Preparation method for extracting mannose based on birch

Abstract

The invention provides a preparation method for extracting mannose based on birch, which comprises the following steps: crushing birch raw materials into small particles, mixing the small particles with modified 1-butyl-3-methylimidazolium hexafluorophosphate after enzymolysis, and extracting under a stirring condition; after the extraction is completed, recovering the ionic liquid through a membrane separation technology; cooling the extracting solution, crystallizing and separating out mannose, and separating and purifying the crystallized mannose by utilizing a high performance liquid chromatography; and finally, drying the purified mannose solution to obtain solid mannose. According to the method, the extraction rate and purity of mannose are remarkably improved, the extraction rate reaches 32.9%, the purity reaches 98.4%, and the method is environmentally friendly, efficient and wide in industrial application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of mannose, and in particular to a preparation method of mannose based on extracting birch. Background Art

[0002] Birch is a widely distributed tree species in the Northern Hemisphere. Its sap is rich in mannose. This polysaccharide is widely used in the food, pharmaceutical and cosmetic industries due to its excellent sweetness and low glycemic index. Traditional mannose extraction technology mainly relies on hot water or organic solvent extraction. Although these methods have been widely used in industry, they have problems such as low efficiency, high energy consumption, and solvent residue. In recent years, with the development of green chemistry, researchers have begun to explore more environmentally friendly and efficient extraction technologies. Against this background, mannose extraction technology has gradually developed in the direction of using green solvents and biotechnology.

[0003] The main deficiencies faced by the prior art in extracting mannose include low extraction efficiency, poor selectivity and environmental pollution. In particular, the use of traditional organic solvents not only consumes energy, but may also burden the environment. Chinese patent CN103338781A discloses a method for preparing fine powder of polymannos extract, using organic solvents for dissolution extraction, such as methanol, ethanol, isopropanol and propanol. Organic solvents may emit volatile organic compounds (VOCs) during the extraction process. These compounds are harmful to the environment and may cause air pollution and damage to the ecosystem. In this regard, the present invention proposes a new method for extracting mannose using green solvents such as ionic liquids. Ionic liquids, due to their flexible design and customizable chemical properties, can effectively dissolve a variety of biomacromolecules at room temperature without producing harmful volatiles, showing great potential in the extraction process. In addition, compared with traditional methods, the use of ionic liquids in the present invention can significantly improve the extraction rate and purity of mannose, reduce energy consumption and solvent usage, thereby achieving higher economic benefits and environmental friendliness. By optimizing the solvent system, not only can the selective extraction efficiency of mannose be improved, but it can also help protect and utilize natural resources and meet the requirements of sustainable development. Summary of the invention

[0004] The main drawbacks of the existing technologies for extracting mannose include low extraction efficiency, poor selectivity and environmental pollution, especially the use of traditional organic solvents, which not only consumes energy but also may cause a burden on the environment.

[0005] The present application provides a preparation method of mannose extracted from birch, comprising the following technical steps:

[0006] Step 1, crushing the birch raw material into small particles, the particle size of the particles ranges from 0.5 to 2 mm;

[0007] Step 2, preparing a citric acid-phosphate buffer solution, adjusting the pH to 4.8, and then soaking the birch particles in the buffer solution for 2 hours, then adding the birch particles to the buffer solution, and adding appropriate amounts of cellulase and hemicellulase; after the reaction is completed, heating to 90° C. for 10 minutes to terminate the enzymatic hydrolysis reaction, and then filtering the enzymatic hydrolysis product to separate the unenzymatic residue, and collecting the filtrate;

[0008] Step 3, mixing the filtrate with an ionic liquid and extracting under stirring conditions; wherein the ionic liquid is modified 1-butyl-3-methylimidazolium hexafluorophosphate;

[0009] Step 4, after the extraction is completed, recovering the ionic liquid by membrane separation technology;

[0010] Step 5, cooling the separated extract to allow mannose to crystallize, and then separating and purifying the crystallized mannose using high performance liquid chromatography;

[0011] Step 6, drying the purified mannose solution to obtain solid mannose.

