Extraction method of plant polyphenol and lignin

Abstract

The invention provides a method for extracting plant polyphenol and lignin. The extraction method comprises the following steps: S1) mixing an extraction raw material and a first solvent for a first reaction to obtain a first product; the extraction raw material is enzymatic hydrolysis lignin, and the material-liquid ratio of the extraction raw material to the first solvent is 1: (10-40) g / mL; carrying out solid-liquid separation on the first product to obtain a first solid and a first liquid; s2) concentrating the first liquid to obtain plant polyphenol, and S3) performing acid treatment on the first solid to obtain lignin.The method can solve the problems that in the prior art, plant polyphenol cannot be obtained through an extraction method, and loss of lignin is large, and is suitable for the technical field of lignin treatment.

Description

Technical Field

[0001] This invention relates to the field of lignin treatment technology, and more specifically, to a method for extracting plant polyphenols and lignin. Background Technology

[0002] In the field of biochemistry, the production of enzymatically hydrolyzed lignin is closely related to the biomass conversion process. It is a product obtained by cellulase in the enzymatic hydrolysis and saccharification of cellulose and hemicellulose in biomass. The composition of enzymatically hydrolyzed lignin is complex, including not only lignin itself but also cellulose, plant polyphenols, and trace amounts of hemicellulose. Plant polyphenols, as a class of secondary metabolites widely found in plants, exhibit rich biological activities due to their multiple phenolic hydroxyl groups, such as antioxidant properties, prevention of Alzheimer's disease, anti-inflammatory, antibacterial, and antitumor effects. This makes them highly promising for the development of high-value-added products such as pharmaceuticals, food additives, and cosmetics.

[0003] However, existing enzymatic lignin utilization technologies mainly focus on the modification and purification of lignin, neglecting the presence and value of plant polyphenols. Specifically, current technical solutions, such as the lignin-based sulfonate preparation method disclosed in patent application CN117209795A, involve using alkali lignin, enzymatically hydrolyzed lignin, etc., as raw materials, activating them under alkaline conditions, and then obtaining the target product through sulfonation and solvent washing steps; and the highly active enzymatic lignin preparation method proposed in patent application CN109485871A, which extracts lignin by treating phenol-ammonia wastewater and alkaline residue waste liquid, and by using an acidification process. Although these two solutions have achieved certain results in lignin purification, neither extracts plant polyphenols from enzymatically hydrolyzed lignin. Moreover, the aforementioned lignin extraction methods actually destroy the properties of plant polyphenols during the purification process, making it difficult to extract plant polyphenols even with subsequent separation and purification.

[0004] However, in the lignin purification technologies mentioned in the aforementioned patent applications, while the alkali dissolution and acid precipitation method can effectively improve the lignin extraction rate, it generates a large amount of difficult-to-treat waste liquid, which not only increases the cost of subsequent treatment but also burdens the environment. On the other hand, although the organic solvent method provides an alternative, the complexity of solvent recycling and the difficulty in completely removing dissolved substances from the solvent affect the efficiency of solvent recycling. Moreover, both of the above methods often damage the molecular structure of lignin during lignin extraction, resulting in a smaller molecular weight of the extracted lignin, which limits its use in demanding applications. Summary of the Invention

[0005] The main objective of this invention is to provide a method for extracting plant polyphenols and lignin, in order to solve the problems that existing extraction methods cannot obtain plant polyphenols and suffer from significant lignin loss.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for extracting plant polyphenols and lignin is provided, the method comprising: S1) mixing an extraction raw material and a first solvent to perform a first reaction to obtain a first product; the extraction raw material is enzymatically hydrolyzed lignin, and the material-to-liquid ratio of the extraction raw material to the first solvent is 1:(10-40) g / mL; separating the first product into solid and liquid components to obtain a first solid and a first liquid; S2) concentrating the first liquid to obtain plant polyphenols; and S3) acid treating the first solid to obtain lignin.

[0007] Furthermore, the first solvent includes one or more of water, methanol, ethanol, ethyl acetate, or acetone.

[0008] Furthermore, the first solvent comprises an alcohol solution with a concentration of 50-99%.

[0009] Furthermore, S1) also includes: mixing enzymatically hydrolyzed lignin, a first solvent, and excipients, and then carrying out a first reaction to obtain a first product.

[0010] Furthermore, the excipients include antioxidants.

[0011] Furthermore, the amount of excipients added is 0.1-0.5% of the total mass of the system in the first reaction.

[0012] Furthermore, the temperature of the first reaction is 40-70℃.

[0013] Furthermore, the time to the first reaction is 2-12 hours.

