An oligopeptide-polyamine coordination complex organic ferrous aqueous solution, its preparation method and application

Abstract

This invention discloses an oligopeptide polyamine coordination complex organic ferrous sulfate aqueous solution, its preparation method, and its application, belonging to the field of agricultural functional water-soluble fertilizer technology. This invention uses a polyamine coordination compound with a pH of 8.5-10.0, plant / animal-derived small molecule oligopeptides with a molecular weight of 300-450 Da and antioxidant activity, and ferrous sulfate heptahydrate as main raw materials, and employs a two-step method with nitrogen protection, segmented temperature control, and a fixed feeding sequence. This invention utilizes the synergistic effect of the antioxidant and reducing properties of the oligopeptide and the basic coordination effect of the polyamine coordination compound to construct a two-site complex structure, effectively inhibiting Fe... 2+ Oxidative inactivation enhances the stability of product complexation and the efficiency of targeted translocation within the crop, significantly improving iron deficiency chlorosis, premature aging, and chlorosis in crops. It also promotes the physiological activity of biological enzymes within the crop, accelerates cell proliferation, and enhances the crop's resistance to stress and disease. This invention utilizes readily available raw materials, precise process parameters, and strong controllability.

Description

Technical Field

[0001] This invention relates to the field of agricultural functional water-soluble fertilizer technology, and more specifically to an oligopeptide polyamine coordination complex organic ferrous water-soluble agent, its preparation method, and its application. Background Technology

[0002] Iron is an essential micronutrient for plant growth and development, participating in chlorophyll synthesis, photosynthesis, respiration, and various enzymatic reactions, playing a crucial role in crop yield and quality. However, commonly used inorganic ferrous salts in traditional agricultural production (such as ferrous sulfate heptahydrate and ferrous ammonium sulfate) have significant drawbacks: they are readily oxidized to Fe in soil environments (especially under alkaline conditions, pH > 7.0). 3+ This forms insoluble hydroxides (Fe(OH)3) or phosphate precipitates (such as FePO4), leading to decreased plant susceptibility to Fe. 2+ The absorption rate of Fe is less than 10%, which not only wastes fertilizer resources but also easily leads to nutrient absorption disorders and element imbalances in plants. Studies have confirmed that Fe... 2+ Its nutritional supply and physiological protection effects on plants are significantly better than those of Fe. 3+ It is more easily absorbed and utilized through iron transport proteins on plant cell membranes.

[0003] In existing technologies, organic chelated iron fertilizers such as amino acid chelated iron, EDTA chelated iron, and polypeptide chelated iron bind to Fe through ligands. 2+ The formation of complexes improves the stability of ferrous ions, but the following key technical challenges remain:

[0004] ① Poor targeting of iron transport: Iron is a low-mobility element in plants, and it is difficult for iron in old leaves and fallen leaves to be transferred to new tissues (such as young leaves and shoots). After crops absorb organically chelated iron, the chelate is prone to dissociation during transport within the plant, and the ligands lose their binding affinity for Fe. 2+ The protective effect of Fe leads to 2+ It is captured and inactivated by endogenous organic acid radicals in plants (such as oxalate and citrate radicals), or it binds with calcium in the body. 2+ Zn 2+ Mn 2+ Cu 2+ Metal ions can competitively adsorb and inhibit the growth of iron, or they can remain bound in non-iron-requiring cellular tissues. This is the fundamental reason why, even with the application of chelated iron fertilizers through foliar spraying, soil root application, or even increased dosage and repeated application, the iron deficiency, yellowing, chlorosis, and premature aging of crops are still difficult to effectively improve in actual production.

[0005] ② Insufficient stability of the production process: Traditional chelation reactions lack strict segmented temperature control standards and the order of feeding is not clearly defined, resulting in excessive pH fluctuations in the reaction system (deviating from Fe). 2+The optimal complexation range is pH 7.0–8.5; insufficient reaction leads to Fe... 2+ Oxidation failure can easily lead to problems such as turbidity, layering, and precipitation in the final product, shortening the shelf life and resulting in poor product quality consistency in industrial production.

