Sodium alginate oligosaccharide plant growth regulator slow-release agent and preparation method thereof

Abstract

The invention discloses a sodium alginate oligosaccharide plant growth regulator sustained-release preparation and a preparation method thereof, and the sustained-release preparation is prepared by mixing chitosan and sodium alginate oligosaccharide as main materials and a chitosan solution and a sodium alginate oligosaccharide solution according to different mass ratios. According to the sodium alginate oligosaccharide plant growth regulator slow-release agent, the two raw materials are blended through electrostatic interaction, sodium alginate oligosaccharide can be effectively embedded, slow release of water-soluble low-molecular-weight sodium alginate oligosaccharide is achieved, plant growth is promoted, abiotic stress of plants is relieved, and the slow-release effect is good. Sodium alginate oligosaccharides are provided at various stages of plant growth.

Description

Technical Field

[0001] The invention relates to the field of slow-release plant growth regulators, and in particular to a sodium alginate oligosaccharide plant growth regulator slow-release preparation and a preparation method thereof. Background Art

[0002] Plant growth regulators are a general term for natural plant hormones extracted from organisms and artificially synthesized chemical substances that regulate the growth and development of plants. This type of substance can effectively regulate the growth process of crops in agricultural production, achieving the goals of stabilizing and increasing production, improving quality, and enhancing crop resistance. However, excessive use of plant growth regulators not only fails to promote plant growth, but inhibits its growth, and in severe cases even causes leaf deformity, drying and falling, and death of the entire plant. Repeated use of plant growth regulators will waste a lot of manpower and material resources. Some growth regulators may have a negative impact on the environment, such as low solubility leading to residues or environmental pollution caused by difficult degradation. In agriculture, sustained-release preparations effectively reduce toxicity and side effects, extend the interval between applications, reduce drug waste, and ensure the crop protection effect and environmental friendliness of plant growth regulators by continuously releasing active ingredients. The use of degradable sustained-release carriers can not only naturally degrade after the active ingredients are released, reducing residues and environmental burden, but also control the release rate and time of the drug, ensuring a stable supply of active ingredients during plant growth, improving application efficiency and crop protection effects.

[0003] At present, the preparation process of the sustained-release technology of plant growth regulators is complicated, and chemical components such as organic solvents and surfactants with environmental toxicity are mostly used in the process. For water-soluble small molecule plant growth regulators, there are disadvantages such as difficult encapsulation, low encapsulation rate, and easy sudden release. Polysaccharides have some research and applications in the sustained-release of plant growth regulators. Slow or controlled release can be achieved by modifying and encapsulating plant growth regulators, thereby improving the bioavailability of these regulators in plants. However, the preparation method is relatively complicated and the cost is relatively high.

[0004] Sodium alginate oligosaccharide is a low-molecular plant growth regulator with good water solubility, strong elicitor activity and good application prospects. The present invention uses sodium alginate oligosaccharide as an active ingredient and chitosan as a slow-release carrier, and utilizes the electrostatic interaction between the two to synthesize a chitosan-based sodium alginate oligosaccharide plant growth regulator slow-release preparation, which has a simple preparation method, low material cost and easy availability, is environmentally friendly, and can reduce the loss of active ingredients caused by the degradation of sodium alginate oligosaccharide. Summary of the invention

[0005] In view of the defects of the prior art, the object of the present invention is to provide a chitosan-based sodium alginate oligosaccharide plant growth regulator sustained-release preparation and a preparation method thereof, so as to solve the problems raised in the background technology.

[0006] The present invention solves the technical problem by adopting the following technical solution:

[0007] The present invention provides a sodium alginate oligosaccharide plant growth regulating sustained-release preparation, characterized in that it comprises the following components: sodium alginate oligosaccharide as the main component and chitosan as the sustained-release carrier. ;

[0008] The preparation method is as follows:

[0009] a. Chitosan solution, the preparation method of which comprises mixing chitosan with an appropriate amount of deionized water, and adding 0.1-2% acetic acid or buffer solution under appropriate conditions to prepare a 0.1%-5% chitosan solution.

