Liquid organic fertilizer prepared by using waste solution of thioredithromycin and preparation method thereof

Abstract

The present application belongs to the technical field of fertilizer production, and particularly relates to a liquid organic fertilizer prepared from sulfated erythromycin waste liquid and a preparation method thereof. The method comprises the following steps: S1, collecting a mixture of waste mycelium and waste liquid generated after sulfated erythromycin is extracted from sulfated erythromycin fermentation liquid to obtain sulfated erythromycin waste liquid; S2, adjusting the pH of the sulfated erythromycin waste liquid to above 11, mixing the sulfated erythromycin waste liquid with an oxidizing agent under alkaline conditions, and performing oxidative degradation under the action of ultrasonic waves, and then performing heat treatment to obtain a treatment liquid in which antibiotics are inactivated and degraded; and S3, adding a nutrient component to the treatment liquid, uniformly mixing, and adjusting the pH to obtain the liquid organic fertilizer. Through the synergistic combination of alkaline hydrolysis, ultrasonic cell wall breaking, oxidative degradation and heat treatment, the present application completely inactivates bacteria and miscellaneous bacteria, and completely converts the sulfated erythromycin antibiotic into an open-loop degradation product without antibacterial activity, so that the antibiotic residue can be reduced to an undetectable level, and the risk of inducing resistance genes after application is avoided.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer production technology, and in particular relates to a liquid organic fertilizer produced from thioerythromycin waste liquid and its preparation method. Background Technology

[0002] Erythromycin is a key precursor in the synthesis of macrolide antibiotics such as erythromycin. Its fermentation broth, after erythromycin extraction, generates a large amount of waste mycelia and waste liquid. This waste liquid contains abundant organic matter, mycelial proteins, nucleic acids, residual erythromycin, and small amounts of other metabolites. Direct discharge not only wastes organic resources but also poses a risk of antibiotic resistance gene diffusion in the environment due to antibiotic residues. Therefore, converting erythromycin waste liquid into agricultural fertilizer is a reasonable path to achieve its reduction and resource utilization.

[0003] Existing technologies for treating such antibiotic waste mainly employ either high-temperature thermal treatment or room-temperature chemical oxidation. While prolonged high-temperature treatment can inactivate bacteria and degrade some antibiotics, it consumes a lot of energy and results in insufficient release of nutrients from the mycelial cell walls, leading to low bioavailability of the resulting fertilizer. Chemical oxidation alone has limited selectivity in antibiotic degradation, particularly for erythromycin containing a lactone ring structure, often leaving behind intermediates with potential antibacterial activity. Furthermore, while alkaline hydrolysis alone can open the lactone ring, the product may still retain some molecular skeleton. Without subsequent deep oxidation and cell-wall disruption, the mycelial cells in the waste liquid cannot be fully ruptured, preventing the release of intracellular amino acids, nucleotides, and other active substances, thus hindering the full realization of fertilizer effectiveness.

[0004] Therefore, there is an urgent need for a process that can synergistically enhance the effect, completely deactivate antibiotic activity, and simultaneously activate mycelial nutrients. Summary of the Invention

[0005] The main objective of this invention is to provide a liquid organic fertilizer produced from erythromycin waste liquid and its preparation method, so as to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] According to a first aspect of the present invention, a method for producing liquid organic fertilizer using erythromycin waste liquid is provided, comprising the following steps:

[0008] S1. Collect the mixture of waste mycelia and waste liquid produced after extracting sulfonylurea from the sulfonylurea fermentation broth to obtain sulfonylurea waste liquid;

[0009] S2. Adjust the pH of the thioerythromycin waste liquid to above 11, mix it with an oxidant under alkaline conditions, and carry out oxidative degradation under ultrasonic action. Then, heat-treat it at 70-121°C for at least 30 minutes to obtain a treatment solution that inactivates and degrades antibiotics.

[0010] S3. Add nutrients to the treatment solution, mix well, and adjust the pH to 5.5-8.5 to obtain the liquid organic fertilizer.

