Process for preparing corn bran xylan through combination of high-temperature cooking and ball milling and compound enzyme method

Abstract

The invention discloses a process for preparing corn bran xylan through combination of high-temperature cooking and ball milling and a compound enzyme method, and relates to the technical field of corn bran xylan preparation, and the process comprises the following steps: step 1, corn bran raw material pretreatment: selecting corn bran without mildew and impurities, washing the corn bran with clear water for 3-5 times, removing dust, soil and soluble impurities attached to the surface, and drying the corn bran; then putting the washed corn bran into a hot air drying box, drying for 4-6 hours at the temperature of 60-80 DEG C, crushing by a crusher after drying, and sieving by a 40-60-mesh sieve to obtain corn bran powder; step 2, high-temperature cooking treatment: uniformly mixing the corn bran powder obtained in the step 1 with deionized water according to a material-liquid ratio of (1: 8)-(1: 12) (w / v), and injecting the mixture into high-temperature cooking equipment; the method has the advantages of being high in xylan conversion rate, high in product purity, environmentally friendly, simple in process, low in cost and the like, industrial production is easy, the corn bran resource utilization rate can be effectively increased, and the technical level of the corn deep processing industry is improved.

Description

Technical Field

[0001] This invention relates to the field of corn husk xylan preparation technology, and in particular to a process for preparing corn husk xylan using a combination of high-temperature cooking, ball milling, and compound enzymatic methods. Background Technology

[0002] Corn is the most widely produced grain crop in my country, accounting for nearly 40% of the total annual grain output, and plays a crucial role in ensuring national food security. Corn husks, a major byproduct of corn starch production, account for 10%-14% (w / w) of corn weight, with an annual output of nearly 30 million tons and abundant reserves. The main components of corn husks are hemicellulose (30-45%), cellulose, lignin, starch, and protein. Arabinoxylan is the main component of hemicellulose, accounting for approximately 25%-30% of the dry weight of corn husks.

[0003] However, the utilization rate of corn husks as a resource is currently low, with most being used only for feed production. This has resulted in the underdevelopment of this abundant biomass resource and its low added value. Arabicaxylan possesses various beneficial effects, including health benefits, antioxidant properties, ability to help lower blood sugar, and enhanced immunity. It has been approved by several countries as a raw material for health foods or as dietary fiber added to foods and dietary supplements, showing broad market application prospects. In 2022, my country issued a public consultation notice regarding arabinoxylan (derived from sugarcane bagasse, barley bran, and corn husks) as a new food ingredient. In 2024, arabinoxylan derived from sugarcane bagasse and barley bran was approved, while arabinoxylan derived from corn husks is still under approval. Its development and utilization have significant practical implications.

[0004] Existing technologies for preparing xylan from corn husks have several shortcomings. For example, single pretreatment methods do not sufficiently disrupt the dense structure of corn husks, leading to low enzymatic hydrolysis efficiency and low xylan conversion rates. Inappropriate enzyme selection and lack of targeted formulation of compound enzymes also hinder efficient xylan release. Furthermore, unscientific process parameter settings result in low product purity, high energy consumption, and high production costs, making industrial-scale production difficult. Therefore, developing a corn husk xylan preparation process that offers good pretreatment effects, high enzymatic hydrolysis efficiency, high product purity, simple operation, and low energy consumption is of great significance for improving the utilization rate of corn husk resources and enhancing the technological level of the corn deep processing industry. Summary of the Invention

[0005] This invention discloses a process for preparing corn husk xylan by high-temperature cooking, ball milling, and a compound enzymatic method. By using a combination of high-temperature cooking and ball milling pretreatment, compared with a single pretreatment method, the dense structure of corn husk can be more fully destroyed, significantly increasing the exposure of xylan, creating favorable conditions for subsequent enzymatic hydrolysis, and greatly improving the xylan conversion rate.

[0006] Its compound enzyme preparation is composed of xylanase CsXyn10B, CsXyn11A, arabinosidase and ferulic acid esterase in a specific ratio. Each enzyme component works synergistically, is highly targeted, has high enzymatic hydrolysis efficiency, can effectively reduce the amount of enzyme preparation used, and save production costs.

