Preparation method and application of yeast nano-β-glucan dry powder

Abstract

The present invention discloses a preparation method and application of yeast nano-β-glucan dry powder. Yeast cells are autolyzed to obtain yeast cell walls, yeast β-glucan is extracted by high temperature, and then the yeast β-glucan is deproteinized. The yeast β-glucan is treated with chlorine dioxide, freeze-dried, homogenized and crushed by high pressure, vacuum concentrated, and vacuum dried to obtain nano-β-glucan dry powder with a particle size of less than 100 nm. The present invention improves the physical properties of yeast β-glucan and enhances its physiological function. The prepared nano-β-glucan dry powder not only has good suspension properties and does not sediment even after being left still for a long time, is easy to use, but also has improved in vitro blood sugar and blood lipid lowering functions. In the process of the present invention, no acid or alkali that corrodes equipment is used, and no toxic or harmful substances are used. All raw materials used are food production raw materials, which are suitable for industrial production. The obtained product can be used as a functional food ingredient or food additive.

Description

Technical Field

[0001] The present invention belongs to the technical field of beta-glucan preparation, and relates to a preparation method and application of yeast nano-beta-glucan, in particular to a preparation method and application of yeast nano-beta-glucan dry powder. Background Art

[0002] β-glucan is a natural polysaccharide compound composed of glucose molecules linked by β-1,3-glycosidic bonds to form a main chain, and β-1,6-glycosidic bonds to form side chains. This means that glucose molecules branch out from the main chain via β-1,6-linked bonds. β-glucan is widely found in plants, fungi, and bacteria, and has numerous physiological functions, including immune regulation, anti-tumor effects, and lipid and blood sugar lowering. It has been widely used in medicine, healthcare products, and food.

[0003] Yeast β-glucan is a major component of the yeast cell wall, located in the inner layer of the cell wall and accounting for approximately 60% of the cell wall's dry weight. Due to its unique three-dimensional helical structure, yeast β-glucan is insoluble in water and presents as granules with a particle size similar to that of the yeast cell, typically 3 to 5 μm. Currently, technologies for separating and extracting β-glucan from yeast cell walls are well-established, including acid and alkaline methods, high-temperature extraction, and acid-base extraction.

[0004] Yeast cells can provide a rich resource of natural β-glucan. However, due to the special structure of yeast β-glucan, it is insoluble in water, easily forms precipitation, and is inconvenient to use. Therefore, in order to avoid the problem of sedimentation of yeast β-glucan during use, people have conducted research on how to prepare water-soluble yeast β-glucan. For example, the Chinese invention patent application with document number 202310006654.4, "A high-purity water-soluble yeast β-glucan and its preparation method", uses waste yeast mud as raw material, obtains yeast cell walls through cell wall lysis, density gradient centrifugation and other methods, uses dimethyl sulfoxide to assist in purification to remove impurities, and then combines ethanol precipitation degradation to finally obtain a high-purity water-soluble yeast glucan product. In the above process, dimethyl sulfoxide, a non-food raw material, is used, which limits the application range of the prepared water-soluble yeast β-glucan. For example, the Chinese invention patent application with document number 202210982808.9, "A water-soluble yeast β-glucan and its preparation method", uses brewer's yeast liquid as raw material, uses the acid-base method to extract non-water-soluble yeast β-glucan, and then treats it with glucanase, alkaline protease hydrolysis, and endonuclease. It is then separated by a membrane through an intercepting organic membrane to obtain water-soluble yeast β-glucan. The above process uses acids and alkalis, corrodes equipment, and uses a large amount of enzyme preparations, resulting in high overall production costs.

