Method for preparing protein from corn soaking water

Abstract

The invention discloses a method for preparing protein from corn soaking water, and belongs to the technical field of protein preparation. Comprising the following steps: settling corn soaking water, and taking supernate; adsorbing the supernate by anion exchange resin, and collecting effluent; separating the effluent through a hollow fiber membrane separation system, and filtering to 2-3% of the original volume to obtain a first trapped fluid and a first permeate; wherein the operation pressure of the hollow fiber membrane is 0.3-0.4 MPa, and the first permeate is reversely fed for 30-40 seconds every time the hollow fiber membrane is operated for 40-50 minutes; filtering the first permeate by using a 100-200Da nanofiltration membrane, and concentrating until the solid content is 20-40wt% to obtain a second trapped fluid and a second permeate; separating the second trapped fluid by adopting a simulated moving bed chromatographic separation technology, and respectively collecting an organic phase and a salt phase; and concentrating the organic phase by a reverse osmosis membrane until the solid content is 20-35wt%, then thermally concentrating until the solid content is 40-50wt%, and drying to obtain a protein product with the protein content of more than 65%. Protein products can be obtained from the corn soaking water, and the protein content reaches up to 65% or above.

Description

Technical Field

[0001] The invention relates to the technical field of potassium phytate preparation, and in particular to a method for preparing protein by using corn soaking water. Background Art

[0002] Corn soaking water is the waste product produced in the process of wet production of corn starch. my country is the world's largest corn starch producer, producing about 30 million tons of corn starch each year, and producing about 35 million tons of corn soaking water. Corn soaking water is rich in nutrients, with a dry matter concentration of about 10wt%-13wt% (including 5-6wt% protein concentration, 1-1.2wt% phytic acid concentration, 2.0-2.4wt% organic acid concentration, and 1.8-2.0wt% ash). How to use economical and applicable methods to separate these substances, prepare them into corresponding products for sale, and improve the comprehensive economic benefits of the corn processing industry chain is the goal that the majority of scientific researchers have been working hard for.

[0003] The protein in corn soaking water is water-soluble protein with multiple biological activities and functional properties. Its unique structure and properties make it have broad application prospects in the fields of feed, food, medicine, cosmetics, fertilizer, etc. At present, the industrial use of protein in corn soaking water is concentrated in the feed industry. According to existing literature reports, the development and utilization of protein in corn soaking water can not only expand the source of feed protein, but also avoid the environmental pressure caused by the discharge of corn soaking water, which has extremely high economic and social benefits. The existing processes mostly use simple acid-base neutralization and impurity removal or membrane technology separation. There is protein precipitation loss in the acid-base neutralization and impurity removal process, and the separation degree of membrane technology is limited, resulting in low protein content and yield, and it is impossible to obtain high-value products. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing protein using corn soaking water, so as to solve the problem of low protein content and low yield of corn protein obtained by simple acid-base neutralization and impurity removal or membrane technology separation in the prior art.

[0005] In a first aspect, the present invention provides a method for preparing protein using corn steep water, comprising the following steps:

[0006] After the corn soaking water has settled, take the supernatant;

[0007] After the supernatant is adsorbed by an anion exchange resin, the effluent is collected;

[0008] The effluent is separated by a hollow fiber membrane separation system and filtered to 2-3% of the original volume to obtain a first retentate and a first permeate; wherein the hollow fiber membrane has an operating pressure of 0.3-0.4 MPa, and the permeate is reverse-fed for 30-40 seconds every 40-50 minutes of operation;

[0009] Filtering the first permeate with a 100-200Da nanofiltration membrane and concentrating it to a solid content of 20-40wt%, obtaining a second retentate and a second permeate;

[0010] The second retentate is separated by using simulated moving bed chromatography separation technology to collect the organic phase and the salt phase respectively;

[0011] The organic phase is concentrated to a solid content of 20-35 wt% by reverse osmosis membrane, then heat-concentrated to a solid content of 40-50 wt%, and dried to obtain a protein product with a protein content of more than 65%.

[0012] Furthermore, after the supernatant is adsorbed by anion exchange resin, a purified water top resin is used, and the water top liquid is combined with the effluent; or,

[0013] The loading speed of the supernatant is 1-4 BV / h, and the loading volume is 8-12 BV of the resin volume; or,

[0014] The loading speed of the water top liquid is 2-4 BV / h, and the loading amount is 1-3 BV of the resin volume.