[0012] It should be noted that crushing birch raw materials into small particles can significantly increase the surface area of ​​the raw materials, increase the contact area between the solvent and the plant cells, and thus enhance the extraction efficiency. Cellulase and hemicellulase are commonly used enzyme preparations, which can effectively decompose cellulose and hemicellulose in birch cell walls and increase the release rate of mannose. The activity of the enzyme is closely related to the pH value. Citric acid-phosphate buffer (pH 4.8) is a suitable reaction environment for cellulase and hemicellulase. Controlling at 50°C and a reaction time of 24 hours are common enzymatic hydrolysis conditions, which can be optimized according to actual conditions. Through the above enzymatic hydrolysis method, cellulose and hemicellulose in birch small particles can be effectively decomposed, releasing more mannose, and improving the efficiency of subsequent extraction and purification. Modified 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) has excellent solubility and selectivity, can effectively dissolve mannose and avoid the dissolution of excessive impurities. The extraction process under stirring conditions can promote full contact between the solvent and the filtrate, thereby improving the extraction efficiency of mannose. Membrane separation technology uses the selective permeability of semipermeable membranes to separate ionic liquids from other components in the extract. Ultrafiltration membranes or nanofiltration membranes can effectively recover ionic liquids from the extract. By controlling the operating pressure and flow rate, efficient separation and recovery can be ensured. The recovered ionic liquid can be used again in the extraction process, thereby reducing costs and reducing environmental pollution. Under low temperature conditions, the solubility of mannose decreases, causing it to crystallize out of the extract. By cooling the extract, preliminary crystallization of mannose can be obtained. Subsequently, the crystallized mannose is further purified by high performance liquid chromatography (HPLC). Low temperature drying methods (such as vacuum freeze drying or rotary evaporation) can effectively remove water from the mannose solution to obtain pure solid mannose. Low temperature drying can avoid thermal degradation of mannose by high temperature and maintain its chemical stability and purity. The dried mannose powder has good storage stability and application value.

[0013] As a preferred technical solution for a preparation method based on extracting mannose from birch, the mass ratio of the filtrate to the ionic liquid is 1:10 to 1:20.

[0014] It should be noted that the mass ratio of the filtrate to the ionic liquid is 1:10 to 1:20, which provides a sufficient amount of solvent to dissolve and extract more mannose while avoiding the waste of solvent.

[0015] As a preferred technical scheme for the preparation method based on extracting mannose from birch, the preparation steps of the modified 1-butyl-3-methylimidazolium hexafluorophosphate include: using 1-butyl-3-methylimidazolium hexafluorophosphate as a base material, adding malonic acid to 1-butyl-3-methylimidazolium hexafluorophosphate under stirring, heating the mixture to 80°C, reacting at this temperature for 3 hours, and cooling to room temperature to obtain carboxylated 1-butyl-3-methylimidazolium hexafluorophosphate.

[0016] It should be noted that by introducing carboxyl groups into [BMIM][PF6], its solubility and selectivity can be significantly improved, making it show higher extraction efficiency and purity in the mannose extraction process. The addition of malonic acid and the optimization of reaction conditions (stirring, heating, reaction time and cooling) ensure the effective progress of the modification reaction and the stability of the product. This modified ionic liquid not only has the excellent properties of the basic [BMIM][PF6], but also adds new functional properties, making it more efficient and environmentally friendly in practical applications.

[0017] As a preferred technical solution for the preparation method of mannose extracted from birch, the purity of the 1-butyl-3-methylimidazolium hexafluorophosphate is ≥99%, and the added amount of malonic acid accounts for 5wt% to 10wt% of the 1-butyl-3-methylimidazolium hexafluorophosphate.

[0018] It should be noted that by selecting high-purity [BMIM][PF6] as the base material and introducing an appropriate amount of malonic acid under well-controlled reaction conditions, carboxyl groups can be effectively introduced into the molecular structure of the ionic liquid. This modification enhances the solubility and selectivity of the ionic liquid, allowing it to exhibit higher extraction efficiency and purity in the extraction process of mannose. The entire modification process ensures the full progress of the reaction and the stability of the product through appropriate temperature control and reaction time, thereby obtaining a modified ionic liquid with excellent performance.

[0019] As a preferred technical solution for the preparation method of mannose extracted from birch, the specific steps of step 3 include:

[0020] After the extraction is completed, a microfiltration membrane or filter paper can be used for filtration. The extracted mannose extract can be filtered through a filtration device to remove impurities to ensure that the liquid entering the membrane separation device is pure.