[0007] Its process parameters have been optimized and designed. The parameters of each step from raw material pretreatment to product drying are scientific and reasonable, and the operation is highly controllable. It can effectively ensure the stability of product quality and avoid problems such as inconsistent product purity caused by parameter fluctuations.

[0008] The entire process does not require the use of toxic or harmful chemical reagents. It adopts a combination of physical pretreatment and biological enzymatic hydrolysis, which is green and environmentally friendly, with no pollutant emissions, meets the requirements of sustainable development, and the product is highly safe.

[0009] Its process is simple, requires conventional equipment, has low energy consumption, low production cost, high xylan conversion rate and product purity, and is easy to scale up for industrial production. It has good economic and social benefits. In summary, it solves the problems in the background technology.

[0010] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0011] The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method of the present invention includes the following steps:

[0012] Step 1, corn husk raw material pretreatment: Select corn husks that are free from mold and impurities, rinse them with clean water 3-5 times to remove dust, dirt and soluble impurities attached to the surface, and then place the rinsed corn husks in a hot air drying oven and dry them at 60-80℃ for 4-6 hours. After drying, pulverize them through a pulverizer and pass them through a 40-60 mesh sieve to obtain corn husk powder.

[0013] Step 2, High-temperature cooking treatment: Mix the corn husk powder obtained in Step 1 with deionized water at a material-to-liquid ratio of 1:8-1:12 (w / v), inject the mixture into a high-temperature cooking device, turn off the device and purge the internal air with nitrogen. After the purge is complete, raise the temperature to 120-140℃ and maintain this temperature and pressure of 0.15-0.25MPa for cooking for 30-60 minutes. After cooking, allow the mixture to cool naturally to room temperature to obtain the cooked corn husk slurry.

[0014] Step 3, ball milling: Transfer the corn husk slurry obtained in Step 2 to a ball mill, add zirconia balls, and the ball-to-material ratio is 10:1-15:1 (w / w). Adjust the ball mill speed to 200-300 r / min and ball mill for 60-120 minutes. During the ball milling process, stop the machine for 5 minutes every 20-30 minutes to prevent the equipment from overheating. After the ball milling is completed, a refined corn husk slurry is obtained.

[0015] Step 4, compound enzymatic hydrolysis treatment: Adjust the pH of the corn husk slurry obtained in Step 3 to 4.5-5.5, and then add a compound enzyme preparation. The amount of compound enzyme preparation added is 0.5%-1.5% (w / w) of the dry weight of the corn husk powder. The compound enzyme preparation is composed of xylanase CsXyn10B, xylanase CsXyn11A, arabinosidase and ferulic acid esterase mixed in a mass ratio of 3:3:2:2. Enzymatic hydrolysis is carried out at a temperature of 50-60℃ and a stirring speed of 150-200r / min for 12-24 hours to obtain the enzymatic hydrolysate.

[0016] Step 5, post-treatment of the enzymatic hydrolysate: Place the enzymatic hydrolysate obtained in Step 4 in a water bath at 85-95℃ for 15-20 minutes to inactivate the enzyme. After inactivation, cool the hydrolysate to room temperature and then centrifuge at 8000-10000 r / min for 20-30 minutes. Collect the supernatant and ultrafilter it through an ultrafiltration membrane with a molecular weight cutoff of 5000-10000 Da. Collect the retentate and vacuum concentrate it to 1 / 3-1 / 2 of its original volume under vacuum conditions of 0.06-0.08 MPa and 50-60℃. After concentration, add 3-5 times the volume of anhydrous ethanol, stir evenly, and let it stand to precipitate for 12-24 hours. Then filter and collect the precipitate. Place the precipitate in a vacuum drying oven and dry it at 45-55℃ for 8-12 hours to obtain the corn husk xylan product.

[0017] Furthermore, in step 1, the wind speed of the hot air drying box is set to 1-2 m / s to ensure that the corn husks are heated evenly during the drying process and to avoid local overheating that could damage the nutrients.