[0011] In step S2, the alkaline environment causes the lactone ring in the erythromycin molecule to open, generating an intermediate containing carboxyl and hydroxyl groups. Simultaneously, the mycelial cell wall undergoes partial hydrolysis under alkaline conditions. Upon introduction of the oxidant, the aforementioned intermediate and exposed antibiotic molecules undergo chain scission and deep ring opening under oxidation, forming small-molecule organic acids and alcohols without antibacterial activity. The cavitation effect and mechanical shearing action of ultrasonic treatment not only enhance the microscopic mixing of the oxidant and the waste liquid but also directly act on the mycelial cells, promoting further cell wall rupture and mycelial dispersion, accelerating the dissolution of intracellular proteins, nucleic acids, and other substances, and partially degrading them into amino acids, short peptides, and nucleotide fragments in the alkaline and oxidizing environment. Subsequent heat treatment at 70–121°C thoroughly inactivates any remaining production strains and other microorganisms in the waste liquid, while also fully decomposing the remaining oxidant and further converting incompletely degraded organic matter into stable humic precursors. The endogenous amino acids and nucleotide fragments in the treated liquid obtained from this synergistic treatment, together with the added nutrients, constitute the bioactive basis of the liquid organic fertilizer.

[0012] Further, the oxidant used in step S2 is at least one of hydrogen peroxide, persulfate, or persulfate, and its addition amount is 0.5-5% of the weight of the thioerythromycin waste liquid. The ultrasonic treatment frequency is 20-40 kHz, the power density is 0.5-5 W / mL, and the treatment time is 5-30 minutes. Oxidants such as hydrogen peroxide can generate active free radicals in the above-mentioned alkaline medium, which can efficiently attack the ring-opened antibiotic molecules, while the ultrasonic field can promote the generation and mass transfer of free radicals.

[0013] Furthermore, in step S2, after or simultaneously with ultrasonic treatment, the pH of the waste liquid is maintained at 12.0–13.5, and the reaction is carried out at 60–90°C for 20–60 minutes for oxidative degradation. Afterwards, the temperature is raised to 100–121°C to complete the heat treatment, with continuous stirring during the heat treatment to ensure complete decomposition of the residual oxidant. This gradient heating method ensures a suitable reaction temperature during the oxidative degradation stage while avoiding the direct introduction of high temperatures that could lead to excessively rapid decomposition of the oxidant and reduced utilization efficiency.

[0014] Furthermore, after the heat treatment in step S2, catalase or manganese dioxide is added to the system to eliminate residual oxidant. When hydrogen peroxide is used as an oxidant, the addition of catalase can gently and efficiently decompose it into water and oxygen.

[0015] Furthermore, the treatment solution obtained after step S2 contains amino acid and nucleic acid degradation fragments released due to alkaline hydrolysis and ultrasonic disruption of the mycelial cell walls. These fragments, together with the oxidative degradation products, constitute the endogenous bioactive components of the liquid organic fertilizer. These endogenous substances can be directly absorbed and utilized by plants, or stimulate plant root growth, and synergistically enhance fertilizer efficiency in conjunction with exogenous nutrient components.

[0016] Further, in step S3, the added nutrient components include at least one of a nitrogen source, a phosphorus source, and a potassium source, such that the total nutrient content in the final product, calculated as N, P2O5, and K2O, is 2–15 wt%. In addition, humic acid and / or amino acids, and / or trace elements are added in step S3; the trace elements are selected from one or more of zinc, boron, manganese, iron, copper, and molybdenum. Humic acid and amino acids can further increase soil organic matter, improve fertilizer physical properties, and provide complexation sites.

[0017] Furthermore, when the phosphorus source added in step S3 includes phosphoric acid, the phosphoric acid not only supplements phosphorus nutrition, but also reacts with alkaline substances and polyvalent metal ions in the treatment solution simultaneously when adjusting the pH, forming a phosphate buffer system and chelating calcium, magnesium and other ions to prevent precipitation of fertilizer during storage and improve the stability of liquid fertilizer.