[0014] Furthermore, the enzymatically hydrolyzed lignin has a particle size of 40-200 mesh.

[0015] Furthermore, the concentration process is carried out at a temperature of 40-60℃.

[0016] Furthermore, the vacuum degree of the concentration process is 0.06-0.09 MPa.

[0017] Further, the acid treatment includes mixing the first solid with an acid solution to carry out a second reaction to obtain lignin.

[0018] Furthermore, the solid-liquid ratio of the first solid to the acid solution is 1:(5~20)g / mL.

[0019] Furthermore, the temperature of the second reaction is 50-80℃.

[0020] Furthermore, the second reaction time is 60-300 min.

[0021] Furthermore, the acid solution includes solutions of any one or more of the following acids: hydrochloric acid, sulfuric acid, oxalic acid, or nitric acid.

[0022] Furthermore, the volume concentration of acid in the acid solution is 1-5%.

[0023] By applying the technical solution of this invention, and through a graded extraction method, the material-to-liquid ratio of the extraction raw material (enzymatically hydrolyzed lignin) to the first solvent used for extraction is controlled. After completing the first reaction and performing solid-liquid separation, plant polyphenols in enzymatically hydrolyzed lignin can be obtained, and the structure and content of lignin are not affected in the above reactions. Further acid treatment of the solid after solid-liquid separation yields lignin. Using the extraction method of plant polyphenols and lignin of this application, both plant polyphenols and lignin in enzymatically hydrolyzed lignin can be obtained simultaneously, and both can be maintained at high contents. This opens up new avenues for the application of enzymatically hydrolyzed lignin in multiple fields, thereby further enhancing the overall utilization value and economic benefits of enzymatically hydrolyzed lignin. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0025] Terminology Explanation:

[0026] Enzymatic hydrolysis of lignin: refers to the solid obtained after treating cellulose and hemicellulose in biomass with enzymes. This solid is called enzymatic hydrolysis of lignin. In this application, enzymatic hydrolysis of lignin refers to the solid material obtained by steam explosion followed by enzymatic treatment. The biomass sources for enzymatic hydrolysis of lignin include, but are not limited to, sugarcane bagasse, corn stalks, wheat stalks, rapeseed stalks, rice stalks, or reeds.

[0027] As mentioned in the background section, existing enzymatic hydrolysis methods for lignin primarily focus on lignin extraction while neglecting the extraction of plant polyphenols. Furthermore, existing enzymatic hydrolysis methods for lignin extraction have drawbacks that negatively impact lignin content and the final result. Therefore, in this application, the inventors have attempted to develop a novel method for extracting plant polyphenols and lignin, and thus have proposed a series of protective solutions.

[0028] In a first typical embodiment of this application, a method for extracting plant polyphenols and lignin is provided. The method includes: S1) mixing the extraction raw material, a first solvent, and a first excipient to carry out a first reaction to obtain a first product; the ratio of enzymatically hydrolyzed lignin to the first solvent is 1:(10-40) g / mL (including but not limited to 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, etc.). (S1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39 or 1:40); The first product is subjected to solid-liquid separation to obtain a first solid and a first liquid; S2) The first liquid is concentrated to obtain plant polyphenols; S3) The first solid is acid-treated to obtain lignin; The extraction raw material is enzymatically hydrolyzed lignin.

[0029] In a first typical embodiment of this application, a fractional extraction method for plant polyphenols and lignin is proposed, aiming to fully utilize the complex components of enzymatically hydrolyzed lignin while avoiding the damage to the lignin structure caused by traditional extraction processes. This application uses enzymatically hydrolyzed lignin as the extraction raw material, which is mixed with a first solvent (organic solvent) to carry out a first reaction. In this application, the material-to-liquid ratio of enzymatically hydrolyzed lignin to the first solvent is controlled at 1:(10-40) g / mL, which promotes the dissolution of plant polyphenols while the lignin remains in a solid state. The purpose of the first reaction is to maximize the preservation of the original structure of lignin while efficiently extracting plant polyphenols. After the reaction, a first solid (a solid containing lignin) and a first liquid (a mixture of solvent and plant polyphenols) are obtained through solid-liquid separation technology. Subsequently, the first liquid is concentrated to recover the solvent and concentrate the plant polyphenols. After the plant polyphenol extraction, the first solid is processed. Specifically, the first solid is acid-washed with acid to remove acid-soluble ash mixed in with the lignin, rather than through traditional lignin acid purification.