[0018] Furthermore, in step 2, the nitrogen purging time is 5-10 minutes, and the nitrogen flow rate is maintained at 0.5-1L / min during the purging process to ensure that the air inside the equipment is completely discharged and to prevent the corn husks from undergoing an oxidation reaction during the high-temperature cooking process.

[0019] Furthermore, in step 3, the zirconia balls have a particle size of 0.5-1.5 mm, and an intermittent ball milling method is adopted during the ball milling process. The ball milling environment temperature is maintained within the range of 30-40℃ by periodically stopping the machine to dissipate heat.

[0020] Furthermore, in step 4, the pH value of the corn husk slurry is adjusted using a citrate-sodium citrate buffer solution with a concentration of 0.05-0.1 mol / L. During the adjustment process, the buffer solution is added while stirring at a speed of 100-150 r / min to ensure that the pH value is uniform and stable.

[0021] Furthermore, in step 4, the enzyme activity of xylanase CsXyn10B is 10000-15000 U / g, the enzyme activity of xylanase CsXyn11A is 12000-18000 U / g, the enzyme activity of arabinosidase is 8000-12000 U / g, and the enzyme activity of ferulic acid esterase is 5000-8000 U / g.

[0022] Furthermore, in step 5, the operating pressure of the ultrafiltration treatment is 0.2-0.3 MPa, and the ultrafiltration membrane is cleaned every 30-60 minutes during the ultrafiltration process by backwashing with deionized water for 5-10 minutes to ensure the permeability of the ultrafiltration membrane.

[0023] Furthermore, in step 5, after adding anhydrous ethanol, the stirring speed is 80-120 r / min and the stirring time is 30-60 minutes to ensure that the anhydrous ethanol and the concentrate are fully mixed and to improve the precipitation efficiency of xylan.

[0024] Furthermore, in step 1, if the crushed corn husk powder is not used in time, it should be placed in a sealed bag and stored in a desiccator. Silica gel desiccant should be placed in the desiccator to prevent the corn husk powder from absorbing moisture and deteriorating.

[0025] Furthermore, in step 5, a vacuum filtration device is used to filter the precipitate, with a filtration pressure of 0.04-0.06 MPa. During the filtration process, a layer of filter paper is laid on the filter cloth to improve the filtration effect and reduce the loss of precipitate.

[0026] The present invention has the following advantages over the prior art:

[0027] (1) The present invention adopts a combination of high-temperature cooking and ball milling pretreatment, which can more fully destroy the dense structure of corn husks and significantly improve the exposure of xylan, creating favorable conditions for subsequent enzymatic hydrolysis and greatly improving the xylan conversion rate;

[0028] (2) The compound enzyme preparation in this invention is composed of xylanase CsXyn10B, CsXyn11A, arabinosidase and ferulic acid esterase in a specific ratio. Each enzyme component works synergistically, is highly targeted, has high enzymatic hydrolysis efficiency, can effectively reduce the amount of enzyme preparation used, and save production costs.

[0029] (3) The process parameters in this invention have been optimized and designed. The parameters of each step from raw material pretreatment to product drying are scientific and reasonable, and the operation is highly controllable. This can effectively ensure the stability of product quality and avoid problems such as inconsistent product purity caused by parameter fluctuations.

[0030] (4) The entire process of this invention does not require the use of toxic and harmful chemical reagents. It adopts a combination of physical pretreatment and biological enzymatic hydrolysis, which is green and environmentally friendly, with no pollutant emissions, meets the requirements of sustainable development, and the product is highly safe.

[0031] (5) The process steps of this invention are simple, the equipment requirements are conventional, the energy consumption is low, the production cost is low, the xylan conversion rate and product purity are high, and it is easy to realize industrial scale-up production, which has good economic and social benefits. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart illustrating the overall process for preparing corn husk xylan according to the present invention.

[0034] Figure 2 This is a flowchart of the raw material pretreatment process for the corn husk xylan preparation process of the present invention;

[0035] Figure 3 This is a flowchart of the high-temperature cooking process for preparing corn husk xylan according to the present invention.