[0021] Select suitable membrane materials according to the pore size of the membrane, install a membrane separation device to ensure that the system is leak-free, and then perform membrane separation operations to separate and recover the ionic liquid through an ultrafiltration membrane or a nanofiltration membrane; during the operation, adjust the operating pressure between 2-10 bar to ensure a stable membrane flux, and control the temperature between 25-40°C to avoid damage to the membrane material by high temperature. At the same time, adjust the feed flow rate between 0.5-2.0 L / min to ensure that the liquid passes through the membrane surface evenly, separate the ionic liquid from other components through membrane separation, and recover pure ionic liquid permeate.

[0022] As a preferred technical solution for a preparation method based on extracting mannose from birch, the membrane material includes a polyethersulfone membrane and a polyvinylidene fluoride membrane.

[0023] It should be noted that the modified [BMIM][PF6] cannot pass through the microporous structure of PES and PVDF membranes and is retained due to its larger molecular structure and high polarity, while mannose and water molecules can selectively pass through these membranes due to their smaller molecular size and different hydrophilic and hydrophobic properties.

[0024] As a preferred technical solution for the preparation method of mannose extracted from birch, the specific steps of step 4 include:

[0025] The extract is placed in a low temperature environment, the cooling temperature is controlled at 4-10°C, and the cooling time is 12-24 hours. Under low temperature conditions, the solubility of mannose decreases and gradually crystallizes. After cooling, the crystallized mannose is separated by filtration or centrifugation. This step separates mannose from the extract by physical methods, improves the purity of the extract, and prepares for the subsequent purification step;

[0026] The crystallized mannose is dissolved in water or an acetonitrile-water mixed solution as the mobile phase to prepare a solution with a concentration controlled at 10-20 mg / mL. Then, the prepared sample solution is injected into the HPLC system through an injector. The configuration of the HPLC system includes selecting an amino column or other special column suitable for carbohydrate analysis, the mobile phase is an acetonitrile-water mixed solution (70:30 v / v), the flow rate is controlled at 0.5-1.0 mL / min, the detector uses a differential refractive index detector (RID), and the column temperature is controlled at 25-30 ° C. The sample solution is separated by a chromatographic column in the HPLC system, and mannose and other impurities are eluted in sequence according to different retention times. Among them, the volume ratio of acetonitrile to water in the acetonitrile-water mixed solution is 7:3.

[0027] The present invention proposes a preparation method for extracting mannose based on birch, and by using modified 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) as a green solvent, the extraction rate and purity of mannose are significantly improved. The method has the following beneficial effects: first, by optimizing the addition amount of malonic acid and the extraction conditions, the extraction rate of mannose reaches 32.9%, which is significantly higher than the traditional method. Secondly, by using membrane separation technology and high performance liquid chromatography (HPLC) purification, the purity of mannose reaches 98.4%, ensuring the quality and application value of the product. In addition, the modified ionic liquid has good solubility and selectivity, does not need to use organic solvents, reduces environmental pollution, and conforms to the concept of green chemistry. Finally, by recycling and reusing ionic liquids, the production cost is reduced and the economic benefit is improved. Therefore, the present invention not only has the characteristics of high efficiency and environmental protection, but also has significant economic value and broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 The HPLC spectrum of the extract of Example 1 is shown in FIG. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0033] Preparation Example 1

[0034] Preparation of modified 1-butyl-3-methylimidazolium hexafluorophosphate

[0035] The preparation steps of the modified 1-butyl-3-methylimidazolium hexafluorophosphate include: using 1-butyl-3-methylimidazolium hexafluorophosphate with a purity greater than 99.9% as a base material, adding malonic acid to the 1-butyl-3-methylimidazolium hexafluorophosphate under stirring, heating the mixture to 80° C., reacting at the temperature for 3 hours, and cooling to room temperature to obtain carboxylated 1-butyl-3-methylimidazolium hexafluorophosphate. The amount of malonic acid added accounts for 5wt% of the 1-butyl-3-methylimidazolium hexafluorophosphate.

[0036] The difference between Preparation Examples 2 to 6 and Preparation 1 is that the amount of malonic acid added is different.

