Composite microbial agent containing specific active ingredients of bamboos and application of composite microbial agent

Abstract

The invention relates to the technical field of microbial agents, in particular to a composite microbial agent containing specific active ingredients of bamboo and application of the composite microbial agent, and the composite microbial agent is prepared through the steps of S1 bamboo pretreatment, S2 extraction of the active ingredients of the bamboo and S3 preparation of the composite microbial agent. According to the method, bamboo is pretreated, the extraction rate of specific active ingredients such as polysaccharide, cellulose, growth hormone and plant hormone in the bamboo can be increased, then sodium alginate and polyaspartic acid are used as coating agents, halloysite nanotubes are used as framework materials, and a calcium chloride cross-linking method is adopted, so that the composite material is obtained. Active components obtained through extraction and microbial strains are loaded in gel, the gel has high water content, growth and reproduction of microorganisms can be well promoted in cooperation with specific active components obtained through extraction from bamboos, insoluble mineral elements in soil can be better converted into forms capable of being absorbed by plants, and the soil quality is improved. And heavy metals in the soil are restored, so that the soil is better beneficial to crop growth.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial agents, and specifically to a composite microbial agent containing specific active ingredients of bamboo and its application. Background Art

[0002] The treatment of soil heavy metal pollution is a major problem in the world today. Since heavy metal pollution in soil is an irreversible process, and heavy metals in soil are non-degradable and difficult to remove by physical and chemical methods. It is very difficult and expensive to repair soil heavy metal pollution by traditional methods. In recent years, with the rapid development of mining, chemical industry, printing and dyeing textile industry and the excessive application of chemical drugs in agricultural production, the soil heavy metal pollution has become increasingly serious, posing a potential safety hazard to human health.

[0003] Microbial technology has gradually attracted people's attention due to its advantages such as ecology, low cost, simplicity, high efficiency and wide application. For example, Chinese Patent CN109797123B discloses a microbial agent and its preparation method and application. The microbial agent includes an adsorption carrier and mixed microorganisms. The mixed microorganisms include Bacillus mucilaginosus, Erwinia and Acidovorax facilis. Its preparation method is: preparing a mixed microbial fermentation broth containing Bacillus mucilaginosus, Erwinia and Acidovorax facilis and an adsorption carrier; mixing the mixed microbial fermentation broth and the adsorption carrier to obtain a microbial agent; in this microbial agent, the adsorption carrier illite powder and soluble sugar provide a place and nutrients for the growth and reproduction of microorganisms. However, the biggest defect of this adsorption carrier is that it cannot retain nutrients inside for a long time, and during the subsequent drying process, a large amount of water will be lost, thus providing a suitable place for the growth and reproduction of microorganisms, resulting in poor repair effect and short repair cycle when the microbial agent is used to repair soil.

[0004] Therefore, selecting a suitable carrier to retain the nutrients and moisture required for the growth and reproduction of suitable microorganisms inside for a long time, so as to provide a good living environment for microorganisms, is a research focus of the existing technology. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a composite microbial agent containing specific active ingredients of bamboo and its application.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A composite microbial agent containing specific active ingredients of bamboo specifically includes the following steps: S1 Bamboo pretreatment Add thermally expandable microspheres into an aqueous solution of sodium dodecyl sulfate to prepare an impregnating solution. Then, use the impregnating solution to perform vacuum impregnation treatment on bamboo. After air-drying at room temperature for 48 - 50 h, heat-treat at 125 - 135 °C for 2 - 3 h to obtain the product; Extraction of bamboo active ingredients Cut and crush the pretreated bamboo to obtain bamboo chips. Then, place the bamboo chips in an extraction tank, use ethanol with a concentration of 75 - 80% as the extraction solvent, extract at 125 - 128 °C for 5 - 10 min, repeat the process 2 - 3 times. Filter, concentrate, and then freeze-dry the obtained extract to obtain bamboo active ingredients; Preparation of composite microbial inoculum Add the microbial strain suspension into a mixed solution of sodium alginate, polyaspartic acid, halloysite nanotubes, and bamboo active ingredients using YPD medium as the solvent. After fully stirring until the microbial strains are evenly dispersed, introduce it into a syringe and extrude it into a calcium chloride solution through a needle. Keep it for 72 - 75 h, and then repeatedly rinse with deionized water until it is neutral;

[0007] As a further preferred embodiment of the present invention, in S1, the vacuum impregnation treatment is specifically operated as follows: Put the bamboo into a container and seal it in an impregnation tank. Use a vacuum pump to raise the vacuum degree of the impregnation tank to 0.09 - 0.10 MPa, and keep it for 45 - 60 min. After stopping vacuum pumping, use the negative pressure in the impregnation tank to suck the impregnating solution into the container, and keep the bamboo below the liquid level. Then, open the air inlet valve and connect to the atmosphere to make the pressure inside and outside the impregnation tank reach equilibrium. Then, close the air inlet valve again and introduce nitrogen to pressurize to 0.5 - 0.7 MPa. Keep it for 60 - 80 min and then release the pressure, and take out the bamboo;

[0008] As a further preferred embodiment of the present invention, the mass fraction of the aqueous solution of sodium dodecyl sulfate is 0.1 - 0.2%; The mass fraction of the thermally expandable microspheres contained in the impregnating solution is 2 - 3%; The ratio of the bamboo chips to the extraction solvent is (5 - 10) g : (20 - 40) mL.

[0009] As a further preferred embodiment of the present invention, the microbial strain suspension is composed of a suspension of Bacillus mucilaginosus with a concentration of (2 - 5)×10 7 cfu / mL, a suspension of Geobacter metallireducens with a concentration of (1 - 3)×10 7 cfu / mL, and a suspension of Bacillus megaterium with a concentration of (1 - 2)×10 7 cfu / mL in a volume ratio of 1∶1∶1; The volume ratio of the microbial strain suspension to the YPD culture medium is 1:(12-16); In the mixed solution, the concentration of sodium alginate is 2-4wt%, the concentration of polyaspartic acid is 3-5wt%, the concentration of halloysite nanotubes is 1.0-1.6wt%, and the concentration of bamboo active ingredients is 1-2wt%; The calcium chloride solution has a concentration of 8-10wt%.