[0010] b. The preparation method of sodium alginate oligosaccharide solution is to dissolve sodium alginate oligosaccharide in deionized water or buffer solution, and mix the sodium alginate oligosaccharide uniformly at a certain stirring rate, wherein the concentration of the sodium alginate oligosaccharide is 0.1%-30%.

[0011] c. Slowly add different volumes of sodium alginate oligosaccharide solution to the chitosan solution, and prepare chitosan-sodium alginate oligosaccharide mixtures with different mixing ratios by magnetic stirring. After mixing evenly, the pH of the mixture can be adjusted with alkaline solution, and after appropriate stirring and centrifugation, vacuum freeze-drying is performed to obtain the final product.

[0012] The deacetylation degree of chitosan is 60%-99%.

[0013] The buffer solution may be phosphate buffer, acetate buffer, Tris-hydrochloric acid buffer, or the like.

[0014] The mixing ratio of chitosan and sodium alginate oligosaccharide is 1:0.001-1:100.

[0015] The conditions for vacuum freeze drying include precooling in a low temperature environment and vacuum drying at -50°C in a suitable vacuum dryer for 12-72 hours.

[0016] The alkali solution is alkali solution such as sodium hydroxide, potassium hydroxide, and ammonia water.

[0017] The pH of the mixture was adjusted to 6.4-7.4 using alkali solution.

[0018] The speed of the magnetic stirrer is 100-2000 rpm.

[0019] The centrifuge speed during the centrifugation process was 3000-12000 rpm, and the precipitate was washed 3-5 times with deionized water after centrifugation.

[0020] The molecular weight of sodium alginate oligosaccharide is 200-9000Da, and the molecular weight of chitosan is 20-700kDa.

[0021] Methods of applying the product include using it as a soil additive or seed coating.

[0022] The product application method can be adjusted according to crop type and growth stage to optimize the growth regulation effect.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The chitosan-based sodium alginate oligosaccharide plant growth regulator sustained-release preparation of the present invention is formed by the electrostatic interaction between the sodium alginate oligosaccharide solution and the chitosan solution, has good sustained-release performance, no sudden release phenomenon, and has a high encapsulation rate for the sodium alginate oligosaccharide. Chitosan is a natural polysaccharide extracted from the shell of crustaceans, has biocompatibility and degradability, can be degraded in the natural environment, and reduces pollution. The sodium alginate oligosaccharide solution of the present invention is formed by mixing and stirring sodium alginate oligosaccharide and deionized water, and the chitosan solution is formed by mixing and stirring chitosan, deionized water and acetic acid. The electrostatic interaction between the sodium alginate oligosaccharide solution and the chitosan solution is utilized to mix and stir the two solutions, and the described sodium alginate oligosaccharide sustained-release plant growth regulator based on chitosan is obtained after drying. The process does not involve chemical substances such as organic solvents that are easy to pollute the environment, and the process is simple and easy to scale up.

[0025] Due to the electrostatic interaction between sodium alginate oligosaccharides and chitosan, the plant growth regulator of the present invention can slow down the release of sodium alginate oligosaccharides, thereby avoiding the inhibitory effect on plant growth caused by applying too much sodium alginate oligosaccharides at one time. The chitosan-based sodium alginate oligosaccharide slow-release plant growth regulator of the present invention only needs to be applied once to provide sodium alginate oligosaccharides to plants at various stages of plant growth, thereby avoiding the loss of manpower and material resources caused by repeated application of plant growth regulators.

[0026] The sodium alginate oligosaccharide plant growth regulator sustained-release agent of the present invention is formulated through the electrostatic interaction between positively charged chitosan and negatively charged sodium alginate oligosaccharides, can effectively load sodium alginate oligosaccharides, achieve the sustained release of water-soluble low molecular weight sodium alginate oligosaccharides, promote plant growth and alleviate plant abiotic stress, and provide sodium alginate oligosaccharides at various stages of plant growth. DETAILED DESCRIPTION