[0005] In recent years, studies have shown that nano-sizing yeast β-glucan can enhance its physiological functions, such as anti-tumor, lipid-lowering, and blood sugar-lowering. Based on research on the preparation of water-soluble glucans, research on nano-sizing water-soluble β-glucan is still ongoing. This involves chemically modifying yeast β-glucan to alter its solubility and then loading it onto nano-scale carriers. For example, Chinese patent application No. 201810145959.2, "Antigen-Loaded Water-Soluble Aminated β-1,3-D-Glucan Nanoparticles, Preparation Method, and Application thereof," involves degrading and purifying dextran to obtain water-soluble dextran. The dextran is then reacted with N'N-carbonyldiimidazole under nitrogen. The dextran is then precipitated, washed, dried, and aminated with triethylamine and diethylamine. The resulting solution is then dialyzed for three days using a 1 kDa molecular weight dialysis bag, and the retentate is freeze-dried to obtain the water-soluble aminated β-glucan. Antigen protein and the ionic crosslinker sodium tripolyphosphate are then added to obtain antigen-loaded water-soluble aminated β-glucan nanoparticles. This preparation method involves loading the water-soluble β-glucan onto the crosslinker, resulting in nanoparticles of pure β-glucan. This process is not only extremely complex but also utilizes a significant amount of non-food materials. The resulting product cannot be used as a functional food ingredient or food additive. In addition, the above preparation process cycle is very long. The dialysis process of the dialysis bag alone lasts for 3 days. The overall production cost is very high and it is not suitable for large-scale production.

[0006] It can be seen that there is currently no research on the preparation process of insoluble nano yeast β-glucan. This is mainly because: (1) dry powder yeast β-glucan particles have high hardness and toughness, and basically cannot be directly crushed to the nanometer level; (2) wet yeast β-glucan particles show strong flexibility and are difficult to crush to the nanometer level without chemical modification, modification or enzymatic hydrolysis. During the chemical modification or modification process, non-food grade reagents or substances will inevitably be used, resulting in the prepared β-glucan being unusable as a food ingredient or food additive. Therefore, it is necessary to develop a preparation method for yeast nano β-glucan dry powder that meets the requirements of the food industry, is easy to use, and is suitable for industrial production. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method and application of yeast nano-β-glucan dry powder to improve its physical properties, prevent precipitation during use, and at the same time, enhance its physiological functions (hypoglycemic and hypolipidemic functions), so that it can be used as a functional food ingredient or food additive.

[0008] The technical solution adopted by the present invention provides a preparation method and application of yeast nano-β-glucan dry powder. Yeast cells are autolyzed to obtain yeast cell walls, and yeast β-glucan is obtained by high-temperature extraction. The key is that the above yeast β-glucan is deproteinized to obtain deproteinized β-glucan, and then the deproteinized β-glucan is treated with chlorine dioxide, freeze-dried, high-pressure homogenized and crushed, vacuum concentrated, and vacuum dried to obtain nano-β-glucan dry powder with a particle size of less than 100 nm.

[0009] Furthermore, the above-mentioned deproteinization treatment is to prepare the above-mentioned yeast β-glucan into a suspension with water, add alkaline protease under alkaline conditions to make the enzyme activity 60,000 U / L to 100,000 U / L, carry out enzymatic hydrolysis reaction at 45°C to 55°C for 2h to 4h, centrifuge, collect the precipitate, and obtain the above-mentioned deproteinized β-glucan; the above-mentioned alkaline conditions are pH 9 to 11.

[0010] Furthermore, the chlorine dioxide treatment is to prepare the deproteinized β-glucan into a suspension with water, add a chlorine dioxide effervescent tablet so that the chlorine dioxide concentration in the suspension is 120 mg / L to 180 mg / L, treat in a water bath at 75° C. to 85° C. for 20 min to 40 min, centrifuge, collect the precipitate and wash the precipitate with water.

[0011] Furthermore, the above-mentioned freeze-drying is to spread the chlorine dioxide-treated glucan on a tray with a thickness of 0.4 cm to 0.6 cm, place it in a freeze dryer, control the cold trap temperature to -50°C to -40°C, and the vacuum degree of the drying chamber to 1Pa to 6Pa, and dry it for 30h to 40h. The dried β-glucan is crushed and passed through a 120-mesh sieve to obtain β-glucan dry powder.

[0012] Furthermore, the high-pressure homogenization and crushing is performed by preparing the freeze-dried β-glucan into a suspension with ethanol having a mass concentration of 90% to 100%, and homogenizing the suspension at 600 bar to 1000 bar for 10 to 25 times.