[0010] As a further preferred embodiment of the present invention, the heat-expandable microspheres are prepared by the following method: 1) Sodium chloride, sodium hydroxide, magnesium chloride and a sodium dodecyl sulfate solution with a concentration of 1.0-1.6 wt% are sequentially added into deionized water, and the mixture is fully stirred in an ice water bath to obtain an aqueous phase; 2) Add acrylonitrile, methyl acrylate and vinyl acetate to azobisisobutyronitrile in sequence, seal the mixture and place it in an ice water bath, stir the mixture, then add 1,4-butanediol dimethacrylate and n-hexane in sequence, seal the mixture and continue stirring to obtain an oil phase; 3) The water phase and the oil phase are sequentially added to a container placed in an ice water bath, and then the composite nanomaterial is added. After sealing, stirring is continued at 1000-2000 r / min for 15-20 min, and then the temperature is raised to 55-58°C at 300-350 r / min, maintained for 2-3 h, and then the temperature is raised to 62-65°C, and the reaction is continued for 19-24 h to obtain a suspended liquid; 4) After the suspension is filtered, the obtained product is transferred to deionized water, and ultrasonically treated at 300-400W for 10-15min, and the treatment is repeated 3-5 times. The obtained microsphere powder is placed at room temperature and in an atmospheric environment for 2-3 days, and vacuum dried at 45-47°C to constant weight to obtain heat-expandable microspheres.

[0011] Furthermore, the ratio of the aqueous phase, sodium chloride, sodium hydroxide, magnesium chloride, sodium dodecyl sulfate solution, and deionized water is (5.0-7.0) g: (2.0-2.8) g: (6.0-7.5) g: (820-1000) μL: (54-82) mL; The ratio of the oil phase, azobisisobutyronitrile, acrylonitrile, methyl acrylate, vinyl acetate, 1,4-butanediol dimethacrylate, and n-hexane is (0.2-0.4) g: (12-17) g: (6-8) g: (2-3) g: (100-160) μL: (6-8) g; The volume ratio of the water phase to the oil phase is (3.0-3.5):1; The composite nano material is added in an amount of 3-5% of the mass of the water phase.

[0012] As a further preferred embodiment of the present invention, the preparation method of the composite nanomaterial is as follows: 1) Dissolve 2 - 3 g of sodium hydroxide, 0.7 - 1.1 g of calcium chloride, and 0.9 - 1.4 g of sodium dihydrogen phosphate in 24 - 36 mL of deionized water respectively to prepare calcium chloride solution, sodium dihydrogen phosphate solution, and sodium hydroxide solution. Then put 32 - 46 mL of oleic acid into a container, successively add 40 - 60 mL of ethanol and 24 - 36 mL of sodium hydroxide solution, and stir for 15 - 30 min; 2) Then continue to successively add 24 - 36 mL of calcium chloride solution, 24 - 36 mL of sodium dihydrogen phosphate solution, and 5 - 8 g of porous nanosheet material. After ultrasonic dispersion for 1 - 2 h, transfer it to a high - pressure reaction kettle, and carry out hydrothermal reaction at 500 - 800 r / min under mechanical stirring for 24 - 27 h. After the reaction is completed, add 1 - 3 g of spiky nanoparticles, mechanically stir at 1000 - 1500 r / min for 1 - 2 h, and perform ultrasonic treatment at 500 - 800 W for 1 - 2 h. After the treatment is completed, take the sediment product, wash it repeatedly with ethanol and deionized water, and then dry it to obtain the composite nanomaterial.

[0013] Furthermore, in step 2), the power of the ultrasonic dispersion is 200 - 300 W; The temperature of the hydrothermal reaction is 180 - 186 °C.

[0014] As a further preferred embodiment of the present invention, for the porous nanosheet material, using sodium dodecyl sulfate as a soft template agent, after the aging reaction of mixing zinc acetate, 2 - methylimidazole and sodium dodecyl sulfate at room temperature, the template agent is removed by solvent washing to synthesize the porous nanosheet material.

[0015] Furthermore, the specific preparation method of the porous nanosheet material is as follows: 1) Dissolve 3 - 5 g of zinc acetate, 3.3 - 5.6 g of 2 - methylimidazole, and 1.9 - 3.2 g of sodium dodecyl sulfate in 100 - 170 mL of deionized water respectively. After ultrasonic dispersion for 1 - 5 min, obtain uniform dispersion liquids respectively and set aside; 2) At room temperature, inject the above - mentioned sodium dodecyl sulfate dispersion liquid into the zinc acetate dispersion liquid, and then quickly inject the 2 - methylimidazole dispersion liquid. Stir quickly for 10 - 20 s to form a mixed liquid. Seal the mixed liquid in a container and let it stand and react at a constant temperature of 26 - 28 °C for 24 - 30 h. After the reaction is completed, collect the product by centrifugation and set aside; 3) At room temperature, wash the above - mentioned product repeatedly by centrifugation with methanol, and then repeatedly by centrifugation with deionized water. Let it stand in ethanol for 24 - 30 h, and then place it in a vacuum drying oven at 60 - 70 °C for drying treatment for 24 - 30 h to obtain the porous nanosheet material.

[0016] As a further preferred embodiment of the present invention, the spiky nanoparticles are synthesized from chloroauric acid as a raw material by the seed growth method to obtain nanoparticles with a short rod structure, and using the nanoparticles with the short rod structure as seeds, cetyltrimethylammonium chloride is used to accelerate the anisotropic growth of the particles, thereby obtaining spiky nanoparticles.

