Lactic acid bacteria complex microbial inoculant, preparation method thereof and application of lactic acid bacteria complex microbial inoculant in improvement of saline-alkali soil and promotion of crop growth

Abstract

The invention relates to a lactic acid bacteria complex microbial inoculant, a preparation method of the lactic acid bacteria complex microbial inoculant and application of the lactic acid bacteria complex microbial inoculant in improvement of saline alkali soil and promotion of growth of crops. The lactic acid bacteria complex microbial inoculant comprises lactobacillus rhamnosus 7M1, lactobacillus futsai 7M7 and lactobacillus coryniform LSC-7. The lactic acid bacteria complex microbial inoculant is prepared from lactobacillus rhamnosus 7M1, lactobacillus futsai 7M7 and lactobacillus coryniform LSC-7. After the lactic acid bacteria complex microbial inoculant is applied to saline-alkali soil, the effects of improving soil, improving the yield and quality of crops and improving the disease resistance of agricultural products can be achieved, and the lactic acid bacteria complex microbial inoculant is suitable for production of green pollution-free agricultural products in modern agricultural production, low in cost and simple to operate; the method has the advantages of good remediation effect, environmental friendliness and no influence on agricultural production.

Description

Technical Field

[0001] The present invention relates to the field of microbial technology, and in particular to a lactic acid bacteria composite agent, a preparation method thereof, and applications thereof in improving saline-alkali soil and promoting the growth of crops. Background Art

[0002] Saline-alkali land has the characteristics of high salt content or high alkalinity, which leads to poor soil structure, easy compaction, low organic matter content, poor nutrients, and weak fertilizer retention capacity, making it unsuitable for crop planting. After improvement, some saline-alkali land with agricultural utilization prospects can effectively improve its fertility and provide favorable growth conditions for crops. Therefore, the development and utilization of saline-alkali land has become the main way to make up for the reduction of cultivated land area.

[0003] The fundamental purpose of saline-alkali soil improvement is to improve the physical and chemical properties of the soil and provide a good growth and development environment for crops. Traditional saline-alkali soil improvement methods include drainage and salt washing, foreign soil improvement, and application of organic fertilizers. The drainage and salt washing measures mainly reduce the salt content by digging drainage ditches and lowering the groundwater level. This method requires a lot of manpower and material resources, and the effect is not lasting. The foreign soil improvement measure is to transport soil from non-saline-alkali land to saline-alkali land and cover it on saline-alkali soil to reduce the soil salt content. Although this method can quickly reduce soil salinity, it requires a large amount of foreign soil source and is prone to soil pollution and damage to the ecological environment. The application of organic fertilizer measures mainly increases the content of soil organic matter, improves soil fertility and water retention capacity, and thus reduces soil salinity by applying organic fertilizers. This method requires long-term persistence and is highly dependent on fertilizers.

[0004] Therefore, it is necessary to propose new measures to overcome the above-mentioned defects. Summary of the invention

[0005] The purpose of the present invention is to provide a lactic acid bacteria composite agent and a preparation method thereof and its application in improving saline-alkali soil and promoting crop growth, so as to solve the problems of high investment, short-lasting effect and easy destruction of ecology in the existing methods.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] Provided is a lactic acid bacteria composite bacterial agent, the lactic acid bacteria composite bacterial agent comprising Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7;

[0008] The Lacticaseibacillus rhamnosus 7M1 is deposited in the General Microbiology Center of China National Committee for the Preservation of Microorganisms, with a deposit date of December 2, 2024 and a deposit number of CGMCCN0.32861.

[0009] The Lactobacillus futsaii 7M7 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with a deposit date of December 2, 2024 and a deposit number of CGMCC No. 32862.

[0010] The Lactobacillus coryniformis LSC-7 is deposited in the General Microbiology Center of the China Culture Collection Administration, with a deposit date of December 2, 2024 and a deposit number of CGMCCN0.32863.