[0015] Furthermore, 5-10 wt% hydrochloric acid is used to analyze the adsorbed anion exchange resin. During the analysis, the loading speed is 1.0-3.0 BV / h, the loading amount is 2.0-4.0 BV of the resin volume, and the analytical solution is concentrated to obtain the phytic acid product.

[0016] Furthermore, the second permeate is concentrated to a solid content of 10-20 wt % using a reverse osmosis membrane, and then hot-concentrated to a solid content of 40-55 wt % to obtain a concentrated solution for use as an organic fertilizer.

[0017] Furthermore, the operating temperature of the reverse osmosis membrane is 35-60° C., and the membrane pressure is 3.5-5.0 MPa.

[0018] Furthermore, the temperature of the hot concentrated liquid is 60 to 80° C., and the vacuum degree is -0.06 to -0.1 MPa.

[0019] Furthermore, the effluent is separated by a hollow fiber membrane separation system, filtered to 2-3% of the original volume, and then 30-60% of the volume of the first retentate is added with purified water for 2-3 times, and the obtained water-carrying permeate is combined with the first permeate.

[0020] Furthermore, the simulated moving bed resin model used in the second retentate is Lanxiao Technology S1850 calcium type resin, and the particle size of the resin particles is 220-320 um.

[0021] Furthermore, when the second retentate is separated by simulated moving bed chromatography separation technology, the feed volume of the second retentate is controlled to be 10-12% of the single column volume, the feed volume of the water circulation is controlled to be 43-45% of the single column volume, the feed volume of the water-collected protein is controlled to be 30-33% of the single column volume, and the feed volume of the water-collected salt is controlled to be 15-17% of the single column volume.

[0022] Furthermore, the operating temperature of the nanofiltration membrane is 40-55° C., and the membrane pressure is 2.0-5.0 MPa.

[0023] Compared with the prior art, the method for preparing protein with corn soaking water of the present invention has the following beneficial effects:

[0024] (1) A protein product can be obtained from corn soaking water. The product has a high protein content of more than 65% and can be used as a first-class product.

[0025] (2) In addition to protein products, organic fertilizer can also be obtained, which can increase the added value of the product.

[0026] (3) Phytic acid can be used as a raw material for inositol to prepare high value-added products;

[0027] (4) This process is simple and has a smooth flow. It is suitable for obtaining various products from corn soaking liquid and is conducive to the comprehensive utilization of raw materials. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] In a first aspect, the present invention provides a method for preparing protein using corn steep water, comprising the following steps:

[0030] Step S1: After the corn soaking water is settled, the supernatant is taken.

[0031] In this step, the corn soaking water sedimentation time can generally be selected to be 3 to 6 hours, and the supernatant is taken after sedimentation for later use. It should be understood that the sediment after sedimentation is generally mainly corn starch, which can be used as a feed additive after recovery.

[0032] Step S2: After the supernatant is adsorbed by an anion exchange resin, the effluent is collected.

[0033] In this step, when the anion exchange resin is adsorbed, the loading speed of the supernatant can be selected to be 1 to 4 BV / h, and the loading amount can be selected to be 8 to 12 BV of the resin volume. Optionally, in order to flush out the impurities, pollutants and residues remaining on the surface and in the pores of the anion exchange resin to better restore the exchange capacity of the resin, after the supernatant is adsorbed by the anion exchange resin, purified water can be used to top the anion exchange resin to remove impurities such as filtration residues in the resin. At this time, the loading speed of the water top liquid can be 2 to 4 BV / h, the loading amount can be 1 to 3 BV of the resin volume, and the water top effluent can be merged into the effluent.

[0034] Optionally, after the adsorption is completed, the anion exchange resin can also be analyzed. At this time, a hydrochloric acid solution with a mass concentration of 5-10% can be selected to analyze the adsorbed anion exchange resin. During the analysis, the loading speed can be 1.0-3.0BV / h, and the loading amount can be 2.0-4.0BV of the resin volume. The analytical solution obtained after the analysis can be concentrated to obtain a phytic acid product. In this step, 100-200Da acid-resistant nanofiltration membrane is used for concentration treatment when the phytic acid is concentrated, and the concentration pressure is 1.5-2.5MPa and the temperature is 25-45°C. Through analysis and membrane treatment, the added value of the product can be further improved, thereby improving the comprehensive utilization rate of the product.

