Preparation method of low-molecular-weight sodium polyglutamate based on multi-energy-level electron beam irradiation

Abstract

The invention relates to a preparation method of low-molecular-weight sodium polyglutamate based on multi-energy-level electron beam irradiation. Comprising the following steps: (1) preparing a sodium polyglutamate aqueous solution; (2) performing first energy level electron beam irradiation on the sodium polyglutamate aqueous solution to obtain the sodium polyglutamate aqueous solution after primary irradiation; (3) adding peracetic acid and hydrogen peroxide into the poly (sodium glutamate) aqueous solution subjected to primary irradiation, and carrying out second energy level electron beam irradiation to obtain a poly (sodium glutamate) aqueous solution subjected to secondary irradiation; and (4) adjusting the pH value of the secondarily irradiated sodium polyglutamate aqueous solution, and carrying out vacuum freeze drying to obtain the low-molecular-weight sodium polyglutamate. The invention provides a method for degrading high-molecular sodium polyglutamate by adopting peracetic acid and hydrogen peroxide as auxiliary agents and combining secondary electron beam irradiation for the first time. The average relative molecular weight of the prepared sodium polyglutamate is 2000-4000 Da, the use requirements of various fields are met, and the molecular weight is uniform.

Description

Technical Field

[0001] The invention relates to a method for preparing low molecular weight sodium polyglutamate based on multi-energy level electron beam irradiation, belonging to the technical field of high molecular polymer degradation. Background Art

[0002] Polyglutamic acid (PGA) is a high molecular weight amino acid polymer formed by glutamic acid molecules connected by peptide bonds. It is a natural polypeptide. The structural characteristic of polyglutamic acid is that the glutamic acid molecules are connected to each other by amide bonds to form a linear or branched structure. The molecular weight is generally 10 to 1000 kDa. Low molecular weight PGA has higher biological activity, high permeability and easy absorption than high molecular weight PGA, and has good application development value.

[0003] The smaller the molecular weight, the smaller the degree of polymerization, and the higher the biological activity. Therefore, with different relative molecular weights, the performance varies greatly, and the application fields are also different. Polyglutamic acid has a very strong moisturizing effect, which can enhance skin elasticity, improve skin smoothness, long-term moisturizing, and anti-wrinkle. This makes it widely used in the cosmetics field. Among them, low molecular weight sodium polyglutamate has good transdermal absorption and can better play a role in skin care.

[0004] The degradation methods of sodium polyglutamate (PGA-Na) mainly include physical degradation, chemical degradation and bio-enzyme degradation, including acid-thermal hydrolysis, alkaline-thermal hydrolysis, ultrasonic degradation and enzymatic hydrolysis, etc. The chemical degradation method mainly hydrolyzes PGA by adding acid (HCl) or alkali (NaOH). Although the hydrolysis efficiency is high, the introduction of exogenous chemical reagents affects the properties of PGA, increases the difficulty of product purification, and is easy to pollute the environment.

[0005] At present, the degradation of sodium polyglutamate mostly adopts the bioenzyme method. For example, Chinese patent document CN104805143A discloses a method for preparing low molecular weight γ-polyglutamic acid. It first adjusts the pH value of the fermentation liquid to 3.5-4.0, the temperature is 75-100°C, and the temperature is kept for degradation for 4-8 hours to obtain low molecular weight γ-polyglutamic acid with a molecular weight range of 10KDa-500KDa; when the temperature drops to 0-60°C, add activated carbon for decolorization, plate and frame filtration, remove bacteria, activated carbon and impurities, and obtain a clear and colorless liquid; the liquid is adjusted to pH 1.5-3.0 with hydrochloric acid, and allowed to stand for 12-24 hours to precipitate; the white powder is added to purified water, and the pH is adjusted to 4.5-6.5, stirred and dissolved to obtain a solution with a concentration of more than 40%; then the low molecular weight γ-polyglutamic acid product is obtained through belt drying and crushing. However, the degradation efficiency of polyglutamic acid degradation enzyme in the bioenzymatic method is low, and the required temperature, acidity, alkalinity, enzyme addition and other conditions are relatively strict, requiring a lot of process exploration, and it is difficult to achieve large-scale industrial production. At the same time, it is easy to cause enzyme residues, which leads to excessive protein content in the raw materials, and there are problems such as excessive protein content in the raw materials caused by residues after enzymolysis. Therefore, there is an urgent need for a method with good degradation efficiency to degrade sodium polyglutamate in batches without introducing other impurities. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for preparing low molecular weight sodium polyglutamate based on multi-energy level electron beam irradiation.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing low molecular weight sodium polyglutamate based on multi-level electron beam irradiation comprises the following steps:

[0009] (1) dissolving high molecular weight sodium polyglutamate in water to obtain a sodium polyglutamate aqueous solution;

[0010] (2) maintaining the liquid layer thickness of the sodium polyglutamate aqueous solution obtained in step (1) at 3 to 5 cm, and irradiating the sodium polyglutamate aqueous solution with a first energy level electron beam to obtain a primary irradiated sodium polyglutamate aqueous solution;

[0011] (3) adding peracetic acid and hydrogen peroxide to the sodium polyglutamate aqueous solution after primary irradiation obtained in step (2), stirring and mixing evenly to obtain a mixed solution; then maintaining the liquid layer thickness of the mixed solution at 3 to 6 cm, performing a second energy level electron beam irradiation to obtain a sodium polyglutamate aqueous solution after secondary irradiation;

[0012] (4) adjusting the pH of the sodium polyglutamate aqueous solution after secondary irradiation obtained in step (3), and then performing vacuum freeze drying to obtain low molecular weight sodium polyglutamate.

[0013] According to a preferred embodiment of the present invention, in step (1), the average relative molecular weight of the high molecular weight sodium polyglutamate is 200000-400000 Da. According to a preferred embodiment of the present invention, in step (1), the mass concentration of the sodium polyglutamate aqueous solution is 0.02-0.2%.

[0014] Further preferably, the mass concentration of the sodium polyglutamate aqueous solution is 0.05%.

[0015] Preferably according to the present invention, in step (2), the thickness of the liquid layer is 2.5 to 3.5 cm.

[0016] Preferably, according to the present invention, in step (2), the parameters of the first energy level electron beam irradiation are: electron beam energy 8-12 MeV, power 15-20 kW, frequency 350-450 Hz, under-beam transmission chain speed 1-1.5 m / min, and a single dose of 12-15 KGy.

[0017] Further preferably, the parameters of the first energy level electron beam irradiation are: electron beam energy 10 MeV, power 18 kW, frequency 400 Hz, under-beam transmission chain speed 1.3 m / min, and single dose 15 KGy.

[0018] Preferably according to the present invention, in step (3), the mass concentration of peracetic acid in the mixed solution is 0.005-0.015%, and the mass concentration of hydrogen peroxide is 3-5%.

[0019] Further preferably, the mass concentration of peracetic acid in the mixed solution is 0.01%, and the mass concentration of hydrogen peroxide is 4%.

[0020] Preferably according to the present invention, in step (3), the thickness of the liquid layer is 4.5 to 5.5 cm.

[0021] Preferably, according to the present invention, in step (3), the parameters of the second energy level electron beam irradiation are: electron beam energy 8-12 MeV, power 15-20 kW, frequency 350-450 Hz, under-beam transmission chain speed 1-1.5 m / min, and a single dose of 10-12 KGy.

[0022] Further preferably, the parameters of the second energy level electron beam irradiation are: electron beam energy 10 MeV, power 18 kW, frequency 400 Hz, under-beam transmission chain speed 1.5 m / min, and single dose 12 KGy.

[0023] Preferably, according to the present invention, in step (4), adjusting the pH value refers to adjusting the pH value to 7.0-7.5 using a NaOH solution with a mass concentration of 0.5%.

[0024] Preferably, according to the present invention, in step (4), the vacuum freeze drying is specifically:

[0025] The sodium polyglutamate aqueous solution after the secondary irradiation was placed in a freeze dryer, the freeze dryer was turned on, and the freeze drying chamber temperature was adjusted to -30.0°C for 3.5 hours;

[0026] Adjust the temperature of the freeze drying chamber to -15.0℃ and maintain it for 45min; adjust the temperature of the freeze drying chamber to -10.0℃ and maintain it for 2h; start vacuuming with a vacuum degree of 55Pa;

[0027] Continue to adjust the temperature of the freezing chamber to -2°C and maintain it for 7 hours; adjust the temperature of the freeze drying chamber to 0°C and maintain it for 3 hours, and maintain the vacuum degree at 55Pa;

[0028] Continue to adjust the temperature of the freezing chamber to 10°C and maintain it for 0.8h; adjust the temperature of the freeze drying chamber to 15°C and maintain it for 1.5h, and maintain the vacuum degree at 55Pa;

[0029] Continue to adjust the temperature of the freezing chamber to 20°C and maintain it for 2 hours; adjust the temperature of the freeze drying chamber to 35°C and maintain it for 4 hours, and maintain the vacuum degree at 15Pa;

[0030] Turn off the freeze dryer, adjust the freeze drying room environment to normal pressure, and take out the low molecular weight sodium polyglutamate.

