Preparation method of amino acid fertilizer containing polypeptide

Abstract

The invention discloses a preparation method of a polypeptide-containing amino acid fertilizer, and relates to the technical field of organic fertilizer processing, and the preparation method is technically characterized by comprising the following steps: carrying out magnetic separation iron removal and color sorting classification on animal and plant protein raw materials, then crushing the animal and plant protein raw materials in a low-temperature environment of 30-40 DEG C until D50 is less than or equal to 80 [mu] m by using a wet ultrafine crusher, spraying a buffer solution with the pH value of 6.5-7.0 during the process, and controlling the water content to be 3-5%; adding a compound enzyme preparation into the crushed material for gradient enzymolysis, performing enzymolysis with neutral protease for 2-3 hours to generate 5-10kDa polypeptide, and performing compound enzymolysis with alkaline protease and papain for 4-6 hours to obtain amino acid hydrolysate; adding a silk fibroin protective agent into the hydrolysate, stirring at a constant temperature to form a compound, mixing the compound with a humic acid adhesive, preparing particles of 2-4mm through a low-temperature spray granulation tower, performing three-stage variable-temperature drying and nitrogen protection airflow dust removal, and finally performing vacuum packaging; the raw material crushing uniformity can be improved, and the enzymolysis effect is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of organic fertilizer processing technology, and in particular to a method for preparing an amino acid fertilizer containing polypeptides. Background Technology

[0002] In agricultural production, amino acid fertilizers, as an important type of organic fertilizer, have a significant effect on promoting crop growth and improving crop quality due to their rich content of amino acids and polypeptides. However, existing methods for preparing amino acid fertilizers have many shortcomings, which seriously restrict their application effectiveness and market promotion.

[0003] Specifically, in the traditional preparation process of amino acid fertilizers, the protein raw material pretreatment stage is a crucial step, but problems often arise at this stage. Take the raw material grinding step, for example; in practice, it is often difficult to achieve uniform particle size. Some parts of the raw material are ground too finely, resembling fine powder, while others are relatively coarse, exhibiting larger granules. This uneven particle size is like setting up numerous obstacles in the originally ordered "enzymatic hydrolysis channel," greatly affecting the efficiency of subsequent enzymatic hydrolysis. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a method for preparing amino acid fertilizer containing polypeptides, which improves the uniformity of raw material crushing and ensures the enzymatic hydrolysis effect.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing an amino acid fertilizer containing polypeptides includes the following steps:

[0007] (1) Protein raw material pretreatment: After the animal and plant protein raw materials are magnetically separated to remove iron and color sorted for grading, they are pulverized to D50≤80μm in a low temperature environment of 30-40℃ using a wet ultrafine pulverizer. During the pulverization process, a buffer solution of pH6.5-7.0 is sprayed to control the moisture content of the material to 3-5% to obtain pulverized material.

[0008] (2) Targeted enzymatic hydrolysis: Add a compound enzyme preparation to the pulverized material for gradient enzymatic hydrolysis. First, use neutral protease to hydrolyze for 2-3 hours to generate 5-10kDa polypeptides. Then, use alkaline protease and papain to hydrolyze for 4-6 hours to obtain an amino acid hydrolysate containing 1-3kDa small molecule polypeptides.

[0009] (3) Peptide stabilization treatment: Add silk fibroin protectant to the amino acid hydrolysate and stir at a constant temperature to form a peptide-silk fibroin complex.

[0010] (4) Granulation and molding: After mixing the composite with humic acid binder, 2-4 mm particles are prepared by low temperature spray granulation tower;

[0011] (5) Active preservation drying: Dry particles are obtained by three-stage variable temperature drying;

[0012] (6) Finished product processing: The dried granules are vacuum packaged after being dusted by a nitrogen protective gas flow.

[0013] Preferably, in step (2), the compound enzyme preparation is composed of neutral protease, alkaline protease and papain in a ratio of 25-35%:15-25%:40-50%, and the total addition amount is 1.8-2.2% of the pulverized material, wherein the neutral protease activity is ≥200U / mg, the alkaline protease activity is ≥180U / mg, and the papain activity is ≥150U / mg.