[0017] Furthermore, the specific preparation method of the spiky nanoparticles is as follows: 1) Add 7.5 - 15.0 mL of an aqueous solution of cetyltrimethylammonium bromide with a concentration of 0.1 - 0.2 mol / L to a container. Under room temperature stirring at 100 - 150 r / min, add 0.1 - 0.2 mL of a chloroauric acid solution with a concentration of 0.025 - 0.030 mol / L. Then, under vigorous stirring at 500 - 800 r / min, quickly add 0.6 - 1.2 mL of an ice-cold aqueous solution of sodium borohydride with a concentration of 0.01 - 0.02 mol / L, continue stirring for 2 - 5 min, and then let it stand in a constant temperature water bath at 28 - 30 °C for 3 - 5 h to obtain a spherical nanoparticle seed solution; 2) Under room temperature stirring at 100 - 150 r / min, add 5 - 10 mL of 0.1 - 0.2 mol / L cetyltrimethylammonium bromide and 32 - 65 μL of heptanol to a container. After mixing evenly, successively add 80 - 100 μL of a chloroauric acid solution with a concentration of 0.025 - 0.030 mol / L, 30 - 50 μL of a silver nitrate solution with a concentration of 0.01 - 0.02 mol / L, and 32 - 45 μL of an ascorbic acid solution with a concentration of 0.10 - 0.15 mol / L. Then add 600 - 900 μL of the spherical nanoparticle seed solution, stir well for 20 - 30 s, and then let it stand and grow in a constant temperature water bath at 28 - 30 °C for 3 - 5 h. Centrifuge and concentrate at 13000 - 15000 r / min for 15 - 20 min to obtain a dispersion of nanoparticles with a short rod structure; 3) Under stirring at 80 - 130 r / min, mix 1 - 2 mL of the nanoparticle dispersion with 500 - 1000 μL of a glutathione solution with a concentration of 0.01 - 0.02 mol / L and stir for 2 - 3 h to obtain a functionalized nanoparticle seed solution. Then, under stirring at room temperature at 100 - 150 r / min, sequentially add 5 - 10 mL of cetyltrimethylammonium chloride with a concentration of 0.04 - 0.06 mol / L, 50 - 100 μL of chloroauric acid solution with a concentration of 0.025 - 0.030 mol / L, and 30 - 60 μL of silver nitrate solution with a concentration of 1 - 2 mmol / L into the container. After stirring evenly, add 80 - 150 μL of ascorbic acid solution with a concentration of 0.1 - 0.2 mol / L. After the mixed solution becomes colorless, quickly add 60 - 120 μL of the functionalized nanoparticle seed solution, continue stirring for 5 - 10 min, let it stand and grow in a constant temperature water bath at 28 - 30 °C for 5 - 8 h. After repeatedly washing with ultrapure water, remove the supernatant, and after drying, thorn-shaped nanoparticles can be obtained.

[0018] The present invention also provides an application of the composite microbial agent in repairing soil heavy metal pollution and increasing crop yield. The application method is: spray the composite microbial agent in the farmland, and transplant the crops 12 - 15 days later. The spraying amount is 25 - 32 kg / mu.

[0019] Compared with the prior art, the beneficial effects of the present invention are: In the present invention, an oil phase composed of monomers, initiators, crosslinking agents, etc. is dispersed into a liquid in an aqueous phase under mechanical stirring, and a composite nanomaterial is also added. Through reaction polymerization, thermally expandable microspheres are obtained. Then, in a vacuum impregnation method, the thermally expandable microspheres are introduced into bamboo, and through heat treatment, the thermally expandable microspheres form multi-fold expansion in the bamboo cell cavities, so that the volume of the cell cavities can increase, which is beneficial for the subsequent extraction, and the active ingredients in the bamboo can be released better, thus helping to improve the extraction rate of the active ingredients in the bamboo. At the same time, since the outer shell of the thermally expandable microspheres is easy to soften, although it is beneficial for expansion, due to the reduction of the tensile strength, it cannot maintain the expanded state for a long time during the heating and expansion process and will quickly rupture, resulting in the slow restoration of the expanded cell cavities. Therefore, in order to prevent the slow restoration of the cell cavities after expansion, in the present invention, a composite nanomaterial is added when the aqueous phase and the oil phase are mixed and dispersed. The composite nanomaterial can form a three-dimensional structure in the thermally expandable microspheres, effectively playing the role of a supporting framework. It can not only improve the strength of the thermally expandable microspheres, enabling them to maintain the expanded state in the cell cavities for a long time, achieving the effect of long-term expansion plasticity of the cell cavities, so that the expanded cell cavities can maintain a large volume state for a long time. At the same time, when the thermally expandable microspheres rupture, the three-dimensional structure formed by the composite nanomaterial can remain in the cell cavities, continuously supporting the cell cavities, so that the cell cavities cannot return to their original state after expansion due to the existence of the supporting effect, enabling the cell cavities to maintain the expanded state for a long time, and the active ingredients in the cells can be released better, thus effectively improving the extraction rate. Moreover, since the three-dimensional structure formed by the composite nanomaterial is in a net-like form with many pores, sufficient channels are reserved for the release of the active ingredients, so it will not affect the extraction of the active ingredients.

[0020] In the composite nanomaterial of the present invention, sodium dodecyl sulfate, a surfactant, is used as a soft template agent. By precisely controlling the dosage ratio, system concentration, and dispersion uniformity of sodium dodecyl sulfate, a porous nanosheet material with a two-dimensional structure and stable pore structure and on-chip morphology is in-situ controllably synthesized. The pore structure of the porous nanosheet material is a through-hole, and it has micropores, mesopores, and macropores. The rich pore structures with different pore diameters provide abundant sites for the subsequent deposition of hydroxyapatite nanowires. Then, under mechanical stirring, nanowires are generated by hydrothermal method, and through mechanical stirring, the nanowires can be better embedded into the pores of the porous nanosheet material, thus forming a two-dimensional continuous-phase network structure with the porous nanosheet material as the connection nodes and the nanowires as the connection lines at the initial stage. However, as the hydrothermal reaction proceeds, the diameter and length of the nanowires will increase significantly. After the initially formed small-diameter nanowires are successfully embedded into the pores of the porous nanosheet material, with the progress of the reaction, the diameter increases, so that the gap with the pores gradually shrinks, making the nanowires well embedded in the pores and not easy to detach. At the same time, the increase in the length of the nanowires causes the distance between the nanosheets to gradually increase after the two ends of the nanowires are respectively connected to the nanosheets. As the distance increases, the nanowires can better form a winding connection with each other, thus forming a multi-layer connection relationship between the nanowires and the nanosheets, as well as between the nanowires and the nanowires, making the originally formed network structure more three-dimensional and constructing a three-dimensional structure. At the same time, in order to form a more stable structure between the nanowires and the porous nanosheet material and further improve the bonding strength between the two, in the preparation of the composite nanomaterial of the present invention, spiky nanoparticles are also added. Through mechanical stirring and ultrasonic treatment, the spiky nanoparticles can continuously insert into the gaps between the nanowires and the pores of the porous nanosheet material during high-speed movement, playing the role of rivets, so that the nanowires and the porous nanosheet material are in full contact and firmly bonded together, making the constructed three-dimensional structure more stable.

