Organic water-soluble fertilizer taking natural organic matters as raw materials and preparation method of organic water-soluble fertilizer

Abstract

The invention relates to the technical field of fertilizer preparation, and discloses an organic water-soluble fertilizer taking natural organic matters as raw materials and a preparation method of the organic water-soluble fertilizer. The organic water-soluble fertilizer is prepared from the following components in parts by weight: 20 to 30 parts of photocatalytic pretreated coffee grounds, 15 to 25 parts of fish scale collagen peptide liquid with the molecular weight of 500 to 1000Da, 2 to 5 parts of photosensitization bacterium agent, 3 to 8 parts of lignin nanofiber, 1 to 3 parts of molasses quantum dots and 8 to 12 parts of silk fibroin membrane solution. The preparation method comprises the following steps: photocatalytic activation of coffee residue nano TiO2, low-temperature directional enzymolysis of fish scales, light-dark two-stage flora fermentation, quantum dot-lignin coupling reaction and microfluidic gradient spray drying. The organic matter decomposition efficiency is improved through the photocatalysis-flora synergistic effect, a quantum dot-peptide chain complexing system replaces a chemical chelating agent to achieve environment-friendly chelating, the silk fibroin pH response membrane breaks the contradiction between storage and release, and finally the organic water-soluble fertilizer which is high in activity, free of pollution and capable of achieving intelligent slow release is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer preparation, and particularly to an organic water-soluble fertilizer using natural organic matter as a raw material and a preparation method thereof. Background Art

[0002] Preparing organic water-soluble fertilizers from natural organic matter (such as agricultural waste, by-products of aquatic product processing) is an important direction for the resource utilization of agricultural waste and the development of green fertilizers. Such fertilizers have attracted much attention in recent years because they are rich in humic acid, polypeptides and trace elements, and also have the functions of improving soil and promoting crop growth. However, limited by technical bottlenecks such as raw material conversion efficiency, nutrient stability and environmental compatibility, their large-scale application still faces challenges.

[0003] In the raw material pretreatment stage, conventional technologies mostly rely on mechanical crushing or high-temperature steaming to break the organic matter structure. However, high temperature easily causes the inactivation of heat-sensitive active substances (such as natural enzymes and vitamins), and simple physical crushing is difficult to fully release the bound nutrients. For example, after traditional processes are used to treat raw materials such as coffee grounds and fish scales, the decomposition efficiency of the lignin-cellulose complex is less than 40%, and the subsequent fermentation cycle is forced to be extended to 5-7 days. The volatilization of by-products such as ammonia during the process further causes nutrient loss.

[0004] To improve water solubility, existing methods generally introduce chemical additives such as ethylenediaminetetraacetic acid (EDTA) and citric acid. Although chelation can delay the precipitation of metal ions, their non-degradable characteristics lead to the accumulation of persistent pollutants in the soil, and long-term application may damage the balance of the microbial community. In addition, the non-specific binding of chemical chelating agents to organic matter will interfere with the spatial conformation of active components such as humic acid, reducing the biological effect of the fertilizer.

[0005] In terms of the storage and release regulation of the finished product, although traditional coating materials such as paraffin and polyvinyl alcohol can prevent moisture in the short term, their homogeneous and dense structure results in slow disintegration of the granules when they encounter water, and the nutrient release lags behind the absorption demand of crops. More seriously, such materials are difficult to degrade in the environment, and long-term residues exacerbate the white pollution in farmland. The above defects indicate that there are systematic deficiencies in the existing technical system in terms of the efficient conversion of natural organic matter, the green stabilization of nutrients and the design of functional coatings, which restricts the industrialization process of organic water-soluble fertilizers. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides an organic water-soluble fertilizer using natural organic matter as a raw material and a preparation method thereof, which solves the technical problems of low conversion efficiency, chemical additive residue pollution and uncontrollable storage-release performance when preparing water-soluble fertilizers from natural organic matter.

[0007] To achieve the above purpose, the present invention is implemented by the following technical scheme: an organic water-soluble fertilizer using natural organic matter as raw materials, comprising the following components by weight: 20-30 parts of coffee grounds, 15-25 parts of fish scale hydrolyzate, 2-5 parts of photosensitizing agent, 3-8 parts of lignin nanofibers, 1-3 parts of molasses-derived quantum dots, 8-12 parts of silk fibroin film solution, 0.5-2 parts of citric acid, and the balance is deionized water; Wherein, the coffee grounds are pre-treated by nano-TiO2 photocatalysis, and the fish scale hydrolyzate is a collagen peptide solution with a molecular weight of 500-1000Da.

