A plant cell wall suberin layer microcapsule and a method of preparing the same

Abstract

The application discloses a plant cell wall suberin layer microcapsule and a preparation method thereof, and relates to the technical field of high-value utilization of plant resources and bio-based new materials. After pretreatment, the plant suberin tissue is placed in a dissociation reagent for reaction, and a plant cell wall suberin layer microcapsule is obtained through purification. The dissociation reagent is an acid dissociation solution or an alkaline dissociation solution. The acid dissociation solution comprises an acid medium and an oxidizing agent, and the alkaline dissociation solution comprises an alkaline medium and an oxidizing agent. The oxidizing agent is one or more of hydrogen peroxide, sodium hypochlorite and sodium chlorite. The acid dissociation solution and the alkaline dissociation solution can further comprise a decomposition agent according to the situation, and the decomposition agent is a cell wall degrading enzyme or a eutectic solvent. Through the precise dissociation technology, the non-suberin components are removed without damaging the structure of the suberin layer, and the microcapsule with a complete suberin layer, a continuous and dense wall layer and a hollow cavity is obtained. The size and appearance of the microcapsule are highly consistent with those of the natural suberin cell, the surface properties can be adjusted, and the natural microstructure is retained.

Description

Technical Field

[0001] This invention relates to the fields of high-value utilization of plant resources and bio-based new materials, and in particular to a plant cell wall cork layer microcapsule and its preparation method. Background Technology

[0002] Suberin is a natural hydrophobic biopolymer polyester found in plant cell walls, primarily in the cell walls of cork tissues (such as bark and tuber periderm). It plays a crucial role in plant protection and water regulation. Suberin possesses high chemical stability and hydrophobicity, making it a promising candidate for a wide range of applications in functional materials.

[0003] Currently, research on obtaining suberin from cork tissue mainly falls into two categories: one is chemical depolymerization, which uses alkaline alcohol solutions to depolymerize suberin polyesters into suberin monomers and their oligomers. This method only yields low-molecular-weight compounds, completely destroying the natural three-dimensional structure of suberin; the other is solvent extraction, which uses organic solvents to extract only soluble components. This method also yields low-molecular-weight suberin compounds and still cannot obtain the insoluble suberin polyester structural framework with complete composition and structure. This has become a key obstacle to studying the intrinsic properties of suberin and utilizing it to create new materials.

[0004] In the prior art, CN119662516A discloses a method for isolating bark cork cells. However, this method yields microcapsules with intact cell morphology, whose capsule walls contain large amounts of lignin and polysaccharides (each component content greater than 5%), rather than pure cork structure and composition. The presence of non-cork layer components (lignin and polysaccharides) affects the structure and physicochemical properties of the cork layer, hindering the exploration of the intrinsic properties of cork, such as its physicochemical properties, from a fundamental research perspective. It also hinders the design and development of new materials using the pure cork layer structure and composition.

[0005] Therefore, how to precisely remove interfering components such as lignin and polysaccharides from cork tissue without destroying the natural three-dimensional chemical structure and composition of cork, and obtain relatively pure "cork layer microcapsules" (with polysaccharide and lignin contents of less than 5%), has become an urgent technical problem to be solved in the field of cork. Summary of the Invention

[0006] To address the aforementioned limitations of existing technologies, the present invention aims to provide plant cell wall suberin layer microcapsules and their preparation method. This invention selects plant suberin tissue as raw material, pre-treats it, and then reacts it in a dissociation reagent to obtain plant cell wall suberin layer microcapsules after purification. The dissociation reagent is either an acidic or alkaline dissociation solution; the acidic dissociation solution includes an acidic medium and an oxidant; the alkaline dissociation solution includes an alkaline medium and an oxidant; the oxidant is one or more of hydrogen peroxide, sodium hypochlorite, and sodium chlorite. The acidic and alkaline dissociation solutions may also include a decomposing agent, which is a eutectic solvent or a cell wall degrading enzyme specifically used to degrade cell wall polysaccharides and / or lignin. This invention utilizes a precise molecular surgical dissociation technique to remove a large amount of non-suberin components without damaging the suberin layer structure, obtaining microcapsules that retain the continuous dense structure and hollow cavity morphology of the suberin layer. Their size and morphology are highly consistent with natural suberin cells, and their surface properties are tunable, preserving the natural microscopic transport structure.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing plant cell wall suberein layer microcapsules, comprising the following steps: (1) After pretreatment of plant cork tissue, cork tissue raw material is obtained; (2) The cork tissue raw material was added to the dissociation reagent for reaction. After the reaction was completed, the precipitate was centrifuged and collected. After washing and drying, plant cell wall cork layer microcapsules were obtained. The dissociation reagent is either an acidic dissociation solution or a basic dissociation solution; wherein, the acidic dissociation solution is composed of an acidic medium and an oxidizing agent, and the basic dissociation solution is composed of a basic medium and an oxidizing agent; The oxidant is one or more of sodium hypochlorite, hydrogen peroxide, and sodium chlorite.