[0021] In the present invention, the prepared thermally expandable microspheres are formulated into an impregnating solution, and then a pretreatment process combining vacuum impregnation treatment and heat treatment of bamboo is carried out, which helps to improve the extraction rate of specific active ingredients such as polysaccharides, cellulose, growth hormones, and phytohormones in bamboo. Then, sodium alginate and polyaspartic acid are used as coating agents, and halloysite nanotubes are used as the framework material. Through the calcium chloride crosslinking method, the extracted active ingredients and microbial strains are loaded into the gel. The gel has a high water content and, combined with the specific active ingredients extracted from bamboo, can well promote the growth and reproduction of microorganisms. Thus, it can better convert insoluble phosphorus, potassium and other mineral elements in the soil into forms that can be absorbed by plants, and can also reduce the heavy metals remaining in the soil into stable compounds with low toxicity, realizing the remediation of heavy metal pollution and completing the remediation of the soil, making the soil more conducive to the growth of crops. Detailed implementation mode

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0023] In the embodiments of the present invention, the YPD medium (yeast extract peptone dextrose medium): 10 g of yeast extract, 20 g of peptone, 20 g of dextrose, 1000 mL of distilled water, autoclaved at 121 °C for 20 min.

[0024] In the embodiments of the present invention, the specific preparation method of the porous nanosheet material is as follows: 1) 3 g of zinc acetate, 3.3 g of 2-methylimidazole and 1.9 g of sodium dodecyl sulfate are respectively dissolved in 100 mL of deionized water. After ultrasonic dispersion for 1 min, uniform dispersions are obtained respectively and reserved; 2) At room temperature, the above sodium dodecyl sulfate dispersion is injected into the zinc acetate dispersion, and then the 2-methylimidazole dispersion is quickly injected. After rapid stirring for 10 s, a mixed solution is formed. The mixed solution is sealed in a container and allowed to stand and react at a constant temperature of 26 °C for 24 h. After the reaction is completed, the product is collected by centrifugation and reserved; 3) At room temperature, the product is repeatedly centrifuged and washed with methanol, and then repeatedly centrifuged and washed with deionized water, and stored in ethanol for 24 h. Subsequently, it is placed in a vacuum drying oven at 60 °C for drying treatment for 24 - 30 h to obtain the porous nanosheet material.

[0025] In the embodiments of the present invention, the specific preparation method of the spiky nanoparticles is as follows: 1) Add 7.5 mL of an aqueous solution of cetyltrimethylammonium bromide with a concentration of 0.1 mol / L into a container. Under stirring at room temperature of 100 r / min, add 0.1 mL of a chloroauric acid solution with a concentration of 0.025 mol / L. Then, under vigorous stirring at 500 r / min, quickly add 0.6 mL of an ice aqueous solution of sodium borohydride with a concentration of 0.01 mol / L. Continue stirring for 2 min, and then let it stand in a constant temperature water bath at 28 °C for 3 h to obtain a spherical nanoparticle seed solution; 2) Under stirring at room temperature of 100 r / min, add 5 mL of 0.1 mol / L cetyltrimethylammonium bromide and 32 μL of heptanol into a container. After mixing evenly, successively add 80 μL of a chloroauric acid solution with a concentration of 0.025 mol / L, 30 μL of a silver nitrate solution with a concentration of 0.01 mol / L, and 32 μL of an ascorbic acid solution with a concentration of 0.10 mol / L. Then add 600 μL of the spherical nanoparticle seed solution. After fully stirring for 20 s, let it stand and grow in a constant temperature water bath at 28 °C for 3 h. Centrifuge and concentrate at 13000 r / min for 15 min to obtain a nanoparticle dispersion with a short rod structure; 3) Under stirring at 80 r / min, mix 1 mL of the nanoparticle dispersion with 500 μL of a glutathione solution with a concentration of 0.01 mol / L and stir for 2 h to obtain a functionalized nanoparticle seed solution. Then, under stirring at room temperature of 100 r / min, successively add 5 mL of cetyltrimethylammonium chloride with a concentration of 0.04 mol / L, 50 μL of a chloroauric acid solution with a concentration of 0.025 mol / L, and 30 μL of a silver nitrate solution with a concentration of 1 mmol / L into a container. After fully stirring evenly, add 80 μL of an ascorbic acid solution with a concentration of 0.1 mol / L. After the mixed solution becomes colorless, quickly add 60 μL of the functionalized nanoparticle seed solution. Continue stirring for 5 min, let it stand and grow in a constant temperature water bath at 28 °C for 5 h. After repeatedly washing with ultrapure water, remove the supernatant, and dry it to obtain spiky nanoparticles.

[0026] Example 1 A composite microbial inoculant containing specific active ingredients of bamboo, specifically including the following steps: S1 Bamboo pretreatment Put bamboo into a container, then place the container in an impregnation tank and seal it, and use a vacuum pump to raise the vacuum degree of the impregnation tank to 0.09MPa, keep it for 45min, then add heat-expandable microspheres into a sodium dodecyl sulfate aqueous solution with a mass fraction of 0.1%, and after sufficient stirring and mixing, prepare an impregnation solution with a mass fraction of heat-expandable microspheres of 2%, then close the air inlet valve of the impregnation tank and the vacuum pump, use the negative pressure in the impregnation tank to suck the impregnation solution into the container with bamboo in the impregnation tank, and keep the bamboo below the liquid level, then open the air inlet valve and connect it to the atmosphere, so that the internal and external pressures of the impregnation tank reach equilibrium, then close the air inlet valve again and introduce nitrogen to pressurize it to 0.5MPa, keep it for 60min and then release the pressure, take out the bamboo, air-dry it at room temperature for 48h, and then heat treat it at 125℃ for 2h; Extraction of active ingredients from S2 bamboo The pretreated bamboo was cut into small pieces and crushed by a grinder to obtain bamboo chips. Then 5 g of bamboo chips were weighed and placed in an extraction cell. 20 mL of 75% ethanol was used as an extraction solvent. The extraction was performed at 125°C for 5 min. The cycle was repeated twice. The obtained extract was filtered, concentrated, and freeze-dried to obtain the active ingredients of bamboo. Preparation of S3 composite microbial agent The microbial strain suspension is added to a mixed solution of sodium alginate, polyaspartic acid, halloysite nanotubes and bamboo active ingredients in YPD medium as a solvent, and after being fully stirred until the microbial strain is evenly dispersed, it is introduced into a syringe and squeezed into a calcium chloride solution with a concentration of 8wt% through a needle, stored for 72 hours, and then repeatedly rinsed with deionized water until neutral; Microbial strain suspension, with a concentration of 2×10 7 cfu / mL of jelly-like Bacillus suspension, concentration of 1×10 7 cfu / mL of Geobacter metal-reducing suspension and a concentration of 1×10 7 cfu / mL of Bacillus megaterium suspension was composed in a volume ratio of 1:1:1; The volume ratio of microbial strain suspension to YPD medium is 1:12; In the mixed solution, the concentration of sodium alginate was 2 wt %, the concentration of polyaspartic acid was 3 wt %, the concentration of halloysite nanotubes was 1.0 wt %, and the concentration of bamboo active ingredients was 1 wt %.

