A cyanobacteria-based plant stimulant and preparation method thereof

Abstract

The invention discloses a method for preparing a cyanobacteria-based plant stimulant, comprising first adding a solid acid and a catalyst to a cyanobacteria aqueous solution, stirring and then heating to obtain a cyanobacteria hydrolyzate; then performing solid-liquid separation on the cyanobacteria hydrolyzate, using an alkaline solution to adjust the pH of the supernatant to make the supernatant neutral, and obtaining a cyanobacteria-based plant stimulant. Using a solid acid to catalyze the acid-hot hydrolysis reaction of the cyanobacteria aqueous solution and preparing the cyanobacteria-based plant stimulant helps to promote the dissolution of nutrients in the cyanobacteria and the decomposition of macromolecular organic matter such as proteins, thereby increasing the yield of the cyanobacteria-based plant stimulant; using inorganic acids and organic acids loaded with nano-silicon dioxide to catalyze the acid-hot hydrolysis reaction of the cyanobacteria can further increase the hydrolysis efficiency of the cyanobacteria and further increase the yield of the cyanobacteria-based plant stimulant. The cyanobacteria-based stimulant obtained by the method of the invention not only contains a relatively high content of total phosphorus, total potassium and amino acids, but also contains nutrients such as soluble proteins, polypeptides, and polysaccharides.

Description

Technical Field

[0001] The invention relates to a cyanobacteria-based plant stimulant and a preparation method thereof, belonging to the technical field of environmental engineering. Background Art

[0002] The total amount of inorganic fertilizers and pesticides used is large, and the cumulative risk of soil pollution in agricultural land is also high. Although the application of inorganic fertilizers and pesticides will increase crop yields and income, it will lead to a decline in crop quality and pose potential health threats and ecological risks. Strengthening soil pollution control and remediation, strengthening agricultural non-point source pollution prevention and control, high-value utilization of agricultural and forestry wastes, and reducing greenhouse gas emissions have become the focus of soil prevention and resource utilization. Studies have found that the application of organic fertilizers and cyanobacteria-based plant stimulants can improve soil quality, and the addition of biochar is conducive to increasing the soil carbon pool capacity. Therefore, the research and development of organic fertilizers and cyanobacteria-based plant stimulants, the application of organic fertilizers and cyanobacteria-based plant stimulants based on agricultural and forestry residues, and the coupling of biochar to enhance carbon fixation and emission reduction have become the key to the development of the industry. Organic fertilizers are mainly derived from biomass, including animal and plant waste, plant residues, etc. They are carbon-containing materials applied to the soil to provide plant nutrition. Their main components are organic acids, peptides and amino acids, etc. They can provide comprehensive nutrition for crops and promote microbial reproduction. They are the main nutrient source for green food production. Cyanobacteria-based plant stimulants are derived from active substances that exist naturally in nature. They can improve the physiological and biochemical state of crops, enhance the effectiveness of pesticides and the utilization rate of fertilizers, and improve the level of crops' resistance to adversity. They also have the function of improving the soil and increasing the final yield and product quality of crops.

[0003] The production of cyanobacteria in agricultural waste in the Taihu Lake Basin is huge. At present, cyanobacteria are generally treated and disposed of by the method of "deep dehydration-incineration". Although incineration can effectively reduce the secondary pollution of cyanobacteria to the environment, the "deep dehydration-incineration" method is not conducive to resource recycling because cyanobacteria contain a large amount of organic matter and elements such as nitrogen and phosphorus. Cyanobacteria are a biomass resource rich in protein (content of about 38-47%) and polysaccharides (cyanobacterial starch, cellulose). If high-value-added products in cyanobacteria can be extracted and prepared into organic fertilizer or cyanobacterial-based plant stimulants, it can not only increase and renew soil organic matter, but also improve the physical and chemical properties of the soil, increase microbial activity, and ultimately achieve the goal of improving soil quality. Therefore, exploring new ways to utilize cyanobacteria resources is of great practical significance.