[0037] The amounts of malonic acid added in Preparation Examples 1 to 6 are shown in Table 1.

[0038] Table 1

[0039]

[0040] Example 1

[0041] Step 1, crushing the birch raw material into small particles, the particle size range of the particles is 0.5 mm;

[0042] Step 2, prepare a citric acid-phosphate buffer solution, adjust the pH to 4.8, and then soak the birch particles in the buffer solution for 2 hours to fully wet and soften the particles. Then, take a certain amount of birch particles, add 100 ml of buffer solution, and according to the instructions for use of the enzyme preparation, add appropriate amounts of cellulase (20 units) and hemicellulase (10 units), place the reaction system in a constant temperature oscillator, control the temperature at 50°C, the oscillation speed at 150 rpm, and the reaction time for 24 hours. During this period, samples are taken regularly (for example, once every 4 hours) to detect the concentration change of the enzymolysis product; after the reaction is completed, the enzymolysis reaction is terminated by heating to 90°C and keeping warm for 10 minutes to inactivate the enzyme, and then the enzymolysis product is filtered using filter paper or a microfiltration membrane to separate the unenzymolyzed residue, and the filtrate is collected;

[0043] Step 3, mixing the collected filtrate with the ionic liquid of Preparation Example 1, with the ratio of the collected filtrate to the ionic liquid being 1:10, and performing extraction under stirring conditions;

[0044] Step 4, after the extraction is completed, a microfiltration membrane or filter paper can be used for filtration, and the extracted mannose extract can be passed through a filtration device to remove impurities to ensure that the liquid entering the membrane separation device is pure;

[0045] Select polyethersulfone membrane material according to the pore size of the membrane, install a membrane separation device to ensure that the system is leak-free, and then perform membrane separation operation to separate and recover the ionic liquid through an ultrafiltration membrane or a nanofiltration membrane; during the operation, adjust the operating pressure to 8 bar, control the temperature to 40°C, and at the same time, adjust the feed flow rate to 2.0 L / min;

[0046] Step 5, placing the extract in a low temperature environment, controlling the cooling temperature at 4°C for 12 hours, and after the cooling is completed, separating the crystallized mannose by filtering or centrifugation to prepare for the subsequent purification step;

[0047] The crystallized mannose was dissolved in the mobile phase of an acetonitrile-water mixed solution to prepare a solution, and the concentration was controlled at 20 mg / m. Then, the prepared sample solution was injected into the HPLC system through an injector, and the flow rate was controlled at 1.0 mL / min. The detector used a differential refractive index detector, and the column temperature was controlled at 25° C. The sample solution was separated by a chromatographic column in the HPLC system; wherein the volume ratio of acetonitrile to water in the acetonitrile-water mixed solution was 7:3;

[0048] Step 6, drying the purified mannose solution to obtain solid mannose.

[0049] Example 2

[0050] Step 1, crushing the birch raw material into small particles, the particle size range of the particles is 2 mm;

[0051] Step 2, prepare a citric acid-phosphate buffer solution, adjust the pH to 4.8, and then soak the birch particles in the buffer solution for 2 hours to fully wet and soften the particles. Then, take a certain amount of birch particles, add 100 ml of buffer solution, and according to the instructions for use of the enzyme preparation, add appropriate amounts of cellulase (20 units) and hemicellulase (10 units), place the reaction system in a constant temperature oscillator, control the temperature at 50°C, the oscillation speed at 150 rpm, and the reaction time for 24 hours. During this period, samples are taken regularly (for example, once every 4 hours) to detect the concentration change of the enzymolysis product; after the reaction is completed, the enzymolysis reaction is terminated by heating to 90°C and keeping warm for 10 minutes to inactivate the enzyme, and then the enzymolysis product is filtered using filter paper or a microfiltration membrane to separate the unenzymolyzed residue, and the filtrate is collected;

[0052] Step 3, mixing the collected filtrate with the ionic liquid of Preparation Example 1, with the ratio of the collected filtrate to the ionic liquid being 1:20, and performing extraction under stirring conditions;

[0053] Step 4, after the extraction is completed, a microfiltration membrane or filter paper can be used for filtration, and the extracted mannose extract can be passed through a filtration device to remove impurities to ensure that the liquid entering the membrane separation device is pure;