[0014] Preferably, the specific parameters for the gradient enzymatic hydrolysis are as follows: in the first stage, neutral protease hydrolysis is performed at pH 7.5-8.0 and 45-50℃ for 2.5-3 hours; in the second stage, alkaline protease and papain are mixed at a mass ratio of 1:2 and hydrolyzed at pH 8.0-8.5 and 50-55℃ for 5-6 hours.

[0015] Preferably, the silk fibroin protectant added in step (3) is 0.6-0.8% of the weight of the pulverized material, and 0.15-0.25 mol / L of Ca is added simultaneously during the reaction. 2+ Solution, control of Ca 2+ The molar ratio of silk fibroin to silk fibroin is 1:10±0.5, maintaining the conductivity of the system at 2.8-3.2 mS / cm.

[0016] Preferably, the low-temperature spray granulation parameters in step (4) include: air inlet temperature 55-60℃, atomization frequency 25-35kHz, granulation chamber micro-negative pressure -15±2Pa, and particle falling speed 0.3-0.4m / s.

[0017] Preferably, the three-stage variable temperature drying specifically includes:

[0018] First-stage dehydration: Treat at 65±1℃ and ≤20%RH for 15±1 minutes;

[0019] Second-stage slow drying: Treat at 50±1℃ and 40-50%RH for 35-40 minutes;

[0020] Third-order equilibrium: Treat for 20±1 minutes at 38±1℃ and 60-65%RH.

[0021] Preferably, in step (1), the wet ultrafine grinding adopts a circulating cooling system to maintain the grinding chamber temperature at 35±2℃, the buffer is a citrate-phosphate buffer system, and the spraying rate is 0.8-1.2L / min.

[0022] Preferably, in step (6), the airflow dust removal adopts a nitrogen flow rate of 3-5 m / s, and the vacuum packaging is carried out in a nitrogen environment with an oxygen content of ≤1.5% and the vacuum degree is maintained at ≤-0.08 MPa.

[0023] Preferably, the humic acid adhesive is sulfonated sodium humate, and the amount added is 3.5-4.5% of the dry weight of the composite, with the degree of sulfonation controlled at 0.6-0.8 mmol / g.

[0024] The present invention has the following beneficial effects:

[0025] I. Low-temperature grinding environment: In step (1) protein raw material pretreatment, a wet ultrafine grinder is used to grind the raw material at a low temperature of 30-40℃. The low-temperature environment helps to maintain the stability of the physical properties of the raw material and reduce the denaturation or agglomeration of the raw material caused by high temperature, thereby ensuring that the grinding process can be carried out more uniformly and that the particle size of the raw material is more consistent.

[0026] II. Buffer Spraying and Moisture Content Control: During the grinding process, a buffer solution with a pH of 6.5-7.0 is sprayed, and the moisture content of the material is controlled at 3-5%. Spraying the buffer solution adjusts the pH value of the environment during grinding, preventing changes in the raw material properties due to localized pH fluctuations, which would affect the grinding effect. Simultaneously, a suitable moisture content creates lubrication between the raw material particles, reducing friction and adhesion, and helping the grinder to grind the raw material more uniformly, obtaining ground material with a D50 ≤ 80μm, thus improving the uniformity of the raw material grinding.

[0027] III. Wet Ultrafine Grinding Process and Circulating Cooling System: Wet ultrafine grinding itself has a better grinding effect and can produce finer particles. Furthermore, the use of a circulating cooling system maintains the grinding chamber temperature at 35±2℃, further stabilizing the temperature conditions during the grinding process and ensuring the grinder operates under stable conditions, which is beneficial for improving the uniformity of grinding.

[0028] IV. Targeted Enzymatic Hydrolysis Process: Step (2) employs a gradient enzymatic hydrolysis method. First, neutral protease is used for hydrolysis for 2-3 hours to generate 5-10 kDa peptides, followed by hydrolysis with a combination of alkaline protease and papain for 4-6 hours. This gradient enzymatic hydrolysis process can target the decomposition of raw materials according to the characteristics of different enzymes, gradually breaking down large protein molecules into small peptide molecules. Different enzymes play their roles at different stages, which can make fuller use of the protein resources in the raw materials, improve the hydrolysis efficiency, and ensure the hydrolysis effect.