[0013] Furthermore, the above-mentioned vacuum concentration is to concentrate the β-glucan crushed by high-pressure homogenization to 20% to 30% of the original volume at 55° C. to 65° C. and a vacuum degree of 0.08 MPa to 0.1 MPa to obtain a β-glucan concentrated solution.

[0014] Furthermore, the above-mentioned vacuum drying is to spread the β-glucan concentrate on a tray with a thickness of 0.7 cm to 0.9 cm, a vacuum degree of 0.08 MPa to 0.1 MPa, and dry it at a temperature of 55°C to 65°C for 2h to 4h. After drying, it is crushed and passed through a 200-mesh sieve to obtain nano β-glucan powder with a particle size of less than 100 nm.

[0015] Preferably, the specific method for obtaining yeast cell walls by autolyzing yeast cells is as follows: active dry yeast powder is prepared into a yeast cell suspension with water, the pH value is adjusted to 5.0-6.0, 400U / mL-500U / mL papain is added, and the suspension is allowed to stand at 50°C-55°C for 30h-42h to allow the yeast cell walls to autolyze, followed by centrifugation, collecting the precipitate, and washing the precipitate with water to obtain autolyzed yeast cell walls.

[0016] Preferably, the specific method for obtaining yeast β-glucan by high-temperature extraction is as follows: preparing a suspension of autolyzed yeast cell walls with water, placing the suspension in a high-pressure steam sterilizer, treating the suspension at 115°C to 125°C for 6h to 10h, centrifuging the suspension, collecting the precipitate, and washing the precipitate with water to obtain yeast β-glucan.

[0017] The invention discloses an application of yeast nano beta-glucan dry powder. The nano beta-glucan dry powder prepared by the invention is used as a functional food ingredient or a food additive.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The nano-β-glucan dry powder prepared by the present invention has a particle size of 40nm to 90nm and a narrow particle size distribution range, which meets the requirement that the nanoparticles have a particle size of less than 100nm;

[0020] 2. The present invention improves the physical properties of yeast β-glucan and enhances its physiological functions. Although the prepared yeast nano β-glucan dry powder is insoluble, it has good suspension properties and will not settle even after long periods of static storage, making it easy to use. Compared with ordinary glucan (not glucan with a particle size less than 100 nm), its in vitro hypoglycemic and hypolipidemic functions are enhanced;

[0021] 3. In the process of preparing nanoparticle β-glucan of the present invention, no acid or alkali that corrodes equipment is used, and no toxic or harmful substances are used. Instead, common and low-cost raw materials for food production are used. This is not only more suitable for industrial production, but the obtained product can also be used as a functional food ingredient or food additive. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the infrared spectrum of the nano-β-glucan prepared by the present invention.

[0023] Figure 2 This is a comparison of the suspension properties of nano-β-glucan and ordinary glucan at 0h.

[0024] Figure 3 This is a comparison of the 1h suspension properties of nano-β-glucan and ordinary glucan.

[0025] Figure 4This is a comparison of the 6h suspension properties of nano-β-glucan and ordinary glucan.

[0026] Figure 5 This is a comparison of the suspension properties of nano-β-glucan and ordinary glucan for 18 hours.

[0027] Figure 6 This is a comparison chart of the inhibition rates of nano-β-glucan and ordinary glucan on pancreatic lipase activity in vitro.

[0028] Figure 7 This is a comparison chart of the inhibition rates of nano-β-glucan and ordinary glucan on α-glucosidase activity in vitro.

[0029] In the accompanying drawings, 1 is nano β-glucan and 2 is ordinary glucan. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing and using yeast nano-β-glucan dry powder. The following provides a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0031] If the specific conditions are not specified in the examples, the experiments can be carried out under conventional conditions; if the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0032] Example 1 to Example 4

[0033] The relevant process parameters in the following steps are shown in Table 1.

[0034] Step 1: Yeast cell autolysis

[0035] Active dry yeast powder was prepared into a 15% bacterial suspension with water, the pH value was adjusted with 0.5M hydrochloric acid, papain with a certain enzyme activity was added, and the suspension was placed in a biochemical incubator and kept at a constant temperature for a certain period of time to allow the yeast cells to autolyze.