[0030] In the extraction methods for plant polyphenols and lignin of this application, more solvent is not necessarily better. When the solvent is excessive, the concentration of the target component per unit volume decreases, leading to prolonged subsequent concentration time and increased energy consumption (including but not limited to rotary evaporation or vacuum distillation; any concentration method known to those skilled in the art can achieve the effect described in this application). Excessive solvent may even reduce the yield due to over-dilution. Simultaneously, excessive solvent will dissolve more non-target impurities such as polysaccharides, proteins, pigments, and tannins from the enzymatically hydrolyzed lignin, directly reducing the final purity and increasing the purification burden. Furthermore, excessive solvent means higher energy consumption for recovery, larger wastewater treatment volumes, and more severe environmental costs. For techniques sensitive to the physicochemical conditions of the system (such as ultrasound-assisted extraction and supercritical fluid extraction), excessive solvent may impair selectivity and weaken the enrichment effect of the target component. For example, in liquid-liquid extraction or two-phase separation stages, excessive solvent can easily cause emulsification or unclear interfaces, significantly reducing separation efficiency. Therefore, this application has determined the range of material-to-liquid ratio in the extraction system through a large number of experiments. Under the premise of improving extraction efficiency and product quality, the amount of solvent used is controlled at a low necessary level, so as to achieve an efficient, economical and green extraction process.

[0031] The technical solution of this application overcomes the limitations of existing technologies, namely, how to achieve efficient extraction of plant polyphenols while purifying lignin without destroying its structure. When applied to the enzymatic hydrolysis of lignin in the industry, this extraction method can further enhance the economic benefits of enzymatic hydrolysis, opening up new pathways for the comprehensive development and utilization of biomass, aligning with the concept of sustainable development, and possessing social and environmental benefits.

[0032] In step S1 of this application, the mixing reaction of the extraction raw material (enzymatically hydrolyzed lignin) with the first solvent can be carried out using various extractors well known to those skilled in the art, including but not limited to Soxhlet extractors or continuous extractors. The selection of these extractors is based on the reaction conditions and raw material characteristics, ensuring efficient extraction of plant polyphenols without damaging the structure and extraction efficiency of lignin.

[0033] In the subsequent solid-liquid separation stage, any solid-liquid separation method known to those skilled in the art, such as centrifugation, vacuum filtration, or pressure filtration, can be used.

[0034] This application allows for the introduction of auxiliary processes in the first reaction, such as stirring, ultrasound, and microwave treatment. These auxiliary processes aim to improve the contact efficiency between the solvent and the raw materials, promoting the dissolution of plant polyphenols. For example, when using microwave assistance, the power can be in the range of 300-600W, while with ultrasound assistance, the power is controlled between 150-300W. To prevent the negative impact of localized overheating on the activity of plant polyphenols, these auxiliary processes are performed in batches, with the interval between each operation set at 3-6 minutes, improving reaction controllability and product quality. Those skilled in the art can select the appropriate process based on actual production needs.

[0035] In a preferred embodiment, the first solvent includes one or more of water, methanol, ethanol, ethyl acetate, or acetone. Preferably, the first solvent is a 50-99% alcohol solution, more preferably a 70-98% alcohol solution.

[0036] The first solvent of this application is preferably one or a combination of water, methanol, ethanol, ethyl acetate or acetone. These solvents have good solubility and affinity for plant polyphenols, which can effectively promote the release of plant polyphenols from lignin composite materials, while having little impact on the structure of lignin.

[0037] In a preferred embodiment, the enzymatically hydrolyzed lignin has a particle size of 40-200 mesh (including but not limited to 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200 mesh).

[0038] The particle size of the enzymatically hydrolyzed lignin in this application is preferably 40-200 mesh, which increases the contact area between the raw material and the solvent, improves the extraction efficiency, and helps to simplify the post-processing, such as solid-liquid separation and drying, thereby reducing energy consumption and cost.

[0039] In a preferred embodiment, the temperature of the first reaction is 40-70°C (including but not limited to 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C), preferably 60-70°C.

[0040] In a preferred embodiment, the time for the first reaction is 2-12 hours (including but not limited to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 hours).

[0041] In this application, the temperature of the first reaction is preferably set at 40-70℃, preferably 60-70℃, and the time range of the first reaction is preferably 2-12 hours. This avoids the destruction of plant polyphenol activity by high temperature, and can improve the extraction speed and efficiency. It can extract plant polyphenols under mild reaction conditions without damaging the structure and content of lignin, thus achieving a balance between extraction efficiency and product quality.

[0042] In the preferred embodiment, this application precisely controls the steps and conditions of the above reaction, from solvent selection, enzymatic hydrolysis of lignin particle size, reaction temperature to reaction time, to achieve efficient and mild fractional extraction of plant polyphenols and lignin. This series of optimization measures not only improves extraction efficiency and product purity, but also provides theoretical support for the rational utilization of resources and the value-added transformation of biomass materials.

