A method for stepwise extraction of single components from high-purity insoluble dietary fiber
By using eutectic solvents and treatment with ethanol, acetone, and alkaline solutions, the problems of complex extraction steps and low purity of insoluble dietary fiber from soybean residue have been solved, achieving safe and environmentally friendly extraction of high-purity single components and broadening its application in the food, cosmetics, and biopharmaceutical fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JILIN AGRICULTURAL UNIV
- Filing Date
- 2023-11-08
- Publication Date
- 2026-05-26
Smart Images
Figure CN117510890B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical separation technology, and more specifically to a method for the stepwise extraction of single components from high-purity insoluble dietary fiber. Background Technology
[0002] Soybean residue is a general term for the byproducts of traditional soy product and soy protein isolate processing. Soybean residue contains over 60% dietary fiber, with insoluble dietary fiber accounting for over 90% of the total dietary fiber content, making it an ideal source of insoluble dietary fiber. Lignin, hemicellulose, and cellulose are important components of the insoluble dietary fiber in soybean residue, and because they can alter the activity of intestinal microorganisms and lower blood cholesterol and blood sugar levels, they are used to prevent cardiovascular disease. However, the insoluble dietary fiber in soybean residue is currently not fully utilized.
[0003] While existing technologies offer methods for the stepwise extraction of lignin, hemicellulose, and cellulose, these methods suffer from drawbacks such as complex steps, low production efficiency, and low purity of individual components. Furthermore, the solvents used in these extraction processes are not suitable for green production, further limiting the application of lignin, hemicellulose, and cellulose in food, cosmetics, and biomedicine.
[0004] Therefore, providing a safe and efficient method for extracting high-purity lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, the present invention provides a method for the stepwise extraction of lignin, cellulose and hemicellulose from high-purity insoluble dietary fiber. This method can achieve the stepwise extraction of single components from insoluble dietary fiber with high purity of each component. In addition, the raw materials used are inexpensive and can also realize the high-value utilization of waste and reduce resource waste.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A method for stepwise extraction of lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber, specifically including the following steps:
[0008] (1) Extraction of lignin: The eutectic solvent and high-purity insoluble dietary fiber were mixed and stirred at 80℃ for 2-3 hours at a ratio of 4:1 (mL / g). After the reaction was completed and cooled, the reaction product was obtained. Ethanol was added to the reaction product and stirred, washed and filtered to obtain filtrate and precipitate 1. The filtrate was then concentrated and water was added to the concentrate and allowed to stand to obtain a precipitate containing lignin. The precipitate was then washed and dried to obtain lignin.
[0009] The eutectic solvent includes choline chloride and glycerol, with a molar mass ratio of choline chloride:glycerol = 1:(3-5).
[0010] (2) Extraction of hemicellulose: Add acetone to the first precipitate and stir magnetically, then centrifuge, repeat three times to obtain the second precipitate; then add ethanol to the second precipitate to remove acetone, then add 15 mL of alkaline solution, stir for 30-45 min, let stand to obtain the third precipitate and supernatant; then adjust the pH of the supernatant to neutral, add three times the volume of ethanol to the supernatant for alcohol precipitation, and then freeze dry to obtain hemicellulose;
[0011] (3) Extraction of cellulose: The precipitate was repeatedly washed with ethanol and then freeze-dried to obtain cellulose.
[0012] The beneficial effects achieved by the above technical solution are as follows: This invention utilizes the fusion of glycerol and choline chloride to form a eutectic solvent (DES solvent), which can gradually separate and extract single components from high-purity insoluble dietary fiber. On the one hand, the eutectic solvent extraction method can obtain high-purity single components; on the other hand, this method is green, environmentally friendly, and highly safe, with good application effects and development prospects. Specifically, the principle involved in step (1) is to break the covalent bonds between hemicellulose and cellulose and lignin in high-purity insoluble dietary fiber through DES solvent, causing the hydroxycinnamic acid of a large number of acetyl units in lignin to form ester bonds and simultaneously remove lignin, thus facilitating the extraction of lignin.
[0013] Preferably, the glycerol is food-grade glycerol.