[0029] V. Optimization of the Compound Enzyme Preparation: The compound enzyme preparation consists of neutral protease, alkaline protease, and papain in a ratio of 25-35%:15-25%:40-50%, with a total addition amount of 1.8-2.2% of the pulverized material. The enzyme activity of each enzyme meets certain standards (neutral protease activity ≥200 U / mg, alkaline protease activity ≥180 U / mg, papain activity ≥150 U / mg). This optimized compound enzyme preparation formula can fully utilize the synergistic effect of different enzymes, improve the speed and efficiency of the enzymatic hydrolysis reaction, and ensure that the proteins in the raw materials are more thoroughly broken down into small molecule peptides, guaranteeing the enzymatic hydrolysis effect.

[0030] VI. Precise Control of Gradient Enzymatic Hydrolysis Parameters: The specific parameters for gradient enzymatic hydrolysis are as follows: First stage: neutral protease hydrolysis at pH 7.5-8.0 and 45-50℃ for 2.5-3 hours; Second stage: alkaline protease and papain hydrolysis at a 1:2 mass ratio at pH 8.0-8.5 and 50-55℃ for 5-6 hours. Precise control of parameters such as pH and temperature during the enzymatic hydrolysis process provides the most suitable reaction environment for different enzymes, allowing their activity to reach its optimal state, thereby improving the efficiency and specificity of the enzymatic hydrolysis reaction and ensuring the hydrolysis effect.

[0031] VII. Peptide Stabilization Treatment: In step (3), a silk fibroin protectant is added to the amino acid hydrolysate, and the mixture is stirred at a constant temperature to form a peptide-silk fibroin complex. The silk fibroin protectant can bind to the peptide, protect the stability of the peptide during subsequent processing, and prevent the peptide from being further decomposed or inactivated, thereby ensuring the effectiveness and stability of the peptide in the enzymatic hydrolysis product, and indirectly ensuring the enzymatic hydrolysis effect.

[0032] 8. The Influence of Raw Material Grinding Uniformity on Enzymatic Hydrolysis: Due to the aforementioned measures to improve the uniformity of raw material grinding, the particle size of the raw materials becomes more uniform. During enzymatic hydrolysis, the enzyme can contact the raw material particles more evenly, allowing the enzymatic reaction to proceed more uniformly on each particle. This avoids localized over- or under-enzymatic hydrolysis caused by uneven particle size, thus ensuring the consistency and stability of the overall enzymatic hydrolysis effect. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a rough process flow diagram of an embodiment of the present invention.

[0035] Figure 2 This is a detailed process flow diagram of an embodiment of the present invention.

[0036] Figure 3 This is a flowchart of the three-stage variable temperature drying process in an embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of 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.

[0038] like Figures 1 to 2 As shown, the process described in this embodiment includes the following steps:

[0039] 1. Protein raw material pretreatment

[0040] In the preparation of amino acid fertilizers containing peptides, the pretreatment of protein raw materials is a crucial initial step. High-quality soybean protein powder (fish meal, etc., can also be used as needed) is selected as the main raw material. After the raw materials enter the production process, they are first processed by a magnetic separator. This magnetic separator has a strong magnetic field strength of ≥1200Gs, which can efficiently remove magnetic impurities such as iron filings mixed in the raw materials, avoiding damage to subsequent processing equipment and ensuring the purity of the product.

[0041] After magnetic separation to remove iron, the raw materials need to be finely graded by a color sorter. The color sorter screens the raw materials according to their particle size, separating those with a particle size range of 0.5-1.5mm to ensure that the raw material particles are relatively uniform in size, providing a good foundation for subsequent crushing and enzymatic hydrolysis processes.

[0042] The graded raw materials were fed into a wet ultrafine pulverizer for grinding. This pulverizer is equipped with an advanced circulating cooling system, which effectively controls the temperature of the grinding chamber during the grinding process, stabilizing it within the range of 35±2℃. Simultaneously, a citrate-phosphate buffer solution, precisely prepared by mixing 0.1 mol / L sodium citrate and 0.05 mol / L disodium hydrogen phosphate, with a stable pH of 6.8, is sprayed into the pulverizer at a rate of 1.0 L / min. Under suitable temperature and buffer conditions, the raw materials are thoroughly pulverized, ultimately achieving a fineness of D50 = 75 μm, with the moisture content controlled at 4.2%, forming a uniform and fine slurry, providing an ideal substrate for subsequent targeted enzymatic hydrolysis.

