A method for preparing lignin microspheres with controllable size and good biological activity

Abstract

The present invention discloses a method for preparing lignin microspheres with controllable size and good biological activity, and belongs to the field of efficient separation of wood fiber raw materials and environmentally friendly natural polymer materials. The present invention uses wood fiber raw materials as substrates, prepares lignin microspheres, enhances lignin biological activity by esterification reaction, and realizes the preparation of controllable size of lignin microspheres by adjusting the reaction conditions of pre-treating lignin fiber raw materials by binary solid acid-organic solvent system. This method has simple process, short preparation cycle and high yield. The esterified high biological activity lignin microspheres prepared by the present invention using lignin are significantly improved compared with lignin prepared by traditional process, and have excellent synergistic ultraviolet shielding performance and antibacterial activity, and have broad application prospects in the fields of cosmetics, personal care products, biopharmaceuticals, polymer composite materials, etc.

Description

Technical Field

[0001] The invention belongs to the field of efficient separation of wood fiber raw materials and environmentally friendly natural polymer materials, and relates to a highly antioxidant, broad-spectrum antibacterial, and anti-ultraviolet lignin microsphere and a preparation method thereof. Background Art

[0002] With the development of my country's economy and society, people's requirements for quality of life are increasing day by day, and antioxidants play an increasingly important role in people's health maintenance. The intake of antioxidant functional substances, such as vitamins, butylated hydroxytoluene (BHT) or oryzanol, can slow down the aging of the body and maintain health. Studies have shown that the initial generation of human chronic diseases is that free radicals easily rob cell electrons after entering the human body, resulting in reduced cell resistance, the body is susceptible to infection by bacteria, and even the formation of carcinogens. Therefore, antioxidant free radical scavenging has always been a research hotspot at home and abroad.

[0003] As people's health awareness gradually increases, some commercial antioxidants, because their synthesis and separation methods involve the use of a large number of chemical agents, have led to increasing attention to natural antioxidants, hoping that they can gradually replace commercial antioxidants, which is of great significance for reducing costs and using antioxidants safely.

[0004] Lignin micro / nanospheres, as a natural polyphenol with a three-dimensional network structure, are a class of lignin polymers with rich biological activities: such as antioxidant, antibacterial, anti-ultraviolet, anti-cancer and antiviral, etc. As a natural product, its cytotoxicity is also low. It has broad application prospects in the fields of lignin-based materials, dispersants and drug carriers. However, most of the lignin is currently treated as industrial waste or fuel, and the utilization rate is low. When lignin itself is used as a natural antioxidant, its antioxidant and antibacterial activities are low, and the ultraviolet shielding efficiency is not high enough. At present, the research on the biological activity of lignin microspheres is still in its infancy, mainly because its preparation method is cumbersome and the yield is low. Most methods for separating lignin microspheres with high biological activity are either based on the modification of industrial lignin or the separation conditions are harsh, causing lignin to undergo degradation reactions or condensation reactions. Therefore, it is necessary to improve the comprehensive biological activity of lignin microspheres and reduce the difficulty and yield of lignin microspheres. This will significantly expand the application areas and depth of lignin, and will be of great significance in promoting the sustainable and high-value utilization of lignin fiber resources. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a method of directly preparing lignin micro / nanospheres using wood fiber raw materials to increase the antioxidant active groups of lignin. The prepared antioxidant nano lignin has excellent antioxidant, synergistic broad-spectrum antibacterial and UV shielding functions.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing lignin microspheres with controllable size and good biological activity, characterized in that: lignin microspheres are prepared using wood fiber raw materials as substrates, the biological activity of lignin is enhanced by esterification reaction, and the size-controllable preparation of lignin microspheres is achieved by adjusting the reaction conditions of pretreating the lignin fiber raw materials with a binary solid acid-organic solvent system.

[0008] Furthermore, the wood fiber raw material is selected from: agricultural and forestry wastes, for example: straw, rice husk, bagasse, sawdust and other wood fiber wastes.

[0009] Furthermore, the binary solid acids are maleic acid and citric acid, respectively, the mass ratio of the two acids is 0.5-1:1, the mass fraction of the total acid in the reaction system is 30-50wt.%; the organic solvent is ethanol-water solvent, wherein the mass fraction of ethanol is 10-30wt.%.

