Preparation process of porous activated carbon soil conditioner loaded with microbial flora

Abstract

The invention relates to the technical field of soil improvement and microorganisms, and discloses a preparation process of a porous activated carbon soil conditioner loaded with microbial flora, which comprises the following steps: firstly, performing high-temperature activation and acid-base modification on a biomass raw material to prepare a porous activated carbon carrier, and dipping in a nutrient solution to preset a slow-release nutrient substrate; secondly, adopting a step-by-step sequential loading process, firstly loading the bacillus subtilis subjected to stress resistance domestication on a carrier through electrostatic adsorption, and performing activation colonization culture to form a stable pioneer biological membrane; then, on the basis of the biological membrane, phosphate solubilizing bacteria, potassium solubilizing bacteria and antagonistic bacteria are loaded in sequence; finally, the loaded composite carrier is subjected to microcapsule embedding and low-temperature drying treatment, and the porous activated carbon soil conditioner is obtained. According to the modifier prepared by the invention, through ordered loading and multiple protection, the problem of strain competition is solved, the high survival rate of flora is ensured, and the improvement effect is stable and long-acting.

Description

Technical Field

[0001] This invention relates to the fields of soil improvement and microbial technology, specifically to the preparation process of porous activated carbon soil conditioner loaded with microbial communities. Background Technology

[0002] With the intensive development of modern agriculture, degradation problems such as soil salinization, compaction, nutrient imbalance and pollutant accumulation have constrained agricultural production.

[0003] To address soil degradation, current technologies often employ physical or biological methods. Physical methods include applying porous materials such as activated carbon to improve soil structure through their adsorption properties; biological methods involve applying microbial agents to activate nutrients and suppress diseases. To combine the advantages of both approaches, composite soil conditioners that load microorganisms onto porous carriers have begun to emerge and are being used.

[0004] However, existing composite improvers are relatively simple to prepare, generally involving a one-time blending of multiple bacterial strains with a carrier. This method leads to disordered competition among strains for attachment sites, making it difficult to form a stable synergistic community. Furthermore, the weak binding affinity between the strains and the carrier results in low viable cell survival rates in practical applications, unstable and unsustainable improvement effects, and failure to fully leverage the synergistic effect between the carrier and the microorganisms.

[0005] Therefore, this invention proposes a process for preparing porous activated carbon soil conditioner loaded with microbial communities to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a process for preparing porous activated carbon soil conditioner loaded with microbial communities. This process solves the problem that existing composite conditioners, due to their simple blending process, result in unstable microbial community structures, weak bonding with the carrier, and low survival rates, leading to poor and unsustainable improvement effects in the final product.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a process for preparing porous activated carbon soil conditioner loaded with microbial communities, comprising the following steps: S1. Prepare porous activated carbon carrier by high-temperature activation and acid-base modification of biomass raw materials; S2. The porous activated carbon carrier is immersed in a nutrient solution and dried to form a pretreated carrier containing a slow-release nutrient substrate. S3. Each strain that makes up the complex microbial community is subjected to stress resistance domestication culture to obtain a variety of domesticated strains; S4. Prepare bacterial suspensions from the various domesticated bacterial strains respectively, and electrostatically adsorb and load the pretreated carrier onto the various bacterial suspensions in sequence. The pretreated carrier is first loaded with Bacillus subtilis and activated and colonized, and then the pretreated carrier is loaded with phosphate-solubilizing bacteria, potassium-solubilizing bacteria and antagonistic bacteria in sequence. S5. The loaded carrier is microencapsulated and dried at low temperature to obtain porous activated carbon soil conditioner. The process of this invention first involves high-temperature activation and acid-base modification of biomass raw materials to prepare a porous activated carbon carrier. The purpose of this step is to construct a rich internal pore structure through high-temperature activation to provide a physical habitat for microorganisms. Subsequent acid-base modification introduces specific oxygen-containing functional groups onto the carrier surface. The introduction of these functional groups alters the chemical properties of the carrier surface, enabling it to exhibit a stable surface charge under specific pH conditions. This is the technical basis for achieving subsequent high-efficiency loading.

[0008] Subsequently, the porous activated Tanshu carbon carrier is impregnated in a nutrient solution and dried to form a pretreated carrier containing a slow-release nutrient substrate. This step involves pre-loading nutrients into the pores of the carrier. In this way, once microorganisms are loaded, they can continuously obtain the basic substances needed for growth from this nutrient substrate. This method provides a favorable microenvironment for the initial colonization of microorganisms and their long-term survival in the soil, helping to improve their environmental adaptability.

[0009] Regarding microbial strains, this process involves separately acclimatizing each strain that makes up the composite microbial community to obtain multiple acclimatized strains. This step utilizes a separate acclimatization method, which avoids competition between different strains due to differences in growth rate, nutritional requirements, etc., during co-cultivation. This helps ensure that each strain retains its intended functional characteristics after acclimatization, providing a high-quality source of strains for the subsequent construction of a functionally balanced composite microbial community.

[0010] A key feature of this process is that after preparing the domesticated bacterial strains into bacterial suspensions, they are loaded using a sequential electrostatic adsorption method. This process is not a one-time mixed adsorption, but rather a step-by-step process: first, Bacillus subtilis is loaded, and a separate activation and colonization stage is established for it; then, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria are loaded sequentially. The key is that by adjusting the pH value, the carrier and the bacterial surface are given opposite charges, and a strong bond is achieved through electrostatic attraction between them. Furthermore, the initial loading and activation of Bacillus subtilis allows for the formation of a biofilm on the carrier surface. This biofilm provides a more favorable interface for the subsequent attachment of functional bacterial strains, facilitating the orderly coexistence of multiple bacterial species on the carrier.