[0014] Preferably, the preparation steps of the eutectic solvent are as follows:
[0015] Choline chloride and glycerol were placed in a DF-101S thermal collector magnetic stirrer at the above molar mass ratio and stirred at a constant temperature for 2-3 hours, and then kept at 80°C for 1-2 hours to prepare a eutectic solvent.
[0016] The beneficial effects achieved by the above technical solution are as follows: Glycerin is an inexpensive starting material. The present invention uses food-grade glycerin as the hydrogen donor (HBD) component for the synthesis of glycerol-based DES, which can improve its safety and acceptability in the food field, and also has the characteristics of good fluidity and high thermal stability. In addition, the above DES solvent preparation method has the advantages of simple operation, high efficiency, good repeatability, low cost and green environmental protection.
[0017] Furthermore, in the eutectic solvent, the molar mass ratio of choline chloride to glycerol is choline chloride:glycerol = 1:3 or 1:5.
[0018] Preferably, the constant temperature heating temperature is 80-95℃.
[0019] Preferably, the preparation steps of the high-purity insoluble dietary fiber are as follows:
[0020] The soybean residue powder was enzymatically hydrolyzed by adding peak amylase and neutral protease, respectively. Then, acetic acid solution was added to adjust the pH of the mixture to 4.5±0.02, followed by the addition of amyloglucosidase for further enzymatic hydrolysis. Distilled water was then added to the hydrolysate, followed by static clarification, centrifugation and alcohol precipitation, filtration, and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0021] The beneficial effects achieved by the above technical solution are as follows: This invention uses soybean residue, the main by-product of traditional soybean product and soybean protein isolate processing, as raw material, which can realize the high-value utilization of waste, reduce resource waste, extend the industrial chain, and lay the foundation for expanding the application of soybean residue in food, cosmetics, additives, nanomaterials and other fields.
[0022] Preferably, the ratio of soybean residue powder, peak amylase, neutral protease and amyloglucosidase is 5g:0.5mL:1.5mL:2mL.
[0023] Furthermore, the concentration ratio of the peak amylase, neutral protease, and amylase in the solution is: peak amylase : neutral protease : amylase = 0.25 g / mL : 0.005 g / mL : 0.02 g / mL.
[0024] Furthermore, the enzyme activities of the peak amylase, neutral protease, and amylase are 40,000 U / g, 500,000 U / g, and 100,000 U / g, respectively.
[0025] Preferably, the magnetic stirring time in step (2) is 2-2.5 hours and the magnetic stirring speed is 8000-8500 rpm.
[0026] Preferably, the centrifugation time in step (2) is 10 min.
[0027] Preferably, the concentration of the alkali solution in step (2) is 1-2.2 mol / L.
[0028] Furthermore, the alkaline solution is sodium hydroxide.
[0029] The beneficial effects achieved by the above technical solution are as follows: In the process of extracting hemicellulose, the addition of a certain amount of alkali solution can roughen the fiber surface and expose the pores. The penetration of alkali solution will cause the fiber to swell, and the hemicellulose will be effectively extracted.
[0030] The lignin extracted by the above method has a purity of ≥94%, hemicellulose has a purity of ≥90%, and cellulose has a purity of ≥74%.
[0031] The cellulose, hemicellulose, and lignin extracted by the above methods have applications in the food, industrial, cosmetic, and biomedical fields.
[0032] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:
[0033] (1) This invention makes an innovative change to the traditional extraction method. It replaces it with the inexpensive, green and pollution-free DES method; the glycerol used in the solvent is food-grade glycerol, which to some extent solves the precedent that food-grade reagents cannot be used as extraction solvents.
[0034] (2) Compared with other methods, the method mentioned in this invention can quickly extract lignin, hemicellulose and cellulose from insoluble dietary fiber; and the purity of the extracted single components is high, specifically, the purity of lignin obtained by the method of this invention is ≥94%, the purity of hemicellulose is ≥90%, and the purity of cellulose is ≥74%.
[0035] (3) This invention uses soybean residue as a widely available and inexpensive raw material. The extracted natural single components can be converted into renewable energy, truly realizing the high-value utilization of waste. It also provides theoretical reference value and new ideas for expanding the application of soybean residue in the food industry and other future industries, as well as for other raw materials. Attached Figure Description
[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0037] Figure 1 The diagram shows DES solvents with choline chloride and glycerol in molar ratios of 1:3 and 1:5.