[0006] ③ Chelating agents have limited function or side effects: Practice has shown that the EDTA ligand in EDTA-chelated iron can only be passively absorbed through transpiration in plant leaves. Excessive accumulation can damage the plant cell's antioxidant system (such as reducing SOD and POD enzyme activity), inhibit plant growth, and even cause leaf burn. Although conventional amino acid or polypeptide chelating agents have certain nutritional functions, they are not effective for iron absorption. 2+ The complexation stability constant is low (logK < 12), which is beneficial to Fe. 2+ Its protective ability is weak, and the ligand structure lacks targeted transduction sites, resulting in chelated Fe... 2+ It is easily decomposed in the soil, has low internal conductivity, and its element utilization rate varies.

[0007] To address the aforementioned technical deficiencies, this invention is based on the core design principles of the antioxidant and reducing properties of oligopeptides and the basic coordination characteristics of polyamino coordination compounds (the aqueous solution of the polyamino coordination compounds has a pH of 8.5~10.0, and the reaction system can be adjusted to Fe...). 2+ With a suitable pH for complexation (7.5-8.0), this study provides a highly stable and highly absorbable oligopeptide-polyamine coordination complex organic ferrous sulfate aqueous solution and its standardized preparation method by optimizing raw material composition, defining segmented temperature control parameters, and fixing the feeding sequence, filling a gap in existing technologies. The molecular weight of this type of coordination complex is controlled at around 600 Da, making it easily absorbed by plants. The oligopeptide and polyamine groups not only stabilize Fe through synergistic complexation but also... 2+ It also possesses a certain degree of targeted transduction capability. After being absorbed by plants, it can quickly transfer Fe... 2+ Transported to iron-deficient and iron-demanding parts, polyamine and oligopeptide groups can also assist plant endogenous enzymes in constructing Fe... 2+ As the functional group of the active center, it enhances the cell's ability to divide and proliferate and the cell membrane's ability to permeate and protect itself; at the same time, it enhances the efficiency of electron transport in the plant, promotes a variety of beneficial biochemical reactions, improves nitrogen utilization and chlorophyll synthesis efficiency, and ultimately achieves the effect of rapid plant growth and enhanced disease resistance and stress resistance. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of Fe in existing organic ferrous fertilizers. 2+ It is easily oxidized, has poor complexation stability, low bioavailability, and uncontrollable production processes. Furthermore, after absorption by crops, its translocation is hindered, preventing its targeted transport to iron-deficient and iron-demanding sites, and hindering the absorption of Fe within plants. 2+To address the technical deficiency of insufficient activity of functional groups in the active center, this paper provides a scientifically formulated, highly stable, and crop-absorbable oligopeptide-polyamine coordination complex organic ferrous aqueous solution. It also provides a simple, parameter-defined preparation method suitable for industrial-scale production.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: An oligopeptide polyamine coordination complex organic ferrous aqueous solution comprises the following components in parts by weight: 10-20 parts of polyamino coordination compounds, 5-15 parts of antioxidant active oligopeptides, 8-18 parts of ferrous sulfate heptahydrate, and deionized water to make up to 100 parts.

[0010] In some embodiments, the polyamine coordination compound is an aliphatic / alcoholic amine polyamine compound with an aqueous solution pH of 8.5–10.0. It provides a stable, weakly alkaline reaction environment, and the amino group (-NH2) in its molecule can react with Fe. 2+ Forming coordinate bonds and constructing a primary complex structure enhances product stability.

[0011] In some embodiments, the antioxidant oligopeptide is a small molecule oligopeptide of plant or animal origin with antioxidant activity, having a molecular weight of 300-450 Da. It contains antioxidant active groups such as hydroxyl (-OH) and thiol (-SH), and can inhibit Fe2+ by scavenging oxygen free radicals. 2+ Oxidized to Fe 3+ Meanwhile, the residual amino (-NH2) and carboxyl (-COOH) groups in the oligopeptide molecule can react with Fe. 2+ A secondary complexation structure is formed, ultimately constructing a "two-site synergistic complexation" system.

