Low-molecular-weight araboxylan as well as preparation method and application thereof

Abstract

The invention provides low-molecular-weight araboxylan as well as a preparation method and application thereof, and belongs to the technical field of biological extraction and purification. The method comprises the following steps: by taking wheat bran as a raw material, pretreating, further fully exposing arabinoxylan in wheat bran by adopting an extrusion expansion coupling steam explosion technology, hydrolyzing by xylanase, decoloring, carrying out ion exchange refining treatment, and separating and purifying components by adopting a multi-stage membrane technology, so as to obtain the arabinoxylan. And finally, preparing araboxylan with different molecular weights. Through the process, on one hand, arabinoxylan with different molecular weights is obtained, the molecular composition is optimized, on the other hand, the content and purity of arabinoxylan with small molecular weight are further improved, and the adaptability of the product is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of biological extraction and purification, and specifically relates to a low molecular weight arabinoxylan and a preparation method and application thereof. Background Art

[0002] Bran is the main by-product of wheat processing, and my country has abundant bran resources. Bran has high nutritional value and is rich in dietary fiber and vitamins, but only a small part of it is used in the development of functional foods, and most of the rest is used as feed and sold at a relatively low price, wasting precious food resources.

[0003] Wheat bran is rich in nutrients, including protein, vitamins and minerals. In addition, it is also rich in high-quality dietary fiber, mainly arabinoxylan. For the human body, it has good physiological activity, and has the functions of promoting gastrointestinal motility, lowering blood sugar, inhibiting cholesterol increase, etc. It also has anti-cancer activity and can enhance the immunity of mice. Due to its oxidative cross-linking characteristics and high water holding capacity, it has a great influence on the characteristics of wheat flour dough and its products, and can effectively improve the quality of flour products and its unique physiological activity, making it a hot spot in market research.

[0004] At present, most studies on wheat bran use water extraction, acid-base extraction, enzymatic extraction and other methods. At the same time, most of them are comprehensive extraction of various dietary fibers contained in wheat bran, and there is no related research on direct extraction of low molecular weight arabinoxylans of various levels. Therefore, providing a method for extracting high-purity low molecular weight arabinoxylans of various levels in wheat bran is a technical problem that needs to be solved at this stage. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a low molecular weight arabinoxylan and a preparation method and application thereof, and to extract low molecular weight arabinoxylan with high purity and high yield by using extrusion puffing coupled with steam explosion technology combined with multi-stage membrane separation and purification, thereby achieving product upgrading and further expanding the application scope of arabinoxylan.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: The invention provides a preparation method of low molecular weight arabinoxylan, comprising the following steps: wheat bran pretreatment: wheat bran is mixed and soaked with water, neutral protease is added for reaction, and then alpha-amylase is added for reaction, enzyme is inactivated after reaction, filter and filter residue is collected, and dried to obtain pretreated wheat bran; extrusion puffing coupled with steam explosion: the pretreated wheat bran is extruded and puffed, and then steam explosion is adopted to collect materials sprayed by steam explosion; enzymolysis: the materials sprayed by steam explosion are mixed and reacted with xylanase to obtain enzymolysis materials; Refining treatment: decolorize the enzymatic material to obtain syrup, and then perform ion exchange on the syrup to obtain refined liquid; multi-stage membrane separation system separation and purification: pass the refined liquid through the ceramic membrane to obtain <1×10 6 Da feed solution and 1×10 6 -6×10 6 Da feed solution, then <1×10 6 The Da feed solution is first passed through an ultrafiltration membrane to remove small molecules, and finally the feed solution that has removed small molecules is passed through an ultrafiltration membrane for the second time to obtain 1×10 4 -4×10 4 Da and 1×10 5 -4×10 5 Feed liquid.

[0007] Preferably, the conditions for the neutral protease addition reaction include: pH 6.3-6.7, temperature 48-52°C, time 22-26h, and the amount of neutral protease added is 340-360mL / T.DS.

[0008] Preferably, the conditions for the reaction of adding α-amylase include: temperature of 95-115° C., reaction time of 15-25 min, and amount of α-amylase added of 240-260 mL / T.DS.