[0043] In a preferred embodiment, S1) further includes: mixing enzymatically hydrolyzed lignin, a first solvent, and excipients to carry out a first reaction to obtain a first product.

[0044] In a preferred embodiment, the excipients include antioxidants; preferably, the antioxidants include one or more of vitamin C, sulfite compounds, or thiol compounds. Preferably, the sulfite compounds include sodium sulfite and / or sodium metabisulfite; preferably, the thiol compounds include cysteine ​​and glutamate. Preferably, the above excipients also include EDTA (which chelates metal ions, protecting the antioxidants and preventing their premature consumption).

[0045] The excipients used in this application are preferably antioxidants, more preferably vitamin C (Vc), sulfite compounds, or thiol compounds. Antioxidants can directly participate in the reaction system, exerting their antioxidant function and further enhancing the protective effect on plant polyphenols. The amount of the aforementioned excipients, such as antioxidants, needs to be precisely controlled, generally accounting for 0.1-0.5% of the total mass of the first reaction system. This proportion provides sufficient antioxidant protection without adversely affecting the reaction process, maintaining the stability of the system and the controllability of the reaction. To prevent the oxidation of plant polyphenols, in addition to adding excipients, nitrogen gas can also be introduced into the first reaction to protect the plant polyphenols. Those skilled in the art can choose any antioxidant adjustment method to apply to the first reaction system according to actual production needs.

[0046] In a preferred embodiment, the amount of excipient added is 0.1-0.5% of the total mass of the system in the first reaction (including but not limited to 0.1%, 0.2%, 0.3%, 0.4% or 0.5%).

[0047] In a preferred embodiment, the concentration process is carried out at a temperature of 40-60°C (including but not limited to 40°C, 45°C, 50°C, 55°C or 60°C).

[0048] In a preferred embodiment, the vacuum degree of the concentration process is 0.06-0.09 MPa (including but not limited to 0.06, 0.07, 0.08 or 0.09 MPa).

[0049] The concentration process in this application involves recovering the first solvent and concentrating the plant polyphenol extract. To ensure effective recovery of the first solvent and high-purity concentration of the plant polyphenols, the concentration temperature is precisely controlled within the relatively mild range of 40-60°C. This temperature range promotes the evaporation rate of the solvent while avoiding the decomposition or structural changes of the plant polyphenols that may be caused by high temperatures, thereby improving the quality and stability of the product.

[0050] This application controls the concentration process under vacuum conditions of 0.06-0.09 MPa, which accelerates the evaporation process, reduces the actual evaporation temperature, and decreases energy consumption. The high vacuum level facilitates rapid solvent evaporation at lower actual operating temperatures, while avoiding the adverse effects of high temperatures on plant polyphenols, thus achieving efficient concentration of the plant polyphenol extract and solvent recovery and reuse.

[0051] In a preferred embodiment, the acid treatment includes mixing a first solid with an acid solution to carry out a second reaction to obtain lignin.

[0052] In a preferred embodiment, the solid-liquid ratio of the first solid to the acid solution is 1:(5~20) g / mL (including but not limited to 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20 g / mL). Preferably, it is 1:10~20.

[0053] In a preferred embodiment, the temperature of the second reaction is 50-80°C (including but not limited to 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C).

[0054] In a preferred embodiment, the second reaction time is 60-300 min (including but not limited to 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 or 300 min), preferably 120-300 min.

[0055] In a preferred embodiment, the acid solution comprises a solution of any one or more of the following acids: hydrochloric acid, sulfuric acid, oxalic acid, or nitric acid.

[0056] In a preferred embodiment, the volume concentration of acid in the acid solution is 1-5% (including but not limited to 1, 2, 3, 4 or 5%).

[0057] Although this application involves an acid washing process, its core is not the traditional acid purification of lignin, but rather the removal of acid-soluble ash remaining in lignin using a low concentration of acid (such as hydrochloric acid or sulfuric acid, with a concentration of approximately 1-5%) under mild conditions (50-80℃), aiming to improve the purity and quality of lignin. This process not only avoids damage to the molecular structure of lignin but also effectively improves the flexibility and breadth of subsequent applications.

[0058] In this application, the solid-liquid ratio of the first solid to the acid solution is precisely controlled within the range of 1:(5~20) g / mL. This ratio is set based on considerations of reaction efficiency and product purity. A higher solvent ratio helps to improve the solubility of ash while avoiding excessive dissolution of lignin and maintaining its inherent form. The selection of the solid-liquid ratio needs to take into account the properties of the raw materials, reaction conditions, and the choice of acid to ensure the sufficiency of the reaction and the high quality of the product.

