A method for extracting zearalenone from corn steep liquor to prepare a crude standard product

Abstract

The present invention belongs to the technical field of zearalenone extraction and relates to a method for extracting zearalenone from corn steep liquor to prepare a crude standard. The method comprises centrifuging corn steep liquor containing ZEN to obtain a supernatant; treating the supernatant using a PA66 membrane to obtain a PA66 membrane enriched with ZEN; eluting the PA66 membrane enriched with ZEN to obtain an eluate; and purifying the eluate by rotary evaporation to obtain a crude ZEN standard. The PA66 membrane is used to enrich and extract ZEN from ZEN-contaminated corn byproducts, achieving an enrichment and extraction efficiency exceeding 90%, providing a reliable and effective method for the high-value utilization of corn byproducts. The PA66 membrane is used to efficiently and selectively adsorb and enrich ZEN to initially prepare a crude ZEN standard, providing a new approach to the preparation of ZEN standard products.

Description

Technical Field

[0001] The invention relates to the technical field of zearalenone extraction, in particular to a method for extracting zearalenone from corn steep liquor to prepare a crude standard product. Background Art

[0002] Corn is a staple food crop. With rising living standards, demand for products such as fuel ethanol, amino acids, and corn starch has increased dramatically. As the primary raw material for these products, corn consumption has also surged. According to statistics, large-scale enterprises primarily processing these products have an annual corn processing capacity exceeding 11 million tons. However, corn is highly susceptible to fungal contamination during the growing season and post-harvest storage and transportation, leading to yield losses and reduced crop value. The most prominent mycotoxins in corn are zearalenone (ZEN), aflatoxins (AFs), and deoxynivalenol (DON), with global average prevalence rates of 48%, 45%, and 52%, respectively. Due to their chemical stability, ZEN and AFs are not readily degraded by various processing technologies applied to corn raw materials. After extensive processing, 0.576 tons of corn steep liquor are generated per ton of corn. ZEN and AFs gradually accumulate in this steep liquor, significantly exceeding regulatory limits. This leads to the direct disposal of byproducts, placing a burden on the environment and causing significant economic losses. Therefore, the development and utilization of contaminated corn processing by-products is a top priority.

[0003] Since its isolation and characterization from infected corn, ZEN has been extensively studied. ZEN is a secondary metabolite produced by Fusarium fusae via the polyketide pathway. Its structure is similar to estrogen, and it primarily exerts estrogen-like effects on various organisms. Exposure to ZEN contamination has been found to have carcinogenic, hepatotoxic, and teratogenic effects (Han et al., 2022), and the International Agency for Research on Cancer has designated it as a Class III carcinogen. Many countries and organizations have established standards that strictly limit the maximum residue levels of ZEN in corn and corn by-products. ZEN standards are crucial for analysis and are directly related to the accuracy of the results. Currently, ZEN standards are expensive and are primarily synthesized through cumbersome chemical methods. Enriching ZEN from contaminated corn by-products provides a new approach for the preparation of ZEN standards and an effective way to increase the value of corn and other by-products.

[0004] Adsorption has been widely used for preconcentration due to its simplicity, high efficiency, low cost, and low toxicity. The type of adsorbate, adsorbent, and operating conditions are the main factors determining extraction efficiency. Various adsorbents with large surface areas, such as montmorillonite, zeolites, metal-organic frameworks, carbon materials, and polymers, have been studied and demonstrated promising performance. The interactions between the adsorbate and the adsorbent primarily include electrostatic, π-π, hydrophobic, acid-base, hydrogen bonding, and van der Waals interactions. Adsorption can be categorized as physical adsorption or chemical adsorption based on the interactions involved. Because physical adsorption is dominated by weak intermolecular forces, namely van der Waals forces or dispersion forces, the adsorbent can be easily regenerated and retain its original structure. Chemical adsorption, attributed to chemical reactions between the adsorbent's surface functional groups and the adsorbate, exhibits higher selectivity than physical adsorption. However, unlike reversible physical adsorption, chemical adsorption is generally irreversible due to the strong chemical bonds, and the adsorbate's original form may change during desorption. In actual adsorption processes, physical and chemical adsorption occur simultaneously, resulting in a dynamic equilibrium of continuous adsorption and desorption.