[0036] Figure 4 This is a flow chart of the ball milling process for preparing corn husk xylan according to the present invention;

[0037] Figure 5 This is a flowchart of the complex enzymatic hydrolysis process for preparing corn husk xylan according to the present invention;

[0038] Figure 6 This is a flowchart of the enzymatic hydrolysate post-treatment process for the corn husk xylan preparation process of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Reference Figures 1-6 And Table 1, the process for preparing corn husk xylan by high-temperature cooking, ball milling combined with compound enzymatic method includes the following steps:

[0042] Step 1, Pre-treatment of corn husk raw materials: Select corn husks that are free from mold and impurities, rinse them three times with clean water to remove dust, dirt and soluble impurities attached to the surface, and then place the rinsed corn husks in a hot air drying oven and dry them for 6 hours at a temperature of 60℃ and a wind speed of 1m / s. After drying, pulverize them with a pulverizer and pass them through a 40-mesh sieve to obtain corn husk powder. Place the corn husk powder in a sealed bag and store it in a desiccator containing silica gel desiccant for later use.

[0043] Step 2, High-temperature cooking treatment: Mix the corn husk powder obtained in Step 1 with deionized water at a ratio of 1:8 (w / v), inject the mixture into a high-temperature cooking device, turn off the device and purge the internal air with nitrogen at a flow rate of 0.5 L / min for 5 minutes. After the purge is complete, raise the temperature to 120°C and maintain this temperature and pressure at 0.15 MPa for 60 minutes. After cooking, allow the mixture to cool naturally to room temperature to obtain the cooked corn husk slurry.

[0044] Step 3, ball milling: Transfer the corn husk slurry obtained in Step 2 to a ball mill, add zirconia balls with a particle size of 0.5 mm, the ball-to-material ratio is 10:1 (w / w), adjust the ball mill speed to 200 r / min, and ball mill for 120 minutes. During the ball milling process, stop the machine for 5 minutes every 20 minutes to maintain the ball milling environment temperature within the range of 30-40℃. After the ball milling is completed, a refined corn husk slurry is obtained.

[0045] Step 4, compound enzymatic hydrolysis: The pH of the corn husk slurry obtained in Step 3 was adjusted to 4.5 using a 0.05 mol / L citrate-sodium citrate buffer solution. During the adjustment process, the buffer solution was added while stirring at a speed of 100 r / min. Then, a compound enzyme preparation was added at a rate of 0.5% (w / w) of the dry weight of the corn husk powder. The compound enzyme preparation was composed of xylanase CsXyn10B with an enzyme activity of 10000 U / g, xylanase CsXyn11A with an enzyme activity of 12000 U / g, arabinosidase with an enzyme activity of 8000 U / g, and ferulic acid esterase with an enzyme activity of 5000 U / g, mixed in a mass ratio of 3:3:2:2. Enzymatic hydrolysis was carried out at 50℃ and a stirring speed of 150 r / min for 24 hours to obtain the enzymatic hydrolysate.

[0046] Step 5, post-treatment of enzymatic hydrolysate: The enzymatic hydrolysate obtained in Step 4 was placed in an 85℃ water bath for 20 minutes to inactivate the enzyme. After inactivation, the hydrolysate was cooled to room temperature and then centrifuged at 8000 r / min for 30 minutes. The supernatant was collected and ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 5000 Da at an operating pressure of 0.2 MPa. During ultrafiltration, the ultrafiltration membrane was backwashed with deionized water for 5 minutes every 30 minutes. The retentate was collected and concentrated to 1 / 3 of its original volume under vacuum conditions of 0.06 MPa and 50℃. After concentration, 3 times the volume of anhydrous ethanol was added, and the mixture was stirred at 80 r / min for 30 minutes. The mixture was allowed to stand for 24 hours to precipitate. Then, the precipitate was collected by filtration under a vacuum pressure of 0.04 MPa using a vacuum filtration device. A layer of filter paper was laid on the filter cloth during filtration. The precipitate was placed in a vacuum drying oven and dried at 45℃ for 12 hours to obtain corn husk xylan product.

[0047] The finished product was found to have a xylan purity of 92.3% and a conversion rate of 58.7%.

