Stress-tolerant bacillus velezensis L-29 and application thereof

Abstract

The invention relates to the technical field of agricultural microorganisms, and discloses stress-tolerant bacillus velezensis L-29 and application thereof. The bacillus velezensis L-29 is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number is CGMCC No.35587. The bacillus velezensis L-29 is named as bacillus velezensis L-29. Experiments prove that the bacillus velezensis L-29 can adapt to various extreme environments, can survive and proliferate under the extreme environments of drought conditions simulated by 0-25% PEG 6000 under the conditions that the pH is 2-12 and the salt concentration is 1.5%, and has various functions of soil improvement (organic matter decomposition and phosphorus activation), plant growth promotion, broad-spectrum disease control and the like. In the secondary fermentation stage of compost, humus generation can be remarkably promoted, compost maturation is accelerated, the good colonization ability is achieved, and after an obtained compost product is applied to normal soil, the nutrient effectiveness can be improved, crop growth is promoted, and the disease resistance is enhanced.

Description

Technical Field

[0001] This invention relates to the field of agricultural microbiology, specifically to a stress-resistant Bacillus belye L-29 strain and its applications. Background Technology

[0002] Bio-organic fertilizer is a type of green input widely used in agricultural production. It is made by combining organic fertilizer with functional microorganisms and has a comprehensive effect of improving soil, increasing nutrient utilization, enhancing crop resistance and promoting growth.

[0003] In bio-organic fertilizers, humus is one of the key components determining fertilizer efficiency. Humus not only improves soil aggregate structure and enhances water and fertilizer retention capacity, but also provides a continuous source of nutrition for plants, serving as an important material basis for healthy crop growth. However, the fermentation process of conventional organic fertilizers is affected by various factors such as the properties of raw materials, environmental temperature, moisture, and microbial communities, making it difficult to guarantee the efficiency of humus synthesis and often resulting in poor quality of the final product. Therefore, how to efficiently and stably promote humus formation during the fermentation process of organic fertilizers has always been a key focus of academic and industrial attention.

[0004] Functional microorganisms are key to sustainable agricultural development. As a core component of bio-organic fertilizers, they directly act on the soil-plant system, achieving multiple effects such as soil improvement, nutrient activation, and enhanced crop resistance. Currently, microbial agents are used to promote composting fermentation and enhance humus synthesis, but these methods have significant limitations. For example, Chinese invention patent application number 202510346868.5 discloses an organic fertilizer that promotes plant growth and soil improvement, and its preparation method. This organic fertilizer uses composted chicken manure, soybean meal, straw powder, and sweet potato vines as raw materials, and contains a compound microbial agent composed of *Actinomyces madurae*, *Pseudomonas schrenckii*, and *Bacillus belye*, as well as rosmarinic acid and glucosamine sulfate solution as stimulants. It is prepared through steps such as raw material mixing, moisture regulation fermentation, granulation, and drying, and can promote cabbage growth, increase yield, and improve soil physicochemical properties. However, this patent only compares the growth-promoting effects of the compound agent and a single strain on crops and does not verify whether functional microorganisms can colonize the fermentation products. Chinese invention patent application number 202311866298.X discloses a disease-resistant and growth-promoting synthetic microbial community, a complete bio-organic fertilizer containing this microbial community, its preparation method, and its application. The microbial community is composed of Bacillus megaterium, Bacillus mucilaginosus, and Bacillus belyssus, etc. The complete bio-organic fertilizer contains this microbial community, well-rotted organic fertilizer, inorganic compound fertilizer, and amino acids. It is prepared through steps such as separate fermentation and secondary composting fermentation, which can improve fertilizer utilization, reduce chemical fertilizer usage, promote vegetable growth, and reduce the occurrence of soil-borne diseases. However, it cannot be confirmed whether the functional strains can continuously play a role in the disease resistance and growth-promoting results. Chinese invention patent application number 202411483940.0 discloses Bacillus belyssus LF-9 and its application in agricultural production. This strain can efficiently produce cellulase, promote plant growth, and prevent potato black scurf and black shank disease. It can also be used for agricultural waste treatment to shorten the composting cycle and improve compost quality, but it is not verified whether the functional microorganisms can colonize in the fermentation products.