[0038] Figure 2 Images of cellulose, hemicellulose, and lignin samples prepared in Examples 1 and 3;
[0039] in, Figure 2 -a is a cellulose sample image. Figure 2 -b is a sample image of hemicellulose. Figure 2 -c is a lignin sample image.
[0040] Figure 3 The scanning electron microscope image of the single component prepared in Example 2 is shown below.
[0041] in, Figure 3 -a is a scanning electron microscope image of cellulose. Figure 3 -b is a scanning electron microscope image of hemicellulose. Figure 3 -c is a scanning electron microscope image of lignin.
[0042] Figure 4 XRD patterns of single components were prepared for Example 4. Detailed Implementation
[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0044] This invention discloses a method for the stepwise extraction of lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber, specifically including the following steps:
[0045] (1) Extraction of lignin: The eutectic solvent and high-purity insoluble dietary fiber were mixed and stirred at 80℃ for 2-3 hours at a ratio of 4:1 (mL / g). After the reaction was completed and cooled, the reaction product was obtained. Ethanol was added to the reaction product and stirred, washed and filtered to obtain filtrate and precipitate 1. The filtrate was then concentrated and water was added to the concentrate and allowed to stand to obtain a precipitate containing lignin. The precipitate was then washed and dried to obtain lignin.
[0046] The eutectic solvent is composed of choline chloride and food-grade glycerol in a mass ratio of choline chloride to food-grade glycerol of 1:(3-5).
[0047] (2) Extraction of hemicellulose: Add acetone to the first precipitate and stir magnetically for 2-2.5 h at a stirring speed of 8000-8500 rpm and centrifuge for 10 min. Repeat this process three times to obtain the second precipitate. Then add ethanol to the second precipitate to remove the acetone, and then add 1-2.2 mol / L alkaline solution. Stir for 30-45 min and let stand to obtain the third precipitate and the supernatant. Then adjust the pH of the supernatant to neutral, add three times the volume of ethanol to the supernatant for alcohol precipitation, and then freeze dry to obtain hemicellulose.
[0048] (3) Extraction of cellulose: The precipitate was repeatedly washed with ethanol and then freeze-dried to obtain cellulose.
[0049] The preparation steps of the aforementioned eutectic solvent are as follows:
[0050] Choline chloride and food-grade glycerol were placed in a DF-101S thermal collector magnetic stirrer at the above molar ratio and stirred at 80-95℃ for 2-3 hours, followed by holding at that temperature for 1-2 hours to prepare a eutectic solvent.
[0051] The preparation steps for high-purity insoluble dietary fiber are as follows:
[0052] Soybean residue powder was enzymatically hydrolyzed by adding peak amylase and neutral protease. The pH of the mixture was then adjusted to 4.5 ± 0.02 with acetic acid solution, followed by further enzymatic hydrolysis with amyloglucosidase. Distilled water was added to the hydrolysate, and the mixture was then subjected to a series of steps: static clarification, centrifugation with alcohol precipitation, filtration, and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%. The ratio of soybean residue powder, peak amylase, neutral protease, and amyloglucosidase was 5g:0.5mL:1.5mL:2mL.
[0053] Furthermore, the concentration ratio of the peak amylase, neutral protease and amylase solution is as follows: peak amylase : neutral protease : amylase = 1.25g / 5mL : 0.125g / 25mL : 0.25g / 12.5mL.
[0054] Furthermore, the enzyme activities of the peak amylase, neutral protease, and amylase are 40,000 U / g, 500,000 U / g, and 100,000 U / g, respectively.
[0055] The lignin extracted using the above method has a purity of ≥94%, hemicellulose a purity of ≥90%, and cellulose a purity of ≥74%.
[0056] The enzyme activities of peak amylase, neutral protease, and amylase used in the following examples and comparative examples were 40,000 U / g, 500,000 U / g, and 100,000 U / g, respectively; and their solution concentrations were 0.25 g / mL, 0.005 g / mL, and 0.02 g / mL, respectively.