[0011] Finally, the loaded carrier is microencapsulated and cryogenically dried. This step aims to protect the carrier loaded with microorganisms. Microencapsulation forms a physical barrier around the carrier, mitigating the impact of external environmental factors on the internal microorganisms. The subsequent cryogenic drying process removes moisture while maintaining the integrity of the microbial cell structure, inducing a dormant state, which helps improve the product's storage stability and shelf life.

[0012] Preferably, the biomass raw material is selected from at least one of coconut shells, straw, or fruit shells.

[0013] These materials, as common lignocellulosic biomass, possess a naturally porous structure and high carbon content. This characteristic allows them to readily form a carbonaceous skeleton with a high specific surface area and abundant porosity after high-temperature activation, providing physical space for microbial habitation and colonization. Simultaneously, their chemical composition provides a reaction basis for subsequent acid-base modification steps, facilitating the generation of oxygen-containing functional groups necessary for electrostatic adsorption on the carrier surface.

[0014] Preferably, step S2 includes: The porous activated carbon carrier was immersed in a nutrient solution for 30 to 60 minutes under a negative pressure of -0.05 MPa to -0.09 MPa. After impregnation, the substrate is dried at 60–85°C to form the pretreated carrier containing the slow-release nutrient substrate.

[0015] The negative pressure range of -0.05MPa to -0.09MPa aims to establish an effective pressure difference between the inside and outside of the carrier, overcoming the capillary resistance of the nutrient solution in the microporous structure, expelling air from the pores, and allowing the nutrient solution to fully penetrate deep into the carrier. The impregnation time of 30–60 minutes ensures sufficient time for the penetration process to complete under the set negative pressure. After impregnation, drying is carried out at 60–85°C. This temperature range ensures effective evaporation of moisture while avoiding the decomposition or denaturation of organic components in the nutrient solution due to excessively high temperatures. Ultimately, the nutrients are stably attached to the inner wall of the carrier pores in a solid form, forming the pretreated carrier containing the slow-release nutrient substrate.

[0016] Preferably, the nutrient solution includes 0.5-5.0% by mass of oligochitosan and 0.01-0.1% by mass of a complex of trace elements, including zinc sulfate, boric acid and sodium molybdate.

[0017] Oligochitosan, as a slow-release carbon and nitrogen source that can be utilized by microorganisms, is set at a mass concentration in the range of 0.5%–5.0% to provide sufficient and continuous basic nutrients for the initial colonization and subsequent growth of microorganisms. Meanwhile, the aforementioned complex trace elements are components or activators of many key metabolic enzymes in microorganisms, indispensable for their life activities. Controlling their mass concentration in a low range of 0.01%–0.1% satisfies the metabolic needs of microorganisms while avoiding the inhibitory effects that might occur due to excessively high local concentrations. Together, these elements construct a balanced nutritional support system for the loaded microorganisms. Zinc sulfate provides zinc, which is an activator of various enzymes; boron provided by boric acid participates in cellular metabolic activities; and molybdenum provided by sodium molybdate is a core component of key enzymes in nitrogen fixation and nitrate reduction processes.

[0018] Preferably, step S3 includes: The composite microbial community was subjected to salt stress acclimatization. The composite microbial community, by weight, included the following components: Bacillus subtilis: 30-50 parts; Phosphate-solubilizing bacteria: 20-40 parts; Potassium-solubilizing bacteria: 15-30 parts; Antagonistic bacteria: 5-15 parts. Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria were cultured stepwise in culture media with sodium chloride concentrations of 0.5%, 1.0%, 1.5%, and 2.0%, respectively, with each stage lasting 24–48 hours, to obtain various domesticated strains of Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria.

[0019] The complex microbial community, by weight, includes 30–50 parts of Bacillus subtilis, 20–40 parts of phosphate-solubilizing bacteria, 15–30 parts of potassium-solubilizing bacteria, and 5–15 parts of antagonistic bacteria. This formulation aims to create a complementary micro-ecosystem, where Bacillus subtilis, as the dominant species, provides a growth foundation for other functional bacteria through its strong colonization and film-forming abilities; phosphate-solubilizing and potassium-solubilizing bacteria are responsible for improving soil nutrient availability; and antagonistic bacteria play a role in biocontrol.

[0020] The key technical feature of this step is the sequential cultivation of Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria in culture media with sodium chloride concentrations of 0.5%, 1.0%, 1.5%, and 2.0%, respectively. Separate cultivation avoids growth competition among different microorganisms under stress, ensuring that each strain can independently complete its adaptive evolution to salt stress without interference, thus preserving its functional characteristics to the greatest extent. The acclimatization method of progressively increasing sodium chloride concentration applies gradually increasing selection pressure to the strains. This is a gentle induction screening process that effectively selects strains with strong salt tolerance while avoiding the mass mortality that might result from a single high-concentration salt shock. Each cultivation stage lasts 24–48 hours. This time range is set to ensure that the strains have sufficient time to grow and reproduce at each salt concentration gradient, allowing the salt tolerance trait to be stably inherited, ultimately obtaining a variety of highly stress-tolerant acclimatized strains suitable for subsequent loads.