[0054] Select polyethersulfone membrane material according to the pore size of the membrane, install a membrane separation device to ensure that the system is leak-free, and then perform membrane separation operation to separate and recover the ionic liquid through an ultrafiltration membrane or a nanofiltration membrane; during the operation, adjust the operating pressure to 10 bar and control the temperature to 25°C, and at the same time, adjust the feed flow rate to 2.0 L / min;

[0055] Step 5, placing the extract in a low temperature environment, controlling the cooling temperature at 4°C for 24 hours, and after the cooling is completed, separating the crystallized mannose by filtration or centrifugation to prepare for the subsequent purification step;

[0056] The crystallized mannose was dissolved in the mobile phase of an acetonitrile-water mixed solution to prepare a solution, and the concentration was controlled at 10 mg / m. Then, the prepared sample solution was injected into the HPLC system through an injector, and the flow rate was controlled at 0.5 mL / min. The detector used a differential refractive index detector, and the column temperature was controlled at 30° C. The sample solution was separated by a chromatographic column in the HPLC system; wherein the volume ratio of acetonitrile to water in the acetonitrile-water mixed solution was 7:3;

[0057] Step 6, drying the purified mannose solution to obtain solid mannose.

[0058] Example 3

[0059] Step 1, crushing the birch raw material into small particles, the particle size range of the particles is 1 mm;

[0060] Step 2, prepare a citric acid-phosphate buffer solution, adjust the pH to 4.8, and then soak the birch particles in the buffer solution for 2 hours to fully wet and soften the particles. Then, take a certain amount of birch particles, add 100 ml of buffer solution, and according to the instructions for use of the enzyme preparation, add appropriate amounts of cellulase (20 units) and hemicellulase (10 units), place the reaction system in a constant temperature oscillator, control the temperature at 50°C, the oscillation speed at 150 rpm, and the reaction time for 24 hours. During this period, samples are taken regularly (for example, once every 4 hours) to detect the concentration change of the enzymolysis product; after the reaction is completed, the enzymolysis reaction is terminated by heating to 90°C and keeping warm for 10 minutes to inactivate the enzyme, and then the enzymolysis product is filtered using filter paper or a microfiltration membrane to separate the unenzymolyzed residue, and the filtrate is collected;

[0061] Step 3, mixing the collected liquid with the ionic liquid of Preparation Example 1, wherein the ratio of the collected liquid to the ionic liquid is 1:15 (w / v), and performing extraction under stirring;

[0062] Step 4, after the extraction is completed, a microfiltration membrane or filter paper can be used for filtration, and the extracted mannose extract can be passed through a filtration device to remove impurities to ensure that the liquid entering the membrane separation device is pure;

[0063] Select polyethersulfone membrane material according to the pore size of the membrane, install a membrane separation device to ensure that the system is leak-free, and then perform membrane separation operation to separate and recover the ionic liquid through an ultrafiltration membrane or a nanofiltration membrane; during the operation, adjust the operating pressure to between 2 bar and control the temperature to 35°C, and at the same time, adjust the feed flow rate to between 1 L / min;

[0064] Step 5, placing the extract in a low temperature environment, controlling the cooling temperature at 10° C. for 18 hours, and after the cooling is completed, separating the crystallized mannose by filtration or centrifugation to prepare for the subsequent purification step;

[0065] The crystallized mannose was dissolved in the mobile phase of an acetonitrile-water mixed solution to prepare a solution, and the concentration was controlled at 15 mg / m. Then, the prepared sample solution was injected into the HPLC system through an injector, and the flow rate was controlled at 0.5 mL / min. The detector used a differential refractive index detector, and the column temperature was controlled at 30° C. The sample solution was separated by a chromatographic column in the HPLC system; wherein the volume ratio of acetonitrile to water in the acetonitrile-water mixed solution was 7:3;

[0066] Step 6, drying the purified mannose solution to obtain solid mannose.

