrated production system that can produce protein products of various qualities (e.g. of desired concentrations or purities) and of relatively high flexibility to adjust to changing market needs. There is also a need for a process for generating a variety of purified protein products of enhanced purity and providing tools for adjusting the ratio between the various products. Accordingly, it would be advantageous to provide a protein purification system and method filling any one or more of these needs or having other advantageous features. SUMMARY OF THE INVENTION The present invention provides a method for the production of at least two purified protein products. The method includes providing a plant material comprising at least one protein, at least one sugar and at least one solvent, wherein the protein has a purity P1 , and wherein the conditions are adjusted so as to form at least one protein-containing solid having a protein purity is P2 and at least one protein-containing solution having a protein purity is P3, so that P2 > P1 > P3. The method also includes separating at least a fraction of the protein-containing solution from the protein-containing solid to form a separated protein-containing solution and a separated protein-containing solid. The method also includes separating protein from the separated protein-containing solution to form a protein-enriched stream having a protein purity is P4 and a protein- depleted stream having a protein purity is P5, wherein P4 > P3 > P5.

The present invention also provides a method of producing at least two purified protein products. The method includes providing a de-hulled and defatted soy material containing at least one sugar and at least one protein. The method also includes washing from the soy material at least about 50 percent of the sugar with at least one of water and an aqueous solution at conditions wherein between about 2 percent and about 98 percent of the protein co-dissolve with the sugar to form a protein-containing solid and a protein-containing solution. The method also includes separating at least a fraction of the protein-containing solution from the protein-containing solid to form a separated protein-containing solution and a separated protein-containing solid. The method also includes providing a second protein solution. The method also includes combining the second protein solution with the separated protein-containing solution. The method also includes separating protein from the combined solution to form a protein-enriched stream and a protein-depleted stream.

The present invention also provides a method for the production of two purified protein products. The method includes washing defatted soybeans with at least one of water and an aqueous solution. The method also includes separating a protein from a solution containing it by means of ultrafiltration.

The present invention also provides a method for the production of two purified protein products. The method includes washing defatted soybeans with at least one of water and an aqueous solution. The method also includes protein precipitation from a solution containing it by pH adjustment to about pl-3 < pH < about pl+3.

The present invention also provides a method for the production of two purified protein products. The method includes protein extraction from a defatted soybean. The method also includes protein precipitation from a solution containing it by pH adjustment to about pl-3 < pH < about pl+3. The method also includes separating a protein from a solution containing it by means of ultrafiltration.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a flow diagram of a protein purification system and method according to an exemplary embodiment of the present invention.

FIGURE 2 is a flow diagram of the protein purification system and method of FIGURE 1 according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED AND OTHER EXEMPLARY EMBODIMENTS Referring to FIGURE 1 , a protein purification system and method is shown according to an exemplary embodiment. The system and method is useful for purifying protein from a plant material. A plant material system containing the plant material is provided. The plant material system includes a protein, a sugar, and a solvent according to an exemplary embodiment. The protein purity in the plant material system is P1. The term "purity," as used in this disclosure means and includes protein concentration by weight on a solvent-free basis. The term purity as used in this disclosure may also mean and include the ratio of the concentrations between the protein and the sugar in the plant material system. The term "purity in the system" in this disclosure means purity in the total system, including solids and solutions.

According to an exemplary embodiment, the plant is an oilseed, most preferably a soybean. According to an exemplary embodiment, the plant material is a defatted oilseed preparation, for example soybean meal (SBM), defatted soybean flour, defatted soybean flakes, flash-desolventized defatted soy flakes, soy protein extracts, soy molasses, soy whey, soy solubles, etc. According to a preferred embodiment, the protein of the plant material system is a soy protein. The protein purification system and method may be suitable for treating a mixture of plant materials, including ones from various plants. The sugar is water soluble according to a preferred embodiment, and may result from the same plant as the at least one protein, e.g. the sugars in soybean. According to any preferred or alternative embodiments, the solvents of the system are water and aqueous solutions. According to a preferred embodiment, the aqueous solutions contain less than about 70 percent organic solvent, suitably less than about 50 percent, 5 more suitably less than about 30 percent. According to a particularly preferred embodiment, the aqueous solutions contain substantially no organic solvent.