[0005] Ideal functional strains need to possess high stress tolerance (such as tolerance to extreme environments like acidity, alkalinity, salinity, and drought), abundant enzyme activity (such as proteases and cellulases to promote the decomposition of organic matter), and pathogen antagonism, thereby maintaining stable function under complex field conditions. *Bacillus belyssiensis*, as a common probiotic, has the potential to synergistically achieve integrated "soil improvement-growth promotion-disease prevention," but existing strains often have limited functionality or insufficient environmental adaptability. For example, Chinese invention patent application number 202510635009.8 discloses a *Bacillus belyssiensis* DSSR-2, which can inhibit eight pathogens, exhibits broad-spectrum antibacterial activity, and can prevent root rot and leaf spot diseases in medicinal herbs, while simultaneously promoting the growth of *Salvia miltiorrhiza* and *Scutellaria baicalensis*. However, these functional microorganisms are usually immobilized in well-rotted organic fertilizer through blending to form bio-organic fertilizer, in order to avoid the inhibition of functional strains by the complex environment of high temperature, high salt, high pH, ​​and ammonia content in compost, and to maintain their effective quantity. Chinese invention patent application number 202510448466.6 relates to a method for preparing a microbial inoculant and organic fertilizer. The microbial inoculant comprises a compound inoculant consisting of Bacillus belye, Pseudomonas montmorillonii, and Lactobacillus pentosus, as well as modified saponins as promoters and nutrients such as amino acids and zinc. The organic fertilizer is made from agricultural waste, manure, and the microbial inoculant through calcination, fermentation, and granulation. It can control diseases and promote the growth of corn and cucumbers. However, most of the functional strains used in this field mainly promote crop growth, with little effect on promoting humus formation. They cannot significantly improve the composting process of organic fertilizer, thus limiting the fertilizer efficiency of bio-organic fertilizer and making it difficult to add it directly during fertilizer production.

[0006] This reveals significant limitations in the current synergistic application of microorganisms and carriers: on the one hand, most functional strains, due to their poor stress tolerance, struggle to survive in the high-temperature, high-salt environment of composting, necessitating the use of later-stage blending processes, resulting in low colonization rates and functional instability; on the other hand, microbial agents focused on composting lack direct disease-promoting capabilities, failing to achieve multifunctional synergy. This disconnect limits the effectiveness of biofertilizers, making it difficult to meet the demands of green agriculture for highly efficient and stable microbial strains.

[0007] Therefore, the current technological gap lies in the lack of a core strain that possesses strong stress resistance, multifunctionality (such as promoting decay, growth, and disease resistance), and can synergize efficiently with organic fertilizer carriers. This invention aims to fill this gap using Bacillus belyssus L-29, whose characteristics provide a basis for direct carrier optimization. Summary of the Invention

[0008] The purpose of this invention is to provide a stress-resistant Bacillus belyceae L-29 strain and its applications. This strain is resistant to acid, alkali, salt, and drought, and can survive and proliferate in extreme environments. It also exhibits good crop growth-promoting and fermentation capabilities, producing high levels of protease, amylase, and cellulase, and can effectively dissolve organic phosphorus. It maintains a high colonization rate even in the later stages of composting and provides excellent disease resistance and growth-promoting effects when crops are returned to the field.

[0009] To achieve the above objectives, the present invention provides a stress-resistant strain of Bacillus belyssus L-29, wherein Bacillus belyssus ( Bacillus velezensis L-29 is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35587, on August 12, 2025, at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0010] Furthermore, the aforementioned Bacillus belyss L-29 exhibits the following stress resistance: Acid and alkali resistance: It can survive and multiply in environments with a pH of 2 to 12; Salt tolerance: It can survive and multiply in environments with concentrations of NaCl, Na2SO4, or Na2CO3 up to 15‰. Drought resistance: It can survive and proliferate in a drought environment simulated by 0~25% PEG6000.