[0011] On the other hand, a method for preparing the lactic acid bacteria composite agent as described above is provided, the method comprising:

[0012] Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7 were activated respectively to obtain three initial bacterial solutions;

[0013] The three initial bacterial liquids are mixed with the liquid seed fermentation medium A, and allowed to ferment statically to obtain a liquid fermentation seed liquid;

[0014] The liquid fermentation seed liquid is mixed with the liquid fermentation medium B, and allowed to ferment statically to obtain a lactic acid bacteria composite bacterial agent.

[0015] Further, Lacticaseibacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7 are activated respectively, including:

[0016] The bacteria in the -80℃ cryotubes were streaked on MRS solid plates for activation and cultured at 37℃ for 24-48 hours;

[0017] Select a single colony, inoculate it into MRS liquid medium, and culture it at 37°C for 24-48 hours;

[0018] Take 1% of the bacterial solution and transfer it to MRS liquid medium, and culture it at 37℃ for 12-24 hours;

[0019] The lactic acid bacteria content is not less than 1×10 9 CFU / mL, the strain activation is complete.

[0020] Further, the formula of MRS liquid culture medium is:

[0021] Peptone 10.0g, beef extract 10.0g, yeast extract 5.0g, glucose 20.0g, sodium acetate 5.0g, diammonium citrate 2.0g, Tween-80 1.0g, dipotassium hydrogen phosphate 0.4g, magnesium sulfate 0.58g, manganese sulfate 0.29g, calcium carbonate 20.0g, add distilled water and make up to 1000mL, sterilize at 121℃ for 30min.

[0022] Further, the three initial bacterial liquids are mixed with the liquid seed fermentation medium A, and allowed to ferment statically to obtain a liquid fermentation seed liquid, including:

[0023] The three initial bacterial liquids were mixed with liquid seed fermentation medium A at a ratio of 2%-3%, and allowed to ferment at 37° C. for 48 hours to obtain liquid fermentation seed liquid.

[0024] Furthermore, the liquid seed fermentation medium A is obtained by adding 0.5%-1% of sterile sand mustard extract to the MRS liquid medium.

[0025] Further, the liquid fermentation seed liquid is mixed with the liquid fermentation medium B, and allowed to stand for fermentation to obtain a lactic acid bacteria composite agent, including:

[0026] Mix the liquid fermentation seed liquid with the liquid fermentation medium B at a ratio of 10%, and ferment at a temperature between 20 and 40° C. for 72 to 120 hours;

[0027] The lactic acid bacteria content is not less than 1×10 10 CFU / mL, the fermentation is completed and the lactic acid bacteria composite agent is obtained.

[0028] Further, the formula of liquid fermentation medium B is:

[0029] Peptone 1%, beef extract 1%, yeast extract 0.5%, glucose 2%, the balance is water, sterilize at 121℃ for 30min.

[0030] On the other hand, the invention provides the use of the lactic acid bacteria composite agent in improving saline-alkali soil.

[0031] On the other hand, the invention provides the use of the lactic acid bacteria composite agent in promoting the growth of crops.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a lactic acid bacteria composite agent and a preparation method thereof, and applications thereof in improving saline-alkali soil and promoting the growth of crops. When the lactic acid bacteria composite agent is applied to saline-alkali soil, the effects of improving the soil, increasing the yield and quality of crops, and increasing the disease resistance of agricultural products can be achieved. The lactic acid bacteria composite agent is suitable for the production of green and pollution-free agricultural products in modern agricultural production, has low cost and is simple to operate, and has the advantages of good repair effect, environmental friendliness, and no impact on agricultural production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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 or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying creative work.

[0035] Figure 1 This is a comparison chart of the effects of salt concentration and pH on the growth of Lactobacillus rhamnosus 7M1, Lactobacillus forsythiae 7M7, Lactobacillus coryneformis LSC-7 and the lactic acid bacteria compound agent MIX. In the figure, (a) shows the effect of different concentrations of NaCl on the growth of lactic acid bacteria, and (b) shows the effect of different pH on the growth of lactic acid bacteria under 3% NaCl conditions.

[0036] Figure 2 This is a comparison chart of the promoting effects of Lactobacillus rhamnosus 7M1, Lactobacillus formosanus 7M7, Lactobacillus coryneformis LSC-7 and the lactic acid bacteria compound agent MIX on plant roots.

