Method and system for increasing the yield and / or purity of protein from a grain protein recovery system

Abstract

A wet mill method and system of starch production for increasing the yield and / or purity of protein (gluten) in facilities that can produce biofuels and / or biochemicals, such as alcohol (e.g., from corn). In one embodiment, the method includes membrane filtration of a liquid portion separated from a thickened gluten slurry into the liquid portion and a protein (gluten) wet cake such as by a rotary drum vacuum filter. The liquid portion may be optionally cooled in a heat exchanger to a temperature suitable for a selected / desired membrane filter. The cooled liquid portion / stream can be sent to the membrane filter. Solids, high molecular weight dissolved proteins, and oils are separated by the membrane filter and concentrated in a retentate stream. Concentrated proteins from the retentate are returned to the prior separation step / equipment (e.g., a centrifuge) that produced the initial gluten slurry in the method and separated thereby increasing protein yields and / or purity in a gluten meal co-product.

Description

METHOD AND SYSTEM FOR INCREASING THE YIELD AND / OR PURITY OF PROTEIN FROM A GRAIN PROTEIN RECOVERY SYSTEMTechnical Field

[0001] The present invention relates generally to wet mill methods and systems of starch production and, more specifically, to increasing the yield and / or purity of protein (gluten) from methods and systems that separate protein from a starch / protein (gluten) slurry in a wet mill plant that can derive a biofuel and / or biochemical, such as alcohol (e.g., ethanol), from grain. Background

[0002] The conventional processes for producing various types of biochemicals, such as biofuels (e.g., alcohol) and other chemicals, from grains generally follow similar procedures. Wet mill processing plants convert, for example, corn grain, into several different co-products, such as germ (for oil extraction), gluten feed (high fiber animal feed), gluten meal (high protein animal feed) and starch-based products such as dextrose, high fructose corn syrup, or food and industrial starch.

[0003] With respect to the wet mill process, Fig. 1 is a flow diagram of an example of a typical wet mill alcohol (e.g., ethanol) production process 10. The wet milling process 10 begins with a steeping step 12 in which kernels of grain (e.g., com) can be soaked for 24 to 48 hours in an acid solution to soften the outer husk of the kernel for grinding, leach soluble components into the steep water, and loosen the protein matrix with the starchy endosperm. Com kernels contain mainly starch, fiber, protein, and oil. After steeping is completed, the softened kernels are mn through a milling operation or a first grinding step 14 in which the com is ground in a manner that tears open the outer layer of the softened kernel and releases the germ so as to make a heavy density slurry of the ground components, primarily a starch slurry. The first grinding step 14 is followed by a germ separation step 16 whereat the germ fraction of the kernel, which contains desirable vegetable oil, is separated from the rest of the slurry by flotation and use of one or more hydrocyclones. The separated germ stream, which contains some portion of the starch, protein, and fiber, generally goes to germ washing to remove starch and protein, and then to a dryer to produce about 2.7 to 3.2 pounds (dry basis) of germ per bushel of com (Ib / bu). The dry germ has about 50% oil content on a dry basis.

[0004] The remaining slurry / kernel constituents, which are made up of fiber, gluten (protein), and starch, can be further reduced in size by being subjected to a second grinding step 20 in which there can be total disruption of endosperm and release of endosperm components, namely gluten and starch, from the fiber and outer kernel hull or pericarp. This is followed by a coarse fiber separation step 22 in which the slurry is passed through a series or set of screens, such as pressure screens, in order to separate the fiber from starch and gluten and to wash the fiber clean of gluten and starch. The gluten particles are generally smaller than the fiber particles and pass through the pressure screen. The larger particle size of the fiber will not pass through the screens. The fiber is removed and can be sold as animal feed either wet, or after being dried.

[0005] The remaining slurry is now generally devoid of germ and fiber and includes mostly starch and gluten particles in water and can be subjected to a mill slurry thickener step 23. At mill slurry thickener step 23, a portion of the water can be removed from the slurry stream by utilizing a mill slurry thickener, as is known in the art and which can include a decanter centrifuge, for example. The recovered process liquid can be returned as process water and used at a step earlier in the method 10, such as at steeping step 12. The remaining thickened slurry now can be separated into separate starch and gluten streams at a gluten separation step 24, such as by way of a centrifuge(s), such as a nozzle bowl type centrifuge, or hydrocyclone(s). The starch is denser than the gluten and can be carried out in the underflow of the centrifuge, and the lighter protein (gluten) stream can exit with the overflow.