[0018] Furthermore, in step S3, a suspension stabilizer and an antifreeze agent are added to obtain a suspension-type liquid organic fertilizer. The suspension stabilizer is preferably bentonite, xanthan gum, or magnesium aluminum silicate, added at a rate of 0.1–2 wt%; the antifreeze agent is preferably ethylene glycol or glycerol, added at a rate of 1–5 wt%. This results in a product with uniform suspension, suitable for long-term storage and transportation.

[0019] According to a second aspect of the present invention, the present invention also provides a liquid organic fertilizer prepared by any of the methods described above. This liquid organic fertilizer has a pH value of 5.5–8.5, an organic matter content of not less than 20 wt%, an antibiotic residue of not more than 0.01 mg / L, and contains ring-opening degradation products of erythromycin formed by alkaline oxidation-ultrasound-heat treatment, which have no antibacterial activity. These ring-opening degradation products specifically include, but are not limited to, a series of dicarboxylic acids and hydroxy acids generated by the cleavage of erythromycin lactone rings, and are safe for the environment and microorganisms. Preferably, the product has a viscosity of 200–2000 mPa·s and a density of 1.05–1.20 g / mL at 25°C, facilitating application. More preferably, the total bacterial count in the product is less than 1 × 10⁻⁶. 5The concentration of CFU / mL was low, E. coli was not detected, and it did not contain any live erythromycin-producing bacteria. Furthermore, when this liquid organic fertilizer was diluted 200 times and used in a seed germination test of Chinese cabbage, the seed germination index was greater than 90%, which fully demonstrates its high safety for crops.

[0020] Compared with the prior art, the advantages of the present invention include:

[0021] (1) This invention provides a liquid organic fertilizer made from erythromycin waste liquid and its preparation method. Through the synergistic combination of alkaline hydrolysis, ultrasonic cell disruption, oxidative degradation and heat treatment, the bacteria and miscellaneous bacteria are completely inactivated, and the erythromycin antibiotic is completely converted into an open-ring degradation product without antibacterial activity. The antibiotic residue can be reduced to undetectable level, avoiding the risk of inducing resistance genes after application.

[0022] (2) The present invention uses ultrasound and alkaline hydrolysis to jointly cause the cell walls of mycelium to rupture, releasing the proteins, nucleic acids, etc. contained therein, and partially degrading them into amino acids and nucleotide fragments, increasing the active organic matter of the fertilizer and the nutrients that can be quickly absorbed by plants, thus significantly improving the fertilizer efficiency of liquid organic fertilizer.

[0023] (3) The heat treatment of the present invention can achieve thorough sterilization and decompose residual oxidants, avoiding oxidative stress on crop roots. At the same time, the heat treatment accelerates the humification process of organic materials, making the product more stable.

[0024] (4) The suspended liquid organic fertilizer obtained by adding suspension stabilizer and antifreeze has good fluidity, suspension stability and low temperature storage properties, and is suitable for large-scale mechanized fertilization.

[0025] (5) The preparation process of this invention is mild and controllable, does not introduce harmful chemicals, realizes the complete resource utilization of antibiotic waste liquid, and has significant environmental and economic benefits. Detailed Implementation

[0026] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0027] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0028] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials used in the following embodiments are commercially available.

[0029] This invention provides a method for producing liquid organic fertilizer from erythromycin waste liquid, comprising the following steps:

[0030] S1. Collect the mixture of waste mycelia and waste liquid produced after extracting erythromycin from the erythromycin fermentation broth to obtain erythromycin waste liquid. The collected erythromycin waste liquid is a mixture of distillation residue and mycelia remaining after the erythromycin fermentation broth has been extracted with organic solvents or resin adsorption to obtain the target product. This waste liquid is acidic (usually pH 3.5–5.0) and contains 3–8 wt% wet mycelia, residual erythromycin and a small amount of erythromycin-related substances, unused culture medium organic matter, inorganic salts, and microbial metabolic byproducts. Its organic matter dry basis content can be as high as 60–80%, making it a potential source of organic fertilizer. However, it also carries live bacteria and antibiotics, posing an environmental risk if used directly in agriculture.