[0009] Preferably, the extrusion puffing conditions include: temperature of 40-70°C, time of 0.5-4h, and screw speed of 70-90rpm.

[0010] Preferably, the steam explosion treatment step comprises: introducing high-temperature saturated steam into the extrusion-expanded liquid to raise the pressure to 1.0-3.0 MPa and then maintaining the pressure for 5-30 seconds, and after the pressure maintenance is completed, opening the pneumatic valve to instantly release the pressure to complete the explosion of the material.

[0011] Preferably, the material sprayed out by steam explosion needs to be diluted with water to 10-40%, and the pH is adjusted to 3-7; the amount of xylanase added is 4-6 kg / T.DS; the temperature of the mixed reaction is 50-70°C and the time is 22-26 hours.

[0012] Preferably, the conditions for decolorization of the enzymatic material include: passing through a granular activated carbon column at a flow rate of 1.5-2.5 BV / h and a temperature of 45-55°C; the conditions for ion exchange of the syrup include: passing through a cation exchange column-a first anion exchange column-a second anion exchange column in sequence at a flow rate of 2-4 BV / h and a temperature of 35-55°C.

[0013] Preferably, the specification of the ceramic membrane is 190-210nm, the specification of the first ultrafiltration membrane is 900-1100Da, and the specification of the second ultrafiltration membrane is 45-55KDa; the temperature of the ceramic membrane or the ultrafiltration membrane is 30-50°C and the pressure is 0-0.1MPa.

[0014] The present invention provides low molecular weight arabinoxylan obtained by the preparation method, wherein the low molecular weight arabinoxylan is divided into 1×10 6 -6×10 6 Da arabinoxylan, 1×10 5 -4×10 5 Da arabinoxylan and 1×10 4 -4×10 4 Da arabinoxylan.

[0015] The present invention provides low molecular weight arabinoxylan obtained by the preparation method or application of the low molecular weight arabinoxylan in preparing food or medicine.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing low molecular weight arabinoxylan, which adopts extrusion puffing coupled steam explosion technology combined with multi-stage membrane separation and purification to extract low molecular weight arabinoxylan of various levels with high purity and high yield, thereby realizing product upgrading and further expanding the application scope of arabinoxylan.

[0017] Furthermore, the present invention adopts extrusion puffing treatment to wheat bran, thereby opening the action site of subsequent treatment. The steam explosion treatment not only exposes the arabinoxylan in the wheat bran more fully, but also degrades the macromolecules to generate small molecules, which is beneficial to the further action of the subsequent xylanase. Thus, the yield of arabinoxylan is increased by 5-10%, and the reaction time is shortened by 10 hours. Furthermore, multi-stage membrane separation technology is adopted to remove small molecules in the feed liquid, thereby improving the purity of arabinoxylan.

[0018] Furthermore, the arabinoxylan prepared by the present invention has a small molecular weight and can be added to pasta to increase the specific volume of steamed bread, improve the appearance, elasticity and structure of pasta, increase the smoothness of the surface, and make its structure more delicate and elastic.

[0019] Furthermore, the entire preparation process of the present invention does not require the addition of organic solvents such as ethanol. Compared with methods of extracting arabinoxylan using water extraction and alcohol precipitation, the present invention has less environmental pollution and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a flow chart for the preparation of low molecular weight arabinoxylan. DETAILED DESCRIPTION