[0059] In this application, the temperature of the second reaction is preferably set at 50-80°C. o The C-range temperature range allows for effective dissolution of ash while avoiding the risk of lignin molecule degradation at high temperatures. This mild reaction temperature helps maintain the structural integrity and molecular weight of lignin, thus ensuring its performance in subsequent applications.

[0060] The preferred acid solution used in the application is a solution of one or more mixed acids, such as hydrochloric acid, sulfuric acid, oxalic acid, or nitric acid. These acids are widely used due to their suitable dissolving power and compatibility with lignin. The acid concentration is controlled within 1-5%, a concentration range that effectively removes ash without causing irreversible damage to the lignin structure.

[0061] By precisely controlling the solid-liquid ratio, reaction temperature, reaction time, and the selection and concentration of the acid solution in the acid washing process (second reaction) of the first solid, this application has constructed an efficient and mild lignin acid treatment process. This process not only significantly improves the purity of lignin but also maintains the integrity of its molecular structure, providing technical support for the optimization of enzymatic hydrolysis and graded utilization of lignin.

[0062] The extraction method described in this application uses a primary solvent primarily for extracting plant polyphenols, rather than dissolving lignin. Through low-temperature, antioxidant protection, and neutral environmental conditions, plant polyphenols were successfully extracted without altering the physical state of lignin. This method significantly differs from traditional organic solvent extraction of lignin using high-temperature, high-pressure, and alkaline conditions. While the latter effectively dissolves lignin, it also damages its structure, reduces its molecular weight, and limits its subsequent applications. The fractional extraction technology in this application not only preserves the structural integrity of lignin but also achieves efficient recovery of plant polyphenols, providing new possibilities for the high-value utilization of enzymatically hydrolyzed lignin, particularly demonstrating application potential in fields with high raw material quality requirements, such as pharmaceuticals, food, and cosmetics.

[0063] The beneficial effects of this application will be explained in more detail below with reference to specific embodiments.

[0064] The methods for preparing enzymatically hydrolyzed lignin in this application are as follows: biomass (e.g., corn stalks, sugarcane bagasse, wheat straw, rice straw) is subjected to steam explosion treatment, and then cellulose and hemicellulose are decomposed using a composite bio-enzyme preparation (which includes cellulase, protease, and pectinase). The remaining recalcitrant solid material is the enzymatically hydrolyzed lignin. The reagents, conditions, and parameter settings used in the preparation method are conventional conditions and parameters in existing enzymatic lignin preparation processes, and are well known to those skilled in the art.

[0065] The enzymatically hydrolyzed lignin and plant polyphenol extraction method of this application can be any of the existing enzymatically hydrolyzed lignin methods used to process lignin-containing biomass materials (including but not limited to sugarcane bagasse, sugarcane leaves, corn stalks, wheat stalks, rapeseed stalks, rice stalks, or reeds).

[0066] Example 1

[0067] 1. Place 40-200 mesh sugarcane bagasse-derived enzymatically hydrolyzed lignin into a round-mouth flask equipped with a condenser. Add 95% ethanol solvent and 1% vitamin C at a material-to-liquid ratio of 1:20 g / mL. Maintain the reaction temperature at 60℃ and use intermittent sonication for 2 hours (30 min intervals). After sonication, remove the flask and allow it to react at 60℃ for another 2 hours (first reaction). After the reaction is complete and cooled to room temperature, the first product is obtained. Centrifuge to separate the solid and liquid components, yielding a solid sample (first solid) and a liquid sample (first liquid).

[0068] 2. Place the liquid sample (first liquid) into a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder (plant polyphenols) at 40℃ and 0.06 MPa.

[0069] 3. After the solid in step 1 (first solid) is dried in an oven at 80℃, 2% hydrochloric acid is added at a solid-liquid ratio of 1:10 and reacted at 60℃ with a stirring rate of 200 rpm for 2 hours. After filtration, the solid sample is washed until neutral, dried and weighed to obtain solid (lignin). The sample mass and lignin content are then tested.

[0070] 4. Under the above conditions, the extraction rate of plant polyphenols was 88%, and the lignin content was 60%.

[0071] Example 2

[0072] 1. Take 40-200 mesh sugarcane bagasse enzymatically hydrolyzed lignin and put it into a round-mouth flask equipped with a condenser. Add 95% ethanol solvent and 5% vitamin C at a material-to-liquid ratio of 1:40 g / mL. The reaction temperature is 70℃. Use intermittent sonication for 30 mins for 4 h. After taking it out, react it at 70℃ for 2 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0073] 2. Place the liquid sample in a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 50°C.

