Bamboo source cross-linked CMC-K and cross-linked CMC-NH composite biocontrol bacteria microspheres, and preparation method and application thereof

Abstract

The application relates to the field of biocontrol agents, in particular to a bamboo-source cross-linked CMC-K and cross-linked CMC-NH composite biocontrol agent microsphere and a preparation method and application thereof, which comprises the following steps: base material preparation, loading liquid preparation, composite adsorption and shaping and drying, wherein the base material preparation comprises the following steps: after the bamboo-source cross-linked CMC-K and the bamboo-source cross-linked CMC-NH are mixed, the mixture is crushed to obtain composite base material particles; the loading liquid preparation comprises the following steps: a binder and a microbial activity protective agent are dissolved in deionized water, after uniform stirring, a biocontrol agent is added, and after sufficient dispersion, a uniform biocontrol agent loading liquid is obtained. By adopting the bamboo-source cross-linked CMC-K and the bamboo-source cross-linked CMC-NH as the composite base material, not only can the biocontrol agent be provided with firm attachment points, the biocontrol agent is protected, the survival rate of the biocontrol agent is improved, but also K + and NH + are released in the degradation process, nutrients are provided for plants, the three synchronizations of "carrier disintegration, nutrient slow release and agent release" are realized, and the effective period and disease prevention effect of the biocontrol agent are improved.

Description

Technical Field

[0001] This application relates to the field of biocontrol agents, and in particular to a bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, their preparation method, and applications. Background Technology

[0002] In current biological control of soil-borne agricultural diseases, biocontrol agents are commonly used. These agents not only reduce pesticide residues in the environment and minimize impacts on non-target organisms, but also effectively maintain the balance of the farmland ecosystem, ensuring sustainable agricultural development. However, the effectiveness of biocontrol agents is often limited by the survival rate and duration of action of the microbial strains in the soil.

[0003] Traditional biocontrol agents primarily use conventional inorganic mineral materials as carriers, such as bentonite and diatomaceous earth. The biocontrol agents are adsorbed onto the surface of these materials, allowing the biocontrol bacteria to attach through physical adsorption. However, these carriers lack effective protection for the biocontrol bacteria and the ability to simultaneously supply nutrients. When biocontrol bacteria are directly exposed to complex soil environments, they are easily inactivated by antagonistic bacteria, extreme temperatures and humidity, and agricultural antimicrobial agents, leading to unstable control effects. Summary of the Invention

[0004] Bamboo-derived cellulose cell walls consist of primary walls, secondary walls, and intercellular layers. The S2 layer of the secondary wall accounts for over 70% of the cell wall, where cellulose microfibrils are arranged parallel at a 30°–40° angle, forming a dense and rigid network framework that endows the cell wall with excellent mechanical strength. The cell wall contains numerous micropores (pore size <2 nm) and mesopores (2–50 nm). When bamboo fibers are alkalized and etherified to prepare CMC, the natural pore structure of the cell wall is completely preserved. In the subsequent cross-linking reaction, the hydroxyl groups on the fiber surface combine with the cross-linking agent, transforming the loose fibers into an interpenetrating three-dimensional cross-linked network. The pore size can also be precisely matched by controlling the degree of cross-linking. Compared to wood-derived fibers, bamboo-derived cross-linked CMC-K / CMC-NH exhibits significantly higher mechanical strength.

[0005] To improve the control effect of biocontrol agents, this application provides bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, their preparation method, and applications.

[0006] In the first aspect, this application provides a method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, which adopts the following technical solution: A method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres includes the following steps: Substrate preparation: Bamboo-derived crosslinked CMC-K and bamboo-derived crosslinked CMC-NH are mixed and then pulverized to 80-100 mesh to obtain composite substrate particles; Preparation of loading solution: Dissolve the binder and microbial activity protectant in deionized water, stir evenly, add biocontrol agent, and after thorough dispersion, obtain a uniform biocontrol agent loading solution; Composite adsorption: After mixing the composite substrate particles and the biocontrol bacteria loading liquid, the mixture is allowed to stand at room temperature for adsorption, resulting in a wet composite substrate loaded with biocontrol bacteria. Molding and drying: The wet composite substrate loaded with biocontrol bacteria is granulated and dried until the moisture content is ≤10% to obtain bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres.

[0007] By adopting the above technical solution, using bamboo-derived cross-linked CMC-K and bamboo-derived cross-linked CMC-NH as composite substrates, it not only possesses good biodegradability but also a rich three-dimensional network structure. During the composite adsorption process, it can provide strong attachment points for biocontrol bacteria, protecting them. Simultaneously, the addition of biocontrol bacteria activity protectants can form a protective layer on the surface of bacterial cells during drying, effectively preventing damage to cell membranes and proteins during dehydration, greatly improving the survival rate of biocontrol bacteria. Furthermore, cross-linked CMC-K can provide potassium, and cross-linked CMC-NH can provide nitrogen, enabling the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol bacteria microspheres to release potassium during degradation. + and NH + It can be absorbed by plants as nutrients, achieving the simultaneous release of "carrier disintegration, nutrient slow release, and bacterial agent release", thus obtaining high-performance bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres through the above preparation method.

[0008] This application utilizes bamboo-derived crosslinked CMC-K and bamboo-derived crosslinked CMC-NH as composite substrates, which not only provides a strong attachment point for biocontrol bacteria, protecting them and improving their survival rate, but also releases K during the degradation process. + and NH + It provides nutrients to plants, achieving simultaneous "carrier disintegration, nutrient slow release, and bacterial agent release," thereby improving the duration of action and disease control effect of biocontrol bacteria.