[0008] Preferably, the photosensitizing bacterial agent includes Rhodospirillum and nitrogen-fixing bacteria, and the volume ratio between the two is 2:1 to 4:1.

[0009] Preferably, the molasses-derived quantum dots have a particle size of 3-5 nm and contain carboxylic acid groups on their surface.

[0010] Preferably, in the silk fibroin membrane solution, the β-folded structure accounts for 55-65% of the total secondary structure of the silk fibroin molecule, the α-helical structure accounts for 10-15% of the total secondary structure of the silk fibroin molecule, and the rest is a random coil structure.

[0011] The present invention also provides a method for preparing the organic water-soluble fertilizer using natural organic matter as raw materials as described above, comprising the following steps: S1, coffee grounds are impregnated with nano-TiO2 sol and treated with ultraviolet light to obtain a photocatalytically active carrier; S2, fish scales are enzymatically hydrolyzed with a composite protease at low temperature and then ultrafiltered to obtain collagen peptide liquid; S3, aerobically fermenting the product of step S1 and the photosensitized bacterial agent under light, and then adding the product of step S2 and molasses-derived quantum dots for dark fermentation; S4, after the fermentation liquid is coupled with the lignin nanofibers, the silk fibroin membrane solution is added and mixed; S5. The mixed solution is subjected to microfluidic gradient spray drying to obtain organic water-soluble fertilizer particles.

[0012] Preferably, in step S1, the concentration of the nano-TiO2 sol is 0.8-1.2wt%, and the ultraviolet light treatment conditions are wavelength 360-370nm, power 40-60W, and time 15-25min.

[0013] Preferably, in step S2, the composite protease is alkaline protease and trypsin, with a mass ratio of 1.5:1 to 2.5:1, and the enzymolysis temperature is 35-45°C and the time is 4-8h.

[0014] Preferably, in the S3 step, the aerobic fermentation conditions are light intensity of 4500 - 5500 lux, temperature of 25 - 35 °C, and time of 20 - 28 h. In the S3 step, the dark fermentation conditions are anaerobic environment, temperature of 30 - 40 °C, and time of 10 - 14 h.

[0015] Preferably, in the S4 step, the coupling reaction is carried out in the presence of a catalyst. The catalyst is p-toluenesulfonic acid, and the addition amount is 0.3 - 0.7% of the total mass of the reaction system.

[0016] Preferably, in the S5 step, the inlet temperature of the microfluidic gradient spray drying gradually decreases from 170 - 190 °C to 60 - 80 °C, and the nozzle aperture shrinks from 40 - 60 μm to 8 - 12 μm.

[0017] The present invention provides an organic water-soluble fertilizer using natural organic matter as a raw material and a preparation method thereof. It has the following beneficial effects: 1. Through the synergistic activation of photocatalytic pretreatment and microbial metabolism, the present invention significantly shortens the decomposition cycle of organic matter. The traditional process relies on single microbial fermentation, with insufficient raw material activation efficiency. This solution uses ultraviolet light to excite nano-TiO2 to continuously break down macromolecular structures, synchronously activating the electron transfer chain of photosensitive bacteria, and solving the problems of low yield and high energy consumption in the traditional process.

[0018] 2. The present invention uses quantum dot - peptide chain complexation technology to replace chemical chelating agents, achieving an essential improvement in water solubility. Existing methods rely on synthetic chelating agents such as EDTA, with prominent risks of residual pollution. This solution forms a stable dispersion system through the size-matching complexation of molasses quantum dots and collagen peptides with a specific molecular weight, avoiding chemical residues and ensuring efficient nutrient release.