[0008] Preferably, both the acidic and alkaline dissociation solutions may include a decomposing agent, which may be a eutectic solvent and / or a cell wall degrading enzyme.

[0009] Furthermore, the eutectic solvent is prepared by mixing hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:(2-4); wherein the hydrogen bond acceptor is choline chloride and the hydrogen bond donor is an organic acid or urea.

[0010] Furthermore, the cell wall degrading enzyme refers to an enzyme used to degrade cell wall polysaccharides and / or lignin, and is one or more of cellulase, hemicellulase, pectinase, and laccase.

[0011] Preferably, the acidic medium is an organic acid or an inorganic acid, and the alkaline medium is an organic base or an inorganic base.

[0012] Furthermore, the acidic medium is one or more of oxalic acid, lactic acid, citric acid, formic acid, and acetic acid; the alkaline medium is sodium hydroxide or potassium hydroxide.

[0013] Preferably, in the acidic dissociation solution, the final concentration of the acidic medium is 1-10 mol / L and the final concentration of the oxidant is 1-10 mol / L; in the alkaline dissociation solution, the final concentration of the alkaline medium is 0.01-5 mmol / L and the final concentration of the oxidant is 1-10 mol / L.

[0014] Preferably, in the acidic dissociation solution, when the decomposing agent is a cell wall degrading enzyme, the amount added is 0.5-5 FPU / g cork tissue raw material, and when the decomposing agent is a eutectic solvent, the final concentration is 0.5-1.5 mol / L; in the alkaline dissociation solution, when the decomposing agent is a cell wall degrading enzyme, the amount added is 2-5 FPU / g cork tissue raw material, and when the decomposing agent is a eutectic solvent, the final concentration is 0.5-2.5 mol / L.

[0015] Preferably, in step (1), the plant cork tissue is the bark of a woody plant rich in cork cells or the periderm of a herbaceous plant.

[0016] Furthermore, the woody plants rich in cork cells were selected from cork oak, eucommia, birch, cork oak (also known as European cork oak), and phellodendron; the herbaceous plants were selected from potatoes.

[0017] As a preferred option, in step (1), the specific operation of pretreatment is as follows: after crushing the plant cork tissue to a particle size of 20-100 mesh, wash it 1-2 times, each time for 1-10 minutes, and then dry it at 50-70℃ to obtain cork tissue raw material.

[0018] As a preferred option, in step (2), the ratio of cork tissue raw material to dissociation reagent is 30g:(600-1000)mL.

[0019] As a preferred option, in step (2), physical enhancement methods may be used as needed during the reaction process.

[0020] Furthermore, physical strengthening methods include one or more combinations of ultrasonic treatment, microwave treatment, stirring, and grinding.

[0021] Preferably, in step (2), the reaction temperature is 20-80℃ and the reaction time is 1.5-70h.

[0022] In a second aspect, the present invention provides plant cell wall suberin layer microcapsules prepared by the above-described preparation method.

[0023] Preferably, the plant cell wall suberin layer microcapsules are hollow sac-like structures with continuous cavities in the wall, and the thickness of the sac wall is 100-2000 nm.

[0024] Preferably, the instantaneous surface water contact angle of the plant cell wall subere layer microcapsules is 20°-110°.

[0025] Preferably, the plant cell wall suberein layer microcapsules retain the original microscopic transport structure of the plant cell wall.

[0026] Preferably, the lignin content and polysaccharide content in the capsule wall of the continuous hollow microcapsule structure are less than 5% by mass.

[0027] The beneficial effects of this invention are: 1. This invention selects plant cork tissue as raw material, pre-treats it, and then reacts it with a dissociation reagent to obtain plant cell wall cork layer microcapsules after purification. Using a precise "molecular scalpel" dissociation technique, microcapsules with a continuous, dense wall structure and hollow cavity morphology that completely preserve the cork layer were obtained for the first time. Their size and morphology are highly consistent with natural cork cells, completely different from traditional amorphous small / low molecular weight cork extracts. This provides an ideal model for studying the intrinsic physicochemical properties of cork, filling a gap in this field.

[0028] 2. This invention uses a "selective peeling" strategy to remove interfering components (polysaccharides, lignin, etc.) without damaging the cork layer structure. The chemical structure of the resulting product is consistent with the natural state, avoiding the damage caused by the traditional alkali-alcohol depolymerization method.

[0029] 3. The plant cell wall suberin layer microcapsules prepared in this invention possess a well-defined aggregated structure. Their crystallinity was measured to be 1-20%, exhibiting a two-phase structure characteristic of crystalline and amorphous coexistence. Furthermore, the prepared plant cell wall suberin layer microcapsules exhibit well-defined surface properties, with an instantaneous water contact angle of 20-110°, demonstrating hydrophilic / hydrophobic characteristics. In addition, thermogravimetric analysis showed that the initial decomposition temperature of the prepared plant cell wall suberin layer microcapsules was ~250℃, exhibiting good thermal stability. These fundamental data provide a scientific basis for subsequent functional applications.