[0004] Blue algae are usually treated and disposed of by "deep dehydration-incineration". However, blue algae contain a large amount of organic matter and elements such as nitrogen and phosphorus, and the "deep dehydration-incineration" method is not conducive to resource recycling. Therefore, exploring new ways to utilize blue algae resources has great practical significance. Summary of the invention

[0005] The present invention aims to provide a cyanobacteria-based plant stimulant and a preparation method thereof, that is, adding a solid acid into a cyanobacteria aqueous solution to cause the cyanobacteria to undergo an acid-thermal hydrolysis reaction, dissolve the nutrients in the cyanobacteria, decompose macromolecular organic matter such as proteins, and prepare the cyanobacteria-based plant stimulant to replace chemical fertilizers to provide nutrients for plants, promote plant growth, and realize resource utilization of cyanobacteria.

[0006] One of the purposes of the present invention is to provide a method for preparing a cyanobacteria-based plant stimulant, comprising the following steps:

[0007] (1) adding a solid acid and a catalyst to a cyanobacteria aqueous solution, stirring and heating, and obtaining a cyanobacteria hydrolyzate;

[0008] (2) The cyanobacteria hydrolyzate in step (1) is subjected to solid-liquid separation, and the pH of the supernatant is adjusted using an alkaline solution to make the supernatant neutral, thereby obtaining a cyanobacteria-based plant stimulant.

[0009] Cyanobacteria-based plant stimulants are a type of substance or microorganism made from cyanobacteria that is used to promote plant growth and development, alleviate abiotic stress and improve crop quality. It is not a traditional fertilizer or pesticide. It improves the physiological state of plants and enhances their stress resistance by acting on the crops themselves.

[0010] Compared with traditional liquid acids, solid acid catalysts have the advantages of easy separation, non-corrosiveness and continuous production. At the same time, they conform to the concept of green environmental protection and are widely used in various acid-catalyzed reactions. Appropriate proton acids such as H 2 SO 4 , H 3 PO 4 , HCl and HNO 3 The solid acid can be impregnated on a suitable carrier (zeolite, silica, diatomaceous earth) to prepare solid acid. The solid acid has low corrosion to the equipment, is easy to separate and recycle, has good high temperature stability, can be activated and regenerated, and reduces the discharge of waste. The use of solid acid to catalyze the acid-thermal hydrolysis reaction of cyanobacteria aqueous solution helps to promote the dissolution of nutrients in cyanobacteria and the decomposition of macromolecular organic matter such as protein, thereby increasing the yield of cyanobacteria-based plant stimulants.

[0011] The blue algae aqueous solution involved in the present invention comes from an algae-water mixture collected from an algae-water separation station.

[0012] In one embodiment of the present invention, the solid acid comprises an inorganic acid or an organic acid supported on a carrier, and the carrier comprises at least one of bentonite, montmorillonite, kaolin, diatomaceous earth, and nano-silicon dioxide.

[0013] In one embodiment of the present invention, the solid acid is an inorganic acid or an organic acid loaded on nano-silicon dioxide. Nano-silicon dioxide is an acidic oxide and a widely used polar inorganic oxide, which has the advantages of complex pore structure, large pore volume, large specific surface area, strong adsorption capacity, etc. Anchoring the acid group on nano-silicon dioxide strengthens the performance of the solid acid and helps to further increase the yield of cyanobacteria-based plant stimulants.

[0014] In one embodiment of the present invention, the inorganic acid includes at least one of sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid, and the organic acid includes acetic acid or oxalic acid.

[0015] In one embodiment of the present invention, the mass fractions of the sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid are 95-98%, 32-36%, 80-85% and 62-68% respectively, and the mass fraction of the oxalic acid is 40-60%.

[0016] In one embodiment of the present invention, the amount of solid acid added is 1-10% of the mass of the blue algae aqueous solution.

[0017] In one embodiment of the present invention, the preparation method of the solid acid comprises: adding inorganic acid or organic acid to nano-silicon dioxide, mixing evenly, heating to 80° C., performing solid-liquid separation after immersion, and drying the solid to obtain the solid acid.

[0018] In one embodiment of the present invention, the catalyst comprises at least one of a soluble iron salt, a calcium salt, a zinc salt, a potassium salt, and a sodium salt.