According to a preferred embodiment, the conditions in the system are adjusted to form at least one protein-containing solid, wherein the protein purity is P2 and at least one protein-containing solution, wherein the protein purityo is P3, so that P2 > P1 > P3. According to a preferred or alternative embodiments, the adjustment may involve one or more means from a group comprising adjusting the solvent concentration, adjusting the solvent/protein ratio, adjusting the solvent composition, adjusting the pH, adjusting the temperature, etc.

FIGURE 1 shows a system (20) with conditions adjusted to form ats least one protein-containing solid and at least one protein-containing solution, according to an exemplary embodiment. Referring to FIGURE 1 , the system in (20) is formed by contacting/washing a protein material (12) such as soybean meal (e.g. defatted, desolventized and toasted flakes) with a solvent (14), such as water or an aqueous solution. Various known means of contacting/washing areo suitable. According to a preferred embodiment, the contacting/washing is a multiple-step, counter-current operation. The number of wash stages, the solvent composition, the phase ratio, the solution temperature and the contact time in each step may be optimized according to products requirements and to economic consideration according to any preferred or alternative embodiments. The5 contacting/washing results, according to an embodiment of the method, in a protein-containing solid (washed solids) and a protein-containing solution (wash solution), which are separated, according to a preferred embodiments. Separation uses methods such as decantation, centrifugation, gravimetric separation, filtration, etc. and various combinations of those according to any preferred oro alternative embodiments. The washed protein-containing solids, optionally after an additional treatment (e.g. a second wash and drying) or more, form a first purified protein (Purified Protein I, stream (22) in FIGURE 1) with a protein purity P2 greater than that in the plant material system (P1). For example, the plant material may be SBM so that P1 is about 45 percent and the concentration of protein in the first purified protein is greater than about 70 percent.

Many of the suitable plant materials, e.g. SBM, contain protein, sugars, and water-soluble components. Contacting, as in step 20 of FIGURE 1 , is directed to dissolving a maximal fraction of the sugars and other water-soluble components in the solvent (also referred to in this disclosure as "washing") according to a preferred embodiment. According to a preferred embodiment, the conditions during washing are such that a fraction of the protein contained initially in the plant material is dissolved in the solvent to form the protein-containing solution, (24) in FIGURE 1. The term "washing" as used in this disclosure means and includes contacting with a solvent. According to a preferred embodiment, washing is conducted at conditions wherein part of the protein is dissolved along with a maximal fraction of sugars and other water-soluble compounds. The term "protein dissolution" (as in the washing step) is also referred to in this disclosure as protein extraction. Some of the other alternative embodiments described later in this disclosure involve a step wherein maximal protein dissolution/extraction may be aimed in order to separate the protein from insolubles. The extracted proteins end up in the solvent (e.g. an aqueous solution), which is also referred to as extract in this disclosure. Sugars and water-soluble components may be found in the extract stream (24). According to alternative embodiments, the protein-containing solids

(washed solids) may include between about 1 and about 99 percent of the protein contained initially in the plant material, preferably more than about 50 percent. The protein-containing solution (wash solution, extract) may also contain between about 1 and about 99 percent of the protein contained initially in the plant material, preferably at least about 3 percent, more preferably at least about 5 percent. According to a preferred embodiment, the solution contains more than about 7 percent of the protein contained initially in the plant material.

Operating according to preferred embodiments of the method results in better removal of soluble (and somewhat less soluble) non-protein components, compared with removal in conventional processes for producing protein concentrate. As a result, the protein concentration and purity of the first purified protein are greater than those of conventional protein concentrate. Furthermore, the ratio between protein and sugars of the first purified protein may be greater than that of conventional protein concentrate. According to a preferred embodiment, most of the soluble impurities of the plant material are present in the wash solution (protein-containing solution) together with the dissolved protein. According to a preferred embodiment, P2 is at least about 2 times greater than P3, preferably about 5 times greater more preferably about 10 times greater. The protein in the low-purity protein-containing (e.g. wash) solution is not necessarily lost. On the contrary, it may be separated as a protein-enriched stream with purity P4, which can result in a second purified protein of high quality ((32) in FIGURE 1). Also formed may be a protein-depleted solution with minimal protein content and protein purity P5 (34). According to a preferred embodiment, the protein-depleted solution contains less than about 5 percent of the protein in the initial plant material, preferably less than about 3 percent, and most preferably less than about 1 percent. The purity of the protein-enriched stream (P4) may be greater than that in the protein-containing solution from the previous step, i.e. P4 > P3 and greater than P5. According to an embodiment, it may be also greater than P1 and also greater than P2. According to a preferred embodiment, P4 is at least about 2 times greater than P5, preferably about 5 times, more preferably about 10 times, most preferably about 30 times.