[0074] 3. After the solid in step 1 is dried in an oven at 80℃, 2% hydrochloric acid is added at a solid-liquid ratio of 1:20 and the mixture is stirred at 200 rpm for 2 hours at 60℃. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0075] 4. Under the above conditions, the extraction rate of plant polyphenols was 86%, and the lignin content was 59%.

[0076] Example 3

[0077] 1. Take 40-200 mesh corn straw-derived enzymatically hydrolyzed lignin and put it into a round-mouth flask equipped with a condenser. Add 95% ethanol solvent and 0.3% vitamin C at a material-to-liquid ratio of 1:10 g / mL. The reaction temperature is 70℃. Use intermittent sonication for 30 min and 3 h. After taking it out, react it at 70℃ for 3 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0078] 2. Place the liquid sample in a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 60°C and 0.08 MPa.

[0079] 3. After the solid in step 1 is dried in an oven at 80℃, 3% hydrochloric acid is added at a solid-liquid ratio of 1:10 and the mixture is stirred at 200 rpm for 3 hours at 60℃. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0080] 4. Under the above conditions, the extraction rate of plant polyphenols was 89%, and the lignin content was 62%.

[0081] Example 4

[0082] 1. Take 40-200 mesh corn straw-derived enzymatically hydrolyzed lignin and put it into a round-mouth flask equipped with a condenser. Add 95% ethanol solvent and 1% vitamin C at a material-to-liquid ratio of 1:15 g / mL. The reaction temperature is 70℃. Use intermittent sonication for 30 min and 3 h. After taking it out, react it at 70℃ for 4 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0083] 2. Place the liquid sample in a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 50°C and 0.09 MPa.

[0084] 3. After the solid in step 1 is dried in an oven at 80℃, 3% hydrochloric acid is added at a solid-liquid ratio of 1:15 and the mixture is stirred at 250 rpm for 3.5 h at 70℃. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0085] 4. Under the above conditions, the extraction rate of plant polyphenols was 86%, and the lignin content was 59%.

[0086] Example 5

[0087] 1. Take 40-200 mesh reed straw-derived enzymatically hydrolyzed lignin and place it in a round-mouth flask equipped with a condenser. Add 95% ethanol solvent and 0.1% vitamin C at a material-to-liquid ratio of 1:30 g / mL. The reaction temperature is 70℃. Use intermittent sonication for 30 min, and sonicate for 3 h. After taking it out, react it at 70℃ for 2 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0088] 2. Place the liquid sample in a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 40°C and 0.06 MPa.

[0089] 3. After the solid in step 1 is dried in an oven at 80℃, 5% hydrochloric acid is added at a solid-liquid ratio of 1:10 and the mixture is stirred at 250 rpm for 2 hours at 80℃. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0090] 4. Under the above conditions, the extraction rate of plant polyphenols was 85%, and the lignin content was 62%.

[0091] Example 6

[0092] 1. Take 40-200 mesh reed straw-derived enzymatically hydrolyzed lignin and place it in a round-mouth flask equipped with a condenser. Add 95% ethanol solvent and 0.1% vitamin C at a material-to-liquid ratio of 1:20 g / mL. The reaction temperature is 70℃. Use intermittent sonication for 30 mins, and sonicate for 1.5 h. After taking it out, react it at 70℃ for 2 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0093] 2. Place the liquid sample in a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 40°C and 0.06 MPa.

[0094] 3. After the solid in step 1 is dried in an 80-degree oven, 2% hydrochloric acid is added at a solid-liquid ratio of 1:10 and the mixture is stirred at 250 rpm for 2 hours at 80 degrees. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0095] 4. Under the above conditions, the extraction rate of plant polyphenols was 83%, and the lignin content was 58%.

[0096] Example 7

[0097] Compared with Example 1, the only difference is that the material-to-liquid ratio in step 3 is 1:60.

[0098] In this embodiment, the extraction rate of plant polyphenols was 75%, and the lignin content was 55%.

[0099] Example 8

[0100] Compared with Example 1, the only difference is that the solid-liquid ratio in step 3 is 1:50.

[0101] In this embodiment, the extraction rate of plant polyphenols was 77%, and the lignin content was 57%.

[0102] Example 9

[0103] Compared with Example 1, the only difference is that the solid-liquid ratio in step 3 is 1:1.

[0104] In this embodiment, the extraction rate of plant polyphenols was 50%, and the lignin content was 45%.

[0105] Example 10

[0106] Compared with Example 1, the only difference is that the solid-liquid ratio in step 3 is 1:2.

