Biomass-based microcapsule loaded with nitrogen source as well as preparation method and application of biomass-based microcapsule

Abstract

The invention belongs to the technical field of microcapsule production, and particularly relates to a biomass-based microcapsule loaded with a nitrogen source as well as a preparation method and application of the biomass-based microcapsule. The invention provides a nitrogen source-loaded biomass-based microcapsule. The nitrogen source-loaded biomass-based microcapsule comprises a biomass-based microcapsule and an organic nitrogen source wrapped in the biomass-based microcapsule, the mass ratio of the organic nitrogen source to the biomass-based microcapsules is (30-35): (3-7). The raw materials of the biomass-based microcapsule loaded with the nitrogen source are easy to obtain and environmentally friendly, and the biomass-based microcapsule is of a hollow structure and can efficiently load the organic nitrogen source and slowly release the organic nitrogen source, so that nutrients can be continuously provided for microorganisms for decomposing straw, and nutrient circulation is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of microcapsule production, and in particular relates to a biomass-based microcapsule loaded with a nitrogen source, and a preparation method and application thereof. Background Art

[0002] Straw incorporation into fields is an important agronomic practice that can effectively improve soil physical and chemical properties. Existing technologies primarily promote straw composting by applying microbial agents to the straw. The carbon-to-nitrogen ratio (C / N) is a key factor influencing straw decomposition. The C / N ratio of straw itself is as high as 60:1 to 100:1, while the optimal C / N ratio for microorganisms is 25:1 to 30:1. If the C / N ratio is too high, microbial growth will be hindered due to insufficient nitrogen, resulting in a decreased decomposition rate and a prolonged decomposition cycle. Furthermore, microorganisms are forced to compete with crops for available nitrogen in the soil, leading to "nitrogen starvation," manifested in the field as yellowing and stagnant crop growth. Existing technologies typically reduce the C / N ratio by adding nitrogen sources. This addition of nitrogen sources can activate microbial activity, accelerate straw decomposition, reduce the accumulation of harmful intermediates, and promote humus formation. However, nitrogen application to the soil is susceptible to factors such as temperature, pH, and weather, which can reduce fertilizer efficiency.

[0003] Some existing studies use biochar as a nitrogen source carrier, but biochar has low nitrogen loading efficiency, and the alkaline conditions of biochar may affect microbial activity. Therefore, how to provide a nitrogen source carrier that can efficiently load nitrogen sources and release nitrogen sources in the field in a long-term and stable manner without affecting microbial activity, thereby improving the composting effect of microbial inoculants on straw, has become an urgent problem in this field. Summary of the Invention

[0004] In order to solve the problems in the prior art of low nitrogen source loading efficiency, poor sustained release effect, and easy impact on microbial activity of nitrogen source carriers, the present invention provides a biomass-based microcapsule loaded with nitrogen source and its preparation method and application, which specifically includes the following technical solutions:

[0005] The present invention provides a biomass-based microcapsule loaded with a nitrogen source, comprising a biomass-based microcapsule and an organic nitrogen source wrapped inside the biomass-based microcapsule; the mass ratio of the organic nitrogen source to the biomass-based microcapsule is 30-35:3-7.

[0006] Preferably, the raw materials of the biomass-based microcapsules include: an aqueous phase component, an oil phase component, sodium lignin sulfonate and chitosan; the aqueous phase component includes alkali lignin and water; the oil phase component includes an organic solvent and / or edible oil; the mass ratio of chitosan to sodium lignin sulfonate is 1 to 3:10; the mass ratio of alkali lignin to chitosan is 1 to 3:2 to 5.

[0007] Preferably, the mass volume ratio of the alkali lignin and water is 0.5-2 g:100 mL; the water includes deionized water; the organic solvent includes any one or more of toluene, cyclohexane, n-hexane and / or cyclohexanone; the edible oil includes soybean oil, peanut oil or vegetable blended oil; the volume ratio of the aqueous phase component to the oil phase component is 4:1.

[0008] The present invention also provides a method for preparing the above-mentioned biomass-based microcapsules loaded with nitrogen source, comprising the following steps:

[0009] Adjusting the pH of the aqueous phase component to 2-3 to obtain an alkali lignin particle dispersion;

[0010] Mixing the alkali lignin particle dispersion with the oil phase component and homogenizing to obtain an alkali lignin-based Pickering emulsion;

[0011] dissolving chitosan and sodium lignin sulfonate to obtain a chitosan solution and a sodium lignin sulfonate solution;

[0012] The alkali lignin-based Pickering emulsion, chitosan solution and sodium lignin sulfonate are mixed and freeze-dried to obtain biomass-based microcapsules;

[0013] The biomass-based microcapsules and the organic nitrogen source are mixed in proportion to obtain biomass-based microcapsules loaded with the nitrogen source.

[0014] Preferably, the chitosan is dissolved in acetic acid solution to obtain a chitosan solution; the volume concentration of the acetic acid solution is 1% to 2%; and the mass concentration of chitosan in the chitosan solution is 0.1% to 0.3%.

[0015] Preferably, the sodium lignin sulfonate is dissolved in water to obtain a sodium lignin sulfonate solution; the water is deionized water; and the mass concentration of sodium lignin sulfonate in the sodium lignin sulfonate solution is 1% to 2%.