[0043] 2. Targeted enzymatic hydrolysis

[0044] The pulverized material is accurately transferred into the enzymatic hydrolysis tank to begin the crucial directional enzymatic hydrolysis step. The enzymatic hydrolysis process employs a two-stage gradient enzymatic hydrolysis method to fully utilize the characteristics of different enzymes and achieve efficient and precise enzymatic hydrolysis results.

[0045] Stage 1: In the enzymatic hydrolysis tank, the pH of the system was first adjusted to 7.8, and the temperature was controlled at 48℃. A carefully formulated compound enzyme preparation was added at 2.0% of the total material weight. This compound enzyme preparation consisted of neutral protease, alkaline protease, and papain in a ratio of 30%:20%:50%, with enzyme activities of 220 U / mg, 190 U / mg, and 160 U / mg, respectively. Under suitable pH and temperature conditions, the compound enzyme preparation began to function, initially decomposing the proteins in the raw materials. After 2.8 hours of enzymatic hydrolysis, a 7.5 kDa polypeptide was successfully generated.

[0046] The second stage: After the first stage of enzymatic hydrolysis is completed, the enzymatic hydrolysis system is adjusted by raising the pH to 8.3 and the temperature to 53℃. The remaining enzyme is added according to a 1:2 mass ratio of alkaline protease to papain, and the enzymatic hydrolysis reaction continues. During the 5.5 hours of the second stage, the enzymatic hydrolysis reaction progresses further, gradually breaking down large polypeptide molecules into smaller polypeptide molecules, ultimately yielding an amino acid hydrolysate containing 2.1 kDa small polypeptide molecules. This gradient enzymatic hydrolysis method can fully utilize the activity characteristics of different enzymes to achieve efficient and targeted protein decomposition, providing high-quality raw materials for subsequent polypeptide stabilization treatment and fertilizer preparation.

[0047] 3. Peptide stabilization treatment

[0048] After completing the targeted enzymatic hydrolysis and obtaining an amino acid hydrolysate containing a small molecule peptide of 2.1 kDa, peptide stabilization treatment is required to ensure the stability of the peptide during subsequent processing and storage, and to prevent it from being degraded or inactivated due to environmental factors or chemical reactions.

[0049] In practice, 0.7% (by dry weight of the material) of silk fibroin protective agent is precisely added to the hydrolysate. Silk fibroin, as a natural biomolecule, possesses excellent biocompatibility and stability, and can interact with polypeptide molecules to form a stable complex structure. Simultaneously with the addition of the silk fibroin protective agent, a 0.20 mol / L CaCl2 solution is added dropwise, with strict control of the Ca concentration. 2+ The molar ratio with silk fibroin is 1:10. (Ca) 2+ It acts as a cross-linking agent in the system, promoting the interaction between silk fibroin molecules and enhancing the stability of the complex. Simultaneously, through a precise control system, the conductivity of the system is maintained at 3.0 mS / cm to ensure that the ionic strength and charge balance of the reaction system are at their optimal state.

[0050] The prepared reaction system was placed in a constant temperature environment of 50°C and stirred at 300 rpm for 40 minutes. Under these constant temperature and stirring conditions, the silk fibroin protectant and peptide molecules fully contacted and interacted, gradually forming a peptide-silk fibroin complex. This complex not only effectively protects the peptide molecules from the influence of the external environment but may also endow them with some new functional properties, providing a higher quality basic material for subsequent fertilizer preparation.

[0051] 4. Granulation and molding

[0052] The peptide-silk fibroin complex obtained after peptide stabilization needs to be further granulated for storage, transportation and use.

[0053] The composite was mixed with sodium sulfonated humate adhesive. Sodium sulfonated humate is a sulfonated modified humic acid substance with good adhesion and adsorption properties. In this process, the degree of sulfonation of the sodium sulfonated humate adhesive was controlled at 0.7 mmol / g, and the addition amount was 4.0% of the dry weight of the composite. The control of the degree of sulfonation is crucial to the performance of the adhesive. An appropriate degree of sulfonation allows the adhesive to be uniformly dispersed in the composite and form a good bond with the composite molecules, thereby providing sufficient adhesive force.