[0048] Example 2

[0049] Reference Figures 1-6 And Table 1, a process for preparing corn husk xylan by high-temperature cooking, ball milling and compound enzymatic method, includes the following steps:

[0050] Step 1, Pre-treatment of corn husk raw materials: Select corn husks that are free from mold and impurities, rinse them 4 times with clean water to remove dust, dirt and soluble impurities attached to the surface, and then place the rinsed corn husks in a hot air drying oven and dry them for 5 hours at a temperature of 70℃ and a wind speed of 1.5m / s. After drying, pulverize them with a pulverizer and pass them through a 50-mesh sieve to obtain corn husk powder. Place the corn husk powder in a sealed bag and put it in a desiccator containing silica gel desiccant for storage and future use.

[0051] Step 2, High-temperature cooking treatment: Mix the corn husk powder obtained in Step 1 with deionized water at a material-to-liquid ratio of 1:10 (w / v), inject the mixture into the high-temperature cooking equipment, turn off the equipment and purge the internal air with nitrogen at a flow rate of 0.8 L / min for 8 minutes. After the purge is complete, raise the temperature to 130°C and cook for 45 minutes at this temperature and a pressure of 0.2 MPa. After cooking, allow the mixture to cool naturally to room temperature to obtain the cooked corn husk slurry.

[0052] Step 3, ball milling: Transfer the corn husk slurry obtained in Step 2 to a ball mill, add zirconia balls with a particle size of 1.0 mm, the ball-to-material ratio is 12:1 (w / w), adjust the ball mill speed to 250 r / min, and ball mill for 90 minutes. During the ball milling process, stop the machine for 5 minutes every 25 minutes to maintain the ball milling environment temperature within the range of 30-40℃. After the ball milling is completed, a refined corn husk slurry is obtained.

[0053] Step 4, compound enzymatic hydrolysis: The pH of the corn husk slurry obtained in Step 3 was adjusted to 5.0 using a 0.08 mol / L citrate-sodium citrate buffer solution. During the adjustment process, the buffer solution was added while stirring at a speed of 120 r / min. Then, a compound enzyme preparation was added at a rate of 1.0% (w / w) of the dry weight of the corn husk powder. The compound enzyme preparation was composed of xylanase CsXyn10B with an enzyme activity of 12000 U / g, xylanase CsXyn11A with an enzyme activity of 15000 U / g, arabinosidase with an enzyme activity of 10000 U / g, and ferulic acid esterase with an enzyme activity of 6000 U / g, mixed in a mass ratio of 3:3:2:2. Enzymatic hydrolysis was carried out at 55℃ and a stirring speed of 180 r / min for 18 hours to obtain the enzymatic hydrolysate.

[0054] Step 5, post-treatment of enzymatic hydrolysate: The enzymatic hydrolysate obtained in Step 4 was placed in a 90℃ water bath for 18 minutes to inactivate the enzyme. After inactivation, the hydrolysate was cooled to room temperature and then centrifuged at 9000 r / min for 25 minutes. The supernatant was collected and ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 8000 Da at an operating pressure of 0.25 MPa. During ultrafiltration, the ultrafiltration membrane was backwashed with deionized water for 8 minutes every 45 minutes. The retentate was collected and concentrated to 2 / 5 of its original volume under vacuum at 0.07 MPa and 55℃. After concentration, 4 times the volume of anhydrous ethanol was added, and the mixture was stirred at 100 r / min for 45 minutes. The mixture was allowed to stand for 18 hours to precipitate. Then, the precipitate was collected by vacuum filtration at a pressure of 0.05 MPa. A layer of filter paper was laid on the filter cloth during filtration. The precipitate was placed in a vacuum drying oven and dried at 50℃ for 10 hours to obtain corn husk xylan product.

[0055] The finished product was found to have a xylan purity of 94.6% and a conversion rate of 62.4%.

