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

Abstract

The present application relates to a kind of lactic acid bacteria complex microbial inoculant and its preparation method and the application in saline soil improvement and promoting crop growth, the lactic acid bacteria complex microbial inoculant includes Lacticaseibacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Loigolactobacillus coryniformis LSC-7.The lactic acid bacteria complex microbial inoculant is applied in saline soil, can reach the effect of improving soil, improving crop yield and quality, and increasing the disease resistance of agricultural products, suitable for the production of green pollution-free agricultural products in modern agricultural production, low cost and simple operation, with the advantages of good repair effect, environment-friendly, do not affect agricultural production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microbial technology, in particular to a lactic acid bacteria complex microbial agent, a preparation method thereof and application thereof in saline-alkali soil improvement and crop growth promotion. BACKGROUND

[0002] The saline-alkali land has the characteristics of high salt content or high alkalinity, which leads to poor soil structure, easy to be cemented, low organic matter content, nutrient-poor, weak fertilizer retention capacity, and is not suitable for crop planting. After improvement, part of the saline-alkali land with agricultural utilization prospect 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 arable land.

[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 environment for crops. Traditional methods of saline-alkali soil improvement include salt washing by drainage, soil improvement by guest soil, and application of organic fertilizer. The salt washing by drainage measure mainly reduces the salt content by digging drainage ditches and lowering the groundwater level. This method requires a large amount of manpower and material resources, and the effect is not lasting. The soil improvement by guest soil measure is to transport the soil from non-saline-alkali land to the saline-alkali land and cover it on the saline-alkali soil to reduce the soil salt content. Although this method can quickly reduce the soil salt content, it requires a large amount of guest soil source and is easy to cause soil pollution and damage to the ecological environment. The application of organic fertilizer measure mainly increases the soil organic matter content by applying organic fertilizer to improve the soil fertility and water retention capacity, thereby reducing the soil salt content. This method needs to be adhered to for a long time and has a strong dependence on fertilizer.

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

[0005] The purpose of the present application is to provide a lactic acid bacteria complex microbial agent, a preparation method thereof and application thereof in saline-alkali soil improvement and crop growth promotion, in order to solve the problems of high investment, non-lasting effect and easy damage to the ecological environment existing in the prior art.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A lactic acid bacteria complex microbial agent is provided, which comprises Lacticaseibacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Loigolactobacillus coryniformis LSC-7.

[0008] The Lacticaseibacillus rhamnosus 7M1 is preserved in the China General Microbiological Culture Collection Center on December 2, 2024, and the preservation number is CGMCC N0.32861.

[0009] The Lactobacillus futsaii 7M7 is preserved in the China General Microbiological Culture Collection Center on December 2, 2024, and the preservation number is CGMCC N0.32862.

[0010] The Loigolactobacillus coryniformis LSC-7 is preserved in the China General Microbiological Culture Collection Center on December 2, 2024, and the preservation number is CGMCC N0.32863.

[0011] In another aspect, a preparation method of the lactic acid bacteria complex bacterium agent as described is provided, and the method comprises:

[0012] The Lacticaseibacillus rhamnosus 7M1, the Lactobacillus futsaii 7M7 and the Loigolactobacillus coryniformis LSC-7 are activated respectively to obtain three initial bacterial solutions.

[0013] The three initial bacterial solutions are mixed with a liquid seed fermentation medium A, and fermentation is carried out to obtain a liquid fermentation seed solution.

[0014] The liquid fermentation seed solution is mixed with a liquid fermentation medium B, and fermentation is carried out to obtain the lactic acid bacteria complex bacterium agent.

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

[0016] The bacterial strain in the -80℃ cryopreservation tube is streaked on an MRS solid plate for activation, and cultured at 37℃ for 24-48 hours;

[0017] A single colony is selected and inoculated into an MRS liquid medium, and cultured at 37℃ for 24-48 hours;

[0018] Take 1% of the bacteria solution and transfer it to MRS liquid medium, incubate at 37°C for 12-24 hours;

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

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

[0021] Proteose peptone 10.0g, beef extract 10.0g, yeast extract 5.0g, glucose 20.0g, sodium acetate 5.0g, citric acid diamine 2.0g, Tween-80 1.0g, potassium 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°C for 30min.