[0037] Figure 3 This is a comparison chart of the antibacterial test of Lactobacillus rhamnosus 7M1, Lactobacillus formosanus 7M7, Lactobacillus coryneformis LSC-7 and lactic acid bacteria compound agent MIX on the test bacteria.

[0038] Figure 4 This is a comparison chart of the phosphate-solubilizing effects of Lactobacillus rhamnosus 7M1, Lactobacillus formosanus 7M7, Lactobacillus coryneformis LSC-7 and the lactic acid bacteria compound agent MIX.

[0039] Figure 5 This is a comparison chart of the potassium-dissolving effects of Lactobacillus rhamnosus 7M1, Lactobacillus formosanus 7M7, Lactobacillus coryneformis LSC-7 and the lactic acid bacteria complex agent MIX.

[0040] Figure 6 This is a comparison chart of the effects of using lactic acid bacteria compound agents on greenhouse vegetables (after picking).

[0041] Figure 7 This is a comparison chart of the effects of using lactic acid bacteria compound agents on greenhouse vegetables (under cultivation). DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0043] In the description of the present invention, it is to be understood that all the techniques and scientific terms used have the same meanings as those generally understood by those of ordinary skill in the art to which the present invention belongs. When there is a contradiction, the definition in this specification shall prevail. If not otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, the reagents used in the embodiments are commercially available products, and the devices used in the embodiments are existing devices, and the limitation of means, reagents or devices cannot be understood as limitation of the present invention, and the means, reagents or devices for solving the same technical problems of the same type are within the protection scope of the present invention.

[0044] In the description of the present invention, it is to be understood that when an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range limited by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. When a numerical range is described in this specification, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0045] In the description of the present invention, it should be understood that multiple steps are involved in the process of describing the method, which should not be understood as a limitation on the order of the method steps. When solving the same technical problem, the technical solution obtained by only changing the order of the steps is also within the scope of protection of the present invention.

[0046] The invention provides a lactic acid bacteria composite agent, which can be used to improve saline-alkali soil and promote crop growth, increase agricultural product yield, and enhance agricultural product disease resistance, and is suitable for the production of green and pollution-free agricultural products in modern agricultural production.

[0047] Specifically, the lactic acid bacteria composite agent includes Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7.

[0048] in:

[0049] The Lacticaseibacillus rhamnosus 7M1 was deposited in the General Microbiology Center of the China National Committee for the Preservation of Microbiological Cultures on December 2, 2024, with a deposit number of CGMCCN0.32861. The Lacticaseibacillus rhamnosus 7M1 was isolated and screened from pickled mustard greens.

[0050] The Lactobacillus futsaii 7M7 is deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration Committee on December 2, 2024, and the deposit number is: CGMCC No. 32862. The Lactobacillus futsaii 7M7 is isolated and screened from sand mustard pickled kimchi.

[0051] The LSC-7 was deposited in the General Microbiology Center of China National Committee for the Preservation of Microbiological Cultures on December 2, 2024, with a deposit number of CGMCCN0.32863. The LSC-7 was isolated and screened from fresh pakchoi.

[0052] The above three strains are all lactic acid bacteria. Lactic acid bacteria is a general term for bacteria that use carbohydrates as substrates, produce high amounts of organic acids such as lactic acid and phenyllactic acid, and secrete plant pathogen growth inhibitors such as bacteriocins. They are safe and edible and are currently the safest agricultural microbial strains. Plant-derived lactobacilli were previously considered to be an important probiotic group in fermented foods. It is currently found that this type of microorganism promotes biodegradation, promotes the conversion of nutrients such as phosphorus and potassium, regulates pH, produces organic acids and bacteriocin metabolites, stimulates the growth of branches and roots, and also has an antagonistic effect on plant pathogens, inhibiting pathogenic fungi and bacterial populations in the rhizosphere and phyllosphere. In the development of sustainable agriculture, maintaining soil health, promoting organic agriculture, and promoting plant health, the development of this type of microorganism can ensure human safety and health at the same time, so it has the advantages of low processing cost, simple construction, no secondary pollution, and little impact on the environment.