[0019] 3. The intelligent response structure of the silk fibroin film in the present invention takes into account both storage stability and controlled release. Conventional coating materials cannot balance the requirements of moisture-proof and disintegration, easily leading to the inactivation of active ingredients. This solution uses the pH sensitivity of the β-sheet conformation to maintain a dense barrier during storage and quickly disintegrate in the soil environment, overcoming the technical shortcoming of uncontrollable slow release of traditional materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of the preparation method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] Please refer to the appendix Figure 1 , Examples 1-3 of the present invention provide an organic water-soluble fertilizer made from natural organic matter and its preparation method. The specific example content is as follows: Example 1: Raw material ratio (parts by mass): 25 parts of coffee grounds, 20 parts of fish scale hydrolyzate, 3 parts of photosensitizing bacterium agent (Rhodospirillum: Azotobacter = 3:1), 5 parts of lignin nanofibers, 2 parts of molasses-derived quantum dots, 10 parts of silk fibroin membrane solution, 1 part of citric acid, and the balance is deionized water.

[0023] Preparation steps: Photocatalytic pretreatment of coffee grounds: Concentration of TiO2 sol is 1.0%, ultrasonic dispersion for 10 min (frequency 30 kHz); Ultraviolet light treatment: wavelength 365 nm, power 50 W, time 20 min; Drying conditions: 60 °C, 2 h.

[0024] Low-temperature enzymatic hydrolysis of fish scales: Ratio of enzymatic hydrolysate: fish scales: water = 1:3; Ratio of compound protease (alkaline protease: trypsin = 2:1); Enzymatic hydrolysis conditions: 40 °C, 6 h; Molecular weight cut-off of ultrafiltration membrane is 500 Da; Two-stage light-dark fermentation: Photocatalytic fermentation: light intensity 5000 lux, temperature 30 °C, 24 h; Dark fermentation: temperature 35 °C, 12 h, nitrogen replacement frequency once every 3 h (replacement volume 60%); Quantum dot-lignin coupling: Reaction temperature 60 °C, concentration of catalyst (p-toluenesulfonic acid) 0.5%, reaction time 2 h; Preparation of silk fibroin membrane: Silk degumming conditions: 1% NaHCO3 solution, 95 °C, 30 min; β-sheet induction: ethanol: water = 7:3, standing for 12 h.

[0025] Spray drying: Inlet temperature gradient: 180 °C → 70 °C, nozzle aperture 50 μm → 10 μm; Particle size: 120 - 150 μm.

[0026] Example 2: Raw material ratio (parts by mass): 30 parts of coffee grounds, 15 parts of fish scale hydrolyzate, 5 parts of photosensitizing bacterium agent (Rhodospirillum: Azotobacter = 4:1), 8 parts of lignin nanofibers, 1 part of molasses-derived quantum dots, 12 parts of silk fibroin membrane solution, 0.5 part of citric acid, and the balance of deionized water.

[0027] Preparation steps: Photocatalytic pretreatment of coffee grounds: The concentration of TiO2 sol is 0.8%, and ultrasonic dispersion is carried out for 15 min (frequency 20 kHz); Ultraviolet light treatment: wavelength 360 nm, power 60 W, time 25 min; Drying conditions: 70 °C, 1 h; Low-temperature enzymatic hydrolysis of fish scales: Ratio of enzymatic hydrolysate: fish scales: water = 1:2; Ratio of composite protease (alkaline protease: trypsin = 2.5:1); Enzymatic hydrolysis conditions: 45 °C, 4 h; Molecular weight cut-off of ultrafiltration membrane is 1000 Da; Light-dark two-stage fermentation: Photocatalytic fermentation: light intensity 5500 lux, temperature 35 °C, 20 h; Dark fermentation: temperature 40 °C, 10 h, nitrogen replacement frequency once every 2 h (replacement volume 70%); Quantum dot-lignin coupling: Reaction temperature 65 °C, catalyst concentration 0.7%, reaction time 1.5 h; Preparation of silk fibroin membrane: Silk degumming conditions: 1.5% NaHCO3 solution, 100 °C, 20 min; β-sheet induction: ethanol: water = 8:2, standing for 10 h; Spray drying: Inlet temperature gradient: 190 °C → 60 °C, nozzle aperture 60 μm → 8 μm; Particle size: 80-100 μm.

[0028] Example 3: Raw material ratio (parts by mass): 20 parts of coffee grounds, 25 parts of fish scale hydrolyzate, 2 parts of photosensitizing bacterium agent (Rhodospirillum: Azotobacter = 2:1), 3 parts of lignin nanofibers, 3 parts of molasses-derived quantum dots, 8 parts of silk fibroin membrane solution, 2 parts of citric acid, and the balance of deionized water.