[0030] 4. The plant cell wall suberin layer microcapsules prepared by this invention retain the natural microscopic transport structure, laying the foundation for constructing high-performance carrier materials. These microcapsules can serve as structural / functional building blocks to construct advanced suberin-based materials for application in high-end fields such as biomedicine, energy and environment, and electronic information.

[0031] 5. This invention provides a variety of dissociation reagent systems that can be selected and optimized based on plant cork tissues from different sources and production costs, which is beneficial for industrial production and promotion.

[0032] 6. The plant cell wall suberin layer microcapsules prepared by this invention can be used to reveal the intrinsic microstructure, composition characteristics, and physicochemical properties of suberin, and can also serve as a basic building block of "cell wall microstructure materials science", with broad scientific and applied value. Attached Figure Description

[0033] Figure 1 SEM image of plant cell wall subere layer microcapsules prepared in Example 1 at 20 μm; Figure 2 SEM image of plant cell wall subere layer microcapsules prepared in Example 1 at 5 μm; Figure 3 Optical photograph of the plant cell wall subere layer microcapsules prepared in Example 1; Figure 4 Optical microscope image of plant cell wall subere layer microcapsules prepared in Example 1; Figure 5 Optical microscope image of plant cell wall subere layer microcapsules prepared in Example 2; Figure 6 Optical microscope image of plant cell wall subere layer microcapsules prepared in Example 3; Figure 7 Optical microscope image of plant cell wall subere layer microcapsules prepared in Example 4; Figure 8 Photograph of the cork material prepared in Comparative Example 1; Figure 9 Photograph of the cork material obtained in Comparative Example 2; Figure 10 : Optical microscope image of the cork material prepared in Comparative Example 2; Figure 11 Optical photograph of cork cells obtained in Comparative Example 3; Figure 12 FTIR images of cork tissue raw materials, plant cell wall cork layer microcapsules prepared in Examples 1-4, cork prepared in Comparative Example 1, and cork cells prepared in Comparative Example 3. Figure 13 XRD patterns of plant cell wall subere layer microcapsules prepared in Examples 1-4; Figure 14 TGA curves of cork tissue raw materials, plant cell wall cork layer microcapsules prepared in Examples 1 and 3-4, and cork layer prepared in Comparative Example 1; Figure 15 Contact angle test diagrams of plant cell wall suberein layer microcapsules prepared in Examples 1-4 Figure 16 SEM image of the product obtained in Comparative Example 4. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] In existing technologies, chemical depolymerization and solvent extraction methods are used to obtain suberin from cork tissue. However, the products obtained are small suberin molecules or their soluble molecular chain segments, not the complete suberin skeleton. Suberin, as a biomacromolecule polyester in plant cell walls, is a complex three-dimensional polyester structure formed by the cross-linking of long-chain fatty acids and aromatic structural components through a glycerol structure. It has complex covalent / non-covalent cross-links with lignin and polysaccharides in the cell wall. Therefore, the key technical challenge in preparing complete suberin layer microcapsules is how to accurately remove interfering components such as lignin, cellulose, and hemicellulose without destroying the natural three-dimensional structure of suberin.

[0036] In the prior art, CN119662516A discloses a separation reagent prepared by compounding hydrogen peroxide solution and sodium hypochlorite solution, which is used to obtain cork cells by placing cork particles in the separation reagent. It utilizes the reaction of hydrogen peroxide and sodium hypochlorite to form single linear oxygen with significant oxidizing activity, which is used to decompose small amounts of lignin in the middle layer and outer wall, while simultaneously releasing a large number of bubbles, promoting cell separation. However, this patent explicitly states that the separation reagent composed of hydrogen peroxide and sodium hypochlorite can only rapidly oxidize the pectin in the middle layer and a small amount of lignin in the outer wall of cork cells within a short time, and it is difficult to penetrate into the hydrophobic cork resin / wax network structure. Therefore, the above-mentioned separation reagent can only remove a small amount of lignin in the middle layer and outer wall; the lignin and polysaccharides in the outer and inner walls remain connected to the cork material through chemical cross-linking, and a pure cork skeleton cannot be obtained.

[0037] To ensure the continued action of the separation reagent on the cork cells to further remove lignin and polysaccharides from the outer and inner cell walls, the reaction can only proceed by replenishing the separation reagent. However, due to the excessively strong oxidizing power of the reactive oxygen species generated by the separation reagent, as the reaction progresses, while removing non-cork components from the surface of the separated cells, it also damages the microcapsule structure and molecular chain components of the cork layer itself, leading to the fragmentation of the microcapsule structure and the formation of numerous new micropores on the surface.