[0057] Example 1
[0058] First, 5g of soybean residue powder was added to 250mL of distilled water and transferred to a 1000mL Erlenmeyer flask for enzymatic hydrolysis. 0.5mL of peak amylase and 1.5mL of neutral protease were added for enzymatic hydrolysis. Then, acetic acid solution was added to adjust the pH of the mixture to 4.5±0.02. Next, 2mL of amylase was added for enzymatic hydrolysis. Then, distilled water was added to the hydrolysate, and the mixture was allowed to stand for clarification, centrifuged for alcohol precipitation, filtered, and freeze-dried to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0059] Secondly, DES solvent was prepared using a laboratory DF-101S thermostatic magnetic stirrer. The mixture was stirred at 80℃ for 2 hours and then kept at that temperature for another 2 hours. The prepared DES solvent, with a choline chloride:glycerol molar ratio of 1:3, was named DES:1:3. DES was mixed with high-purity insoluble dietary fiber at a ratio of 4:1 (mL / g) at 80℃ and stirred for 2 hours. After the reaction was complete, the mixture was cooled to obtain the reaction product. Ethanol was added to the reaction product and stirred. The mixture was washed with ethanol, filtered, and the precipitate was retained. The filtrate was concentrated to obtain a concentrated solution, which was then added to water and allowed to stand to obtain a precipitate containing lignin. This precipitate was washed and dried to obtain lignin. The solid precipitate retained after lignin extraction was added to acetone and magnetically stirred for 2 hours. The mixture was centrifuged at 8000 rpm for 10 minutes, repeated three times. Ethanol was then added to remove the acetone. 15 mL of 1 mol / L NaOH was added to the precipitate and stirred for 30 minutes. After standing, the precipitate was retained, and the supernatant was extracted. The pH was adjusted to neutral, and three times the volume of ethanol was added for alcohol precipitation. The precipitate was then lyophilized to obtain hemicellulose. The retained precipitate was repeatedly washed with ethanol and then freeze-dried to obtain cellulose.
[0060] Conclusion: Figure 1 As shown, DES solvent with a molar mass ratio of 1:3 is a transparent liquid with good flowability. Figure 2 As shown in -c, the extracted lignin is a grayish-white powder. For example... Figure 2 -b shows that the freeze-dried hemicellulose is a yellow powder. For example... Figure 2 As shown in -a, cellulose is pure white.
[0061] The contents of lignin, cellulose, and hemicellulose were calculated using Van Soest's washing fiber analysis method (the same analytical method was used in the following examples). The calculated purity of lignin extracted by DES was 95.8%, the purity of hemicellulose was 92%, and the purity of cellulose was 76%.
[0062] like Figure 4 As shown, single-component XRD Figure 2 θ corresponds to its crystal plane, proving that stepwise extraction can achieve the extraction and separation of single components.
[0063] Example 2
[0064] Take 5g of soybean residue powder, add 250mL of distilled water, transfer to a 1000mL Erlenmeyer flask for enzymatic hydrolysis, add 0.5mL of peak amylase and 1.5mL of neutral protease for enzymatic hydrolysis, then add acetic acid solution to adjust the pH of the mixture to 4.5±0.02, then add 2mL of amylase for enzymatic hydrolysis, then add distilled water to the enzymatic hydrolysate, and then perform static clarification, centrifugation and alcohol precipitation, filtration and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0065] DES solvent was prepared using a laboratory DF-101S thermostatically heated magnetic stirrer. The mixture was stirred at 90℃ for 3 hours and kept at that temperature for 2 hours. The prepared DES solvent, with a choline chloride:glycerol molar ratio of 1:3, was named DES-1:3. DES was mixed with high-purity insoluble dietary fiber at a ratio of 4:1 (mL / g) at 80℃ and stirred for 3 hours. After the reaction was complete, the mixture was cooled to obtain the reaction product. Ethanol was added to the reaction product and stirred. The mixture was washed with ethanol, filtered, and the precipitate was retained. The filtrate was concentrated to obtain a concentrated solution, which was then added to water and allowed to stand, yielding a precipitate containing lignin. This precipitate was washed and dried to obtain lignin. The solid precipitate retained after lignin extraction was added to acetone and magnetically stirred for 2.5 hours. The mixture was centrifuged at 8500 rpm for 10 minutes, repeated three times. Ethanol was then added to remove the acetone. 15 mL of 2 mol / L NaOH was added to the precipitate and stirred for 40 minutes. After standing, the precipitate was retained, and the supernatant was extracted. The pH was adjusted to neutral, and three times the volume of ethanol was added for alcohol precipitation. The precipitate was then lyophilized to obtain hemicellulose. The retained precipitate was repeatedly washed with ethanol and then freeze-dried to obtain cellulose.