[0009] Preferably, the dry weight ratio of the bamboo-derived crosslinked CMC-K to the bamboo-derived crosslinked CMC-NH is (1.5-3):1.

[0010] By adopting the above technical solutions, when there is too much bamboo-derived cross-linked CMC-K, the higher degree of cross-linking and the more stable structure of the cross-linked CMC-K will lead to an overly rigid overall structure of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. This slows down the degradation rate in the soil and delays the release of biocontrol bacteria. Furthermore, the presence of excessive cross-linked CMC-K will result in an overly dense three-dimensional network, affecting the activity of the biocontrol bacteria. When there is too little bamboo-derived cross-linked CMC-K, the excessive addition of bamboo-derived cross-linked CMC-NH will make the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres more prone to swelling. This will reduce the compressive strength of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres and cause them to disintegrate too quickly in humid environments. The biocontrol bacteria will lack a long-term stable "sanctuary" and will be unable to achieve long-term control.

[0011] Preferably, the binder is at least one of maltodextrin, soluble starch, oligosaccharides, and low-viscosity cellulose ether.

[0012] By adopting the above technical solution, maltodextrin exhibits good viscosity and, after drying, forms a strong, transparent film that tightly binds the composite substrate particles, giving the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres ideal compressive strength. Furthermore, as a sugar derivative, maltodextrin can replace some water molecules during the drying process, forming hydrogen bonds with the phospholipids and proteins of the biocontrol bacteria cell membrane, thus acting as a "water replacement" agent, stabilizing the cell structure, and improving the survival rate of the biocontrol bacteria.

[0013] Soluble starch, after gelatinization, possesses excellent viscosity, enabling it to bind composite substrate particles. Its macromolecular chains also serve to fill and support the network structure. Furthermore, soluble starch can be slowly degraded by microorganisms in soil, providing an initial carbon source for biocontrol bacteria and beneficial soil bacteria, thus promoting the colonization of biocontrol bacteria.

[0014] While possessing viscosity, oligosaccharides can also form a special glassy protective layer on the surface of biocontrol bacteria cells, effectively preventing damage to cell membranes and proteins caused by adverse conditions such as dryness and high temperatures, thereby improving the survival rate of biocontrol bacteria.

[0015] Low-viscosity cellulose ethers can form strong, continuous films, providing excellent interparticle adhesion and overall strength of microspheres.

[0016] Preferably, the amount of the microbial activity protectant added accounts for 2-3% of the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate.

[0017] By adopting the above technical solution, when the amount of microbial activity protectant added is too small, it is impossible to form a complete protective layer for all biocontrol bacteria cells. During the drying process, a large number of cells die due to direct exposure to dehydration stress, resulting in the initial viable bacteria count in the bamboo-based cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres being far lower than expected. This directly weakens the application effect of the biocontrol agent. Furthermore, due to insufficient protection of the biocontrol bacteria, the resistance to temperature and humidity fluctuations during subsequent storage is also poor, resulting in a shortened shelf life.

[0018] When too much microbial activity protectant is added, the excessively high concentration of microbial activity protectant will significantly increase the viscosity and osmotic pressure of the loading liquid. The high viscosity liquid is difficult to uniformly wet and adsorb into the porous cross-linked CMC substrate particles, which can easily lead to uneven loading. Furthermore, the high osmotic pressure environment may cause some sensitive bacterial cells to undergo plasmolysis, which will damage them before drying and affect the activity of the biocontrol bacteria.

[0019] Preferably, the microbial activity protectant is at least one of mannitol, sorbitol, and xylitol.

[0020] By employing the above-mentioned technical solution, mannitol, containing six hydroxyl groups, can form strong hydrogen bonds with the polar heads of the phospholipid bilayer of biocontrol bacteria cell membranes and the amino and carboxyl groups of proteins. During the drying and dehydration process, mannitol can replace water molecules to occupy the hydrogen bond sites on the surface of bacterial cells, preventing the aggregation and fusion of cell membrane phospholipid molecules due to water loss, while also preventing protein denaturation and inactivation, thus reducing bacterial death at the source during drying. Furthermore, mannitol has a certain free radical scavenging ability, which can neutralize reactive oxygen species generated during the metabolism of biocontrol bacteria, reduce ROS oxidative damage to cell membrane lipids, and prolong the survival period of biocontrol bacteria in soil.

[0021] Sorbitol functions similarly to mannitol, binding to bacterial cell membranes and proteins via its hydroxyl groups to stabilize cell structure and resist adverse conditions such as dryness and high temperatures. Furthermore, sorbitol exhibits a mild osmotic pressure regulating effect, mitigating osmotic pressure fluctuations caused by binders and substrate components in the loading solution, preventing cell plasmolysis and decreased activity in sensitive biocontrol bacteria due to osmotic pressure mutations. Simultaneously, sorbitol releases a small amount of carbon source during degradation in soil, providing basic nutrients for biocontrol bacteria colonization and the reproduction of beneficial soil bacteria, indirectly extending the duration of biocontrol bacteria's effectiveness, and synergistically enhancing the release of potassium from cross-linked CMC-K / CMC-NH. + NH + This enhances the simultaneous effect of "nutrient slow release + bacterial agent release".