[0027] The preparation method of heat-expandable microspheres is as follows: 1) 5.0 g of sodium chloride, 2.0 g of sodium hydroxide, 6.0 g of magnesium chloride and 820 μL of 1.0 wt% sodium dodecyl sulfate solution were sequentially added into 54 mL of deionized water, and stirred at 400 r / min for 40 min in an ice water bath to obtain an aqueous phase; 2) 12 g of acrylonitrile, 6 g of methyl acrylate, and 2 g of vinyl acetate were successively added to 0.2 g of azobisisobutyronitrile. After sealing, the mixture was placed in an ice-water bath and stirred at 400 r / min for 5 min. Then, 100 μL of 1,4-butanediol dimethacrylate and 6 g of n-hexane were successively added. After sealing, the mixture was continuously stirred for 25 min to obtain an oil phase; 3) The aqueous phase and the oil phase were successively added to a container placed in an ice-water bath according to a volume ratio of 3:1. Then, a composite nanomaterial accounting for 3% of the mass of the aqueous phase was added. After sealing, the mixture was continuously stirred at 1000 r / min for 15 min. Then, the temperature was raised to 55 °C at 300 r / min and maintained for 2 h. Subsequently, the temperature was raised to 62 °C and the reaction was continued for 19 h to obtain a suspension; 4) After the suspension was filtered by suction, the obtained product was transferred to deionized water and ultrasonically treated at 300 W for 10 min. This treatment was repeated 3 times. The obtained microsphere powder was placed at room temperature and in an atmospheric environment for 2 d and then vacuum dried at 45 °C to constant weight to obtain the thermally expandable microspheres.

[0028] The preparation method of the above composite nanomaterial is as follows: 1) 2 g of sodium hydroxide, 0.7 g of calcium chloride, and 0.9 g of sodium dihydrogen phosphate were respectively dissolved in 24 mL of deionized water to prepare a calcium chloride solution, a sodium dihydrogen phosphate solution, and a sodium hydroxide solution. Then, 32 mL of oleic acid was placed in a container, and 40 mL of ethanol and 24 mL of the sodium hydroxide solution were successively added, and the mixture was stirred for 15 - 30 min; 2) Then, 24 mL of the calcium chloride solution, 24 mL of the sodium dihydrogen phosphate solution, and 5 g of porous nanosheet material were successively added. After ultrasonic dispersion at 200 W for 1 h, the mixture was transferred to a high-pressure reaction kettle. Under mechanical stirring at 500 r / min, a hydrothermal reaction was carried out at 180 °C for 24 h. After the reaction ended, 1 g of spiky nanoparticles was added, and the mixture was mechanically stirred at 1000 r / min for 1 h and ultrasonically treated at 500 W for 1 h. After the treatment ended, the precipitated product was taken, washed repeatedly with ethanol and deionized water, and then dried to obtain the composite nanomaterial.

[0029] Example 2 A composite microbial inoculant containing specific active ingredients of bamboo specifically includes the following steps: S1 Bamboo pretreatment Put bamboo into a container, then place the container in an impregnation tank and seal it, and use a vacuum pump to raise the vacuum degree of the impregnation tank to 0.10MPa, keep it for 55min, then add heat-expandable microspheres into a sodium dodecyl sulfate aqueous solution with a mass fraction of 0.15%, and after sufficient stirring and mixing, prepare an impregnation solution with a mass fraction of heat-expandable microspheres of 2-3%, then close the air inlet valve of the impregnation tank and the vacuum pump, use the negative pressure in the impregnation tank to suck the impregnation solution into the container with bamboo in the impregnation tank, and keep the bamboo below the liquid level, then open the air inlet valve and connect it to the atmosphere, so that the internal and external pressures of the impregnation tank reach equilibrium, then close the air inlet valve again and introduce nitrogen to pressurize to 0.6MPa, keep it for 70min and then release the pressure, take out the bamboo, air-dry it at room temperature for 50h, and then heat-treat it at 130℃ for 2.5h; Extraction of active ingredients from S2 bamboo The pretreated bamboo was cut into small pieces and crushed by a grinder to obtain bamboo chips. Then 8 g of bamboo chips were weighed and placed in an extraction tank. 30 mL of 78% ethanol was used as an extraction solvent. The extraction was performed at 126°C for 7 min and the cycle was repeated 3 times. The obtained extract was filtered, concentrated and freeze-dried to obtain the active ingredients of bamboo. Preparation of S3 composite microbial agent The microbial strain suspension is added to a mixed solution of sodium alginate, polyaspartic acid, halloysite nanotubes and bamboo active ingredients in YPD medium as a solvent, and after being fully stirred until the microbial strain is evenly dispersed, it is introduced into a syringe and squeezed into a 9wt% calcium chloride solution through a needle, stored for 73 hours, and then repeatedly rinsed with deionized water until neutral; Microbial strain suspension, with a concentration of 3×10 7 cfu / mL of jelly-like Bacillus suspension, concentration of 2×10 7 cfu / mL of Geobacter metal-reducing suspension and a concentration of 2×10 7 cfu / mL of Bacillus megaterium suspension was composed in a volume ratio of 1:1:1; The volume ratio of microbial strain suspension to YPD medium is 1:15; In the mixed solution, the concentration of sodium alginate was 3wt%, the concentration of polyaspartic acid was 4wt%, the concentration of halloysite nanotubes was 1.3wt%, and the concentration of bamboo active ingredients was 1.5wt%.