[0005] With recycling and reuse in mind, adsorbents have been made into membranes for adsorption, supported by various types of polymer membranes. Wan et al. have successfully obtained a polydopamine-coated sandwich structure membrane for the effective removal of AFB1 (Ren et al., 2019; Wu et al., 2020). Wang et al. prepared a nylon-6-based fiber membrane (Ji et al., 2023) for the selective adsorption and enhanced photocatalytic reduction of Cr(VI) in water. Bruggen et al. used polyethersulfone as a substrate to prepare a new thin-film nanocomposite membrane to achieve effective capture and rapid release of endocrine disrupting compounds (Liu et al., 2022). Due to the presence of functional groups on the polymer membrane that can interact with the target substrate, the adsorption efficiency cannot be attributed solely to the contribution of the adsorbent.

[0006] Therefore, how to efficiently enrich ZEN pollutants, provide a high-value utilization method for corn by-products, and provide a supporting theory for the preparation of ZEN standard substances has become an urgent problem that technicians in this field need to overcome. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for extracting zearalenone from corn steep liquor to prepare a crude standard product, so as to solve the problems existing in the above-mentioned prior art.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] One of the technical solutions of the present invention is to provide an application of a PA66 membrane in enriching ZEN.

[0010] The second technical solution of the present invention is to provide a method for extracting zearalenone from corn steep liquor to prepare a crude standard product, the steps comprising:

[0011] The corn steep liquor containing ZEN is centrifuged to obtain a supernatant;

[0012] The supernatant is treated with a polyamide 66 (PA66) membrane to obtain a PA66 membrane enriched with ZEN;

[0013] Eluting the PA66 membrane enriched with ZEN to obtain an eluate;

[0014] The eluate was subjected to rotary evaporation purification to obtain a crude standard of ZEN.

[0015] Furthermore, the centrifugal speed is 5000 rpm and the time is 5 minutes.

[0016] Furthermore, the pore size of the PA66 membrane is 0.22-0.45 μm.

[0017] Furthermore, the use of a PA66 membrane to treat the supernatant comprises: using PA66 as a membrane, filtering the ZEN in the supernatant with PA66 for adsorption and enrichment.

[0018] Furthermore, the eluent used for the elution is acetonitrile.

[0019] Furthermore, the temperature of the rotary evaporation purification is 60° C. and the time is 10 min.

[0020] The third technical solution of the present invention is to provide a method for removing ZEN from corn by-products containing ZEN, comprising the following steps:

[0021] Centrifuging the ZEN-containing corn by-product for solid-liquid separation to obtain a solid portion and a supernatant;

[0022] The supernatant is treated with a polyamide 66 (PA66) membrane to obtain a filtrate from which ZEN is removed;

[0023] The filtrate and the solid portion are combined to obtain the ZEN-removed corn by-product.

[0024] Furthermore, the ZEN-containing corn by-products include corn steep liquor and corn steep liquor.

[0025] Furthermore, the centrifugal speed is 5000 rpm and the time is 5 minutes.

[0026] Furthermore, the pore size of the PA66 membrane is 0.22-0.45 μm, preferably 0.22 μm or 0.45 μm.

[0027] Furthermore, the use of a PA66 membrane to treat the supernatant comprises: using PA66 as a membrane, filtering the ZEN in the supernatant with PA66 for adsorption and enrichment.