[0022] The hydroxyl group of xylitol has a more stable spatial structure, and the protective layer formed on the surface of the microbeads has good stress resistance. It can not only resist dehydration damage during the drying process, but also cope with temperature and humidity fluctuations during microbead storage, continuously encapsulate the microbeads, reduce the stimulation of the microbeads by the external environment, extend the shelf life of the microbeads, and solve the problem of "decay of microbead activity during storage".

[0023] Preferably, the biocontrol agent is a mixture of Trichoderma harzianum spores and Bacillus subtilis spores.

[0024] By adopting the above technical solution, the hyphae formed after the germination of Trichoderma harzianum spores can parasitize or entangle the hyphae of plant pathogens, secrete extracellular enzymes such as chitinase and glucanase to degrade the cell walls of pathogens, achieving direct antagonism. In addition, the hyphae can colonize the surface of plant roots, forming a "protective film" to occupy space sites, preventing pathogen infection, and can also induce the plant to produce a defense response, thereby enhancing the plant's own disease resistance.

[0025] Bacillus subtilis spores have extremely strong resistance to adverse conditions. They can quickly germinate into vegetative bodies in the soil. These vegetative bodies can secrete substances such as lipopeptide antibiotics and antibacterial proteins to inhibit the growth and reproduction of pathogens. They can also inhibit the colonization of pathogens through nutrient competition, while secreting plant growth regulators to promote plant growth.

[0026] Combining Trichoderma harzianum spores and Bacillus subtilis spores into a biocontrol agent enables comprehensive control of fungal and bacterial diseases, overcoming the narrow spectrum of single-agent disease prevention. Furthermore, Bacillus subtilis spores germinate rapidly, quickly occupying rhizosphere sites and consuming nutrients, creating a low-competition environment for Trichoderma harzianum spore germination. The entanglement characteristic of Trichoderma harzianum hyphae further strengthens the rhizosphere "protective barrier." Together, they form a microecological system of synergistic colonization by bacteria and fungi, resisting dual competition from indigenous microorganisms and pathogens, thus extending the duration of effectiveness. Moreover, Bacillus subtilis spores exhibit strong resistance, surviving stably under adverse conditions such as dryness and low temperatures. Their post-germination metabolic products act as "nutrient activators" for Trichoderma harzianum spore germination, promoting spore development. The hyphal network of Trichoderma harzianum can envelop the vegetative body of Bacillus subtilis, preventing predation by soil protozoa and increasing the bacterial survival rate in the soil.

[0027] Preferably, the solid-liquid mass ratio of the composite substrate particles and the biocontrol bacteria loading liquid is 1:(1.5-2.5).

[0028] By adopting the above technical solution, when the solid-liquid mass ratio is too high, the biocontrol bacteria loading liquid is insufficient and can only cover the surface of the composite substrate particles, unable to penetrate into the pores. This causes the biocontrol bacteria to only adhere to the surface of the substrate and easily become inactive due to direct contact with the external environment during the drying process. Furthermore, the binder cannot uniformly coat the composite substrate particles, resulting in a lack of sufficient bonding medium between the composite substrate particles. Consequently, the compressive strength of the bamboo-based crosslinked CMC-K and crosslinked CMC-NH composite biocontrol bacteria microspheres decreases. When the solid-liquid mass ratio is too low, excessive biocontrol bacteria loading liquid will cause the composite substrate particles to be in a highly moist state, which will easily lead to excessive adhesion during the granulation process, forming irregular large-size agglomerates. Due to the poor air permeability inside the agglomerates, the "dry outside and wet inside" phenomenon is likely to occur during the drying process. The internal biocontrol bacteria will become moldy and inactive due to lack of oxygen and water retention. Furthermore, excessive biocontrol bacteria loading liquid will destroy the three-dimensional network structure of cross-linked CMC-K / cross-linked CMC-NH, resulting in a decrease in the compressive strength of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol bacteria microspheres.

[0029] Preferably, kaolin is added in the substrate preparation step, and the amount of kaolin added accounts for 1-5% of the total amount of the bamboo-derived crosslinked CMC-K substrate and the bamboo-derived crosslinked CMC-NH substrate.

[0030] By adopting the above technical solution, the layered particles of kaolin have high hardness and rigidity, and can be used as a "rigid filler" to fill the three-dimensional network pores of the cross-linked CMC-K / CMC-NH composite substrate. This forms a "rigid support-flexible adhesion" composite structure with the binder, significantly improving the compressive strength of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. Simultaneously, the negatively charged surface of kaolin allows it to bind with negatively charged biocontrol bacteria cells through electrostatic adsorption, forming a "mineral protective layer" that enhances the biocontrol bacteria's resistance and protects their activity.

[0031] When the amount of kaolin added is too small, it cannot fully fill the three-dimensional network pores of the cross-linked CMC-K / CMC-NH composite substrate, and the improvement of the compressive strength of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres is not significant. When the amount of kaolin added is too large, the excess kaolin will block the three-dimensional network structure of the cross-linked CMC-K / CMC-NH composite substrate, making the structure of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres too dense. This makes it difficult for the biocontrol bacteria to come into contact with external moisture and nutrients, and the germination of Trichoderma harzianum spores and Bacillus subtilis spores is inhibited.

[0032] Secondly, this application provides a bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, which adopt the following technical solution: A bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microsphere is prepared by the above-mentioned preparation method of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microsphere.

[0033] Thirdly, the application of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres provided in this application adopts the following technical solution: Application of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres; application of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres in the prevention and control of soil-borne diseases in farmland.