[0019] In one embodiment of the present invention, the alkaline solution is a potassium hydroxide solution, and the mass fraction of the potassium hydroxide solution is 1-10%.

[0020] In one embodiment of the present invention, in step (1), the stirring speed is 40 to 150 r / min, the heating temperature is 80 to 100° C., and the heating time is 7 to 48 h.

[0021] In one embodiment of the present invention, in step (1), after adding the solid acid and the catalyst, the pH of the cyanobacteria aqueous solution is 0.8 to 4.2.

[0022] In one embodiment of the present invention, the water content of the blue algae aqueous solution is 95-98%.

[0023] In one embodiment of the present invention, in step (2), the solid-liquid separation method comprises performing solid-liquid separation on the cyanobacteria hydrolyzate by vacuum filtration.

[0024] In one embodiment of the present invention, step (2) further includes a step of removing water from the supernatant.

[0025] The second object of the present invention is to provide a cyanobacteria-based stimulant obtained using the above method.

[0026] The third object of the present invention is to provide a cyanobacteria-based plant stimulant for use in the cultivation of agricultural and forestry crops.

[0027] In one embodiment of the present invention, the use comprises improving soil using cyanobacteria-based plant stimulants.

[0028] Beneficial effects of the present invention:

[0029] 1. Using solid acid to catalyze the acid-thermal hydrolysis reaction of cyanobacteria aqueous solution and prepare cyanobacteria-based plant stimulants can help promote the dissolution of nutrients in cyanobacteria and the decomposition of macromolecular organic matter such as proteins, and increase the yield of cyanobacteria-based plant stimulants; on the other hand, solid acid has low corrosion to equipment, waste is easy to separate and recycle, and has good high-temperature stability.

[0030] 2. Nano-silica has a large pore volume, a large specific surface area, and a strong adsorption capacity. The acid groups are anchored on the nano-silica, which increases the adsorption amount and stability of the acid. When inorganic acids and organic acids loaded with nano-silica are used to catalyze the acid-thermal hydrolysis reaction of cyanobacteria, the hydrolysis efficiency of cyanobacteria can be further increased, and the yield of cyanobacteria-based plant stimulants can be further improved.

[0031] 3. The cyanobacteria-based stimulant obtained by the method of the present invention has a total nitrogen content of up to 80.55 g / kg, a total phosphorus content of 12.5 g / kg, and a free amino acid content of 77.62 g / kg, which are much higher than the existing sludge alkaline protein nutrients and cyanobacteria compost fertilizer nutrients. The cyanobacteria-based stimulant also contains soluble proteins, polypeptides, polysaccharides and other nutrients. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The effect of the types of solid acid on the nutrients and content in the prepared cyanobacteria-based plant stimulants;

[0033] Figure 2 The effect of the amount of solid acid added on the nutrients and content in the prepared cyanobacteria-based plant stimulant;

[0034] Figure 3 Effect of catalyst types on nutrients and content in prepared cyanobacteria-based plant stimulants DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0036] Example 1 Preparation of cyanobacteria-based plant stimulants

[0037] ① Preparation of solid acid

[0038] Take 20g of amorphous nano-silica, and wash it with 0.1mol / L NaOH and 0.1mol / L HCl successively; add sulfuric acid to the washed nano-silica, mix well, immerse at 80°C for 24h, separate the solid-liquid of the mixed solution, and place the solid in a 120°C oven to dry to obtain a solid acid.

[0039] ② Preparation of cyanobacteria-based plant stimulants

[0040] Take 2500g of salvaged cyanobacteria aqueous solution, with a water content of about 98%, and add it into a glass reactor. Slowly add the solid acid obtained in step ① and 20g of sodium sulfate into the glass reactor. The amount of solid acid added is 2% of the mass of the cyanobacteria aqueous solution. Use sulfuric acid to adjust the pH of the mixed solution to obtain a mixed solution with a pH of 2. Heat the mixed solution to 100°C and react for 7 hours to obtain a cyanobacteria hydrolyzate. Use a vacuum filtration device to separate the cyanobacteria hydrolyzate into solids and liquids, add a 10% potassium hydroxide solution by mass to the supernatant obtained by separation, adjust the pH of the supernatant to 7, and obtain a cyanobacteria-based plant stimulant. Determine the content of nitrogen, phosphorus, potassium and other nutrients in the cyanobacteria-based plant stimulant, and record the results in Table 1, where total phosphorus is expressed as P 2 O 5 Total potassium is K 2 O plan.