[0006] The gluten stream next can be subjected to a gluten thickener step 25 to remove a portion of the water by means and methods known in the art, which can include a decanter centrifuge, for example, thereby providing a thicker / thickened gluten slurry. The recovered process liquid can be returned as process water and used at a step earlier in the method 10, such as at steeping step 12. The now thickened gluten slurry optionally can be separated at gluten meal separation step 26 using a rotary drum vacuum filter (RDVF), for example. The water in the slurry passes through the cloth on the drum of the filter and the gluten is collected as a wet cake. The recovered process liquid from the gluten meal separation step 26 can be returned as process water and used at a step earlier in the method 10, such as at steeping step 12. The resulting protein (gluten) rich wet cake, which typically contains mostly starch that may be free and / or bound with the protein matrix, can be dried and sold as an animal feed (gluten meal).Here, while variations in protein (gluten) concentrations may be experienced in the wet mill process of Fig. 1, the protein (gluten) typically is present in the gluten meal in an amount from about 58 wt% to 65 wt% on a dry basis.

[0007] The starch stream from the gluten separation step 24 can undergo a jet cooking step 27 to start the process of converting the starch to sugar. Jet cooking refers to a cooking process performed at elevated temperatures and pressures, although the specific temperatures and pressures can vary widely. Typically, jet cooking occurs at a temperature of about 93 to 110°C (about 200 to 230°F) and a pressure of about 30 to 50 psi. This is followed by liquefaction 28, saccharification 30, fermentation 32, yeast recycling 34, and distillation / dehydration 36 for a typical wet mill biochemical system. Liquefaction occurs as the mixture or "mash" is held at 90 to 95°C in order for alpha-amylase to hydrolyze the gelatinized starch into maltodextrins and oligosaccharides (chains of glucose sugar molecules) to produce a liquefied mash or slurry. In the saccharification step 30, the liquefied mash is cooled to about 50°C and a commercial enzyme known as gluco-amylase is added. The gluco-amylase hydrolyzes the maltodextrins and short-chained oligosaccharides into single glucose sugar molecules to produce a liquefied mash. In the fermentation step 32, a common strain of yeast (Saccharomyces cerevisae) is added to metabolize the glucose sugars into ethanol and CO2.

[0008] Upon completion, the fermentation mash ("beer") will contain about 15% to 18% ethanol (volume / volume basis), plus soluble and insoluble solids from all the remaining grain components. The solids and some liquid remaining after fermentation go to an evaporation stage where yeast can be recovered as a byproduct. Yeast can optionally be recycled in a yeast recycling step 34. In some instances, the CO2 is recovered and sold as a commodity product. Subsequent to the fermentation step 32 is the distillation and dehydration step 36 in which the beer is pumped into distillation columns where it is boiled to vaporize the ethanol. The ethanol vapor is separated from the water / slurry solution in the distillation columns and alcohol vapor (in this instance, ethanol) exits the top of the distillation columns at about 95% purity (190 proof). The 190 proof ethanol then goes through a molecular sieve dehydration column, which removes the remaining residual water from the ethanol, to yield a final product of essentially 100% ethanol (199.5 proof). This anhydrous ethanol is now ready to be used for motor fuel purposes.Further processing within the distillation system can yield food grade or industrial grade alcohol.The starch stream alternatively may be converted to modified starch products or sweeteners.

[0009] No centrifugation step is necessary at the end of the wet mill ethanol production process 10 as the germ, fiber and gluten have already been removed in the previous separation steps 16, 22, 24. The "stillage" produced after distillation and dehydration 36 in the wet mill process 10 is often referred to as "whole stillage" although it also is technically not the same type of whole stillage produced with a traditional dry grind process since no insoluble solids are present. Other wet mill producers may refer to this type of stillage as "thin" stillage or simply “stillage”.

[0010] While the wet grind process 10 can produce a high-quality starch product such as for conversion to alcohol, as well as separate streams of germ, fiber, and protein (gluten), which can be sold as co-products to generate additional revenue streams, the overall yields for various coproducts can be less than desirable. It, thus, would be beneficial to provide an improved method and system to further enhance a gluten meal grain co-product, such as by increasing the protein content (gluten) and / or the overall amount of protein (gluten) so that the gluten meal can be sold at a higher cost and / or greater revenue can be realized simply through the sale of more product.Summary of the Invention

[0011] The present invention is directed to a method and system for increasing the yield and / or purity of protein from a system that produces protein from the wet milling of grains including, for example, corn and wheat.