[0021] Preferably, step S4 includes: The various domesticated bacterial strains of Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria obtained in step S3 were collected by centrifugation, washed with sterile buffer, and resuspended to prepare a concentration of 10. 8 ~10 9 Corresponding bacterial suspensions with CFU / mL; The pretreated carrier is suspended in sterile water to form a pretreated carrier suspension. The first electrostatic adsorption loading process includes the following steps: The pH of the pretreated carrier suspension was adjusted to 6.0–9.0, at which the surface Zeta potential of the pretreated carrier was -20 mV to -50 mV; the pH of the Bacillus subtilis suspension was adjusted to 2.0–4.0, at which the surface Zeta potential of the Bacillus subtilis was +15 mV to +40 mV; the pretreated carrier suspension and the Bacillus subtilis suspension were mixed and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C. The carrier that has completed the first electrostatic adsorption loading is cultured at 30-37℃ for 12-24 hours to activate and colonize it. The second electrostatic adsorption loading process includes the following steps: The pH of the phosphate-solubilizing bacteria suspension was adjusted to 2.0–4.0. At the pH of 2.0–4.0, the surface Zeta potential of the phosphate-solubilizing bacteria was +15mV to +40mV. The activated and colonized carrier was mixed with the phosphate-solubilizing bacteria suspension and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C. The third electrostatic adsorption loading process includes the following steps: The pH of the potassium-solubilizing bacteria suspension was adjusted to 2.0–4.0. At the pH of 2.0–4.0, the surface zeta potential of the potassium-solubilizing bacteria was +15mV to +40mV. The carrier that had completed the second electrostatic adsorption loading was mixed with the potassium-solubilizing bacteria suspension and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C. The fourth electrostatic adsorption loading process includes the following steps: The pH of the antagonistic bacterial suspension was adjusted to 2.0–4.0, at which the surface zeta potential of the antagonistic bacteria was +15mV to +40mV. The carrier that had completed the third electrostatic adsorption loading was mixed with the antagonistic bacterial suspension and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C.

[0022] The microbial loading step in S4 employs a step-by-step, sequential electrostatic adsorption process. First, various domesticated bacterial strains, including Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria obtained in S3, are collected by centrifugation, washed and resuspended in sterile buffer, and prepared into concentrations of 10... 8 ~10 9 The corresponding bacterial suspension was prepared at CFU / mL. This concentration range was set to ensure a sufficient number of viable bacteria participated in the loading process to achieve an effective loading density. Simultaneously, the pretreated carrier was suspended in sterile water to form a pretreated carrier suspension.

[0023] The core of this process lies in the initial electrostatic adsorption loading and subsequent activation and colonization. The steps are as follows: The pH of the pretreated carrier suspension is adjusted to 6.0–9.0. Under this pH condition, the oxygen-containing functional groups on the carrier surface dissociate, resulting in a stable negative zeta potential of -20mV to -50mV. Simultaneously, the pH of the Bacillus subtilis suspension is adjusted to an acidic environment of 2.0–4.0. Under this condition, the amino groups on the surface of the bacterial cell wall are protonated, resulting in a stable positive zeta potential of +15mV to +40mV. The two are then mixed and stirred at 25–35°C and 100–150 rpm for 1–2 hours. The key is that by precisely controlling the pH to generate opposite zeta potentials, a strong electrostatic attraction is formed between the carrier and the bacteria, achieving efficient and robust adsorption. The set mild stirring conditions ensure sufficient contact between the two while avoiding mechanical damage to the bacteria.

[0024] After the initial loading, this process includes a crucial activation and colonization step: culturing the Bacillus subtilis-loaded vector at 30–37°C for 12–24 hours. This step leverages the ease with which Bacillus subtilis, as a "pioneer strain," grows and forms biofilms, providing it with a unique and suitable growth window. During this period, Bacillus subtilis not only colonizes more firmly within the vector pores, but more importantly, it germinates and secretes extracellular polymers such as polysaccharides, forming a biofilm on the vector surface. This biofilm provides a more biocompatible attachment interface for subsequent loading of other functional strains.

[0025] Building upon this biofilm, subsequent bacterial strains are loaded sequentially. The second electrostatic adsorption loading involves adjusting the pH of the phosphate-solubilizing bacterial suspension to 2.0–4.0 (resulting in a surface zeta potential of +15 mV to +40 mV) and mixing it with the activated and colonized carrier. Similarly, the third loading of potassium-solubilizing bacteria and the fourth loading of antagonistic bacteria follow the same procedure: adjusting the pH of their respective bacterial suspensions to 2.0–4.0 and then mixing them with the carrier from the previous loading step. This series of stepwise loadings utilizes the established biofilm interface and continuous electrostatic attraction to load different functional bacterial strains onto the carrier in a stratified and orderly manner, constructing a structurally stable and functionally synergistic complex microbial community. This avoids the problems of competitive adsorption and uneven distribution among strains caused by single-stage mixing loading.

[0026] Preferably, step S5 includes: Microcapsule encapsulation was performed by mixing the loaded carrier with a sodium alginate solution with a mass concentration of 1.0–3.0%, and then dropping the mixture into a calcium chloride solution with a mass concentration of 2.0–5.0% for cross-linking and encapsulation. Subsequently, a low-temperature drying process is carried out. The embedded carrier is first pre-frozen at -40℃ to -60℃ for 8 to 12 hours, and then sublimation drying is carried out under a vacuum of 10 to 30 Pa to obtain the porous activated carbon soil conditioner.