[0010] Furthermore, the two solid acids are mixed with an ethanol-water solution in proportion, heated to dissolve at 50-60° C., and stirred continuously until a clear and uniform binary solid acid-organic solvent system is formed, and then heated to the reaction temperature and kept warm.

[0011] Furthermore, the preparation of lignin microspheres with controllable size and good biological activity includes the following steps:

[0012] 1) maleic acid and citric acid are mixed with an ethanol-water solution in proportion, and heated to dissolve at 50-60° C. until a uniform and transparent binary solid acid-organic solvent system is formed;

[0013] 2) The wood fiber raw material is fully mixed with the binary solid acid-organic solvent system and reacted at 80-120°C. After the reaction is completed, the pretreatment liquid is separated from the water-insoluble solids by vacuum filtration using a Buchner funnel. At the same time, a large amount of water is added to wash the solids and dilute the reaction liquid. The total acid content in the reaction liquid is diluted to less than 10wt.%, and lignin can be precipitated. The reaction liquid is left to stand overnight.

[0014] 3) centrifuging the reaction solution after standing, washing the obtained lignin with water until the washing solution is neutral, and freeze-drying to obtain lignin microspheres;

[0015] 4) After centrifuging the lignin in step 3), the remaining solvent is subjected to rotary evaporation to remove water therein, and the solid acid is recovered and recycled.

[0016] Furthermore, the solid-liquid ratio of the wood fiber raw material to the binary solid acid-organic solvent system is 1:5-1:15.

[0017] Furthermore, the wood fiber raw material is mixed with the binary solid acid-organic solvent system and reacted at 60-120° C. for 10-60 minutes.

[0018] Furthermore, a large amount of water is used to wash the solids and dilute the reaction solution at the same time. The final amount of water added is 10-15 times of the composite acid-water solvent system, and the concentration of the reaction solution where lignin is precipitated is reduced to 5-10wt.%, so as to precipitate the lignin microspheres in the pretreatment reaction solution.

[0019] Furthermore, the lignin micro / nanospheres are obtained by preparing the morphology-controllable energy storage lignin micro / nanospheres.

[0020] Furthermore, the modified lignin microspheres are used in the fields of cosmetics, personal care products, biopharmaceuticals, coatings, and polymer composite materials.

[0021] Compared with the prior art, the advantages of this application are:

[0022] 1) In the separation process of the present invention, the lignin can be directly prepared into microspheres through a pretreatment reaction without further processing, and the steps are simple and easy to operate.

[0023] 2) The present application can control the size of lignin microspheres by controlling the reaction conditions for separating wood fiber raw materials (pretreatment liquid acid concentration and ratio, reaction time, stirring method and reaction temperature, etc.), and can also control the esterification degree of lignin and increase the antioxidant active groups in lignin.

[0024] 3) The pKa values ​​of maleic acid and citric acid used in this application are 1.9 and 3.1 (sulfuric acid pKa = -2.0), so the two solid acids have weak acidity. Maleic acid and citric acid are also food additives with almost no toxicity, which greatly improves safety.

[0025] 4) The present application utilizes a weaker acid to significantly reduce the degradation reaction of lignin when separating lignin, and the ethanol contained in the reaction solution can also prevent the condensation reaction of lignin. At the same time, maleic acid can also undergo esterification reaction with the γ-OH side chain of lignin (Ind.Crops Prod.2021, 159, 113017), thereby increasing the esterification degree of lignin and the biological activity of lignin.

[0026] 5) The recovery of lignin in the present application only requires diluting the pretreatment reaction solution with water and centrifuging it for recovery. Maleic acid and citric acid can be recycled by simple evaporation and concentration. Therefore, compared with conventional methods, the preparation method of the present application is simple, recyclable, and can realize industrial large-scale preparation of lignin microspheres with controllable size, which has good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : Lignin microsphere size distribution and lignin microsphere morphology, where (ac) is the lignin microsphere size distribution diagram, and (dg) is the lignin microsphere morphology analysis diagram;

[0028] Figure 2 : The scavenging ability of lignin to DPPH (a) and ABTS (b) free radicals;

[0029] Figure 3 : Killing curves of lignin against E.coil (a) and S.aureus (b);