[0016] Preferably, the method of mixing the alkali lignin-based Pickering emulsion, chitosan solution and sodium lignin sulfonate comprises: alternately adding chitosan solution and sodium lignin sulfonate to the alkali lignin-based Pickering emulsion in sequence; the number of times of alternate addition is 1 to 15 times.

[0017] The present invention also provides a composition comprising biomass-based microcapsules loaded with a nitrogen source and microorganisms;

[0018] The biomass-based microcapsules loaded with nitrogen sources are the biomass-based microcapsules loaded with nitrogen sources as described above or the biomass-based microcapsules loaded with nitrogen sources prepared by the preparation method.

[0019] Preferably, the microorganisms include Bacillus subtilis and Bacillus cereus; the deposit number of the Bacillus subtilis is ACCC62095; the deposit number of the Bacillus cereus is ACCC62096.

[0020] The present invention also provides the use of the nitrogen source-loaded biomass-based microcapsules or the nitrogen source-loaded biomass-based microcapsules or compositions prepared by the above-mentioned nitrogen source-loaded biomass-based microcapsules or preparation methods in promoting straw decomposition and / or crop growth.

[0021] The beneficial effects of the present invention are:

[0022] The present invention provides a biomass-based microcapsule loaded with a nitrogen source, comprising a biomass-based microcapsule and an organic nitrogen source encapsulated within the biomass-based microcapsule; the mass ratio of the organic nitrogen source to the biomass-based microcapsule is 30-35:3-7. The raw materials for the biomass-based microcapsules loaded with nitrogen sources are readily available and environmentally friendly. The hollow structure of the biomass-based microcapsules allows for efficient loading of the organic nitrogen source and slow release of the nitrogen source, thereby continuously providing nutrients to microorganisms that decompose straw and promoting nutrient recycling.

[0023] The present invention also provides a biomass-based microcapsule. Alkali lignin is used as a template, and sodium lignin sulfonate and chitosan with opposite charges are added sequentially. The sodium lignin sulfonate and chitosan are alternately deposited at the interface of an emulsion made from the alkali lignin, thereby forming the biomass-based microcapsule. The biomass-based microcapsules of the present invention form a rich hollow structure through the alternating deposition of raw materials layer by layer, which can effectively load an organic nitrogen source and achieve a long-term sustained release effect.

[0024] The present invention also provides a preparation method of the biomass-based microcapsules. The preparation method of the present invention has a simple process, mild conditions, and green and environmentally friendly raw materials. The hollow structure of the prepared biomass-based microcapsules can efficiently encapsulate nitrogen sources, reduce nitrogen loss caused by rainwater erosion and irrigation, and thus provide continuous and stable nitrogen nutrition for the composite bacterial system, thereby improving the decomposition efficiency of the composite bacterial system on crop straw and promoting the recycling of nutrients in agricultural waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0026] Figure 1 This is a morphology of the alkali lignin that was not repeatedly deposited in Example 1;

[0027] Figure 2 The morphology of the biomass-based microcapsules prepared in Example 1; from left to right are the morphology of multiple biomass-based microcapsules and the morphology of a single biomass-based microcapsule;

[0028] Figure 3 The experimental results of exploring the volume ratio of sodium lignin sulfonate solution to chitosan solution in Example 3 are shown; wherein, a is the precipitation result of the mixed solution after adding different volumes of chitosan solution to the sodium lignin sulfonate solution; b is the UV spectrum of the sample supernatant; c is the surface zeta potential of the sample supernatant;

[0029] Figure 4 The statistical results of straw decomposition rates of different groups in Example 4 of the present invention are as follows;

[0030] Figure 5 The statistical results of plant height of winter wheat in different groups in Example 4 of the present invention are as follows;

[0031] Figure 6 The SPAD value statistics of winter wheat in different groups in Example 4 of the present invention are as follows;

[0032] Figure 7 This is a schematic diagram of the growth effects of winter wheat in different groups on different days in Example 4 of the present invention;

[0033] Figure 8 The aboveground dry weight statistics of winter wheat in different groups in Example 4 of the present invention are shown. DETAILED DESCRIPTION

[0034] The present invention provides a biomass-based microcapsule loaded with a nitrogen source, comprising a biomass-based microcapsule and an organic nitrogen source wrapped inside the biomass-based microcapsule; the mass ratio of the organic nitrogen source to the biomass-based microcapsule is 30-35:3-7.