[0022] Further, mix the three initial bacterial solutions together with liquid seed fermentation medium A, and ferment at rest to obtain a liquid fermentation seed solution, including:

[0023] Mix the three initial bacterial solutions at a ratio of 2%-3% with liquid seed fermentation medium A, and ferment at rest at 37°C for 48 hours to obtain a liquid fermentation seed solution.

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

[0025] Further, mix the liquid fermentation seed solution with liquid fermentation medium B, and ferment at rest to obtain a lactic acid bacteria complex inoculant, including:

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

[0027] When the content of lactic acid bacteria is not less than 1×10 10 CFU / mL, the fermentation is completed to obtain a lactic acid bacteria complex inoculant.

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

[0029] Proteose peptone 1%, beef extract 1%, yeast extract 0.5%, glucose 2%, the balance being water, sterilize at 121°C for 30min.

[0030] On the other hand, the application provides the use of the lactic acid bacteria complex inoculant as described in the improvement of saline-alkali soil.

[0031] On the other hand, the application provides the use of the lactic acid bacteria complex inoculant as described in the promotion of crop growth.

[0032] Compared with the prior art, the application has the following advantages:

[0033] The application provides a lactic acid bacteria composite microbial inoculant, a preparation method thereof and application of the lactic acid bacteria composite microbial inoculant in saline-alkali soil improvement and crop growth promotion. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings of other embodiments can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0035] Figure 1 is a comparison chart of the effects of salt concentration and pH on the growth of Lactobacillus rhamnosus 7M1, Lactobacillus fujiensis 7M7, Lactobacillus coryniformis LSC-7 and lactic acid bacteria composite microbial inoculant MIX. In the chart, (a) is the effect of different concentrations of NaCl on the growth of lactic acid bacteria, and (b) is the effect of different pH on the growth of lactic acid bacteria under the condition of 3% NaCl.

[0036] Figure 2 is a comparison chart of the promotion effects of Lactobacillus rhamnosus 7M1, Lactobacillus fujiensis 7M7, Lactobacillus coryniformis LSC-7 and lactic acid bacteria composite microbial inoculant MIX on plant root systems.

[0037] Figure 3 is a comparison chart of the antibacterial test of Lactobacillus rhamnosus 7M1, Lactobacillus fujiensis 7M7, Lactobacillus coryniformis LSC-7 and lactic acid bacteria composite microbial inoculant MIX on test bacteria.

[0038] Figure 4 is a comparison chart of the phosphorus solubilization effects of Lactobacillus rhamnosus 7M1, Lactobacillus fujiensis 7M7, Lactobacillus coryniformis LSC-7 and lactic acid bacteria composite microbial inoculant MIX.

[0039] Figure 5 is a comparison chart of the potassium solubilization effects of Lactobacillus rhamnosus 7M1, Lactobacillus fujiensis 7M7, Lactobacillus coryniformis LSC-7 and lactic acid bacteria composite microbial inoculant MIX.

[0040] Figure 6 is a comparison chart of the use effects of the lactic acid bacteria composite microbial inoculant on facility vegetables in a greenhouse (after picking). is a comparison chart of the use effects of the lactic acid bacteria composite microbial inoculant on facility vegetables in a greenhouse (after picking).

[0041] Figure 7 Figure is a comparison chart of the use effect of the lactic acid bacteria complex microbial agent on the facility vegetables in the greenhouse (in planting). DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized 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 application more thorough and comprehensive.

[0043] In the description of the present application, it should be understood that all the technical and scientific terms used have the same meaning as generally understood by those skilled in the art to which the present application belongs. When there is a conflict, the definition in the specification shall prevail. If not specifically indicated, the technical means used in the examples are the conventional means known to those skilled in the art, the reagents used in the examples are commercially available, and the devices used in the examples are existing devices. The limitation of means, reagents or devices cannot be understood as the limitation of the present application, and the means, reagents or devices of the same type solving the same technical problem are within the protection scope of the present application.

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

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

[0046] The present application provides a lactic acid bacteria complex microbial agent, which can be used for improving saline-alkali soil and promoting crop growth, increasing the yield of agricultural products, and increasing the disease resistance of agricultural products, and is suitable for the production of green and non-polluted agricultural products in modern agricultural production.