[0035] For example, in the embodiment of the present invention, the anion exchange resin can be selected from Hebei Lijiang 201×7 resin, Xi'an Lanxiao LX-360 resin, Purolite A600MB resin, etc.

[0036] Step S3, separating the effluent through a hollow fiber membrane separation system, filtering to 2-3% of the original volume, and obtaining a first retentate and a first permeate; wherein the operating pressure of the hollow fiber membrane is 0.3-0.4 MPa, and the first permeate is back-fed for 30-40 seconds every 40-50 minutes of operation.

[0037] In this step, the hollow fiber membrane is an asymmetric structure, consisting of a fine surface layer and a porous support layer. The membrane material of the hollow fiber membrane can be selected as polyvinylidene fluoride. For example, the hollow fiber membrane model can be selected as NF-1~5. The main components of the first retentate obtained by hollow fiber membrane separation are starch that has not been completely precipitated, precipitated macromolecular proteins, etc., and the main components of the first permeate are small molecular proteins, lactic acid, inorganic salts, etc. Hollow fiber membranes are used instead of traditional ceramic membranes to separate and treat the effluent. Since the hollow fiber membrane core is relatively dense, the blockage of the hollow fiber membrane by particulate matter can be reduced, thereby improving the separation efficiency of the effluent.

[0038] Optionally, the effluent is separated by a hollow fiber membrane separation system, filtered to 2-3% of the original volume, and then 30-60% of the volume of the first retentate is added with purified water 2-3 times, and the obtained water-carrying permeate is combined with the first permeate.

[0039] Step S4, filtering the first permeate with a 100-200Da nanofiltration membrane and concentrating it to a solid content of 20-40wt%, to obtain a second retentate and a second permeate.

[0040] In this step, the operating temperature of the nanofiltration membrane can be selected to be 40-55°C, and the membrane pressure can be selected to be 2.0-5.0 MPa. The second retentate obtained by nanofiltration membrane separation mainly contains most of the protein, a small part of lactic acid, multivalent salts, etc., and the second permeate mainly contains most of the lactic acid, a small amount of small molecule amino acids and monovalent salts, etc.

[0041] Optionally, the second permeate can be further concentrated to a solid content of 10-20wt% by using a reverse osmosis membrane, wherein the operating temperature of the reverse osmosis membrane is 35-60°C and the membrane pressure is 3.5-5.0MPa. Then, the second permeate can be thermally concentrated to a solid content of 40-50wt%, wherein the feed liquid temperature is 60-80°C during thermal concentration and the vacuum degree is -0.06--0.1MPa. The products after the reverse osmosis membrane concentration and thermal concentration treatment mainly include lactic acid, a small amount of small molecule amino acids and potassium chloride, etc., which can be mainly used as organic fertilizer to further improve its comprehensive utilization rate.

[0042] Step S5: The second retentate is separated by using simulated moving bed chromatography separation technology to collect the organic phase and the salt phase respectively.

[0043] In this step, when the second retentate is separated by simulated moving bed chromatography separation technology, the particle size of the simulated moving bed resin chromatography is selected to be 220-320um, the resin model is Lanxiao Technology S1850 calcium type resin, and the feed volume of the second retentate is controlled to be 10-12% of the single column volume, the feed volume of the water cycle is 43-45% of the single column volume, the feed volume of the water protein is 30-33% of the single column volume, and the feed volume of the water salt is 15-17% of the single column volume. When using simulated moving bed chromatography separation, according to the difference in fluidity between the organic phase and the salt phase in the second retentate in the stationary phase and the mobile phase, the two are effectively separated, and the organic phase and the salt phase are collected separately.

[0044] Step S6, the organic phase is concentrated to a solid content of 20-35wt% by reverse osmosis membrane, then hot concentrated to a solid content of 40-50wt%, and dried to obtain a protein product with a protein content of >65%.

[0045] In this step, the operating temperature of the reverse osmosis membrane is 35-60°C, and the membrane pressure is 3.5-5.0MPa. The temperature of the hot concentrated liquid is 60-80°C, and the vacuum degree is -0.06--0.1MPa. After the above steps, a protein product with a protein content of more than 65% can be obtained from the corn soaking water. The protein product has a high protein content and can be used as a primary product, which greatly increases the added value of the product.

[0046] In order to better illustrate the technical solution of the present invention, the present invention also provides the following specific examples. It should be understood that the raw materials used in the following examples are all commercially available raw materials unless otherwise specified.