[0034] In summary, this application includes at least one of the following beneficial technical effects: 1. This application uses bamboo-derived crosslinked CMC-K and bamboo-derived crosslinked CMC-NH as composite substrates, which not only provides a strong attachment point for biocontrol bacteria, protecting them and improving their survival rate, but also releases K during the degradation process. + and NH + It provides nutrients to plants, achieving simultaneous "carrier disintegration, nutrient slow release, and bacterial agent release", thereby improving the duration of action and disease control effect of biocontrol bacteria; 2. This application combines *Trichoderma harzianum* spores and *Bacillus subtilis* spores into a biocontrol agent, achieving comprehensive control of "fungal + bacterial" diseases. This solves the problem of narrow spectrum of single-agent disease prevention. Furthermore, *Bacillus subtilis* spores germinate rapidly, quickly occupying plant rhizosphere sites and consuming nutrients, creating a "low-competition" environment for *Trichoderma harzianum* spore germination. The entanglement characteristics of *Trichoderma harzianum* hyphae further strengthen the rhizosphere "protective barrier." Together, they form a "bacterial-fungal" synergistic colonization microecological system, resisting dual competition from indigenous microorganisms and pathogens, thus extending the effective period. Moreover, *Bacillus subtilis* spores exhibit strong resistance, surviving stably under adverse conditions such as dryness and low temperatures. Their post-germination metabolic products act as "nutrient activators" for *Trichoderma harzianum* spore germination, promoting spore development. The hyphal network of *Trichoderma harzianum* can encapsulate the vegetative body of *Bacillus subtilis*, preventing predation by soil protozoa and increasing the bacterial survival rate in the soil. 3. This application utilizes kaolin as a reinforcing phase, acting as a "rigid filler" to fill the three-dimensional network pores of the cross-linked CMC-K / CMC-NH composite substrate. This forms a "rigid support-flexible adhesion" composite structure with the binder, significantly improving the compressive strength of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. Simultaneously, the negatively charged surface of kaolin allows it to bind with the negatively charged biocontrol bacteria cells through electrostatic adsorption, forming a "mineral protective layer" that enhances the biocontrol bacteria's resistance and protects cell activity. Detailed Implementation

[0035] The raw materials in this application include the following: Bamboo-derived crosslinked CMC-Na: This application uses bamboo-derived crosslinked CMC-Na with a carboxymethyl substitution degree of 0.68; Maltodextrin: Uses commercially available products with CAS number 9050-36-6; Soluble starch: Commercially available product with CAS number 9005-84-9; Oligosaccharides: Chitosan, sodium alginate, etc. can be used. This application takes chitosan with CAS number 9012-76-4 as an example. Low viscosity cellulose ethers: This application takes low viscosity sodium carboxymethyl cellulose from Hubei Huada Fine Chemical Co., Ltd. as an example; Mannitol: Uses commercially available product with CAS number 69-65-8; Sorbitol: Uses a commercially available product with CAS number 50-70-4; Xylitol: Uses commercially available products with CAS number 87-99-0; Trichoderma harzianum: Trichoderma harzianum with accession number CGMCC No. 3.3711 and accession date of July 10, 2025 was used; Bacillus subtilis: Bacillus subtilis with accession number CGMCC No. 0806 and accession date of July 15, 2025 was used; Kaolin: Commercially available product with CAS number 1332-58-7; Traditional biocontrol wettable powder: Bacillus subtilis wettable powder from Hubei Jiufenglong Chemical Co., Ltd.

[0036] Preparation Example 1 The preparation method of bamboo-derived crosslinked CMC-K includes the following steps: Take 100g of bamboo-derived crosslinked CMC-Na, add 200mL of 6% dilute hydrochloric acid, stir at 150rpm for 40min at room temperature to remove sodium, then wash with water until pH 7.0, centrifuge and dry, add the desodium-removed product to 450mL of 0.5% potassium hydroxide aqueous solution, stir at 180rpm for 60min at 40℃ to carry out ion exchange, and dry with hot air after the reaction to obtain bamboo-derived crosslinked CMC-K powder.

[0037] Preparation Example 2 The preparation method of bamboo-derived crosslinked CMC-NH includes the following steps: Take 100g of bamboo-derived crosslinked CMC-Na, add 200mL of 6% dilute hydrochloric acid, stir at 150 rpm for 40min at room temperature to remove sodium, then wash with water until pH 7.0, centrifuge and dry, add the desodium product to 250mL of 8% ammonia water, stir at 180 rpm for 60min at 40℃ to ammonify, after the reaction, remove free ammonia by hot air blowing, quickly wash with water and vacuum dry at 40℃ until the moisture content is ≤8%, to obtain bamboo-derived crosslinked CMC-NH powder with a residual amino content of 0.52 mmol / g.

[0038] Preparation Example 3 The method for preparing Trichoderma harzianum spores includes the following steps: Trichoderma harzianum is inoculated onto a PDA solid culture medium plate, incubated upside down at 28°C for 7 days, and the activated strain is used to prepare a spore suspension with sterile water. The spore concentration is counted under a microscope, and the concentration of the Trichoderma harzianum spore suspension is adjusted to 1.0 × 10⁻⁶. 9 CFU / g.