[0021] The invention provides a preparation method of low molecular weight arabinoxylan, comprising the following steps: (1) pretreatment of wheat bran: wheat bran is mixed and soaked with water, neutral protease is added for reaction, and then alpha-amylase is added for reaction, and after the reaction, the enzyme is inactivated, and the residue is filtered and dried to obtain pretreated wheat bran; (2) extrusion puffing coupled with steam explosion: the pretreated wheat bran is extruded and puffed, and then steam explosion is performed, and the material sprayed by the steam explosion is collected; (3) enzymolysis: the material sprayed by the steam explosion is mixed with xylanase for reaction to obtain enzymolysis material; (4) refining treatment: the enzymolysis material is decolorized to obtain syrup, and then the syrup is ion-exchanged to obtain refined liquid; (5) separation and purification by a multi-stage membrane separation system: the refined liquid is passed through a ceramic membrane to obtain <1×10 6 Da feed solution and 1×10 6 -6×10 6 Da feed solution, then <1×10 6 The Da feed solution is first passed through an ultrafiltration membrane to remove small molecules, and finally the feed solution that has removed small molecules is passed through an ultrafiltration membrane for the second time to obtain 1×10 4 -4×10 4 Da and 1×10 5 -4×10 5 The wheat bran of the present invention needs to be crushed and sieved before soaking, and the wheat bran sieved with 100-200 meshes is selected.

[0022] In the present invention, the conditions for adding neutral protease reaction include: pH 6.3-6.7, temperature 48-52°C, time 22-26h, and the amount of neutral protease added is 340-360mL / T.DS (340-360mL enzyme solution is added per ton of dry substrate); preferably, the conditions for adding neutral protease reaction include: pH 6.5, temperature 50°C, time 24h, and the amount of neutral protease added is 350mL / T.DS. The conditions for adding α-amylase reaction in the present invention include: temperature 95-115°C, time 15-25min, and the amount of α-amylase added is 240-260mL / T.DS (240-260mL enzyme solution is added per ton of dry substrate); preferably, the conditions for adding α-amylase reaction include: temperature 105°C, time 20min, and the amount of α-amylase added is 250mL / T.DS. The purpose of adding neutral protease in the present invention is to remove protein from the wheat bran material, and the purpose of adding α-amylase is to remove starch from the wheat bran. In the present invention, the temperature of the extrusion puffing is 40-70°C, preferably 45-65°C, and more preferably 50°C; the time of the extrusion puffing is 0.5-4h, preferably 1-3h, and more preferably 2h; the screw speed of the extrusion puffing is 70-90rpm, preferably 75-85rpm, and more preferably 80rpm. The extrusion puffing treatment of the present invention opens the action site of subsequent treatment in the wheat bran.

[0023] In the present invention, the step of steam explosion treatment comprises: introducing high-temperature saturated steam into the extrusion puffing treatment liquid, raising the pressure to 1.0-3.0MPa and maintaining the pressure for 5-30s, opening the pneumatic valve after the pressure maintenance is completed, and instantly releasing the pressure to complete the explosion of the material. The pressure of the steam explosion treatment of the present invention is preferably increased to 1.5-2.5MPa, and more preferably 2MPa. The time of maintaining the pressure of the present invention is preferably 10-25s, and more preferably 20s. The steam explosion treatment of the present invention exposes the arabinoxylan in the wheat bran more fully, degrades the macromolecules, and generates small molecules, which is conducive to the further action of the subsequent xylanase.

[0024] In the present invention, the steam explosion sprayed material needs to be diluted with water to 10-40wt%, preferably 20-38wt%, and more preferably 35wt%; the pH is adjusted to 5.8-6.2, preferably pH is adjusted to 6.0. The amount of xylanase added in the present invention is 4-6kg / T.DS (4-6kg enzyme powder is added per ton of dry substrate), preferably 5kg / T.DS; the temperature of the steam explosion sprayed material and xylanase mixed reaction is 50-70°C, preferably 60°C, and the time is 22-26h, preferably 24h.

[0025] In the present invention, the conditions for decolorization of the enzymatic material include: passing through a granular activated carbon column, a flow rate of 1.5-2.5BV / h, preferably 2.0BV / h, and a temperature of 45-55°C, preferably 50°C; the conditions for ion exchange of the syrup include: passing through a cation exchange column-a first anion exchange column-a second anion exchange column in sequence, a flow rate of 2-4BV / h, preferably 3BV / h, and a temperature of 35-55°C, preferably 50°C. The cation exchange column of the present invention is a strong acid cation resin 001FD, the first anion exchange column is a weak base anion resin 301P FD, and the second anion exchange column is a strong base anion resin 202FD. The purpose of passing the enzymatic material through a granular activated carbon column in the present invention is decolorization. The purpose of passing the decolorized syrup through an ion exchange column in the present invention is desalination.