[0053] A lactic acid bacteria composite agent can be prepared based on the above three lactic acid bacteria, and the specific preparation method includes the following steps:

[0054] S1: Bacteria activation:

[0055] Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7 were activated respectively to obtain three initial bacterial solutions.

[0056] Each initial bacterial solution can be obtained through the following process:

[0057] S101: Streak the bacteria in the -80°C cryotube on an MRS solid plate and culture at 37°C for 24-48 hours;

[0058] S102: Select a single colony, inoculate it into MRS liquid culture medium, and culture it at 37°C for 24-48 hours;

[0059] S103: Take 1% (volume ratio) of the bacterial solution and transfer it to MRS liquid culture medium, and culture at 37° C. for 12-24 hours;

[0060] S104: The lactic acid bacteria content is not less than 1×10 9 CFU / mL, the strain activation is complete.

[0061] The formula of the above-mentioned MRS liquid culture medium is:

[0062] Peptone 10.0g, beef extract 10.0g, yeast extract 5.0g, glucose 20.0g, sodium acetate 5.0g, diammonium citrate 2.0g, Tween-80 1.0g, dipotassium hydrogen phosphate 0.4g, magnesium sulfate 0.58g, manganese sulfate 0.29g, calcium carbonate 20.0g, add distilled water and make up to 1000mL, sterilize at 121℃ for 30min.

[0063] S2: Obtaining liquid fermentation seed solution:

[0064] The three initial bacterial liquids were mixed with the liquid seed fermentation medium A, and allowed to ferment statically to obtain a liquid fermentation seed liquid, specifically:

[0065] The three initial bacterial solutions were mixed with liquid seed fermentation medium A at a ratio of 2%-3% (volume ratio), and fermented at 37° C. for 48 hours to obtain liquid fermentation seed solution. The three initial bacterial solutions were used in the same amount during the mixing process.

[0066] The liquid seed fermentation medium A is obtained by adding 0.5%-1% (volume ratio) of sterile sand mustard extract to the MRS liquid medium, and the formula of the MRS liquid medium is the same as the formula involved in S1. The sand mustard extract is obtained by crushing 500g of sand mustard (Pugionium cornutum (L.) Gaertn.) with a food processor, adding 500ml of water to soak for 30 minutes, filtering the liquid, and sterilizing it at 105°C for 15 minutes.

[0067] S3: Preparation of lactic acid bacteria composite agent:

[0068] The liquid fermentation seed liquid is mixed with the liquid fermentation medium B, and allowed to stand for fermentation to obtain a lactic acid bacteria composite agent, specifically:

[0069] S301: mixing the liquid fermentation seed liquid with the liquid fermentation medium B at a ratio of 10% (volume ratio), allowing the fermentation to proceed at a temperature between 20° C. and 40° C. for 72 to 120 hours;

[0070] S302: The lactic acid bacteria content is not less than 1×10 10 CFU / mL, the fermentation is completed and the lactic acid bacteria composite agent is obtained.

[0071] The formula of the above-mentioned liquid fermentation medium B is:

[0072] Peptone 1% (volume ratio), beef extract 1% (volume ratio), yeast extract 0.5% (volume ratio), glucose 2% (volume ratio), the balance is water, sterilize at 121℃ for 30min.

[0073] The obtained lactic acid bacteria composite agent can be stored in a one-way ventilated barrel and placed in a cool and dark environment at room temperature. It needs to be stirred evenly when used, and can maintain good activity within a shelf life of 3-6 months. When used, it is diluted with water at a ratio of 1:200 (volume ratio), and the dosage per mu is 20 kg.

[0074] The lactic acid bacteria composite agent provided by the present invention can be used to improve saline-alkali soil and promote the growth of crops, and the specific effects are specifically illustrated by the following embodiments.