Referring back to FIGURE 1 , the protein containing solution (24) separated from the protein-containing solid in step 20 is treated in step 30 to separate the proteins contained in it. A protein-enriched stream (32) and a protein-depleted solution (34) are formed. The protein-enriched stream as such, or after some treatment, (e.g. wash, diafiltration, drying) forms a second purified protein product (Purified Protein II). The protein separation may use, e.g., membrane filtration, precipitation at a pH of about the isoelectric point of the protein, size exclusion and a combination thereof according to any preferred or alternative embodiments.

According to an alternative embodiment, the protein containing solution (solution 24 in FIGURE 1) may be treated prior to the protein separation by a means such as ion-exchange, adsorption, solvent extraction, crystallization, active carbon treatment, fermentation, various combinations thereof, etc. (The purpose of such treatment can be removal of impurities, recovery of valuable components or both.) Commercially valuable components can also be recovered from the protein-depleted stream (34) formed in the protein-separation operation. Commercially valuable components may include, for example, isoflavones, cyclitols, phyate, saponins, sugars (e.g. galactose), fermentation products, etc.

According to a preferred embodiment, the purity of the protein- containing solids (P1), or of the first purified protein product obtained from it (22), is greater than about 60 percent, preferably greater than about 70 percent, more preferably greater than about 75 percent, and most preferably greater than about 85 percent.

According to a preferred embodiment, the purity of the protein- enriched stream (P4) or of the purified second protein obtained from it (32) is greater than about 80 percent, preferably greater than about 85 percent, more preferably greater than about 90 percent, and more preferably greater than about 92 percent.

According to an alternative embodiment, another protein solution may be provided and combined with the protein material to form the adjusted conditions in (20). Thus, a protein solution from another source may be used (as the solvent in (14) or in addition to it) to wash soluble impurities from the plant material. According to a preferred embodiment, protein contained in the provided protein solution is also recovered in another protein stream or in one of the protein products of the process. According to a preferred embodiment, the protein separation uses a method similar to that for the formation of the protein-enriched stream. According to alternative embodiments, those two operations are 5 conducted sequentially, substantially simultaneously, or in the same operation.

According to another alternative embodiment, the provided protein solution may be combined with at least a fraction of the protein-containing solution (24) to form a combined stream with protein purity P7. Protein may be separated from that combined stream to form a protein-enriched stream with protein purityo P8 and a protein-depleted stream with protein purity P9 so that P8 > P7 > P9.

According to another alternative embodiment, de-hulled and defatted soy material containing at least one sugar and at least one protein and having protein purity P1 are provided. Most of the sugar in the soy material is washed with water or with an aqueous solution at conditions wherein between about 25 percent and about 98 percent (between about 5 percent and about 95 percent) of the protein co-dissolve with the sugar to form a protein-containing solid and a protein-containing solution. Separation is applied to form a separated protein- containing solution having protein purity P3 and a separated protein-containing solid having protein purity P2, so that P2 > P1 > P3. At least a part of the proteino containing solution, or a solution derived from it, is combined with another protein solution having protein purity P7. Protein is separated from the combined solution to form a protein-enriched stream having protein purity P8 and a protein-depleted stream having protein purity P9, so that P8 > P7 > P9.

Referring to another alternative embodiment as shown in FIGURE 2,5 soybeans are dehulled and defatted to form a defatted protein material (42). A fraction of it is preferably desolventized and toasted (shown as Portion A (46)) and another fraction is desolventized with no toasting, preferably flash desolventized (shown as Portion B (48)). Most of the sugars in Portion A (46) are washed out in step 50 with water or with an aqueous solution (44) at conditions wherein betweeno about 2 percent and about 50 percent (e.g. between about 5 percent and about 40 percent) of the proteins co-dissolve. A protein-containing solid is formed and separated and can be used, optionally after some additional treatments, as a first purified protein product (52). Also formed is a solution containing the extracted protein and sugars (54). Referring further to FIGURE 2, Portion B (48) is extracted in step 60 with water or with an aqueous solution (56), preferably at a slightly alkaline pH (pH of about 8) at conditions wherein at least about 70 percent (e.g. about 80 percent, 90 percent, 95 percent, etc.) of the protein is extracted. The extract is separated from the insolubles to form a separated extract (64) and separated insolubles (62). According to an alternative embodiment, at least part of the extract may be used to form the solvent for the extraction of Portion A (step 50).