[0047] Example 1

[0048] This embodiment provides a method for preparing protein using corn soaking water, comprising the following steps:

[0049] Step S1, taking 100L corn soaking water and letting it settle for 3h, and taking the supernatant;

[0050] Step S2, the supernatant is adsorbed by an anion exchange resin at a loading rate of 1 BV / h and a loading volume of 8 BV of the resin volume, and the effluent is collected. In this embodiment, the anion exchange resin is Hebei Lijiang 201×7 resin;

[0051] Step S3, separating the effluent through a hollow fiber membrane separation system, filtering to 2% of the original volume, and obtaining a first retentate and a first permeate; wherein the hollow fiber membrane model is NF-1, the operating pressure of the hollow fiber membrane is 0.3 MPa, and the first permeate is reverse-fed for 30 seconds every 40 minutes of operation;

[0052] Step S4, filtering the first permeate with a 200Da nanofiltration membrane at an operating temperature of 40°C and a membrane pressure of 2.0MPa, and concentrating the first permeate to a solid content of 20wt%, to obtain a second retentate and a second permeate;

[0053] Step S5, the second retentate is separated by simulated moving bed chromatography separation technology, and the organic phase and the salt phase are collected respectively; wherein the particle size of the simulated moving bed resin chromatography is 220-240um, the resin model is Lanxiao Technology S1850 calcium type resin, and the feed volume of the second retentate is controlled to be 10% of the single column volume, the feed volume of the water circulation is 43% of the single column volume, the feed volume of the water protein is 30% of the single column volume, and the feed volume of the water salt is 15% of the single column volume;

[0054] Step S6, the organic phase is concentrated to a solid content of 20wt% by reverse osmosis membrane, and then hot concentrated to a solid content of 40wt%, wherein the operating temperature of the reverse osmosis membrane is 35°C and the membrane pressure is 3.5MPa. The hot concentrated liquid temperature is 60°C and the vacuum degree is -0.1MPa. After the above steps, 6.4kg of protein product can be obtained from the corn soaking water, and the protein content is 67.5wt%.

[0055] Example 2

[0056] This embodiment provides a method for preparing protein using corn soaking water, comprising the following steps:

[0057] Step S1, taking 100L corn soaking water and letting it settle for 4h, and taking the supernatant;

[0058] Step S2, the supernatant is loaded at a speed of 2.5 BV / h and the loading amount is 10 BV of the resin volume, and after adsorbing with an anion exchange resin, the effluent is collected. In this embodiment, the anion exchange resin selected is Xi'an Lanxiao LX-360 resin;

[0059] Step S3, separating the effluent through a hollow fiber membrane separation system, filtering to 3% of the original volume, and obtaining a first retentate and a first permeate; wherein the hollow fiber membrane model is NF-5, the operating pressure of the hollow fiber membrane is 0.4 MPa, and the first permeate is reverse-fed for 35 seconds every 45 minutes of operation;

[0060] Step S4, filtering the first permeate with a 150Da nanofiltration membrane at an operating temperature of 45°C and a membrane pressure of 3.5MPa, and concentrating the first permeate to a solid content of 30wt%, to obtain a second retentate and a second permeate;

[0061] Step S5, the second retentate is separated by simulated moving bed chromatography separation technology, and the organic phase and the salt phase are collected respectively; wherein the particle size of the simulated moving bed resin chromatography is 260-280um, the resin model is Lanxiao Technology S1850 calcium type resin, and the feed volume of the second retentate is controlled to be 11% of the single column volume, the feed volume of the water circulation is 44% of the single column volume, the feed volume of the water protein is 32% of the single column volume, and the feed volume of the water salt is 16% of the single column volume;

[0062] Step S6, the organic phase is concentrated to a solid content of 27wt% by reverse osmosis membrane, and then hot concentrated to a solid content of 45wt%, wherein the operating temperature of the reverse osmosis membrane is 50°C and the membrane pressure is 4.0MPa. The hot concentrated liquid temperature is 70°C and the vacuum degree is -0.09MPa. After the above steps, 6.5kg of protein product can be obtained from the corn soaking water, and the protein content is 68.3wt%.