[0039] Preparation Example 4 The method for preparing Bacillus subtilis spores includes the following steps: streaking Bacillus subtilis strain onto LB solid medium, incubating upside down at 37°C for 5 days, preparing a spore suspension with sterile water, counting the spore concentration under a microscope, and adjusting the concentration of the Bacillus subtilis spore suspension to 1.0 × 10⁻⁶. 10 CFU / g.

[0040] The present application will be further described in detail below with reference to embodiments and comparative examples. Example 1

[0041] A method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres includes the following steps: Substrate preparation: Bamboo-derived crosslinked CMC-K and bamboo-derived crosslinked CMC-NH were mixed at a dry weight ratio of 2:1 and then pulverized to 90 mesh to obtain 50g of composite substrate particles; Preparation of loading solution: Dissolve 18g of maltodextrin and 1.5g of mannitol in 80mL of deionized water, stir at 50℃ until completely dissolved, cool to room temperature, add 1.5g of biocontrol agent, and stir magnetically for 30min to obtain a homogeneous biocontrol loading solution. The biocontrol agent is a mixture of Trichoderma harzianum spores and Bacillus subtilis spores, with a mass ratio of Trichoderma harzianum spores to Bacillus subtilis spores of 2:1. Composite adsorption: The composite substrate particles and the biocontrol bacteria loading liquid were mixed at a solid-liquid mass ratio of 1:2 and allowed to stand at room temperature for 30 minutes to adsorb, thus obtaining a wet composite substrate loaded with biocontrol bacteria. Molding and drying: The wet composite substrate loaded with biocontrol bacteria is transferred to a granulator and granulated at 300 rpm to obtain wet microspheres with a particle size of 1-3 mm. The wet microspheres are then vacuum dried at 40°C until the moisture content is ≤10% to obtain bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol bacteria microspheres.

[0042] Comparative Example 1 Comparative Example 1 is based on the preparation method of Example 1, but removes the microbial activity protectant in the preparation process of the loading solution. That is, in the preparation process of the loading solution, the binder is dissolved in deionized water, stirred evenly, and then the biocontrol agent is added. After being fully dispersed, a uniform biocontrol loading solution is obtained, and the other conditions remain unchanged.

[0043] Comparative Example 2 Comparative Example 2 is a conventional biocontrol wettable powder with the same bacterial count as Example 1.

[0044] Performance testing The biocontrol agents of Example 1 and Comparative Examples 1-2 were analyzed using the following specific detection methods: 1. Nutrient release measurement Weigh 10g of the test soil and place it in an Erlenmeyer flask. Add 0.5g of bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres, and then add 100mL of deionized water. After sealing the Erlenmeyer flask, extract the soil by shaking at 25℃ and 150rpm for 24h to obtain a mixed solution. Centrifuge the supernatant, filter it to obtain the soil extract, plot the standard curves of potassium ions and amino nitrogen, and calculate the release of potassium ions and amino nitrogen.

[0045] 2. Disintegration rate and release amount 10g of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres were weighed and evenly buried in simulated soil. The microspheres were incubated at 25℃ for 15 days while maintaining the soil moisture content at 18%. Soil samples were taken and undisintegrated bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres were collected. The microspheres were rinsed with deionized water and then vacuum dried at 40℃. The mass was measured and the disintegration rate was calculated.

[0046] Soil samples were collected at different incubation times (1d, 3d, 5d, 7d, 15d), and 100mL of sterile physiological saline was added to each sample. The mixture was shaken for 30min to prepare a soil bacterial suspension. The soil bacterial suspension was diluted 10-3 times, and 0.1mL of the diluted solution was spread onto a culture medium. Trichoderma harzianum was cultured on PDA medium at 28℃ for 7 days, and Bacillus subtilis was cultured on LB medium at 37℃ for 5 days. The number of viable bacteria in the soil at each time point was calculated. The cumulative release rate after 15 days was calculated using the formula: Cumulative release rate after 15 days (%) = Total number of viable bacteria in the soil after 15 days / Initial total number of viable bacteria in the microspheres × 100%.

[0047] The method for detecting the initial total viable count in the microspheres is as follows: Weigh 1g of the prepared fresh bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres and place them in an Erlenmeyer flask containing 99mL of sterile physiological saline. Add 8 sterile glass beads and shake at 25℃ and 150rpm for 40min to obtain the initial bacterial suspension. Dilute the initial bacterial suspension to 10... -3 10 -4 10 -5 10 -6 Dilute the solution by 1:1 and spread 0.1 mL of the diluted solution onto PDA and LB agar plates. Incubate the PDA plates upside down at 28°C for 7 days and the LB plates upside down at 37°C for 5 days. Calculate the colony count on the plates. Single-strain viable cell concentration (CFU / g) = (average colony count × dilution factor) ÷ spread volume (0.1 mL) ÷ microsphere sample mass (1.0 g). Initial total viable cell count of microspheres (CFU / g) = Trichoderma harzianum viable cell concentration + Bacillus subtilis viable cell concentration.

[0048] 3. Survival rate Weigh 10g of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres and spread them evenly in a petri dish. Spray with diluted chlorothalonil solution until the surface of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres is moistened, and then place them in a ventilated place to dry. After spraying, bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres were placed in 50 mL of sterile physiological saline and shaken for 5 min to wash away the biocontrol bacteria on the surface of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, obtaining a surface bacterial suspension. The washed bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres were then cut open, and the core tissue was taken and placed in sterile physiological saline. After grinding, it was shaken for 30 min to obtain a core bacterial suspension. The surface bacterial suspension and the core bacterial suspension were diluted and spread on selective culture medium, and counted. The number of viable bacteria on the surface and in the core of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres that were not sprayed with chlorothalonil was used as a control to obtain the survival rate: survival rate (%) = number of viable bacteria after spraying / number of viable bacteria in the control × 100%.