[0035] As an embodiment, in the biomass-based nitrogen source-loaded microcapsules of the present invention, the mass ratio of the organic nitrogen source to the biomass-based microcapsules is 30-35:3-7. As an optional embodiment, the mass ratio of the organic nitrogen source to the biomass-based microcapsules can be 30:3, 30:4, 30:5, 30:6, 30:7, 35:3, 35:4, 35:5, 35:6 or 35:7, or any intermediate value between the adjacent point values ​​mentioned above. As an embodiment, the organic nitrogen source includes products from microbial fermentation. In a specific embodiment, the organic nitrogen source of the present invention is purchased from Angel Yeast (Chifeng) Co., Ltd., item number: 6917790024205. The organic nitrogen source contains 23.22% carbon, 8.07% nitrogen, and a total nutrient content (N+P2O5+K2O≥10.0%), including polysaccharides (calculated as β-glucan + mannan) ≥1.5%, organic acids (calculated as malic acid + citric acid + succinic acid) ≥1.0%, fulvic acid ≥30%, Ca+Mg ≥1.0%, and water-insoluble matter ≤5%. The organic nitrogen source has a pH of 4.5-8.0. This nitrogen source is a fermentation metabolite of yeast cultured in molasses. Refined through concentration, drying, or non-drying processes, it is rich in amino acids, organic acids, fulvic acid, polysaccharides, and other substances, as well as major, medium, and trace elements. Yeast metabolites contain a large amount of biochemical fulvic acid, amino acids (primarily aspartic acid and glutamic acid), organic acids (primarily organic acids produced by yeast in the tricarboxylic acid cycle during aerobic respiration, such as malic acid, citric acid, and succinic acid), yeast cell wall polysaccharides, mannans, glucans, the natural stress-resistant component betaine, and yeast-derived γ-aminobutyric acid and ergosterol. Yeast metabolites are of microbial origin. In terms of composition, yeast metabolites contain humic biochemical fulvic acid, nitrogenous substances such as amino acids and betaine, chitosans such as yeast cell wall polysaccharides, and microbial extracts such as various organic acids produced during the tricarboxylic acid cycle, γ-aminobutyric acid, ergosterol, and vitamins. These rich ingredients are similar to those of seaweed extracts, providing ample nutrition for microbial growth and reproduction.

[0036] The present invention also provides a method for preparing the biomass-based nitrogen source-loaded microcapsules, comprising the following steps: dispersing an organic nitrogen source in deionized water, stirring for 10 to 20 minutes, and obtaining an organic nitrogen source solution; adding freeze-dried microcapsules (CH+SL)12@PE to the organic nitrogen source solution, and magnetically stirring for 20 to 40 minutes to finally form nitrogen source-loaded microcapsules.

[0037] As an embodiment, the mass volume ratio of the organic nitrogen source and deionized water is 150-180g:350-500mL. As an optional embodiment, the mass volume ratio of the organic nitrogen source and deionized water can be 150g:350mL, 160g:350mL, 170g:350mL, 180g:350mL, 150g:400mL, 160g:400mL, 170g:400mL, 180g:400mL, 150g:500mL, 160g:500mL, 170g:500mL or 180g:500mL, or any intermediate value between the above adjacent point values. As an embodiment, the stirring time can be 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20min, or any intermediate value between the above adjacent point values.

[0038] As an embodiment, the mass ratio of the organic nitrogen source in the organic nitrogen source solution to the freeze-dried microcapsules is 150-180:25-30. As an optional embodiment, the mass ratio of the organic nitrogen source in the organic nitrogen source solution to the freeze-dried microcapsules can be 150:25, 150:30, 160:25, 160:30, 170:25, 170:30, 180:25 or 180:30, or any intermediate value between the above adjacent point values. As an optional embodiment, the magnetic stirring time can be 20 min, 25 min, 30 min, 35 min or 40 min, or any intermediate value between the above adjacent point values.

[0039] As an embodiment, the raw materials of the biomass-based microcapsules include: an aqueous phase component, an oil phase component, sodium lignin sulfonate and chitosan; the aqueous phase component includes alkali lignin and water; the oil phase component includes an organic solvent and / or edible oil; the mass ratio of chitosan to sodium lignin sulfonate is 1 to 3:10; the mass ratio of alkali lignin to chitosan is 1 to 3:2 to 5.

[0040] In one embodiment, the mass-to-volume ratio of alkali lignin to water in the biomass-based microcapsules of the present invention is 0.5-2 g:100 mL; the water comprises deionized water. Alternatively, the volume ratio of lignin to water can be 0.5 g:100 mL, 1.0 g:100 mL, 1.5 g:100 mL, or 2.0 g:100 mL, or any intermediate value between these values. In one embodiment, the volume ratio of the aqueous phase component to the oil phase component is 4:1. In one embodiment, the chitosan and sodium lignin sulfonate can be replaced with other materials with opposite charges, such as heparin-protamine or chitosan-hyaluronic acid. In one embodiment, the mass ratio of chitosan to sodium lignin sulfonate can be 1:10, 2:10, or 3:10, or any intermediate value between these values. In one embodiment, the mass ratio of alkali lignin to chitosan can be 1:2, 1:3, or 2:5, or any intermediate value between these values. In one embodiment, the oil phase component includes an organic solvent or an edible oil. In one embodiment, the organic solvent includes any one or more of toluene, cyclohexane, n-hexane, and / or cyclohexanone. In one embodiment, the edible oil includes soybean oil, peanut oil, or a vegetable blend oil. In a preferred embodiment, the oil phase component is an organic solvent, and the organic solvent is cyclohexane.