[0028] The present invention discloses the following technical effects:

[0029] This invention utilizes a PA66 membrane to enrich and extract ZEN from ZEN-contaminated corn byproducts, achieving an extraction efficiency exceeding 90%. This provides a reliable and effective method for increasing the value of corn byproducts. This invention utilizes a PA66 membrane to efficiently and selectively adsorb and enrich ZEN to prepare a preliminary ZEN standard, providing a new approach for the preparation of ZEN standard products. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 Comparison of the enrichment efficiency of ZEN and AFB1 by PA66 membrane with a pore size of 0.22 μm in aqueous acetonitrile solutions of different concentrations, where (A) is 100% acetonitrile, (B) is 70% acetonitrile, (C) is 50% acetonitrile, (D) is 30% acetonitrile, and (E) is 10% acetonitrile.

[0032] Figure 2 The enrichment-desorption experimental results of PA66 membranes with pore sizes of 0.22 μm and 0.45 μm for different concentrations of ZEN and AFB1, wherein (A) is the enrichment-desorption experimental result of the 0.22 μm PA66 membrane for different concentrations of ZEN, (B) is the enrichment-desorption experimental result of the 0.22 μm PA66 membrane for different concentrations of AFB1, (C) is the enrichment-desorption experimental result of the 0.45 μm PA66 membrane for different concentrations of ZEN, and (D) is the enrichment-desorption experimental result of the 0.45 μm PA66 membrane for different concentrations of AFB1;

[0033] Figure 3 Figure 3 shows the results of repeated regeneration of PA66 membrane for ZEN and AFB1 enrichment, where (A) shows 10 consecutive ZEN enrichments without elution, (B) shows 10 consecutive ZEN enrichments with acetonitrile elution of the PA66 membrane after each enrichment, (C) shows 10 consecutive AFB1 enrichments without elution, and (D) shows 10 consecutive AFB1 enrichments with acetonitrile elution of the PA66 membrane after each enrichment.

[0034] Figure 4 SEM images of PA66 membranes before and after enrichment with ZEN or AFB1, where (A) is the PA66 membrane before enrichment, (B) is the PA66 membrane after enrichment with ZEN, and (C) is the PA66 membrane after enrichment with AFB1;

[0035] Figure 5 XPS graphs of PA66 membranes before and after enrichment with ZEN or AFB1, where (A), (D), and (G) are the C1s, O 1s, and N1s spectra of the PA66 membranes before enrichment, respectively; (B), (E), and (H) are the C1s, O1s, and N1s spectra of the PA66 membranes after enrichment with ZEN; (C), (F), and (I) are the C1s, O 1s, and N1s spectra of the PA66 membranes after enrichment with AFB1;

[0036] Figure 6 FT-IR images of PA66 membrane before and after enrichment of ZEN or AFB1;

[0037] Figure 7 The optimized DFT calculation model of PA66 membrane and the enrichment model of ZEN and AFB1 on PA66 membrane, where (A) is the optimized DFT calculation model of PA66 membrane, (B) is the enrichment model of ZEN on PA66 membrane, and (C) is the enrichment model of AFB1 on PA66 membrane;

[0038] Figure 8 Schematic diagram of the enrichment principle of ZEN and AFB1 by PA66 membrane. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] The present invention prepares ZEN-containing corn steep liquor by adding ZEN (ZEN provided by Sigma-Aldrich) at a concentration of 50 ppb to commercially available negative corn steep liquor (negative corn steep liquor provided by Hubei Kanglezi Food and Beverage Co., Ltd.), which is used in the examples and comparative examples.

[0045] The PA66 membrane used in the specific embodiment of the present invention has a pore size of 0.22 μm and a thickness of 0.1 mm.

[0046] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0047] Example 1

[0048] The steps for extracting zearalenone from corn steep liquor to prepare a crude standard are as follows:

[0049] S1. Centrifuge the corn steep liquor containing ZEN (5000 rpm, 5 min) to obtain a solid portion and a supernatant;

[0050] S2, using PA66 as a membrane, filtering the supernatant, so that PA66 adsorbs and enriches ZEN in the supernatant, and obtaining a PA66 membrane enriched with ZEN and a purified liquid, wherein, according to the PA66 membrane 1.06 mg / cm 2 Adsorption enrichment standard, preparation of PA66 membrane and supernatant;

[0051] S3, eluting the PA66 membrane enriched with ZEN using acetonitrile to obtain an eluate;

[0052] S4. Purify the eluate by rotary evaporation (60° C., 10 min), recover acetonitrile, and obtain a crude standard product of ZEN.