[0038] Therefore, when using a separation solution composed of hydrogen peroxide and sodium hypochlorite for treatment, the oxidation pathway of the reactive oxygen species produced by the reaction is non-selective. The reactive oxygen species oxidize and degrade lignin "non-selectively" from the intercellular layer to the cell wall layer, while also partially degrading other components. To achieve complete removal of lignin / polysaccharides, the reaction time must be extended, which will lead to the degradation of the suberin skeleton; if the reaction time is controlled to avoid damage, significant lignin / polysaccharide residues will remain. Therefore, the separation reagent composed of hydrogen peroxide and sodium hypochlorite cannot achieve the pure suberin layer microcapsules created in this invention through precise component tailoring.

[0039] Furthermore, prolonged treatment with strong oxidizing agents can damage the microcapsule structure and molecular chain components of the cork layer itself. To preserve the microcapsule structure of the cork layer, the inventors also attempted to treat the cork tissue raw material using weaker oxidizing agents such as hydrogen peroxide or sodium hypochlorite alone. However, these agents lacked sufficient oxidizing power for polysaccharides, making it difficult to completely remove them, and the resulting cork layer still contained a large amount of non-cork components.

[0040] Based on this, the present invention provides plant cell wall suberin layer microcapsules and their preparation method. Specifically, the plant suberin tissue is pretreated, then added to a dissociation reagent, and physical enhancement methods are used to facilitate the reaction as needed. After the reaction, the microcapsules are purified to obtain the plant cell wall suberin layer microcapsules. This invention achieves precise molecular dissociation from suberin tissue, selectively removing interfering components (lignin, cellulose, hemicellulose, etc.) while completely preserving the hollow, cystic morphology of the suberin layer.

[0041] The dissociation reagent is an acidic or alkaline dissociation solution. The acidic dissociation solution consists of an acidic medium and an oxidizing agent; the alkaline dissociation solution consists of an alkaline medium and an oxidizing agent, wherein the oxidizing agent is one or more of hydrogen peroxide, sodium hypochlorite, and sodium chlorite. Both the acidic and alkaline dissociation solutions may also include a decomposing agent, which is a eutectic solvent or a cell wall degrading enzyme specifically designed to degrade cell wall polysaccharides and / or lignin.

[0042] In this process, the oxidant attacks the aromatic side-chain ether bonds, ester bonds, and unsaturated double bonds in the lignin molecule, thereby breaking the bonds connecting lignin and suberin. This selectively removes lignin / polysaccharides from the middle lamella and cell wall surface while preserving the suberin layer framework. This treatment causes cells to naturally disperse, forming hollow suberin layer microcapsules. Acidic / alkaline media not only assist in the degradation of polysaccharides but also precisely help the oxidant regulate the surface properties of the suberin without damaging its integrity. Additionally, the decomposing agent can be used to decompose and dissolve non-suberin components such as lignin and polysaccharides on the cell wall surface, depending on the situation. Therefore, the dissociation reagent of this invention can effectively remove lignin and polysaccharides without damaging the structure of the suberin layer.

[0043] The plant cell wall suberin layer microcapsules prepared by the method of the present invention have a sac-like structure with a continuous wall and a hollow cavity, and the sac wall thickness is 100-2000 nm, thus preserving the original microscopic transport structure of the plant cell wall.

[0044] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0045] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels. Experimental methods without specified detailed conditions were performed according to conventional testing methods or the supplier's recommended operating instructions. Wherein: The common cellulase and alkaline cellulase used in the embodiments of the present invention were purchased from Shanghai Yanhui Biotechnology and Guangzhou Longli Biotechnology Co., Ltd., respectively.

[0046] Example 1: (1) Select the bark of the cork oak tree, remove the outer periderm and phloem, retain the cork layer, crush it to 40-60 mesh, and ultrasonically wash the crushed particles twice with distilled water for 5 minutes each time to remove surface dust and soluble impurities. Finally, dry it at 60℃ to obtain cork tissue raw material. (2) Prepare an acidic dissociation solution by blending: it contains acetic acid with a final concentration of 1 mol / L, hydrogen peroxide with a final concentration of 5 mol / L, and the amount of ordinary cellulase is 2.5 FPU / g cork tissue raw material; Using acidic dissociation solution as the dissociation reagent, 30g of cork tissue raw material was added to 800mL of dissociation reagent and stirred at 50℃ for 10h. After the reaction was completed, the reaction solution was collected and centrifuged. The precipitate was collected and gently ground. The precipitate was washed 5 times with deionized water and then freeze-dried to obtain plant cell wall cork layer microcapsules.

[0047] The SEM image of the plant cell wall cork layer microcapsules prepared in this embodiment is shown below. Figures 1-2 As shown, optical photographs Figure 3 As shown, the optical microscope image is as follows. Figure 4 As shown.