[0012] In one embodiment, a method for increasing the yield and / or purity of protein (gluten) in a gluten meal co-product from a gluten slurry stream in a wet grain milling plant, which derives a starch stream to produce a biochemical, such as alcohol (e.g., ethanol) and / or other starch based products, from grain, includes membrane filtration of a liquid portion that has been separated from a thickened gluten slurry into the liquid portion and a protein (gluten) wet cake portion such as by a rotary drum vacuum filter (RDVF). The liquid portion may be optionally cooled in a heat exchanger to a temperature suitable for the selected / desired membrane filter. The optionally cooled liquid portion / stream is pumped into / sent to a membrane filter. Solids,high molecular weight dissolved proteins, and oils are rejected / separated by the membrane filter and concentrated in a retentate stream. Low molecular weight dissolved solids (and water) will pass through the membrane as the permeate. The concentrated proteins from the retentate will be returned to prior separation equipment (e.g., a centrifuge) that produced the initial gluten slurry in the method, such as previously described above in Fig. 1, and will be captured / separated by said equipment increasing protein yields and / or purity in the gluten meal co-product.

[0013] In another embodiment, a method for increasing the yield and / or purity of protein in a gluten meal coproduct produced in a wet mill plant that can derive a biofuel and / or biochemical from grain is provided that includes steeping grain in an acid solution for a desired period of time to soften the grain, milling the softened grain to provide a slurry, including germ, initial protein, fiber, and starch, and removing the germ and fiber from the slurry. Thereafter, at least a portion of a retentate, which includes residual protein, that is received from a later step in the method is added to the slurry, and then separating the slurry into a starch stream and a gluten stream, including the combined initial and residual protein, wherein the addition of the retentate increases the overall concentration of protein in the slurry. Thereafter, the first process liquid is filtered to provide the retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received from the later step in the method, and wherein the first dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt% protein on a dry basis.

[0014] In another embodiment, a method for increasing the yield and / or purity of protein in a gluten meal coproduct produced in a wet mill plant that can derive a biofuel and / or biochemical from grain is provide that includes steeping grain in an acid solution for a desired period of time to soften the grain, milling the softened grain to provide a slurry, including germ, initial protein, fiber, and starch, and removing the germ and fiber from the slurry. Thereafter, at least a portion of a retentate, which includes residual protein, that is received from a later step in the method is added to the slurry, and then separating the slurry into a starch stream and a gluten stream, including the combined initial and residual protein, wherein the addition of the retentate increases the overall concentration of protein in the slurry. Thereafter, the gluten stream is dewatered to provide a first process liquid and a first dewatered gluten stream, including the combined protein, and the first dewatered gluten stream is dewatered to provide a second processliquid and a second dewatered gluten stream, including the combined protein. Then, the second process liquid is cooled, via a heat exchanger, followed by filtering the cooled second process liquid to provide the retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received from the later step in the method, and wherein the second dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt% protein on a dry basis.

[0015] In yet another embodiment, a system for increasing the yield and / or purity of protein in a gluten meal coproduct produced in a wet mill plant that can derive a biofuel and / or biochemical from grain is provided that includes a milling device that receives and grinds softened grain from a steeping process to provide a slurry, including germ, initial protein, fiber, and starch, and a germ separation device and a fiber separation device that are situated after the milling device, the germ separation device removes germ from the slurry and the fiber separation device removes fiber from the slurry. The system further includes a first apparatus that is situated after the germ and fiber separation devices and that receives the slurry including starch and initial protein and whereat a retentate, which includes residual protein, is added to the slurry from a later apparatus in the system, the first apparatus configured to separate the slurry into a starch stream and a gluten stream, including the combined initial and residual protein, wherein the addition of the retentate increases the overall concentration of protein in the slurry. The system further includes a second apparatus that is situated after the first apparatus and that receives the gluten stream from the first apparatus, the second apparatus configured to dewater the gluten stream to provide a first process liquid and a first dewatered gluten stream, including the combined protein, and a filtration device that is situated after the second apparatus and that receives the first process liquid, the filtration device configured to separate the first process liquid into a retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received at the first apparatus from the later apparatus in the system, and wherein the first dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt % protein on a dry basis.Brief Description of the Drawings

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate embodiments of the invention and, together with the general descriptionof the invention given above and the detailed description given below, serve to explain the principles of the invention. Similar reference numerals are used to indicate similar features throughout the various figures of the drawings.