[0026] In the present invention, the specification of the ceramic membrane is 190-210nm, preferably 200nm, the specification of the first ultrafiltration membrane is 900-1100Da, preferably 1000Da, and the specification of the second ultrafiltration membrane is 45-55KDa, preferably 50KDa. The temperature of the ceramic membrane or ultrafiltration membrane of the present invention is 30-50°C and the pressure is 0-0.1MPa, preferably the temperature is 32-45°C and the pressure is 0.02-0.05MPa, and more preferably the temperature is 35°C and the pressure is 0.04MPa. The purpose of the ceramic membrane filtration of the present invention is to obtain <1×10 6 Da feed liquid and (1-6)×10 6 Feed liquid, <1×10 6 The feed solution is used for subsequent ultrafiltration membrane filtration, (1-6)×10 6 The feed liquid contains (1-6)×10 6 Da arabinoxylan feed liquid; the purpose of the first ultrafiltration membrane filtration is to remove <1×10 6 The purpose of the second ultrafiltration membrane filtration is to remove 1×10 5 -4×10 5 Da arabinoxylan and 1×10 4 -4×10 4 Da arabinoxylan.

[0027] The present invention also provides low molecular weight arabinoxylan obtained by the preparation method, wherein the low molecular weight arabinoxylan is divided into 1×10 6 -6×10 6 Da arabinoxylan, 1×10 5 -4×10 5 Da arabinoxylan and 1×10 4 -4×104 Da arabinoxylan.

[0028] The present invention also provides the low molecular weight arabinoxylan obtained by the preparation method or the use of the low molecular weight arabinoxylan in preparing food or medicine. The food of the present invention includes but is not limited to pasta. The medicine of the present invention includes but is not limited to hypoglycemic drugs, immunity enhancing drugs, and gastrointestinal regulating drugs.

[0029] In the present invention, unless otherwise specified, all components or reagents are commercially available products well known to those skilled in the art.

[0030] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The following examples involve a method for determining the molecular weight of WBAXs: the molecular weight of the polysaccharide is determined by high-performance size exclusion chromatography, and different molecular weight dextran standards are sampled and analyzed, and the molecular weight standard curve is automatically drawn by the GPC software. The prepared material is formulated into a solution with an arabinoxylan content of 0.01 g / mL, filtered through a 0.45 μm microfiltration membrane, and then sampled, and the results are processed and analyzed using the GPC software. Among them, the chromatographic column: 2 Waters UltrahydrogelTM Linear in series (7.8 mm×300 mm); the detector: a differential refractive index detector; the mobile phase: 0.1 mol / L NaAc solution; the flow rate: 0.9 mL / min; the column temperature: 45°C.

[0032] Example 1 (1) Pretreatment of wheat bran raw materials: After the wheat bran is crushed, it is sieved and the bran sieved with 100-200 mesh is selected and soaked in pure water for 2 h. After the soaking, the pH is adjusted to 6.5 and the temperature is 50°C. 350 mL / T.DS (350 mL enzyme solution is added for every 1 ton of dry substrate) neutral protease (Novozymes (China) Biotechnology Co., Ltd., 2.4 AU / g, nominal activity of about 240,000-270,000 U / g) is added and reacted for 24 h to obtain the material; 250 mL / T.DS high temperature resistant α-amylase (Shandong Longda Bioengineering Co., Ltd., 20,000 U / ml) is added to the material and reacted at 105°C for 20 min. After the reaction, the enzyme is inactivated in a boiling water bath. After filtration, the residue is washed and dried to obtain the de-starch and de-proteinized wheat bran.