[0031] The technical features of the present invention are as follows:

[0032] In order to develop and prepare low molecular weight sodium polyglutamate, the inventors of the present application conducted a large amount of basic research. In an experiment, they unexpectedly discovered that electron beam irradiation can not only promote the cross-linking of sodium polyglutamate, but also degrade the high molecular weight sodium polyglutamate by adding auxiliary agents during multiple electron beam irradiations, thus proposing a new method for the preparation of low molecular weight sodium polyglutamate.

[0033] The specific degradation mechanism is inferred as follows: the high-energy electron beam interacts with the polymer molecular chain, breaks the chemical bonds in the polymer molecular chain, and produces a large number of highly reactive transition particles, mainly free radical ions, secondary electrons, and high-energy particles. Under low concentration conditions, some free radical ions react with Na + The corresponding salts are formed by the action, and a small part of them are cross-linked. Since most of the sodium polyglutamate is in a spiral-random curl, random curl and winding structure, the free radical polymerization structure is unstable, and a physical bonding point is formed under the action of the electron beam. It is easy to break during stirring or long-term placement. The auxiliary agent is conducive to the breakage of the chemical bonds of the polymer structure itself under a relatively low irradiation dose, forming corresponding free radicals, and forming corresponding acids in the acidic environment of the auxiliary agent. After irradiation, the pH is adjusted to form stable low-molecular sodium polyglutamate, thereby forming small-molecule sodium polyglutamate.

[0034] In the preparation method of the present invention, the concentration of the polymer sodium polyglutamate solution, the addition of auxiliary agents and the parameters of electron beam irradiation are three key factors. First, the concentration of the polymer sodium polyglutamate solution can only be degraded by electron beam irradiation when it is within a certain range. When the concentration of the polymer sodium polyglutamate solution is too high, the probability of cross-linking of the polymer sodium polyglutamate under electron beam irradiation increases. Second, only when a specific concentration of auxiliary agents (peracetic acid and hydrogen peroxide) is added during multiple electron beam irradiations can the polymer sodium polyglutamate be degraded. Third, the parameters of electron beam irradiation can only degrade the polymer sodium polyglutamate when it is within a certain range. When the irradiation dose is too large, the polymer sodium polyglutamate will be cross-linked or even partially degraded, resulting in uncontrollable molecular weight. When the irradiation dose is too small, it is not enough to provide the energy required for degradation.

[0035] Beneficial effects:

[0036] 1. The present invention proposes for the first time a method for preparing low molecular weight sodium polyglutamate by multi-level electron beam irradiation, using peracetic acid and hydrogen peroxide as auxiliary agents, combined with secondary electron beam irradiation to degrade high molecular weight sodium polyglutamate. Compared with the physical degradation, chemical degradation and bio-enzyme degradation methods in the prior art, there is no need to use expensive instruments to adjust the physical degradation temperature, nor to add enzymes, and the average relative molecular weight of the prepared sodium polyglutamate is 2000-4000Da, which meets the use requirements of various fields, and the molecular weight is uniform.

[0037] 2. The auxiliary agent in the method for preparing low molecular weight sodium polyglutamate of the present invention can volatilize during the freeze-drying process, and no additional process is required for removal. The operation is simple, easy to control, and pollution-free. The preparation of low molecular weight sodium polyglutamate by secondary energy level irradiation with the aid of auxiliary agents avoids the destructiveness of the one-time high energy level to the substantial structure of high molecular weight sodium polyglutamate, reduces the severity of the reaction, shortens the degradation time, ensures the structure and biological activity of sodium polyglutamate, and is suitable for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the GPC chromatogram of the low molecular weight sodium polyglutamate prepared in Example 1.

[0039] Figure 2 This is a real photo of the low molecular weight sodium polyglutamate prepared in Example 1.

[0040] Figure 3 This is the GPC chromatogram of sodium polyglutamate prepared in Comparative Example 1.

[0041] Figure 4 This is the GPC chromatogram of sodium polyglutamate prepared in Comparative Example 2.

