Water-soluble fertilizer containing polyglutamic acid and preparation method thereof

Abstract

The invention discloses a water-soluble fertilizer containing polyglutamic acid, which is characterized in that fermentation liquor rich in polyglutamic acid is purified through centrifugation and ultrafiltration concentration, and impurities in the fermentation liquor are taken out to prevent the impurities in the fermentation liquor from influencing the quality of the produced water-soluble fertilizer; polyglutamic acid is combined with metal ions through carboxyl, phosphorus precipitation is reduced, release of phosphorus elements can be delayed, the fertilizer efficiency can be prolonged, root hair development can be promoted, and the active absorption capacity of crops to nitrogen, phosphorus and potassium can be enhanced; polyglutamic acid adsorbs ammonium ions through hydrogen bonds, and nitrogen loss is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fertilizer manufacturing, in particular to a water-soluble fertilizer containing polyglutamic acid and a preparation method thereof. BACKGROUND

[0002] The water-soluble fertilizer is a kind of fertilizer that can be completely or almost completely dissolved in water. It can quickly release nutrients and be directly absorbed by crop roots or leaves, and has the advantages of quick effect, high utilization rate, and convenient application. Polyglutamic acid is a kind of high polymer with water solubility, biodegradability and non-toxicity. When it is applied to soil, it forms a thin film on the surface of plant root hairs, not only protecting the root hairs, but also being the best transport platform for the close contact between soil nutrients, water and root hairs, which can effectively improve the dissolution, storage, transport and absorption of fertilizers. It prevents the precipitation of sulfate, phosphate and oxalate with metal elements, so that crops can more effectively absorb phosphorus, calcium, magnesium and trace elements in the soil. It promotes the development of crop roots and enhances disease resistance. Therefore, polyglutamic acid is a substance added to water-soluble fertilizer to promote the absorption of fertilizers by crops.

[0003] Currently, polyglutamic acid is mainly obtained by microbial fermentation, but the fermented microbial fermentation broth has the problems of high viscosity and difficult purification. If it is directly added to water-soluble fertilizer without purification, the impurities in the fermentation broth will affect the quality of the water-soluble fertilizer. In the prior art "Method for extracting and purifying gamma-polyglutamic acid from gamma-polyglutamic acid fermentation broth" (CN118240201B), a method for extracting and purifying polyglutamic acid is disclosed, but the method is complex and time-consuming, which makes it difficult to be applied in modern industrial production. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects of the prior art and provide a water-soluble fertilizer containing polyglutamic acid.

[0005] In order to solve the above technical problems, the present application provides the following technical solutions: The present application provides a water-soluble fertilizer containing polyglutamic acid, which comprises phosphite, potassium nitrate, methyl urea, sodium humate, EDTA-Fe and pH adjuster, and further comprises polyglutamic acid and ammonium polyphosphate, wherein the polyglutamic acid is provided by a polyglutamic acid concentrate; The preparation of the polyglutamic acid concentrate comprises the following processes: The original fermentation broth obtained by fermentation culture of Bacillus is adjusted in viscosity to obtain a fermentation broth rich in polyglutamic acid; Water is added to the fermentation broth rich in polyglutamic acid and heated to 50-80℃ to dilute it to obtain a dilution liquid, the dilution liquid is transferred to a centrifuge for centrifugation, and the supernatant obtained by centrifugation is concentrated by ultrafiltration to obtain a polyglutamic acid concentrate.

[0006] As a preferred technical solution of the present application, the mass ratio of the phosphite, the potassium nitrate, the methyl urea, the ammonium polyphosphate, the sodium humate, the EDTA-Fe, the pH regulator and the polyglutamic acid is 10-50:10-50:10-50:1-10:0.1-1:0.01-1:0.1-1:0.1-1.

[0007] As a preferred technical solution of the present application, the methyl urea is one or more of urea formaldehyde, monomethylol urea, dimethylol urea, methylene diurea and dimethylene triurea.

[0008] As a preferred technical solution of the present application, the methyl urea is urea formaldehyde.

[0009] As a preferred technical solution of the present application, the phosphite is one or more of potassium phosphite, sodium phosphite and ammonium phosphite.

[0010] As a preferred technical solution of the present application, the phosphite is potassium phosphite.

[0011] As a preferred technical solution of the present application, the pH regulator is citric acid.

[0012] As a preferred technical solution of the present application, the Bacillus is Bacillus subtilis; the viscosity of the fermentation broth rich in polyglutamic acid is ≤15 Pa·s, and water is added thereto to obtain a dilution liquid with a viscosity of ≤10 Pa·s by constant stirring at 60℃ for 45 min; the dilution liquid is transferred to a tubular centrifuge for centrifugation at 10000-12000 rpm to obtain supernatant, and the supernatant is transferred to an ultrafiltration device for ultrafiltration to obtain a polyglutamic acid concentrate with a polyglutamic acid content of 15 g / L.