[0107] In this embodiment, the extraction rate of plant polyphenols was 52%, and the lignin content was 46%.

[0108] Example 11

[0109] Compared to Example 3, the only difference is that the ethanol concentration in step 1 is 80%.

[0110] In this embodiment, the extraction rate of plant polyphenols was 86%, and the lignin content was 60%.

[0111] Example 12

[0112] Compared with Example 3, the only difference is that the total ultrasonic extraction time in step 1 is 5 hours.

[0113] In this embodiment, the extraction rate of plant polyphenols was 80%, and the lignin content was 53%.

[0114] Example 13

[0115] Compared with Example 5, the only difference is that the extraction temperature in step 1 is 30°C.

[0116] In this embodiment, the extraction rate of plant polyphenols was 70%, and the lignin content was 45%.

[0117] Example 14

[0118] Compared with Example 5, the only difference is that the temperature in step 1 is 80°C.

[0119] In this embodiment, the extraction rate of plant polyphenols was 82%, and the lignin content was 50%.

[0120] Comparative Example 1

[0121] 1. Take 40-200 mesh sugarcane bagasse enzymatically hydrolyzed lignin and put it into a round-mouth flask equipped with a condenser. Add 50% ethanol solvent at a material-to-liquid ratio of 1:5 g / mL. The reaction temperature is 60℃. Use intermittent sonication for 40 min, and sonicate for 0.5 h. After taking it out, react it at 70℃ for 1 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0122] 2. Place the liquid sample into a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 40°C.

[0123] 3. After the solid in step 1 is dried in an oven at 80℃, 1% hydrochloric acid is added at a solid-liquid ratio of 1:5 and the mixture is stirred at 200 rpm for 1 hour at 50℃. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0124] 4. The extraction rate of plant polyphenols in this comparative example is 29%, and the lignin content is 45%.

[0125] Because of the adjustment of the material-liquid ratio in step 1, other parameters in this comparative example were also adjusted accordingly to make the reaction system reach the ideal reaction conditions in theory.

[0126] Comparative Example 2

[0127] 1. Take 40-200 mesh sugarcane bagasse enzymatically hydrolyzed lignin and put it into a round-mouth flask equipped with a condenser. Add 75% ethanol solvent at a material-to-liquid ratio of 1:5 g / mL. The reaction temperature is 60℃. Use intermittent sonication for 10 min for 0.5 h. After taking it out, react it at 60℃ for 1 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0128] 2. Place the liquid sample into a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 40°C.

[0129] 3. After the solid in step 1 is dried in an oven at 80℃, 1% hydrochloric acid is added at a solid-liquid ratio of 1:5 and the mixture is stirred at 200 rpm for 1 hour at 50℃. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0130] 4. The extraction rate of plant polyphenols in this comparative example is 45%, and the lignin content is 48%.

[0131] Because of the adjustment of the material-liquid ratio in step 1, other parameters in this comparative example were also adjusted accordingly to make the reaction system reach the ideal reaction conditions in theory.

[0132] Comparative Example 3

[0133] 1. Take 40-200 mesh corn straw-derived enzymatically hydrolyzed lignin and put it into a round-mouth flask equipped with a condenser. Add 70% ethanol solvent and 0.01% Vc at a material-to-liquid ratio of 1:5 g / mL. The reaction temperature is 50℃. Use intermittent sonication for 20 mins, and sonicate for 1 h. After taking it out, react it at 50℃ for 1 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0134] 2. Place the liquid sample into a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 40°C.

[0135] 3. After the solid in step 1 is dried in an oven at 80°C, 3% hydrochloric acid is added at a solid-liquid ratio of 1:5 and the mixture is stirred at 250 rpm for 3.5 h at 70°C. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0136] 4. The extraction rate of plant polyphenols in this comparative example is 40%, and the lignin content is 44%.

[0137] Because of the adjustment of the material-liquid ratio in step 1, other parameters in this comparative example were also adjusted accordingly to make the reaction system reach the ideal reaction conditions in theory.

[0138] Comparative Example 4

[0139] 1. Take 40-200 mesh corn straw-derived enzymatically hydrolyzed lignin and place it in a round-mouth flask equipped with a condenser. Add 60% ethanol solvent and 0.01% vitamin C at a material-to-liquid ratio of 1:50 g / mL. The reaction temperature is 60℃. Use intermittent sonication for 20 mins, and sonicate for 1 h. After removing the sample, react it at 50℃ for 1 h. After the reaction is completed and cooled to room temperature, use centrifugation to separate the solid and liquid samples to obtain solid and liquid samples.