[0042] Figure 5This is the GPC chromatogram of sodium polyglutamate prepared in Comparative Example 3. DETAILED DESCRIPTION

[0043] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing low molecular weight sodium polyglutamate based on multi-level electron beam irradiation comprises the following steps:

[0046] (1) 5.0g average relative molecular weight Mw (g / mol) is 3.34452×10 5 The high molecular weight sodium polyglutamate is dissolved in water to obtain a sodium polyglutamate aqueous solution with a mass concentration of 0.05%;

[0047] (2) filling the sodium polyglutamate aqueous solution obtained in step (1) into a sterile storage bag, maintaining the liquid layer thickness at 3 cm, and performing first energy level electron beam irradiation under the conditions of electron beam energy of 10 MeV, power of 18 kW, frequency of 400 Hz, transmission chain speed of 1.3 m / min under the beam, and single dose of 15 KGy to obtain a sodium polyglutamate aqueous solution after primary irradiation;

[0048] (3) transferring the sodium polyglutamate aqueous solution after primary irradiation obtained in step (2) to a large beaker, adding peracetic acid and 37% hydrogen peroxide to the sodium polyglutamate aqueous solution after primary irradiation, stirring and mixing to obtain a mixed solution, wherein the mass concentration of peracetic acid in the mixed solution is 0.01%, and the mass concentration of hydrogen peroxide is 4%; then filling it again into a sterile storage bag, maintaining the liquid layer thickness of the mixed solution to be 5 cm, and performing a second energy level electron beam irradiation under the conditions of an electron beam energy of 10 MeV, a power of 18 kW, a frequency of 400 Hz, a transmission chain speed of 1.3 m / min under the beam, and a single dose of 12 KGy to obtain a sodium polyglutamate aqueous solution after secondary irradiation;

[0049] (4) adjusting the pH value of the sodium polyglutamate aqueous solution after secondary irradiation obtained in step (3) to 7.3 using a 0.5% NaOH solution, and placing the solution in a freeze dryer for vacuum freeze drying to obtain low molecular weight sodium polyglutamate;

[0050] Wherein, the vacuum freeze drying is specifically:

[0051] The sodium polyglutamate aqueous solution after secondary irradiation (pH adjusted to 7.3) was placed in a freeze dryer, the freeze dryer was turned on, and the freeze drying chamber temperature was adjusted to -30.0°C for 3.5 hours;

[0052] Adjust the temperature of the freeze drying chamber to -15.0℃ and maintain it for 45min; adjust the temperature of the freeze drying chamber to -10.0℃ and maintain it for 2h; start vacuuming with a vacuum degree of 55Pa;

[0053] Continue to adjust the temperature of the freezing chamber to -2°C and maintain it for 7 hours; adjust the temperature of the freeze drying chamber to 0°C and maintain it for 3 hours, and maintain the vacuum degree at 55Pa;

[0054] Continue to adjust the temperature of the freezing chamber to 10°C and maintain it for 0.8h; adjust the temperature of the freeze drying chamber to 15°C and maintain it for 1.5h, and maintain the vacuum degree at 55Pa;

[0055] Continue to adjust the temperature of the freezing chamber to 20°C and maintain it for 2 hours; adjust the temperature of the freeze drying chamber to 35°C and maintain it for 4 hours, and maintain the vacuum degree at 15Pa;

[0056] Turn off the freeze dryer, adjust the freeze drying room environment to normal pressure, and take out the low molecular weight sodium polyglutamate.

[0057] Example 2

[0058] A method for preparing low molecular weight sodium polyglutamate based on multi-level electron beam irradiation comprises the following steps:

[0059] (1) 5.0g average relative molecular weight Mw (g / mol) is 3.34452×10 5 The high molecular weight sodium polyglutamate is dissolved in water to obtain a sodium polyglutamate aqueous solution with a mass concentration of 0.02%;

[0060] (2) filling the sodium polyglutamate aqueous solution obtained in step (1) into a sterile storage bag, maintaining the liquid layer thickness at 3 cm, and performing first energy level electron beam irradiation under the conditions of electron beam energy 8 MeV, power 15 kW, frequency 350 Hz, under-beam transmission chain speed 1 m / min, and single dose 12 KGy to obtain a sodium polyglutamate aqueous solution after primary irradiation;

[0061] (3) transferring the sodium polyglutamate aqueous solution after primary irradiation obtained in step (2) to a large beaker, adding peracetic acid and 37% hydrogen peroxide to the sodium polyglutamate aqueous solution after primary irradiation, stirring and mixing to obtain a mixed solution, wherein the mass concentration of peracetic acid in the mixed solution is 0.005%, and the mass concentration of hydrogen peroxide is 3%; then filling it again into a sterile storage bag, maintaining the liquid layer thickness of the mixed solution to be 5 cm, and performing a second energy level electron beam irradiation under the conditions of electron beam energy 8 MeV, power 15 kW, frequency 350 Hz, beam transmission chain speed 1 m / min, and single dose 10 KGy to obtain a sodium polyglutamate aqueous solution after secondary irradiation;

[0062] (4) adjusting the pH value of the sodium polyglutamate aqueous solution after secondary irradiation obtained in step (3) to 7.4 using a 0.5% NaOH solution, and placing the solution in a freeze dryer for vacuum freeze drying to obtain low molecular weight sodium polyglutamate.