[0017] FIG. 1 is a flow diagram of a typical wet mill alcohol production process; and

[0018] FIG. 2 is a method and system for increasing the yield and / or purity of protein in a gluten meal co-product by membrane filtration in a wet milling biochemical process in accordance with an embodiment of the invention.Detailed Description of Drawings

[0019] The present invention relates to a wet mill method of starch production from grain and increasing the yield and / or purity of protein (gluten) from such methods and systems that separate protein (gluten) from the gluten stream of a wet mill plant that produces a starch slurry and can derive a biofuel and / or biochemical, such as alcohol (e.g., ethanol), from the grain(s).

[0020] As discussed in detail above, Fig. 1 shows a flow diagram of a typical wet milling alcohol (e.g., ethanol) production method and system 10. Although virtually any type and quality of grain, such as but not limited to sorghum, wheat, triticale, barley, rye, tapioca, cassava, potato, pea and other starch and / or oil containing grains and / or legumes can be used to produce ethanol and / or a biochemical / biomolecule, for example, the feedstock for this process is typically com referred to as "No. 2 Yellow Dent Com."

[0021] Fig. 2 shows one embodiment of a method and system for increasing the yield and / or purity of protein in a wet mill process, collectively numeral 100, like the wet mill process 10 described in Fig. 1. Certain reference numerals used in Fig. 1 are used here to represent like devices and / or steps in the method and system 100. The variations of the embodiment of Fig. 2 are discussed hereinbelow.

[0022] As shown in Fig. 2 and as compared to Fig. 1, in this embodiment, the liquid fraction / process liquid from the optional gluten meal separation step 26, which can include a rotary drum vacuum filter (RDVF), can be optionally cooled in a heat exchanger 110, by means and methods known in the art, to a temperature suitable for operation with a selected / desired type of membrane filtration device 120 with the liquid fraction (cooled or not) ultimately beingsubjected to said membrane filtration device 120, as is further discussed below. In one example, the RDVF may be replaced by a membrane filtration device, like the membrane filtration device 120 discussed in detail further below. If the optional cooling heat exchanger 110 is not required, it may be eliminated altogether or the liquid fraction may be bypassed, manually or automatically by means and methods known in the art, around the cooling heat exchanger 110. Cooling the liquid fraction / process liquid (permeate) before it encounters the membrane filtration device 120 may change the performance thereof. As the liquid fraction is cooled, the solubility of high molecular weight dissolved solids can be reduced thereby allowing the membrane filtration device 120 to reject a higher percentage of soluble proteins and increase overall process yield and / or purity of protein when returned to the gluten separation step 24, as discussed further below. Additionally, the optionally cooled process liquid (permeate) may have a higher viscosity due to the lower temperature, which can also impact the separation efficiency or flux rate of the membrane filtration device 120. If the optional gluten meal separation step 26 is not present, alternatively, the liquid fraction / process liquid from the gluten thickener step 25 can be optionally cooled in the heat exchanger 110 to a temperature suitable for operation with the selected / desired type of membrane filtration device 120, with the liquid fraction (cooled or not) being subjected to said membrane filtration device 120, as further discussed below, to ultimately produce the retentate and process liquid.

[0023] With respect to the membrane filtration device 120, a wide variety of filter media are suitable for use as or within the membrane filtration device 120. In one example, any membrane filter with a pore size suitably small enough to exclude the passing of solids (including, for example, protein solids) and / or higher molecular weight dissolved solids can be used. Such membrane filters can include polymer membranes, sintered metal filters, coated filters, or ceramic filters, and the like. In one example, the pore size required for this type of application falls into the area normally described as microfiltration. In another example, ultrafiltration, which is the next step smaller in pore size, could also be used if the microfiltration method does not desirably reject / separate enough of the protein (gluten) solids that need to be recycled for recovery. In other words, the membrane filtration device 120 can be a microfdter, an ultrafilter, or a nanofilter. In one example, there may be more than one membrane filtration device 120, which may be the same or different type of device and can be arranged in series or parallel. Inone embodiment, the membrane filtration device 120 includes a microfiltration device followed by an ultrafiltration device.