[0011] Furthermore, the Bacillus belye L-29 is capable of secreting indole-3-acetic acid and has the ability to produce protease, amylase, cellulase and lysozyme.

[0012] Furthermore, the *Bacillus belye* L-29 is effective against *Fusarium oxysporum* (…). Fusarium oxysporum ), Alternaria brassicae ( Alternaria brassicae ) and Rhizoctonia solani ( Rhizoctonia solani It has an antagonistic effect.

[0013] This invention also provides the application of Bacillus belyssus L-29 in the preparation of compost products.

[0014] Furthermore, the compost product is prepared by the following method: Bacillus belye L-29 is inoculated into the organic material after primary fermentation, and a secondary fermentation is carried out, with an inoculation amount of 1×10⁻⁶. 5 ~1×10 6 CFU / g wet material, then cooled and cured.

[0015] The present invention also provides a compost product containing Bacillus belye L-29.

[0016] The present invention also provides the application of the aforementioned Bacillus belyss L-29 in promoting plant growth and / or enhancing plant disease resistance.

[0017] The present invention also provides the application of the compost product in promoting plant growth and / or enhancing plant disease resistance.

[0018] The advantages and positive effects of the stress-resistant Bacillus belyssus L-29 strain and its application described in this invention are as follows: (1) The Bacillus belye L-29 of this invention was isolated from saline-alkali soil. It has strong environmental adaptability and a certain degree of tolerance to salt, pH and drought. It can survive and proliferate in extreme environments with pH 2~12, salt concentration of 15‰ and severe drought conditions simulated by 0~25% PEG6000. It can be applied directly to the soil or with organic fertilizer, soil conditioner, etc., overcoming the problem that ordinary microbial strains are difficult to survive in saline-alkali soil. Acid tolerance: 18 times proliferation at pH=2, 38 times proliferation at pH=4; Alkali tolerance: 48 times proliferation at pH=10, 24 times proliferation at pH=12; Salt tolerance: Tolerates NaCl, Na2SO4 and Na2CO3 above 15‰, and NaCl and Na2SO4 concentrations below 15‰ have no significant effect on the proliferation of this strain; Drought tolerance: Tolerates 0~25% PEG6000 and can proliferate 200 times.

[0019] (2) The Bacillus berberis L-29 of the present invention can secrete IAA, produce high levels of protease and amylase, and has a good ability to decompose cellulose and effectively dissolve organic phosphorus. Protease and amylase can help nitrogen conversion and carbon source supply, improve the decomposition of organic matter in saline-alkali land, and phospholysin can enhance phosphorus availability and directly promote plant growth.

[0020] (3) The Bacillus berberis L-29 of the present invention can maintain a high colonization rate in the later stage of composting, so that the final product has stable functionality.

