Organic water-soluble fertilizer with medium trace elements chelated by feather acidolysis mother liquor and preparation method of organic water-soluble fertilizer

Abstract

The invention belongs to the technical field of fertilizers, and particularly relates to an organic water-soluble fertilizer of feather acidolysis mother liquor chelated medium trace elements and a preparation method of the organic water-soluble fertilizer. (2) chelating step by step; and (3) performing in-situ stabilization to obtain the organic water-soluble fertilizer with the feather acidolysis mother liquor chelated with the trace elements. According to the scheme, through the full-chain process design from mother liquor pretreatment and chelating sequence reconstruction to in-situ stabilization, the problems that in the prior art, sulfur-containing amino acid is prone to oxidation, colloidal impurities interfere with the chelating efficiency and the stability of a finished product is insufficient are solved, and the resource utilization value of the feather acidolysis mother liquor can be remarkably improved; the requirement of the national standard (NY 1106-2010) of organic water-soluble fertilizer on the shelf life is met.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizers, and in particular relates to an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor and a preparation method thereof. Background Art

[0002] The resource utilization of feathers is an important area of ​​agricultural waste management. Acid hydrolysis of feathers, rich in amino acids (total content ≥80 g / L) and natural chelating components, is considered an ideal raw material for organic water-soluble fertilizers. However, this system has inherent drawbacks: sulfur-containing amino acids, comprising up to 12-18% of the total volume (primarily cystine and cysteine), can easily trigger chain oxidation reactions during the chelation process. Furthermore, colloidal impurities (molecular weight 1-50 kDa) produced by acid hydrolysis compete with the target amino acids for metal ions, significantly reducing chelation efficiency.

[0003] Existing processes generally adopt a strategy of step-by-step chelation combined with antioxidant addition, but face three challenges: First, the traditional activated carbon-membrane filtration combination has limited separation effect on peptide impurities with similar molecular weight (such as 5-10 kDa fragments), resulting in a loss of more than 20% of effective amino acids (Liu et al., 2022); Second, although the chelation order of "Fe-Cu-Zn-Mn" is consistent with the metal stability constant ranking, it ignores the effect of sulfur-containing amino acids on Cu 2+ / Fe 3+ preferential coordination tendency - this combination activates an oxygen free radical chain reaction, resulting in a chelate decomposition rate of more than 40% after accelerated storage at 40°C for 30 days (Chen et al., 2020); thirdly, exogenous antioxidants (such as ascorbic acid) may undergo self-oxidation reactions in the presence of transition metals, while the synthetic chelating agent EDTA interferes with the bioavailability of trace elements.

[0004] Of particular concern is the high isoelectric point of cystine in feather stock (pI 5.0) that overlaps significantly with the typical chelation pH window (4.0-6.0), which can cause protein flocculation and subsequent equipment clogging. Despite industry attempts to introduce inert atmospheres or stabilizers (such as sorbitol), the oxidative half-life of sulfur-containing chelates remains less than 30 days, far below the six-month shelf life required by the national standard for organic water-soluble fertilizers (NY1106-2010).

[0005] This presents a technological gap: How can we selectively activate the chelation potential of sulfur-containing amino acids while simultaneously blocking their oxidation pathways? Can the "impurities" in the mother liquor be converted into stabilization resources? Existing technologies have yet to offer a systematic solution. Therefore, it is imperative to develop an innovative, comprehensive process from mother liquor pretreatment, chelation sequence reconstruction, to in-situ stabilization, to maximize the value of feather acid hydrolysis mother liquor. Summary of the Invention

[0006] To solve the above problems, the present invention provides an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor and a preparation method thereof. Through a full-chain process design from mother liquor pretreatment, chelation sequence reconstruction to in-situ stabilization, the problems in the prior art such as the easy oxidation of sulfur-containing amino acids, the interference of colloidal impurities with chelation efficiency, and the insufficient stability of the finished product are solved. This method can significantly improve the resource utilization value of feather acid hydrolysis mother liquor and meet the shelf life requirements of the national standard for organic water-soluble fertilizers (NY 1106-2010).