[0030] The preparation method of heat-expandable microspheres is as follows: 1) 6.0 g of sodium chloride, 2.5 g of sodium hydroxide, 6.8 g of magnesium chloride and 950 μL of 1.4 wt% sodium dodecyl sulfate solution were sequentially added into 70 mL of deionized water, and stirred at 500 r / min for 50 min in an ice water bath to obtain an aqueous phase; 2) To 0.3 g of azobisisobutyronitrile, 15 g of acrylonitrile, 7 g of methyl acrylate and 2.5 g of vinyl acetate were added in sequence. After sealing, it was placed in an ice-water bath and stirred at 500 r / min for 7 min. Then, 130 μL of 1,4-butanediol dimethacrylate and 7 g of n-hexane were added in sequence. After sealing, it was continuously stirred for 35 min to obtain an oil phase; 3) According to a volume ratio of 3.2:1, the aqueous phase and the oil phase were added to a container placed in an ice-water bath in sequence. Then, a composite nanomaterial accounting for 4% of the mass of the aqueous phase was added. After sealing, it was continuously stirred at 1500 r / min for 17 min. Then, at 320 r / min, the temperature was raised to 56 °C and maintained for 2.5 h. Then, the temperature was raised to 63 °C and the reaction was continued for 21 h to obtain a suspension; 4) After the suspension was filtered by suction, the obtained product was transferred to deionized water and ultrasonically treated at 350 W for 12 min. The treatment was repeated 4 times. The obtained microsphere powder was placed at room temperature and in an atmospheric environment for 3 d and dried in vacuo at 46 °C to constant weight to obtain thermally expandable microspheres.

[0031] The preparation method of the above composite nanomaterial is as follows: 1) 2.5 g of sodium hydroxide, 0.9 g of calcium chloride and 1.2 g of sodium dihydrogen phosphate were respectively dissolved in 30 mL of deionized water to prepare a calcium chloride solution, a sodium dihydrogen phosphate solution and a sodium hydroxide solution. Then, 38 mL of oleic acid was placed in a container, and 50 mL of ethanol and 30 mL of the sodium hydroxide solution were added in sequence and stirred for 25 min; 2) Then, 30 mL of the calcium chloride solution, 30 mL of the sodium dihydrogen phosphate solution and 7 g of porous nanosheet material were continuously added in sequence. After ultrasonic dispersion at 250 W for 1.5 h, it was transferred to a high-pressure reaction kettle. Under mechanical stirring at 700 r / min, a hydrothermal reaction was carried out at 182 °C for 25 h. After the reaction was completed, 2 g of spiky nanoparticles were added and mechanically stirred at 1200 r / min for 1.5 h and ultrasonically treated at 600 W for 1.5 h. After the treatment was completed, the sedimentation product was taken, washed repeatedly with ethanol and deionized water and then dried to obtain the composite nanomaterial.

[0032] Example 3 A composite microbial inoculant containing specific active ingredients of bamboo specifically comprises the following steps: S1 Bamboo pretreatment Put bamboo into a container, then place the container in an impregnation tank and seal it, and use a vacuum pump to raise the vacuum degree of the impregnation tank to 0.10MPa, keep it for 60min, then add heat-expandable microspheres into a sodium dodecyl sulfate aqueous solution with a mass fraction of 0.2%, and after sufficient stirring and mixing, prepare an impregnation solution with a mass fraction of heat-expandable microspheres of 3%, then close the air inlet valve of the impregnation tank and the vacuum pump, use the negative pressure in the impregnation tank to suck the impregnation solution into the container with bamboo in the impregnation tank, and keep the bamboo below the liquid level, then open the air inlet valve and connect it to the atmosphere, so that the internal and external pressures of the impregnation tank reach equilibrium, then close the air inlet valve again and introduce nitrogen to pressurize to 0.7MPa, keep it for 80min and then release the pressure, take out the bamboo, air-dry it at room temperature for 50h, and then heat treat it at 135℃ for 3h; Extraction of active ingredients from S2 bamboo The pretreated bamboo was cut into small pieces and crushed by a grinder to obtain bamboo chips. Then 10 g of bamboo chips were weighed and placed in an extraction tank. 40 mL of 80% ethanol was used as an extraction solvent. The extraction was performed at 128°C for 10 min, and the cycle was repeated 3 times. The obtained extract was filtered, concentrated, and freeze-dried to obtain the active ingredients of bamboo. Preparation of S3 composite microbial agent The microbial strain suspension is added to a mixed solution of sodium alginate, polyaspartic acid, halloysite nanotubes and bamboo active ingredients in YPD medium as a solvent, and after being fully stirred until the microbial strain is evenly dispersed, it is introduced into a syringe and squeezed into a 10wt% calcium chloride solution through a needle, stored for 75 hours, and then repeatedly rinsed with deionized water until neutral; Microbial strain suspension, with a concentration of 5×10 7 cfu / mL of jelly-like Bacillus suspension, concentration of 3×10 7 cfu / mL of Geobacter metal-reducing suspension and a concentration of 2×10 7 cfu / mL of Bacillus megaterium suspension was composed in a volume ratio of 1:1:1; The volume ratio of microbial strain suspension to YPD medium was 1:16; In the mixed solution, the concentration of sodium alginate was 4wt%, the concentration of polyaspartic acid was 5wt%, the concentration of halloysite nanotubes was 1.6wt%, and the concentration of bamboo active ingredients was 2wt%.

[0033] The preparation method of heat-expandable microspheres is as follows: 1) 7.0 g of sodium chloride, 2.8 g of sodium hydroxide, 7.5 g of magnesium chloride and 1000 μL of 1.6 wt% sodium dodecyl sulfate solution were sequentially added into 82 mL of deionized water, and stirred at 600 r / min for 60 min in an ice water bath to obtain an aqueous phase; 2) 17 g of acrylonitrile, 8 g of methyl acrylate, and 3 g of vinyl acetate were successively added to 0.4 g of azobisisobutyronitrile. After sealing, the mixture was placed in an ice-water bath and stirred at 600 r / min for 10 min. Then, 160 μL of 1,4-butanediol dimethacrylate and 8 g of n-hexane were successively added. After sealing, the mixture was stirred continuously for 40 min to obtain an oil phase; 3) According to a volume ratio of 3.5:1, the aqueous phase and the oil phase were successively added to a container placed in an ice-water bath. Then, a composite nanomaterial accounting for 5% of the mass of the aqueous phase was added. After sealing, the mixture was stirred continuously at 2000 r / min for 20 min. Then, at 350 r / min, the temperature was raised to 58 °C and maintained for 3 h. Then, the temperature was raised to 65 °C and the reaction was continued for 24 h to obtain a suspension; 4) After the suspension was filtered by suction, the obtained product was transferred to deionized water and ultrasonically treated at 400 W for 15 min. The treatment was repeated 5 times. The obtained microsphere powder was placed at room temperature and in an atmospheric environment for 3 d and then vacuum dried at 47 °C to constant weight to obtain the thermally expandable microspheres.