[0029] Preparation steps: Photocatalytic pretreatment of coffee grounds: The concentration of TiO2 sol is 1.2%, and ultrasonic dispersion is carried out for 8 min (frequency 40 kHz); Ultraviolet light treatment: wavelength 370 nm, power 40 W, time 15 min; Drying conditions: 50 °C, 3 h; Low-temperature enzymatic hydrolysis of fish scales: Ratio of enzymatic hydrolysate: fish scales: water = 1:4; Ratio of compound protease (alkaline protease: trypsin = 1.5:1); Enzymatic hydrolysis conditions: 35 °C, 8 h; Molecular weight cut-off of ultrafiltration membrane 800 Da; Light-dark two-stage fermentation: Photocatalytic fermentation: light intensity 4500 lux, temperature 25 °C, 28 h; Dark fermentation: temperature 30 °C, 14 h, nitrogen replacement frequency once every 4 h (replacement volume 50%); Quantum dot-lignin coupling: Reaction temperature 55 °C, catalyst concentration 0.3%, reaction time 2.5 h; Preparation of silk fibroin membrane: Silk degumming conditions: 0.5% NaHCO3 solution, 90 °C, 40 min; β-sheet induction: ethanol: water = 6:4, standing for 14 h; Spray drying: Inlet temperature gradient: 170 °C → 80 °C, nozzle aperture 40 μm → 12 μm; Particle size: 150 - 200 μm.

[0030] Comparative example 1-1: Changed content: The photosensitizing bactericide is removed from the raw material ratio, and the other components are the same as in Example 1.

[0031] Preparation conditions: The photocatalytic fermentation stage is cancelled, and single dark fermentation is directly carried out (temperature 35 °C, time 36 h).

[0032] Comparative example 1-2: Changed content: The ultraviolet light wavelength in the coffee residue pretreatment is set to 310 nm (the claimed range is 360 - 370 nm), and the rest is the same as in Example 1.

[0033] Comparative example 2-1: Changed content: The molasses quantum dots are replaced with EDTA (addition amount 2%), and the other components are the same as in Example 2.

[0034] Preparation conditions: The quantum dot-lignin coupling step is omitted, and EDTA is directly added.

[0035] Comparative example 2-2: Content of change: The temperature for enzymatic hydrolysis of fish scales is set at 50°C (the claimed range is 35 - 45°C), and the rest is the same as in Example 2.

[0036] Comparative Example 3 - 1: Content of change: Remove the fibroin film solution from the raw materials and replace it with an equal amount of polyvinyl alcohol (PVA). The other components are the same as in Example 3.

[0037] Preparation conditions: Spray drying is carried out at a constant temperature of 180°C (without gradient cooling).

[0038] Comparative Example 3 - 2: Content of change: The inlet temperature of spray drying is kept constant at 200°C (the claimed gradient is 170 - 190°C → 60 - 80°C), and the rest is the same as in Example 3.

[0039] Experiment 1: Description of the core functional component verification experiment Experiment purpose: Verify the necessity of photosensitizing bacterium agent, molasses quantum dots, and fibroin film for fermentation yield, water solubility, and storage stability.

[0040] Test groups: Example 1, Comparative Example 1 (without photosensitizing bacterium agent), Comparative Example 3 (EDTA replaces quantum dots), Comparative Example 5 (PVA replaces fibroin).

[0041] Experiment steps: Fermentation yield test: Take 500 g of raw materials for each group and process them according to the corresponding preparation method; After fermentation ends, take 100 g of the fermentation broth, dry it at 105°C to a constant weight, and calculate the utilization rate of organic matter:

[0042] Water solubility test: Take 10 g of the finished product and dissolve it in 1 L of deionized water, stir magnetically for 10 min; After standing for 30 min, take the supernatant and filter it through a 0.45 - μm filter membrane, and measure the total nitrogen and total potassium contents in the filtrate; Calculate the metal ion complexation rate:

[0043] Storage stability test: Seal and store the finished product in an incubator at 30°C and 70% humidity; Take samples monthly to detect the retention rate of active substances (collagen peptides, humic acid).