[0048] Depend on Figure 1 and Figure 2 It can be seen that the microcapsules of the plant cell wall subereum have a hollow sac-like structure, preserving the continuous and dense wall structure of the subereum and the hollow microcapsule morphology within the cavity. The sac wall thickness is 300-600 nm, and a small number of microporous transport structures exist on the sac wall.

[0049] Depend on Figure 3 As can be seen, the obtained plant cell wall suberen microcapsules are milky white. Because lignin contains chromophores such as conjugated carbonyl groups and phenolic hydroxyl groups, lignin-rich plant tissues are usually brown or brownish-yellow, and the darker the color, the higher the lignin content. The milky white color of the plant cell wall suberen microcapsules obtained in this example proves that they contain virtually no lignin.

[0050] Depend on Figure 4 It can be seen that the prepared plant cell wall subere layer microcapsules have a hollow cavity structure and good dispersibility in organic solutions (acetone).

[0051] Example 2: (1) Select potato peels, wash and filter them to remove surface dust and soluble impurities, and then dry them at 60°C to obtain cork tissue raw materials; (2) Acidic dissociation solution is prepared by blending: including sodium hypochlorite, a eutectic solvent made by choline chloride and formic acid in a molar ratio of 1:3, wherein the final concentration of sodium hypochlorite is 1 mol / L and the final concentration of formic acid is 1 mol / L. Using acidic dissociation solution as the dissociation reagent, 30g of cork tissue raw material was added to 600mL of dissociation reagent and stirred at 35℃ for 12h. After the reaction was completed, the reaction solution was collected and centrifuged. The precipitate was collected and subjected to sonication. The precipitate was washed 5 times with deionized water and then freeze-dried to obtain plant cell wall cork layer microcapsules.

[0052] The optical microscope image of the plant cell wall cork layer microcapsules prepared in this embodiment is shown below. Figure 5 As shown. By Figure 5 It can be seen that it has a hollow structure and good dispersibility in solution.

[0053] Example 3: (1) Select birch bark, remove the outer periderm and phloem, retain the cork layer, crush it to 20-80 mesh, and ultrasonically clean the crushed particles twice with distilled water for 1 minute each time to remove surface dust and soluble impurities. Finally, dry it at 60℃ to obtain cork tissue raw material. (2) Prepare an alkaline dissociation solution by blending: including potassium hydroxide, hydrogen peroxide, and a eutectic solvent made by choline chloride and urea in a molar ratio of 1:2; wherein the final concentration of potassium hydroxide is 1 mmol / L, the final concentration of hydrogen peroxide is 1.5 mol / L, and the final concentration of urea is 1 mol / L. Using alkaline dissociation solution as the dissociation reagent, 30g of cork tissue was added to 1000mL of the dissociation reagent and stirred at 45℃ for 8h. After the reaction was completed, the reaction solution was collected and centrifuged. The precipitate was collected, washed 5 times with deionized water, and then freeze-dried to obtain plant cell wall cork layer microcapsules.

[0054] The optical microscope image of the plant cell wall cork layer microcapsules prepared in this embodiment is shown below. Figure 6 As shown. By Figure 6 It can be seen that it has a strip-shaped hollow structure and good dispersibility in solution.

[0055] Example 4: (1) Select Eucommia bark, remove the outer periderm and phloem, retain the cork layer, crush it to 20-60 mesh, and ultrasonically clean the crushed particles twice with distilled water for 10 minutes each time to remove surface dust and soluble impurities. Finally, dry it at 60℃ to obtain cork tissue raw material. (2) Preparation of alkaline dissociation solution: including sodium hydroxide, sodium hypochlorite and alkaline cellulase, wherein the final concentration of sodium hydroxide is 2 mmol / L, the final concentration of sodium hypochlorite is 1.5 mol / L, and the amount of alkaline cellulase is 3.5 FPU / g cork tissue raw material; Using alkaline dissociation solution as the dissociation reagent, 30g of cork tissue raw material was added to 800mL of dissociation reagent and stirred at 35℃ for 4.5h. After the reaction was completed, the reaction solution was collected and centrifuged. The precipitate was collected, washed 5 times with deionized water, and then freeze-dried to obtain plant cell wall cork layer microcapsules.

[0056] The optical microscope image of the plant cell wall cork layer microcapsules prepared in this embodiment is shown below. Figure 7 As shown. By Figure 7 It can be seen that it has a hollow structure and good dispersibility in solution.

[0057] Comparative Example 1: The difference between this comparative example and Example 1 is that the existing alkali-alcohol depolymerization method is used to prepare cork. The specific steps are as follows: Cork tissue raw material was prepared according to the method in Example 1. It was placed in a 2% KOH / methanol solution and heated under reflux for 1.5 hours. After the reaction was complete, the cork tissue completely disintegrated, and a brown oily product was obtained by rotary evaporation. Figure 8 As shown.