[0007] To achieve the above object, the technical solution of the present invention is: An organic water-soluble fertilizer containing trace elements chelated in feather acid hydrolysis mother liquor. The fertilizer is prepared from the feather acid hydrolysis mother liquor through specific pretreatment, step-by-step chelation and in-situ stabilization. The fertilizer is characterized in that the metal ions in the fertilizer form stable chelates with amino acids, and the macromolecular components in the mother liquor are converted into peptides with stabilizing function. The decomposition rate of the chelate after accelerated storage at 40°C for 30 days is less than 10%.

[0008] The organic water-soluble fertilizer of feather acid hydrolysis mother liquor chelated with trace elements disclosed in the present invention has obvious distinguishing features compared with the prior art. In the prior art, direct use of feather acid hydrolysis mother liquor will result in sulfur-containing amino acids preferentially coordinating Cu 2+ / Fe 3+ , triggering an oxygen free radical chain reaction, resulting in a decrease in the stability of the chelate; at the same time, the traditional activated carbon-membrane filtration combination is difficult to effectively separate peptide impurities with similar molecular weights, resulting in the loss of effective amino acids. The present invention blocks the oxidation pathway of sulfur-containing amino acids through the directional regulation of sodium bisulfite, allowing them to preferentially participate in metal ion chelation, thereby activating their chelation potential. In addition, the mother liquor is graded using an ultrafiltration membrane with a molecular weight cutoff of 1-3 kDa, which not only removes interfering colloidal impurities with a molecular weight greater than 3 kDa, but also converts these impurities into large molecular peptides with stabilizing functions. Through the enzymatic hydrolysis of papain, the large molecular impurities are further degraded into small molecular peptides of 1-3 kDa. These peptides synergize with tannic acid in the subsequent self-assembly process to form a stable coating structure, which significantly improves the antioxidant properties of the chelate.

[0009] Specifically, the present invention achieves the above-mentioned objectives through the following steps: Step (1): Pretreatment of mother liquor After decolorizing the feather acid hydrolysis mother liquor with activated carbon, 0.5-1.5 wt% sodium bisulfite is added and treated at 45-55°C for 20-40 minutes. The mother liquor is then filtered through an ultrafiltration membrane with a molecular weight cutoff of 1-3 kDa. The role of sodium bisulfite at this stage is to reduce the oxidation tendency of sulfur-containing amino acids through reductive regulation while retaining their chelating activity. The use of an ultrafiltration membrane enables the precise separation of different molecular weight components in the mother liquor, ensuring high retention of effective amino acids while removing interfering impurities.

[0010] Step (2): Stepwise chelation Under the protection of an inert atmosphere throughout the process, the pH value of the mother liquor is adjusted in sequence and zinc salt, iron salt, copper salt and manganese salt solutions are added for step-by-step chelation. The specific operation is as follows: Step (a) adjusting the pH to 3.0-3.5, adding zinc glycinate pre-chelate, and stirring the reaction for 30-45 minutes; Step (b) adjusting the pH to 4.0-4.5, adding an iron salt solution, and reacting for 30-60 minutes; Step (c) adjusting the pH to 4.5-5.0, adding a copper salt solution, and reacting for 20-40 minutes; Step (d) Adjust the pH to 5.5-6.0, add a manganese salt solution, and react for 30-50 minutes.

[0011] The design of step-by-step chelation is based on the difference in coordination ability between metal ions and amino acids and the precise control of pH window. 2+ The competitive coordination with sulfur-containing amino acids improves the chelation efficiency. The inert atmosphere protection effectively inhibits the generation of oxygen free radicals and prevents sulfur-containing amino acids from 2+ / Fe 3+ The iron salt is ferrous sulfate. To avoid the oxidizing property of iron ions, 0.1-0.3 wt% L-ascorbic acid can be added to the iron salt solution to prevent Fe 2+ Oxidation, the copper salt is basic copper carbonate, and the copper salt is pre-dispersed in a triethanolamine aqueous solution (mass concentration 5-10%) before addition to improve wettability.

[0012] Step (3): In situ stabilization 0.5-2 wt% feather hydrolyzed polypeptides and 0.05-0.1 wt% tannic acid are added to the chelating system and reacted at 50-60°C for 10-20 minutes. The solution is then concentrated to a solids content of ≥25%, cooled, and the pH adjusted to 4.0-5.5 to produce an organic water-soluble fertilizer containing trace elements chelated from the feather hydrolyzed liquor. The feather hydrolyzed polypeptides, obtained through papain enzymatic hydrolysis, have a molecular weight of 1-3 kDa and exhibit excellent biocompatibility and antioxidant properties. Tannic acid synergizes with the polypeptides through hydrogen bonding and hydrophobic interactions, forming a stable coating that further enhances the antioxidant capacity of the chelate.