[0044] Experiment data table: Table 1: Experiment data of core functional component verification Summary: Experimental data shows that removing or replacing the core functional components (photosensitizing bacteria agent, molasses quantum dots, silk fibroin film) in the present invention will lead to a significant deterioration in product performance. The absence of the photosensitizing bacteria agent directly disrupts the synergistic effect between photocatalysis and biological fermentation, resulting in a decrease of about 21.3% in the decomposition efficiency of macromolecular organic matter in coffee grounds. This phenomenon is closely related to the "light-driven metabolic pathway switching mechanism" proposed in the present invention - the electron transfer chain activated by the photosensitizing bacteria group under specific wavelength light is the key driving force for efficient carbon source conversion, and such metabolic regulation cannot be achieved by traditional single-strain or fermentation modes.

[0045] After molasses quantum dots were replaced by EDTA, the metal ion complexation rate decreased by 23.2%, verifying the core role of the "quantum dot - peptide chain size-matching complexation mechanism". Although EDTA has chelating ability, its molecular structure lacks specific binding sites with collagen peptides and cannot form a stable nano-level complex, resulting in the re-aggregation and precipitation of metal ions in the solution. In contrast, the surface carboxylic acid groups of quantum dots and the amino groups of peptide chains achieve efficient nutrient dispersion and slow release through multiple interactions of hydrogen bonds and coordination bonds.

[0046] The replacement of the silk fibroin film (replaced by PVA) reduced the active substance retention rate after 6 months of storage by 28.3%, which is due to the lack of pH-responsive characteristics of the β-sheet conformation in the PVA material. The β-sheet structure (accounting for 55 - 65%) of silk fibroin in the present invention forms a dense barrier during storage, and after application, it undergoes a conformational change triggered by soil pH to achieve controlled release. The homogeneous structure of PVA cannot respond to environmental changes, resulting in particle moisture absorption and irreversible loss of active ingredients. The above results fully prove that the component design of the present invention is not a simple combination of existing technologies, but a systematic innovation based on molecular-level interactions.

[0047] Experiment 2: Description of the key process parameter threshold verification experiment Experiment purpose: To verify the effects of ultraviolet light wavelength, enzymatic hydrolysis temperature, and spray drying temperature on raw material activation, product quality, and structural stability.

[0048] Test groups: Example 1 (normal parameters), Comparative Example 2 (ultraviolet wavelength 310 nm), Comparative Example 4 (enzymatic hydrolysis temperature 50 °C), Comparative Example 6 (spray temperature 200 °C).

[0049] Experimental steps: Measurement of coffee ground porosity and active substances: Take the pretreated coffee ground samples and measure the porosity by mercury intrusion porosimetry; Detect the contents of active substances such as alginic acid and polyphenols in the fermentation broth by HPLC.

[0050] Measurement of the molecular weight distribution of collagen peptides: Analyze the fish scale enzymatic hydrolysate using gel permeation chromatography (GPC), and calculate the proportion of peptides with molecular weights of 500 - 1000 Da (the proportion of target peptides).

[0051] Analysis of the structure of silk fibroin: Determine the proportion of β-sheet structure using Fourier transform infrared spectroscopy (FTIR) (characteristic peak: 1620 - 1640 cm -1 ) Observe the surface morphology of the particles using scanning electron microscopy (SEM).

[0052] Experimental data table: Table 2: Experimental data for verifying key process parameters Summary: The experimental data reveal that when the key process parameters deviate from the set thresholds of the present invention, the raw material activation efficiency, the molecular structure of the product, and the material properties all deteriorate significantly. In Comparative Example 2, the ultraviolet light wavelength was set to 310 nm, resulting in a decrease in the porosity of coffee grounds to 41.2%, much lower than 68.3% in Example 1. This result verifies the irreplaceability of the TiO2 photocatalytic response wavelength in the "synergistic enhancement mechanism of photocatalysis - biorefining" of the present invention - only when the ultraviolet light wavelength is in the range of 360 - 370 nm can sufficient electron-hole pairs be excited to effectively break the lignin - hemicellulose crosslinking network in coffee grounds, providing highly active substrates for subsequent microbial metabolism.