[0041] The present invention also provides a method for preparing the above-mentioned biomass-based microcapsules loaded with nitrogen sources, comprising the following steps:

[0042] The method comprises adjusting the pH of an aqueous phase component to 2-3 to obtain an alkali lignin particle dispersion; mixing the alkali lignin particle dispersion with an oil phase component and homogenizing to obtain an alkali lignin-based Pickering emulsion; dissolving chitosan and sodium lignin sulfonate to obtain a chitosan solution and a sodium lignin sulfonate solution; mixing the alkali lignin-based Pickering emulsion, the chitosan solution and the sodium lignin sulfonate, and then freeze-drying to obtain biomass-based microcapsules; and mixing the biomass-based microcapsules with an organic nitrogen source in proportion to obtain biomass-based microcapsules loaded with a nitrogen source.

[0043] As an optional embodiment, the pH of the aqueous phase component of the present invention can be adjusted to 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3, or any intermediate value between the adjacent values ​​mentioned above. As an embodiment, the volume ratio of the alkali lignin particle dispersion to the oil phase component is 4:1.

[0044] In one embodiment, the chitosan is dissolved in an acetic acid solution to obtain a chitosan solution. In one embodiment, the mass-to-volume ratio of the chitosan to the acetic acid solution is 1:1000 to 2:1000. In an alternative embodiment, the mass-to-volume ratio of the chitosan to the acetic acid solution can be 1:1000 or 2:1000, or any intermediate value between the aforementioned adjacent values. In one embodiment, the volume concentration of the acetic acid solution is 1-2%. In an alternative embodiment, the volume concentration of the acetic acid solution can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, or any intermediate value between the aforementioned adjacent values. In one embodiment, the mass concentration of chitosan in the chitosan solution is 0.1-0.3%. In an alternative embodiment, the mass concentration of chitosan in the chitosan solution can be 0.1%, 0.2%, or 0.3%, or any intermediate value between the aforementioned adjacent values.

[0045] In one embodiment, the sodium lignin sulfonate is dissolved in water to obtain a sodium lignin sulfonate solution. In one embodiment, the mass-to-volume ratio of the sodium lignin sulfonate to water is 1-3:80-150. In an alternative embodiment, the mass-to-volume ratio of the sodium lignin sulfonate to water can be 1:80, 2:80, 3:80, 1:100, 8:100, 3:100, 1:150, 2:150, or 3:150, or any intermediate value between the aforementioned adjacent values. In one embodiment, the water is deionized water. In one embodiment, the mass concentration of sodium lignin sulfonate in the sodium lignin sulfonate solution is 1-2%. In an alternative embodiment, the mass concentration of sodium lignin sulfonate in the sodium lignin sulfonate solution can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, or any intermediate value between the aforementioned adjacent values.

[0046] In one embodiment, the method of mixing the alkali lignin-based Pickering emulsion, chitosan solution, and sodium lignin sulfonate includes: alternately adding the chitosan solution and sodium lignin sulfonate to the alkali lignin-based Pickering emulsion; the number of alternating additions is 1 to 15 times. In one embodiment, adding the chitosan solution to the alkali lignin-based Pickering emulsion once and adding the sodium lignin sulfonate solution to the alkali lignin-based Pickering emulsion once counts as one alternating addition; in an alternative embodiment, the number of alternating additions can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 times. In a preferred embodiment, the number of alternating additions is 12 times. In one embodiment, the volume ratio of the chitosan solution to the sodium lignin sulfonate solution is 1.5 to 5:1. As an optional embodiment, as an embodiment, the volume ratio of the chitosan solution to the sodium lignin sulfonate solution can be 1.5:1, 2:1, 3:1 or 5:1, or any intermediate value between the adjacent point values ​​mentioned above. As an embodiment, the freeze-drying step is: placing the mixed alkali lignin-based Pickering emulsion, chitosan solution and sodium lignin sulfonate in a freeze dryer for freeze drying.

[0047] As an embodiment, the mixing ratio of the biomass-based microcapsules and the organic nitrogen source is as described above and will not be repeated here.

[0048] The present invention also provides a composition comprising biomass-based microcapsules loaded with nitrogen sources and microorganisms.

[0049] In one embodiment, the microorganisms include Bacillus subtilis and Bacillus cereus. In one embodiment, the Bacillus subtilis has a deposit number of ACCC62095, which is disclosed in Patent 202510298377.8. In one embodiment, the Bacillus cereus has a deposit number of ACCC62096, which is disclosed in Patent 202510298015.9.

[0050] The composition of the present invention can produce slow-release nitrogen fertilizer in the field and improve the decomposition efficiency of microbial agents in the field.

[0051] The present invention also provides the use of the nitrogen source-loaded biomass-based microcapsules or the nitrogen source-loaded biomass-based microcapsules or compositions prepared by the above-mentioned nitrogen source-loaded biomass-based microcapsules or preparation methods in promoting straw decomposition and / or crop growth.