[0075] Example 1: Tolerance of various strains and lactic acid bacteria composite agents to salt and alkali

[0076] Prepare MRS liquid culture medium containing 0%, 0.5%, 1%, 2%, 3%, 4%, 5% (volume ratio) NaCl respectively, divide it into 10ml sterile test tubes, inoculate rhamnosus lactobacillus 7M1, forsythia lactobacillus 7M7, coryneform lactobacillus LSC-7 and lactobacillus compound bacterial agent MIX according to the ratio of 1% (volume ratio), and culture at 37°C for 24h. Adjust the pH of MRS liquid culture medium to 7, 8, 9, 10, 11 with dilute NaOH, divide it into 10ml sterile test tubes, inoculate rhamnosus lactobacillus 7M1, forsythia lactobacillus 7M7, coryneform lactobacillus LSC-7 and lactobacillus compound bacterial agent MIX according to the ratio of 1% (volume ratio), and culture at 37°C for 24h. After mixing evenly, measure the bacterial concentration under the condition of OD600. Take the MRS bacterial concentration of pH 7 as the positive control, and take the sterile MRS culture fluid as the negative control. Use dilute NaOH to adjust the pH of MRS liquid culture medium containing 3% NaCl to 7, 8, 9, 10, 11, and dispense into 10ml sterile test tubes. Inoculate Lactobacillus rhamnosus 7M1, Lactobacillus forsythiae 7M7, Lactobacillus coryneformis LSC-7 and lactic acid bacteria compound agent MIX at a ratio of 1% (volume ratio), and culture at 37°C for 24h. After mixing evenly, measure the bacterial concentration under OD600 conditions. Use MRS bacterial concentration with a pH of 7 as a positive control, and use sterile MRS culture fluid as a negative control.

[0077] The results show that ( Figure 1 ), when the NaCl concentration was 3%, it had almost no effect on the growth of the strain, and when the concentration was 4% and 5% or above, it had a significant inhibitory effect on the growth. When the NaCl concentration was 3%, different pH conditions had little effect on the growth of the strain. Under the condition of natural salt concentration, high pH was beneficial to the growth of the strain. The three strains and their mixed fermentation bacteria were not affected by low concentrations of salt and alkali.

[0078] Example 2: Experiment on promoting plant root growth by various strains and lactic acid bacteria composite agents

[0079] The three strains and the mixture were inoculated in MRS containing 0.2% L-tryptophan and cultured statically at 37°C for 72 hours. 2 ml of bacterial solution was taken and centrifuged for 2 minutes, and 1 mL of cell-free supernatant was added to 4 mL of 36% H2SO4 solution containing 6.2 mM FeCl3, and reacted at room temperature in the dark for 20 minutes, and then the absorbance at 535 nm was read using a spectrophotometer. The results showed (Table 1) that the three strains could all produce 3-indoleacetic acid, among which Lactobacillus formosanus 7M7 produced the highest amount.

[0080] Table 1 Determination of indoleacetic acid production by strains

[0081]

[0082] After disinfecting the surface of pakchoi seeds, place them in a 9cm plate with sterile filter paper. Soak the seeds in 2ml of filtered sterile fermentation liquid for 2 hours, dry the surface water, plant them in potting soil, and place them in a sunny place at room temperature until the seeds germinate. Use the unsoaked seeds as a negative control to observe the development of the seed root system. It can be seen that after being soaked in Lactobacillus formosanus 7M7 and lactic acid bacteria compound agent MIX, the root system of the seeds grows longer and stronger than the control. Figure 2 , where “CK” is the blank control sample.

[0083] Example 3: Antibacterial test of various strains and lactic acid bacteria composite agents

[0084] Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Bacillus subtilis were used as indicators for detecting the antibacterial activity of LAB. The strains were inoculated in nutrient broth medium and cultured at 28°C on a shaking table at 120 rpm for 24 h.

[0085] After mixing each test bacteria with nutrient agar, pour the plate, and after solidification, punch a circular hole on the plate, add 200μL of lactic acid bacteria solution into the hole. The lower left corner of each plate is the mixed fermentation solution hole, and culture it at 37℃ overnight to observe the inhibition of lactic acid bacteria on the test bacteria. It can be seen that the mixed fermentation solution has a good inhibitory effect on each test bacteria. Figure 3 In each culture dish, the lower left corner shows the effect of lactic acid bacteria compound agent MIX, and the other three are the effects of the corresponding bacteria species on the left.