[0054] The uniformly mixed material is fed into a low-temperature spray granulation tower for granulation. This tower employs advanced spray drying technology, precisely controlling various parameters to produce high-quality granules. The inlet air temperature is set at 58℃, ensuring rapid evaporation of moisture while preventing material denaturation or loss of active ingredients due to excessive heat. The atomization frequency is set to 30kHz; this higher frequency enables the material to form fine, uniform droplets, which is beneficial for granule formation and drying. The granulation chamber maintains a slight negative pressure of -16Pa. This negative pressure environment helps the droplets disperse and deposit evenly, preventing particle adhesion and aggregation. Simultaneously, the particle falling speed is adjusted to 0.35m / s to ensure sufficient residence time for drying and shaping within the granulation chamber.

[0055] Through the precisely controlled granulation process described above, regular spherical granules with a particle size of 3.2±0.3 mm are finally produced. These granules have a uniform particle size and good flowability, which facilitates subsequent packaging, storage and use, and also improves the application effect and utilization rate of fertilizers.

[0056] 5. Active preservation drying

[0057] In order to retain the active ingredients formed during the preparation of the polypeptide-silk fibroin complex particles to the greatest extent and to ensure the high activity of the final fertilizer product, a three-stage variable temperature drying process is used to dry the particles.

[0058] First-stage dehydration: The granulated particles are rapidly transferred to a first-stage dehydration and drying device. This stage is set at a drying temperature of 65℃, an ambient humidity of 18% RH, and a processing time of 15 minutes. Under these high temperature and low humidity conditions, the free water on the particle surface evaporates rapidly, achieving quick removal of surface moisture. This step quickly reduces the surface moisture content of the particles, preventing them from sticking or clumping during subsequent processing due to excessive surface moisture, and also prepares them for the subsequent slow-drying stage.

[0059] Second-stage slow drying: After the first-stage dehydration, the granules enter the second-stage slow drying stage. In this stage, the drying temperature is adjusted to 50℃, the humidity is increased to 45% RH, and the processing time is 38 minutes. Lowering the temperature and appropriately increasing the humidity helps slow down the evaporation rate of moisture inside the granules, avoiding stress caused by excessively rapid evaporation and thus preventing cracking. During this stage, the moisture inside the granules gradually diffuses outward, slowly exchanging moisture with the external environment, allowing the granules to gradually reach a stable drying state while maintaining a certain moisture content.

[0060] Third-stage equilibrium: After the second-stage slow drying, the granules enter the third-stage equilibrium stage. In this stage, the drying temperature is further reduced to 38℃, the humidity is adjusted to 62% RH, and the processing time is 20 minutes. Under the lower temperature and higher humidity environment, the moisture inside the granules can be distributed more evenly. Through slow equilibrium with the external environment, the moisture content of the granules is uniformly controlled to ≤5%. This stage is a crucial step in ensuring uniform and stable moisture content, enabling the granules to maintain good physical and chemical stability during storage and use, and preventing granule deterioration or reduced activity due to uneven moisture content.

[0061] 6. Finished Product Processing

[0062] The dried granules, after being processed by a three-stage variable temperature drying process, need to undergo further finished product processing to ensure the quality and activity of the product.

[0063] First, the dried granules are treated with a nitrogen-protected airflow dust removal system. This system uses nitrogen as the protective gas, with the nitrogen flow rate controlled at 4 m / s. Under the protection of nitrogen, the airflow effectively removes dust and impurities from the granule surface, while preventing contact between the granules and oxygen, thus preventing the loss of active ingredients due to oxidation. The nitrogen-protected airflow dust removal system not only improves the purity and appearance of the product but also further protects the activity of the granules, ensuring the product performs optimally during use.

[0064] Subsequently, the dried granules, after dust removal, are vacuum-packed in a nitrogen atmosphere with an oxygen content ≤1.2%. Vacuum packaging effectively isolates the granules from air and moisture, preventing them from being affected by the external environment during storage and transportation. During the packaging process, the vacuum level is controlled at -0.085 MPa to ensure a high vacuum state inside the packaging bag. This high-vacuum packaging environment minimizes the contact between the granules and oxygen, delaying the oxidation reaction of the granules, while preventing moisture from entering the packaging bag, thus maintaining the dryness and activity of the granules.