[0063] Wherein, the vacuum freeze drying is specifically:

[0064] The sodium polyglutamate aqueous solution after secondary irradiation (pH adjusted to 7.4) was placed in a freeze dryer, the freeze dryer was turned on, and the freeze drying chamber temperature was adjusted to -30.0°C for 3.5 hours;

[0065] Adjust the temperature of the freeze drying chamber to -15.0℃ and maintain it for 45min; adjust the temperature of the freeze drying chamber to -10.0℃ and maintain it for 2h; start vacuuming with a vacuum degree of 55Pa;

[0066] Continue to adjust the temperature of the freezing chamber to -2°C and maintain it for 7 hours; adjust the temperature of the freeze drying chamber to 0°C and maintain it for 3 hours, and maintain the vacuum degree at 55Pa;

[0067] Continue to adjust the temperature of the freezing chamber to 10°C and maintain it for 0.8h; adjust the temperature of the freeze drying chamber to 15°C and maintain it for 1.5h, and maintain the vacuum degree at 55Pa;

[0068] Continue to adjust the temperature of the freezing chamber to 20°C and maintain it for 2 hours; adjust the temperature of the freeze drying chamber to 35°C and maintain it for 4 hours, and maintain the vacuum degree at 15Pa;

[0069] Turn off the freeze dryer, adjust the freeze drying room environment to normal pressure, and take out the low molecular weight sodium polyglutamate.

[0070] Example 3

[0071] A method for preparing low molecular weight sodium polyglutamate based on multi-level electron beam irradiation comprises the following steps:

[0072] (1) 5.0g average relative molecular weight Mw (g / mol) is 3.34452×105 The high molecular weight sodium polyglutamate is dissolved in water to obtain a sodium polyglutamate aqueous solution with a mass concentration of 0.2%;

[0073] (2) filling the sodium polyglutamate aqueous solution obtained in step (1) into a sterile storage bag, maintaining the liquid layer thickness at 3 cm, and performing first energy level electron beam irradiation under the conditions of electron beam energy of 12 MeV, power of 20 kW, frequency of 450 Hz, transmission chain speed of 1.5 m / min under the beam, and single dose of 15 KGy to obtain a sodium polyglutamate aqueous solution after primary irradiation;

[0074] (3) transferring the sodium polyglutamate aqueous solution after primary irradiation obtained in step (2) to a large beaker, adding peracetic acid and 37% hydrogen peroxide to the sodium polyglutamate aqueous solution after primary irradiation, stirring and mixing to obtain a mixed solution, wherein the mass concentration of peracetic acid in the mixed solution is 0.015%, and the mass concentration of hydrogen peroxide is 5%; then filling it again into a sterile storage bag, maintaining the liquid layer thickness of the mixed solution to be 5 cm, and performing a second energy level electron beam irradiation under the conditions of an electron beam energy of 12 MeV, a power of 20 kW, a frequency of 450 Hz, a transmission chain speed of 1.5 m / min under the beam, and a single dose of 12 KGy to obtain a sodium polyglutamate aqueous solution after secondary irradiation;

[0075] (4) adjusting the pH value of the sodium polyglutamate aqueous solution after secondary irradiation obtained in step (3) to 7.4 using a 0.5% NaOH solution, and placing the solution in a freeze dryer for vacuum freeze drying to obtain low molecular weight sodium polyglutamate;

[0076] Wherein, the vacuum freeze drying is specifically:

[0077] The sodium polyglutamate aqueous solution after secondary irradiation (pH adjusted to 7.4) was placed in a freeze dryer, the freeze dryer was turned on, and the freeze drying chamber temperature was adjusted to -30.0°C for 3.5 hours;

[0078] Adjust the temperature of the freeze drying chamber to -15.0℃ and maintain it for 45min; adjust the temperature of the freeze drying chamber to -10.0℃ and maintain it for 2h; start vacuuming with a vacuum degree of 55Pa;

[0079] Continue to adjust the temperature of the freezing chamber to -2°C and maintain it for 7 hours; adjust the temperature of the freeze drying chamber to 0°C and maintain it for 3 hours, and maintain the vacuum degree at 55Pa;

[0080] Continue to adjust the temperature of the freezing chamber to 10°C and maintain it for 0.8h; adjust the temperature of the freeze drying chamber to 15°C and maintain it for 1.5h, and maintain the vacuum degree at 55Pa;

[0081] Continue to adjust the temperature of the freezing chamber to 20°C and maintain it for 2 hours; adjust the temperature of the freeze drying chamber to 35°C and maintain it for 4 hours, and maintain the vacuum degree at 15Pa;

[0082] Turn off the freeze dryer, adjust the freeze drying room environment to normal pressure, and take out the low molecular weight sodium polyglutamate.