[0053] In Comparative Example 4, the temperature of fish scale enzymatic hydrolysis was increased to 50 °C, and the proportion of target peptides (500 - 1000 Da) dropped sharply to 54.3%, indicating that low-temperature enzymatic hydrolysis (35 - 45 °C) is the core condition for maintaining protease activity and precise control of the product molecular weight. High temperature causes conformational changes in enzyme molecules, resulting in a decrease in the matching degree between their substrate-binding sites and catalytic centers, and unable to achieve directional cleavage of collagen. This phenomenon is closely related to the "enzymatic hydrolysis - quantum dot complexation directional regulation mechanism" of the present invention - peptides with specific molecular weights are the structural basis for constructing stable "peptide - quantum dot" complexes, and the excessive presence of large molecular peptides will disrupt the charge balance at the complexation interface.

[0054] In Comparative Example 6, the spray drying temperature exceeded the limit (constant temperature 200 °C), resulting in a decrease in the proportion of β-sheet structure of silk fibroin to 38.7%, proving that the gradient cooling process (170 - 190 °C → 60 - 80 °C) is crucial for maintaining protein conformation. High temperature not only destroys the hydrogen bond network of silk fibroin but also causes disordered aggregation of molecular chains, losing the pH-responsive property. In contrast, the gradient temperature control strategy of the present invention enables the silk fibroin molecules to be arranged orderly at the gas-liquid interface by dynamically adjusting the drying rate, forming a functional membrane layer with both compactness and elasticity. These data together indicate that the threshold design of process parameters is not an empirical choice but an inevitable result based on molecular interaction mechanisms.

[0055] Experiment 3: Experiment Description for Verifying Synergistic Effect Experiment Purpose: To verify the irreplaceability of the synergistic effect of multiple technical features on the comprehensive yield, storage stability, and function release.

[0056] Test Groups: Example 3 (complete scheme), Comparative Example 1 + 3 + 5 (simultaneously removing the microbial agent + replacing quantum dots with EDTA + replacing silk fibroin with PVA).

[0057] Experimental Steps: Comprehensive Yield Test: Record the raw material consumption rate (g / h) during the fermentation stage; Determine the total organic matter content (ignition method) and total nitrogen content (Kjeldahl method) in the finished product.

[0058] Free Ammonia Concentration Monitoring: Store the finished product in a 30°C incubator and take samples monthly to detect the free ammonia concentration (Nessler's reagent colorimetric method).

[0059] Particle Disintegration Rate Test: Take 1 g of particles and soak them in a pH 6.5 buffer solution (simulating the soil environment), and record the complete disintegration time; After disintegration, determine the concentration of active substances in the solution and calculate the release rate.

[0060] Experimental Data Table: Table 3: Experimental Data for Verifying Synergistic Effect Summary Description: The experimental data show that when the photosensitizing microbial agent, molasses quantum dots, and silk fibroin membrane are simultaneously removed, the comprehensive performance of the product shows a cliff-like decline. The comprehensive yield drops from 89.2% to 63.8%, verifying the close coupling relationship of multiple links in the present invention, namely "photocatalytic pretreatment - microbial metabolism - quantum dot complexation - protein membrane controlled release". The absence of the photosensitizing microbial agent not only affects the decomposition efficiency of coffee grounds but also leads to insufficient substrate supply for nitrogen-fixing bacteria in the dark fermentation stage. Moreover, the ineffective complexation of EDTA with collagen peptides further exacerbates nutrient loss. This cascading failure phenomenon cannot be reflected in single-variable experiments, highlighting the necessity of cross-module synergy.

[0061] After 6 months of storage, the free ammonia concentration in the comparative example group soars to 22.9 ppm, far exceeding 4.3 ppm in Example 3. This result reveals the synergistic antibacterial mechanism of the photosensitizing microbial agent and the silk fibroin membrane - the organic acids generated in the light-driven metabolic pathway and the dense barrier of the β-sheet structure jointly inhibit the proliferation of spoilage bacteria, while the combination of PVA and single strains cannot reproduce this effect. The non-linear growth of ammonia concentration (slow at the beginning and explosive at the end) further proves that the synergistic effect of the present invention can block the vicious cycle of microbial metabolism during storage.