[0058] Analysis revealed it to be a mixture of cork monomers and oligomers, completely losing its original macroscopic morphology.

[0059] Comparative Example 2: The difference between this comparative example and Example 1 is that the cork extract is prepared using a conventional solvent extraction method. The specific steps are as follows: Cork tissue raw material was prepared according to the method in Example 1. Soxhlet extraction was used, with a mixture of chloroform and methanol in a 2:1 ratio as the solvent. The cork tissue raw material was extracted for 10 hours, and the resulting product was a soluble solid. Figure 9 As shown.

[0060] The optical microscope image of the cork material prepared in this comparative example is shown below. Figure 10 As shown. By Figure 10 It can be seen that the cork obtained by solvent extraction cannot maintain the complete capsule structure morphology.

[0061] Comparative Example 3: The method for preparing bark cork cells according to patent CN119662516A includes the following specific steps: (1) Add the impurity-removed cork particles to the separation reagent and separate them at 60℃ for 1 hour (replace the separation reagent every 30 minutes during the process) to obtain separated cork cells; The separation reagent consists of a 3% sodium hypochlorite solution and a 3% hydrogen peroxide solution in a mass ratio of 10:1, except that the ratio of the amount of cork particles added to the separation reagent is 1g:55mL. (2) After washing the isolated cork cells with water, they were ultrasonically dispersed at a frequency of 40 kHz, a power of 720 W, and a duration of 5 min. The ultrasonically dispersed cork cells were freeze-dried for 48 h to obtain cork cell aggregates. The cork cell aggregates were then dispersed with anhydrous ethanol at a concentration of 5% of the cork cell aggregate mass, with continuous stirring. After the reagent evaporated, intact single hollow cork cells with a brownish-yellow color were obtained. Figure 11 As shown.

[0062] Comparative Example 4: The difference between this comparative example and Example 1 is that a separation reagent is used instead of a dissociation reagent. The separation reagent is prepared by mixing a 3% sodium hypochlorite solution and a 3% hydrogen peroxide solution in a 10:1 mass ratio. The specific steps are as follows: Cork tissue raw material was prepared according to the method in Example 1. 30g of cork tissue raw material was added to 800mL of separation reagent and stirred at 50℃ for 10h. After the reaction was completed, the reaction solution was collected and centrifuged. The precipitate was collected and gently ground. The precipitate was washed 5 times with deionized water and then freeze-dried to collect the product.

[0063] The product obtained in this comparative example was analyzed by SEM, and the results are as follows: Figure 16 As shown. By Figure 16 It can be seen that by using a separation reagent instead of the dissociation reagent in this application, the microcapsule structure of the prepared cork layer is broken, and a large number of new micropores are generated on the surface.

[0064] Experimental Example 1: Structural Characterization 1. FTIR analysis: FTIR analysis was performed on the cork tissue raw material obtained in step (1) of Example 1, the plant cell wall cork layer microcapsules obtained in Examples 1-4, the cork obtained in Comparative Example 1, and the cork cells obtained in Comparative Example 3. The results are as follows: Figure 12 As shown.

[0065] Depend on Figure 12 It can be seen that, compared with cork tissue raw materials, the plant cell wall cork layer microcapsules prepared in Examples 1-4 have a higher content of 2920 cm⁻¹. -1 (CH stretching vibration) and 1730cm -1 A distinct absorption peak exists at the (ester group C=O stretching vibration) position, at 1730 cm⁻¹. -1 The ester group peak at 1600 cm⁻¹ is a characteristic signal of suberin polyester, and its retention proves that the dissociation process of this invention did not destroy the ester bond structure of the suberin layer, demonstrating that the suberin layer of the microcapsule structure was not damaged. In the suberin raw material, the peak located at 1600 cm⁻¹... -1 1510 cm -1 The nearby lignin aromatic ring skeleton vibration absorption peak, and the peak located at 1050 cm⁻¹ -1 The CO stretching vibration absorption peaks of nearby cellulose / hemicellulose were significantly reduced in the spectra of Examples 1-4. This indicates that the lignin and polysaccharide components have been effectively removed. Combined with chemical composition analysis (lignin content <5%, polysaccharide content <5%), this confirms that the method of the present invention achieves selective removal of interfering components.

[0066] The product of Comparative Example 1 (alkali-alcohol depolymerization method) was at 1730 cm⁻¹ -1 The intensity of the ester group peak at 1705 cm⁻¹ decreased significantly, and at 1705 cm⁻¹... -1The increased peak intensity of the carboxylic acid group indicates that the suberin polyester has been fully depolymerized into monomers or oligomers; the product of Comparative Example 3 (separation method - suberin cells) still shows obvious lignin and polysaccharide characteristic peaks, proving that it is still a suberin cell containing whole cell wall components, rather than a pure suberin layer.