[0065] Through the aforementioned series of meticulous processes, a highly active peptide-amino acid fertilizer was finally obtained. This fertilizer is not only rich in various small-molecule peptides and amino acids, but also possesses stable physical and chemical properties, providing comprehensive nutritional support for crops, promoting crop growth and development, and improving crop yield and quality. Furthermore, its excellent storage stability and effectiveness make this fertilizer a promising candidate for agricultural applications.

[0066] Key parameter descriptions:

[0067] Enzymatic hydrolysis efficiency verification

[0068] Enzymatic hydrolysis, as the core step in the entire preparation process, directly determines the content and quality of peptides in the final product. To accurately evaluate the hydrolysis effect, we used SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) to detect the molecular weight distribution of peptides in the hydrolysate. SDS-PAGE is a widely used technique for protein and peptide analysis, capable of separating peptides into different bands based on molecular weight. By comparing with standard peptides of known molecular weight, we can accurately determine the molecular weight range of peptides in the hydrolysate. Extensive experimental verification showed that when the proportion of peptides smaller than 3 kDa in the hydrolysate reaches ≥85%, the enzymatic hydrolysis process is relatively thorough, efficiently breaking down the proteins in the raw materials into small-molecule peptides, providing a high-quality substrate for subsequent stabilization and granulation. Strict control of this parameter ensures the activity and effectiveness of the peptides in the product, laying the foundation for the efficient utilization of fertilizers.

[0069] Granulation strength test

[0070] Granulation strength is a crucial indicator of fertilizer granule quality, directly impacting its stability and effectiveness during storage, transportation, and application. To assess granule strength, we tested the compressive strength and disintegration time of the granules according to GB / T 8571 standard. The compressive strength test involved applying progressively increasing pressure to individual granules using specialized equipment until they ruptured, recording the pressure value at that point. Through multiple experiments and data analysis, we determined that the compressive strength of the granules should be ≥12N to ensure they do not break under external pressure during storage and transportation. The disintegration time test involved placing the granules in a specific simulated environment and observing their disintegration within a specified time. Experimental results showed that the disintegration time should be ≤30 seconds. This ensures rapid disintegration after application, releasing nutrients without excessively rapid disintegration leading to nutrient loss. By strictly controlling the granulation strength parameters, we ensured that the fertilizer granules possessed excellent physical properties, meeting the needs of actual production and use.

[0071] Activity retention rate

[0072] Maximizing the preservation of peptide bioactivity is crucial during peptide stabilization and drying. To accurately assess the activity retention of peptides after drying, we employed ELISA (Enzyme-Linked Immunosorbent Assay). ELISA is a highly sensitive and specific immunological detection method capable of accurately detecting peptide bioactivity. After a three-stage drying process, we tested the peptide activity in the dried granules, showing a bioactivity retention rate of ≥92%. This result demonstrates that our three-stage variable-temperature drying process effectively protects peptide activity, preventing inactivation due to high temperatures and drying conditions. This high activity retention rate ensures that the fertilizer can fully utilize the biofunctional properties of the peptides during application, providing sufficient nutritional support for crops.

[0073] This embodiment has the following experimental results:

[0074] The polypeptide-containing amino acid fertilizer prepared according to this method exhibits significant advantages in both nutrient content and activity stability. Precise testing and analysis revealed that the fertilizer contains ≥45% amino acids and ≥18% polypeptides. The high content of amino acids and polypeptides provides crops with abundant nitrogen sources and bioactive substances, promoting crop growth and development, and enhancing crop resistance and yield.

[0075] Compared to products prepared using traditional high-temperature processes, fertilizers prepared using this method exhibit significant advantages in storage stability. Traditional high-temperature processes may cause thermal denaturation or degradation of active ingredients such as peptides during drying, thereby reducing fertilizer activity. However, the three-stage variable-temperature drying process employed in this method minimizes the loss of active ingredients like peptides by precisely controlling parameters such as drying temperature, humidity, and time. After a 6-month storage experiment, the loss rate of active ingredients in fertilizers prepared using this method was less than 5%, while the loss rate of active ingredients in products prepared using traditional high-temperature processes is often higher. This significant difference indicates that fertilizers prepared using this method have better storage stability, maintaining their activity and effectiveness for a longer period, providing a more reliable fertilizer product for agricultural production.