[0012] Another object of the present invention is to provide a method for preparing the above-mentioned oligopeptide polyamine coordination complex organic ferrous aqueous agent, comprising the following steps: (1) Coordination complexation stage Add the prescribed amount of deionized water to the reactor, start stirring (300~500 r / min), and continuously introduce nitrogen gas (0.5~1.0 L / min); add the polyamine coordination compound, continue stirring until completely dissolved, raise the temperature to 30~35℃ (temperature fluctuation ≤±2℃), add ferrous sulfate aqueous solution dropwise at a rate of 5~10 g / min, maintain this temperature and react for 2 hours to obtain a green and transparent polyamine ferrous sulfate coordination mother liquor; (2) Antioxidant protection and complexation stage The polyamine ferrous sulfate complex mother liquor was heated to 45-50℃ (temperature fluctuation ≤ ±2℃), and stirred (400-600 r / min). The formulated amount of oligopeptide compound was added to the mother liquor at a rate of 5-10 g / min. After being dispersed evenly, stirring was continued for 10 min. The reaction was carried out at a constant temperature of 45-50℃ for 1 h, with continuous stirring and nitrogen gas purging for protection. After the reaction was completed, the mixture was naturally cooled to room temperature and filtered through a 0.22 μm microporous membrane to obtain the oligopeptide polyamine complex organic ferrous sulfate aqueous solution.

[0013] This invention solves the problem of Fe by precisely matching the chemical properties of raw materials with process parameters. 2+ This addresses the issue of oxidative protection, enhances its mobility and targeting within plants, and utilizes the bioactivity of oligopeptides and polyamines to synergize with Fe... 2+ The specific principles behind improving plant growth performance are as follows: 1. The weak basicity (pH 8.5–10.0) of polyamino coordination compounds provides a suitable pH environment for the coordination reaction (final system pH 7.5–8.0). The amino group (-NH2) in their molecule reacts with Fe... 2+ Formation of primary coordination complexes (Fe 2 --polyamine complex), initially inhibiting Fe 2+ Hydrolysis and oxidation; 2. The hydroxyl (-OH) and thiol (-SH) groups in oligopeptide molecules can effectively scavenge oxygen free radicals in the reaction system and plants, and block Fe. 2+ →Fe 3+ The oxidation pathway, while its carboxyl (-COOH), amino (-NH2) groups and Fe in the primary coordination complex. 2 + Further combination forms a secondary complex, constructing a stable "polyamine-oligopeptide dual-site synergistic complexation" structure (molecular weight approximately 600 Da); (Optimization notes: Clarifying the complexation structure type and molecular weight, supplementing the oxidation blocking mechanism, and making the chemical principle clearer) 3. Segmented temperature control design: 30~35℃ is the suitable temperature for coordination reaction, which can promote the reaction of amino groups with Fe²⁺. + Coordination binding; 45~50℃ can prevent the inactivation of the antioxidant groups (-SH, -OH) of oligopeptides, while inhibiting Fe 2+ Oxidation, balancing reaction efficiency and product stability; 4. The dual-site complex structure not only enhances Fe 2+ Its ability to resist fixation in the soil (avoiding binding with soil colloids and phosphates) also enhances its targeting and translocation within plants, allowing it to be transported to iron-deficient areas through the plant phloem, thus addressing the technical challenge of poor iron mobility.