[0027] The sodium alginate oligosaccharide plant growth regulating slow-release preparation of the present invention is formed by the electrostatic interaction between the sodium alginate oligosaccharide solution and the chitosan solution. The technical scheme in the embodiment of the present invention is clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described below are only embodiments of some commonly used proportions of the present invention, rather than all embodiments. The content of the present invention is not limited to the following embodiments. Based on the following embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0028] Example 1

[0029] Chitosan: average molecular weight 200kDa, deacetylation degree 85%

[0030] Sodium alginate oligosaccharide: average molecular weight 1000Da

[0031] Acetic acid: mass concentration 1%

[0032] Sodium hydroxide solution: 1M

[0033] Steps: Dissolve 1 gram of sodium alginate oligosaccharide in 99 milliliters of deionized water, stir evenly, and obtain a sodium alginate oligosaccharide solution with a mass concentration of 1%. Dissolve 2 grams of chitosan in 98 milliliters of acetic acid solution with a mass concentration of 1%, stir for 1 hour, and obtain a chitosan solution with a mass concentration of 2%. Slowly add the sodium alginate oligosaccharide solution to the chitosan solution and stir for 2 hours at a stirring rate of 600 rpm. Adjust the pH of the mixture to 7.0 with 1M sodium hydroxide solution. Centrifuge at 5000 rpm for 20 minutes, discard the supernatant, and wash the precipitate 3 times with deionized water. Precool the precipitate at -80°C for 3 hours, and then vacuum freeze-dry at -50°C for 48 hours.

[0034] Establish a standard curve of sodium alginate oligosaccharide concentration and absorbance: Take sodium alginate oligosaccharide solutions with mass concentrations of 0.01%, 0.02%, 0.03%, 0.04%, and 0.05%, respectively, and test their absorbance values ​​at 230nm in a UV-visible spectrophotometer to obtain the absorbance / concentration standard curve of sodium alginate oligosaccharide:

[0035] y=37.282x+0.079,R 2 =0.9963

[0036] The obtained product was dispersed in a 3M NaCl solution, and after centrifugation, the absorbance of the supernatant at 230 nm was tested by a UV-visible spectrophotometer to obtain the amount of sodium alginate oligosaccharides in the product. The encapsulation efficiency of sodium alginate oligosaccharides was tested using the following formula:

[0037]

[0038] Results: 1.47 g of product was prepared by the above steps. The mass ratio of chitosan to sodium alginate oligosaccharide was 1:1.199, and the loaded sodium alginate oligosaccharide was 80.18% of the initially added sodium alginate oligosaccharide (encapsulation efficiency).

[0039] Embodiment 2:

[0040] Chitosan: average molecular weight 150kDa, deacetylation degree 90%

[0041] Sodium alginate oligosaccharide: average molecular weight 1500Da

[0042] Phosphate buffer (pH 7.2)

[0043] Sodium hydroxide solution: 1M

[0044] Steps: Dissolve 2 grams of sodium alginate oligosaccharide in 98 milliliters of phosphate buffer and stir evenly to obtain a sodium alginate oligosaccharide solution with a mass concentration of 2%. Dissolve 1.5 grams of chitosan in 98.5 milliliters of phosphate buffer solution and stir for 1 hour to obtain a chitosan solution with a mass concentration of 1.5%. Slowly add the sodium alginate oligosaccharide solution to the chitosan solution and stir for 2 hours at a stirring rate of 800 rpm. Adjust the pH of the mixture to 7.2 with 1M sodium hydroxide solution. Centrifuge at 6000 rpm for 25 minutes, discard the supernatant, and wash the precipitate 3 times with deionized water. Precool the precipitate at -80°C for 3 hours, and then vacuum freeze-dry at -50°C for 60 hours.

[0045] The obtained product was dispersed in a 3M NaCl solution, and after centrifugation, the absorbance of the supernatant at 230 nm was tested by a UV-visible spectrophotometer to obtain the amount of sodium alginate oligosaccharides in the product.

[0046] Results: 2.84 g of product was prepared through the above steps. The mass ratio of chitosan to sodium alginate oligosaccharide was 1:1.204, and the encapsulation efficiency of sodium alginate oligosaccharide was 77.56%.