[0034] The preparation method of the above composite nanomaterial is as follows: 1) 3 g of sodium hydroxide, 1.1 g of calcium chloride, and 1.4 g of sodium dihydrogen phosphate were respectively dissolved in 36 mL of deionized water to prepare a calcium chloride solution, a sodium dihydrogen phosphate solution, and a sodium hydroxide solution. Then, 46 mL of oleic acid was placed in a container, and 60 mL of ethanol and 36 mL of the sodium hydroxide solution were successively added, and the mixture was stirred for 30 min; 2) Then, 36 mL of the calcium chloride solution, 36 mL of the sodium dihydrogen phosphate solution, and 8 g of the porous nanosheet material were successively added. After ultrasonic dispersion at 300 W for 2 h, the mixture was transferred to a high-pressure reaction kettle. Under mechanical stirring at 800 r / min, a hydrothermal reaction was carried out at 186 °C for 27 h. After the reaction ended, 3 g of the spiky nanoparticles were added, and the mixture was mechanically stirred at 1500 r / min for 2 h and ultrasonically treated at 800 W for 2 h. After the treatment ended, the sedimented product was taken, washed repeatedly with ethanol and deionized water, and then dried to obtain the composite nanomaterial.

[0035] Comparative Example 1: This comparative example was basically the same as Example 1, except that it did not contain the composite nanomaterial.

[0036] Comparative Example 2: This comparative example was basically the same as Example 1, except that in the preparation of the composite nanomaterial, it did not contain the porous nanosheet material.

[0037] Comparative Example 3: This comparative example was basically the same as Example 1, except that in the preparation of the composite nanomaterial, it did not contain the spiky nanoparticles.

[0038] Test experiment: Experimental Group 1: A contaminated pepper test field, where the compound microbial inoculant of Example 1 of the present invention was applied 15 days before pepper transplantation, and the spraying amount was 25 kg / mu; Control Group 1: A contaminated pepper test field, where the compound microbial inoculant of Comparative Example 1 of the present invention was applied 15 days before pepper transplantation, and the spraying amount was 25 kg / mu; Control Group 2: A contaminated pepper test field, where the compound microbial inoculant of Comparative Example 2 of the present invention was applied 15 days before pepper transplantation, and the spraying amount was 25 kg / mu; Control Group 3: A contaminated pepper test field, where the compound microbial inoculant of Comparative Example 3 of the present invention was applied 15 days before pepper transplantation, and the spraying amount was 25 kg / mu; Control Group 4: A contaminated pepper test field with no treatment measures.

[0039] The comparative experiment was carried out in a certain planting base in Liuyang City. The planted crop was pepper. The experiment adopted a randomized block design. One treatment group was set up, using the method of Experimental Group 1, and two control groups were set up, using the methods of Control Groups 1 - 4 respectively. Before the experiment, the Cd content in the soil was detected to be between 0.25 - 0.32 mg / kg and the pH value was between 6.52 - 6.58. During the specific operation, sowing or transplanting, fertilizing, watering, weeding, and pest control of each experimental group were completed within 1 day, reducing the human error to the minimum. Fertilization was carried out according to the local fertilization level and method. According to the weather and soil moisture conditions, ditches were dug to prepare for flood prevention and drought resistance. The microbial inoculant was applied manually. After pepper harvest, the pepper yield, soil available cadmium content, and cadmium content in pepper fruits were measured, and the results are shown in Table 1.

[0040] Table 1 As can be seen from Table 1, the compound microbial inoculant in the present invention can effectively reduce the bioavailability of heavy metal cadmium in the soil, making the soil more conducive to the growth of crops, thus helping to increase the crop yield.

[0041] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not elaborate on all the details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the relevant technical field can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A composite microbial inoculum containing specific active ingredients of bamboo, characterized in that, Specifically, it includes the following steps: S1 Bamboo pretreatment Add thermally expandable microspheres into an aqueous solution of sodium dodecyl sulfate to prepare an impregnating solution. Then use the impregnating solution to perform vacuum impregnation treatment on bamboo. After air-drying at room temperature for 48 - 50 h, heat-treat it at 125 - 135 °C for 2 - 3 h. S2 Extraction of bamboo active ingredients Cut and crush the pretreated bamboo to obtain bamboo chips. Then place the bamboo chips in an extraction pool, use ethanol with a concentration of 75 - 80% as the extraction solvent, extract at 125 - 128 °C for 5 - 10 min, cycle 2 - 3 times. Filter, concentrate, and then freeze-dry the obtained extractive solution to obtain bamboo active ingredients. S3 Preparation of compound microbial inoculum Add the microbial strain suspension into a mixed solution of sodium alginate, polyaspartic acid, halloysite nanotubes, and bamboo active ingredients using YPD medium as the solvent. Stir well until the microbial strains are evenly dispersed, then introduce it into a syringe and extrude it into a calcium chloride solution through a needle. Keep it for 72 - 75 h, and then repeatedly rinse it with deionized water until it is neutral.

2. The composite microbial inoculum containing specific active ingredients of bamboo according to claim 1, characterized in that, In S1, the specific operation of the vacuum impregnation treatment is as follows: Put the bamboo into a container and seal it in an impregnation tank. Use a vacuum pump to raise the vacuum degree of the impregnation tank to 0.09 - 0.10 MPa, maintain it for 45 - 60 min. After stopping vacuum pumping, use the negative pressure in the impregnation tank to suck the impregnating solution into the container, and keep the bamboo below the liquid level. Then open the air inlet valve and connect to the atmosphere to make the pressure inside and outside the impregnation tank reach equilibrium. Then close the air inlet valve again and pressurize with nitrogen to 0.5 - 0.7 MPa. Keep it for 60 - 80 min and then relieve the pressure, and take out the bamboo.