[0021] (4) The Bacillus berberis L-29 of the present invention has both soil improvement and disease resistance and growth promotion effects, and can realize the integrated function of "promoting decomposition-soil improvement-growth promotion". Moreover, the process is simple, the cost is low, and it is suitable for large-scale promotion.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 These are the results of colony morphology observation of the strain in LB medium; Figure 2 It is the result of Gram staining; Figure 3This shows the growth of the strains under NaCl stress, where A represents the growth morphology of the strains at different NaCl concentrations, and B represents the proliferation rate of the strains at different NaCl concentrations. Figure 4 This shows the growth of the strain under Na2SO4 stress, where A represents the growth morphology of the strain under different Na2SO4 concentrations, and B represents the proliferation rate of the strain under different Na2SO4 concentrations. Figure 5 This shows the growth of the strain under Na2CO3 stress, where A represents the growth morphology of the strain under different Na2CO3 concentrations, and B represents the proliferation rate of the strain under different Na2CO3 concentrations. Figure 6 This shows the growth of the strain under drought stress simulated by PEG 6000. In this case, A represents the growth morphology of the strain under different drought conditions, and B represents the proliferation rate of the strain under different drought conditions. Figure 7 The values ​​represent the proliferation rates under different pH conditions, where A represents the growth morphology of the strain under different pH conditions, and B represents the proliferation rate of the strain under different pH conditions. Figure 8 These are the results of observations on enzyme production characteristics; Figure 9 These are the results of the pathogen antagonism experiment. Figure 10 This describes the temperature changes during different treatments in the secondary fermentation process. Figure 11 It refers to the humus content of different treatments at the end of fermentation; Figure 12 This describes the colonization status of L-29 cells after fermentation in the inoculated group. Figure 13 This shows the growth of Chinese cabbage under different treatments. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. Experimental instruments, equipment, and reagents in the following embodiments that do not specify their sources are all commercially available materials.

[0026] Unless otherwise defined or stated, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the methods of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0027] Bacillus belyes L-29 is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35587, on August 12, 2025, at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0028] Example 1: Screening and Identification of Strains: 1. Source and isolation of strains: (1) Sample collection: Saline-alkali soil samples were collected from the comprehensive demonstration base of saline-alkali land at Shangzhuang Experimental Station of China Agricultural University in Beijing for later use.

[0029] (2) Culture medium preparation: LB medium: 10 g / L tryptone, 5 g / L yeast extract, 10 g / L sodium chloride, 15 g / L agar, pH adjusted to 7.0. PDA medium: Peel potatoes, cut 200 g into small pieces, boil in water for 30 min, filter through 4 layers of gauze, add 20 g glucose, 17 g agar, and distilled water to a final volume of 1000 mL, boil and mix well.

[0030] (3) Isolation and purification of the strain: The strain was isolated using the dilution plate method, and the specific operation method is as follows. Weigh 100g of soil sample and put it into 900mL of sterile water and shake well to obtain 10 -1 A bacterial suspension with a concentration of g / mL was diluted to 10. -2 g / mL, 10 -3 g / mL and 10 -4 The bacterial suspension (g / mL) was spread onto PDA plates, dried, and then incubated upside down in a 30℃ incubator for 5-7 days. Single colonies resembling bacteria were picked and transferred to LB plates for purification and culture. After preliminary identification as bacteria by microscopic examination, they were transferred to LB slant plates for further culture. After successful growth, the colonies underwent natural mutagenesis and were then stored in a refrigerator.

[0031] 2. Strain identification: (1) Morphological identification: The strain was inoculated on LB medium and incubated at 37°C to observe the colony morphology, such as... Figure 1 As shown. The results indicated that on LB medium, the colonies of this strain were milky white, slightly irregularly round, with intact edges, medium size, slightly raised, and a sunken, opaque center. This strain was Gram-positive, appearing as rod-shaped cells under a microscope, arranged in pairs, and producing spores, as shown. Figure 2 As shown.

[0032] Example 2: Functional verification of the strain: 1. Stress tolerance verification: Single-factor stress experiment was used to evaluate the proliferation ability of the strain in extreme environments by plate counting method.

[0033] (1) Acid and alkali resistance verification: Bacillus belye L-29 was inoculated into a 100 mL sterile Erlenmeyer flask of LB broth and incubated overnight at 37°C with shaking. An appropriate amount of the overnight culture was transferred to fresh LB broth for secondary culture and incubated at 37°C with shaking for 24 h until mid-log growth (at this stage, the bacterial cells have uniform viability and are sensitive to stress).

[0034] Prepare and autoclave culture media covering the target pH range in advance. Adjust the pH of LB medium to 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0. For the acidic range (pH 2.0–6.0), use 0.1 mol / L H₂SO₄ for adjustment, and for the alkaline range (pH 8.0–12.0), use 0.1 mol / L NaOH for adjustment. Dispense each treatment medium into 100 mL Erlenmeyer flasks, with three replicates per treatment.