[0031] S2. Adjust the pH of the thioerythromycin waste liquid to above 11, mix it with an oxidant under alkaline conditions, and oxidize and degrade it under ultrasonic action. Then, heat-treat it at 70-121°C for at least 30 minutes to obtain a treatment liquid that inactivates and degrades antibiotics, thereby achieving complete passivation of antibiotics and full release of mycelial nutrients.

[0032] S3. Add nutrients to the treatment solution, mix thoroughly, and adjust the pH to 5.5–8.5 to obtain the liquid organic fertilizer. Prepare the treatment solution into a finished liquid organic fertilizer. Adding nitrogen, phosphorus, potassium, and other nutrients ensures the total nutrient content meets commercial fertilizer standards. Humic acid, amino acids, and trace elements can be introduced as needed to meet the needs of certain crops or improve soil. Adjusting the pH to a slightly acidic to neutral range of 5.5–8.5 ensures fertilizer storage stability and compatibility with most pesticides, while also being suitable for the crop rhizosphere environment. When phosphoric acid is used as the phosphorus source, it can form a phosphate buffer system during pH adjustment and chelate with polyvalent metal ions in the treatment solution to prevent precipitation, further ensuring the uniformity and ease of application of the liquid fertilizer.

[0033] To better understand the technical solution of the present invention, the following detailed discussion is provided in conjunction with specific embodiments.

[0034] Example 1

[0035] This embodiment provides a method for producing liquid organic fertilizer using erythromycin waste liquid, including the following steps:

[0036] S1. Take the waste liquid after extracting thioerythromycin from a certain erythromycin production enterprise. It contains about 4.8 wt% wet mycelium, pH 4.5, and thioerythromycin residue of about 48 mg / L.

[0037] S2. Add sodium hydroxide solution to the waste liquid to adjust the pH to 11.2, heat and maintain at 60℃, add 0.5% (by weight) of 30% hydrogen peroxide solution, and simultaneously start the ultrasonic generator for ultrasonic treatment at a frequency of 20 kHz, a power density of 0.5 W / mL, and a treatment time of 5 minutes. After ultrasonication, continue to maintain the temperature at 60℃ with stirring for oxidative degradation, and the reaction time is 20 minutes. Then, raise the temperature of the solution to 70℃ and maintain it for 30 minutes with continuous stirring. After heat treatment, cool to 50℃, add 0.05 g / L catalase (activity 2000 U / mg), and stir for 20 minutes to remove residual hydrogen peroxide, obtaining the treated solution.

[0038] S3. Add urea, potassium dihydrogen phosphate, and potassium sulfate to the treatment solution to adjust the total N+P2O5+K2O to 12 wt% (N 6.5%, P2O5 3.5%, K2O 2%). Then add 2.5 wt% potassium humate, 1.0 wt% compound amino acid powder, and a mixture of trace elements (added in the form of zinc sulfate heptahydrate, boric acid, and manganese sulfate monohydrate, etc.) to make the zinc content in the finished product 0.10%, boron 0.05%, and manganese 0.03%. Adjust the pH of the system to 6.5 with food-grade phosphoric acid and replenish the phosphorus source. Finally, add 1.0 wt% bentonite as a suspension stabilizer and 3.0 wt% ethylene glycol as an antifreeze agent, and mix at 3000 rpm for 20 minutes using a high-shear disperser to obtain a suspension liquid organic fertilizer.

[0039] The product test results were as follows: pH 6.5, organic matter content 21.8 wt%, total nutrients 12.0 wt%; viscosity (25℃) 880 mPa·s, density 1.10 g / mL; HPLC-MS / MS did not detect erythromycin or erythromycin-related substances (detection limit 0.005 mg / L); total bacterial count 3.5 × 10⁻⁶. 4 CFU / mL, E. coli not detected, no viable bacterial growth in streak plate culture. The product was diluted 200 times and used in a germination test of Chinese cabbage seeds, with a germination index of 91.3%.