[0024] In one example, the filtration membrane selected could be a flat sheet membrane. In another example, the membrane for the membrane filtration device 120 can be a spiral wound membrane since that design is more compact for a given filter surface area. Metal and ceramic filter elements also have lower surface area per volume and can require a larger footprint to install.

[0025] The temperature of the gluten slurry at the gluten meal separation step 26 generally has cooled to less than 100°F because the corn steeping process typically is run at a maximum of about 120°F and the slurry cools as it progresses through to gluten meal separation step 26 (or the gluten thickener step 25). Thus, there may not be a need for the optional cooling heat exchanger step 110 for the liquid faction (either from the gluten meal separation step 26 or the gluten thickener step 25) before it is subjected to the membrane filtration device 120. Although, the need or use for the optional cooling heat exchanger 110 is likely to be dependent, in large part, on the type of material in which the membrane filtration device 120 is constructed. Additionally, the optional cooling heat exchanger 110 can be utilized within the membrane filtration step, e.g., between multiple membrane filtration devices 120, as typically more than one membrane filtration device 120 is utilized in most circumstances. Most membrane filtration systems / devices 120 have a high recycle rate, e.g., a 10 to 1 ratio or higher or lower can be utilized within the membrane system for feed rate to recycle rate. This high recycle rate may generate frictional heat, which may need to be removed from the recycle stream to maintain a temperature that does not impact the membrane of the membrane filtration device 120 or cause any starch gelatinization or protein degradation issue if the temperature rises above 130°F.

[0026] For polymer-based filter membranes / membrane filtration devices 120, the temperature of the liquid faction being filtered may need to be cooled to a filtration temperature of as low as 120°F. If sintered metal, coated, or ceramic membrane filters / membrane filtration devices 120 are selected, the optional cooling heat exchanger may be bypassed or eliminated altogether. These types of filters can be capable of handling a hot 190°F feed material and, thus, the liquid fraction / centrate can be pumped directly to the membrane filtration device 120. Theoptional cooling heat exchanger 110 to be used in cooling the liquid faction could be a shell and tube or a plate and frame type heat exchanger, as are known in the art. In one example, cooling tower water may be the most readily available media for the cold side of the optional cooling heat exchanger 110. Other process streams / stream liquid may be utilized along with or instead of cooling tower water for cooling the liquid faction, as needed / desired.

[0027] The liquid faction from the gluten meal separation step 26 (or the gluten thickener step 25) can be pumped directly into the membrane filtration device 120. The membrane filtration device 120 could be set up for either cross flow or perpendicular flow. A cross flow installation typically will have a longer run time between filter changes out due to the scouring nature of flow across the filter surface.

[0028] Solids, high molecular weight dissolved solids, including proteins (and oils) are rejected / separated by the filter media / membrane filtration device 120 and are concentrated in the retentate. Low molecular weight dissolved solids will pass through the filter / membrane filtration device 120 (along with water) as the permeate / process liquid. The concentrated proteins from the retentate, i.e., all or a portion of the retentate, can be returned to the gluten separation step 24 to further enhance the gluten meal grain co-product by increasing the protein content (gluten) therein so that the gluten meal can be sold at a higher cost. At the gluten separation step 24, the recycled protein combines with the thickened starch / gluten slurry stream and can be subjected to one or more centrifuge(s), such as a nozzle bowl type centrifuge, and / or hydrocyclone(s). Again, the starch is denser than the protein (gluten) and can be carried out in the underflow of the centrifuge, and the lighter protein (gluten) stream can exit with the overflow. The additional / recycled protein will increase the yield of the protein (gluten) versus a typical process described in Fig. 1.

[0029] The gluten stream next can be subjected to the gluten thickener step 25 to remove the portion of the water by means and methods known in the art, which can include the decanter centrifuge, for example, thereby providing a thicker / thickened gluten slurry. The recovered process liquid can be returned as process water and used at a step earlier in the method 10, such as at steeping step 12, as explained above, or alternatively subjected to the optional cooling heater exchanger 110 and membrane filtration device 120 if the gluten meal separation step 26 isnot present. The now thickened gluten slurry, with its higher protein concentration, can be separated at the gluten meal separation step 26 using the rotary drum vacuum filter (RDVF), for example. The water in the slurry passes through the cloth on the drum of the filter and the gluten is collected as a wet cake, which includes a higher protein yield than the typical process. The eventual recovered process liquid from the gluten meal separation step 26 (or the gluten thickener step 25 if the gluten meal separation step 26 is not present) can be returned as process water and used at a step earlier in the method 10, such as at steeping step 12, as explained above. In one example, the rotary drum vacuum filter may be replaced by a belt filter, a filter press, and the like.