[0036] After the autolysis was complete, the bacterial suspension was centrifuged at 5000 rpm for 5 min, the supernatant was discarded, and the precipitate was collected and washed three times with water to obtain the yeast cell wall.

[0037] Step 2: High temperature extraction

[0038] A 20% suspension of autolyzed yeast cell walls was prepared with water and placed in a high-pressure steam sterilizer. After high-temperature treatment for a specified period of time, the suspension was centrifuged at 5000 rpm for 5 minutes. The supernatant was discarded and the precipitate was collected. The precipitate was washed three times with water to obtain a sludge of yeast β-glucan.

[0039] The discarded supernatant can be used to prepare mannan.

[0040] Step 3: Deproteinization

[0041] Prepare a 20% suspension of yeast β-glucan in water, adjust the pH to alkaline with 0.1 M NaOH solution, add alkaline protease to the enzyme activity shown in Table 1, and perform enzymatic hydrolysis in a water bath at a constant temperature.

[0042] After the reaction was completed, the bacterial suspension was centrifuged at 5000 rpm for 5 min, and the precipitate was collected to obtain deproteinized β-glucan.

[0043] Step 4: Chlorine dioxide treatment

[0044] A 20% suspension of deproteinized β-glucan was prepared with water, to which a chlorine dioxide effervescent tablet was added so that the final concentration of chlorine dioxide in the system met the requirements of Table 1, and the suspension was placed in a water bath and kept at a constant temperature for a certain period of time.

[0045] After chlorine dioxide treatment, the bacterial suspension was centrifuged at 5000 rpm for 5 minutes, the supernatant was discarded, and the β-glucan precipitate was collected and washed once with water.

[0046] Step 5: Freeze Drying

[0047] The β-glucan precipitate obtained in "Step 4" is evenly spread on a tray with a thickness that meets the requirements of Table 1. It is placed in a freeze dryer, and the cold trap temperature and the vacuum degree of the drying chamber are controlled according to Table 1. Dry for a certain period of time.

[0048] The freeze-dried β-glucan was crushed and passed through a 120-mesh sieve to obtain β-glucan dry powder.

[0049] Step 6: High-pressure homogenization and crushing

[0050] The β-glucan dry powder obtained in "Step 5" was prepared into a 20% suspension with ethanol of different mass concentrations, and high-pressure homogenization and crushing were performed according to the parameters in Table 1 to obtain a nano-β-glucan ethanol suspension.

[0051] Step 7: Vacuum concentration

[0052] The nano-β-glucan ethanol suspension was vacuum concentrated at the temperature and pressure according to Table 1 to obtain a nano-β-glucan concentrated solution with a glucan concentration of about 70%, and ethanol was recovered by condensation at the same time.

[0053] Step 8: Vacuum drying

[0054] The nanoglucan concentrate was evenly spread on the tray and vacuum dried according to the parameters in Table 1.

[0055] After drying, the mixture was crushed and passed through a 200-mesh sieve to obtain nano-β-glucan dry powder.

[0056] Table 1: Process parameter table of Examples 1 to 4

[0057]

[0058] Table 1: Process parameter table of Example 1 to Example 4

[0059]

[0060] Table 1: Process parameter table of Example 1 to Example 4

[0061]

[0062]

[0063] Measurement and analysis

[0064] 1. Particle size determination

[0065] The particle size of nano-β-glucan dry powder was measured using a laser nanoparticle size analyzer.

[0066] Each sample was measured five times, and the average particle size was calculated based on the longest particle size. The corresponding sample numbers are sample 1 to sample 4. The results are shown in Table 2.

[0067] 2. Yield determination

[0068] The mass of the prepared nano-β-glucan dry powder sample was measured, and the β-glucan yield was calculated according to Formula 1. The results are shown in Table 2:

[0069] Formula 1:

[0070] Nano β-glucan yield (%) = mass of prepared nano β-glucan dry powder sample (g) / weight of yeast dry powder (g) × 100%.