[0027] The first step involves microencapsulation, specifically: the loaded carrier is mixed with a 1.0–3.0% sodium alginate solution, and then this mixture is dropped into a 2.0–5.0% calcium chloride solution for cross-linking and encapsulation. This process utilizes the sodium alginate solution to encapsulate the carrier loaded with microorganisms. When the calcium chloride solution is added, divalent calcium ions rapidly replace the monovalent sodium ions in the sodium alginate, undergoing an ionic cross-linking reaction with the alginate molecular chains to form a water-insoluble calcium alginate gel with a network structure. The 1.0–3.0% sodium alginate concentration and the 2.0–5.0% calcium chloride concentration are matched to create a physical barrier of suitable thickness and strength. This barrier protects the internal microorganisms from external environmental stresses while maintaining a certain degree of permeability, facilitating their recovery in the soil.

[0028] Following this, a low-temperature drying process is performed. This process begins by pre-freezing the embedded carrier at -40℃ to -60℃ for 8–12 hours. This deep pre-freezing step aims to rapidly cool the carrier and gel packaging material, causing the moisture inside to form tiny ice crystals, thus preventing large ice crystals from causing irreversible physical damage to the microbial cell structure. After pre-freezing, sublimation drying is carried out under a vacuum of 10–30 Pa. Under this high vacuum environment, the solid ice in the material can be directly sublimated into water vapor and removed without passing through a liquid state. This sublimation drying process removes moisture without damaging the integrity of the microbial cell structure, inducing a dormant state, thereby obtaining a final stable, easily stored, and transportable porous activated carbon soil conditioner.

[0029] This invention provides a process for preparing porous activated carbon soil conditioner loaded with microbial communities. It has the following beneficial effects: 1. This invention utilizes a specific high-temperature activation and modification process to prepare an activated carbon carrier with a customized pore structure, providing an excellent physical basis for the growth and attachment of microorganisms. Furthermore, this invention employs a stepwise loading and activation colonization construction method, first introducing pioneer strains to form a stable biofilm, and then sequentially loading various functional bacteria. This ordered construction method effectively avoids direct competition between strains, significantly improving the attachment stability and survival rate of the entire microbial community on the carrier, laying a solid structural and biological foundation for the long-term effectiveness of the soil conditioner.

[0030] 2. This invention efficiently combines the physical adsorption capacity of the carrier with the biodegradation function of microorganisms. The three-dimensional porous network structure of activated carbon itself can effectively adsorb and fix pollutants such as heavy metals and pesticide residues in the soil, reducing their biotoxicity. At the same time, the functional microbial community that stabilizes the load, such as antagonistic bacteria, can inhibit the growth of soil-borne pathogens through metabolic activities or competitive interactions. This synergistic mechanism of "physical solidification" and "biological purification" achieves dual treatment of chemical and biological pollution in the soil, resulting in a more comprehensive and thorough effect.

[0031] 3. This invention focuses on comprehensive ecological restoration of soil and sustainable improvement of soil fertility. The beneficial microorganisms loaded in the product, such as those that solubilize phosphorus and potassium, continuously convert insoluble nutrients fixed in the soil into forms that can be absorbed by plants, thereby activating the soil's potential fertility. Furthermore, the porous nature of activated carbon combined with polysaccharides produced by microbial metabolism effectively promotes the formation of soil aggregates and improves soil aeration and water retention. This comprehensive approach, integrating pollution control, fertility enhancement, and structural improvement, achieves a positive reconstruction of the soil ecosystem. Attached Figure Description

[0032] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] To better understand the present invention, the above content will be described in detail below with reference to specific embodiments.

[0035] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0036] Please see the attached Figure 1 .

[0037] S1. Preparation of porous activated carbon support: Dried coconut shells were crushed and screened through a vibrating sieve to obtain particles with a diameter of 40 mesh. The screened particles were placed in a tube furnace and heated to 700°C under an oxygen-free atmosphere protected by nitrogen. Then, steam was introduced for high-temperature activation treatment for 45 minutes, followed by natural cooling to obtain the activated product. This activated product was then immersed in a 1.2 mol / L hydrochloric acid solution and reacted with stirring in a 70°C water bath for 4 hours. After the reaction, the product was repeatedly washed with deionized water until the pH of the filtrate was neutral, and then dried in an oven at 105°C to obtain a porous activated carbon carrier with a well-developed pore structure.

[0038] S2. Preparation of the pretreated carrier: A nutrient solution was prepared, containing 2.5% (w / w) of oligochitosan and 0.05% (w / w) of a complex of trace elements (zinc sulfate, boric acid, and sodium molybdate mixed in a 1:1:1 mass ratio). The porous activated carbon carrier obtained in step S1 was placed in a vacuum impregnation tank, and a vacuum was drawn to -0.07 MPa. Under this negative pressure condition, the carrier was impregnated in the above nutrient solution for 45 minutes. After impregnation, the carrier was removed and dried with hot air at 75°C until constant weight was achieved, forming a pretreated carrier containing a slow-release nutrient substrate.