[0049] 4. Disease prevention effect Tomato seeds were disinfected, soaked, and then sown in a sterilization system. After reaching the two-leaf-one-heart stage, uniformly growing tomato seedlings were selected, and their roots were immersed in a Fusarium oxysporum spore suspension for 30 minutes. After drying, the seedlings were divided into three groups of 30 seedlings each. The treatment methods for the three groups were as follows: Group 1: Each seedling was treated with 1g of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres mixed with the sterilized substrate before transplanting; Group 2: Each seedling was treated with an equal amount of traditional biocontrol wettable powder mixed with the substrate before transplanting; Group 3: No biocontrol agents were used during transplanting. All tomato seedlings were cultured in a greenhouse at 26℃ with 12h / d light, and watered regularly to maintain a substrate moisture content of 15-20%. After 30 days, the incidence of root rot was investigated in each treatment group.

[0050] Based on the above detection method, the test results of Example 1 and Comparative Examples 1-2 were obtained, as shown in Table 1 below.

[0051] Table 1 Performance test results for Example 1 and Comparative Examples 1-2

[0052] Referring to Table 1, it can be seen from the comparison between Example 1 and Comparative Example 1 that the addition of the microbial activity protectant can form a protective layer on the surface of the bacterial cells during the drying process, effectively preventing damage to the cell membrane and proteins during dehydration, and greatly improving the survival rate of the biocontrol bacteria.

[0053] Comparative Example 1 and Comparative Example 2 show that the bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres obtained in this application have a significantly better control effect on tomato root rot than traditional biocontrol wettable powders.

[0054] Examples 2-5 Examples 2-5 are based on the preparation method of Example 1, but the dry weight ratio of bamboo-derived crosslinked CMC-K to bamboo-derived crosslinked CMC-NH is adjusted as shown in Table 2.

[0055] Performance testing The bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres from Examples 1-5 were analyzed using the following specific detection methods: 1. Compressive strength Bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres with uniform particle size, good sphericity, and no cracks or damage were screened and placed in a desiccator for equilibration for 24 hours. Then, the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres were placed in a particle strength tester and pressure was applied to them. The maximum pressure value (N) when multiple groups of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres were broken was recorded and the average value was taken.

[0056] Based on the above detection method, the test results of Examples 1-5 were obtained, as shown in Table 2 below.

[0057] Table 2. Dry weight ratio and performance test results of bamboo-derived crosslinked CMC-K and bamboo-derived crosslinked CMC-NH in Examples 1-5.

[0058] Referring to Table 2, comparing Examples 1-5, it can be seen that when the dry weight ratio of bamboo-derived crosslinked CMC-K to bamboo-derived crosslinked CMC-NH is in the range of (1.5-3):1, especially when the dry weight ratio of bamboo-derived crosslinked CMC-K to bamboo-derived crosslinked CMC-NH is 2:1, the resulting composite biocontrol microspheres of bamboo-derived crosslinked CMC-K and crosslinked CMC-NH exhibit the best performance. This may be because when there is too much bamboo-derived crosslinked CMC-K, due to the higher degree of crosslinking and the more stable structure of crosslinked CMC-K, the composite biocontrol microspheres of bamboo-derived crosslinked CMC-K and crosslinked CMC-NH become too rigid, resulting in a slower degradation rate in the soil. The release of biocontrol bacteria is delayed due to the slowed temperature. Furthermore, the presence of excessive cross-linked CMC-K can lead to an overly dense three-dimensional network, affecting the activity of the biocontrol bacteria. When there is too little bamboo-derived cross-linked CMC-K, the addition of bamboo-derived cross-linked CMC-NH is too excessive, making the composite biocontrol microspheres of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH more prone to swelling. This reduces the compressive strength of the composite biocontrol microspheres and causes them to disintegrate too quickly in humid environments. Consequently, the biocontrol bacteria lack a long-term stable "sanctuary" and cannot achieve long-term control.

[0059] Examples 6-8 Examples 6-8 are based on the preparation method of Example 1, but the type of adhesive is adjusted, as shown in Table 3.

[0060] The bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres from Examples 6-8 were subjected to the above-mentioned performance tests, and the test results are shown in Table 3.

[0061] Table 3. Types of adhesives and their performance test results for Examples 1 and 6-8

[0062] Referring to Table 3, a comparison of Examples 1 and 6-8 shows that the bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres obtained using maltodextrin as a binder exhibit the best performance. This is likely because maltodextrin has good viscosity, forming a strong, transparent film after drying, which tightly binds the composite substrate particles, resulting in ideal compressive strength for the bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres. Furthermore, as a sugar derivative, maltodextrin can replace some water molecules during the drying process, forming hydrogen bonds with phospholipids and proteins in the biocontrol bacteria cell membrane, thus playing a "water replacement" role, stabilizing cell structure, and improving the survival rate of biocontrol bacteria.

[0063] Examples 9-11 Examples 9-11 are based on the preparation method of Example 1, but the proportion of the amount of microbial active protectant added to the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate is adjusted, as shown in Table 4.