[0047] Embodiment 3:

[0048] Chitosan: average molecular weight 250kDa, deacetylation degree 85%

[0049] Sodium alginate oligosaccharide: average molecular weight 2500Da

[0050] Acetic acid: mass concentration 1%

[0051] Sodium hydroxide solution: 1M

[0052] Steps: Dissolve 1.5 grams of sodium alginate oligosaccharide in 98.5 milliliters of deionized water and stir evenly to obtain a sodium alginate oligosaccharide solution with a mass concentration of 1.5%. Dissolve 2 grams of chitosan in 98 milliliters of acetic acid solution with a mass concentration of 1%, stir for 1 hour, and obtain a chitosan solution with a mass concentration of 2%. Slowly add the sodium alginate oligosaccharide solution to the chitosan solution and stir for 2 hours at a stirring rate of 1000 rpm. Adjust the pH of the mixture to 6.5 with 1M sodium hydroxide solution. : Centrifuge at 8000 rpm for 20 minutes, discard the supernatant, and wash the precipitate 3 times with deionized water. : Precool the precipitate at -80°C for 3 hours, and then vacuum freeze-dry at -50°C for 48 hours.

[0053] The obtained product was dispersed in a 3M NaCl solution, and after centrifugation, the absorbance of the supernatant at 230 nm was tested by a UV-visible spectrophotometer to obtain the amount of sodium alginate oligosaccharides in the product.

[0054] Results: 2.24 g of product was prepared through the above steps. The mass ratio of chitosan to sodium alginate oligosaccharide was 1:1.229, and the encapsulation efficiency of sodium alginate oligosaccharide was 82.34%.

[0055] Embodiment 4:

[0056] Chitosan: average molecular weight 400kDa, deacetylation degree 75%

[0057] Sodium alginate oligosaccharide: average molecular weight 8000Da

[0058] Acetic acid: mass concentration 1%

[0059] Ammonia: 1%

[0060] Steps: Dissolve 1.2 grams of sodium alginate oligosaccharide in 98.8 milliliters of deionized water, stir evenly, and obtain a sodium alginate oligosaccharide solution with a mass concentration of 1.2%. Dissolve 1 gram of chitosan in 99 milliliters of acetic acid solution with a mass concentration of 1%, stir for 1 hour, and obtain a chitosan solution with a mass concentration of 1%. Slowly add the sodium alginate oligosaccharide solution to the chitosan solution and stir for 1.5 hours at a stirring rate of 1200 rpm. Adjust the pH of the mixture to 7.0 with 1M sodium hydroxide solution. Centrifuge at 7000 rpm for 20 minutes, discard the supernatant, and wash the precipitate 3 times with deionized water. Precool the precipitate at -80°C for 3 hours, and then vacuum freeze-dry at -50°C for 48 hours.

[0061] The obtained product was dispersed in 3M NaCl solution, centrifuged and the absorbance of the supernatant at 230nm was measured by UV-visible spectrophotometer to obtain the amount of sodium alginate oligosaccharide in the product.

[0062] Results: 1.78 g of product was prepared through the above steps, and the encapsulation efficiency was 82.9%.

[0063] Release experiment: 0.2g of the obtained product was placed in a 8000-14000Da (here 12000Da) dialysis bag and a blue-capped bottle containing 100ml of water and sodium dihydrogen phosphate / citric acid buffer solution of pH 5, 6, and 7 and Tris / hydrochloric acid buffer solution of pH 8 and 9 for release experiment. The blue-capped bottle was placed in a constant temperature culture shaker at 25±1°C and 150rpm. The dialysate was taken at regular intervals to test the absorbance at 230nm to test the amount of sodium alginate oligosaccharides released. The sodium alginate oligosaccharide cumulative release rate of the sodium alginate oligosaccharide slow-release plant growth regulator was calculated by dividing the amount of sodium alginate oligosaccharides released by the cumulative amount of sodium alginate oligosaccharides by the amount of sodium alginate oligosaccharides contained in the above material.