[0039] S3. Domestication of the stress resistance of complex microbial communities: By weight, 40 parts of Bacillus subtilis, 30 parts of phosphate-solubilizing bacteria, 23 parts of potassium-solubilizing bacteria, and 10 parts of antagonistic bacteria were taken. These four bacterial strains were inoculated separately into basal liquid culture medium. Subsequently, sodium chloride was added to the culture medium to create a gradient stress environment with mass concentrations of 0.5%, 1.0%, 1.5%, and 2.0%, respectively. At each sodium chloride concentration, each bacterial strain was cultured for 36 hours in a shaker at 30°C and 150 rpm, and then transferred to a higher salt concentration culture medium to complete the stepwise salt stress acclimatization, obtaining multiple acclimatized bacterial strains with enhanced salt tolerance.

[0040] S4. Step-by-step electrostatic adsorption of loads: The various domesticated bacterial strains obtained in S3 were collected by centrifugation (8000 rpm, 10 min), washed twice with sterile phosphate buffer, and resuspended to prepare a concentration of approximately 5 × 10⁻⁶. 8The corresponding bacterial suspensions at CFU / mL were prepared. The pretreated carrier obtained in S2 was suspended in sterile water. First, the first loading was performed: the pH of the carrier suspension was adjusted to 7.5, at which point its surface zeta potential was approximately -35 mV; simultaneously, the pH of the Bacillus subtilis suspension was adjusted to 3.0, at which point its surface zeta potential was approximately +25 mV. The two were mixed and stirred at 30°C and 120 rpm for 1.5 hours for adsorption. After adsorption, the carrier loaded with Bacillus subtilis was incubated at 35°C for 18 hours for activation and colonization. Subsequently, the second, third, and fourth loading were performed sequentially. The pH of the suspensions of phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria was adjusted to 3.0, respectively, to make their surfaces positively charged, and then added sequentially to the carrier suspensions that had undergone the previous activation or loading step, each time stirred and adsorbed for 1.5 hours at 30°C and 120 rpm.

[0041] S5, Microencapsulation and Low-Temperature Drying: The carriers from step S4, with all bacterial strains loaded, were uniformly mixed with a 2.0% sodium alginate solution. This mixture was then slowly dripped into a 3.5% calcium chloride solution using a peristaltic pump, and allowed to stand for 30 minutes to solidify, forming gel microcapsules. The microcapsules were then removed, rinsed with sterile water, and pre-frozen at -50°C for 10 hours. Finally, the pre-frozen samples were placed in a vacuum freeze dryer and sublimated at a vacuum of 20 Pa for 24 hours to obtain porous activated carbon soil conditioner.

[0042] Example 2: S1. Preparation of Porous Activated Carbon Support: Agricultural waste straw was crushed, and particles with a diameter of 60 mesh were screened out. The particles were heated to 600℃ in an anaerobic atmosphere and activated by passing carbon dioxide through them to obtain an activated product. The product was immersed in a 0.5 mol / L sodium hydroxide solution and reacted at 60℃ for 2 hours. After the reaction was completed, the product was washed until neutral and dried to obtain a porous activated carbon support.

[0043] S2. Preparation of the pretreated carrier: Prepare a nutrient solution containing 0.5% (w / w) of oligochitosan and 0.01% (w / w) of zinc sulfate. Immerse the carrier from S1 in the nutrient solution for 30 minutes under a negative pressure of -0.05 MPa, and then dry it at 60°C to form the pretreated carrier.

[0044] S3. The stress resistance acclimatization of the complex microbial community was carried out by mass fractions: 30 parts of Bacillus subtilis, 20 parts of phosphate-solubilizing bacteria, 15 parts of potassium-solubilizing bacteria, and 5 parts of antagonistic bacteria. Each strain was cultured sequentially in media with sodium chloride concentrations of 0.5%, 1.0%, 1.5%, and 2.0%, with each stage lasting 24 hours, to complete the acclimatization process.

[0045] S4. The domesticated bacterial strains from S3 were prepared in steps by electrostatic adsorption loading to obtain concentrations of 1×10⁻⁶. 8 CFU / mL bacterial suspension. For the first loading: adjust the pH of the pretreated carrier suspension to 6.0 (surface zeta potential approximately -20 mV), and adjust the pH of the Bacillus subtilis suspension to 4.0 (surface zeta potential approximately +15 mV). Mix the two and stir at 25°C and 100 rpm for 1 hour. After completion, incubate the carrier at 30°C for 12 hours for activation and colonization. Subsequently, adjust the pH of the suspensions of phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria to 4.0 sequentially, and load them sequentially, each time stirring at 25°C and 100 rpm for 1 hour.

[0046] S5. Microencapsulation and Low-Temperature Drying: The loaded carrier was mixed with a 1.0% sodium alginate solution and then added dropwise to a 2.0% calcium chloride solution for cross-linking and embedding. The embedded carrier was pre-frozen at -40℃ for 8 hours and then sublimated and dried under a vacuum of 30 Pa to obtain porous activated carbon soil conditioner.

[0047] Example 3: S1. Preparation of Porous Activated Carbon Support: Waste fruit shells were crushed, and particles with a diameter of 20 mesh were screened out. The particles were heated to 800℃ under an oxygen-free atmosphere and activated by passing steam through them to obtain an activated product. The product was immersed in a 2.0 mol / L hydrochloric acid solution and reacted at 80℃ for 6 hours. After the reaction was completed, the product was washed until neutral and dried to obtain a porous activated carbon support.