According to one embodiment, protein may be separated from the extract (64) to form a protein-enriched stream that can be used as such or after further treatment as a second purified protein product. According to another embodiment (as shown in FIGURE 2), at least a fraction of the protein-containing solution or a solution derived from it (54) is combined with at least a fraction of the extract, or a solution derived from it (64) to form a combined solution (65). Protein may be separated from at least a fraction of the combined solution in step 70 to form a protein depleted solution (72) and a protein-enriched stream, which can be used as such or after additional treatments, as purified protein product (74). According to a preferred embodiment, protein separation is conducted by ultrafiltration, isoelectric precipitation or a combination of those.

According to alternative embodiments, the plant material may be treated prior to the formation of the system, prior to adjustment of the conditions, or substantially simultaneously with it.

According to an exemplary embodiment, the system may be formed by contacting/washing a plant material, such as SBM, with water or with aqueous solution at conditions where protein-containing solid and protein-containing solution exist. According to an alternative embodiment, the protein and the sugar are extracted from the plant material to form an extract and a protein-depleted matter and the extract is separated from the matter. The conditions in the extract may be changed to facilitate precipitation of a fraction of the protein. Changing the conditions can be done by known methods, such as changing the pH towards pi, increasing the concentration e.g. by water removal, solvent-aided precipitation, lowering the temperature, various combinations of those, etc. according to any preferred or alternative embodiments. The solution and the precipitated protein form the protein-containing solid and protein-containing solution.

According to an exemplary embodiment, SBM may be extracted with a slightly alkaline aqueous solution. Most of the extractable protein may be extracted to form an extract, which also contains water-soluble bean components, mainly sugars. The extract may be separated from the insolubles and its pH may be lowered to facilitate partial precipitation of proteins. The protein-containing solid may be separated from the protein-containing solution and to form, as such, or after further treatment, the first purified protein product. The separated protein- containing solution may be further treated to separate protein contained in it and to form thereby a second purified protein product.

According to another exemplary embodiment, the method involves at least two protein/sugar separations. In one of those, most of the sugars and part of the protein are removed by dissolution from the rest of the protein and from the insolubles in a defatted bean. In the other, dissolved protein is separated from dissolved sugars by means of ultrafiltration. According to a preferred embodiment, the method also involves a step wherein most of the protein and most of the sugars are separated from insolubles in a defatted bean by extraction.

According to another alternative embodiment, the method involves at least two protein/sugar separations. In one of those, most of the sugars and part of the protein are removed by dissolution from the rest of the protein and from the insolubles in a defatted bean. In the other, dissolved protein is separated from dissolved sugars by pH adjustment to about pl-3 < pH < pl+3.

According to still another alternative embodiment, the method involves at least three protein/sugar separations. In one of those, most of the sugars and most of the protein are removed from the insolubles in a defatted bean by extraction. In another step, dissolved protein is separated from dissolved sugars by pH adjustment to about pl-3 < pH < pl+3. In a third separation, dissolved protein is separated from dissolved sugars by means of ultrafiltration. Referring back to FIGURES 1 and 2, various purified protein products (PP) may be produced. Those include: PP1 , the separated protein- containing solids (washed solids), optionally after further treatment (streams 22 and 52 in FIGURES 1 and 2, respectively); PP2, proteins separated from the protein-containing solution (streams 24 and 54 in FIGURES 1 and 2, respectively); PP3 proteins separated from the extract (64); and PP4, proteins separated from the combined stream (65).