[0066] like Figure 1 As shown, the DES solvent with a molar mass ratio of 1:3 is a free-flowing, transparent liquid. Calculations show that the purity of lignin extracted by DES is 95%, the purity of hemicellulose is 90%, and the purity of cellulose is 75%. This can be seen from single-component scanning electron microscopy. Figure 3 -a shows cellulose with irregular protrusions in the middle and natural folds around the edges; such as Figure 3 As shown in -c, lignin, which has a similar surface morphology, appears as smoother flakes; such as Figure 3 As shown in -b, hemicellulose has pores of varying sizes on its surface after DES treatment.
[0067] Example 3
[0068] Take 5g of soybean residue powder, add 250mL of distilled water, transfer to a 1000mL Erlenmeyer flask for enzymatic hydrolysis, add 0.5mL of peak amylase and 1.5mL of neutral protease for enzymatic hydrolysis, then add acetic acid solution to adjust the pH of the mixture to 4.5±0.02, then add 2mL of amylase for enzymatic hydrolysis, then add distilled water to the enzymatic hydrolysate, and then perform static clarification, centrifugation and alcohol precipitation, filtration and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0069] DES solvent was prepared using a laboratory DF-101S thermostatically heated magnetic stirrer. Stirring was performed at 90℃ for 2 hours, followed by holding at that temperature for 3 hours. The prepared DES solvent, with a choline chloride:glycerol molar ratio of 1:5, was named DES-1:5. Figure 1As shown. DES and high-purity insoluble dietary fiber were mixed and stirred at 80℃ for 2-3 hours at a ratio of 4:1 (mL / g). After the reaction was complete, the mixture was cooled to obtain the reaction product. Ethanol was added to the reaction product and stirred. The mixture was washed with ethanol, filtered, and the precipitate was retained. The filtrate was concentrated to obtain a concentrated solution, which was then added to water and allowed to stand, yielding a precipitate containing lignin. This precipitate was washed and dried to obtain lignin. The solid precipitate retained after lignin extraction was added to acetone and magnetically stirred for 2 hours. It was then centrifuged at 8000 rpm for 10 minutes, repeated three times. Ethanol was then added to remove the acetone. 15 mL of 1 mol / L NaOH was added to the precipitate and stirred for 30 minutes. After standing, the precipitate was retained, and the supernatant was extracted. The pH was adjusted to neutral, and three times the volume of ethanol was added for alcohol precipitation. The precipitate was lyophilized to obtain hemicellulose. The retained precipitate was repeatedly washed with ethanol and lyophilized to obtain cellulose.
[0070] like Figure 1 As shown, the DES solvent at a molar mass ratio of 1:5 is a slightly viscous, transparent liquid with poor flowability. Calculations showed that the purity of lignin extracted by DES was 94%, hemicellulose was 89%, and cellulose was 74%. Comparing these results, the increased proportion of glycerol resulted in a more compact internal structure, thus slightly reducing the purity of each component.
[0071] Example 4
[0072] Take 5g of soybean residue powder, add 250mL of distilled water, transfer to a 1000mL Erlenmeyer flask for enzymatic hydrolysis, add 0.5mL of peak amylase and 1.5mL of neutral protease for enzymatic hydrolysis, then add acetic acid solution to adjust the pH of the mixture to 4.5±0.02, then add 2mL of amylase for enzymatic hydrolysis, then add distilled water to the enzymatic hydrolysate, and then perform static clarification, centrifugation and alcohol precipitation, filtration and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0073] DES solvent was prepared using a laboratory DF-101S thermostatically heated magnetic stirrer. Stirring was performed at 95℃ for 2 hours, followed by holding at that temperature for another 2 hours. The prepared DES solvent, with a choline chloride:glycerol molar ratio of 1:5, was named DES-1:5. Figure 1As shown. DES and high-purity insoluble dietary fiber were mixed and stirred at 80℃ for 2 hours at a ratio of 4:1 (mL / g). After the reaction was complete, the mixture was cooled to obtain the reaction product. Ethanol was added to the reaction product and stirred. The mixture was washed with ethanol, filtered, and the precipitate was retained. The filtrate was concentrated to obtain a concentrated solution, which was then added to water and allowed to stand, yielding a precipitate containing lignin. This precipitate was washed and dried to obtain lignin. The solid precipitate retained after lignin extraction was added to acetone, magnetically stirred for 2 hours, and centrifuged at 8500 rpm for 10 minutes, repeated three times. Ethanol was then added to remove the acetone. 15 mL of 1.5 mol / L NaOH was added to the precipitate and stirred for 30 minutes. After standing, the precipitate was retained, and the supernatant was extracted. The pH was adjusted to neutral, and three times the volume of ethanol was added for alcohol precipitation. Hemicellulose was obtained by lyophilization. The retained precipitate was repeatedly washed with ethanol and lyophilized to obtain cellulose. Figure 2 As shown in a.