[0053] The purified liquid and the solid portion were mixed to obtain ZEN-free corn steep liquor. Detection showed that the concentration of ZEN in the ZEN-free corn steep liquor was 2.17 ppb, and the enrichment efficiency was 95%.

[0054] Enrichment efficiency = (1-C / C0) x 100%; wherein C is the ZEN concentration in the ZEN-containing corn steep liquor, and C0 is the ZEN concentration in the ZEN-depleted corn steep liquor.

[0055] Comparative Example 1

[0056] Compared with Example 1, the only difference is that the PA66 membrane is replaced by a polytetrafluoroethylene membrane (PTFE, pore size 0.22 μm).

[0057] Similarly, the purified liquid and the solid portion were mixed to obtain corn slurry. After testing, the concentration of ZEN in the corn slurry was 50 ppb, without any change, indicating that the PTFE membrane had no enrichment effect on ZEN.

[0058] Test example

[0059] Figure 1 Comparison of the enrichment efficiency of ZEN and AFB1 by PA66 membrane with a pore size of 0.22 μm in acetonitrile aqueous solution with different concentrations, where (A) is 100% acetonitrile, (B) is 70% acetonitrile, (C) is 50% acetonitrile, (D) is 30% acetonitrile, and (E) is 10% acetonitrile. Figure 1 As shown in (A) to (D), when the concentrations of ZEN and AFB1 ranged from 10 to 1000 ppb, the enrichment effect was negligible when the solvents were 100%, 70%, 50%, and 30% acetonitrile, respectively. This indicates that ZEN and AFB1 can pass through the PA membrane with almost no resistance in the four acetonitrile-water solutions described above. When the acetonitrile concentration was reduced to 10%, ZEN and AFB1 enrichment on the PA was observed, as shown in (E). The enrichment efficiencies of ZEN and AFB1 at all tested concentrations were approximately 90% and 10%, respectively, indicating that ZEN and AFB1 have a high affinity for hydrophobic PA. Error bars in the figures are the standard deviation of three measurements.

[0060] ZEN and AFB1 have good solubility in acetonitrile, so 100% acetonitrile was used as the eluent for the enrichment-desorption experiment. Figure 2 shown.

[0061] Figure 2The enrichment-desorption experimental results of PA66 membranes with pore sizes of 0.22μm and 0.45μm for different concentrations of ZEN and AFB1, among which, (A) is the enrichment-desorption experimental result of PA66 membrane with pore size of 0.22μm for different concentrations of ZEN, (B) is the enrichment-desorption experimental result of PA66 membrane with pore size of 0.22μm for different concentrations of AFB1, (C) is the enrichment-desorption experimental result of PA66 membrane with pore size of 0.45μm for different concentrations of ZEN, (D) is the enrichment-desorption experimental result of PA66 membrane with pore size of 0.45μm for different concentrations of AFB1. Figure 2 It can be seen that after elution with 100% acetonitrile, the enrichment efficiency of ZEN on the PA membrane is negligible, which means that almost all the enriched ZEN molecules are eluted; under the same conditions, the enriched AFB1 will also pass through the membrane during the elution process.

[0062] Repeated regeneration experiment of membrane: Using 100% acetonitrile as eluent and PA66 membrane with pore size of 0.22μm, repeated regeneration experiment was carried out. The enrichment process of ZEN and AFB1 was repeated on the same membrane, and the regeneration performance of PA66 membrane was judged by repeating it 10 times with or without elution. Among them, ZEN and AFB1 were added to 10% acetonitrile aqueous solution to make its concentration reach 500ppb, as the stock solution. The results are shown in the figure. Figure 3 shown.