[0041] Table 1 Nutrients and their contents in cyanobacteria-based stimulants

[0042] Nutrients Total Nitrogen Total Phosphorus Total Potassium (before pH adjustment) Total Potassium (after pH adjustment) Free amino acids Organic matter Soluble protein Peptides Polysaccharides Content (g / kg) 80.55 12.5 4.526 5.617 77.62 72.12 0.488 3.115 25.004

[0043] The results showed that cyanobacteria-based plant stimulants not only have high levels of total nitrogen, total phosphorus, total potassium and free amino acids, but also contain nutrients such as soluble protein, polypeptides, polysaccharides, etc. Using potassium hydroxide as a pH regulator can further increase the total potassium content in plant stimulants.

[0044] Example 2 Effect of solid acid types on the nutrient content of cyanobacteria-based plant stimulants

[0045] Take 20g of amorphous nano-silicon dioxide, rinse with 0.1mol / L NaOH and 0.1mol / L HCl; mix the nano-silicon dioxide with 98%, 65%, 35%, 50% sulfuric acid, nitric acid, hydrochloric acid and oxalic acid, respectively, keep the temperature at 80℃, and immerse for 24h; separate the acid loaded with nano-silicon dioxide from the acid solution, and dry the solid in a 120℃ oven. Take 8000ml of cyanobacteria aqueous solution with a water content of 98%, divide it into 4 groups and add it to a glass reactor, slowly add sulfuric acid, nitric acid, oxalic acid and hydrochloric acid loaded with nano-silicon dioxide, the group numbers are R1, R2, R3 and R4 respectively, the amount of solid acid added is 2% of the mass of the cyanobacteria aqueous solution, and then add the corresponding acid solution to each group to adjust the pH value to 2, and heat and hydrolyze for 7h. After the reaction is completed, vacuum filtration is used for solid-liquid separation to obtain a transparent yellow-brown liquid with a pH of about 2. The pH of the cyanobacteria hydrolyzate was adjusted to 7 using 10% potassium hydroxide to obtain cyanobacteria-based plant stimulants. The contents of various nutrients in the cyanobacteria-based plant stimulants were determined. The results are as follows: Figure 1 shown.

[0046] The results showed that the cyanobacteria-based plant stimulants prepared using sulfuric acid, nitric acid, oxalic acid and hydrochloric acid loaded with nano-silica as solid acids all had high contents of P 2 O 5 and P-PO 4 3- When oxalic acid loaded with nano-silica is used as solid acid, the prepared cyanobacteria-based plant stimulant contains less K 2 O, its concentration is less than 50mg / L. The cyanobacteria-based plant stimulant prepared using sulfuric acid loaded with nano-silica as solid acid contains a higher content of Kjeldahl nitrogen, which is much higher than the other three solid acids.

[0047] Example 4 Effect of the amount of solid acid added on the nutrient content of cyanobacteria-based plant stimulants

[0048] Take 20g of amorphous nano-silica, and rinse it with NaOH with a concentration of 0.1mol / L and HCl with a concentration of 0.1mol / L; mix the nano-silica with 98% sulfuric acid by mass, maintain the temperature at 80℃, and immerse for 24h; separate the nano-silica loaded with sulfuric acid from the acid solution, and place the solid in a 120℃ oven for drying. Collect 8000ml of cyanobacteria aqueous solution with a water content of 98% from the algae-water separation station, divide it into 3 groups and add it to the glass reactor, the group numbers are R1, R2, and R3, respectively. Sulfuric acid-loaded nano-silica is slowly added according to the mass fraction of 1%, 2%, and 10% of the cyanobacteria aqueous solution, and hydrolyze and heat for 7h. After the reaction is completed, vacuum filtration is used for solid-liquid separation to obtain a transparent yellow-brown liquid with a pH of 1. Use potassium hydroxide with a mass fraction of 10% to adjust the pH of the cyanobacteria hydrolyzate to 7 to obtain cyanobacteria-based plant stimulants, and determine the content of each nutrient in the cyanobacteria-based plant stimulants. The results are as follows Figure 2 shown.