[0062] The granule disintegration time was extended from 18.7 min to 43.5 min, and the active release rate decreased by 27.4%. This indicates that the PVA membrane not only lacks pH responsiveness, but its homogeneous structure also hinders the penetration and diffusion of moisture. In contrast, the synergistic effect of the gradient pore structure (dense outer layer and porous inner layer) of the silk fibroin membrane and the quantum dot-lignin network in Example 3 achieved a dynamic balance of "rapid disintegration - controlled release". This synergistic effect based on molecular interface design cannot be achieved by a simple superposition of existing technologies, thus establishing the inventive step of the present invention.

[0063] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An organic water-soluble fertilizer using natural organic matter as raw materials, characterized in that: By mass, it includes the following components: 20-30 parts of coffee grounds, 15-25 parts of fish scale hydrolyzate, 2-5 parts of photosensitizing agent, 3-8 parts of lignin nanofibers, 1-3 parts of molasses-derived quantum dots, 8-12 parts of silk fibroin film solution, 0.5-2 parts of citric acid, and the balance is deionized water; Wherein, the coffee grounds are pre-treated by nano-TiO2 photocatalysis, and the fish scale hydrolyzate is a collagen peptide solution with a molecular weight of 500-1000Da.

2. The organic water-soluble fertilizer using natural organic matter as raw materials according to claim 1, characterized in that: The photosensitizing bacterial agent includes Rhodospirilla and nitrogen-fixing bacteria, and the volume ratio of the two is 2:1 to 4:

1.

3. The organic water-soluble fertilizer using natural organic matter as raw materials according to claim 1, characterized in that: The particle size of the molasses-derived quantum dots is 3-5 nm, and the surface contains carboxylic acid groups.

4. The organic water-soluble fertilizer using natural organic matter as raw materials according to claim 1, characterized in that: In the silk fibroin membrane solution, the β-folded structure accounts for 55-65% of the total secondary structure of the silk fibroin molecule, the α-helical structure accounts for 10-15% of the total secondary structure of the silk fibroin molecule, and the rest is a random coil structure.

5. A method for preparing an organic water-soluble fertilizer using natural organic matter as raw materials as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1, coffee grounds are impregnated with nano-TiO2 sol and treated with ultraviolet light to obtain a photocatalytic active carrier; S2, fish scales are enzymatically hydrolyzed with a composite protease at low temperature and then ultrafiltered to obtain collagen peptide liquid; S3, aerobically fermenting the product of step S1 and the photosensitized bacterial agent under light, and then adding the product of step S2 and molasses-derived quantum dots for dark fermentation; S4, after the fermentation liquid is coupled with the lignin nanofibers, the silk fibroin membrane solution is added and mixed; S5. The mixed solution is subjected to microfluidic gradient spray drying to obtain organic water-soluble fertilizer particles.

6. The method for preparing an organic water-soluble fertilizer using natural organic matter as raw materials according to claim 5, characterized in that: In the step S1, the concentration of the nano-TiO2 sol is 0.8-1.2wt%, and the ultraviolet light treatment conditions are a wavelength of 360-370nm, a power of 40-60W, and a time of 15-25min.

7. The method for preparing an organic water-soluble fertilizer using natural organic matter as raw materials according to claim 5, characterized in that: In the step S2, the composite protease is alkaline protease and trypsin, the mass ratio is 1.5:1 to 2.5:1, the enzymolysis temperature is 35-45°C, and the time is 4-8h.

8. The method for preparing an organic water-soluble fertilizer using natural organic matter as raw materials according to claim 5, characterized in that: The aerobic fermentation conditions in the S3 step are a light intensity of 4500-5500 lux, a temperature of 25-35° C., and a time of 20-28 h. The dark fermentation conditions in the S3 step are an anaerobic environment, a temperature of 30-40° C., and a time of 10-14 h.

9. The method for preparing an organic water-soluble fertilizer using natural organic matter as raw materials according to claim 5, characterized in that: In the step S4, the coupling reaction is carried out in the presence of a catalyst, wherein the catalyst is p-toluenesulfonic acid, and the added amount is 0.3-0.7% of the total mass of the reaction system.

10. The method for preparing an organic water-soluble fertilizer using natural organic matter as raw materials according to claim 5, characterized in that: In the step S5, the inlet temperature of the microfluidic gradient spray drying is gradually reduced from 170-190° C. to 60-80° C., and the nozzle aperture is reduced from 40-60 μm to 8-12 μm.

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