[0030] The protein (gluten) wet cake can be dried and sold as an animal feed (gluten meal) at a higher cost / greater revenue due to its increased protein content and yield. That is, the additional protein material being captured and recycled / returned back to the gluten separation step 24 from the membrane filtration device 120 further desirably increases the yield and / or purity of protein in the resulting gluten meal product. In one example, the resulting gluten (protein) meal (co)product, which defines a high protein grain (e.g., corn) meal, can include at least 58 wt% protein on a dry basis and which may be sold as pig or chicken feed, for example. In another embodiment, the high gluten (protein) meal includes at least 62 wt% protein on a dry basis. In still another embodiment, the high gluten (protein) meal includes at least 68 wt% protein on a dry basis. In yet another embodiment, the high gluten (protein) meal includes at least 70 wt% protein on a dry basis. In one embodiment, the high gluten (protein) meal can include from about 58 wt% to about 70 wt% protein on a dry basis. In another embodiment, the high gluten (protein) meal can include from about 60 wt% to about 70 wt%. In another embodiment, the high gluten (protein) meal can include from about 65 wt% to about 70 wt% or greater.

[0031] While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. While all or a portion of the retentate can be recycled / returned back to the gluten separation step 24, in one embodiment, the retentate may remain completely separate from the gluten separation step 24, i.e., not returned at all, to provide a separate protein / protein mealproduct(s). The various features shown and described herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described.Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant’ s general inventive concept.

Claims

What is claimed is:

1. A method for increasing the yield and / or purity of protein in a gluten meal coproduct produced in a wet mill plant that can derive a biofuel and / or biochemical from grain, the method comprising: steeping grain in an acid solution for a desired period of time to soften the grain; milling the softened grain to provide a slurry, including germ, initial protein, fiber, and starch; removing the germ and fiber from the slurry; thereafter, adding at least a portion of a retentate, which includes residual protein, that is received from a later step in the method to the slurry, and separating the slurry into a starch stream and a gluten stream, including the combined initial and residual protein, wherein the addition of the retentate increases the overall concentration of protein in the slurry; thereafter, dewatering the gluten stream to provide a first process liquid and a first dewatered gluten stream, including the combined protein; and filtering the first process liquid to provide the retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received from the later step in the method, and wherein the first dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt% protein on a dry basis.

2. The method of claim 1 wherein the gluten meal coproduct includes from 58 wt % to 70 wt % protein on a dry basis.

3. The method of claim 1 wherein separating the slurry into a starch stream and a gluten stream comprises separating the slurry, via a centrifuge or a hydrocyclone, into the starch and gluten streams.

4. The method of claim 1 wherein dewatering the gluten stream to provide a first process liquid and a first dewatered gluten stream comprises dewatering the gluten stream, via a centrifuge, to provide a first process liquid and a first dewatered gluten stream.

5. The method of claim 1 further comprising cooling the first process liquid prior to filtering the first process liquid to provide the retentate and permeate.

6. The method of claim 5 wherein the first process liquid is cooled to a temperature less than 120°F.

7. The method of claim 1 further comprising cooling the first process liquid, via a heat exchanger, prior to filtering the liquid fraction to provide the retentate and permeate.

8. The method of claim 1 wherein filtering the first process liquid to provide the retentate and permeate includes filtering via a membrane.

9. The method of claim 1 wherein filtering the first process liquid to provide the retentate and permeate includes microfiltering, ultrafiltering, or nanofiltering the first process liquid.

10. The method of claim 1 further comprising cooling the first process liquid, via a heat exchanger, prior to filtering the liquid fraction to provide the retentate and permeate, and microfiltering, ultrafiltering, or nanofiltering the first process liquid, via a membrane, to provide the retentate and permeate.

11. The method of claim 1 further comprising dewatering the first dewatered gluten stream to provide a second process liquid and a second dewatered gluten stream, including the combinedprotein; and filtering the second process liquid to provide the retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received from the later step in the method, and wherein the second dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt% protein on a dry basis.