[0013] A preparation method of a water-soluble fertilizer containing polyglutamic acid, the phosphite, the potassium nitrate, the methyl urea, the ammonium polyphosphate, the sodium humate, the EDTA-Fe, the pH regulator and the polyglutamic acid are mixed, stirred at 100-200 rpm, dried and granulated to obtain the water-soluble fertilizer.

[0014] Compared with the prior art, the present application has the following advantages: 1. The fermentation broth rich in polyglutamic acid is purified by centrifugation and ultrafiltration concentration to remove impurities therein, so as to prevent the impurities in the fermentation broth from affecting the quality of the water-soluble fertilizer obtained by production; 2. The polyglutamic acid binds with metal ions through carboxyl groups, reduces phosphorus precipitation, delays the release of phosphorus elements, prolongs the fertilizer effect, promotes root hair development, and enhances the active absorption capacity of crops to nitrogen, phosphorus and potassium; 3. Polyglutamic acid adsorbs ammonium ions through hydrogen bonds, reducing nitrogen loss. DETAILED DESCRIPTION

[0015] The preferred embodiments of the present application are described below, and it should be understood that the preferred embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0017] The present application provides a water-soluble fertilizer containing polyglutamic acid, which comprises phosphite, potassium nitrate, methyl urea, sodium humate, EDTA-Fe and a pH regulator, and further comprises polyglutamic acid and ammonium polyphosphate, wherein the polyglutamic acid is provided by a polyglutamic acid concentrate; The preparation of the polyglutamic acid concentrate comprises the following processes: The original fermentation broth obtained by fermentation culture of Bacillus is adjusted in viscosity to obtain a fermentation broth rich in polyglutamic acid; Water is added to the fermentation broth rich in polyglutamic acid, and the mixture is heated to 50-80℃ to obtain a dilution liquid. The dilution liquid is transferred to a centrifuge for centrifugation. The supernatant obtained by centrifugation is concentrated by ultrafiltration to obtain a polyglutamic acid concentrate.

[0018] Further, the mass ratio of the phosphite, potassium nitrate, methyl urea, ammonium polyphosphate, sodium humate, EDTA-Fe, pH regulator and polyglutamic acid is 10-50:10-50:10-50:1-10:0.1-1:0.01-1:0.1-1:0.1-1.

[0019] Further, the methyl urea is one or more of urea formaldehyde, monomethylol urea, dimethylol urea, methylene diurea and dimethylene triurea.

[0020] Further, the methyl urea is urea formaldehyde.

[0021] Further, the phosphite is one or more of potassium phosphite, sodium phosphite and ammonium phosphite.

[0022] Further, the phosphite is potassium phosphite.

[0023] Further, the pH regulator is citric acid.

[0024] Further, the Bacillus is Bacillus subtilis. Water is added to the fermentation broth rich in polyglutamic acid, and the mixture is stirred at 60℃ for 45min to obtain a dilution liquid with a viscosity of ≤10Pa·s. The dilution liquid is transferred to a tubular centrifuge for centrifugation at 10000-12000rpm to obtain supernatant. The supernatant is transferred to an ultrafiltration device for ultrafiltration to obtain a polyglutamic acid concentrate with a polyglutamic acid content of 15g / L.

[0025] Example 1: A water-soluble fertilizer was prepared with the mass ratio of potassium phosphite, potassium nitrate, urea-formaldehyde, ammonium polyphosphate, sodium humate, EDTA-Fe, citric acid and polyglutamic acid being 50:50:50:10:0.1:0.01:0.1:0.1, wherein the source of polyglutamic acid was polyglutamic acid concentrate.

[0026] Example 2: A water-soluble fertilizer was prepared with the mass ratio of potassium phosphite, potassium nitrate, urea-formaldehyde, ammonium polyphosphate, sodium humate, EDTA-Fe, citric acid and polyglutamic acid being 50:50:50:10:0.1:0.01:0.1:0.3, wherein the source of polyglutamic acid was polyglutamic acid concentrate.

[0027] Example 3: A water-soluble fertilizer was prepared with the mass ratio of potassium phosphite, potassium nitrate, urea-formaldehyde, ammonium polyphosphate, sodium humate, EDTA-Fe, citric acid and polyglutamic acid being 50:50:50:10:0.1:0.01:0.1:0.5, wherein the source of polyglutamic acid was polyglutamic acid concentrate.

[0028] Comparative Examples 1-3: On the basis of Examples 1-3, the source of polyglutamic acid was replaced by a fermentation broth rich in polyglutamic acid.

[0029] Comparative Example 4: A water-soluble fertilizer was prepared on the basis of Example 1 without adding polyglutamic acid.

[0030] Experimental design: Experimental crop: cherry tomatoes, variety: Golden Sun.

[0031] Experimental device and settings: hydroponic system, temperature: 22-26°C (day) / 18-20°C (night), light: 16 hours light (200 μmol·m⁻²·s⁻¹) / 8 hours dark, humidity: 60-70%; the seeds used were all pretreated in the same way.

[0032] Fertilizer application: Examples 1-3 and Comparative Examples 1-4.