[0083] Comparative Example 1

[0084] A method for preparing low molecular weight sodium polyglutamate comprises the following steps:

[0085] (1) 30.0g average relative molecular weight Mw (g / mol) is 3.34452×10 5 The high molecular weight sodium polyglutamate is dissolved in water to obtain a sodium polyglutamate aqueous solution with a mass concentration of 1.2%;

[0086] (2) filling the sodium polyglutamate aqueous solution obtained in step (1) into a sterile storage bag, maintaining the liquid layer thickness at 4 cm, and performing first energy level electron beam irradiation under the conditions of electron beam energy of 12 MeV, power of 20 kW, frequency of 450 Hz, transmission chain speed of 1.5 m / min under the beam, and single dose of 15 KGy to obtain a sodium polyglutamate aqueous solution after primary irradiation;

[0087] (3) transferring the sodium polyglutamate aqueous solution after primary irradiation obtained in step (2) to a large beaker, adding peracetic acid and 37% hydrogen peroxide to the sodium polyglutamate aqueous solution after primary irradiation, stirring and mixing uniformly to obtain a mixed solution, wherein the mass concentration of peracetic acid in the mixed solution is 0.015%, and the mass concentration of hydrogen peroxide is 5%; then filling it again into a sterile storage bag, maintaining the liquid layer thickness of the mixed solution to be 5 cm, and performing a second energy level electron beam irradiation under the conditions of an electron beam energy of 12 MeV, a power of 20 kW, a frequency of 450 Hz, a transmission chain speed of 1.5 m / min under the beam, and a single dose of 5 KGy to obtain a sodium polyglutamate aqueous solution after secondary irradiation;

[0088] (4) adjusting the pH value of the sodium polyglutamate aqueous solution after secondary irradiation obtained in step (3) to 7.3 using a 0.5% NaOH solution, and placing the solution in a freeze dryer for vacuum freeze drying to obtain low molecular weight sodium polyglutamate;

[0089] Wherein, the vacuum freeze drying is specifically:

[0090] The sodium polyglutamate aqueous solution (pH adjusted to 7.3) after secondary irradiation and pH adjustment was placed in a freeze dryer, the freeze dryer was turned on, and the freeze drying chamber temperature was adjusted to -30.0°C for 3.5 hours;

[0091] Adjust the temperature of the freeze drying chamber to -15.0℃ and maintain it for 45min; adjust the temperature of the freeze drying chamber to -10.0℃ and maintain it for 2h; start vacuuming with a vacuum degree of 55Pa;

[0092] Continue to adjust the temperature of the freezing chamber to -2°C and maintain it for 7 hours; adjust the temperature of the freeze drying chamber to 0°C and maintain it for 3 hours, and maintain the vacuum degree at 55Pa;

[0093] Continue to adjust the temperature of the freezing chamber to 10°C and maintain it for 0.8h; adjust the temperature of the freeze drying chamber to 15°C and maintain it for 1.5h, and maintain the vacuum degree at 55Pa;

[0094] Continue to adjust the temperature of the freezing chamber to 20°C and maintain it for 2 hours; adjust the temperature of the freeze drying chamber to 35°C and maintain it for 4 hours, and maintain the vacuum degree at 15Pa;

[0095] Turn off the freeze dryer, adjust the freeze drying room environment to normal pressure, and take out sodium polyglutamate.

[0096] Comparative Example 2

[0097] A method for preparing low molecular weight sodium polyglutamate comprises the following steps:

[0098] (1) 5.0g average relative molecular weight Mw (g / mol) is 3.34452×10 5 The high molecular weight sodium polyglutamate is dissolved in water to obtain a sodium polyglutamate aqueous solution with a mass concentration of 0.2%;

[0099] (2) filling the sodium polyglutamate aqueous solution obtained in step (1) into a sterile storage bag, maintaining the liquid layer thickness at 3 cm, and performing first energy level electron beam irradiation under the conditions of electron beam energy of 10 MeV, power of 18 kW, frequency of 400 Hz, transmission chain speed of 1.3 m / min under the beam, and single dose of 15 KGy to obtain a sodium polyglutamate aqueous solution after primary irradiation;

[0100] (3) placing the sodium polyglutamate aqueous solution obtained in step (2) after primary irradiation into a freeze dryer for vacuum freeze drying, wherein the vacuum freeze drying parameters are the same as those in Example 1, to obtain low molecular weight sodium polyglutamate.