3. The composite microbial inoculum containing specific active ingredients of bamboo according to claim 1, characterized in that, The mass fraction of the aqueous solution of sodium dodecyl sulfate is 0.1 - 0.2%; The mass fraction of the thermally expandable microspheres contained in the impregnating solution is 2 - 3%; The ratio of the bamboo chips to the extraction solvent is (5 - 10) g : (20 - 40) mL.

4. A composite microbial inoculant containing specific active ingredients of bamboo according to claim 1, characterized in that, The microbial strain suspension is composed of a Bacillus mucilaginosus suspension with a concentration of (2-5)×10 7 cfu / mL, a Geobacter metallireducens suspension with a concentration of (1-3)×10 7 cfu / mL, and a Bacillus megaterium suspension with a concentration of (1-2)×10 7 cfu / mL, and they are composed in a volume ratio of 1∶1∶1; The volume ratio of the microbial strain suspension to the YPD medium is 1 : (12 - 16); In the mixed solution, the concentration of sodium alginate is 2 - 4 wt%, the concentration of polyaspartic acid is 3 - 5 wt%, the concentration of halloysite nanotubes is 1.0 - 1.6 wt%, and the concentration of bamboo active ingredients is 1 - 2 wt%; The concentration of the calcium chloride solution is 8 - 10 wt%.

5. A composite microbial inoculant containing specific active ingredients of bamboo according to claim 1, characterized in that, The preparation method of the thermally expandable microspheres is as follows: 1) Add sodium chloride, sodium hydroxide, magnesium chloride, and an aqueous solution of sodium dodecyl sulfate with a concentration of 1.0 - 1.6 wt% into deionized water in turn, and stir well in an ice-water bath to obtain an aqueous phase; 2) Add acrylonitrile, methyl acrylate, and vinyl acetate to azobisisobutyronitrile in turn. Seal it and place it in an ice-water bath. After stirring, add 1,4-butanediol dimethacrylate and n-hexane in turn, seal it and continue to stir to obtain an oil phase; 3) Add the aqueous phase and the oil phase successively into a container placed in an ice-water bath, then add the composite nanomaterial, seal it, and continue stirring at 1000 - 2000 r / min for 15 - 20 min. Then, at 300 - 350 r / min, raise the temperature to 55 - 58 °C and keep it for 2 - 3 h. Then raise the temperature to 62 - 65 °C and continue the reaction for 19 - 24 h to obtain a suspension liquid. 4) After filtering the suspension by suction, transfer the obtained product to deionized water, perform ultrasonic treatment at 300 - 400 W for 10 - 15 min, repeat the treatment 3 - 5 times, place the obtained microsphere powder at room temperature and in an atmospheric environment for 2 - 3 d, and dry it in vacuum at 45 - 47 °C to constant weight to obtain the thermally expandable microspheres.

6. The composite microbial inoculant containing specific active ingredients of bamboo according to claim 5, characterized in that, For the aqueous phase, the ratio of sodium chloride, sodium hydroxide, magnesium chloride, sodium dodecyl sulfate solution, and deionized water is (5.0 - 7.0) g : (2.0 - 2.8) g : (6.0 - 7.5) g : (820 - 1000) μL : (54 - 82) mL; For the oil phase, the ratio of azobisisobutyronitrile, acrylonitrile, methyl acrylate, vinyl acetate, 1,4 - butanediol dimethacrylate, and n - hexane is (0.2 - 0.4) g : (12 - 17) g : (6 - 8) g : (2 - 3) g : (100 - 160) μL : (6 - 8) g; For the aqueous phase and the oil phase, the volume ratio is (3.0 - 3.5) : 1; The addition amount of the composite nanomaterial is 3 - 5% of the mass of the aqueous phase.

7. A composite microbial inoculant containing specific active ingredients of bamboo according to claim 5, characterized in that, The preparation method of the composite nanomaterial is as follows: 1) Dissolve 2 - 3 g of sodium hydroxide, 0.7 - 1.1 g of calcium chloride, and 0.9 - 1.4 g of sodium dihydrogen phosphate in 24 - 36 mL of deionized water respectively to prepare calcium chloride solution, sodium dihydrogen phosphate solution, and sodium hydroxide solution. Then put 32 - 46 mL of oleic acid into a container, successively add 40 - 60 mL of ethanol and 24 - 36 mL of sodium hydroxide solution, and stir for 15 - 30 min; 2) Then continue to successively add 24 - 36 mL of calcium chloride solution and 24 - 36 mL of sodium dihydrogen phosphate solution, as well as 5 - 8 g of porous nanosheet material. After ultrasonic dispersion at 200 - 300 W for 1 - 2 h, transfer it to a high - pressure reaction kettle. Under mechanical stirring at 500 - 800 r / min, perform hydrothermal reaction at 180 - 186 °C for 24 - 27 h. After the reaction ends, add 1 - 3 g of spiky nanoparticles, stir mechanically at 1000 - 1500 r / min for 1 - 2 h, and perform ultrasonic treatment at 500 - 800 W for 1 - 2 h. After the treatment ends, take the sediment product, wash it repeatedly with ethanol and deionized water, and then dry it to obtain the composite nanomaterial.

8. A composite microbial inoculant containing specific active ingredients of bamboo according to claim 7, characterized in that, For the porous nanosheet material, using sodium dodecyl sulfate as a soft template agent, after the aging reaction of mixing zinc acetate, 2 - methylimidazole, and sodium dodecyl sulfate at room temperature, wash the template agent away with a solvent to synthesize the porous nanosheet material.

9. A composite microbial inoculant containing specific active ingredients of bamboo according to claim 7, characterized in that, The described spiky nanoparticles are synthesized by using chloroauric acid as a raw material and adopting the seed growth method to obtain nanoparticles with a short rod structure. Taking the nanoparticles with the short rod structure as seeds, cetyltrimethylammonium chloride is used to accelerate the anisotropic growth of the particles, thereby obtaining spiky nanoparticles.

10. Use of the composite microbial inoculant according to any one of claims 1-9 in repairing soil heavy metal pollution and increasing crop yield, characterized in that, The described application method is as follows: Spraying the compound microbial inoculum in the farmland, transplanting the crops 12 - 15 days later, and the spraying amount is 25 - 32 kg / mu.

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