[0047] Specifically, the lactic acid bacteria complex agent comprises Lacticaseibacillus rhamnosus 7M1, Lactobacillus futsaii 7M7, and Loigolactobacillus coryniformis LSC-7.

[0048] In the formula, R represents a C1-C6 alkyl group, and n represents an integer of 1-3.

[0049] The Lacticaseibacillus rhamnosus 7M1 is preserved in the China General Microbiological Culture Collection Center on December 2, 2024, and has a preservation number of CGMCC N0.32861. The Lacticaseibacillus rhamnosus 7M1 is isolated and screened from pickled mustard leaf kimchi.

[0050] The Lactobacillus futsaii 7M7 is preserved in the China General Microbiological Culture Collection Center on December 2, 2024, and has a preservation number of CGMCC N0.32862. The Lactobacillus futsaii 7M7 is isolated and screened from pickled mustard leaf kimchi.

[0051] The Loigolactobacillus coryniformis LSC-7 is preserved in the China General Microbiological Culture Collection Center on December 2, 2024, and has a preservation number of CGMCC N0.32863. The Loigolactobacillus coryniformis LSC-7 is isolated and screened from fresh small green vegetables.

[0052] The above three strains are lactic acid bacteria. Lactic acid bacteria are a kind of bacteria that use sugar as a substrate, produce lactic acid and other organic acids, and secrete bacteriocins and other plant pathogen growth inhibitors. They are safe and edible, and are the safest agricultural microbial strains. Plant-derived lactobacillus was previously considered an important probiotic group in fermented foods. However, it has been found that this type of microorganism promotes biodegradation, promotes the transformation of nutrients such as phosphorus and potassium, regulates pH, produces organic acid and bacteriocin metabolites, stimulates shoot and root growth, and has antagonistic effects on plant pathogens. It can inhibit pathogenic fungi and bacterial populations in the rhizosphere and phyllosphere. In sustainable agricultural development, maintaining soil health, promoting organic agriculture, promoting plant health, and ensuring the safety and health of people, the development of this type of microorganism can also ensure the safety and health of people. Therefore, it has the advantages of low treatment cost, simple construction, no secondary pollution, and little impact on the environment.

[0053] Based on the above three lactic acid bacteria, a lactic acid bacteria complex microbial agent can be prepared. The specific preparation method includes the following steps:

[0054] S1: strain activation:

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

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

[0057] S101: The strain in the -80℃ cryopreserved tube was streaked on an MRS solid plate and cultured at 37℃ for 24-48 hours;

[0058] S102: A single colony was selected and inoculated into MRS liquid medium and cultured at 37℃ for 24-48 hours;

[0059] S103: 1% (volume ratio) of the bacterial solution was transferred to MRS liquid medium and cultured at 37℃ for 12-24 hours;

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

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

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

[0063] S2: Obtain liquid fermentation seed liquid:

[0064] Mix the three initial bacterial liquids together with the liquid seed fermentation medium A, and stand for fermentation to obtain the liquid fermentation seed liquid, specifically:

[0065] Mix the three initial bacterial liquids at a ratio of 2%-3% (volume ratio) with the liquid seed fermentation medium A, and stand for fermentation at 37℃ for 48 hours to obtain the liquid fermentation seed liquid. The three initial bacterial liquids are 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 oyster extract to the MRS liquid medium, and the formula of the MRS liquid medium is the same as that involved in S1. The process of obtaining the sand oyster extract is as follows: grind 500 g of sand oyster (Pugionium cornutum (L.) Gaertn.) with a food processor, soak in 500 ml of water for 30 min, filter the liquid, and sterilize at 105℃ for 15 min.

[0067] S3: Prepare lactic acid bacteria complex inoculant:

[0068] Mix the liquid fermentation seed liquid with the liquid fermentation medium B, and stand for fermentation to obtain the lactic acid bacteria complex inoculant, specifically:

[0069] S301: Mix the liquid fermentation seed liquid at a ratio of 10% (volume ratio) with the liquid fermentation medium B, and stand for fermentation, maintaining the temperature between 20-40℃, for 72-120 hours;

[0070] S302: When the content of lactic acid bacteria is not less than 1×10 10 CFU / mL, complete the fermentation to obtain the lactic acid bacteria complex inoculant.