[0056] Example 3

[0057] Reference Figures 1-6 And Table 1, a process for preparing corn husk xylan by high-temperature cooking, ball milling and compound enzymatic method, includes the following steps:

[0058] Step 1, Pre-treatment of corn husk raw materials: Select corn husks that are free from mold and impurities, rinse them 5 times with clean water to remove dust, dirt and soluble impurities attached to the surface, and then place the rinsed corn husks in a hot air drying oven and dry them for 4 hours at a temperature of 80℃ and a wind speed of 2m / s. After drying, pulverize them through a pulverizer and pass them through a 60-mesh sieve to obtain corn husk powder. Place the corn husk powder in a sealed bag and store it in a desiccator containing silica gel desiccant for later use.

[0059] Step 2, High-temperature cooking treatment: Mix the corn husk powder obtained in Step 1 with deionized water at a material-to-liquid ratio of 1:12 (w / v), inject the mixture into a high-temperature cooking device, turn off the device and purge the internal air with nitrogen at a flow rate of 1L / min for 10 minutes. After the purge is complete, raise the temperature to 140℃ and maintain this temperature and 0.25MPa pressure for 30 minutes. After cooking, allow the mixture to cool naturally to room temperature to obtain the cooked corn husk slurry.

[0060] Step 3, ball milling: Transfer the corn husk slurry obtained in Step 2 to a ball mill, add zirconia balls with a particle size of 1.5 mm, the ball-to-material ratio is 15:1 (w / w), adjust the ball mill speed to 300 r / min, and ball mill for 60 minutes. During the ball milling process, stop the machine for 5 minutes every 30 minutes to maintain the ball milling environment temperature within the range of 30-40℃. After the ball milling is completed, a refined corn husk slurry is obtained.

[0061] Step 4, compound enzymatic hydrolysis: The pH of the corn husk slurry obtained in Step 3 was adjusted to 5.5 using a 0.1 mol / L citrate-sodium citrate buffer solution. During the adjustment process, the buffer solution was added while stirring at a speed of 150 r / min. Then, a compound enzyme preparation was added at a rate of 1.5% (w / w) of the dry weight of the corn husk powder. The compound enzyme preparation was composed of xylanase CsXyn10B with an enzyme activity of 15000 U / g, xylanase CsXyn11A with an enzyme activity of 18000 U / g, arabinosidase with an enzyme activity of 12000 U / g, and ferulic acid esterase with an enzyme activity of 8000 U / g, mixed in a mass ratio of 3:3:2:2. Enzymatic hydrolysis was carried out at 60℃ and a stirring speed of 200 r / min for 12 hours to obtain the enzymatic hydrolysate.

[0062] Step 5, Post-treatment of the enzymatic hydrolysate: The enzymatic hydrolysate obtained in Step 4 was placed in a 95℃ water bath for 15 minutes to inactivate the enzyme. After enzyme inactivation, the hydrolysate was cooled to room temperature and then centrifuged at 10000 r / min for 20 minutes. The supernatant was collected and ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 10000 Da at an operating pressure of 0.3 MPa. During ultrafiltration, the ultrafiltration membrane was backwashed with deionized water for 10 minutes every 60 minutes. The retentate was collected. The retentate was concentrated to half its original volume under vacuum conditions of 0.08 MPa and 60°C. After concentration, 5 times the volume of anhydrous ethanol was added, and the mixture was stirred at 120 r / min for 60 minutes. After standing for 12 hours to precipitate, the precipitate was collected by vacuum filtration under a filtration pressure of 0.06 MPa. During filtration, a layer of filter paper was laid on the filter cloth, and the precipitate was placed in a vacuum drying oven and dried at 55°C for 8 hours to obtain corn husk xylan product.

[0063] Testing revealed that the xylan purity in the finished product was 95.8%, and the conversion rate was 65.2%.

[0064] Working principle

[0065] This invention employs a combined pretreatment process of high-temperature cooking and ball milling. First, high temperature and pressure are used to break the bonds between cellulose, hemicellulose, and lignin in corn husks, loosening the dense physical structure of the corn husks and exposing xylan. Then, ball milling further refines the corn husk particles, increasing the specific surface area and providing more sites for subsequent enzymatic hydrolysis. Next, a targeted complex enzyme preparation is selected, in which xylanases CsXyn10B and CsXyn11A specifically hydrolyze the glycosidic bonds in xylan molecules, while arabinosidase and ferulic acid esterase work synergistically to remove side chain groups on xylan molecules, promoting complete release of xylan. Finally, post-treatment steps such as enzyme inactivation, centrifugation, ultrafiltration, concentration, alcohol precipitation, and drying remove impurities, yielding a high-purity corn husk xylan product.