12. The method of claim 11 further comprising cooling the second process liquid prior to filtering the second process liquid to provide the retentate and permeate.

13. The method of claim 11 wherein filtering the second process liquid to provide the retentate and permeate includes microfiltering, ultrafiltering, or nanofiltering the second process liquid.

14. The method of claim 11 wherein dewatering the first dewatered gluten stream to provide a second process liquid and a second dewatered gluten stream comprising dewatering the first dewatered gluten stream, via a rotary drum vacuum filter, to provide a second process liquid and a second dewatered gluten stream.

15. The method of claim 1 wherein the grain is com.

16. The method of claim 1 wherein the biofuel and / or biochemical production process is an alcohol production process.

17. A method for increasing the yield and / or purity of protein in a gluten meal coproduct produced in a wet mill plant that can derive a biofuel and / or biochemical from grain, the method comprising: steeping grain in an acid solution for a desired period of time to soften the grain;milling the softened grain to provide a slurry, including germ, initial protein, fiber, and starch; removing the germ and fiber from the slurry; thereafter, adding at least a portion of a retentate, which includes residual protein, that is received from a later step in the method to the slurry, and separating the slurry into a starch stream and a gluten stream, including the combined initial and residual protein, wherein the addition of the retentate increases the overall concentration of protein in the slurry; thereafter, dewatering the gluten stream to provide a first process liquid and a first dewatered gluten stream, including the combined protein; dewatering the first dewatered gluten stream to provide a second process liquid and a second dewatered gluten stream, including the combined protein; cooling the second process liquid, via a heat exchanger, followed by filtering the cooled second process liquid to provide the retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received from the later step in the method, and wherein the second dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt% protein on a dry basis.

18. A system for increasing the yield and / or purity of protein in a gluten meal coproduct produced in a wet mill plant that can derive a biofuel and / or biochemical from grain, the system comprising: a milling device that receives and grinds softened grain from a steeping process to provide a slurry, including germ, initial protein, fiber, and starch; a germ separation device and a fiber separation device that are situated after the milling device, the germ separation device removes germ from the slurry and the fiber separation device removes fiber from the slurry; a first apparatus that is situated after the germ and fiber separation devices and that receives the slurry including starch and initial protein and whereat a retentate, which includesresidual protein, is added to the slurry from a later apparatus in the system, the first apparatus configured to separate the slurry into a starch stream and a gluten stream, including the combined initial and residual protein, wherein the addition of the retentate increases the overall concentration of protein in the slurry; a second apparatus that is situated after the first apparatus and that receives the gluten stream from the first apparatus, the second apparatus configured to dewater the gluten stream to provide a first process liquid and a first dewatered gluten stream, including the combined protein; and a filtration device that is situated after the second apparatus and that receives the first process liquid, the filtration device configured to separate the first process liquid into a retentate, including residual protein, and a permeate, wherein the retentate defines the retentate received at the first apparatus from the later apparatus in the system, wherein the first dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt % protein on a dry basis.

19. The system of claim 18 wherein the gluten meal coproduct includes from 58 wt % to 70 wt % protein on a dry basis.

20. The system of claim 18 wherein the first apparatus is a centrifuge or hydrocyclone, the second apparatus is a centrifuge, and the filtration device is a membrane filtration device.

21. The system of claim 18 further comprising a cooling device that is situated after the second apparatus and before the filtration device, the cooling device configured to receive and cool the first process liquid prior to being subjected to the filtration device.

22. The system of claim 21 wherein the first process liquid is cooled to a temperature less than 120°F.

23. The system of claim 21 wherein the cooling device is a heat exchanger.

24. The system of claim 18 wherein the filtration device is one of a microfiltration device, ultrafiltration device, or a nanofiltration device.

25. The system of claim 18 further comprising a third apparatus that is situated after the second apparatus and that receives the first dewatered gluten stream, including the combined protein, from the second apparatus, the third apparatus configured to dewater the first dewatered gluten stream to provide a second process liquid and a second dewatered gluten stream, including the combined protein, and wherein the filtration device receives the second process liquid and is configured to separate the second process liquid into the retentate, including residual protein, and the permeate, and wherein the second dewatered gluten stream defines a gluten meal coproduct that includes at least 58 wt % protein on a dry basis.

26. The system of claim 25 wherein the third apparatus is a rotary drum vacuum filter.

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