[0063] Example 3

[0064] This embodiment provides a method for preparing protein using corn soaking water, comprising the following steps:

[0065] Step S1, taking 100L corn soaking water and letting it settle for 6h, and taking the supernatant;

[0066] Step S2, the supernatant is loaded at a rate of 4 BV / h and a loading amount of 12 BV of the resin volume, and after adsorbing with an anion exchange resin, the effluent is collected. In this embodiment, the anion exchange resin is selected as Purolite A600MB resin;

[0067] Step S3, separating the effluent through a hollow fiber membrane separation system, filtering to 3% of the original volume, and obtaining a first retentate and a first permeate; wherein the hollow fiber membrane model is NF-3, the operating pressure of the hollow fiber membrane is 0.4 MPa, and the first permeate is reverse-fed for 40 seconds every 50 minutes of operation;

[0068] Step S4, filtering the first permeate with a 100Da nanofiltration membrane at an operating temperature of 55°C and a membrane pressure of 5.0MPa, and concentrating the first permeate to a solid content of 40wt%, to obtain a second retentate and a second permeate;

[0069] Step S5, the second retentate is separated by simulated moving bed chromatography separation technology, and the organic phase and the salt phase are collected respectively; wherein the particle size of the simulated moving bed resin chromatography is 300-320um, the resin model is Lanxiao Technology S1850 calcium type resin, and the feed volume of the second retentate is controlled to be 12% of the single column volume, the feed volume of the water circulation is 45% of the single column volume, the feed volume of the water protein is 33% of the single column volume, and the feed volume of the water salt is 17% of the single column volume;

[0070] Step S6, the organic phase is concentrated to a solid content of 35wt% by reverse osmosis membrane, and then hot concentrated to a solid content of 50wt%, wherein the operating temperature of the reverse osmosis membrane is 60°C and the membrane pressure is 5.0MPa. The hot concentrated liquid temperature is 80°C and the vacuum degree is -0.06MPa. After the above steps, 6.7kg of protein product can be obtained from the corn soaking water, and the protein content is 66.1wt%.

[0071] Example 4

[0072] The only difference between this embodiment and embodiment 2 is that in step S2, after the adsorption is completed, a hydrochloric acid solution with a mass concentration of 7% is selected to parse the adsorbed anion exchange resin. During the parsing, the loading rate is 2.0BV / h, and the loading amount can be 3.0BV of the resin volume. The parsed solution obtained after the parsing is concentrated by a 100Da acid-resistant nanofiltration membrane, the concentration pressure is 2.0MPa, and the temperature is 35°C, to obtain 5.7kg of phytic acid product with a concentration of 21wt%.

[0073] Example 5

[0074] The difference between this embodiment and embodiment 2 is that in step S2, after the adsorption is completed, purified water is used to top anion exchange resin to remove impurities such as filtration residues in the resin. The loading rate of the water top liquid is 3BV / h, the loading amount is 2BV of the resin volume, and the water top effluent can be combined with the effluent.

[0075] After the water top is completed, a hydrochloric acid solution with a mass concentration of 5% is selected to parse the adsorbed anion exchange resin. During the analysis, the loading speed is 1.0BV / h, and the loading amount can be 2.0BV of the resin volume. The analyzed solution obtained after the analysis is concentrated by a 200Da acid-resistant nanofiltration membrane, the concentration pressure is 2.5MPa, the temperature is 25°C, and 6.7kg of phytic acid product with a concentration of 18wt% is obtained.

[0076] Example 6

[0077] The difference between this embodiment and embodiment 2 is that in step S4, the second permeate is treated as follows: the second permeate is further concentrated to a solid content of 15wt% by using a reverse osmosis membrane, wherein the operating temperature of the reverse osmosis membrane is 45°C and the membrane pressure is 4MPa. Then, the second permeate is thermally concentrated to a solid content of 45wt%, wherein the feed liquid temperature is 70°C and the vacuum degree is -0.09MPa during thermal concentration. After reverse osmosis membrane concentration and thermal concentration treatment, 8.8kg of organic fertilizer product is obtained, which mainly includes lactic acid, a small amount of small molecule amino acids and potassium chloride.

[0078] Comparative Example 1

[0079] Compared with Example 2, the difference is that: step S4 uses a reverse osmosis membrane instead of a nanofiltration membrane to filter the first permeate, the operating temperature of the reverse osmosis membrane is 45°C, the membrane pressure is 3.5MPa, and other process conditions and parameters remain unchanged. 8.2kg of protein product can be obtained from corn soaking water, and the protein product has a protein content of 55.2%.

[0080] Comparative Example 2

[0081] Compared with Example 2, the difference is that the particle size of the simulated moving bed resin chromatography in step S5 is replaced with 600-700 um, and other process parameters remain unchanged. 7.6 kg of protein product with a protein content of 56.1% can be obtained from corn soaking water.