[0064] Through the release experiment, it was found that the sodium alginate oligosaccharide slow-release plant growth regulator released 2% in water in 1 hour, 15% in 5 hours, and 50% in 192 hours. Therefore, the sodium alginate oligosaccharide slow-release plant growth regulator has good slow-release performance. After 192 hours, the sodium alginate oligosaccharide slow-release plant growth regulator released 26.56% (pH=5), 39.45% (pH=6), 46.63% (pH=7), 51.34% (pH=8), and 59.74% (pH=9) in buffer solutions of different pH values, respectively.

[0065] Embodiment 5:

[0066] Chitosan: average molecular weight 100kDa, deacetylation degree 60%

[0067] Sodium alginate oligosaccharide: average molecular weight 6000Da

[0068] Acetic acid: mass concentration 1%

[0069] Potassium hydroxide solution: 1M

[0070] Steps: Dissolve 0.8 g of sodium alginate oligosaccharide in 99.2 ml of deionized water, stir evenly, and obtain a sodium alginate oligosaccharide solution with a mass concentration of 0.8%. Dissolve 1 g of chitosan in 99 ml of 1% acetic acid solution, stir for 1 hour, and obtain a chitosan solution with a mass concentration of 1%. Slowly add the sodium alginate oligosaccharide solution to the chitosan solution and stir for 2 hours at a stirring rate of 1500 rpm. Adjust the pH of the mixture to 7.2 with 1M sodium hydroxide solution. Centrifuge at 10,000 rpm for 30 minutes, discard the supernatant, and wash the precipitate with deionized water 5 times. Precool the precipitate at -80°C for 3 hours, and then vacuum freeze-dry at -50°C for 60 hours.

[0071] The obtained product was formulated into a 100ppm dispersion system and used for rice seed coating with 300mL per kilogram of rice seeds. In the seed germination stage, compared with uncoated and treated with chitosan and sodium alginate oligosaccharides of equal concentration and amount, the germination rate of rice seeds after coating was 84%, the germination rate of rice in the uncoated group was 72%, and the germination rate of rice seeds in the group treated with chitosan and sodium alginate oligosaccharides of equal doses was 77%. Finally, the per mu yield of rice coated with the sodium alginate oligosaccharide slow-release plant growth regulator was 415kg, the per mu yield of rice in the uncoated group was 330kg, and the per mu yield of rice treated with chitosan and sodium alginate oligosaccharides of equal doses was 360kg. After applying the sodium alginate oligosaccharide slow-release plant growth regulator, rice grows healthier and increases rice yield. The results show that the sodium alginate oligosaccharide slow-release plant growth regulator has the ability to promote rice growth.

[0072] Embodiment 6:

[0073] Chitosan: average molecular weight 30kDa, deacetylation degree 85%

[0074] Sodium alginate oligosaccharide: average molecular weight 6000Da

[0075] Acetic acid: mass concentration 1%

[0076] Dissolve 1.2 g of sodium alginate oligosaccharide in 118.8 ml of deionized water and stir evenly to obtain a sodium alginate oligosaccharide solution with a mass concentration of 1%. Dissolve 1 g of chitosan in 99 ml of acetic acid solution with a mass concentration of 1%, stir for 1 hour, and obtain a chitosan solution with a mass concentration of 1%. Slowly add the sodium alginate oligosaccharide solution to the chitosan solution and stir for 3 hours at a stirring rate of 500 rpm. Centrifuge at 10,000 rpm for 30 minutes, discard the supernatant, and wash the precipitate with deionized water 5 times. Precool the precipitate and vacuum freeze-dry it at -50°C for 48 hours.

[0077] Moderate saline-alkali soil with a pH of 7.1-8.0 and a salt content of 0.4% was selected, and the obtained product was applied as a soil additive at a concentration of 50 mg / kg soil. At the same time, the control group treated the soil with the same amount of chitosan and sodium alginate oligosaccharides. After flotation and disinfection, the rice seeds were cultured in an incubator until the three-leaf stage and then transplanted into soils with different treatments. After three months, the various indicators of mature rice were recorded. Finally, the average plant height of the rice treated with the sodium alginate oligosaccharide-based slow-release plant growth regulator was 77 cm, and the per mu yield was 390 kg. The average plant height of the rice treated with chitosan and sodium alginate oligosaccharides was 71 cm, and the per mu yield was 350 kg. The results show the long-term performance of the sodium alginate oligosaccharide slow-release plant growth regulator in promoting rice growth and its ability to alleviate rice salt-alkali stress.