[0067] Example 4

[0068] Step 1, crushing the birch raw material into small particles, the particle size range of the particles is 2 mm;

[0069] Step 2, prepare a citric acid-phosphate buffer solution, adjust the pH to 4.8, and then soak the birch particles in the buffer solution for 2 hours to fully wet and soften the particles. Then, take a certain amount of birch particles, add 100 ml of buffer solution, and according to the instructions for use of the enzyme preparation, add appropriate amounts of cellulase (20 units) and hemicellulase (10 units), place the reaction system in a constant temperature oscillator, control the temperature at 50°C, the oscillation speed at 150 rpm, and the reaction time for 24 hours. During this period, samples are taken regularly (for example, once every 4 hours) to detect the concentration change of the enzymolysis product; after the reaction is completed, the enzymolysis reaction is terminated by heating to 90°C and keeping warm for 10 minutes to inactivate the enzyme, and then the enzymolysis product is filtered using filter paper or a microfiltration membrane to separate the unenzymolyzed residue, and the filtrate is collected;

[0070] Step 3, mixing the collected filtrate with the ionic liquid of Preparation Example 1, with the ratio of the collected filtrate to the ionic liquid being 1:14, and performing extraction under stirring;

[0071] Step 4, after the extraction is completed, a microfiltration membrane or filter paper can be used for filtration, and the extracted mannose extract can be passed through a filtration device to remove impurities to ensure that the liquid entering the membrane separation device is pure;

[0072] Select polyethersulfone membrane material according to the pore size of the membrane, install a membrane separation device to ensure that the system is leak-free, and then perform membrane separation operation to separate and recover the ionic liquid through an ultrafiltration membrane or a nanofiltration membrane; during the operation, adjust the operating pressure to between 2 bar and control the temperature to 30°C, and at the same time, adjust the feed flow rate to between 1.0 L / min;

[0073] Step 5, placing the extract in a low temperature environment, controlling the cooling temperature at 8° C. for 18 hours, and after the cooling is completed, separating the crystallized mannose by filtration or centrifugation to prepare for the subsequent purification step;

[0074] The crystallized mannose was dissolved in the mobile phase of an acetonitrile-water mixed solution to prepare a solution, and the concentration was controlled at 15 mg / m. Then, the prepared sample solution was injected into the HPLC system through an injector, and the flow rate was controlled at 0.7 mL / min. The detector used a differential refractive index detector, and the column temperature was controlled at 35° C. The sample solution was separated by a chromatographic column in the HPLC system; wherein the volume ratio of acetonitrile to water in the acetonitrile-water mixed solution was 7:3;

[0075] Step 6, drying the purified mannose solution to obtain solid mannose.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that unmodified 1-butyl-3-methylimidazolium hexafluorophosphate is used as the ionic liquid.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that the ionic liquid of Preparation Example 2 is used.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 1 is that the ionic liquid of Preparation Example 3 is used.

[0082] Comparative Example 4

[0083] The difference between this comparative example and Example 1 is that the ionic liquid of Preparation Example 4 is used.

[0084] Comparative Example 5

[0085] The difference between this comparative example and Example 1 is that the ionic liquid of Preparation Example 5 is used.

[0086] Comparative Example 6

[0087] The difference between this comparative example and Example 1 is that the ionic liquid of Preparation Example 6 is used.

[0088] Performance Testing

[0089] Extraction rate = (extract weight / birch raw material weight) x 100%.

[0090] Purity test method:

[0091] The purity of mannose can be read directly in step 4.

[0092] Table 1

[0093]

[0094]

[0095] From Examples 1 to 4 and Table 4, it can be seen that the extraction rate of mannose extracted by the method of the present application is between 27.9% and 32.9%, and the purity is between 92.6% and 98.4%, indicating that by optimizing the extraction conditions, the extraction rate and purity of mannose can be significantly improved, and by reasonably controlling the addition amount of ionic liquid and the extraction parameters, the product purity can be improved while ensuring efficient extraction, and the cost and environmental burden can be reduced, which has important practical application value.

[0096] Combining Example 1, Comparative Example 1 and Table 4, it can be seen that the extraction rate and the purity of the obtained product in Example 1 are higher than those in Comparative Example 1. Using modified 1-butyl-3-methylimidazolium hexafluorophosphate as an extractant can significantly improve the extraction rate and purity of mannose.