[0030] Figure 4 : The anti-ultraviolet performance diagram of lignin, (a) is the ultraviolet transmittance diagram of lignin, and (b) is the ultraviolet shielding rate diagram of lignin. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0032] Example 1

[0033] 1) citric acid and maleic acid were mixed at a mass ratio of 0.5:1, 0.75:1 and 1:1, respectively, and a corresponding mass of 30% (volume ratio) ethanol-water solution was added to adjust the total acid concentration to 50wt.%, and heated at 50°C until a uniform, clear liquid was formed;

[0034] 2) Mix the cotton stalk powder with the binary solid acid-organic solvent system at a solid-liquid ratio of 1:10, and react at 80, 100 and 120°C for 40 minutes, respectively, to complete the pretreatment reaction. By adjusting the lignin separation conditions, the esterification degree of lignin and the particle size of the lignin microspheres are changed. After the pretreatment reaction is completed, use a Buchner funnel to separate the pretreatment reaction liquid and the solids, add 10-15 times the volume of ultrapure water solution to wash the solids and dilute the reaction liquid at the same time, dilute the reaction liquid to a total acid concentration of less than 5wt.%, precipitate the lignin microspheres, and freeze the reaction liquid for 6-8h;

[0035] 3) using a centrifuge to centrifuge the reaction solution after quiescence, to separate lignin from the reaction solution, to recover the lignin micro / nanospheres, to wash the lignin micro / nanospheres with clean water until the washing solution becomes neutral, to freeze-dry, to obtain purified lignin micro / nanospheres, and to analyze their chemical structure and physical properties;

[0036] 4) The prepared lignin was divided into M50T80t40, M50T100t40 and M50T120t40 reaction conditions named L-T50, L-T100 and L-T120 (MxxTyytzz, M is the mass fraction of the mixed acid, wt.%, T is the reaction temperature, °C, t is the reaction time, min). The antioxidant activities, antibacterial activities and anti-ultraviolet activities of the three are shown in Table 1;

[0037] 5) The diluted reaction solution is subjected to rotary evaporation at 60° C. to recover the solid acid for recycling.

[0038] from Figure 1 As can be seen from Table 1, the size of lignin can change with the change of reaction conditions. Figure 1 The size distribution diagram of ac is the size of lignin microspheres obtained under different composite acid ratios (0.5:1, 0.75:1 and 1:1) under M50T100t40. The morphology of lignin microspheres (Figure cf) is the lignin prepared under the reaction conditions of M50T80t40, M50T100t40 and M50T120t40, and the solid acid composite ratio is (1:1). Figure 1 From a and b, we can see that the size of lignin changes with the ratio of the two solid acids in the reaction system. As the content of citric acid in the solid acid increases, the size of lignin gradually decreases, indicating that the addition of citric acid can adjust the size range of lignin microspheres. And as the proportion of citric acid increases, the particle size distribution in lignin becomes closer and closer to its geometric size, indicating that the addition of citric acid can enhance the uniformity of the distribution of lignin particle size ( Figure 1 ac in d 50 The value is close to μg(q 0 )). As shown in Table 2, the size of lignin decreases with the improvement of the reaction system after solid acid treatment with a 1:1 mixed dibasic acid. When the strongest reaction conditions (M50T120t40) are reached, the size of the lignin microspheres decreases from 58nm (M50T80t40) to 15nm. It can also be seen from Figure cf that compared with the large size (more than 300nm) and irregular structure of MWL, the size of the solid acid dissolved lignin decreases with the reaction (Table 2, the size of the solid acid lignin gradually decreases), and the morphology is getting closer and closer to spherical. The shape of L-T80 is close to a cylinder, while the L-T120 lignin particles are close to a sphere. This shows that the binary solid acid-water solvent separation method can regulate the particle size of the lignin microspheres and the morphology of the lignin by separating the reaction conditions of the lignin. This advantage can make the binary solid acid-organic solvent separation method in industrial applications, by preparing the required size and morphology requirements of lignin, adjusting the reaction conditions, and effectively changing the morphology requirements of the required lignin.