[0071] 3. Determination of glucan content

[0072] According to the Chinese light industry industry standard "Yeast β-glucan", standard number QB / T 4572-2021, "6.4 Yeast β-glucan content" recorded on page 4, the glucan content in the nano β-glucan dry powder sample was determined. The results are shown in Table 2.

[0073] Table 2: Summary of sample particle size, yield and glucan content determination results

[0074]

[0075] Note: "Content (g / 100g)" in Table 2 refers to the β-glucan content in 100g of the tested glucan dry powder converted according to the test results. The same applies to Table 3.

[0076] As can be seen from Table 2, the nano-glucan dry powder prepared by the present invention has a particle size range of 40 nm to 90 nm and uniform particles; the prepared nano-β-glucan dry powder has a high glucan content.

[0077] 4. Infrared spectroscopy analysis

[0078] 3.0 mg of the prepared nano-β-glucan dry powder sample was added with 300 mg of dry potassium bromide powder and ground in a mortar. The mixture was evenly mixed and pressed into tablets. The tablets were scanned and analyzed on an infrared spectrometer. The results are shown in the attached Figure 1 .

[0079] Attachment Figure 1 In 3418cm -1 The absorption peaks at 1248, 1375, and 2925 cm are the stretching vibration peaks of OH; -1 The characteristic peaks of 1062 and 1063 confirmed that the sample was a glucan with β-(1-3) bonds.

[0080] 1455cm -1 The absorption peak at 890 cm is characteristic of the polysaccharide structure; -1 The absorption peak at can confirm that the glycosidic bond in the sample is β-configuration.

[0081] It can be seen that the nano β-glucan dry powder prepared by the present invention meets the characteristics of high-purity yeast β-glucan.

[0082] Comparative Example 1

[0083] Refer to the experimental process of Example 1, except that "step three, deproteinization treatment", "step four, chlorine dioxide treatment" and "step five, freeze drying" are not performed; when performing "step six, high-pressure homogenization and crushing", water is used to prepare the bacterial suspension, and the subsequent operations are the same as in Example 1 to prepare a reference substance 1.

[0084] Comparative Example 2

[0085] The experimental process was the same as in Example 1, except that “Step 4, chlorine dioxide treatment” and “Step 5, freeze drying” were not performed; when “Step 6, high-pressure homogenization and crushing” was performed, water was used to prepare the bacterial suspension, and the subsequent operations were the same as in Example 1 to prepare a reference substance 2.

[0086] Comparative Example 3

[0087] The experimental process was similar to that of Example 1, except that "Step 5, freeze-drying" was not performed; when "Step 6, high-pressure homogenization and crushing" was performed, water was used to prepare the bacterial suspension, and subsequent operations were the same as those of Example 1 to prepare reference substance 3.

[0088] Comparative Example 4

[0089] The experimental process of Example 1 was referred to, except that "Step 5, freeze-drying" was not performed. Subsequent operations were the same as those of Example 1 to prepare reference substance 4.

[0090] The particle size, yield, and glucan content of reference substances 1 to 4 were determined using the same method as described in the determination and analysis section. The results are shown in Table 3.

[0091] Table 3: Summary of the results of determination of particle size, yield and glucan content of reference substances

[0092]

[0093] As shown in Table 3, the present invention reduces the flexibility of β-glucan through the synergistic effect of "step 3, deproteinization", "step 4, chlorine dioxide treatment", "step 5, freeze drying", and "step 6, high-pressure homogenization and crushing", so that nanoyeast β-glucan with a particle size of less than 100 nm can be prepared by physical crushing of β-glucan.

[0094] Particle suspension test

[0095] The nano-β-glucan powder prepared by the present invention was dissolved in water to obtain a nano-β-glucan suspension, and a suspension of ordinary glucan (with a particle size less than 100 nm) dissolved in water was used for comparison. The suspension was allowed to stand for observation. The results are shown in the attached Figure 2 ~Attached Figure 5 .

[0096] By the attached Figure 2 ~Attached Figure 5 It can be seen that the present invention improves the physical properties of yeast β-glucan. Although the nano β-glucan prepared by the present invention is still water-insoluble, it has good suspension properties and does not show sedimentation after standing for 18 hours, while ordinary particle size β-glucan begins to sediment after standing for 1 hour.