[0049] The results showed that adding 1-10% solid acid to the cyanobacteria aqueous solution could make the prepared plant stimulant contain a higher content of P 2 O 5 , K 2 O and P-PO 4 3- , when the mass fraction of solid acid is 1%, the decomposition performance of macromolecules in the cyanobacteria aqueous solution is poor, and the content of Kjeldahl nitrogen obtained is low.

[0050] Example 5: Effect of Catalyst Type on the Content of Nutrients in Cyanobacteria-Based Plant Stimulants

[0051] Take 20g of amorphous nano-silica, rinse with 0.1mol / L NaOH and 0.1mol / L HCl successively; mix the amorphous nano-silica with 98% sulfuric acid, keep the temperature at 80℃, and soak for 24h; separate the amorphous nano-silica from the acid, and place the solid in a 120℃ oven to dry to obtain solid acid. Collect 10L of cyanobacteria aqueous solution with a water content of 98% from the algae-water separation station, divide it into 5 groups and add it to the glass reactor, add 20g of potassium sulfate, iron sulfate, zinc sulfate, sodium sulfate, and calcium sulfate to the reactor respectively, and the group numbers are R1, R2, R3, R4, and R5 respectively, and slowly add 2% of the mass of the cyanobacteria aqueous solution to the solid acid, and hydrolyze and heat for 7h. After the reaction is completed, vacuum filtration is used for solid-liquid separation to obtain a transparent yellow-brown liquid with a pH of 2. The pH of the cyanobacteria hydrolyzate was adjusted to 7 using 10% potassium hydroxide to obtain cyanobacteria-based plant stimulants. The contents of various nutrients in the cyanobacteria-based plant stimulants were determined. The results are as follows: Figure 3 shown.

[0052] The results showed that, in general, the type of catalyst had little effect on the nutrient content of cyanobacteria-based plant stimulants. Using potassium sulfate as a catalyst could further increase the Kjeldahl nitrogen content in cyanobacteria-based plant stimulants. 2 O 5 The content is the highest, and the catalytic effect of calcium sulfate is relatively poor, especially in promoting the decomposition of macromolecules in cyanobacteria.

[0053] Comparative Example 1: Comparison of nutrients and contents of cyanobacteria-based plant stimulants and sludge alkaline protein

[0054] The cyanobacteria-based plant stimulant prepared in Example 1 and the nutrients in the existing sludge alkaline protein were tested, and the content of each nutrient is recorded in Table 2, where total phosphorus is expressed as P 2 O 5 Total potassium is K 2 O plan.

[0055] The results showed that the total nitrogen and total phosphorus content in cyanobacteria-based plant stimulants was twice that of sludge alkaline protein. Although the potassium content in cyanobacteria hydrolyzate was low, the low potassium content in cyanobacteria-based plant stimulants could be effectively compensated after pH adjustment using potassium hydroxide. The organic matter content of cyanobacteria-based plant stimulants is roughly the same as that of sludge alkaline protein. Applying rich organic matter to the soil can improve the soil's fertility and water retention. At the same time, the higher the organic matter content, the more active the microbial activity in the soil. The free amino acid content of cyanobacteria-based plant stimulants is 143% higher than that of sludge alkaline protein. The rich amino acids can provide plants with more nitrogen sources and promote plant growth. In addition, cyanobacteria-based plant stimulants are rich in polysaccharides and polypeptides, among which polysaccharides can shorten the synthesis path of substances required by plants during synthetic growth and development.