[0013] Preferably, the feather acid hydrolysis mother liquor in step (1) must simultaneously meet the following conditions: total amino acid content ≥80 g / L, sulfur-containing amino acids ≥12 wt% (calculated as cysteine ​​+ cystine), and ultrafiltration retentate (3 kDa) ≤8 wt%. These conditions ensure the raw material quality of the mother liquor and provide a basic guarantee for subsequent processes.

[0014] Preferably, before the sodium bisulfite treatment in step (1), the pH of the mother liquor is adjusted to 2.5-3.5 using citric acid. The introduction of citric acid not only lowers the pH of the mother liquor but also reduces the nonspecific binding of metal ions to sulfur-containing amino acids through chelation, thereby improving the subsequent sodium bisulfite reduction efficiency and reducing the oxidation tendency of sulfur-containing amino acids.

[0015] As a preference, the amount of zinc glycinate pre-chelate added in step (2) is based on the amount of Zn 2+ The molar ratio of the free -SH groups in the mother liquor is 1:(1.2-1.5); The metal ion molar ratio satisfies: Zn:(Fe+Cu) = (1.5-3.0):1, and M Fe :M Cu The ratio is 2-4:1, and the total metal ion addition amount is ≤6.5 mol% (based on the total amount of amino acids in the mother liquor). This ratio design ensures that Zn 2+ Sufficient coordination with sulfur-containing amino acids while avoiding excessive Zn 2+ Interference with the chelation of other metal ions.

[0016] As a preference, step (2) is protected by nitrogen throughout the process, and the reaction temperature is 48-52°C. Nitrogen protection effectively isolates oxygen and prevents sulfur-containing amino acids from 2+ / Fe 3+ The oxidation reaction occurs in the presence of , while maintaining the stability of the reaction system.

[0017] Preferably, the feather hydrolyzed polypeptide in step (3) is obtained by the following method: taking the macromolecular fraction (3 kDa) retained by ultrafiltration in step (1), adding 0.5-1.5 wt% of papain, and performing enzymatic hydrolysis at pH 6.0-7.0 and 50-55°C for 1-3 hours, inactivating the enzyme, and collecting the 1-3 kDa peptide fragment by ultrafiltration. Papain is selected based on its high efficiency in degrading macromolecular proteins, and the molecular weight distribution of the enzymatic hydrolysis product meets the requirements of subsequent self-assembly.

[0018] Preferably, after the reaction in step (3), a composite antioxidant is added: 0.05-0.1 wt% of sodium L-ascorbate, 0.02-0.05 wt% of sodium thiosulfate, and 0.005-0.01 wt% of tocopherol (added in the form of an aqueous dispersion). The composite antioxidant further enhances the antioxidant properties of the chelate through a synergistic effect of multiple mechanisms, thereby extending the shelf life.

[0019] Preferably, the method further comprises a calcium / magnesium chelation step: after step (2) (d), the pH is adjusted to 6.0-6.5, and calcium gluconate and magnesium citrate are added, with the total amount of calcium and magnesium ions being ≤ 2.0 mol% of the total amount of amino acids. The introduction of calcium / magnesium not only enriches the nutrient content of the fertilizer, but also further stabilizes the chelation system through competitive coordination.

[0020] Preferably, 2-4 wt% sorbitol and 1-2 wt% trehalose are added after concentration, and the mixture is stored in a brown, light-proof container at ≤25°C. The addition of sorbitol and trehalose reduces the impact of the external environment on the chelate through a physical barrier effect, while maintaining the water balance of the system.

[0021] Compared with the prior art, the present invention has the following advantages: 1. The present invention successfully activates the chelation potential of sulfur-containing amino acids through the directional regulation of sodium bisulfite, while simultaneously blocking their oxidation pathways, significantly improving chelation efficiency and stability. Ultrafiltration classification and enzymatic conversion technologies are used to convert macromolecular impurities in the mother liquor into peptides with stabilization functions, thus realizing resource utilization of waste. Through step-by-step chelation and in-situ stabilization design, combined with the synergistic effects of inert atmosphere protection and compound antioxidants, the shelf life of the chelate is significantly extended, meeting the six-month shelf life requirement of the national standard for organic water-soluble fertilizers (NY 1106-2010).