[0033] (2) Extrusion puffing coupled with steam explosion: The de-starch and de-proteinized wheat bran was extruded for 2 h at an extrusion puffing temperature of 50 °C and a screw speed of 80 rpm. The extruded wheat bran was added to the steam explosion cylinder, and high-temperature saturated steam was introduced to raise the pressure of the explosion cylinder to 1.50 MPa and then maintain the pressure for 20 s. After the pressure maintenance, the pneumatic valve was opened, and the pressure was released instantly to complete the explosion of the material, and the material ejected by the steam explosion was collected. The molecular weight distribution of the material was detected by the WBAXs molecular weight determination method. The results are shown in Table 1.

[0034] Table 1 Molecular weight distribution of each component of the material ejected by steam explosion

[0035] (3) Xylan hydrolysis: The steam explosion material was diluted with water to 35 wt%, the pH was adjusted to 6.0, and xylanase (Kandien Biotechnology Co., Ltd., 100,000 U / g) was added according to 5 kg / T.DS (5 kg enzyme powder per 1 ton of dry substrate), and the reaction was carried out at 60°C for 24 h to obtain the enzymatic hydrolysis material. The molecular weight distribution of the enzymatic hydrolysis material was detected by the WBAXs molecular weight determination method. The results are shown in Table 2.

[0036] Table 2 Molecular weight distribution of each component of enzymatic hydrolysis material

[0037] (4) Refining treatment: The enzymatic hydrolyzed material is decolorized by passing through a granular activated carbon column at a flow rate of 2 BV / h at 50°C to obtain a syrup; then the syrup is sequentially passed through a cation exchange column (strong acid cation resin 001FD) - anion exchange column (weak base anion resin 301P FD) - anion exchange column (strong base anion resin 202FD) at a flow rate of 3 BV / h at 40°C to obtain a refined liquid.

[0038] (5) Separation and purification by multi-stage membrane separation system: The refined liquid enters a 200 nm ceramic membrane at a temperature of 35 °C and a pressure of 0.04 MPa, collecting <1×10 6 Da feed liquid and (1-6)×10 6 Da arabinoxylan liquid, and then <1×10 6 The Da feed liquid was passed through a 1000Da ultrafiltration membrane to remove small molecules such as rhamnose, arabinose, galactose, glucose, and xylose. Finally, the feed liquid after removing small molecules was passed through a 50KDa ultrafiltration membrane for separation and purification at a temperature of 35°C and a pressure of 0.04MPa to obtain (1-4)×10 4 Da feed liquid and (1-4)×10 5 The feed liquid, of which the liquid outside the membrane is (1-4)×10 4 Da arabinoxylan liquid, the liquid flowing out of the membrane is (1-4)×10 5Da arabinoxylan feed solution. The purity of each molecular weight feed solution was detected by WBAXs molecular weight determination method. The yield of arabinoxylan in each molecular weight feed solution prepared was calculated based on the content of arabinoxylan at each molecular weight in the refined feed solution obtained in step (4). The calculation formula is: yield = arabinoxylan content in each molecular weight feed solution / corresponding arabinoxylan content at each molecular weight in the refined feed solution × 100%. The results are shown in Table 3.

[0039] Table 3 Purity and yield of arabinoxylan in various molecular weight solutions

[0040] Example 2 (1) Pretreatment of wheat bran raw materials: After the wheat bran is crushed, it is sieved and the bran sieved with 100-200 mesh is selected and soaked in pure water for 2 h. After the soaking, the pH is adjusted to 6.3 and the temperature is 48°C. 30 mL / T.DS neutral protease (Novozymes (China) Biotechnology Co., Ltd., 2.4 AU / g, nominal activity of about 240,000-270,000 U / g) is added and reacted for 22 h to obtain the material; 240 mL / T.DS high temperature resistant α-amylase (Shandong Longda Bioengineering Co., Ltd., 20,000 U / ml) is added to the material and reacted at 95°C for 15 min. After the reaction, the enzyme is inactivated in a boiling water bath. After filtration, the residue is washed and dried to obtain the de-starch and de-proteinized wheat bran.