[0014] This invention also aims to provide the application of the aforementioned oligopeptide-polyamine coordination compound organic ferrous aqueous solution in the treatment of iron deficiency chlorosis in fruit trees (apple, pear, citrus, grape), vegetables (tomato, cucumber, pepper), grain crops (wheat, corn, rice), and flowers. It is particularly suitable for treating iron deficiency chlorosis in alkaline soils (pH > 7.0), greenhouse cultivation, or fields with continuous cropping obstacles. It can be applied through foliar spraying, drip irrigation, or fertigation, using a 500-1000 times diluted solution (by weight of the finished product), applied every 7-10 days, with 2-3 consecutive applications achieving significant corrective effects.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention has the following technical effects: 1. Significantly improved complexation stability: Through a process of "dual-site synergistic complexation + nitrogen protection + segmented temperature control", Fe is effectively suppressed. 2+ Oxidation: The product remains clear and transparent even after being sealed and stored at room temperature (25℃) for 6 months. (Fe) 2+ With an oxidation rate of less than 5%, its stability far exceeds that of existing organic ferrous fertilizers. 2. High bioavailability: The dual-site complexation structure enables Fe... 2+ It is not easily fixed by soil colloids and phosphates, and the absorption efficiency of crop roots is increased to more than 35%, which is 3 to 4 times higher than that of traditional ferrous sulfate. It can also be transported to iron-deficient parts. 3. Precise and outstanding fertilizer effect: It can quickly replenish the Fe required by crops. 2+ Iron deficiency chlorosis can be corrected in 7 to 10 days, while promoting chlorophyll synthesis and photosynthesis, enhancing crop resistance (drought resistance, cold resistance), increasing yield by 10% to 15% compared with conventional fertilization, and significantly improving fruit quality (such as sugar content and vitamin content). 4. High degree of process standardization: The key conditions such as raw material properties (pH, molecular weight, functional groups), temperature parameters, feeding sequence, and nitrogen flow rate are clearly defined. The operation is simple and highly controllable, and it can be directly applied to industrial mass production, solving the problems of unstable processes and large fluctuations in product quality in existing technologies. 5. Green and environmentally friendly: The raw materials are all biodegradable components (polyamino coordination compounds, plant / animal-derived oligopeptides), with no harmful ligand residues such as EDTA. After application, it can improve the soil micro-ecological environment, which meets the development needs of "reducing fertilizer and increasing efficiency, and green agriculture". Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1 This embodiment provides an oligopeptide polyamine coordination complex organic ferrous aqueous solution, comprising: 15 parts of polyamine coordination compound (industrial grade TETA, pH 9.2, 25℃), 10 parts of oligopeptide (commercially available SOP-300 soybean oligopeptide, molecular weight 300~450 Da, containing thiol antioxidant groups), 12 parts of ferrous sulfate heptahydrate, and 63 parts of deionized water.

[0018] Preparation methods include: (1) Add 63 parts of deionized water to the reactor, turn on the stirring (400 r / min), and continuously introduce nitrogen gas (0.8 L / min) for protection; (2) Add 15 parts of the polyamino coordination compound and stir until completely dissolved; (3) Start the temperature control system, raise the temperature to 32°C, add 12 parts of ferrous sulfate aqueous solution at a rate of 8g / min, and react at a constant temperature for 2h to obtain polyamine ferrous sulfate complex mother liquor (pH 7.8, 25°C, no visible particles). (4) Heat the mother liquor to 48°C, and slowly add 10 parts of oligopeptide aqueous solution at a rate of 8g / min, and react at a constant temperature for 1h. (5) Cool naturally to 25°C and filter with a 0.22μm filter membrane to obtain a clear and transparent oligopeptide polyamine coordination complex organic ferrous aqueous solution.

[0019] Product performance: Finished product pH 7.7 (25℃), Fe 2+ Content 4.2%, no precipitation or discoloration after 6 months of sealed storage at room temperature (25℃), Fe 2+ Oxidation rate <5%, good stability.

[0020] Example 2 This embodiment provides an oligopeptide polyamine coordination complex organic ferrous sulfate aqueous solution, comprising: 12 parts of polyamine coordination compound (industrial grade AEEA, pH 8.8, 25℃), 8 parts of oligopeptide (commercially available FCP-350 fish oligopeptide, molecular weight 300~450 Da, containing hydroxyl antioxidant groups), 10 parts of ferrous sulfate heptahydrate, and 70 parts of deionized water.

[0021] Preparation methods include: (1) Add 70 parts of deionized water to the reactor, turn on the stirring (350 r / min), and continuously introduce nitrogen gas (0.8 L / min) for protection; (2) Add 12 parts of the polyamino coordination compound; stir until completely dissolved; (3) Start the temperature control system, raise the temperature to 33°C, add 10 parts of ferrous sulfate aqueous solution at a rate of 6g / min, and react at a constant temperature for 2h to obtain polyamine ferrous sulfate complex mother liquor (pH 7.6, 25°C). (4) Heat to 46°C, slowly add 8 parts of oligopeptide aqueous solution, and react at a constant temperature for 1 hour; (5) After the reaction is complete, cool to room temperature and filter through a 0.22μm microporous membrane to obtain the finished product.

[0022] Product performance: Finished product pH 7.5 (25℃), Fe 2+ With a content of 3.5%, it showed good stability after being stored in a sealed container at room temperature for 6 months, with no oxidation or deterioration. (Fe) 2+ Oxidation rate < 4%.