[0039] Table 1 Comparison of biological activities of different lignins

[0040]

[0041] In the table, the antioxidant activity and antibacterial activity are expressed in terms of half inhibition concentration (mg / mL) and the maximum UV shielding rate of the lignin solution at a concentration of 0.1 mg / mL.

[0042] As shown in Table 1, the antioxidant activity and antibacterial activity of different lignins were compared according to the half-inhibition concentration, and the UV shielding ability of lignin was measured with a 0.1 mg / mL lignin solution. Comparing the scavenging ability of different lignins on DPPH and ABTS free radicals, it can be seen that L-T120 has the lowest half-inhibition concentration and KL has the highest half-inhibition concentration, indicating that L-T120 can effectively scavenge the two free radicals at a lower concentration, and with the increase in the intensity of the reaction, the antioxidant activity of solid acid lignin can be improved. Even the antioxidant activity of L-T80 lignin dissolved under weak conditions is better than that of commercial lignin (AL, KL, etc.) and experimental lignin (CEL, MWL), and its half-inhibition concentration for DPPH and ABTS is only 0.05 and 0.07 mg / mL, which is much lower than LS's 0.30 and 0.28 mg / mL. Similar to the trend of antioxidant activity, the antibacterial performance of solid acid-dissolved lignin is also the best (Table 1). L-T120 lignin only needs 1.2 mg / mL to reach the lowest half-inhibitory concentration for E.coil, and its half-inhibitory concentration for S.aureus is only 2.4 mg / mL, which is much lower than other types of lignin, especially for industrial lignin, which is only 1 / 10 of the antibacterial concentration of KL lignin. In the test of anti-ultraviolet activity, L-T120, L-T100 and L-T80 still have the best ultraviolet shielding rate, which can shield up to 92% of ultraviolet light, and the lowest shielding rate reaches 78%, which is better than other types of lignin. The excellent biological activity of solid acid dissolved lignin is mainly due to the change of its structure by solid acid during the dissolution process. As shown in Table 2, the phenolic hydroxyl and carboxyl groups of solid acid dissolved lignin are higher than MWL, while the molecular weight is significantly lower than MWL. These advantages make solid acid lignin have unparalleled advantages in biological activity over commercial lignin and experimental lignin.

[0043] Table 2 Comparison of physical and chemical structures of different lignins

[0044]

[0045] Example 2

[0046] The lignin microspheres were prepared under the above conditions and different biological activities were measured as follows:

[0047] Antioxidant activity test: The antioxidant activity of lignin microspheres dissolved under different reaction intensities was evaluated by measuring the free radical scavenging ability of DPPH and ABTS. DPPH was dissolved in ethanol to prepare a concentration of 9×10 -5 mol / L analytical solution. ABTS analytical solution was prepared by reacting 7mM ABTS diammonium salt aqueous solution with 2.45mM potassium persulfate aqueous solution and standing at room temperature in a dark environment for 15 hours. The lignin microspheres were dissolved to prepare solutions of different concentrations (0.5-2.0mg / mL), and then the dissolved samples were added to the DPPH and ABTS analytical solutions, respectively, and reacted for 30 minutes and 6 minutes, respectively. Finally, the absorbance of the residual DPPH and ABTS after the reaction was measured at 517nm and 734nm using an ultraviolet spectrophotometer, and the antioxidant rates of different lignins were calculated.

[0048] Lignin resistance to DPPH free radical rate = [1-Aj / Ac]*100%; (taking 2mL of 0.2mM DPPH as the working solution as an example, Ac is the absorbance at 517nm after 2mL of lignin-free solution is mixed with 2mL of DPPH solution for 30min; Aj is the absorbance at 517nm after 2mL of lignin solution is mixed with 2mL of DPPH solution for 30min. The calculation formula for resistance to ABTS free radical is consistent with that of DPPH, but the mixing reaction time of ABTS free radical and lignin is 6min, and the absorbance of the detected ABTS and lignin mixed solution and ABTS solution is at 734nm.