[0022] 2. The process of the present invention is simple, the raw materials are widely available, and it is suitable for large-scale production, providing a new way for the high-value utilization of agricultural waste. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Overall embodiment

[0024] A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor is decolorized with activated carbon, and the pH of the mother liquor is adjusted to 2.5-3.5 with citric acid. 0.5-1.5 wt% of sodium bisulfite is added and the mother liquor is treated at 45-55°C for 20-40 min. The mother liquor is filtered through an ultrafiltration membrane with a molecular weight cutoff of 1-3 kDa to obtain the mother liquor. The mother liquor must also meet the following requirements: total amino acid content ≥ 80 g / L; sulfur-containing amino acids account for ≥ 12 wt% of cysteine ​​+ cystine; and the 3 kDa ultrafiltration retentate accounts for ≤ 8 wt% Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48-52°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0-3.5, add zinc salt solution, and stir to react for 30-45 minutes; the zinc salt is glycine zinc pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of the metal ions to the free -SH groups in the mother liquor is 1:(1.2-1.5); the molar ratio of the metal ions satisfies: Zn:(Fe+Cu) = (1.5-3.0):1, and M Fe :M Cu The ratio is 2-4:1, and the total amount of metal ions added is ≤6.5 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0-4.5, adding an iron salt solution, and reacting for 30-60 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5-5.0, adding a copper salt solution, and reacting for 20-40 minutes; the copper salt is basic copper carbonate; Step (d) adjusting the pH to 5.5-6.0, adding a manganese salt solution, and reacting for 30-50 minutes; the manganese salt is manganese sulfate; adjusting the pH to 6.0-6.5, adding calcium gluconate and magnesium citrate, and the total amount of calcium and magnesium ions is ≤ 2.0 mol% of the total amount of amino acids; Step (3) In situ stabilization: The mother liquor after chelation in step (2) is taken as unit 1, 0.5-2wt% of feather hydrolyzed polypeptide and 0.05-0.1wt% of tannic acid are added, and the mixture is reacted at 50-60°C for 10-20min, and a compound antioxidant is added: 0.05-0.1wt% of L-sodium ascorbate + 0.02-0.05wt% of sodium thiosulfate; 0.005-0.01wt% of tocopherol (added in the form of an aqueous dispersion), and then concentrated to a solid content of ≥25%. After concentration, 2-4wt% of sorbitol and 1-2wt% of trehalose are added, and the mixture is cooled to adjust the pH to 4.0-5.5. The mixture is stored in a brown light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements in the feather acid hydrolysis mother liquor; Feather hydrolyzed polypeptides are obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5-1.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0-7.0 and 50-55° C. for 1-3 h; and collecting 1-3 kDa peptides by ultrafiltration after inactivation of the enzyme. Example 1

[0025] A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0026] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0027] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme. Example 2

[0028] A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 3.0 with citric acid. 1.0 wt% sodium bisulfite was added and the mixture was treated at 50°C for 30 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 2 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0029] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature 50°C, the following steps were carried out in the mother liquor: Step (a) adjust the pH to 3.2, add zinc salt solution, and stir to react for 35 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.3; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 2.0:1, and MFe:MCu is 3:1, and the total metal ion addition amount is ≤5.5 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.2, adding an iron salt solution, and reacting for 45 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.7, adding a copper salt solution, and reacting for 30 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.7, a manganese salt solution is added, and the reaction is carried out for 40 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.2, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.5 mol% (based on the total amount of amino acids in the mother liquor).

[0030] Step (3) In situ stabilization: 1.0 wt% of feather hydrolyzed polypeptide and 0.07 wt% of tannic acid were added, reacted at 55°C for 15 minutes, and a compound antioxidant comprising 0.07 wt% of sodium L-ascorbate and 0.03 wt% of sodium thiosulfate and 0.007 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 3 wt% of sorbitol and 1.5 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.5, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements in the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 1.0 wt% of papain and performing enzymatic hydrolysis at pH 6.5 and 52°C for 2 h; and collecting the 2 kDa peptide fragment by ultrafiltration after inactivation of the enzyme. Example 3