[0064] Performance testing The bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres from Examples 1 and 9-11 were analyzed using the following specific detection methods:

[0065] 1. Storage survival rate Weigh 1g of intact bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres stored for 6 months. Rinse the surface twice with sterile physiological saline. After drying, cut open the eluted bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, take the core tissue and place it in 99mL of sterile physiological saline. Grind and shake for 30min to obtain a core layer bacterial suspension. Dilute the surface layer bacterial suspension and the core layer bacterial suspension and spread them on a selective culture medium. Count the microorganisms to obtain N1. Immediately after the microsphere preparation is completed, separate the core layer using the same method as above and detect the initial core layer viable bacterial concentration N. 0， Core layer bacterial survival rate (%) = N0 / N1 × 100%.

[0066] Based on the above detection method, the test results of Example 1 and Examples 9-11 were obtained, as shown in Table 4 below.

[0067] Table 4. The proportion of microbial activity protectant added in Examples 1 and 9-11 to the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate, and their performance test results.

[0068] Referring to Table 4, a comparison of Examples 1 and 9-11 shows that when the amount of microbial active protectant added is within the range of 2-3% of the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate, especially when the amount of microbial active protectant added is within 2% of the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate, the performance of the resulting bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres is optimal. This may be because when the amount of microbial active protectant added is too small, it is impossible to form a complete protective layer for all biocontrol bacteria cells. During the drying process, a large number of cells die due to direct exposure to dehydration stress, resulting in the initial viable bacteria count in the bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres being far lower than expected, directly weakening the application effect of the biocontrol agent. Furthermore, due to insufficient protection of the biocontrol bacteria, the resistance to temperature and humidity fluctuations during subsequent storage is also poor, resulting in a shortened shelf life.

[0069] Examples 12-13 Examples 12-13 are based on the preparation method of Example 1, but the types of microbial activity protectants are adjusted, as shown in Table 5.

[0070] The bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres from Examples 12-13 were subjected to the above-mentioned performance tests, and the test results are shown in Table 5.

[0071] Table 5. Types of microbial activity protectants and their performance test results in Examples 1 and 12-13.

[0072] Referring to Table 5, a comparison of Examples 1 and 12-13 shows that the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres obtained using mannitol as a microbial activity protectant exhibit the best performance. This is likely because mannitol contains six hydroxyl groups, which can form strong hydrogen bonds with the polar heads of the phospholipid bilayer of the biocontrol bacteria cell membrane, as well as the amino and carboxyl groups of proteins. During the drying and dehydration process, mannitol can replace water molecules to occupy the hydrogen bond binding sites on the surface of the bacterial cells, preventing the aggregation and fusion of cell membrane phospholipid molecules due to water loss, while also preventing protein deformation and inactivation, thus reducing bacterial death at the source during drying. Furthermore, mannitol has a certain free radical scavenging ability, which can neutralize reactive oxygen species generated during the metabolism of biocontrol bacteria, reduce ROS oxidative damage to cell membrane lipids, and prolong the survival period of biocontrol bacteria in the soil.

[0073] Examples 14-17 Examples 14-17 are based on the preparation method of Example 1, but the solid-liquid mass ratio of the composite substrate particles and the biocontrol bacteria loading liquid is adjusted, as shown in Table 6.

[0074] The bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres from Examples 14-17 were subjected to the above-mentioned performance tests, and the test results are shown in Table 6.

[0075] Table 6. Microbial activity protectants and their performance test results in Examples 1 and 14-17

[0076] Referring to Table 6, a comparison of Examples 1 and 14-17 shows that when the solid-liquid mass ratio of the composite substrate particles to the biocontrol bacteria loading liquid is in the range of 1:(1.5-2.5), especially when the solid-liquid mass ratio of the composite substrate particles to the biocontrol bacteria loading liquid is 1:2, the resulting bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol bacteria microspheres exhibit the best performance. This may be because when the solid-liquid mass ratio is too high, the biocontrol bacteria loading liquid is insufficient and cannot penetrate into the pores, causing the biocontrol bacteria to adhere only to the surface of the substrate. During the drying process, they are prone to inactivation due to direct contact with the external environment. Furthermore, the binder cannot uniformly coat the composite substrate particles, resulting in insufficient adhesion between the composite substrate particles. The medium causes a decrease in the compressive strength of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. When the solid-liquid mass ratio is too low, the excessive biocontrol loading liquid will cause the composite substrate particles to be in a highly moist state, which is prone to excessive adhesion during the granulation process, forming irregular large-size agglomerates. Due to the poor air permeability inside the agglomerates, the "dry outside and wet inside" phenomenon is prone to occur during the drying process. The internal biocontrol bacteria will become moldy and inactive due to lack of oxygen and water retention. Furthermore, the excessive biocontrol loading liquid will destroy the three-dimensional network structure of cross-linked CMC-K / cross-linked CMC-NH, resulting in a decrease in the compressive strength of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres.

[0077] Example 18 Example 18 is based on the preparation method of Example 1, but with the addition of kaolin in the substrate preparation step. The substrate preparation steps are as follows: bamboo-derived crosslinked CMC-K, bamboo-derived crosslinked CMC-NH and kaolin are mixed and pulverized to 90 mesh to obtain 50g of composite substrate particles. The amount of kaolin added accounts for 3% of the total amount of the bamboo-derived crosslinked CMC-K substrate and the bamboo-derived crosslinked CMC-NH substrate, and the other conditions remain unchanged.

[0078] Examples 19-22 Examples 19-22 are based on the preparation method of Example 18, but the proportion of kaolin added to the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate is adjusted, as shown in Table 7.