[0067] 2. XRD Analysis XRD analysis was performed on the plant cell wall suberein layer microcapsules prepared in Examples 1-4, and the results are as follows: Figure 13 As shown.

[0068] Depend on Figure 13 As can be seen, the XRD spectra of Examples 1 and 2 both exhibit a broad, diffuse diffraction peak near 2θ≈21°, which is a typical characteristic of the coexistence of crystalline and amorphous phases in polymer materials. Specifically, the peaks in Examples 1 and 2 are relatively sharp near 21°, with calculated crystallinity of 19.3% and 18.7%, respectively, indicating a certain degree of regularity in their molecular chain arrangement. In contrast, the spectra of Examples 3 and 4 show a more diffuse, broad peak, with calculated crystallinity of only 11.1% and 4.6%, respectively, indicating that they are predominantly amorphous.

[0069] 3. TGA Analysis: TGA analysis was performed on the cork tissue raw material obtained in step (1) of Example 1, the plant cell wall cork layer microcapsules obtained in Examples 1-4, and the cork layer obtained in Comparative Example 1. The results are as follows: Figure 14 As shown.

[0070] Depend on Figure 14 It can be seen that the plant cell wall suberin layer microcapsules prepared in Examples 1-4 begin to decompose at 250℃, reach the maximum weight loss rate at 420℃, and have a char residue rate of 8-10% at 550℃. Their thermal decomposition behavior is basically consistent with that of the suberin raw material, but slightly higher than that of the alkali depolymerization product of Comparative Example 1, indicating that the suberin layer microcapsules prepared in this invention completely retain the intrinsic thermal stability of suberin polyester. The alkali depolymerization product of Comparative Example 1 exhibits significantly reduced thermal stability due to the breakdown of polyester into smaller molecules.

[0071] 4. Hydrophobicity / Hydrophilicity Analysis: The hydrophobicity / hydrophilicity of the plant cell wall subere layer microcapsules prepared in Examples 1-4 was analyzed, and the results are as follows: Figure 15 As shown.

[0072] Depend on Figure 15As can be seen, the plant cell wall suberin microcapsules prepared in Example 1 have a contact angle of 90-110°, exhibiting hydrophobicity; the plant cell wall suberin microcapsules prepared in Example 2 have a contact angle of 70-95°, exhibiting moderate hydrophobicity; the plant cell wall suberin microcapsules prepared in Example 3 have a contact angle of 45-70°, exhibiting a hydrophilic-hydrophobic balance; and the plant cell wall suberin microcapsules prepared in Example 4 have a contact angle of 20-55°, exhibiting hydrophilicity. This demonstrates that by selecting different dissociation reagent systems, the surface chemical properties of suberin microcapsules can be effectively controlled, achieving a wide adjustable range (20°-110°) from hydrophilic to hydrophobic. The mechanism lies in the fact that dissociation reagents at different pH conditions affect the degree of hydrolysis of ester bonds and the exposure of polar functional groups such as hydroxyl groups on the suberin surface, thereby altering its surface energy. Therefore, the plant cell wall suberin layer microcapsules prepared by the present invention using different dissociation reagents have adjustable hydrophilicity / hydrophobicity.

[0073] Experimental Example 2: The components of plant cell wall suberin layer microcapsules prepared in Examples 1-4, suberin prepared in Comparative Examples 1-2, and suberin cells prepared in Comparative Example 3 were analyzed, and the results are shown in Table 1. Details are as follows: Suberin content: This is determined using the "depolymerization-determination method." Specifically, the sample is depolymerized using methods such as alkaline alcohol depolymerization to release suberin monomers (such as long-chain fatty acids and fatty alcohols). The monomers are then weighed (using an electronic scale) and their composition is determined (using GC-MS) to identify them as suberin components. Finally, the masses of all monomers are summed, and the percentage of suberin mass in the total composition is calculated, which is the suberin content.

[0074] Lignin content: The lignin content was determined using the "Klason lignin (acid-insoluble lignin) determination method," which is the standard method for determining the lignin content of lignocellulosic raw materials. The principle involves treating the sample with 72% concentrated sulfuric acid to hydrolyze polysaccharides (cellulose, hemicellulose) into soluble monosaccharides; the remaining insoluble residue is Klason lignin. Simultaneously, the acid-soluble lignin in the acid hydrolysate is determined using ultraviolet-visible spectrophotometry. The sum of these two methods represents the total lignin content.

[0075] Polysaccharide content: Determined using a two-step acid hydrolysis method followed by high-performance anion exchange chromatography (HPAEC) or high-performance liquid chromatography (HPLC). First, the residue after removing the suberin is hydrolyzed with 72% sulfuric acid. Then, a second step of high-temperature hydrolysis is performed by diluting the acid concentration to completely hydrolyze cellulose and hemicellulose into monosaccharides. Finally, HPAEC or HPLC is used to qualitatively and quantitatively identify the various monosaccharides (such as glucose, xylose, arabinose, etc.) in the hydrolysate, and the total polysaccharide content is calculated based on the monosaccharide content.