[0076] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for preparing an amino acid fertilizer containing polypeptides, characterized in that, Includes the following steps: (1) Protein raw material pretreatment: After the animal and plant protein raw materials are magnetically separated to remove iron and color sorted for grading, they are pulverized to D50≤80μm in a low temperature environment of 30-40℃ using a wet ultrafine pulverizer. During the pulverization process, a buffer solution of pH6.5-7.0 is sprayed to control the moisture content of the material to 3-5% to obtain pulverized material. (2) Targeted enzymatic hydrolysis: Add a compound enzyme preparation to the pulverized material for gradient enzymatic hydrolysis. First, use neutral protease to hydrolyze for 2-3 hours to generate 5-10kDa polypeptides. Then, use alkaline protease and papain to hydrolyze for 4-6 hours to obtain an amino acid hydrolysate containing 1-3kDa small molecule polypeptides. (3) Peptide stabilization treatment: Add silk fibroin protectant to the amino acid hydrolysate and stir at a constant temperature to form a peptide-silk fibroin complex. (4) Granulation and molding: After mixing the composite with humic acid binder, 2-4 mm particles are prepared by low-temperature spray granulation tower; (5) Active preservation drying: Dry particles are obtained by three-stage variable temperature drying; (6) Finished product processing: The dried granules are vacuum packaged after being dusted by a nitrogen protective gas flow.

2. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: In step (2), the compound enzyme preparation is composed of neutral protease, alkaline protease and papain in a ratio of 25-35%:15-25%:40-50%, with a total addition amount of 1.8-2.2% of the pulverized material. The neutral protease activity is ≥200U / mg, the alkaline protease activity is ≥180U / mg, and the papain activity is ≥150U / mg.

3. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 2, characterized in that: The specific parameters for the gradient enzymatic hydrolysis are as follows: in the first stage, neutral protease is used for hydrolysis at pH 7.5-8.0 and 45-50℃ for 2.5-3 hours; in the second stage, alkaline protease and papain are mixed at a mass ratio of 1:2 and hydrolyzed at pH 8.0-8.5 and 50-55℃ for 5-6 hours.

4. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: The silk fibroin protectant added in step (3) is 0.6-0.8% of the weight of the pulverized material, and 0.15-0.25 mol / L of Ca is added simultaneously during the reaction. 2+ Solution, control of Ca 2+ The molar ratio of silk fibroin to silk fibroin is 1:10±0.5, maintaining the conductivity of the system at 2.8-3.2 mS / cm.

5. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: The low-temperature spray granulation parameters in step (4) include: air inlet temperature 55-60℃, atomization frequency 25-35kHz, granulation chamber micro-negative pressure -15±2Pa, and particle falling speed 0.3-0.4m / s.

6. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: The three-stage variable temperature drying specifically includes: First-stage dehydration: treatment at 65±1℃ and ≤20%RH for 15±1 minutes; Second-stage slow drying: Treat at 50±1℃ and 40-50%RH for 35-40 minutes; Third-order equilibrium: Treat for 20±1 minutes at 38±1℃ and 60-65%RH.

7. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: In step (1), the wet ultrafine grinding adopts a circulating cooling system to maintain the grinding chamber temperature at 35±2℃, the buffer is a citrate-phosphate buffer system, and the spraying rate is 0.8-1.2L / min.

8. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: In step (6), the airflow dust removal uses a nitrogen flow rate of 3-5 m / s, and the vacuum packaging is carried out in a nitrogen environment with an oxygen content of ≤1.5%, and the vacuum degree is maintained at ≤-0.08 MPa.

9. The method for preparing a polypeptide-containing amino acid fertilizer according to claim 1, characterized in that: The humic acid binder is sulfonated sodium humate, and the amount added is 3.5-4.5% of the dry weight of the composite, with the degree of sulfonation controlled at 0.6-0.8 mmol / g.

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