[0086] The culture broth fermented with the lactic acid bacteria compound agent MIX for 72 hours was filtered through a 0.22 filter membrane to obtain a sterile fermentation broth. The minimum inhibitory concentration (MIC) method was used for determination. In a 96-well plate, 100 μL of nutrient broth medium was added to each well. Then, 100 μL of lactic acid bacteria fermentation supernatant was added and diluted 5 times in a row. Then, 10ul of the indicator strain cell suspension diluted to 2×106 was inoculated; the uninoculated indicator bacteria was used as a negative control; the inoculated but non-lactic acid bacteria sterile fermentation broth was used as a positive control. Growth was evaluated by measuring the optical density at 600nm after 24 hours of incubation. The results showed (Table 2) that the sterile fermentation broth could effectively inhibit the growth of the four indicator bacteria.

[0087] Table 2 Minimum inhibitory concentration (MIC) of sterile fermentation broth

[0088]

[0089] Example 4: Phosphorus and potassium solubilization tests of various strains and lactic acid bacteria composite agents

[0090] 1. NBRIP agar screening method to determine the ability of strains to dissolve phosphate:

[0091] The lactic acid bacteria suspension was grown in MRS for 24 hours, and circular wells were punched on NBRIP agar plates. 200 μL of lactic acid bacteria solution was added to the wells and incubated anaerobically at 37°C for 5 days. The diameter of the halo area around the colony was measured to calculate the phosphate solubility index (PSI). The results are shown in Table 1. Figure 4 (In the figure, the lower right corner of each culture dish shows the effect of the lactic acid bacteria compound agent MIX, and the other three are the effects of the bacteria species marked on the top), as shown in Table 3, the mixed fermentation broth can produce a more effective phosphate solubilizing effect than the three strains alone.

[0092] Table 3 Phosphate solubility index (PSI) measured by strains

[0093]

[0094] 2. Aleksandrov agar medium is used to determine the ability of strains to dissolve potassium:

[0095] The lactic acid bacteria suspension was grown in MRS for 24 hours, and circular wells were punched on Aleksandrov agar. 200 μL of lactic acid bacteria solution was added to the wells and incubated anaerobically at 37°C for 4 days. The halo area around the colony was measured to calculate the potassium solubility index (KSI). Figure 5 (In the figure, the lower left corner of each culture dish shows the effect of the lactic acid bacteria compound agent MIX, and the other three are the effects of the bacteria species marked in the upper left corner), as shown in Table 4, the mixed fermentation liquid has a better potassium dissolving effect.

[0096] Table 4 Potassium solubility index (PSI) measured by strains

[0097]

[0098] Example 5: Effect of using lactic acid bacteria composite agent on greenhouse celery in greenhouse

[0099] In the greenhouse, the plot was divided into two equal-sized areas, with area 1 as the treatment and area 2 as the control. Lactobacillus compound agents were used three times in the early, middle and late stages of crop growth, with area 1:200 irrigated with lactobacillus compound liquid, with a dosage of 20 kg per mu, and area 2 irrigated with the same amount of water as the control. The rest of the time, crop maintenance and management were carried out according to daily routine.

[0100] The corresponding indicators were collected and tested in the middle of crop growth and harvest period. It can be seen from the soil physical and chemical indicators (Table 5) that the pH of the soil using lactic acid bacteria agent has decreased, and the levels of organic matter, available phosphorus, available potassium and alkaline nitrogen have increased.

[0101] Table 5 Soil physical and chemical indicators

[0102]

[0103] After using the lactic acid bacteria compound agent, the root system of the crop is more developed, the root hairs grow vigorously, the crop grows taller and stronger, and the yield is 10% higher than the control. The crude fiber content and crude protein content of celery crops are higher than those of the control group. Figure 6 , Figure 7 , as shown in Table 6 and Table 7.