[0082] Comparative Example 3

[0083] Compared with Example 2, the ceramic membrane in step S3 replaces the hollow fiber membrane to separate the effluent, the pore size of the ceramic membrane is 8 nm, the operating pressure is 0.4 MPa, and the operating temperature is 40° C. 6.2 kg of protein product can be obtained from the corn soaking water, and the protein content of the protein product is 63.7%.

[0084] It can be seen from the results of the embodiments and comparative examples that the protein content of the protein products obtained by the separation process of the present invention is higher than 65%, compared with the protein content of the protein products obtained in the comparative examples being only 55.2% to 63.7%. The impurity content in the protein products is high, resulting in a lower protein content in the protein products.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing protein using corn soaking water, characterized in that: The following steps are involved: After the corn soaking water has settled, take the supernatant; After the supernatant is adsorbed by an anion exchange resin, the effluent is collected; The effluent is separated by a hollow fiber membrane separation system and filtered to 2-3% of the original volume to obtain a first retentate and a first permeate; wherein the hollow fiber membrane has an operating pressure of 0.3-0.4 MPa, and the first permeate is reverse-fed for 30-40 seconds every 40-50 minutes of operation; Filtering the first permeate with a 100-200Da nanofiltration membrane and concentrating it to a solid content of 20-40wt%, obtaining a second retentate and a second permeate; The second retentate is separated by using simulated moving bed chromatography separation technology to collect the organic phase and the salt phase respectively; The organic phase is concentrated to a solid content of 20-35 wt% by reverse osmosis membrane, then heat-concentrated to a solid content of 40-50 wt%, and dried to obtain a protein product with a protein content of more than 65%.

2. The method for preparing protein using corn soaking water according to claim 1, characterized in that: After the supernatant is adsorbed by anion exchange resin, purified water top resin is used, and the water top liquid is combined with the effluent; or, The loading speed of the supernatant is 1-4 BV / h, and the loading volume is 8-12 BV of the resin volume; or, The loading speed of the water top liquid is 2-4 BV / h, and the loading amount is 1-3 BV of the resin volume.

3. The method for preparing protein using corn soaking water according to claim 1 or 2, characterized in that: The anion exchange resin after adsorption is analyzed by using 5-10wt% hydrochloric acid. During the analysis, the loading speed is 1.0-3.0BV / h, the loading amount is 2.0-4.0BV of the resin volume, and the analytical solution is concentrated to obtain the phytic acid product.

4. The method for preparing protein by using corn soaking water according to claim 1, characterized in that: The second permeate is concentrated to a solid content of 10-20 wt % by using a reverse osmosis membrane, and then hot concentrated to a solid content of 40-55 wt % to obtain a concentrated solution for use as an organic fertilizer.

5. The method for preparing protein by using corn soaking water according to claim 1 or 4, characterized in that: The operating temperature of the reverse osmosis membrane is 35-60° C., and the membrane pressure is 3.5-5.0 MPa.

6. The method for preparing protein using corn soaking water according to claim 1 or 4, characterized in that: The temperature of the hot concentrated liquid is 60-80°C, and the vacuum degree is -0.06--0.1MPa.

7. The method for preparing protein by using corn soaking water according to claim 1, characterized in that: The effluent is separated by a hollow fiber membrane separation system, filtered to 2-3% of the original volume, and then 30-60% of the volume of the first retentate is added with purified water for 2-3 times, and the obtained water-carrying permeate is combined with the first permeate.

8. The method for preparing protein using corn soaking water according to claim 1, characterized in that: The simulated moving bed resin model used in the second retentate is Lanxiao Technology S1850 calcium type resin, and the particle size of the resin particles is 220-320um.

9. The method for preparing protein by using corn soaking water according to any one of claims 1 to 8, characterized in that: When the second retentate is separated by simulated moving bed chromatography separation technology, the feed volume of the second retentate is controlled to be 10-12% of the single column volume, the feed volume of the water cycle is controlled to be 43-45% of the single column volume, the feed volume of the water-collected protein is controlled to be 30-33% of the single column volume, and the feed volume of the water-collected salt is controlled to be 15-17% of the single column volume.

10. The method for preparing protein by using corn soaking water according to any one of claims 1 to 9, characterized in that: The operating temperature of the nanofiltration membrane is 40-55° C., and the membrane pressure is 2.0-5.0 MPa.