[0031] A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 3.5 with citric acid. 1.5 wt% sodium bisulfite was added and the mixture was treated at 55°C for 40 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 3 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0032] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature was 52°C, and the following steps were carried out in the mother liquor: Step (a) adjust the pH to 3.5, add zinc salt solution, and stir to react for 45 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.5; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 3.0:1, and MFe:MCu is 4:1, and the total metal ion addition amount is ≤6.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.5, adding an iron salt solution, and reacting for 60 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 5.0, adding a copper salt solution, and reacting for 40 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 6.0, a manganese salt solution is added, and the reaction is carried out for 50 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.5, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤2.0 mol% (based on the total amount of amino acids in the mother liquor).

[0033] Step (3) In situ stabilization: 2.0 wt% of feather hydrolyzed polypeptides and 0.1 wt% of tannic acid were added, reacted at 60°C for 20 minutes, and a compound antioxidant comprising 0.1 wt% of sodium L-ascorbate and 0.05 wt% of sodium thiosulfate and 0.01 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 4 wt% of sorbitol and 2 wt% of trehalose were added. The mixture was cooled to adjust the pH to 5.5, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 1.5 wt% papain, and performing enzymatic hydrolysis at pH 7.0 and 55°C for 3 h; and collecting the 3 kDa peptide fragment by ultrafiltration after inactivation of the enzyme. Example 4

[0034] A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.8 with citric acid. 0.8 wt% of sodium bisulfite was added and the mixture was treated at 48°C for 25 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1.5 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥ 80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥ 12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤ 8 wt%.

[0035] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 49°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.1, add zinc salt solution, and stir to react for 32 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.25; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.8:1, and MFe:MCu is 2.5:1, and the total metal ion addition amount is ≤5.2 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.1, adding an iron salt solution, and reacting for 35 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.6, adding a copper salt solution, and reacting for 25 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.6, a manganese salt solution is added, and the reaction is carried out for 35 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.1, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.2 mol% (based on the total amount of amino acids in the mother liquor).

[0036] Step (3) In situ stabilization: 0.8 wt% of feather hydrolyzed polypeptide and 0.06 wt% of tannic acid were added, reacted at 52°C for 12 minutes, and a compound antioxidant was added: 0.06 wt% of sodium L-ascorbate and 0.025 wt% of sodium thiosulfate; 0.006 wt% of tocopherol (added in the form of an aqueous dispersion). The mixture was then concentrated to a solid content of ≥25%. After concentration, 2.5 wt% of sorbitol and 1.2 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.2, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.8 wt% papain and performing enzymatic hydrolysis at pH 6.2 and 51°C for 1.5 h; and collecting the 1.5 kDa peptide fragment by ultrafiltration after inactivation of the enzyme. Example 5

[0037] A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 3.2 with citric acid. 1.2 wt% sodium bisulfite was added and the mixture was treated at 53°C for 35 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 2.5 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0038] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature was 51°C, and the following steps were carried out in the mother liquor: Step (a) adjust the pH to 3.4, add zinc salt solution, and stir to react for 40 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.4; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 2.5:1, and MFe:MCu is 3.5:1, and the total metal ion addition amount is ≤6.2 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.3, adding an iron salt solution, and reacting for 50 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.8, adding a copper salt solution, and reacting for 35 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.8, a manganese salt solution is added, and the reaction is carried out for 45 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.3, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.8 mol% (based on the total amount of amino acids in the mother liquor).

[0039] Step (3) In situ stabilization: 1.5 wt% of feather hydrolyzed polypeptides and 0.08 wt% of tannic acid were added, reacted at 58°C for 18 minutes, and a compound antioxidant comprising 0.08 wt% of sodium L-ascorbate and 0.04 wt% of sodium thiosulfate and 0.008 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 3.5 wt% of sorbitol and 1.8 wt% of trehalose were added. The mixture was cooled to adjust the pH to 5.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 1.2 wt% papain, and performing enzymatic hydrolysis at pH 6.8 and 54°C for 2.5 h; and collecting the 2.5 kDa peptide segment by ultrafiltration after inactivation of the enzyme.

[0040] Comparative Example 1 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and then 0.5 wt% sodium bisulfite was added and treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥ 80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥ 12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤ 8 wt%.