[0049] according to Figure 1 The results of the antioxidant activity test of solid acid dissolved lignin and commercial lignin are compared in Table 1; it can be seen that the antioxidant activity of lignin under different reaction intensities is different. As the reaction intensity increases, the antioxidant activity of lignin increases accordingly. Figure 1 It can be seen that the antioxidant activity of L-T120 lignin is the best (separated under the conditions of M50T120t40), followed by L-T100, and L-T80 is the worst. This shows that with the increase of lignin separation conditions, the phenolic hydroxyl content in lignin increases (Table 2), and the increase in reaction intensity also improves the esterification rate of lignin, increases the carboxyl content with antioxidant activity, and further increases the antioxidant performance of solid acid dissolved lignin. Compared with commonly used commercial lignin (alkali lignin, lignin sulfonate, etc.) and laboratory lignin (MWL), the lignin dissolved by solid acid has good antioxidant activity, and the separation method is mild, and the reaction reagents can be recycled, showing great commercial potential.

[0050] Antibacterial activity test: The obtained lignin samples were prepared into concentrations of 1.0 mg / mL and 10 mg / mL, and filter paper sheets (diameter 5 mm) were soaked in them. 200 μL of bacterial suspension (Staphylococcus aureus (S.Aureus) and Escherichia coli (E.Coil) were taken respectively, and the concentration of the two bacterial mixtures was 5.0×10 8 CFU / mL), and the mixture was spread on the agar plate of the culture medium. The culture dish was divided into sections, and the soaked filter paper was attached to the divided agar. The plate was cultured in a bacterial incubator at 37°C for 24 hours. After the time was up, the inhibition zone was observed and measured, and the inhibition rate of lignin was calculated.

[0051] Inhibition rate = (inhibition zone diameter of treatment group - inhibition zone diameter of blank group) / inhibition zone diameter of treatment group

[0052] A trend similar to the antioxidant performance can also be seen in the antibacterial performance of solid acid-dissolved lignin. L-T120 lignin has the lowest half-inhibitory concentration for killing E.coil and S.aureus, with a minimum of only 1.18 mg / mL. On the contrary, KL requires 10 times the concentration to reach the corresponding half-inhibitory rate. For S.aureus bacteria, the half-inhibitory concentration required for lignin is higher, but solid acid-dissolved lignin still has the lowest half-inhibitory concentration. For example, L-T80 has a half-inhibitory concentration of 4.12 mg / mL for S.aureus, but commercial lignins such as AL and KL need to reach a similar half-inhibitory rate of more than 12 mg / mL, which is nearly 3 times that of L-T80. Moreover, L-T80 is the category with the highest half-inhibitory concentration among the three solid acid-dissolved lignins. From the inhibition rate of lignin solution on two microorganisms at different concentrations in Table 2, it can be seen that the effect of lignin in killing bacteria is dose-dependent. With the increase of dosage, the inhibition rate of lignin increases, and the relationship on the antibacterial curve of lignin shows that the sterilization ability of lignin enters a plateau after 12 hours, and the inhibition rate increases slowly. Similar to the antioxidant property, at the same concentration (1 mg / mL), the antibacterial activity of L-T120 is better than that of L-T80. Its sterilization rate for E.coil exceeds 80% after 24 hours, and the inhibition rate for S.aureus reaches 75%, which is much higher than the inhibition rate of MWL. This shows that the change of lignin's physical and chemical structure (phenolic hydroxyl content and molecular weight) after separation by solid acid significantly enhances its antibacterial activity.

[0053] UV shielding performance test: Dissolve lignin in 0.1 mol / L NaOH solution to prepare a 0.1 mg / mL lignin solution. Use a UV spectrophotometer to measure the UV absorption peak of the sample in the UVB and UVA regions.

[0054] UV transmittance of lignin T UVThe calculation of (200-400nm) is shown below:

[0055]

[0056] Where: T α is the average UV transmittance corresponding to the UV wavelength range, %. The calculation of the UV shielding rate of lignin is shown in the following formula:

[0057] S UV =100-T UV

[0058] Where: S UV is the shielding rate of lignin.