[0052] To further illustrate the present invention, the following describes in detail a biomass-based microcapsule loaded with a nitrogen source and its preparation method and application provided by the present invention in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1 Preparation method of biomass-based microcapsules loaded with nitrogen source

[0054] The steps of the preparation method are as follows:

[0055] (1) Preparation of alkali lignin-based Pickering emulsion (PE emulsion): Weigh 1 g of alkali lignin and dissolve it in 100 mL of deionized water. After fully dissolving, filter to remove insoluble matter, and then adjust the pH of the solution to 2.5 with hydrochloric acid to obtain an alkali lignin particle dispersion with a concentration of 1 wt%. The alkali lignin particle dispersion was used as the aqueous phase and cyclohexane as the organic phase. The aqueous phase and the organic phase were mixed in a volume ratio of 4:1, and then homogenized with a homogenizer at a speed of 7000 rpm for 3 minutes to obtain an alkali lignin-based Pickering emulsion, named PE emulsion. The PE emulsion was freeze-dried. The morphology after freeze-drying is shown in the figure below. Figure 1 shown.

[0056] (2) Preparation of chitosan solution (CH solution): 0.1 g of chitosan was dissolved in 1% by volume acetic acid solution, stirred for 24 h, and then the insoluble matter was filtered to prepare a CH solution with a final concentration of 0.1 wt%.

[0057] (3) Preparation of sodium lignin sulfonate solution (SL solution): 1 g of sodium lignin sulfonate was dissolved in deionized water, and the precipitate was removed by filtration to prepare an SL solution with a final concentration of 1 wt%.

[0058] (4) Place 1 mL of PE emulsion on a magnetic stirrer at a speed of 500 rpm, and add CH solution and SL solution to the PE emulsion in turn. The amount of CH solution added is 2 mL / time, and the amount of SL solution added is 1 mL / time. Stir for 2 minutes to allow chitosan and sodium lignin sulfonate to be deposited layer by layer on the interface of the Pickering emulsion droplets to form microcapsules (CH+SL)1@PE. Repeat the step of "adding CH solution and SL solution to the PE emulsion in turn" 11 times on the basis of (CH+SL)1@PE. Stir for 2 minutes after each cycle. After every 3 cycles, let it stand for 3 minutes to allow the microcapsules to fully float and remove the supernatant. Continue the cycle until a multilayer film containing 12 layers of chitosan and 12 layers of sodium lignin sulfonate is prepared. Place it in a freeze dryer and freeze-dry it. It is named (CH+SL)12@PE, that is, biomass-based microcapsules. The morphology of the freeze-dried biomass-based microcapsules is as follows: Figure 2As shown, it can be seen that the size of the microcapsules after repeated deposition is 10 to 15 μm, the microcapsules can maintain a complete spherical shape, which improves the mechanical strength of the microcapsules and can effectively prevent the loss of nitrogen source.

[0059] (5) 160 g of an organic nitrogen source (a yeast fermentation metabolite obtained from molasses culture produced by Angel Yeast (Chifeng) Co., Ltd., product number: 6917790024205) was dispersed in 400 mL of deionized water. After stirring for 15 min, 25 g of biomass-based microcapsules were added and magnetic stirring was continued for 30 min to obtain microcapsules loaded with nitrogen source.

[0060] Example 2 Exploration experiment of the optimal volume ratio of CH solution and SL solution

[0061] 1 wt% SL solution and 0.1 wt% CH solution were prepared according to the preparation method described in (2) and (3) of Example 1. SL solution and CH solution were mixed according to the volume ratio of SL solution to CH solution of 1:0.1, 1:0.5, 1:1, 1:1.5, 1:2, 1:3 and 1:5, respectively, to obtain mixed solutions. The mixed solutions were allowed to stand and the precipitation in the mixed solutions of different groups was observed. The results are as follows. Figure 3 As shown in a. The mixed solutions of different groups were centrifuged and the supernatant was separated. The SL solution has an ultraviolet absorption peak at 280nm. Therefore, the residual SL in the supernatant under different ratio conditions can be analyzed by ultraviolet spectroscopy. The results are shown in Figure 3 As shown in b. The surface potential of the supernatant was detected, and the results were as follows Figure 3 As shown in c.

[0062] Depend on Figure 3 It can be seen that when the volume ratio of SL solution to CH solution is 1:2, the flocculent sedimentation is fastest and the supernatant is the clearest ( Figure 3 In a), the absorption peak intensity at 280 nm is reduced to the lowest ( Figure 3 b). The absolute value of the zeta potential of the mixed solution is the smallest ( Figure 3 Figure c) indicates that CH and SL reacted fully under this ratio. As the CH ratio increased, the supernatant became increasingly turbid and the amount of unreacted SL increased.

[0063] Example 3 Study on the straw decomposition effect of biomass-based microcapsules loaded with nitrogen source

[0064] 1. The soil information used in this example is as follows: collected from Fangcheng County, Nanyang City, Henan Province (33°0′16″N, 112°53′14″E), the soil type is sandy ginger black soil, winter wheat-summer corn rotation system, pH 5.80, organic matter 50.05 g / kg, total nitrogen 2.21 g / kg, available phosphorus 90.92 mg / kg, and available potassium 298.00 mg / kg.

[0065] 2. Experimental Materials

[0066] (1) Corn straw: Cut corn straw dried to constant weight into 2 cm segments, take 12 g of corn straw and put it into a 250 mesh nylon mesh bag (15 cm × 10 cm) for later use;

[0067] (2) Biomass-based microcapsules loaded with nitrogen source prepared in Example 1;

[0068] (3) Microorganisms: Bacillus subtilis and Bacillus cereus. The deposit number of Bacillus subtilis is ACCC62095, which is disclosed in Patent 202510298377.8; the deposit number of Bacillus cereus is ACCC62096, which is disclosed in Patent 202510298015.9.