[0140] 2. Place the liquid sample into a rotary evaporator for evaporation and concentration and ethanol recovery until the ethanol recovery rate reaches 90%. The concentrated liquid sample is then vacuum dried to a solid powder at 40°C.

[0141] 3. After the solid in step 1 is dried in an oven at 80°C, 3% hydrochloric acid is added at a solid-liquid ratio of 1:5 and the mixture is stirred at 250 rpm for 3.5 h at 70°C. After filtration, the solid sample is washed until neutral, dried, weighed, and the mass and lignin content of the solid sample are tested.

[0142] 4. The extraction rate of plant polyphenols in this comparative example is 38%, and the lignin content is 43%.

[0143] Because of the adjustment of the material-liquid ratio in step 1, other parameters in this comparative example were also adjusted accordingly to make the reaction system reach the ideal reaction conditions in theory.

[0144] Comparative Example 5

[0145] Compared with Example 3, the only difference is the solid-liquid ratio of 1:60g / mL in step 1.

[0146] In this comparative example, the extraction rate of plant polyphenols was 84%, and the lignin content was 58%.

[0147] Comparative Example 6

[0148] Compared with Example 3, the only difference is that the solid-liquid ratio in step 1 is 1:1 g / mL.

[0149] In this comparative example, the extraction rate of plant polyphenols was 15%, and the lignin content was 43%.

[0150] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: This application provides a method for the graded utilization of enzymatically hydrolyzed lignin, the core of which lies in achieving efficient and gentle extraction of plant polyphenols from enzymatically hydrolyzed lignin, while simultaneously completing the non-destructive purification of lignin. Through optimized solvent extraction steps, the efficiency of extracting plant polyphenols can reach 85%-90% while maintaining the structural integrity of lignin, thus recovering this high-value-added component. Secondly, the use of a gentle acid washing process for lignin purification not only effectively removes acid-soluble ash impurities but also ensures the structural stability of lignin molecules, avoiding the potential damage to lignin caused by traditional purification methods, and obtaining a high content of lignin. This application solves the problems of low utilization efficiency of plant polyphenols and easy destruction of lignin in the prior art of enzymatically hydrolyzed lignin, promoting the development of the lignin industry.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for extracting plant polyphenols and lignin, characterized by, The extraction method comprises: S1) mixing an extraction raw material and a first solvent to perform a first reaction to obtain a first product; The extraction raw material is enzymatic hydrolysis lignin, and a solid-liquid ratio of the extraction raw material to the first solvent is 1:(10-40) g / mL; The first product is subjected to solid-liquid separation to obtain a first solid and a first liquid; S2) the first liquid is subjected to concentration treatment to obtain plant polyphenols; S3) the first solid is subjected to acid treatment to obtain lignin.

2. The extraction method according to claim 1, characterized in that, The first solvent comprises one or more of water, methanol, ethanol, ethyl acetate or acetone.

3. The extraction method according to claim 2, characterized in that, The first solvent comprises an alcohol solution with a concentration of 50-99%.

4. The extraction method of claim 1, wherein, The S1) further comprises: after the enzymatic hydrolysis lignin, the first solvent and an auxiliary material are mixed, the first reaction is performed to obtain the first product.

5. The extraction method according to claim 4, characterized in that, The auxiliary material comprises an antioxidant.

6. The extraction method of claim 4, wherein, An addition amount of the auxiliary material is 0.1-0.5% of a total mass of a system of the first reaction.

7. The extraction method of claim 4, wherein, The first reaction is performed at a temperature of 40-70 DEG C.

8. The extraction method of claim 7, wherein, The first reaction is performed for a time of 2-12 h.

9. The extraction method of claim 1, wherein, The enzymatic hydrolysis lignin has a particle size of 40-200 meshes.

10. The extraction method of claim 1, wherein, The concentration treatment is performed at a temperature of 40-60 DEG C.

11. The extraction method of claim 10, wherein, A vacuum degree of the concentration treatment is 0.06-0.09 MPa.

12. The extraction method of claim 1, wherein, The acid treatment comprises: the first solid is mixed with an acid solution to perform a second reaction to obtain the lignin.

13. The extraction method of claim 12, wherein, A solid-liquid ratio of the first solid to the acid solution is 1:(5-20) g / mL.

14. The extraction method of claim 12, wherein, The second reaction is performed at a temperature of 50-80 DEG C.

15. The extraction method of claim 14, wherein, The second reaction is performed for a time of 60-300 min.

16. The extraction method of claim 12, wherein, The acid solution comprises a solution of any one or more of the following acids: hydrochloric acid, sulfuric acid, oxalic acid or nitric acid.

17. The extraction method of claim 16, wherein, A volume concentration of the acid in the acid solution is 1-5%.