[0063] Figure 3 The results of repeated regeneration of PA66 membrane for ZEN and AFB1 enrichment, where (A) is 10 consecutive ZEN enrichment without elution, (B) is 10 consecutive ZEN enrichment, and the PA66 membrane is eluted with acetonitrile after each enrichment, (C) is 10 consecutive AFB1 enrichment without elution, and (D) is 10 consecutive AFB1 enrichment, and the PA66 membrane is eluted with acetonitrile after each enrichment. Figure 3 It can be seen that, as shown in (A), in the absence of elution as a cleaning process, the ZEN enrichment efficiency dropped sharply from 90% to 10% after seven reuse cycles and remained stable in the next three reuse cycles. This is because the active sites of the membrane were gradually occupied; in contrast, in (B), when an additional elution process of 100% acetonitrile was performed after each cycle, the ZEN enrichment performance could be basically maintained at 81.3% after ten reuse cycles; for AFB1, there was no elution process in (C), and the enrichment of the PA66 membrane quickly reached saturation in the second cycle, indicating that the PA66 membrane had few enrichment sites for AFB1; in (D), 100% acetonitrile was eluted after each use, and the enrichment of AFB1 remained stable at 9.7%. It can be seen that 100% acetonitrile can be used as an effective regeneration agent for desorption of PA66 membrane. Furthermore, Figures 2-3It can be shown that PA66 membrane has a certain enrichment selectivity for ZEN.

[0064] After enriching 500 ppb of ZEN and AFB1 once using a 0.22 μm PA66 membrane, the PA66 membranes before and after enrichment of ZEN or AFB1 were characterized by SEM, XPS, and FT-IR. The results are shown in Figures 4 to 6.

[0065] Figure 4 The SEM images of PA66 membrane before and after enrichment of ZEN or AFB1, where (A) is the PA66 membrane before enrichment, (B) is the PA66 membrane after enrichment of ZEN, and (C) is the PA66 membrane after enrichment of AFB1. Figure 4 It can be seen that the morphology of (B) and (C) has not changed significantly compared with (A).

[0066] Figure 5 XPS graphs of PA66 membranes before and after enrichment with ZEN or AFB1, where (A), (D), and (G) are the C1s, O 1s, and N1s spectra of the PA66 membranes before enrichment, (B), (E), and (H) are the C1s, O1s, and N1s spectra of the PA66 membranes after enrichment with ZEN, and (C), (F), and (I) are the C1s, O 1s, and N1s spectra of the PA66 membranes after enrichment with AFB1. Figure 5 It can be seen that the C1s spectrum in (A) shows three peaks at 284.7eV, 285.3eV and 287.7eV of the PA66 membrane before enrichment, which are attributed to CC, CN and C=O respectively; as shown in (B), after enrichment of ZEN, an additional peak can be observed at 286.3eV, which is due to the formation of C-OH groups due to the hydrogen bonds between the PA66 membrane and the ZEN molecules; compared with (A), the C1s spectrum of the PA membrane after enrichment of AFB1 has not changed as shown in (C); in (D), the peaks at 531.0eV, 531.8eV and 533.3eV are respectively O =CN, O=CO (edge ​​carbonyl group of polyamide) and COH (edge ​​carboxyl group); in (E), the peak at 532.4 eV is attributed to O...HO, which indicates that hydrogen bonds are formed between the hydroxyl groups of ZEN and the amide groups of PA after the membrane is absorbed by ZEN molecules; due to the attraction of oxygen anions, the binding energy of O...HO in the edge carboxyl groups is lower than that of C-OH. In contrast, the XPS peak in (F) is the same as that in (B), which indicates that the chemical state of O does not change after AFB1 enrichment; in (G) to (I), there is no significant difference in the N1s spectra of PA66 membranes before and after enrichment with ZEN and AFB1.