[0069] 3. Preparation method of composite bacterial strain: Use 75% alcohol cotton to disinfect the surface of the vial containing Bacillus subtilis and Bacillus cereus respectively, open the vial under sterile conditions, add 0.3mL of the matching LB liquid medium to the freeze-dried quality control bacteria, hydrate the freeze-dried powder, dissolve the freeze-dried quality control bacteria into a uniform suspension, use a pipette to draw an appropriate amount of freeze-dried powder to hydrate the suspension, transfer it to the LB slant medium, culture at a constant temperature of 28°C overnight, and observe the growth of the strain. Gently scrape a small amount of bacterial moss and inoculate it into LB liquid medium, culture it at a constant temperature of 28°C and 150r / min to the logarithmic phase, measure the OD value on the spectrophotometer (600nm), adjust it to zero with physiological saline as the blank control, measure the absorbance of the 20-fold diluted bacterial solution, if the OD value is in the range of 0.3-0.7, then according to 1OD=1.0×10 9 The original bacterial solution concentration was calculated by cfu / mL. The final bacterial solution concentrations of Bacillus subtilis and Bacillus cereus were both 1.0×10 9 cfu / mL, Bacillus subtilis and Bacillus cereus were mixed in a volume ratio of 1:1 to obtain a composite bacterial system.

[0070] 4. This example provides four treatments: corn straw, corn straw + composite bacterial system, corn straw + composite bacterial system + nitrogen source, and corn straw + composite bacterial system + nitrogen source-loaded microcapsules. Each treatment group contains five nylon mesh bags of corn straw. The specific treatment methods are as follows:

[0071] Straw group: 12 g of corn straw in a nylon mesh bag was directly buried in the pot;

[0072] Straw + composite bacteria group: corn straw composite bacteria were mixed at a mass volume ratio of 12 g: 6 mL and then buried in the pot;

[0073] Straw + composite bacteria system + nitrogen source: corn straw and composite bacteria system were mixed at a mass volume ratio of 12 g:6 mL, and 4.66 g of the organic nitrogen source described in Example 1 was added. After mixing, the mixture was filled into a pot.

[0074] Straw + composite bacteria system + nitrogen source-loaded microcapsules: Mix corn straw and composite bacteria system in a volume ratio of 16.36g:6mL, then add nitrogen source-loaded microcapsules in a mass volume ratio of nitrogen source: composite bacteria system of 4.66g:6mL, mix and fill into the pot.

[0075] The operations for filling the pots for each treatment group were as follows: nylon mesh bags with different treatments were placed in pots with 5.5 kg of soil for filling treatment, the surface of the nylon mesh bags was covered with 3 cm of soil, and the plants were cultured in the dark at 25°C. Water was added in time to maintain the soil moisture content at 60% of the field water holding capacity.

[0076] 5. Samples were taken from each treatment group on the 0th, 3rd, 7th, 14th, and 28th day after the nylon mesh bags were filled. After washing away the soluble matter, the samples were dried at 80°C to constant weight. The decomposition rate of the straw was calculated. The results are shown in Table 1. The residual straw rate was calculated based on the decomposition rate of the straw. The results are shown in Table 1. Figure 4 shown.

[0077] The formula for straw decomposition rate is as follows:

[0078] Straw decomposition rate (%) = (W1-W2) / W1;

[0079] Where: W1 is the original straw weight (g); W2 is the remaining straw weight in the net bag (g).

[0080] The calculation formula for straw residue rate is as follows:

[0081] Straw residue rate (%) = 1-straw decomposition rate (%).

[0082] Table 1 Decomposition rate of straw in different groups (%)

[0083] Day 0 Day 3 Day 7 Day 14 Day 28 straw 100.00 77.58 68.27 63.12 56.36 Straw + composite bacteria system 100.00 72.07 67.98 61.43 56.28 Straw + composite bacteria system + nitrogen source 100.00 64.42 60.07 57.87 46.06 Straw + composite bacteria system + nitrogen source loaded microcapsules 100.00 80.79 63.83 59.66 39.13

[0084] From Table 1 and Figure 4As can be seen, the residual straw mass rate in each treatment decreased with increasing straw decomposition time. All three treatments—straw, composite bacterial system, and composite bacterial system + nitrogen source—showed rapid decomposition in the early stages, followed by a gradual slowdown in the later stages. The addition of a nitrogen source, in particular, significantly accelerated straw decomposition because it optimized the carbon-nitrogen ratio of the straw, providing sufficient nitrogen for microorganisms and thus enhancing their activity and reproduction. The microcapsule treatment loaded with a composite nitrogen source experienced slower decomposition in the early stages, likely due to the nitrogen source being trapped within the biomass-based capsules and unable to be rapidly released. As decomposition time increased, the nitrogen source in the microcapsules was gradually released, significantly boosting microbial activity. In contrast, the nitrogen source in the other treatments was gradually lost due to water erosion. Consequently, the microcapsule treatment loaded with a composite nitrogen source exhibited a higher straw decomposition rate than the other treatments, reaching 39.13% after 28 days. Higher straw decomposition efficiency significantly improves soil nutrients and fertility.