[0097] In vitro blood sugar and lipid lowering tests

[0098] The inhibitory effect of glucan on pancreatic lipase activity was determined in vitro to reflect the lipid-lowering ability of glucan; the inhibitory effect of glucan on α-glucosidase activity was determined to reflect the blood sugar-lowering ability of glucan.

[0099] The commercial dextran purchased from Jarrow Formulas, USA was used as a control.

[0100] Test 1: Determination of the ability to inhibit pancreatic lipase activity

[0101] Test method:

[0102] 1. Prepare the β-glucan sample to be tested into a suspension of a certain concentration. Take 3 mL of the suspension into a stoppered test tube and add 3 mL of 1 mg / mL pancreatic lipase solution.

[0103] After incubation at 37°C in a water bath for 10 min, 3 mL of 5 mmol / L substrate p-NPB (4-nitrophenylbutyrate) solution was added and the mixture was reacted in a water bath in the dark for 15 min.

[0104] The mixture was centrifuged, the supernatant was passed through a membrane, and its absorbance at 405 nm was measured.

[0105] 2. Substitute the result into the p-NP standard curve to obtain the amount of p-NP (p-nitrophenol) produced by pancreatic lipase-catalyzed substrate.

[0106] 3. According to formula 2, calculate the inhibition rate of the β-glucan sample to be tested on pancreatic lipase.

[0107] Formula 2:

[0108] Wherein: A and B are the amount of p-NP generated after mixing pancreatic lipase and p-NPB solution and the amount of p-NP generated after mixing dextran sample, pancreatic lipase, and p-NPB solution, respectively.

[0109] The test results are shown in Table 4 and Appendix Figure 6 .

[0110] Table 4: Inhibition rate of pancreatic lipase activity in vitro

[0111]

[0112] Test 2:

[0113] Test method:

[0114] 1. Prepare the β-glucan sample to be tested into a suspension of a certain concentration. Take 3 mL of the suspension into a stoppered test tube and add 3 mL of 0.5 U / mL α-glucosidase solution.

[0115] After shaking in a water bath at 37°C for 10 min, 3 mL of 5 mmol / L p-NPG (4-nitrophenyl-α-D-galactopyranoside) solution was added, and shaking in a water bath at 37°C was continued for 30 min. The reaction was terminated by adding Na2CO3 solution.

[0116] The mixture was centrifuged, the supernatant was passed through a membrane, and its absorbance at 405 nm was measured.

[0117] 2. Substitute the standard curve of p-NP to obtain the amount of p-NP (p-nitrophenol) produced by α-glucosidase-catalyzed substrate.

[0118] 3. According to formula 3, calculate the inhibition rate of the tested glucan sample on α-glucosidase.

[0119] Formula 3:

[0120] Wherein: A and B are the amount of p-NP generated after mixing α-glucosidase and p-NPG solution and the amount of p-NP generated after mixing glucan sample, α-glucosidase, and p-NPG solution, respectively.

[0121] The test results are shown in Table 5 and Appendix Figure 7 .

[0122] Table 5: Inhibition rate of α-glucosidase activity in vitro

[0123] Suspension concentration (mg / L) Inhibition rate of nano-β-glucan (%) Inhibition rate of control β-glucan (%) Improvement rate (%) 10 73.8 60.8 21.4 20 85.6 68.7 24.6 30 90.8 76.2 19.2 40 92.0 78.9 16.6 50 93.1 80.1 16.2

[0124] From Table 4, Table 5 and Appendix Figure 6 , Attachment Figure 7 As can be seen, the nano-β-glucan prepared by the present invention has a higher ability to inhibit the activity of pancreatic lipase and α-glucosidase. Compared with conventional glucan, the nano-β-glucan prepared by the present invention can improve the inhibitory effect of trypsin activity by up to 52.6% and the inhibitory effect of α-glucosidase activity by up to 24.6% in vitro, indicating that the nano-β-glucan prepared by the present invention has greatly enhanced physiological functions.