[0040] Example 2

[0041] This embodiment provides a method for producing liquid organic fertilizer using erythromycin waste liquid, including the following steps:

[0042] S1. Take the waste liquid after extracting thioerythromycin from a certain erythromycin production enterprise. It contains about 4.8 wt% wet mycelium, pH 4.5, and thioerythromycin residue of about 48 mg / L.

[0043] S2. Adjust the pH of the waste liquid to 12.5 with sodium hydroxide, heat and maintain at 80°C, add 2.0% (by weight) of a 30% hydrogen peroxide solution, and simultaneously start ultrasonic treatment at a frequency of 28 kHz, a power density of 1.5 W / mL, and a treatment time of 25 minutes. After ultrasonic treatment, continue to maintain the temperature at 80°C with stirring for 15 minutes for oxidation and degradation (total oxidation and degradation time 40 minutes). Then, raise the temperature of the liquid to 121°C and maintain it for 30 minutes with continuous stirring. After heat treatment, cool to 50°C, add 0.1 g / L catalase, and stir for 20 minutes to remove residual hydrogen peroxide, obtaining the treated liquid. S3. Using the same nutrient components and additive formulation process as in Example 1, obtain a suspended liquid organic fertilizer. Product test results: pH 6.5, organic matter content 23.1 wt%, total nutrients 12.2 wt%; viscosity 980 mPa·s, density 1.11 g / mL; no thioerythromycin or erythromycin-related substances detected; total bacterial count 2.4 × 10⁻⁶. 4 CFU / mL, E. coli not detected, no viable bacteria. Germination index 95.2%.

[0044] Example 3 This example provides a method for producing liquid organic fertilizer using erythromycin waste liquid, including the following steps:

[0045] S1. Waste liquid from the extraction of thioerythromycin by an erythromycin production enterprise was collected. It contained approximately 4.8 wt% wet mycelium, had a pH of 4.5, and a residual thioerythromycin concentration of approximately 48 mg / L. S2. The pH of the waste liquid was adjusted to 13.5 with potassium hydroxide. The liquid was heated and maintained at 90°C. A 30% hydrogen peroxide solution (5.0% by weight of the waste liquid) was added, and ultrasonic treatment was initiated simultaneously at a frequency of 40 kHz and a power density of 5.0 W / mL for 30 minutes. After ultrasonic treatment, the liquid was kept at 90°C with stirring for 30 minutes to oxidize and degrade (total oxidative degradation time 60 minutes). The liquid was then heated to 121°C and maintained for 30 minutes with continuous stirring. After heat treatment, the liquid was cooled to 50°C, and 0.2 g / L catalase was added. The mixture was stirred for 30 minutes to eliminate residual hydrogen peroxide, yielding the treated liquid. S3. Using the same nutrient components and additive formulation process as in Example 1, a suspended liquid organic fertilizer was obtained. Product test results: pH 6.4, organic matter content 23.5 wt%, total nutrients 12.1 wt%; viscosity 1020 mPa·s, density 1.12 g / mL; no antibiotic residues detected; total bacterial count 1.9 × 10⁻⁶. 4 CFU / mL, E. coli not detected, no viable bacteria. Germination index 93.8%.

[0046] Comparative Example 1

[0047] High-temperature heat treatment was used only, without alkaline hydrolysis, oxidation, or ultrasound: the waste liquid was treated at 121°C for 40 minutes, and other steps were the same as in Example 1, S3. The resulting product had an antibiotic residue of 12 mg / L, mycelial sedimentation and stratification, low organic matter utilization, and a germination index of only 65%.

[0048] Comparative Example 2

[0049] Using only alkaline hydrolysis and oxidation, without ultrasonic and high-temperature heat treatment: the waste liquid was adjusted to pH 12.5, 2.0% hydrogen peroxide was added, and oxidation was carried out at 80℃ for 40 minutes, then directly proceeded to step S3. The resulting product had a total bacterial count exceeding 10. 7 With a concentration of CFU / mL, containing live bacteria, and antibiotic residues of 0.8 mg / L, it is not suitable for use as agricultural fertilizer.