[0076] Table 1. Suberin content, lignin content, and polysaccharide content of different treatments As shown in Table 1, the lignin and polysaccharide contents in the plant cell wall suberein microcapsules prepared by this invention are both less than 1.5%, and the cork resin content is greater than 96.8%. Combined with FTIR analysis, it can be seen that the lignin and polysaccharide components have been effectively removed, thus proving that the method of this invention achieves selective stripping of interfering components.

[0077] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing plant cell wall suberein layer microcapsules, characterized in that, Includes the following steps: (1) After pretreatment of plant cork tissue, cork tissue raw material is obtained; (2) The cork tissue raw material was added to the dissociation reagent for reaction. After the reaction was completed, the precipitate was centrifuged and collected. After washing and drying, plant cell wall cork layer microcapsules were obtained. The dissociation reagent is either an acidic or a basic dissociation solution; the acidic dissociation solution consists of an acidic medium and an oxidizing agent; the basic dissociation solution consists of a basic medium and an oxidizing agent. The oxidizing agent is one or more of sodium hypochlorite, hydrogen peroxide, and sodium chlorite.

2. The method for preparing plant cell wall subere layer microcapsules as described in claim 1, characterized in that, Both the acidic and alkaline dissociation solutions may further include a decomposing agent, depending on the circumstances; wherein the decomposing agent is a eutectic solvent and / or a cell wall degrading enzyme; The eutectic solvent is prepared by mixing hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:(2-4); the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is an organic acid or urea. Cell wall degrading enzymes refer to enzymes used to degrade cell wall polysaccharides and / or lignin; preferably, the cell wall degrading enzyme is one or more of cellulase, hemicellulase, pectinase, and laccase.

3. The method for preparing plant cell wall suberen layer microcapsules as described in claim 1, characterized in that, The acidic medium is an organic acid or an inorganic acid, and the alkaline medium is an organic base or an inorganic base; preferably, the alkaline medium is sodium hydroxide or potassium hydroxide; the acidic medium is one or more of oxalic acid, lactic acid, citric acid, formic acid, and acetic acid.

4. The method for preparing plant cell wall suberen layer microcapsules as described in claim 1, characterized in that, In the acidic dissociation solution, the final concentration of the acidic medium is 1-10 mol / L and the final concentration of the oxidant is 1-10 mol / L; in the alkaline dissociation solution, the final concentration of the alkaline medium is 0.01-5 mmol / L and the final concentration of the oxidant is 1-10 mol / L.

5. The method for preparing plant cell wall suberen layer microcapsules as described in claim 2, characterized in that, In acidic dissociation solutions, when the decomposing agent is a cell wall degrading enzyme, its addition amount is 0.5-5 FPU / g cork tissue raw material; when the decomposing agent is a eutectic solvent, its final concentration is 0.5-1.5 mol / L. In the alkaline dissociation solution, when the decomposing agent is a cell wall degrading enzyme, the amount added is 2-5 FPU / g cork tissue raw material; when the decomposing agent is a eutectic solvent, the final concentration is 0.5-2.5 mol / L.

6. The method for preparing plant cell wall subere layer microcapsules as described in claim 1, characterized in that, In step (1), the plant cork tissue is the bark of a woody plant rich in cork cells or the periderm of a herbaceous plant; preferably, the woody plants rich in cork cells are selected from cork oak, eucommia, birch, cork oak, and phellodendron; the herbaceous plants are selected from potatoes.

7. The method for preparing plant cell wall subere layer microcapsules as described in claim 1, characterized in that, In step (1), the specific operation of pretreatment is as follows: after crushing the plant cork tissue to a particle size of 20-100 mesh, wash it 1-2 times, each time for 1-10 minutes, and then dry it at 50-70℃ to obtain cork tissue raw material.

8. The method for preparing plant cell wall suberein layer microcapsules as described in claim 1, characterized in that, In step (2), the ratio of cork tissue raw material to dissociation reagent is 30g:(600-1000)mL; the reaction temperature is 20-80℃ and the reaction time is 1.5-70h; During the reaction process, physical enhancement methods may be used as needed; the physical enhancement methods include one or more combinations of ultrasonic treatment, microwave treatment, stirring, and grinding.

9. The plant cell wall suberin layer microcapsules prepared by the preparation method according to any one of claims 1-8, characterized in that, The plant cell wall suberein layer microcapsules have a continuous wall and a hollow cavity, retaining the original microscopic transport structure of the plant cell wall; the wall thickness of the continuous wall and hollow cavity microcapsule structure is 100-2000 nm.

10. The plant cell wall suberen microcapsules as described in claim 9, characterized in that, The instantaneous surface water contact angle of plant cell wall subere layer microcapsules ranges from 20° to 110°.

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