Claims

1. A method for preparing yeast nano-β-glucan dry powder, comprising autolyzing yeast cells to obtain yeast cell walls, and extracting yeast β-glucan through high temperature, characterized in that: The yeast β-glucan is deproteinized to obtain deproteinized β-glucan, which is then treated with chlorine dioxide, freeze-dried, homogenized and crushed under high pressure, vacuum concentrated, and vacuum dried to obtain nano β-glucan dry powder with a particle size of less than 100 nm; The chlorine dioxide treatment comprises preparing the deproteinized β-glucan into a suspension with water, adding a chlorine dioxide effervescent tablet so that the chlorine dioxide concentration in the suspension is 120 mg / L to 180 mg / L, treating the suspension in a water bath at 75° C. to 85° C. for 20 min to 40 min, centrifuging, collecting the precipitate, and washing the precipitate with water; The freeze drying process comprises spreading the chlorine dioxide-treated beta-glucan on a tray with a thickness of 0.4 cm to 0.6 cm, placing the tray in a freeze dryer, controlling the cold trap temperature at -50°C to -40°C, and the vacuum degree of the drying chamber at 1 Pa to 6 Pa, drying the tray for 30 h to 40 h, and then crushing the dried beta-glucan and passing it through a 120-mesh sieve to obtain beta-glucan dry powder. The high-pressure homogenization and crushing is to prepare the freeze-dried beta-glucan into a suspension with ethanol of mass concentration of 90% to 100%, and homogenize it 10 to 25 times at 600 bar to 1000 bar.

2. The method for preparing yeast nano β-glucan dry powder according to claim 1, characterized in that: The deproteinization treatment comprises preparing the yeast β-glucan into a suspension with water, adding alkaline protease under alkaline conditions to make the enzyme activity 60,000 U / L to 100,000 U / L, performing an enzymatic hydrolysis reaction at 45°C to 55°C for 2h to 4h, centrifuging, collecting the precipitate, and obtaining the deproteinized β-glucan; the alkaline conditions are pH 9 to 11.

3. The method for preparing yeast nano β-glucan dry powder according to claim 1, characterized in that: The vacuum concentration is to concentrate the high-pressure homogenized and crushed beta-glucan to 20% to 30% of the original volume at 55° C. to 65° C. and a vacuum degree of 0.08 MPa to 0.1 MPa to obtain a beta-glucan concentrated solution.

4. The method for preparing yeast nano β-glucan dry powder according to claim 1, characterized in that: The vacuum drying comprises spreading the β-glucan concentrate on a tray with a thickness of 0.7 cm to 0.9 cm, applying a vacuum degree of 0.08 MPa to 0.1 MPa, and drying at a temperature of 55° C. to 65° C. for 2 to 4 hours. After drying, the concentrate is crushed and passed through a 200-mesh sieve to obtain nano β-glucan dry powder with a particle size of less than 100 nm.

5. The method for preparing yeast nano β-glucan dry powder according to claim 1, characterized in that: The specific method for obtaining yeast cell walls by autolyzing yeast cells is as follows: active dry yeast powder is prepared into a yeast cell suspension with water, the pH value is adjusted to 5.0-6.0, 400U / mL-500U / mL papain is added, the suspension is allowed to stand at 50-55°C for 30-42 hours to autolyze the yeast cell walls, the suspension is centrifuged, the precipitate is collected, and the precipitate is washed with water to obtain the autolyzed yeast cell walls; the specific method for obtaining yeast β-glucan by high-temperature extraction is as follows: the autolyzed yeast cell walls are prepared into a suspension with water, the suspension is placed in a high-pressure steam sterilizer, the suspension is subjected to high-temperature treatment at 115-125°C for 6-10 hours, the suspension is centrifuged, the precipitate is collected, and the precipitate is washed with water to obtain the yeast β-glucan.

6. An application of yeast nano β-glucan dry powder, wherein the yeast nano β-glucan dry powder is prepared according to any one of claims 1 to 5, characterized in that: The prepared nanometer beta-glucan dry powder is used as a functional food ingredient or as a food additive.

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