[0041] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0042] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0043] Comparative Example 2 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content of 60 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0044] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0045] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0046] Comparative Example 3 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. The mother liquor was treated at 45°C for 20 min and filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; sulfur-containing amino acids accounted for ≥12 wt% based on cysteine ​​+ cystine; and the proportion of 3 kDa ultrafiltration retentate was ≤8 wt%.

[0047] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0048] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0049] Comparative Example 4 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0050] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total amount of metal ions added is ≤8.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0051] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0052] Comparative Example 5 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0053] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0054] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0055] Comparative Example 6 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0056] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (b) adjusting the pH to 3.0, adding zinc salt solution, stirring and reacting for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0057] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0058] Comparative Example 7 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0059] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferric nitrate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is copper nitrate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0060] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0061] Comparative Example 8 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0062] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0063] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptides were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0064] Comparative Example 9 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0065] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0066] Step (3) In situ stabilization: 0.05 wt% of tannic acid was added, and the mixture was reacted at 50°C for 10 minutes. A compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was then added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0067] Comparative Example 10 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0068] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0069] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 3.5, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements in the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0070] Comparative Example 11 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0071] Step (2) stepwise chelation: Under inert atmosphere, reaction temperature is 48°C, and the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+ The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0072] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.15 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0073] Comparative Example 12 A method for preparing an organic water-soluble fertilizer containing chelated trace elements in a feather acid hydrolysis mother liquor comprises the following steps: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor was decolorized with activated carbon, and the pH value of the mother liquor was adjusted to 2.5 with citric acid. 0.5 wt% sodium bisulfite was added and the mixture was treated at 45°C for 20 min. The mother liquor was filtered through an ultrafiltration membrane with a molecular weight cutoff of 1 kDa to obtain the mother liquor. The mother liquor must meet the following requirements: total amino acid content ≥80 g / L; the proportion of sulfur-containing amino acids, calculated as cysteine ​​+ cystine, ≥12 wt%; and the proportion of 3 kDa ultrafiltration retentate ≤8 wt%.

[0074] Step (2) stepwise chelation: Under air atmosphere, reaction temperature 60 ℃, the following steps are carried out in the mother liquor in sequence: Step (a) adjust the pH to 3.0, add zinc salt solution, and stir to react for 30 minutes; the zinc salt is zinc glycine pre-chelate, and the addition amount is based on Zn 2+The molar ratio of Zn to free -SH groups in the mother liquor is 1:1.2; the molar ratio of metal ions satisfies: Zn:(Fe+Cu) = 1.5:1, and MFe:MCu is 2:1, and the total metal ion addition amount is ≤5.0 mol% (based on the total amount of amino acids in the mother liquor); Step (b) adjusting the pH to 4.0, adding an iron salt solution, and reacting for 30 minutes; the iron salt is ferrous sulfate; Step (c) adjusting the pH to 4.5, adding a copper salt solution, and reacting for 20 minutes; the copper salt is basic copper carbonate; In step (d), the pH is adjusted to 5.5, a manganese salt solution is added, and the reaction is carried out for 30 minutes; the manganese salt is manganese sulfate; the pH is adjusted to 6.0, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤1.0 mol% (based on the total amount of amino acids in the mother liquor).

[0075] Step (3) In situ stabilization: 0.5 wt% of feather hydrolyzed polypeptide and 0.05 wt% of tannic acid were added, reacted at 50°C for 10 minutes, and a compound antioxidant comprising 0.05 wt% of sodium L-ascorbate and 0.02 wt% of sodium thiosulfate and 0.005 wt% of tocopherol (added in the form of an aqueous dispersion) was added. The mixture was then concentrated to a solid content of ≥25%. After concentration, 2 wt% of sorbitol and 1 wt% of trehalose were added. The mixture was cooled to adjust the pH to 4.0, and stored in a brown, light-proof container at ≤25°C to obtain an organic water-soluble fertilizer containing chelated trace elements from the feather acid hydrolysis mother liquor. Feather hydrolyzed polypeptides were obtained by the following method: taking the >3 kDa macromolecular fraction retained by ultrafiltration in step (1); adding 0.5 wt% papain, and performing enzymatic hydrolysis at pH 6.0 and 50°C for 1 h; and collecting 1 kDa peptides by ultrafiltration after inactivation of the enzyme.