[0085] Example 4 Study on the Growth-Promoting Effect of Biomass-Based Microcapsules Loaded with Nitrogen Source

[0086] In this embodiment, a potted plant experiment was conducted using round pots with a diameter of 20 cm and a depth of 28 cm. A total of 12 round pots were evenly divided into 4 groups. Different groups were treated as shown in Table 2.

[0087] Table 2 Treatments of potted plant experiments

[0088]

[0089]

[0090] Note: In Table 2, / indicates that the component is not added; the concentrations of the Bacillus subtilis and Bacillus cereus bacterial solutions are 1.0×10 9 cfu / mL, that is, in the composite bacterial system, the concentrations of Bacillus subtilis and Bacillus cereus are each 4.5×10 8 cfu / mL; in the straw+composite bacteria system+microcapsule described in Example 1 group, the amount of the microcapsule described in Example 1 was 6.35 g based on the organic nitrogen source.

[0091] The steps for each process are as follows:

[0092] Straw + composite bacterial system + nitrogen source-loaded microcapsules group: Dried corn straw was mixed with a microbial solution at a ratio of 16.36 g:6 mL to produce a first mixture. The concentrations of the microbial solution are shown in Table 3. 6.35 g of an organic nitrogen source was loaded into microcapsules according to the method described in Example 1. The nitrogen source-loaded microcapsules were then added to the first mixture and mixed to produce a second mixture. The second mixture was mixed with soil, placed in a round basin, and adjusted to 60% of field capacity for later use.

[0093] Straw + composite bacterial system + nitrogen source group: Dry corn straw was mixed with a microbial solution at a ratio of 16.36 g: 6 mL to obtain a first mixture. The concentrations of the microbial solution are shown in Table 3. 6.35 g of an organic nitrogen source was added to the first mixture and mixed to obtain a second mixture. The second mixture was mixed with soil and placed in a round basin. The volume was adjusted to 60% of the field capacity and set aside.

[0094] Straw + composite bacterial system group: Dry corn straw was mixed with microbial solution at a ratio of 16.36 g:6 mL to obtain a first mixture. The concentration of the microbial solution is shown in Table 3. The first mixture was placed in a round basin and adjusted to 60% of the field capacity for later use.

[0095] Straw group: 16.36 g of dried corn straw was mixed with soil and placed in a round basin. The mixture was adjusted to 60% of the field water holding capacity and set aside.

[0096] The soil in each of the 12 round pots weighs 1.5 kg on a dry basis, and the amount of straw used is 16.36 g / pot, equivalent to 8,000 kg / hm2 of soil returned to the field. 2 Corn stalks.

[0097] After preparing the round pots as described above, winter wheat was sown in the round pots of different groups, with 15 seeds sown in each pot. The plant height of winter wheat in different groups was measured on the 16th and 22nd day after sowing. The results are as follows: Figure 5 The photosynthetic rate of winter wheat was measured on the 22nd day after sowing, and the results are shown in Table 4.

[0098] Table 3 Plant height of winter wheat after transplanting (cm)

[0099]

[0100]

[0101] Table 4 Photosynthetic efficiency of winter wheat leaves under different treatments 22 days after transplanting

[0102]

[0103] The decomposition of straw releases a large amount of organic matter, which in turn increases the content of nutrients such as nitrogen, phosphorus, and potassium in the soil. It also reduces soil bulk density and increases soil porosity, thereby improving soil aeration and water permeability. Therefore, microcapsules loaded with complex nitrogen sources have great potential for promoting straw decomposition and growth. As shown in Table 4, 22 days after sowing, the net photosynthetic rate of winter wheat treated with microcapsules loaded with complex nitrogen sources was the highest, increasing by 148.82% compared to the microbial system + nitrogen source treatment. This indicates that these treated plants were able to more efficiently utilize light energy, carbon dioxide, and water to synthesize more organic matter, providing an adequate material foundation for growth and development. Figure 5 It was also confirmed that the plant height of the plants treated with the microcapsules had obvious advantages 16 days and 22 days after sowing.

[0104] The chlorophyll content (SPAD value) of leaves was measured on the 13th, 16th, 22nd, 31st and 43rd day after sowing the winter wheat. The results are shown in Table 5 and Figure 6 As shown, photos of different groups of winter wheat were taken on the 9th, 16th, 22nd and 48th days after sowing. Two pots were randomly displayed in each treatment group. The results are shown in Figure 7 The plant height of winter wheat was measured on the 16th and 22nd day after sowing. Destructive sampling was performed on the 48th day after sowing to measure the aboveground dry matter weight of each pot of winter wheat under each treatment. The results are shown in the figure. Figure 8 and shown in Table 6.