[0097] From Example 1, Comparative Examples 2 to 6 and Table 4, it can be seen that as the amount of malonic acid increases, the extraction rate and purity increase. The appropriate addition of malonic acid improves the extraction rate and purity of mannose by improving the solubility of the ionic liquid. When the amount of malonic acid exceeds a certain value, the extraction rate and purity decrease. Excessive malonic acid may cause the solubility of the target substance (mannose) and non-target substances (impurities) in the extract to increase significantly, resulting in an increase in the impurity content in the extract, reducing the selectivity of the extraction and the purity of the extract.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method based on extracting mannose from birch, It is characterized in that The technical steps include: Step 1, crushing the birch raw material into small particles, the particle size of the particles ranges from 0.5 to 2 mm; Step 2, preparing a citric acid-phosphate buffer solution, adjusting the pH to 4.8, and then soaking the birch particles in the buffer solution for 2 hours, then adding the birch particles to the buffer solution, and adding appropriate amounts of cellulase and hemicellulase; after the reaction is completed, heating to 90° C. for 10 minutes to terminate the enzymatic hydrolysis reaction, and then filtering the enzymatic hydrolysis product to separate the unenzymatic residue, and collecting the filtrate; Step 3, mixing the filtrate with an ionic liquid and extracting under stirring conditions; wherein the ionic liquid is modified 1-butyl-3-methylimidazolium hexafluorophosphate; Step 4, after the extraction is completed, recovering the ionic liquid by membrane separation technology; Step 5, cooling the separated extract to allow mannose to crystallize, and then separating and purifying the crystallized mannose using high performance liquid chromatography; Step 6, drying the purified mannose solution to obtain solid mannose.

2. The method for preparing mannose extracted from birch according to claim 1, It is characterized in that The mass ratio of the filtrate to the ionic liquid is 1:10 to 1:

20.

3. The method for preparing mannose extracted from birch according to claim 1, It is characterized in that The preparation steps of the modified 1-butyl-3-methylimidazolium hexafluorophosphate include: taking 1-butyl-3-methylimidazolium hexafluorophosphate as a base material, adding malonic acid to the 1-butyl-3-methylimidazolium hexafluorophosphate under stirring, heating the mixture to 80° C., reacting at the temperature for 3 hours, and cooling to room temperature to obtain carboxylated 1-butyl-3-methylimidazolium hexafluorophosphate.

4. The method for preparing mannose extracted from birch according to claim 3, It is characterized in that The purity of the 1-butyl-3-methylimidazolium hexafluorophosphate is ≥99%, and the added amount of the malonic acid accounts for 5wt% to 10wt% of the 1-butyl-3-methylimidazolium hexafluorophosphate.

5. The method for preparing mannose extracted from birch according to claim 1, It is characterized in that The specific steps of step 3 include: After the extraction is completed, a microfiltration membrane or filter paper can be used for filtration. The extracted mannose extract can be filtered through a filtration device to remove impurities to ensure that the liquid entering the membrane separation device is pure. Select suitable membrane materials according to the pore size of the membrane, install a membrane separation device, ensure that the system is leak-free, and then perform membrane separation operations to separate and recover ionic liquids through ultrafiltration membranes or nanofiltration membranes; during the operation, adjust the operating pressure between 2-10 bar, and control the temperature between 25-40°C. At the same time, adjust the feed flow rate between 0.5-2.0 L / min.

6. The method for preparing mannose extracted from birch according to claim 5, It is characterized in that The membrane materials include polyethersulfone membrane and polyvinylidene fluoride membrane.

7. The method for preparing mannose extracted from birch according to claim 5, It is characterized in that The specific steps of step 4 include: The extract is placed in a low temperature environment, the cooling temperature is controlled at 4-10°C, and the cooling time is 12-24 hours. After the cooling is completed, the crystallized mannose is separated by filtration or centrifugation to prepare for the subsequent purification step; The crystallized mannose is dissolved in a mobile phase of an acetonitrile-water mixed solution to prepare a solution, and the concentration is controlled at 10-20 mg / m. Then, the prepared sample solution is injected into an HPLC system through an injector, and the flow rate is controlled at 0.5-1.0 mL / min. A differential refractometer is used as a detector, and the column temperature is controlled at 25-30° C. The sample solution is separated by a chromatographic column in the HPLC system; wherein the volume ratio of acetonitrile to water in the acetonitrile-water mixed solution is 7:3.

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