[0050] Comparative Example 3

[0051] After alkaline hydrolysis, oxidation, and sonication, the product was directly formulated without enzymatic or manganese dioxide removal of residual oxidants: Step S2 of Example 2 was followed, but the catalase treatment was skipped after heat treatment, and the process proceeded directly to step S3. The product caused browning of the seed radicle and a decrease in the germination index to 55%, indicating that residual oxidants damaged the crop.

[0052] After treatment in Comparative Examples 1-3, nutrients, suspending agents, and antifreeze agents were added according to the same formula to adjust the total nutrients to 12wt% and the pH to 6.5±0.2.

[0053] In the above examples and comparative examples, the thioerythromycin waste liquid was derived from fresh waste liquid extracted by erythromycin production enterprises. Key indicators included: pH 4.5, wet mycelial content 4.8 wt%, thioerythromycin residue 48.2 mg / L, organic matter content (dry basis) 72.4%, and total bacterial count 2.6 × 10⁻⁶. 7 CFU / mL, containing live erythromycin-producing bacteria.

[0054] Detection methods and instruments: Antibiotic residues were determined by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS, detection limit 0.005 mg / L); total bacterial count and Escherichia coli were determined according to GB / T 19524.1 and GB / T 19524.2; seed germination index was determined according to GB / T 3543.4, using Chinese cabbage seed extract culture and distilled water as control; organic matter was determined according to NY / T 1976; total amino acids were determined by ninhydrin colorimetric method; viscosity was determined by rotational viscometer at 25℃; suspension stability was expressed as bottom sedimentation rate after standing for 30 days.

[0055] The results are shown in Table 1.

[0056] Table 1 ;

[0057] In the table above, "—" indicates that the steady-state viscosity could not be measured due to severe stratification or microbial gas production. "Amino acid increment in the treated liquid" refers to the increase in the treated liquid obtained in step S2 compared to the original waste liquid (amino acid content 85 mg / L), reflecting the mycelial cell disruption and release.

[0058] As shown in Table 1, the antibiotic residues in Examples 1-3 of this invention were all below the detection limit, the products contained no live bacteria or Escherichia coli, and the seed germination index was >90%, indicating safety for crops. With increased cell wall disruption (increased ultrasonic / alkali hydrolysis intensity), the amino acid increment increased from 312 mg / L to 503 mg / L, the organic matter content remained stable above 21.8%, and the suspension stability was good (sedimentation rate ≤2.1%), indicating that harmlessness can be achieved at the lower limit of the process, while medium-to-high parameters further enhance nutrient release and product stability.

[0059] Comparative Example 1 relied solely on heat treatment, resulting in significant antibiotic residues, weak mycelial cell disruption, a germination index of only 65.3%, and severe sedimentation and stratification, rendering it unsuitable as a qualified commercial fertilizer. Comparative Example 2 lacked ultrasonic and high-temperature inactivation; although alkaline hydrolysis and oxidation released a relatively large amount of amino acids, it suffered from excessive levels of miscellaneous bacteria and high antibiotic residues, rendering the seeds almost unable to germinate normally and thus having no practical value. Comparative Example 3 confirmed that residual oxidants significantly toxicized the seed roots, drastically reducing the germination index to 54.7%.

[0060] As can be seen from Examples 1-3 and the comparative examples, within the parameter range, the combined process of the present invention can achieve complete antibiotic degradation, complete inactivation of bacteria and miscellaneous bacteria, and efficient release of mycelial nutrients, with excellent product safety and fertilizer efficacy. It is particularly noteworthy that even when using the lower limit parameters (low oxidant dosage, short-duration ultrasound, and lower temperature), the synergistic effect still ensures the treatment effect, while the upper limit parameters result in faster and more thorough treatment, demonstrating the broad adaptability of the process.