[0101] Comparative Example 3

[0102] A method for preparing low molecular weight sodium polyglutamate comprises the following steps:

[0103] (1) 5.0g average relative molecular weight Mw (g / mol) is 3.34452×10 5 The high molecular weight sodium polyglutamate is dissolved in water to obtain a sodium polyglutamate aqueous solution with a mass concentration of 0.2%;

[0104] (2) filling the sodium polyglutamate aqueous solution obtained in step (1) into a sterile storage bag, maintaining the liquid layer thickness at 3 cm, and performing first energy level electron beam irradiation under the conditions of electron beam energy of 10 MeV, power of 18 kW, frequency of 400 Hz, transmission chain speed of 1.3 m / min under the beam, and single dose of 15 KGy to obtain a sodium polyglutamate aqueous solution after primary irradiation;

[0105] (3) The sodium polyglutamate aqueous solution after primary irradiation obtained in step (2) was transferred to a large beaker, and the pH value was adjusted to 7.4. The sodium polyglutamate aqueous solution after primary irradiation was added with water in an amount equal to that of peracetic acid and 37% hydrogen peroxide in Example 1, and stirred and mixed evenly; then the solution was filled into a sterile storage bag again, and the liquid layer thickness of the mixed solution was maintained at 5 cm. The sodium polyglutamate aqueous solution after secondary irradiation was obtained under the conditions of electron beam energy of 10 MeV, power of 18 kW, frequency of 400 Hz, transmission chain speed of 1.3 m / min, and single dose of 12 KGy.

[0106] (4) placing the sodium polyglutamate aqueous solution after primary irradiation obtained in step (3) into a freeze dryer for vacuum freeze drying, wherein the vacuum freeze drying parameters are the same as those in Example 1, to obtain low molecular weight sodium polyglutamate.

[0107] Test example

[0108] The low molecular weight sodium polyglutamate prepared in Example 1 and Comparative Examples 1 to 3 was dissolved in purified water, and the average relative molecular weight of the low molecular weight sodium polyglutamate prepared in Example 1 and Comparative Examples 1 to 3 was determined by gel chromatography. The GPC chromatogram of the low molecular weight sodium polyglutamate prepared in Example 1 is as shown in FIG. Figure 1 As shown, the actual photo of the low molecular weight sodium polyglutamate prepared in Example 1 is as shown in Figure 2 As shown, the GPC chromatogram of sodium polyglutamate prepared in Comparative Example 1 is as shown Figure 3 As shown, the GPC chromatogram of sodium polyglutamate prepared in Comparative Example 2 is as follows Figure 4 As shown, the GPC chromatogram of sodium polyglutamate prepared in Comparative Example 3 is as follows Figure 5 shown.

[0109] Depend on Figure 1 and Figure 2 It can be seen that the low molecular weight sodium polyglutamate prepared in Example 1 is a milky white fluffy powder with an average relative molecular weight of 2619.

[0110] Depend on Figures 3 to 5 It can be seen that the average molecular weight of the sodium polyglutamate prepared in Comparative Example 2 is 200342, the average relative molecular weight of the low molecular weight sodium polyglutamate prepared in Comparative Example 1 is 63877, and the average relative molecular weight of the low molecular weight sodium polyglutamate prepared in Comparative Example 2 is 13391.

[0111] It can be seen from the above data that in the preparation method of the present invention, the concentration of the high molecular sodium polyglutamate solution, the addition of the auxiliary agent and the parameters of the electron beam irradiation are three key factors. First, the concentration of the high molecular sodium polyglutamate solution can be degraded by electron beam irradiation within a certain range. When the concentration of the high molecular sodium polyglutamate solution is too high, the cross-linking probability of the high molecular sodium polyglutamate under electron beam irradiation increases. Second, only by adding auxiliary agents (peracetic acid and hydrogen peroxide) of a specific concentration during multiple electron beam irradiations can the high molecular sodium polyglutamate be degraded. Third, the parameters of the electron beam irradiation can degrade the high molecular sodium polyglutamate within a certain range. When the irradiation dose is too large, the high molecular sodium polyglutamate will be cross-linked, even partially degraded, resulting in uncontrollable molecular weight. When the irradiation dose is too small, it is not enough to provide the energy required for degradation. Only by using peracetic acid and hydrogen peroxide as auxiliary agents and degrading the high molecular sodium polyglutamate by secondary electron beam irradiation can the low molecular weight sodium polyglutamate with an average relative molecular weight of 2000-4000Da be prepared.