[0076] Detection method: Amino acid analysis: GB / T 18246-2019; Determination of metal ions: GB / T 34764-2017; Stability test: HG / T 4365-2012 "Test method for stability of water-soluble fertilizers", "NY 1106-2010 Water-soluble fertilizers containing amino acids".

[0077] Table 1 is a table of experimental procedures and results of the examples and comparative examples.

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] The performance advantage of the embodiment is derived from the synergistic effect of the whole chain process. In the mother liquor pretreatment, citric acid is used to adjust the pH to 2.5-3.5, which provides an optimal reducing environment for sodium bisulfite and effectively protects the -SH group of sulfur-containing amino acids from oxidation. The ultrafiltration membrane with a molecular weight cutoff of 1-3kDa accurately removes interfering colloidal impurities. At the same time, the retained macromolecular components are enzymatically hydrolyzed into 1-3kDa polypeptides by papain. These polypeptides form a coating structure with tannic acid through hydrogen bonds and hydrophobic interactions during the in situ stabilization stage, building a physical barrier for the chelate. During the step-by-step chelation, the zinc glycine pre-chelate preferentially combines with the free -SH group at a molar ratio of 1: (1.2-1.5), seizes the coordination site and avoids competition with other metal ions. The inert atmosphere protection and the reaction temperature of 48-52°C further inhibit the Fe 3+ / Cu 2+ The oxygen free radical chain reaction is triggered, and the ratio design of Zn:(Fe+Cu)=(1.5-3.0):1 balances the chelation efficiency of each metal ion. Finally, the synergistic effect of the compound antioxidant, sorbitol, and trehalose extends the shelf life of the product, making the embodiment perform well in terms of total amino acid retention rate and metal chelation rate, and the decomposition rate after storage at 40°C for 30 days is less than 10%.

[0086] In Comparative Example 1, because citric acid was not used to adjust the pretreatment pH, the sodium bisulfite reduction efficiency decreased, the oxidation rate of sulfur-containing amino acids increased, resulting in a decrease in chelation sites, and the colloidal stability of the solution decreased, causing slight flocculation; in Comparative Example 2, the total amino acid content of the mother liquor was only 60 g / L, the effective coordination groups were insufficient, and the chelation rate decreased; in Comparative Example 3, sodium bisulfite was missing, and sulfur-containing amino acids were oxidized in large quantities, which not only reduced the chelation sites, but also generated oxidation products that interfered with the stability of the system, and the decomposition rate increased significantly; in Comparative Example 4, the total metal ion addition amount reached 8.0 mol%, exceeding the amino acid carrying capacity, the excess metal ions caused precipitation, and the chelation rate dropped sharply; in Comparative Example 5, Zn:(Fe+Cu)=1:1, Zn 2+ Unable to effectively occupy the coordination site, Fe 3+ / Cu 2+ Combined with sulfur-containing amino acids preferentially and activated the oxidation reaction; Comparative Example 6 changed the chelation order to Fe→Zn, Fe 3+ First, it combines with -SH to initiate the oxidation chain, and then Zn 2+It is difficult to coordinate effectively; Comparative Example 7 uses ferric nitrate and copper nitrate, which are more oxidizing than ferrous sulfate and basic copper carbonate, accelerating the oxidation of sulfur-containing amino acids and the decomposition of chelates; Comparative Example 8 lacks tannic acid, the polypeptide cannot form a stable coating structure, and the antioxidant capacity decreases; Comparative Example 9 lacks feather hydrolyzed polypeptide, and tannic acid alone is difficult to build an effective barrier and has insufficient stability; Comparative Example 10 adjusts the storage pH to 3.5, deviating from the stable range of 4.0-5.5, resulting in partial chelate dissociation; Comparative Example 11 The tannic acid is excessive to 0.15wt%, but competes with amino acids for metal ions, reducing the chelation rate; Comparative Example 12 reacts in an air atmosphere at 60°C, where high temperature and oxygen jointly intensify the oxidation reaction, destroying a large amount of sulfur-containing amino acids, the chelate decomposition rate exceeds 50%, and severe flocculation occurs.