The conditions may be adjusted by controlling the pH. According to a preferred embodiment, the first step (e.g. wash solution, steps 20 and 50 in FIGURES 1 and 2, respectively) is conducted at a pH other than pi (which may leads to increased purity of the washed protein (PP1)). According to alternative embodiments, the pH in the wash operation could be higher or lower than about pi. According to a particularly preferred embodiment, pH > pi (e.g. greater than about pH about 4 - 4.5, suitably between about 4 and about 8.) According to a preferred embodiment, the pH is in the range between about pi + 0.1 and about pi + 3.

The conditions may also be adjusted by controlling the temperature in the wash operation, the solvent/plant-material weight ratio there and the concentration of water-soluble organic solvent, if present in the solvent of the wash solution (streams 14 and 44 in FIGURES 1 and 3, respectively). According to a preferred embodiment, conducting the wash according to preferred embodiments may lead to increased purity of the first purified protein product (PP1).

In the embodiment described in FIGURE 2, increasing the ratio between Portion B and Portion A (i.e. between stream 48 and stream 46) increases the proportion of PP3 and PP4 compared with that of PP1 and PP2. The ratio between PP3 and PP4 may be affected by the proportion of the extract (64) combined with the protein-containing solution (54).

While the preferred and other exemplary embodiments described in this disclosure are presently preferred, it may be understood that these embodiments are offered by way of example only. The invention may be not limited to a particular embodiment, but extends to various modifications, combinations, and permutations.

Claims

CLAIMSWhat is claimed is:

1. A method for the production of at least two purified protein products, comprising the steps of: (a) providing a plant material comprising at least one protein, at least one sugar and at least one solvent, wherein the protein has a purity P1 , and wherein the conditions are adjusted so as to form at least one protein-containing solid having a protein purity is P2 and at least one protein- containing solution having a protein purity is P3, so that P2 > P1 > P3; (b) separating at least a fraction of the protein-containing solution from the protein- containing solid to form a separated protein-containing solution and a separated protein-containing solid; (c) separating protein from the separated protein- containing solution to form a protein-enriched stream having a protein purity is P4 and a protein-depleted stream having a protein purity is P5, wherein P4 > P3 > P5.

2. The method of Claim 1 , wherein the plant material comprises an oilseed.

3. The method of Claim 1 , wherein the plant material comprises a defatted oilseed.

4. The method of Claim 1 , wherein the plant material comprises at least one of soybean meal, defatted soybean flour, defatted soybean flakes, flash- desolventized defatted soy flakes, soy protein extracts, soy molasses, soy whey, and soy solubles.

5. The method of Claim 1 , wherein the at least one protein comprises a soy protein.

6. The method of Claim 1 , wherein the solvent comprises at least one of water and aqueous solutions, and wherein the solvent comprises less than about 70 percent organic solvent.

7. The method of Claim 1 , wherein adjusting the conditions in step (a) comprises at least one of adjusting the solvent concentration, adjusting the solvent composition, adjusting the solvent/protein ratio, adjusting the pH, adjusting the temperature and a combination thereof.

8. The method of Claim 1 , wherein the conditions in step (a) are such that the protein-containing solid comprises between about 1 percent and about 99 percent by weight of the protein in the plant material.

9. The method of Claim 1 , wherein the conditions in step (a) are such that the protein-containing solution comprises between about 1 percent and about 99 percent by weight of the protein in the plant material.

10. The method of Claim 1 , wherein the conditions in step (a) are such that the protein-containing solution comprises at least about 3 percent by weight of the protein in the plant material.

11. The method of Claim 1 , wherein the conditions in step (a) are such that the protein-containing solution comprises at least about 50 percent by weight of the at least one sugar in the plant material.

12. The method of Claim 1 , wherein providing the plant material comprises contacting with a solvent a solid plant material comprising at least one protein and at least one sugar.

13. The method of Claim 12, wherein the contacting comprises a multiple-stage contacting.

14. The method of Claim 13, wherein the multiple-stage contacting is conducted in a counter-current mode of operation.

15. The method of Claim 1 , wherein P2 is at least about 2 times greater than P3.

16. The method of Claim 1 , wherein P2 is at least about 60 percent.

17. The method of Claim 1 , wherein the pH of the protein-containing solution is between about pi + 0.1 and about pi + 3, wherein pi is the isoelectric point of the protein.

18. The method of Claim 1 , wherein the separating in step (b) comprises at least one of decantation, centrifugation, gravimetric separation, filtration, and a combination thereof.