[0048] S2. Preparation of the pretreated carrier: Prepare a nutrient solution containing 5.0% (w / w) of oligochitosan and 0.1% (w / w) of a complex of trace elements (zinc sulfate, boric acid, sodium molybdate). Immerse the carrier from S1 in the nutrient solution for 60 minutes under a negative pressure of -0.09 MPa, and then dry it at 85°C to form the pretreated carrier.

[0049] S3. The stress resistance acclimatization of the complex microbial community was carried out by weight-based fractionation: 50 parts of Bacillus subtilis, 40 parts of phosphate-solubilizing bacteria, 30 parts of potassium-solubilizing bacteria, and 15 parts of antagonistic bacteria. Each strain was cultured sequentially in media with sodium chloride concentrations of 0.5%, 1.0%, 1.5%, and 2.0%, with each stage lasting 48 hours, to complete the acclimatization process.

[0050] S4. The domesticated bacterial strains from S3 were prepared in steps by electrostatic adsorption loading to obtain concentrations of 1×10⁻⁶. 9CFU / mL bacterial suspension. For the first loading: adjust the pH of the pretreated carrier suspension to 9.0 (surface zeta potential approximately -50 mV), and adjust the pH of the Bacillus subtilis suspension to 2.0 (surface zeta potential approximately +40 mV). Mix the two and stir at 35°C and 150 rpm for 2 hours. After completion, incubate the carrier at 37°C for 24 hours for activation and colonization. Subsequently, adjust the pH of the suspensions of phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria to 2.0 sequentially, and load them sequentially, each time stirring at 35°C and 150 rpm for 2 hours.

[0051] S5. Microencapsulation and Low-Temperature Drying: The loaded carrier was mixed with a 3.0% sodium alginate solution and then added dropwise to a 5.0% calcium chloride solution for cross-linking and embedding. The embedded carrier was pre-frozen at -60℃ for 12 hours and then sublimated and dried under a vacuum of 10 Pa to obtain porous activated carbon soil conditioner.

[0052] Comparative Example 1: The difference between this example and Example 1 lies in the microbial loading method in step S4. In this comparative example, equal volumes of four bacterial suspensions—Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria—obtained through S3 in Example 1 were pre-mixed. The pH of this mixed bacterial suspension was then adjusted to 3.0, and a single-stage adsorption loading was performed with a pretreated carrier suspension at pH 7.5. The loading conditions (30°C, 120 rpm, 1.5 hours) were the same as in Example 1 for a single loading, without the intermediate activation and colonization step. All other steps were the same as in Example 1.

[0053] Comparative Example 2: The difference compared to Example 1 lies in the loading process of step S4. Although this comparative example also uses stepwise loading, the "activation and colonization" step after the first loading of Bacillus subtilis is omitted. That is, after the adsorption of Bacillus subtilis is completed, the subsequent electrostatic adsorption loading of phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria is carried out directly without 18 hours of incubation. The remaining steps are the same as in Example 1. Comparative Example 3: Compared to Example 1, the difference lies in the omission of step S2. This comparative example directly uses the porous activated carbon carrier prepared in step S1 (without nutrient solution impregnation) for subsequent steps S3 and S4, meaning the carrier itself does not contain a pre-placed slow-release nutrient substrate. The remaining steps are the same as in Example 1.

[0054] Comparative Example 4: Compared to Example 1, the difference lies in omitting the microcapsule encapsulation step S5. In this comparative example, the vectors for which all bacterial strains were loaded in step S4 were directly subjected to low-temperature drying (pre-freezing at -50°C for 10 hours, followed by vacuum sublimation drying at 20 Pa), without cross-linking encapsulation with sodium alginate and calcium chloride. The remaining steps were the same as in Example 1.

[0055] Test Example 1: Experimental Materials and Grouping Test product: Group A (Example 1): Modifier prepared using the process of Example 1.

[0056] Group B (Comparative Example 1): Modifier prepared using the process of Comparative Example 1.

[0057] Group C (Comparative Example 2): Modifier prepared using the process of Comparative Example 2.

[0058] Group D (Comparative Example 3): Modifier prepared using the process of Comparative Example 3.

[0059] Group E (Comparative Example 4): Modifier prepared using the process of Comparative Example 4.

[0060] Control group: CK group (blank control): No exogenous modifiers were applied, and the same routine management as the experimental group was performed.

[0061] Tested soils and crops: Scenario 1: Soil 1 (saline-alkali land, initial pH≈8.5, total salt content≈1.26g / kg, yield decrease of 30%), the test crop is maize.

[0062] Scenario 2: Soil 2 (greenhouse, continuous cropping for 10 years, soil-borne disease (wilt) incidence rate >60%, yield decrease of 30%), the test crop is tomato.

[0063] Experimental steps Scenario 1: Soil Improvement Experiment (Saline-Alkali Land) Site preparation and sampling: Representative saline-alkali land with uniform soil fertility was selected and divided into 18 experimental plots of equal area. These plots were randomly assigned to six treatment groups (A, B, C, D, E, and CK), with three replicates per group. Before applying the soil amendment, soil samples from the topsoil layer (0-20cm) of each plot were collected according to specifications, mixed thoroughly, and used to determine the initial soil physicochemical properties to confirm that they met the "current soil condition".