[0056] Table 2 Comparison of nutrient elements between cyanobacteria-based plant stimulants and sludge alkaline protein

[0057] Nutritional indicators Cyanobacteria-based plant stimulants Sludge Alkaline Protein Nutrients Total nitrogen (g / kg) 80.55 47.4 Total phosphorus (g / kg) 12.5 6.4 Total potassium (g / kg) (before pH adjustment) 4.526 5.33 Total potassium (g / kg) (after pH adjustment) 5.617 5.33 Free amino acids (g / kg) 77.62 31.85 Organic matter (g / kg) 72.12 72.3 Soluble protein (g / kg) 0.488 / Peptide (g / kg) 3.115 / Polysaccharide (g / kg) 25.004 /

[0058] Comparative Example 2: Comparison of nutrients and content between cyanobacteria-based plant stimulants and cyanobacteria compost fertilizer

[0059] The nutrients and contents of the cyanobacteria-based plant stimulant prepared in Example 1 and the existing cyanobacteria compost fertilizer were tested, and the results are recorded in Table 3, where total phosphorus is expressed as P 2 O 5 Total potassium is K 2 O plan.

[0060] The results showed that the total nitrogen content of cyanobacteria-based plant stimulants was 2.5 times that of nutrients in compost fertilizers, while the total phosphorus concentration was 300% higher than that of compost fertilizers. The total potassium content was relatively higher than that of compost fertilizers. After adjusting the pH value with potassium hydroxide, the total potassium content could reach 189% of the total potassium content of compost fertilizers. Because the process of cyanobacteria compost fertilizers is relatively simple, it was found that they did not contain free amino acids, soluble proteins, polysaccharides and polypeptides. The contents of the above substances in cyanobacteria-based plant stimulants were as high as 77.62, 0.488, 3.115 and 25.004 g / kg, respectively. Polysaccharides are easier to be absorbed and utilized by plants and are more likely to promote plant growth. The relatively high content of free amino acids and polypeptides provides a stable material basis for plant growth and soil quality improvement.

[0061] Table 3 Comparison of nutrient elements between cyanobacteria-based plant stimulants and cyanobacteria compost fertilizer

[0062] Nutritional indicators Cyanobacteria-based plant stimulants Cyanobacteria compost fertilizer nutrients Total nitrogen (g / kg) 80.55 30.56 Total phosphorus (g / kg) 12.5 3.15 Total potassium (g / kg) (before pH adjustment) 4.526 2.97 Total potassium (g / kg) (before pH adjustment) 5.617 2.97 Free amino acids (g / kg) 77.62 / Soluble protein (g / kg) 0.488 / Peptide (g / kg) 3.115 / Polysaccharide (g / kg) 25.004 /

[0063] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a cyanobacteria-based plant stimulant, characterized in that: The following steps are involved: (1) adding a solid acid and a catalyst to a cyanobacteria aqueous solution, stirring and heating, and obtaining a cyanobacteria hydrolyzate; The cyanobacteria hydrolyzate in step (1) is subjected to solid-liquid separation, and the pH of the supernatant is adjusted with an alkaline solution to make the supernatant neutral, thereby obtaining a cyanobacteria-based plant stimulant; the solid acid is sulfuric acid loaded on nano-silicon dioxide, and the mass fraction of the sulfuric acid is 95-98%; the amount of the solid acid added is 2-10% of the mass of the cyanobacteria aqueous solution.

2. The method for preparing the cyanobacteria-based plant stimulant according to claim 1, characterized in that: The catalyst includes at least one of soluble iron salt, calcium salt, zinc salt, potassium salt and sodium salt.

3. The method for preparing the cyanobacteria-based plant stimulant according to claim 1, characterized in that: In step (1), the stirring speed is 40 to 150 r / min, the heating temperature is 80 to 100° C., and the heating time is 7 to 48 h.

4. The method for preparing the cyanobacteria-based plant stimulant according to claim 1, characterized in that: In step (1), after adding the solid acid and the catalyst, the pH of the blue algae aqueous solution is 0.8 to 4.

2.

5. The method for preparing the cyanobacteria-based plant stimulant according to claim 1, characterized in that: The water content of the blue algae aqueous solution is 95-98%.

6. A cyanobacteria-based stimulant obtained by the method for preparing a cyanobacteria-based phytostimulant according to any one of claims 1 to 5.

7. Use of the cyanobacteria-based plant stimulant according to claim 6 in the cultivation of agricultural and forestry crops.

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