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

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

[0073] The obtained lactic acid bacteria compound microbial inoculant can be stored in a one-way breathable barrel, placed in a room temperature, cool, and light-proof environment, and needs to be stirred uniformly before use, and can maintain good activity for 3-6 months. When used, it is diluted with water at a ratio of 1:200 (volume ratio), and the use amount per mu is 20 kg.

[0074] The lactic acid bacteria compound microbial inoculant provided by the application can be used for saline-alkali soil improvement and promoting crop growth, and the specific effects are illustrated by the following examples.

[0075] Example 1: Tolerance of each strain and lactic acid bacteria compound microbial inoculant to saline-alkali

[0076] MRS liquid culture media containing 0%, 0.5%, 1%, 2%, 3%, 4%, and 5% (volume ratio) NaCl were prepared and dispensed in 10 ml sterile test tubes, and Lactobacillus rhamnosus 7M1, Lactobacillus paracasei 7M7, Lactobacillus coryniformis LSC-7, and lactic acid bacteria compound microbial inoculant MIX were inoculated in the MRS liquid culture media at a ratio of 1% (volume ratio) and incubated at 37°C for 24 hours. The pH of the MRS liquid culture media was adjusted to 7, 8, 9, 10, and 11 with dilute NaOH, and the MRS liquid culture media were dispensed in 10 ml sterile test tubes, and Lactobacillus rhamnosus 7M1, Lactobacillus paracasei 7M7, Lactobacillus coryniformis LSC-7, and lactic acid bacteria compound microbial inoculant MIX were inoculated in the MRS liquid culture media at a ratio of 1% (volume ratio) and incubated at 37°C for 24 hours. After mixing, the bacterial concentration under OD600 was determined. The bacterial concentration of the MRS liquid culture medium with pH 7 was used as a positive control, and the sterile MRS culture solution was used as a negative control. The pH of the MRS liquid culture medium containing 3% NaCl was adjusted to 7, 8, 9, 10, and 11 with dilute NaOH, and the MRS liquid culture medium was dispensed in 10 ml sterile test tubes, and Lactobacillus rhamnosus 7M1, Lactobacillus paracasei 7M7, Lactobacillus coryniformis LSC-7, and lactic acid bacteria compound microbial inoculant MIX were inoculated in the MRS liquid culture medium at a ratio of 1% (volume ratio) and incubated at 37°C for 24 hours. After mixing, the bacterial concentration under OD600 was determined. The bacterial concentration of the MRS liquid culture medium with pH 7 was used as a positive control, and the sterile MRS culture solution was used as a negative control.

[0077] The results show that Figure 1 ), the growth of the strains is almost not affected when the NaCl concentration is 3%, and the growth is significantly inhibited when the concentration is 4% and 5% or more. When the NaCl concentration is 3%, different pH conditions have little effect on the growth of the strains, and under the condition of natural salt concentration, high pH is beneficial to the growth of the strains. The three strains and their mixed fermentation bacteria are not affected by low concentration of saline-alkali.

[0078] Example 2: Test of each strain and lactic acid bacteria compound microbial inoculant for promoting plant root system

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

[0080] Table 1: Indoleacetic acid production content determination of strains

[0081]

[0082] The surface of the small green seed was sterilized and placed in a sterile filter paper 9cm dish. After soaking the seeds in 2ml of filtered sterile fermentation liquid for 2 hours, the surface moisture was absorbed and planted in a potting soil, placed in a room temperature sunny place, and the seeds were germinated. The seeds without soaking were used as negative control to observe the root development of the seeds. It can be seen that after soaking in Lactobacillus fugetanum 7M7 and lactic acid bacteria complex inoculant MIX, the root system of the seeds grew longer and stronger than the control, such as Figure 2 wherein "CK" is a blank control sample.