[0041] (2) Extrusion puffing coupled with steam explosion: The de-starch and de-proteinized wheat bran was extruded at an extrusion puffing temperature of 40°C and a screw speed of 70 rpm for 1 h: the extruded wheat bran was added to the steam explosion cylinder, and high-temperature saturated steam was introduced to raise the pressure of the explosion cylinder to 1.0 MPa and then maintain the pressure for 10 seconds. After the pressure maintenance, the pneumatic valve was opened, and the pressure was released instantly to complete the explosion of the material, and the material ejected by the steam explosion was collected. The molecular weight distribution of the material was detected by the WBAXs molecular weight determination method. The results are shown in Table 4.

[0042] Table 4 Molecular weight distribution of each component of the material ejected by steam explosion

[0043] (3) Xylan hydrolysis: The steam explosion material was diluted with water to 25%, the pH was adjusted to 5.0, and xylanase (Kandien Biotechnology Co., Ltd., 100,000 U / g) was added at 4 kg / T.DS. The reaction was continued for 22 h to obtain the enzymatic hydrolysis material. The molecular weight distribution of the enzymatic hydrolysis material was detected by the WBAXs molecular weight determination method. The results are shown in Table 5.

[0044] Table 5 Molecular weight distribution of each component of enzymatic hydrolysis material

[0045] (4) Refining treatment: The enzymatic hydrolyzed material is decolorized by passing through a granular activated carbon column at a flow rate of 1.5 BV / h at 45°C to obtain a syrup; then the syrup is sequentially passed through a cation exchange column (strong acid cation resin 001FD) - anion exchange column (weak base anion resin 301P FD) - anion exchange column (strong base anion resin 202FD) at a flow rate of 2 BV / h at 35°C to obtain a refined liquid.

[0046] (5) Separation and purification by multi-stage membrane separation system: the refined liquid enters the 200nm ceramic membrane at a temperature of 30°C and a pressure of 0.03MPa, and collects <1×10 6 Da feed liquid and (1-6)×10 6 Da arabinoxylan liquid, and then <1×10 6 The feed solution was passed through a 1000Da ultrafiltration membrane to remove small molecules such as rhamnose, arabinose, galactose, glucose, and xylose, and finally passed through a 50KDa ultrafiltration membrane for separation at a temperature of 30°C and a pressure of 0.03MPa to obtain (1-4)×10 4 Da feed liquid and (1-4)×10 5 The feed liquid, of which the liquid outside the membrane is (1-4)×10 4 Da arabinoxylan liquid, the liquid flowing out of the membrane is (1-4)×10 5 Da arabinoxylan feed solution. The purity and yield of each molecular weight feed solution were tested in the same manner as in Example 1. The results are shown in Table 6.

[0047] Table 6 Purity and yield of arabinoxylan in various molecular weight solutions

[0048] Example 3 (1) Pretreatment of wheat bran raw materials: After the wheat bran is crushed, it is sieved and the bran sieved with 100-200 mesh is selected and soaked in pure water for 2 h. After the soaking, the pH is adjusted to 6.7 and the temperature is 52°C. 360 mL / T.DS neutral protease (Novozymes (China) Biotechnology Co., Ltd., 2.4 AU / g, nominal activity of about 240,000-270,000 U / g) is added and reacted for 26 h to obtain the material; 260 mL / T.DS high temperature resistant α-amylase (Shandong Longda Bioengineering Co., Ltd., 20,000 U / ml) is added to the material and reacted at 115°C for 25 min. After the reaction, the enzyme is inactivated in a boiling water bath. After filtration, the residue is washed and dried to obtain the de-starch and de-proteinized wheat bran.

[0049] (2) Extrusion puffing coupled with steam explosion: The de-starch and de-proteinized wheat bran was extruded for 4 h at an extrusion puffing temperature of 70 °C and a screw speed of 90 rpm. The extruded wheat bran was added to the steam explosion cylinder, and high-temperature saturated steam was introduced to raise the pressure of the explosion cylinder to 3.0 MPa and then maintain the pressure for 30 seconds. After the pressure maintenance, the pneumatic valve was opened, and the pressure was released instantly to complete the explosion of the material, and the material ejected by the steam explosion was collected. The molecular weight distribution of the material was detected by the WBAXs molecular weight determination method. The results are shown in Table 7.