[0078] It can be concluded from the examples that the chitosan-based sodium alginate oligosaccharide plant growth regulator slow-release preparation of the invention has excellent sodium alginate oligosaccharide encapsulation efficiency. Compared with the simple application of sodium alginate oligosaccharide, the chitosan-based sodium alginate oligosaccharide slow-release plant growth regulator has good sodium alginate oligosaccharide slow-release performance, and can continuously provide sodium alginate oligosaccharides at different stages of plant growth to promote plant growth.

[0079] It is also found that in an alkaline environment, the chitosan-based sodium alginate oligosaccharide slow-release plant growth regulator has a higher release rate.

[0080] It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and not every embodiment includes only one independent technical solution. The description of the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole. Therefore, the above embodiments are not used to limit the present invention, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A sodium alginate oligosaccharide plant growth regulator sustained-release preparation, characterized in that: The ingredients included are: chitosan and sodium alginate oligosaccharide; The mixing mass ratio of chitosan to sodium alginate oligosaccharide is 1:0.001-1:100, preferably 1:0.1-1:10, more preferably 1:0.3-1:3 sodium alginate oligosaccharide.

2. The sodium alginate oligosaccharide plant growth regulating sustained-release preparation according to claim 1, characterized in that: Sodium alginate oligosaccharide is used as the main component, and chitosan is used as a sustained-release carrier; The deacetylation degree of chitosan is 60%-99%, preferably 70-99%, more preferably 85-99%; The molecular weight of the sodium alginate oligosaccharide is 200-9000Da, preferably 500-9000Da, more preferably 1000-9000Da; the molecular weight of the chitosan is 20-700kDa, preferably 50-600kDa, more preferably 100-500kDa.

3. A method for preparing the sodium alginate oligosaccharide plant growth regulating sustained-release preparation according to claim 1 or 2, characterized in that: a. Preparation of chitosan solution: chitosan is added to an aqueous solution of acetic acid or a buffer solution having a mass concentration of 0.1-2% to prepare a chitosan solution having a mass concentration of 0.1%-5% (preferably 0.5%-3%, more preferably 0.8%-2%); Preparation of sodium alginate oligosaccharide solution: dissolving sodium alginate oligosaccharide in deionized water or buffer solution, stirring to make the sodium alginate oligosaccharide mix evenly, wherein the concentration of the sodium alginate oligosaccharide is 0.1%-30% (preferably 0.5%-10%, more preferably 0.8%-2%); c. Mixing the sodium alginate oligosaccharide solution with the chitosan solution, after uniform mixing, adding no or alkali solution to adjust the pH of the mixture, and performing vacuum freeze drying after stirring and centrifugation to obtain the final product.

4. The preparation method according to claim 3, characterized in that: The buffer solution may be one or more of phosphate buffer, acetate buffer, Tris-hydrochloric acid buffer, etc.; The alkali solution is one or more alkali solutions selected from 0.5-2M sodium hydroxide, 0.5-2M potassium hydroxide, 1-3M ammonia water, etc.; the pH range of the mixture is adjusted to 6.4-7.4 by the alkali solution.

5. The preparation method according to claim 3, characterized in that: The vacuum freeze drying conditions include precooling in a low temperature environment (temperature -85℃—-70℃, time 3h—5h), and vacuum drying in a vacuum dryer at -60℃—-40℃ for 12-72h; The speed of the magnetic stirrer is 100-2000rpm; The centrifuge speed during the centrifugation process was 3000-12000 rpm, and the precipitate was washed 3-5 times with deionized water after centrifugation.

6. Use of the sodium alginate oligosaccharide plant growth regulating slow-release preparation according to claim 1 or 2 as a soil additive or seed coating agent.

7. The use according to claim 6, characterized in that: The soil additive or coating agent is used in an amount of 20ppm-300ppm relative to the soil or dispersion.

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