19. The method of Claim 1 , wherein the separated protein-containing solid is washed with at least one of water and an aqueous solution to form a separated and washed protein-containing solid having a protein purity P6.

20. The method of Claim 1 , wherein P6 is at least about 60 percent.

21. The method of Claim 1 , wherein the separated protein-containing solution is treated prior to step (c) for the removal of impurities by at least one of ion- exchange, adsorption, solvent extraction, active carbon treatment, fermentation, crystallization and a combination thereof.

22. The method of Claim 1 , wherein the separated protein-containing solution is treated prior to step (c) for the separation of at least one compound of commercial value.

23. The method of Claim 22, wherein the at least one compound of commercial value comprises at least one of isoflavones, saponins, sugars, proteins, fermentation products, cyclitols, phytate, and combinations thereof.

24. The method of Claim 1 , wherein the separating in step (c) comprises at least one of membrane filtration, precipitation at pH of about the isoelectric point of the protein, size exclusion and a combination thereof.

25. The method of Claim 1 , wherein P4 is at least about 2 times greater than P5.

26. The method of Claim 1 , wherein P4 is at least about 80 percent.

27. The method of Claim 1 , wherein the protein-depleted stream is treated for the separation of at least one compound of commercial value.

28. The method of Claim 27, wherein the at least one compound of commercial value comprises at least one of isoflavones, saponins, sugars, proteins, fermentation products, cyclitols, phytate, and combinations thereof.

29. The method of Claim 1 , further comprising the step of: (d) providing a second protein-containing solution.

30. The method of Claim 29, wherein the second protein-containing solution of step (d) is combined with the plant material of step (a).

31. The method of Claim 29, wherein the adjusting of conditions comprises combining with the second protein-containing solution of step (d).

32. The method of Claim 29, further comprising the step of: (e) separating protein from the second protein-containing solution of step (d) to form a second protein-enriched stream and a second protein-depleted stream.

33. The method of Claim 32, wherein the protein separation of step (e) uses substantially the same means of protein separation as step (c).

34. The method of Claim 29, further comprising the step of: (f) combining the second protein-containing solution of step (d) with at least a fraction of the separated protein-containing solution of step (b) to form a combined solution having a protein purity P7.

35. The method of Claim 34, further comprising the step of: (g) separating protein from the combined solution of step (f) to form a third protein-enriched stream having a protein purity P8 and a third protein-depleted stream having a protein purity P9, and wherein P8 > P7 > P9.

36. The method of Claim 35, wherein the separation of protein comprises ultrafiltration.

37. A method of producing at least two purified protein products comprising the steps of: (a) providing a de-hulled and defatted soy material containing at least one sugar and at least one protein; (b) washing from the soy material of step (a) at least about 50 percent of the sugar with at least one of water and an aqueous solution at conditions wherein between about 2 percent and about 98 percent of the protein co-dissolve with the sugar to form a protein-containing solid and a protein-containing solution; (c) separating at least a fraction of the protein- containing solution from the protein-containing solid to form a separated protein- containing solution and a separated protein-containing solid; (d) providing a second protein solution; (e) combining the second protein solution of step (d) with the separated protein-containing solution of step (c); and (f) separating protein from the combined solution of step (e) to form a protein-enriched stream and a protein-depleted stream.

38. The method of Claim 37, further comprising the step of: (g) combining at least a fraction of the separated protein-containing solution of step (c) with at least a fraction of the separated extract of step (e) to form a combined solution, and separating protein from the combined solution by means of an ultrafiltration membrane, isoelectric point precipitation or their combination to form a protein- enriched stream and a protein-depleted stream.

39. A method for the production of two purified protein products, comprising the step of washing defatted soybeans with at least one of water and an aqueous solution and the step of separating a protein from a solution containing it by means of ultrafiltration.

40. The method of Claim 39, further comprising the step of protein extraction from a defatted soybean.

41. A method for the production of two purified protein products, comprising the step of: washing defatted soybeans with at least one of water and an aqueous solution and the step of protein precipitation from a solution containing it by pH adjustment to about pl-3 < pH < about pl+3.

42. A method for the production of two purified protein products, comprising the steps of: protein extraction from a defatted soybean, protein precipitation from a solution containing it by pH adjustment to about pl-3 < pH < about pl+3, and separating a protein from a solution containing it by means of ultrafiltration.