[0079] The bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres from Examples 18-22 were subjected to the above-mentioned performance tests, and the test results are shown in Table 7.

[0080] Table 7. The proportion of kaolin added in Examples 1 and 18-22 to the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate, and their performance test results.

[0081] Referring to Table 7, a comparison of Examples 1 and 18-22 shows that the addition of kaolin significantly improves the performance of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. This is likely because the layered particles of kaolin have high hardness and rigidity, allowing them to act as a "rigid filler" filling the three-dimensional network pores of the cross-linked CMC-K / CMC-NH composite substrate, forming a "rigid support-flexible adhesion" composite structure with the binder, significantly improving the compressive strength of the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. Simultaneously, the negatively charged surface of kaolin allows it to bind with negatively charged biocontrol bacteria cells through electrostatic adsorption, forming a "mineral protective layer" that enhances the resistance of the biocontrol bacteria and protects their activity.

[0082] Comparative examples 18-22 show that when the amount of kaolin added accounts for 1-5% of the total amount of the bamboo-derived crosslinked CMC-K substrate and the bamboo-derived crosslinked CMC-NH substrate, especially when the amount of kaolin added accounts for 3% of the total amount of the bamboo-derived crosslinked CMC-K substrate and the bamboo-derived crosslinked CMC-NH substrate, the performance of the resulting bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres is optimal. This may be because when the amount of kaolin added is too small, the kaolin cannot fully fill the crosslinked CMC-K / crosslinked CMC-NH substrate. The three-dimensional network pores of the C-NH composite substrate do not significantly improve the compressive strength of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres. When too much kaolin is added, the excess kaolin will block the three-dimensional network structure of the cross-linked CMC-K / cross-linked CMC-NH composite substrate, making the structure of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres too dense. This makes it difficult for the biocontrol bacteria to come into contact with external moisture and nutrients, and hinders the germination of Trichoderma harzianum spores and Bacillus subtilis spores.

[0083] All of the above Examples 1-22 can be put into practical use. The following application examples are based on Example 1 and are illustrated by way of example.

[0084] Application Example 1 During the planting period of tomatoes, the bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres prepared in Example 1 were evenly spread in the planting holes at a rate of 30 kg / mu, and after being slightly mixed with the soil, they were managed as usual. No additional potassium and nitrogen fertilizers were provided during the growth period of tomatoes.

[0085] Comparative Example 3 During the transplanting stage of tomato planting, the application of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres was not performed, while other conditions remained unchanged.

[0086] After the tomatoes entered the harvest period, the number of normal tomatoes, the number of tomatoes with root rot, and the yield of tomatoes in each group of fields were investigated to obtain the incidence rate of root rot.

[0087] Table 8 Performance Test Table for Application Example 1 and Comparative Example 3

[0088] Referring to Table 8, a comparison of Application Example 1 and Comparative Example 3 shows that the bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres have a better control effect on tomato root rot and can promote the increase of tomato fruit yield.

[0089] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, characterized in that, Includes the following steps: Substrate preparation: Bamboo-derived crosslinked CMC-K and bamboo-derived crosslinked CMC-NH are mixed and then pulverized to 80-100 mesh to obtain composite substrate particles; Preparation of loading solution: Dissolve the binder and microbial activity protectant in deionized water, stir evenly, add biocontrol agent, and after thorough dispersion, obtain a uniform biocontrol agent loading solution; Composite adsorption: After mixing the composite substrate particles and the biocontrol bacteria loading liquid, the mixture is allowed to stand at room temperature for adsorption, resulting in a wet composite substrate loaded with biocontrol bacteria. Molding and drying: The wet composite substrate loaded with biocontrol bacteria is granulated and dried until the moisture content is ≤10% to obtain bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol bacteria microspheres.

2. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 1, characterized in that, The dry weight ratio of the bamboo-derived crosslinked CMC-K to the bamboo-derived crosslinked CMC-NH is (1.5-3):

1.

3. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 1, characterized in that, The binder is at least one of maltodextrin, soluble starch, oligosaccharides, and low-viscosity cellulose ether.

4. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 1, characterized in that, The amount of the microbial active protectant added accounts for 2-3% of the total amount of bamboo-derived crosslinked CMC-K substrate and bamboo-derived crosslinked CMC-NH substrate.

5. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 4, characterized in that, The microbial activity protectant is at least one of mannitol, sorbitol, and xylitol.

6. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 1, characterized in that, The biocontrol agent is a mixture of Trichoderma harzianum spores and Bacillus subtilis spores.

7. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 1, characterized in that, The solid-liquid mass ratio of the composite substrate particles and the biocontrol bacteria loading liquid is 1:(1.5-2.5).

8. The method for preparing bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres according to claim 1, characterized in that, Kaolin is also added in the substrate preparation step, and the amount of kaolin added accounts for 1-5% of the total amount of the bamboo-derived crosslinked CMC-K substrate and the bamboo-derived crosslinked CMC-NH substrate.

9. A bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, characterized in that, It is prepared by the method for preparing bamboo-derived crosslinked CMC-K and crosslinked CMC-NH composite biocontrol microspheres as described in any one of claims 1-8.

10. An application of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres, characterized in that, The application of bamboo-derived cross-linked CMC-K and cross-linked CMC-NH composite biocontrol microspheres as described in claim 9 in the prevention and control of soil-borne diseases in farmland.

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