[0074] like Figure 1 As shown, a DES solvent with a molar mass ratio of 1:5 is a slightly viscous, transparent liquid with poor flowability. Figure 2 As shown in -c, lignin production is high, and it is a grayish-white powder. For example... Figure 2 -b shows a slightly darker brownish-yellow powder obtained from freeze-drying. For example... Figure 2 As shown in -a, cellulose is pure white. Calculations showed that the purity of lignin extracted by DES was 95%, the purity of hemicellulose was 91%, and the purity of cellulose was 76%. Comparing the above results, the increased proportion of glycerol resulted in a more compact internal structure, thus slightly reducing the purity of each component.
[0075] Comparative Example 1
[0076] Take 5g of soybean residue powder, add 250mL of distilled water, transfer to a 1000mL Erlenmeyer flask for enzymatic hydrolysis, add 0.5mL of peak amylase and 1.5mL of neutral protease for enzymatic hydrolysis, then add acetic acid solution to adjust the pH of the mixture to 4.5±0.02, then add 2mL of amylase for enzymatic hydrolysis, then add distilled water to the enzymatic hydrolysate, and then perform static clarification, centrifugation and alcohol precipitation, filtration and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0077] DES solvent was prepared using a laboratory DF-101S thermostatically heated magnetic stirrer, and stirred at room temperature for 2 hours. The prepared DES solvent, with a choline chloride:glycerol molar ratio of 1:3, was named DES-1:3. DES was mixed with high-purity insoluble dietary fiber at a ratio of 4:1 (mL / g) at 80℃ and stirred for 2 hours. After the reaction was complete, the mixture was cooled to obtain the reaction product. Ethanol was added to the reaction product and stirred. The mixture was washed with ethanol, filtered, and the precipitate was retained. The filtrate was concentrated to obtain a concentrate, which was then added to water and allowed to stand to obtain a precipitate containing lignin. After washing and drying, lignin was obtained. The solid precipitate retained after lignin extraction was added to acetone and magnetically stirred for 2 hours. The mixture was centrifuged at 6500 rpm for 5 minutes, repeated three times. Ethanol was then added to remove the acetone. 15 mL of 1 mol / L NaOH was added to the precipitate and stirred for 10 minutes. After standing, the precipitate was retained, and the supernatant was extracted. The pH was adjusted to neutral, and three times the volume of ethanol was added for alcohol precipitation. After lyophilization, hemicellulose was obtained. The retained precipitate was repeatedly washed with ethanol and then freeze-dried to obtain cellulose.
[0078] Calculations show that the purity of lignin extracted by DES is 65%, the purity of hemicellulose is 71%, and the purity of cellulose is 61%.
[0079] Comparative Example 2
[0080] Take 5g of soybean residue powder, add 250mL of distilled water, transfer to a 1000mL Erlenmeyer flask for enzymatic hydrolysis, add 0.5mL of peak amylase and 1.5mL of neutral protease for enzymatic hydrolysis, then add acetic acid solution to adjust the pH of the mixture to 4.5±0.02, then add 2mL of amylase for enzymatic hydrolysis, then add distilled water to the enzymatic hydrolysate, and then perform static clarification, centrifugation and alcohol precipitation, filtration and freeze-drying to obtain high-purity insoluble dietary fiber with a purity of 90.2%.