[0083] Example 3: Antimicrobial test of each strain and lactic acid bacteria complex inoculant

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

[0085] Each test bacteria was mixed with nutrient agar, poured into a plate, and after solidification, a round hole was punched on the plate, and 200μL of lactic acid bacteria liquid was added into the hole. The lower left corner of each plate was the mixed fermentation liquid hole, and the plates were incubated at 37°C overnight. The inhibition of lactic acid bacteria on the test bacteria was observed. It can be seen that the mixed fermentation liquid has good inhibition effect on each test bacteria. For example, Figure 3 In each culture dish, the lower left corner is the effect of lactic acid bacteria complex inoculant MIX, and the other three are the effects of the corresponding strains on the left side.

[0086] The lactic acid bacteria complex inoculum MIX fermentation broth was filtered through 0.22 filter membrane to obtain sterile fermentation broth. The minimum inhibitory concentration (MIC) method was used for determination. In 96-well plates, 100 μL nutrient broth medium was added to each well. Then, 100 μL lactic acid bacteria fermentation supernatant was added, and diluted by 5 times successively. Then, 10 ul of the cell suspension of the indicator strain diluted to 2 x 106was inoculated; the indicator strain without inoculation was used as a negative control; the inoculation without lactic acid bacteria sterile fermentation broth was used as a positive control. The growth was evaluated by measuring the optical density at 600 nm after 24 h of incubation. The results showed (Table 2) that the sterile fermentation broth could effectively inhibit the growth of the four indicator strains.

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

[0088]

[0089] Example 4: Phosphorus and potassium solubilization test of each strain and lactic acid bacteria complex inoculum

[0090] 1. NBRIP agar screening method for determining the ability of the strain to solubilize phosphate:

[0091] The lactic acid bacteria suspension was grown in MRS for 24 hours, and a round hole was punched on the NBRIP agar plate, 200 μL of lactic acid bacteria broth was added in the hole, and anaerobic incubation was carried out at 37°C for 5 days. The diameter of the halo area around the colony was measured to calculate the phosphate solubilization index (PSI), and the results are shown in Figure 4 (Fig., the lower right corner of each dish is the effect of lactic acid bacteria complex inoculum MIX, and the other three are the effects of the top identified strains), and Table 3 shows that the mixed fermentation broth can more effectively produce phosphorus solubilization effect than the three strains alone.

[0092] Table 3 Measured phosphate solubilization index (PSI) of the strains

[0093]

[0094] 2. Aleksandrov agar medium for determining the ability of the strain to solubilize potassium:

[0095] The lactic acid bacteria suspension was grown in MRS for 24 hours, and a round hole was punched on the Aleksandrov agar, 200 μL of lactic acid bacteria broth was added in the hole, and anaerobic incubation was carried out at 37°C for 4 days. The halo area around the colony was measured to calculate the potassium solubilization index (KSI). The results are shown in Figure 5 (Fig., the lower right corner of each dish is the effect of lactic acid bacteria complex inoculum MIX, and the other three are the effects of the top identified strains), and Table 4 shows that the mixed fermentation broth has a better potassium solubilization effect.

[0096] Table 4 Measured potassium solubilization index (PSI) of the strains

[0097]

[0098] Example 5: Use effect of lactic acid bacteria complex microbial agent on facility celery in a greenhouse

[0099] The land in the facility greenhouse was divided into two equal-area sections, one section was treated and the other was used as a control. The lactic acid bacteria complex microbial agent was used three times according to the growth of the crops, wherein section 1 was irrigated with 200 kg of lactic acid bacteria complex microbial solution per mu, and section 2 was irrigated with an equal amount of water as a control. The crops were maintained and managed according to the daily routine at other times.

[0100] The corresponding indicators were collected and detected at the middle and harvest stages of crop growth. As can be seen from Table 5, the soil treated with the lactic acid bacteria agent had a lower pH, and the levels of organic matter, available phosphorus, available potassium, and alkali-hydrolyzed nitrogen were improved.