[0059] From the comparison of the UV shielding rates of different types of lignin in Table 1, it can be seen that compared with MWL and CEL separated by traditional experimental methods, the UV shielding rates of solid acid dissolved lignin are higher than those of lignin samples separated by these two traditional methods. Similarly, the anti-ultraviolet activity of solid acid lignin is also higher than that of AL, LS, and KL prepared by industrial methods. Among them, the UV shielding rate of L-T80 under milder reaction conditions (M50T80t40) is close to 80%, while the highest lignin separated by industrial and traditional methods is only about 70% (such as KL). This shows that the lignin separated by binary solid acid has good anti-ultraviolet activity, and the binary solid acid separation method can significantly increase the anti-ultraviolet performance of lignin, especially it can increase the functional groups and chemical bonds in lignin that have significant gains in anti-ultraviolet (as shown in Table 2), such as phenolic hydroxyl, carboxyl, S / G value and HK α The increase of phenolic hydroxyl groups in lignin can make lignin have more functional groups that can convert UV light into energy, while the carboxyl group and HK α The bond can enhance the conjugation effect of lignin and enhance the shielding performance of lignin. The increase in the S / G value increases the content of S unit lignin in lignin. The anti-ultraviolet performance of S unit lignin is better than that of G unit lignin. Because it has one more methoxy group than G unit, the ionization ability of the phenolic hydroxyl group of S unit lignin is increased, which can effectively increase the speed of lignin forming quinone structure, increase the conjugation performance of lignin, and improve the ultraviolet shielding efficiency of lignin. Figure 4 By comparing the transmittance of lignin, it can be seen that the UV transmittance of solid acid dissolved lignin (200-400nm range) is lower than that of MWL, and the transmittance of the three lignins decreases with the increase of reaction height. L-T120 has the lowest transmittance in the range of 200-400nm, which is close to 0( Figure 4The enlarged image in the middle shows that the binary solid acid separation method can increase the UV resistance of lignin samples by controlling the reaction conditions, and can selectively regulate the structure and UV resistance of lignin. This advantage is suitable for its industrial application. By adjusting the reaction conditions to prepare the UV resistance required by the product, the use of chemicals and energy can be selectively increased or decreased, the accuracy of the product's initial energy input can be increased, waste can be reduced, and the separation process can be made greener and more environmentally friendly.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing lignin microspheres with controllable size and good biological activity, characterized in that: The following steps are involved: 1) mixing maleic acid and citric acid in a mass ratio of 0.5 to 1:1 with an ethanol-water solution in proportion, and heating and dissolving at 50 to 60° C. until a uniform and transparent binary solid acid-organic solvent system is formed; the mass fraction of the total acid in the binary solid acid-organic solvent system is 30 to 50 wt.%; the organic solvent system is an ethanol-water solution, and the mass fraction of ethanol is 10 to 30 wt.%; 2) the lignocellulosic raw material is fully mixed with the binary solid acid-organic solvent system, and reacted at 60-120° C. for 10-60 minutes. After the reaction, the pretreatment liquid is separated from the water-insoluble solids by vacuum filtration using a Buchner funnel, and a large amount of water is used to wash the solids and dilute the reaction liquid. The total acid content in the reaction liquid is diluted to less than 10wt.%, and lignin can be precipitated. The reaction liquid is allowed to stand for 6-8 hours; the solid-liquid ratio of the lignocellulosic raw material to the binary solid acid-organic solvent system is 1:5-1:15; 3) centrifuging the reaction solution after standing, washing the obtained lignin with water until the washing solution is neutral, and freeze-drying to obtain lignin microspheres; 4) After centrifuging the lignin in step 3), the remaining solvent is subjected to rotary evaporation to remove water therein, and the solid acid is recovered and recycled.

2. The method for preparing size-controlled lignin microspheres with good biological activity according to claim 1, characterized in that: The wood fiber raw material is selected from one or more of straw, rice husk, bagasse and sawdust.

3. The method for preparing size-controlled lignin microspheres with good biological activity according to claim 1, characterized in that: A large amount of water was used to wash the solids and dilute the reaction solution. The final amount of water added was 10 to 15 times that of the binary solid acid-organic solvent system, reducing the concentration of the reaction solution where lignin was precipitated to 5 to 10 wt.%.

4. The lignin microspheres obtained by the method for preparing lignin microspheres with controllable size and good biological activity according to any one of claims 1 to 3.

5. The use of lignin microspheres according to claim 4, characterized in that: Used in cosmetics.

6. The use of lignin microspheres according to claim 4, characterized in that: Used in personal care products, biopharmaceuticals and coatings.

7. The use of lignin microspheres according to claim 4, characterized in that: Application in polymer composites.

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