[0081] DES solvent was prepared using a laboratory DF-101S thermostatically heated magnetic stirrer, and stirred at room temperature for 2 hours. The prepared DES solvent, with a choline chloride:glycerol molar ratio of 1:5, was named DES-1:5. DES was mixed with high-purity insoluble dietary fiber at a ratio of 4:1 (mL / g) at 80℃ and stirred for 2 hours. After the reaction was complete, the mixture was cooled to obtain the reaction product. Ethanol was added to the reaction product and stirred. The mixture was washed with ethanol, filtered, and the precipitate was retained. The filtrate was concentrated to obtain a concentrated solution, which was then added to water and allowed to stand to obtain a precipitate containing lignin. After washing and drying, lignin was obtained. The solid precipitate retained after lignin extraction was added to acetone and magnetically stirred for 2 hours. The mixture was centrifuged at 8000 rpm for 5 minutes, and this process was repeated three times. Ethanol was then added to remove the acetone. 15 mL of 1.5 mol / L NaOH was added to the precipitate and stirred for 10 minutes. After standing, the precipitate was retained, and the supernatant was extracted. The pH was adjusted to neutral, and three times the volume of ethanol was added for alcohol precipitation. After lyophilization, hemicellulose was obtained. The retained precipitate was repeatedly washed with ethanol and then freeze-dried to obtain cellulose.
[0082] Calculations show that the purity of lignin extracted by DES is 77%, the purity of hemicellulose is 74.6%, and the purity of cellulose is 52.9%.
[0083] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for stepwise extraction of lignin, cellulose, hemicellulose from high purity insoluble dietary fiber, characterized by, include: (1) Extraction of lignin: High-purity insoluble dietary fiber and eutectic solvent were stirred at 80℃ for 2-3 hours at a ratio of 1:4 g / mL. After cooling, ethanol was added to the reaction product for washing and filtration to obtain filtrate and precipitate 1. The filtrate was then concentrated, allowed to stand, washed and dried to obtain lignin. The eutectic solvent includes choline chloride and glycerol in a mass ratio of choline chloride:glycerol = 1:(3-5). (2) Extraction of hemicellulose: Add acetone to the first precipitate, stir magnetically, centrifuge, repeat three times to obtain the second precipitate; then add alkaline solution to the second precipitate, stir, and let stand to obtain the third precipitate and supernatant; then adjust the pH of the supernatant to neutral and then perform alcohol precipitation and freeze drying to obtain hemicellulose; (3) Extraction of cellulose: The precipitate was repeatedly washed with ethanol and freeze-dried to obtain cellulose; The preparation steps of the eutectic solvent are as follows: The choline chloride and glycerol were mixed in the above proportions and heated and stirred at a constant temperature for 2-3 hours, and then kept at 80°C for 1-2 hours to prepare a eutectic solvent. The constant temperature heating temperature is 80-95℃; The preparation steps for the high-purity insoluble dietary fiber are as follows: Peak amylase and neutral protease were added to soybean residue powder in sequence for enzymatic hydrolysis. Then the pH of the mixture was adjusted to 4.5±0.02, and amyloglucosidase was added for enzymatic hydrolysis. Distilled water was added to the final hydrolysate and the mixture was allowed to stand for clarification, centrifuged for alcohol precipitation, filtered, and freeze-dried to obtain high-purity insoluble dietary fiber. The concentration of the alkali solution in step (2) is 1-2.2 mol / L.
2. The method for stepwise extraction of lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber according to claim 1, characterized in that, The ratio of soybean residue powder, peak amylase, neutral protease and amyloglucosidase is 5g:0.5mL:1.5mL:2mL.
3. The method for stepwise extraction of lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber according to claim 2, characterized in that, The enzyme activities of peak amylase, neutral protease, and amylase were 40,000 U / g, 500,000 U / g, and 100,000 U / g, respectively.
4. The method for stepwise extraction of lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber according to claim 1, characterized in that, The magnetic stirring time in step (2) is 2-2.5 hours and the magnetic stirring speed is 8000-8500 rpm.
5. The method for stepwise extraction of lignin, cellulose, and hemicellulose from high-purity insoluble dietary fiber according to claim 1, characterized in that, The centrifugation time in step (2) is 10 min.