[0023] Comparative Example 1 The difference from Example 1 is that only the oligopeptide was modified to a regular polypeptide, which has no obvious antioxidant activity and a separation amount of 500~800 Da.

[0024] Results: Fe in 1 month 2+ Oxidation rate: 28%.

[0025] Comparative Example 2 The difference from Example 1 is that the only change is that the temperature control is changed to a one-pot reaction at room temperature (25°C) throughout the process; Result: Fe in 2 months 2+ Oxidation rate: 22%.

[0026] Comparative Example 3 The difference from Example 1 is that the order of addition is ferrous sulfate → polyamino coordination compound → polypeptide; Results: Precipitate and Fe appeared after 15 days of storage. 2+ Oxidation rate: 41%.

[0027] Comparative Example 4 The difference from Example 1 is that nitrogen gas is not introduced for protection.

[0028] Results: Fe in 1 month 2+ Oxidation rate: 32%.

[0029] Comparative Example 5 The difference from Example 1 is as follows: Common peptides (with no clear antioxidant activity and a molecular weight of 500-800 Da) were used. No segmented temperature control, one-pot reaction at room temperature (25℃) throughout; The order of addition is: ferrous sulfate → polyamino coordination compound → polypeptide; No nitrogen protection.

[0030] Result: The product was cloudy, Fe2+ With a content of only 2.1%, a yellowish-brown precipitate (Fe(OH)3) appears after being left at room temperature for 3 days. 2+ The oxidation rate reached 65%, which could not meet the usage requirements.

[0031] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0032] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An oligopeptide-polyamine coordination complex organic ferrous aqueous solution, characterized in that, Includes the following ingredients by weight: 10-20 parts of polyamino coordination compounds, 5-15 parts of antioxidant active oligopeptides, 8-18 parts of ferrous sulfate heptahydrate, and deionized water to make up to 100 parts.

2. The oligopeptide polyamine coordination composite organic ferrous aqueous solution according to claim 1, characterized in that, The polyamino coordination compound is an aliphatic / alcoholic amine polyamino compound with an aqueous solution pH of 8.5~10.

0.

3. The oligopeptide-polyamine coordination composite organic ferrous aqueous solution according to claim 1, characterized in that, The antioxidant oligopeptides are small molecule oligopeptides of plant or animal origin with antioxidant activity, and have a molecular weight of 300~450 Da.

4. A method for preparing an oligopeptide polyamine coordination complex organic ferrous aqueous solution as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Coordination complexation stage Add the prescribed amount of deionized water to the reactor, start stirring, and continuously introduce nitrogen gas at the same time; add the polyamine coordination compound, continue stirring until completely dissolved, raise the temperature to 30~35℃, add ferrous sulfate aqueous solution dropwise at a rate of 5~10g / min, maintain this temperature and react for 2h to obtain a green and transparent polyamine ferrous sulfate coordination mother liquor. (2) Antioxidant protection and complexation stage The polyamine ferrous sulfate complex mother liquor was heated to 45-50℃ and stirred. The formulated amount of oligopeptide compound was added to the mother liquor at a rate of 5-10 g / min. After being dispersed evenly, the mixture was stirred for 10 min and kept at a constant temperature of 45-50℃ for 1 h. During the reaction, the mixture was stirred continuously and nitrogen gas was introduced for protection. After the reaction was completed, the mixture was naturally cooled to room temperature and filtered to obtain the oligopeptide polyamine complex organic ferrous aqueous solution.

5. The preparation method according to claim 4, characterized in that, In step (1), the stirring speed is 300~500 r / min.

6. The preparation method according to claim 4, characterized in that, In step (1), the flow rate of nitrogen gas introduced is 0.5~1.0 L / min.

7. The preparation method according to claim 4, characterized in that, The reaction endpoint in step (1) is determined when the pH of the mother liquor is 7.5~8.0 and there are no visible particles.

8. The preparation method according to claim 4, characterized in that, In step (2), the stirring speed is kept at 400~600 r / min.

9. The preparation method according to claim 4, characterized in that, The filtration process uses a 0.22μm microporous membrane.

10. The application of the oligopeptide polyamine coordination complex organic ferrous aqueous solution as described in any one of claims 1-3 in the correction of iron deficiency chlorosis in alkaline soils, protected cultivation sites, or sites with continuous cropping obstacles.