[0066] The hot air drying box has a wind speed of 1-2 m / s, which can ensure that the corn husks are heated evenly during the drying process and avoid local overheating that could damage the nutrients.

[0067] The nitrogen purging time is 5-10 minutes and the flow rate is 0.5-1L / min, which can completely remove the air inside the equipment and prevent the corn husks from oxidizing during high-temperature cooking.

[0068] The zirconia balls have a particle size of 0.5-1.5mm and are produced by intermittent ball milling. With regular shutdowns for heat dissipation, the ball milling environment temperature can be maintained at 30-40℃, ensuring stable ball milling results.

[0069] The pH was adjusted using a 0.05-0.1 mol / L citrate-sodium citrate buffer solution while stirring at 100-150 r / min, which ensured a uniform and stable pH value and provided a suitable environment for the enzymatic hydrolysis reaction.

[0070] By limiting the enzyme activity range of each complex enzyme component, the efficient synergy of the enzymatic hydrolysis system can be ensured, thereby improving the degradation efficiency of xylan.

[0071] The ultrafiltration operating pressure is controlled at 0.2-0.3 MPa, and the membrane is backwashed with deionized water for 5-10 minutes every 30-60 minutes to maintain the permeability of the ultrafiltration membrane and ensure the separation effect.

[0072] Adding anhydrous ethanol and stirring at 80-120 r / min for 30-60 minutes can promote thorough mixing of ethanol and concentrate, thereby improving xylan precipitation efficiency.

[0073] Unused corn husk powder should be sealed and stored in a desiccator containing silica gel desiccant to prevent the powder from absorbing moisture and deteriorating, thus ensuring the quality of the raw materials.

[0074] Among them, controlling the vacuum filtration pressure at 0.04-0.06MPa and laying filter paper on the filter cloth can improve the filtration effect and reduce the loss of precipitates.

[0075] Results Measurement

[0076] The test data for Examples 1, 2, and 3, and Comparative Examples 1, 2, 3, and 4 are as follows:

[0077]

[0078] Table 1 Sample Test Data

[0079] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for preparing corn husk xylan using a combination of high-temperature cooking, ball milling, and compound enzymatic methods, characterized in that, Includes the following steps: Step 1, corn husk raw material pretreatment: Select corn husks that are free from mold and impurities, rinse them with clean water 3-5 times to remove dust, dirt and soluble impurities attached to the surface, and then place the rinsed corn husks in a hot air drying oven and dry them at 60-80℃ for 4-6 hours. After drying, pulverize them through a pulverizer and pass them through a 40-60 mesh sieve to obtain corn husk powder. Step 2, High-temperature cooking treatment: Mix the corn husk powder obtained in Step 1 with deionized water at a material-to-liquid ratio of 1:8-1:12 (w / v), inject the mixture into a high-temperature cooking device, turn off the device and purge the internal air with nitrogen. After the purge is complete, raise the temperature to 120-140℃ and maintain this temperature and pressure of 0.15-0.25MPa for cooking for 30-60 minutes. After cooking, allow the mixture to cool naturally to room temperature to obtain the cooked corn husk slurry. Step 3, ball milling: Transfer the corn husk slurry obtained in Step 2 to a ball mill, add zirconia balls, and the ball-to-material ratio is 10:1-15:1 (w / w). Adjust the ball mill speed to 200-300 r / min and ball mill for 60-120 minutes. During the ball milling process, stop the machine for 5 minutes every 20-30 minutes to prevent the equipment from overheating. After the ball milling is completed, a refined corn husk slurry is obtained. Step 4, compound enzymatic hydrolysis treatment: Adjust the pH of the corn husk slurry obtained in Step 3 to 4.5-5.5, and then add a compound enzyme preparation. The amount of compound enzyme preparation added is 0.5%-1.5% (w / w) of the dry weight of the corn husk powder. The compound enzyme preparation is composed of xylanase CsXyn10B, xylanase CsXyn11A, arabinosidase and ferulic acid esterase mixed in a mass ratio of 3:3:2:

2. Enzymatic hydrolysis is carried out at a temperature of 50-60℃ and a stirring speed of 150-200r / min for 12-24 hours to obtain the enzymatic hydrolysate. Step 5, post-treatment of the enzymatic hydrolysate: Place the enzymatic hydrolysate obtained in Step 4 in a water bath at 85-95℃ for 15-20 minutes to inactivate the enzyme. After inactivation, cool the hydrolysate to room temperature and then centrifuge at 8000-10000 r / min for 20-30 minutes. Collect the supernatant and ultrafilter it through an ultrafiltration membrane with a molecular weight cutoff of 5000-10000 Da. Collect the retentate and vacuum concentrate it to 1 / 3-1 / 2 of its original volume under vacuum conditions of 0.06-0.08 MPa and 50-60℃. After concentration, add 3-5 times the volume of anhydrous ethanol, stir evenly, and let it stand to precipitate for 12-24 hours. Then filter and collect the precipitate. Place the precipitate in a vacuum drying oven and dry it at 45-55℃ for 8-12 hours to obtain the corn husk xylan product.

2. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 1, characterized in that, In step 1, the air velocity of the hot air drying box is set to 1-2 m / s to ensure that the corn husks are heated evenly during the drying process and to avoid local overheating that could damage the nutrients.

3. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 2, characterized in that, In step 2, the nitrogen purging time is 5-10 minutes, and the nitrogen flow rate is maintained at 0.5-1L / min during the purging process to ensure that the air inside the equipment is completely discharged and to prevent the corn husks from undergoing an oxidation reaction during the high-temperature cooking process.

4. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 3, characterized in that, In step 3, the zirconia balls have a particle size of 0.5-1.5 mm. The ball milling process is carried out in an intermittent manner, and the ball milling environment temperature is maintained within the range of 30-40℃ by periodically stopping the machine to dissipate heat.

5. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 2, characterized in that, In step 4, the pH value of the corn husk slurry is adjusted using a citrate-sodium citrate buffer solution with a concentration of 0.05-0.1 mol / L. During the adjustment process, the buffer solution is added while stirring at a speed of 100-150 r / min to ensure that the pH value is uniform and stable.

6. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 1, characterized in that, In step 4, the enzyme activity of xylanase CsXyn10B is 10000-15000 U / g, the enzyme activity of xylanase CsXyn11A is 12000-18000 U / g, the enzyme activity of arabinosidase is 8000-12000 U / g, and the enzyme activity of ferulic acid esterase is 5000-8000 U / g.

7. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 1, characterized in that, In step 5, the operating pressure of ultrafiltration is 0.2-0.3 MPa. During the ultrafiltration process, the ultrafiltration membrane is cleaned every 30-60 minutes using deionized water for backwashing, with a washing time of 5-10 minutes, to ensure the permeability of the ultrafiltration membrane.

8. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 1, characterized in that, In step 5, after adding anhydrous ethanol, the stirring speed is 80-120 r / min and the stirring time is 30-60 minutes to ensure that the anhydrous ethanol and the concentrate are fully mixed and to improve the precipitation efficiency of xylan.

9. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 1, characterized in that, In step 1, if the crushed corn husk powder is not used in time, it should be placed in a sealed bag and stored in a desiccator. Silica gel desiccant should be placed in the desiccator to prevent the corn husk powder from absorbing moisture and deteriorating.

10. The process for preparing corn husk xylan by high-temperature cooking, ball milling, and compound enzymatic method according to claim 1, characterized in that, In step 5, a vacuum filtration device is used to filter the precipitate, with a filtration pressure of 0.04-0.06 MPa. During the filtration process, a layer of filter paper is laid on the filter cloth to improve the filtration effect and reduce the loss of precipitate.

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