[0050] Table 7 Molecular weight distribution of each component of the material ejected by steam explosion

[0051] (3) Xylan hydrolysis: The steam explosion material was diluted with water to 40%, the pH was adjusted to 7.0, and xylanase (Kandien Biotechnology Co., Ltd., 100,000 U / g) was added at 6 kg / T.DS. The reaction was continued for 26 h to obtain the hydrolyzed material. The molecular weight distribution of the hydrolyzed material was detected by the WBAXs molecular weight determination method. The results are shown in Table 8.

[0052] Table 8 Molecular weight distribution of each component of enzymatic hydrolysis material

[0053] (4) Refining treatment: The enzymatic hydrolyzed material is decolorized by passing through a granular activated carbon column at a flow rate of 2.5 BV / h at 55°C to obtain a syrup; then the syrup is sequentially passed through a cation exchange column (strong acid cation resin 001FD) - anion exchange column (weak base anion resin 301P FD) - anion exchange column (strong base anion resin 202FD) at a flow rate of 4 BV / h at 55°C to obtain a refined liquid.

[0054] (5) Separation and purification by multi-stage membrane separation system: the refined liquid enters the 200nm ceramic membrane at a temperature of 50°C and a pressure of 0.1MPa, and collects <1×10 6 Da feed liquid and (1-6)×10 6 Da arabinoxylan liquid, and then <1×10 6 The feed solution was passed through a 1000Da ultrafiltration membrane to remove small molecules such as rhamnose, arabinose, galactose, glucose, and xylose, and finally passed through a 50KDa ultrafiltration membrane for separation and purification at a temperature of 50°C and a pressure of 0.1MPa to obtain (1-4)×10 4 Da feed liquid and (1-4)×10 5 The feed liquid, of which the liquid outside the membrane is (1-4)×10 4 Da arabinoxylan liquid, the liquid flowing out of the membrane is (1-4)×10 5Da arabinoxylan feed solution. The purity and yield of each molecular weight feed solution were tested using the same method as in Example 1. The results are shown in Table 9.

[0055] Table 9 Purity and yield of arabinoxylan in various molecular weight solutions

[0056] Comparative Example 1 Compared with Example 1, the extrusion and puffing step was removed, and the remaining steps were the same as those in Example 1. The molecular weight distribution of the enzymatic hydrolyzed material was detected by the WBAXs molecular weight determination method. The results are shown in Table 10. Compared with Example 1, it was found that (1-4)×10 4 The content of Da arabinoxylan was significantly lower, indicating that extrusion can affect the distribution of small molecular weight arabinoxylan.

[0057] Table 10 Molecular weight distribution of each component of enzymatic hydrolysis material

[0058] Comparative Example 2 Compared with Example 1, the steam explosion treatment step was removed, and the remaining steps were the same as those in Example 1. The molecular weight distribution of the enzymatic hydrolyzed material was detected by the WBAXs molecular weight determination method. The results are shown in Table 11. Compared with Example 1, it was found that (1-4)×10 4 The content of Da arabinoxylan was significantly reduced, and the results showed that steam explosion could further act on macromolecules and reduce their content, thus providing conditions for subsequent separation and purification.

[0059] Table 11 Molecular weight distribution of each component of enzymatic hydrolysis material

[0060] Comparative Example 3 Compared with Example 1, in step (5) of separation and purification by multi-stage membrane separation system, only 50KDa ultrafiltration membrane is used for separation and purification, and the small molecule transparent liquid is obtained. 4 Da and concentrate ≥ (1-4) × 10 4 Da, the remaining steps are the same as in Example 1. The WBAXs molecular weight determination method is used to detect ≤ (1-4) × 10 4 Da small molecule transparent liquid and ≥ (1-4) × 10 4The purity of arabinoxylan in Da concentrate was determined by the same method as in Example 1. The results are shown in Tables 12-13. Compared with Example 1, the purity of arabinoxylan in each molecular weight in the feed solution was reduced. The results show that selecting a suitable specification of filter membrane in multi-stage membrane separation technology is helpful to improve the purity and yield of arabinoxylan products of each molecular weight, and is more suitable for producing products of different molecular weights.