[0105] Table 5 SPAD values ​​in different groups of winter wheat

[0106]

[0107] Table 6 Dry matter weight of aboveground part of winter wheat in different groups 45 days after sowing

[0108]

[0109]

[0110] Depend on Figure 6 As shown in Table 5, the SPAD values ​​of winter wheat in each treatment gradually decreased over time. The group containing the composite bacteria system and nitrogen source can effectively delay the decomposition of leaf chlorophyll and maintain the SPAD value at a higher level. Among them, the SPAD value of the plant leaves treated with microcapsules loaded with composite nitrogen source was 32.67 43 days after sowing, which was 52% higher than that of the straw group and 8% higher than that of the composite bacteria system + nitrogen source treatment. The higher the SPAD value, the higher the chlorophyll content in the leaves, the stronger the photosynthesis capacity, and the richer the dry matter accumulation. Figure 8As shown in Table 6, 48 days after sowing, the microcapsule-treated plants showed the best growth and the highest dry matter weight, reaching 154 mg / plant, a 118% increase compared to the CK treatment, demonstrating a significant growth-promoting effect. The winter wheat treated with the straw + composite bacterial system + nitrogen-source-loaded microcapsules group had significantly higher aboveground dry matter weight than the other groups. The nitrogen-source-loaded microcapsules prepared by the present invention, when combined with the composite bacterial system to promote straw composting, can improve the growth efficiency of subsequent crops.

[0111] In summary, the biomass-based microcapsules provided by the present invention can effectively load nitrogen sources and slowly release them. When used together with microbial strains for straw return to the field, they can promote the activity of the microbial strains, increase the efficiency of straw composting, and enhance the growth and development of subsequent crops. This present invention provides a highly efficient technical solution for straw return to the field.

[0112] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments like this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A biomass-based microcapsule loaded with a nitrogen source, characterized in that: It comprises a biomass-based microcapsule and an organic nitrogen source encapsulated inside the biomass-based microcapsule; The mass ratio of the organic nitrogen source to the biomass-based microcapsules is 30-35:3-7.

2. The biomass-based microcapsule loaded with nitrogen source according to claim 1, characterized in that The raw materials of the biomass-based microcapsules include: water phase component, oil phase component, sodium lignin sulfonate and chitosan; The aqueous phase components include alkali lignin and water; The oil phase components include organic solvents and / or edible oils; The mass ratio of chitosan to sodium lignin sulfonate is 1 to 3:10; The mass ratio of the alkali lignin to chitosan is 1-3:2-5.

3. The biomass-based microcapsule loaded with nitrogen source according to claim 2, characterized in that: The mass volume ratio of the alkali lignin and water is 0.5-2 g:100 mL; the water includes deionized water; The organic solvent includes any one or more of toluene, cyclohexane, n-hexane and / or cyclohexanone; the edible oil includes soybean oil, peanut oil or vegetable blend oil; The volume ratio of the water phase component to the oil phase component is 4:

1.

4. The method for preparing the biomass-based microcapsules loaded with nitrogen sources according to any one of claims 1 to 3, characterized in that: The steps include: Adjusting the pH of the aqueous phase component to 2-3 to obtain an alkali lignin particle dispersion; Mixing the alkali lignin particle dispersion with the oil phase component and homogenizing to obtain an alkali lignin-based Pickering emulsion; dissolving chitosan and sodium lignin sulfonate to obtain a chitosan solution and a sodium lignin sulfonate solution; The alkali lignin-based Pickering emulsion, chitosan solution and sodium lignin sulfonate are mixed and freeze-dried to obtain biomass-based microcapsules; The biomass-based microcapsules and the organic nitrogen source are mixed in proportion to obtain biomass-based microcapsules loaded with the nitrogen source.

5. The preparation method according to claim 4, wherein The chitosan is dissolved in acetic acid solution to obtain a chitosan solution; the volume concentration of the acetic acid solution is 1% to 2%; the mass concentration of the chitosan in the chitosan solution is 0.1% to 0.3%.

6. The preparation method according to claim 4, wherein The sodium lignin sulfonate is dissolved in water to obtain a sodium lignin sulfonate solution; the water is deionized water; and the mass concentration of the sodium lignin sulfonate in the sodium lignin sulfonate solution is 1% to 2%.

7. The preparation method according to claim 4, wherein The method of mixing the alkali lignin-based Pickering emulsion, chitosan solution and sodium lignin sulfonate comprises: alternately adding chitosan solution and sodium lignin sulfonate to the alkali lignin-based Pickering emulsion in sequence; the number of alternate additions is 1 to 15 times.

8. A composition, characterized in that including biomass-based microcapsules and microorganisms loaded with nitrogen sources; The nitrogen source-loaded biomass-based microcapsules are the nitrogen source-loaded biomass-based microcapsules according to any one of claims 1 to 3 or the nitrogen source-loaded biomass-based microcapsules prepared by the preparation method according to any one of claims 4 to 7.

9. The composition according to claim 8, wherein The microorganisms include Bacillus subtilis and Bacillus cereus; The deposit number of the Bacillus subtilis is: ACCC62095; The deposit number of the Bacillus cereus is ACCC62096.

10. Use of the nitrogen source-loaded biomass-based microcapsules according to claims 1 to 3, or the nitrogen source-loaded biomass-based microcapsules prepared by the preparation method according to any one of claims 4 to 7, or the composition according to claim 8 or 9 in promoting straw decomposition and / or crop growth.

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