[0112] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing low molecular weight sodium polyglutamate based on multi-level electron beam irradiation, characterized in that: The steps include: (1) dissolving high molecular weight sodium polyglutamate in water to obtain a sodium polyglutamate aqueous solution; (2) maintaining the liquid layer thickness of the sodium polyglutamate aqueous solution obtained in step (1) at 3 to 5 cm, and irradiating the sodium polyglutamate aqueous solution with a first energy level electron beam to obtain a primary irradiated sodium polyglutamate aqueous solution; (3) adding peracetic acid and hydrogen peroxide to the sodium polyglutamate aqueous solution after primary irradiation obtained in step (2), stirring and mixing evenly to obtain a mixed solution; then maintaining the liquid layer thickness of the mixed solution at 3 to 6 cm, performing a second energy level electron beam irradiation to obtain a sodium polyglutamate aqueous solution after secondary irradiation; (4) adjusting the pH of the sodium polyglutamate aqueous solution after secondary irradiation obtained in step (3), and then performing vacuum freeze drying to obtain low molecular weight sodium polyglutamate.

2. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein In step (1), the average relative molecular weight of the high molecular weight sodium polyglutamate is 200,000 to 400,000 Da.

3. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein In step (1), the mass concentration of the sodium polyglutamate aqueous solution is 0.02-0.2%; Further preferably, the mass concentration of the sodium polyglutamate aqueous solution is 0.05%.

4. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein In step (2), the thickness of the liquid layer is 2.5 to 3.5 cm.

5. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein In step (2), the parameters of the first energy level electron beam irradiation are: electron beam energy 8-12 MeV, power 15-20 kW, frequency 350-450 Hz, under-beam transmission chain speed 1-1.5 m / min, and single dose 12-15 KGy; Further preferably, the parameters of the first energy level electron beam irradiation are: electron beam energy 10 MeV, power 18 kW, frequency 400 Hz, under-beam transmission chain speed 1.3 m / min, and single dose 15 KGy.

6. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein: In step (3), the mass concentration of peracetic acid in the mixed solution is 0.005-0.015%, and the mass concentration of hydrogen peroxide is 3-5%; Further preferably, the mass concentration of peracetic acid in the mixed solution is 0.01%, and the mass concentration of hydrogen peroxide is 4%.

7. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein: In step (3), the thickness of the liquid layer is 4.5 to 5.5 cm.

8. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein: In step (3), the parameters of the second energy level electron beam irradiation are: electron beam energy 8-12 MeV, power 15-20 kW, frequency 350-450 Hz, under-beam transmission chain speed 1-1.5 m / min, and single dose 10-12 KGy; Further preferably, the parameters of the second energy level electron beam irradiation are: electron beam energy 10 MeV, power 18 kW, frequency 400 Hz, under-beam transmission chain speed 1.5 m / min, and single dose 12 KGy.

9. The method for preparing low molecular weight sodium polyglutamate according to claim 1, wherein In step (4), adjusting the pH value refers to adjusting the pH value to 7.0-7.5 using a NaOH solution with a mass concentration of 0.5%.

10. The method for preparing low molecular weight sodium polyglutamate according to claim 1, characterized in that: In step (4), the vacuum freeze-drying is specifically: The sodium polyglutamate aqueous solution after the secondary irradiation was placed in a freeze dryer, the freeze dryer was turned on, and the temperature of the freeze drying chamber was adjusted to -30.0°C for 3.5 hours; Adjust the temperature of the freeze drying chamber to -15.0℃ and maintain it for 45min; adjust the temperature of the freeze drying chamber to -10.0℃ and maintain it for 2h; start vacuuming with a vacuum degree of 55Pa; Continue to adjust the temperature of the freezing chamber to -2°C and maintain it for 7 hours; adjust the temperature of the freeze drying chamber to 0°C and maintain it for 3 hours, and maintain the vacuum degree at 55Pa; Continue to adjust the temperature of the freezing chamber to 10°C and maintain it for 0.8h; adjust the temperature of the freeze drying chamber to 15°C and maintain it for 1.5h, and maintain the vacuum degree at 55Pa; Continue to adjust the temperature of the freezing chamber to 20°C and maintain it for 2 hours; adjust the temperature of the freeze drying chamber to 35°C and maintain it for 4 hours, and maintain the vacuum degree at 15Pa; Turn off the freeze dryer, adjust the freeze drying room environment to normal pressure, and take out the low molecular weight sodium polyglutamate.

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