[0061] The above descriptions are merely some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for producing liquid organic fertilizer from erythromycin waste liquid, characterized in that, Includes the following steps: S1. Collect the mixture of waste mycelia and waste liquid produced after extracting sulfonylurea from the sulfonylurea fermentation broth to obtain sulfonylurea waste liquid; S2 adjusts the pH of the thioerythromycin waste liquid to above 11, mixes it with an oxidant under alkaline conditions, and oxidizes and degrades it under ultrasonic action. Then, it is heat-treated at 70-121°C for at least 30 minutes to obtain a treatment solution that inactivates and degrades antibiotics. S3 adds nutrient components to the treatment solution, mixes them evenly, and adjusts the pH to 5.5-8.5 to obtain the liquid organic fertilizer.

2. The method according to claim 1, characterized in that, The oxidant in step S2 is at least one of hydrogen peroxide, persulfate, or persulfate, and its addition amount is 0.5-5% of the weight of the thioerythromycin waste liquid; the frequency of the ultrasonic treatment is 20-40 kHz, the power density is 0.5-5 W / mL, and the treatment time is 5-30 minutes.

3. The method according to claim 1, characterized in that, In step S2, after or simultaneously with ultrasonic treatment, the pH of the waste liquid is maintained at 12.0 to 13.5, and the reaction is carried out at 60 to 90°C for 20 to 60 minutes for oxidative degradation. Then, the temperature is raised to 100 to 121°C to complete the heat treatment, and the mixture is continuously stirred during the heat treatment to ensure that the residual oxidant is fully decomposed.

4. The method according to claim 1, characterized in that, In step S2, after the heat treatment is completed, catalase or manganese dioxide is added to the system to eliminate residual oxidants.

5. The method according to claim 1, characterized in that, The treatment liquid described in step S2 contains amino acids and nucleic acid degradation fragments released due to alkaline hydrolysis and ultrasonic disruption of the mycelial cell walls. These fragments, together with the oxidative degradation products, constitute the endogenous bioactive components of the liquid organic fertilizer.

6. The method according to claim 1, characterized in that, The nutrient components in step S3 include at least one of nitrogen source, phosphorus source and potassium source, so that the total nutrient content of the liquid organic fertilizer prepared, calculated as N, P2O5 and K2O, is 2 to 15 wt%; humic acid and / or amino acids, and / or trace elements are also added in step S3, wherein the trace elements are selected from one or more of zinc, boron, manganese, iron, copper and molybdenum.

7. The method according to claim 6, characterized in that, The phosphorus source added in step S3 includes phosphoric acid, which simultaneously forms a buffer system and chelates polyvalent metal ions in the treatment solution when adjusting the pH.

8. The method according to claim 1, characterized in that, In step S3, a suspension stabilizer and an antifreeze agent are added to obtain a suspension-type liquid organic fertilizer; the suspension stabilizer is bentonite, xanthan gum or magnesium aluminum silicate, and the addition amount is 0.1-2 wt%; the antifreeze agent is ethylene glycol or glycerol, and the addition amount is 1-5 wt%.

9. A liquid organic fertilizer prepared by the method according to any one of claims 1-8, characterized in that, The liquid organic fertilizer has a pH value of 5.5 to 8.5, an organic matter content of not less than 20 wt%, an antibiotic residue of not more than 0.01 mg / L, and contains a ring-opening degradation product of thioerythromycin with no antibacterial activity formed by alkaline oxidation-ultrasound-heat treatment.

10. The liquid organic fertilizer according to claim 9, characterized in that, The liquid organic fertilizer has a viscosity of 200–2000 mPa·s at 25℃, a density of 1.05–1.20 g / mL, and a total bacterial count of less than 1×10⁻⁶. 5 CFU / mL, no E. coli detected, no live erythromycin-producing bacteria, and when this liquid organic fertilizer was diluted 200 times and used in a germination test of Chinese cabbage seeds, the seed germination index was greater than 90%.