[0061] Table 12 ≤ (1-4) × 10 4 Molecular weight distribution of each component in Da small molecule transparent liquid

[0062] Table 13 ≥ (1-4) × 10 4 Molecular weight distribution of each component in Da concentrate

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing low molecular weight arabinoxylan, characterized in that: The steps include: Wheat bran pretreatment: Wheat bran is mixed with water and soaked, neutral protease is added for reaction, and then α-amylase is added for reaction, enzyme is inactivated after the reaction is completed, and the residue is filtered and dried to obtain pretreated wheat bran; Extrusion puffing coupled with steam explosion: the pretreated wheat bran is extruded and puffed, then steam exploded, and the steam explosion ejected material is collected; Enzymatic hydrolysis: the material sprayed out by steam explosion is mixed with xylanase to react and obtain enzymatic hydrolysis material; Refining treatment: decolorizing the enzymatically hydrolyzed material to obtain syrup, and then subjecting the syrup to ion exchange to obtain refined liquid; Multi-stage membrane separation system separation and purification: the refined liquid passes through the ceramic membrane to obtain <1×10 6 Da feed solution and 1×10 6 -6×10 6 Da feed solution, then <1×10 6 The Da feed solution is first passed through an ultrafiltration membrane to remove small molecules, and finally the feed solution that has removed small molecules is passed through an ultrafiltration membrane for the second time to obtain 1×10 4 -4×10 4 Da and 1×10 5 -4×10 5 Feed liquid.

2. The preparation method according to claim 1, characterized in that The conditions for the neutral protease addition reaction include: pH 6.3-6.7, temperature 48-52° C., time 22-26 hours, and the amount of neutral protease added is 340-360 mL / T.DS.

3. The preparation method according to claim 1, characterized in that: The conditions for the reaction of adding α-amylase include: temperature of 95-115° C., reaction time of 15-25 min, and addition amount of α-amylase of 240-260 mL / T.DS.

4. The preparation method according to claim 1, characterized in that: The extrusion puffing conditions include: temperature of 40-70° C., time of 0.5-4 h, and screw speed of 70-90 rpm.

5. The preparation method according to claim 1, characterized in that: The steam explosion treatment comprises: introducing high-temperature saturated steam into the extrusion-expanded liquid material to raise the pressure to 1.0-3.0 MPa and then maintaining the pressure for 5-30 seconds; after the pressure maintenance is completed, the pneumatic valve is opened to release the pressure instantly to complete the explosion of the material.

6. The preparation method according to claim 1, characterized in that: The material sprayed out by steam explosion needs to be diluted with water to 10-40%, and the pH is adjusted to 3-7; the amount of xylanase added is 4-6kg / T.DS; the temperature of the mixed reaction is 50-70°C and the time is 22-26h.

7. The preparation method according to claim 1, characterized in that: The conditions for decolorization of the enzymatic material include: passing through a granular activated carbon column at a flow rate of 1.5-2.5 BV / h and a temperature of 45-55°C; the conditions for ion exchange of the syrup include: passing through a cation exchange column-a first anion exchange column-a second anion exchange column in sequence at a flow rate of 2-4 BV / h and a temperature of 35-55°C.

8. The preparation method according to claim 1, characterized in that: The specification of the ceramic membrane is 190-210nm, the specification of the first ultrafiltration membrane is 900-1100Da, and the specification of the second ultrafiltration membrane is 45-55KDa; the temperature of the ceramic membrane or the ultrafiltration membrane is 30-50°C and the pressure is 0-0.1MPa.

9. The low molecular weight arabinoxylan obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The low molecular weight arabinoxylan is divided into 1×10 6 -6×10 6 Da arabinoxylan, 1×10 5 -4×10 5 Da arabinoxylan and 1×10 4 -4×10 4 Da arabinoxylan.

10. Use of the low molecular weight arabinoxylan obtained by the preparation method according to any one of claims 1 to 8 or the low molecular weight arabinoxylan according to claim 9 in the preparation of food or medicine.

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