[0101] Table 5 Soil physical and chemical indicators

[0102]

[0103] After using the lactic acid bacteria complex microbial agent, the crop root system was more developed, the hair roots grew vigorously, the crop growth was higher and more robust, and the yield was 10% higher than the control. The crude fiber content and crude protein content of the celery crop were higher than those of the control group, as shown in Table 6 and Table 7. Figure 6 、 Figure 7

[0104] Table 6 Crop growth indicators at the initial stage of use

[0105]

[0106] Table 7 Nutrient indicators of celery

[0107]

[0108] The above application of specific examples is used to illustrate the present application and is used to help understand the present application, and does not limit the present application. For those skilled in the art to which the present application belongs, according to the idea of the present application, a number of simple deductions, deformations, or substitutions can be made.​

Claims

1. A compound lactic acid bacteria agent, characterized in that: The lactic acid bacteria compound agent includes Lacticaseibacillus rhamnosus 7M1, Lactobacillus futsaii 7M7 and Loigolactobacillus scoryniformis LSC-7. The Lacticaseibacillus rhamnosus 7M1 strain is deposited at the China General Microbiological Culture Collection Center (CGMCC) on December 2, 2024, with accession number CGMCC No. 32861. The Lactobacillus futsaii 7M7 strain is deposited at the China General Microbiological Culture Collection Center (CGMCC) on December 2, 2024, with accession number CGMCC No. 32862. The Lactobacillus coryniformis LSC-7 is deposited at the China General Microbiological Culture Collection Center on December 2, 2024, with accession number CGMCCN0.32863.

2. The preparation method of the lactic acid bacteria compound inoculant as described in claim 1, characterized in that: The method includes: Three initial bacterial cultures were obtained by activating Lacticaseibacillus rhamnosus 7M1, Lactobacillus futsaii 7M7, and Loigolactobacillus coryniformis LSC-7, respectively. The three initial bacterial cultures were mixed together with liquid seed fermentation medium A and allowed to ferment statically to obtain liquid fermentation seed culture. The liquid fermentation seed liquid was mixed with liquid fermentation medium B and allowed to ferment statically to obtain a lactic acid bacteria compound inoculant.

3. The method for preparing the lactic acid bacteria compound inoculant according to claim 2, characterized in that: Activation was performed on *Lactaseibacillus rhamnosus* 7M1, *Lactobacillus futsaii* 7M7, and *Loigolactobacillus coryniformis* LSC-7, respectively, including: The bacterial strains in the -80℃ cryovials were streaked onto MRS solid plates for activation and then incubated at 37℃ for 24-48 hours. Select a single colony and inoculate it into MRS liquid medium, then incubate at 37°C for 24-48 hours; Take 1% of the bacterial culture and transfer it to MRS liquid medium, and incubate at 37°C for 12-24 hours; The lactic acid bacteria content is not less than 1×10 9 The strain activation was completed at a concentration of CFU / mL.

4. The method for preparing the lactic acid bacteria compound inoculant according to claim 3, characterized in that: The formula for MRS liquid culture medium is as follows: 10.0g peptone, 10.0g beef extract, 5.0g yeast extract, 20.0g glucose, 5.0g sodium acetate, 2.0g diamine citrate, 1.0g Tween-80, 0.4g dipotassium hydrogen phosphate, 0.58g magnesium sulfate, 0.29g manganese sulfate, and 20.0g calcium carbonate were added to distilled water, bringing the total volume to 1000mL. The mixture was then sterilized at 121℃ for 30min.

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

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

7. The method for preparing the lactic acid bacteria compound inoculant according to claim 6, characterized in that: The liquid fermentation seed culture was mixed with liquid fermentation medium B and allowed to ferment statically to obtain a lactic acid bacteria compound inoculant, comprising: Mix the liquid fermentation seed liquid with liquid fermentation medium B at a ratio of 10%, let it ferment statically, maintain the temperature between 20-40℃, and ferment for 72-120 hours. The lactic acid bacteria content is not less than 1×10 10 Fermentation was completed at CFU / mL, yielding a compound lactic acid bacteria inoculum.

8. The method for preparing the lactic acid bacteria compound inoculant according to claim 7, characterized in that: The formula for liquid fermentation medium B is as follows: 1% peptone, 1% beef extract, 0.5% yeast extract, 2% glucose, with the remainder being water, sterilized at 121°C for 30 minutes.

9. The application of the lactic acid bacteria compound agent as described in claim 1 in the improvement of saline-alkali soil.

10. The application of the lactic acid bacteria compound inoculant as described in claim 1 in promoting crop growth.

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