[0064] Soil amendment application: According to the "Application Plan", apply the five groups of products (A, B, C, D, and E) at a rate of 200 kg per acre, evenly to the surface of the corresponding plot. Then, use a rotary tiller to turn the soil amendment into the soil to a depth of 15-20 cm. The CK group plot should be tilled under the same conditions.

[0065] Field management: All plots are sown in a unified manner, and are coordinated with consistent irrigation and drainage management, routine fertilization and pest and disease control.

[0066] Data Collection and Analysis: Three months after processing, soil samples were collected again from each plot to test and record soil pH, salinity, and porosity. After the corn matured, actual yield measurements were taken from each plot and converted to yield per acre.

[0067] Scenario 2: Soil Remediation Experiment (Continuous Cropping Greenhouse) Site preparation and sampling: In a greenhouse with severe continuous cropping obstacles, 18 independent planting areas were set up and randomly assigned to six treatment groups: A, B, C, D, E and CK, with 3 replicates per group.

[0068] Application of soil conditioner: According to the "Application Plan", apply 5 kg of products (groups A, B, C, D, and E) per cubic meter of soil and mix thoroughly with the soil in the corresponding planting area.

[0069] Cultivation Management: All planting areas underwent uniform high-temperature fumigation treatment. After fumigation, tomato seedlings with uniform growth were transplanted. Subsequent cultivation management measures remained completely consistent across all treatment groups.

[0070] Data Collection and Analysis: After a complete growing season, the incidence rate (%) of Fusarium wilt and the continuous cropping obstacle index were calculated for each region. After the tomato harvest season, the total yield for each region was calculated. During the peak fruiting period, tomato fruits of uniform maturity were randomly harvested, and their vitamin C content was measured.

[0071] Experimental results (see Table 1 and Table 2): Table 1: Comparison of Soil Improvement Effects (Saline-Alkali Land) Group Soil pH value (after improvement) Total salt content (g / kg) (after improvement) Soil porosity (%) (after improvement) Corn yield (kg / mu) CK group (blank control) 8.51 1.26 13.1 350 Group B (Comparative Example 1) 8.3 1.05 15.2 375 Group D (Comparative Example 3) 8.21 0.97 16.9 388 Group E (Comparative Example 4) 8.14 0.88 17.6 402 Group C (Comparative Example 2) 8.02 0.74 19.5 425 Group A (Example 1) 7.8 0.6 22 450 Table 2: Comparison of Soil Remediation Effects in Continuous Cropping Greenhouses Group Continuous cropping obstacle index (improved) Fusarium wilt incidence (%) Tomato yield (recovery status) Vitamin C content (mg / 100g) CK group (blank control) 72 62 Production decreased by 30% 20.3 Group B (Comparative Example 1) 61 51 Production has rebounded slightly. 21.2 Group D (Comparative Example 3) 54 43 Production partially recovered 22 Group E (Comparative Example 4) 49 36 Production has recovered significantly 22.7 Group C (Comparative Example 2) 41 29 Production recovered significantly 23.5 Group A (Example 1) 28 15 Restored to pre-continuous cropping levels 24.4 The comprehensive experimental data in Tables 1 and 2 clearly demonstrate that the soil conditioner (Group A) prepared using the complete process of this invention is significantly superior to the comparative groups (Groups B, C, D, and E) and the blank control group (CK) in both saline-alkali land improvement and continuous cropping obstacle repair scenarios. Group A not only exhibits strong physical improvement capabilities, such as significantly reducing soil pH and total salinity and increasing soil porosity (thanks to the superior physical adsorption properties of the porous activated carbon carrier and its synergistic effect with microbial metabolites (such as polysaccharides) on soil aggregate structure), but also demonstrates excellent performance at the biological level, significantly improving crop yield and quality by effectively reducing the incidence of Fusarium wilt and the continuous cropping obstacle index. This fully proves the effectiveness of the "carrier-microbe-soil" synergistic mechanism constructed in this invention.

[0072] The technical advantage of this invention lies in its unique preparation process. By comparing the effects of group A with groups B and C, it can be seen that the step-by-step loading and activation colonization process employed in this invention is key to ensuring the efficient synergy of functional microorganisms. Simple mixed loading (group B) or omitting the activation step (group C) cannot construct a structurally stable and functionally coordinated microbial community, resulting in a significant reduction in its ability to inhibit pathogen reproduction (biodegradation) and decompose insoluble minerals to improve fertility (fertility enhancement). This invention, through an ordered method of electrostatic adsorption, ensures stable loading and high survival rate of functional microbial communities, enabling them to rapidly form a dominant population after entering the soil and perform their intended biological functions.

[0073] Furthermore, comparing the results of group A with groups D and E further confirms the necessity of the carrier pretreatment and finished product protection processes. Pre-positioning the carrier with a slow-release nutrient medium (compared to group D) provides the loaded microorganisms with initial "food" in the harsh soil environment, ensuring their rapid colonization and effectiveness. The final microencapsulation process (compared to group E) provides a robust physical barrier for this intricately constructed micro-ecosystem, effectively resisting external environmental stresses and ensuring the product maintains high biological activity during application. It is this complete technological chain, from carrier customization and microbial community construction to finished product protection, that is interconnected and collectively ensures that the product of this invention can achieve stable and comprehensive improvement effects in practical applications.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing porous activated carbon soil conditioner loaded with microbial communities, characterized in that, Includes the following steps: S1. Prepare porous activated carbon carrier by high-temperature activation and acid-base modification of biomass raw materials; S2. The porous activated carbon carrier is immersed in a nutrient solution and dried to form a pretreated carrier containing a slow-release nutrient substrate. S3. Each strain that makes up the complex microbial community is subjected to stress resistance domestication culture to obtain a variety of domesticated strains; S4. Prepare bacterial suspensions from the various domesticated bacterial strains respectively, and electrostatically adsorb and load the pretreated carrier onto the various bacterial suspensions in sequence. The pretreated carrier is first loaded with Bacillus subtilis and activated and colonized, and then the pretreated carrier is loaded with phosphate-solubilizing bacteria, potassium-solubilizing bacteria and antagonistic bacteria in sequence. S5. The loaded carrier is microencapsulated and dried at low temperature to obtain porous activated carbon soil conditioner.

2. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 1, characterized in that, The steps in S1 include: Pre-treatment of biomass raw materials involves crushing and screening the biomass raw materials to obtain particles with a particle size of 20-60 mesh. The particles are activated at high temperature by treating them in an oxygen-free atmosphere at 600–800°C with steam or carbon dioxide to obtain the activated product. The activated product is subjected to acid-base modification treatment by immersing it in a 0.5-2.0 mol / L hydrochloric acid solution or sodium hydroxide solution and reacting it at 60-80°C for 2-6 hours. It is then washed until neutral and dried to obtain the porous activated carbon support.

3. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 2, characterized in that, The biomass raw material is selected from at least one of coconut shells, straw, or fruit shells.

4. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 1, characterized in that, Step S2 includes: The porous activated carbon carrier was immersed in a nutrient solution for 30 to 60 minutes under a negative pressure of -0.05 MPa to -0.09 MPa. After impregnation, the substrate is dried at 60–85°C to form the pretreated carrier containing the slow-release nutrient substrate.

5. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 4, characterized in that, The nutrient solution includes 0.5-5.0% by mass of oligochitosan and 0.01-0.1% by mass of complex trace elements, including zinc sulfate, boric acid and sodium molybdate.

6. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 1, characterized in that, The steps in S3 include: The composite microbial community was subjected to salt stress acclimatization. The composite microbial community, by weight, included the following components: Bacillus subtilis: 30-50 parts; Phosphate-solubilizing bacteria: 20-40 parts; Potassium-solubilizing bacteria: 15-30 parts; Antagonistic bacteria: 5-15 parts. Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria were cultured stepwise in culture media with sodium chloride concentrations of 0.5%, 1.0%, 1.5%, and 2.0%, respectively, with each stage lasting 24–48 hours, to obtain various domesticated strains of Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria.

7. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 1, characterized in that, The steps in S4 include: The various domesticated bacterial strains of Bacillus subtilis, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and antagonistic bacteria obtained in step S3 were collected by centrifugation, washed with sterile buffer, and resuspended to prepare a concentration of 10. 8 ~10 9 Corresponding bacterial suspensions with CFU / mL; The pretreated carrier is suspended in sterile water to form a pretreated carrier suspension. The first electrostatic adsorption loading process includes the following steps: The pH of the pretreated carrier suspension was adjusted to 6.0–9.0, at which the surface Zeta potential of the pretreated carrier was -20 mV to -50 mV; the pH of the Bacillus subtilis suspension was adjusted to 2.0–4.0, at which the surface Zeta potential of the Bacillus subtilis was +15 mV to +40 mV; the pretreated carrier suspension and the Bacillus subtilis suspension were mixed and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C. The carrier that has completed the first electrostatic adsorption loading is cultured at 30-37℃ for 12-24 hours to activate and colonize it. The second electrostatic adsorption loading process includes the following steps: The pH of the phosphate-solubilizing bacteria suspension was adjusted to 2.0–4.

0. At the pH of 2.0–4.0, the surface Zeta potential of the phosphate-solubilizing bacteria was +15mV to +40mV. The activated and colonized carrier was mixed with the phosphate-solubilizing bacteria suspension and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C. The third electrostatic adsorption loading process includes the following steps: The pH of the potassium-solubilizing bacteria suspension was adjusted to 2.0–4.

0. At the pH of 2.0–4.0, the surface zeta potential of the potassium-solubilizing bacteria was +15mV to +40mV. The carrier that had completed the second electrostatic adsorption loading was mixed with the potassium-solubilizing bacteria suspension and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C. The fourth electrostatic adsorption loading process includes the following steps: The pH of the antagonistic bacterial suspension was adjusted to 2.0–4.0, at which the surface zeta potential of the antagonistic bacteria was +15mV to +40mV. The carrier that had completed the third electrostatic adsorption loading was mixed with the antagonistic bacterial suspension and stirred at 100–150 rpm for 1–2 hours at a temperature of 25–35°C.

8. The preparation process of porous activated carbon soil conditioner loaded with microbial communities according to claim 1, characterized in that, The steps in S5 include: Microcapsule encapsulation was performed by mixing the loaded carrier with a sodium alginate solution with a mass concentration of 1.0–3.0%, and then dropping the mixture into a calcium chloride solution with a mass concentration of 2.0–5.0% for cross-linking and encapsulation. Subsequently, a low-temperature drying process is carried out. The embedded carrier is first pre-frozen at -40℃ to -60℃ for 8 to 12 hours, and then sublimation drying is carried out under a vacuum of 10 to 30 Pa to obtain the porous activated carbon soil conditioner.

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