[0067] Since ν(NH) vibration is very strong and very sensitive to the formation of hydrogen donor-acceptor complexes, Fourier transform infrared spectroscopy (FT-IR) is a powerful method to study hydrogen bonds involving NH groups. In order to further verify the formation of intermolecular hydrogen bonds between PA film and ZEN molecules, the changes of amide groups before and after enrichment were analyzed by Fourier transform infrared spectroscopy. The results are as follows Figure 6 shown.

[0068] Figure 6 FT-IR images of PA66 membrane before and after enrichment of ZEN or AFB1. Figure 6 1541cm is shown in -1 、1635cm -1 and 3295cm -1 The characteristic bands near the ZEN enrichment point correspond to amide band II, amide band I, and NH stretching vibration, respectively. Compared with the spectrum of PA66 film before enrichment (black line), the amide group at 1541 cm -1 、1635cm -1 and 3295cm -1 The absorption peak intensity of PA66 is reduced (red line), while the intensity difference of PA66 enriched AFB1 is almost negligible (blue line). These phenomena indicate that intermolecular hydrogen bonds are formed between the amide groups in the PA membrane and the hydroxyl groups in ZEN, which is consistent with the XPS results.

[0069] Density functional theory (DFT) calculations were used to further demonstrate the enrichment differences of ZEN and AFB1 on PA66 membranes. Figure 7 shown.

[0070] Figure 7 The optimized DFT calculation model of PA66 membrane and the enrichment model of ZEN and AFB1 on PA66 membrane, among which (A) is the optimized DFT calculation model of PA66 membrane, (B) is the enrichment model of ZEN on PA66 membrane, and (C) is the enrichment model of AFB1 on PA66 membrane. Figure 7 It can be seen that ZEN and AFB1 were introduced on the PA66 membrane and placed on the surface. (B) and (C) show the most stable optimized structures of ZEN and AFB1 on the PA66 membrane, and their corresponding adsorption energies (ΔE abs ) to evaluate the relative ease of enrichment. The calculation results show that when ZEN is on PA66 membrane, the adsorption energy is -0.45eV, as shown in (B). When AFB1 is arranged on PA, the adsorption energy is -0.13eV, as shown in (C). According to the results of DFT calculation, the adsorption energy follows ΔE abs (PA-ZEN)<ΔE absThis means that the PA membrane has a higher affinity for ZEN and is more suitable for adsorbing and enriching ZEN on its surface, which is very consistent with the research results.

[0071] Figure 8 Schematic diagram of the enrichment principle of ZEN and AFB1 by PA66 membrane.

[0072] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for extracting zearalenone from corn steep liquor to prepare a crude standard product, characterized in that the steps include: The corn steep liquor containing ZEN is centrifuged to obtain a supernatant; Treating the supernatant with a PA66 membrane to obtain a PA66 membrane enriched with ZEN; Eluting the PA66 membrane enriched with ZEN to obtain an eluate; Purifying the eluate by rotary evaporation to obtain a crude standard of ZEN; The pore size of the PA66 membrane is 0.22-0.45 μm; The eluent used in the elution is acetonitrile.

2. The method according to claim 1, characterized in that The centrifugal speed is 5000 rpm and the time is 5 minutes.

3. The method according to claim 1, characterized in that The method of using the PA66 membrane to treat the supernatant is as follows: using PA66 as a membrane, filtering the ZEN in the supernatant with PA66 for adsorption and enrichment.

4. The method according to claim 1, wherein The temperature of the rotary evaporation purification is 60° C. and the time is 10 min.

5. A method for removing ZEN from a ZEN-containing corn by-product, characterized in that the steps include: Centrifuging the ZEN-containing corn by-product for solid-liquid separation to obtain a solid portion and a supernatant; The supernatant is treated with a PA66 membrane to obtain a filtrate from which ZEN is removed; combining the filtrate and the solid portion to obtain a ZEN-removed corn by-product; The pore size of the PA66 membrane is 0.22-0.45 μm.

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