Claims

1. A method for preparing an organic water-soluble fertilizer containing chelated trace elements from feather acid hydrolysis mother liquor, characterized in that: The following steps are involved: Step (1) mother liquor pretreatment: The feather acid hydrolysis mother liquor is decolorized with activated carbon, and then 0.5-1.5 wt% of sodium bisulfite is added, and the mixture is treated at 45-55° C. for 20-40 minutes, and filtered through an ultrafiltration membrane with a molecular weight cut-off of 1-3 kDa to obtain a mother liquor; Step (2) stepwise chelation: Under inert atmosphere, the following steps are carried out in sequence in the mother liquor: Step (a) adjusting the pH to 3.0-3.5, adding zinc salt solution, and stirring the reaction for 30-45 minutes; Step (b) adjusting the pH to 4.0-4.5, adding an iron salt solution, and reacting for 30-60 minutes; Step (c) adjusting the pH to 4.5-5.0, adding a copper salt solution, and reacting for 20-40 minutes; Step (d) adjusting the pH to 5.5-6.0, adding a manganese salt solution, and reacting for 30-50 minutes; Step (3) In situ stabilization: 0.5-2 wt% of feather hydrolyzed polypeptide and 0.05-0.1 wt% of tannic acid are added, reacted at 50-60° C. for 10-20 minutes, then concentrated to a solid content of ≥25%, cooled and adjusted to a pH of 4.0-5.5 to obtain an organic water-soluble fertilizer containing chelated trace elements in the feather acid hydrolysis mother liquor.

2. The method for preparing an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor according to claim 1, characterized in that: The feather acid hydrolysis mother liquor must simultaneously meet the following requirements: total amino acid content ≥80 g / L; sulfur-containing amino acids account for ≥12 wt % based on cysteine+cystine; and 3 kDa ultrafiltration retentate accounts for ≤8 wt %.

3. The method for preparing an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor according to claim 1, characterized in that: Before the sodium bisulfite treatment in step (1), the pH of the mother liquor is adjusted to 2.5-3.5 using citric acid.

4. The method for preparing an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor according to claim 1, characterized in that: The zinc salt in step (2) (a) is a zinc glycinate pre-chelate, and the amount of zinc glycinate added is based on the amount of zinc glycinate. 2+ The molar ratio of the metal ions to the free -SH groups in the mother liquor is 1:(1.2-1.5); the molar ratio of the metal ions satisfies: Zn:(Fe+Cu) = (1.5-3.0):1, and M Fe :M Cu The ratio is 2-4:1, and the total amount of metal ions added is ≤6.5 mol% (based on the total amount of amino acids in the mother liquor).

5. The method for preparing an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor according to claim 1, characterized in that: The reaction temperature of step (2) is 48-52°C.

6. The method for preparing an organic water-soluble fertilizer for chelating trace elements in feather acid hydrolysis mother liquor according to claim 1, characterized in that: The feather hydrolyzed polypeptide in step (3) is obtained by the following method: Take the macromolecular fraction retained by ultrafiltration in step (1), with a molecular weight > 3 kDa; Add 0.5-1.5wt% of papain and perform enzymolysis at pH 6.0-7.0 and 50-55℃ for 1-3h; After inactivation of the enzyme, 1-3 kDa peptides were collected by ultrafiltration.

7. The method for preparing an organic water-soluble fertilizer containing chelated trace elements from feather acid hydrolysis mother liquor according to claim 1, characterized in that: After the reaction in step (3), add a compound antioxidant: Sodium L-ascorbate 0.05-0.1wt% + sodium thiosulfate 0.02-0.05wt%; Tocopherol 0.005-0.01wt%.

8. The method for preparing an organic water-soluble fertilizer containing chelated trace elements from feather acid hydrolysis mother liquor according to claim 1, characterized in that: The step of calcium / magnesium chelation is also included: after step (2) (d), the pH is adjusted to 6.0-6.5, calcium gluconate and magnesium citrate are added, and the total amount of calcium and magnesium ions is ≤ 2.0 mol% of the total amount of amino acids.

9. The method for preparing an organic water-soluble fertilizer containing chelated trace elements from feather acid hydrolysis mother liquor according to claim 1, characterized in that: After concentration, add 2-4 wt% sorbitol and 1-2 wt% trehalose, and store in a brown light-proof container at ≤25°C.

10. An organic water-soluble fertilizer containing trace elements chelated from feather acid hydrolysis mother liquor, characterized in that: The fertilizer is prepared by the method for preparing an organic water-soluble fertilizer containing chelated trace elements in feather acid hydrolysis mother liquor as described in any one of claims 1 to 9.

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