[0033] Sampling and determination period: the experiment lasted for 4 weeks, each group was given a fixed amount of fertilizer at fixed time, samples were taken at the 2nd and 4th weeks respectively, 5 plants were randomly selected from each group, the root systems were washed and the surface water was absorbed with filter paper.

[0034] Determination method: root activity determination-TTC reduction method and plant nutrient content determination.

[0035] The results of root activity determination are shown in the data in Table 1: Table 1

[0036] From Table 1, it can be seen that 1, the water-soluble fertilizer added with polyglutamic acid can improve the root activity of tomato; 2, too much polyglutamic acid added will inhibit the root activity of tomato; 3, the fermentation broth rich in polyglutamic acid containing impurities can also improve the root activity of tomato, but the effect is not as good as the purified polyglutamic acid concentrate, and the effect difference increases with the extension of the experimental period.

[0037] The plant nutrient content determination results are shown in the data in Table 2: Table 2

[0038] From Table 2, it can be seen that 1, the water-soluble fertilizer added with polyglutamic acid can improve the nitrogen, phosphorus and potassium content in tomato plants; 2, too much polyglutamic acid added will limit the absorption of nitrogen, phosphorus and potassium of tomato; 3, the fermentation broth rich in polyglutamic acid containing impurities can also improve the absorption effect of nitrogen, phosphorus and potassium of tomato, but the effect is not as good as the purified polyglutamic acid concentrate, and the effect difference increases with the extension of the experimental period.

[0039] A preparation method of a water-soluble fertilizer containing polyglutamic acid, the water-soluble fertilizer is prepared by mixing phosphite, potassium nitrate, methyl urea, ammonium polyphosphate, sodium humate, EDTA-Fe, pH regulator and polyglutamic acid, stirring at 100-200 rpm, drying and granulating.

[0040] Specifically, after mixing, stirring at 100 rpm and constant temperature 25℃ for 1h, drying, and granulating by drum or fluidized bed to obtain the water-soluble fertilizer, the moisture content is ≤3%.

[0041] Finally, it should be noted that: the above is only the preferred embodiment of the present application, and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A water-soluble fertilizer containing polyglutamic acid, comprising phosphite, potassium nitrate, methylurea, sodium humate, EDTA-Fe, and a pH adjuster, characterized in that, It also contains polyglutamic acid and ammonium polyphosphate, wherein the polyglutamic acid is provided by polyglutamic acid concentrate; The preparation of the polyglutamic acid concentrate includes the following process: The viscosity of the original fermentation broth obtained from Bacillus fermentation culture was adjusted to obtain a fermentation broth rich in polyglutamic acid; Water is added to the fermentation broth rich in polyglutamic acid and heated to 50-80℃ to dilute it and obtain a diluted solution. The diluted solution is then transferred to a centrifuge for centrifugation. The supernatant obtained by centrifugation is then concentrated by ultrafiltration to obtain a concentrated polyglutamic acid solution.

2. The water-soluble fertilizer containing polyglutamic acid according to claim 1, characterized in that, The mass ratio of the phosphite, potassium nitrate, methylurea, ammonium polyphosphate, sodium humate, EDTA-Fe, pH adjuster, and polyglutamic acid is 10-50:10-50:10-50:1-10:0.1-1:0.01-1:0.1-1:0.1-1.

3. The water-soluble fertilizer containing polyglutamic acid according to claim 2, characterized in that, The methylurea is one or more of urea-formaldehyde, monohydroxymethylurea, dihydroxymethylurea, methylene diurea, and dimethylene triurea.

4. A water-soluble fertilizer containing polyglutamic acid according to claim 3, characterized in that, The methylurea is urea-formaldehyde.

5. A water-soluble fertilizer containing polyglutamic acid according to claim 2, characterized in that, The phosphite is one or more of potassium phosphite, sodium phosphite, and ammonium phosphite.

6. A water-soluble fertilizer containing polyglutamic acid according to claim 5, characterized in that, The phosphite is potassium phosphite.

7. A water-soluble fertilizer containing polyglutamic acid according to claim 2, characterized in that, The pH adjuster is citric acid.

8. A water-soluble fertilizer containing polyglutamic acid according to claim 1, characterized in that, The Bacillus species is Bacillus subtilis; the fermentation broth rich in polyglutamic acid has a viscosity ≤15 Pa·s, and water is added to it and stirred at a constant temperature of 60℃ for 45 min to obtain a diluted solution with a viscosity ≤10 Pa·s; the diluted solution is transferred to a tubular centrifuge and centrifuged at 10000-12000 rpm to obtain the supernatant, and the supernatant is transferred to an ultrafiltration device for ultrafiltration to obtain a polyglutamic acid concentrate with a polyglutamic acid content of 15 g / L.

9. A method for preparing a water-soluble fertilizer containing polyglutamic acid, characterized in that, The water-soluble fertilizer is obtained by mixing the phosphite, potassium nitrate, methyl urea, ammonium polyphosphate, sodium humate, EDTA-Fe, pH adjuster and polyglutamic acid, stirring at 100-200 rpm, drying and granulating.

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