[0104] Table 6 Crop growth indicators in the early stage of use

[0105]

[0106] Table 7 Nutrient index of celery

[0107]

[0108] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A lactic acid bacteria composite agent, characterized in that: The lactic acid bacteria composite agent includes Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7; The Lactobacillus rhamnosus 7M1 was deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with a deposit date of December 2, 2024 and a deposit number of CGMCC No. 32861. The Lactobacillus futsaii 7M7 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with a deposit date of December 2, 2024 and a deposit number of CGMCC No. 32862. The Lactobacillus coryniformis LSC-7 is deposited in the General Microbiology Center of the China Culture Collection Administration, with a deposit date of December 2, 2024 and a deposit number of CGMCCN0.32863.

2. The method for preparing the composite lactic acid bacteria agent according to claim 1, characterized in that: The method comprises: Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7 were activated respectively to obtain three initial bacterial solutions; The three initial bacterial liquids are mixed with the liquid seed fermentation medium A, and allowed to ferment statically to obtain a liquid fermentation seed liquid; The liquid fermentation seed liquid is mixed with the liquid fermentation medium B, and allowed to ferment statically to obtain a lactic acid bacteria composite bacterial agent.

3. The method for preparing the lactic acid bacteria composite agent according to claim 2, characterized in that: Lactobacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Lactobacillus coryniformis LSC-7 were activated respectively, including: The bacteria in the -80℃ cryotubes were streaked on MRS solid plates for activation and cultured at 37℃ for 24-48 hours; Select a single colony, inoculate it into MRS liquid medium, and culture it at 37°C for 24-48 hours; Take 1% of the bacterial solution and transfer it to MRS liquid medium, and culture it at 37℃ for 12-24 hours; The lactic acid bacteria content is not less than 1×10 9 CFU / mL, the strain activation is complete.

4. The method for preparing the lactic acid bacteria composite agent according to claim 3, characterized in that: The formula of MRS liquid medium is: Peptone 10.0g, beef extract 10.0g, yeast extract 5.0g, glucose 20.0g, sodium acetate 5.0g, diammonium citrate 2.0g, Tween-80 1.0g, dipotassium hydrogen phosphate 0.4g, magnesium sulfate 0.58g, manganese sulfate 0.29g, calcium carbonate 20.0g, add distilled water and make up to 1000mL, sterilize at 121℃ for 30min.

5. The method for preparing the composite lactic acid bacteria agent according to claim 4, characterized in that: The three initial bacterial liquids are mixed with the liquid seed fermentation medium A, and allowed to ferment statically to obtain a liquid fermentation seed liquid, including: The three initial bacterial liquids were mixed with liquid seed fermentation medium A at a ratio of 2%-3%, and allowed to ferment at 37° C. for 48 hours to obtain liquid fermentation seed liquid.

6. The method for preparing the composite lactic acid bacteria agent according to claim 5, characterized in that: The liquid seed fermentation medium A is obtained by adding 0.5%-1% of sterile sand mustard extract into the MRS liquid medium.

7. The method for preparing the composite lactic acid bacteria agent according to claim 6, characterized in that: The liquid fermentation seed liquid is mixed with the liquid fermentation medium B, and allowed to stand for fermentation to obtain a lactic acid bacteria composite agent, including: Mix the liquid fermentation seed liquid with the liquid fermentation medium B at a ratio of 10%, and ferment at a temperature between 20 and 40° C. for 72 to 120 hours; The lactic acid bacteria content is not less than 1×10 10 CFU / mL, the fermentation is completed and the lactic acid bacteria composite agent is obtained.

8. The method for preparing the composite lactic acid bacteria agent according to claim 7, characterized in that: The formula of liquid fermentation medium B is: Peptone 1%, beef extract 1%, yeast extract 0.5%, glucose 2%, the balance is water, sterilize at 121℃ for 30min.

9. Use of the lactic acid bacteria composite agent as claimed in claim 1 in improving saline-alkali soil.

10. Use of the lactic acid bacteria composite agent according to claim 1 in promoting the growth of crops.

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