[0035] Take 3 mL of culture and inoculate it into different treatment media, then immediately collect the bacterial cells. Take 100 μL of culture and perform a 10-fold serial dilution, selecting an appropriate dilution (usually so that the final plate colony count is between 30-300) and spread it on LB agar plates, with at least two plates for each dilution. The results of counting these plates after incubation are the initial viable cell concentration before stress (T0 CFU / mL).

[0036] Each treatment was incubated at 37℃ and 120 rpm in a shaker. After 24 hours, 100 μL of the culture was serially diluted 10-fold. The appropriate dilution was then plated onto LB agar plates, and plate counts were performed to calculate the viability. The results of these plate counts after incubation were taken as the initial viable cell concentration after stress (T1 CFU / mL).

[0037] Proliferation rate (%) = (T1-T0) / T0×100%.

[0038] Proliferation rate under different pH conditions, such as Figure 7 As shown.

[0039] The results of the strains' acid and alkali resistance are shown in Table 1: Table 1. Determination of the acid and alkali resistance of the strains

[0040] (2) Salt tolerance verification: The bacterial culture preparation stage was the same as the acid and alkali tolerance verification stage. For the salt stress treatment, pre-prepared and autoclaved culture media covering the target pH range were used. Na₂SO₄, NaCl, and Na₂CO₃ were added to LB medium to concentrations of 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 1.0%, 1.3%, and 1.5%, respectively. A control without inoculation was used. Each treatment medium was aliquoted into Erlenmeyer flasks, 100 mL per flask, with three replicates per treatment. Subsequent culture and treatments were the same as in the acid and alkali tolerance verification stage. Under NaCl stress, the growth of the strain was as follows... Figure 3 As shown; the growth of the strain under Na2SO4 stress is as follows. Figure 4 As shown; the growth of the strain under Na2CO3 stress is as follows. Figure 5 As shown.

[0041] The results of the salt tolerance test of the strains are shown in Table 2: Table 2. Determination of salt tolerance of strains

[0042] (3) Drought resistance verification: The bacterial culture preparation stage was the same as the acid and alkali tolerance verification stage. For the drought stress treatment, pre-prepared and autoclaved culture media covering the target pH range were used. PEG 6000 was added to LB medium at concentrations of 5%, 10%, 15%, 20%, and 25%, with a control of no inoculation. Each treatment medium was aliquoted into Erlenmeyer flasks, 100 mL per flask, with three replicates per treatment. Subsequent culture and treatment were the same as the acid and alkali tolerance verification stage. The growth of the strains under PEG 6000-simulated drought stress was as follows... Figure 6 As shown.

[0043] The results of the drought resistance test of the strains are shown in Table 3: Table 3. Determination of drought resistance of strains

[0044] The results showed that the strain could proliferate 18-fold at pH=2, 38-fold at pH=4, 48-fold at pH=10, and 24-fold at pH=12; it was tolerant to NaCl, Na2SO4 and Na2CO3 concentrations up to 15‰, and the concentrations of NaCl and Na2SO4 up to 15‰ had no significant effect on the proliferation of the strain; it was also tolerant to 0-25% PEG6000 and could proliferate 200-fold.

[0045] 2. Functional characteristic verification: The diameter of the transparent ring was measured using the transparent ring method.

[0046] (1) Detection of cellulase: The activated strain was inoculated onto a cellulose Congo red agar plate and incubated at 30℃. The formation of a red hydrolysis zone around the colony was observed. The presence of a red hydrolysis zone indicates the production of cellulase. Cellulose Congo red agar (cellulase detection medium): MgSO4·7H2O 0.25g / L, K2HPO4 0.5g / L, cellulose 1.88g / L, Congo red 0.2g / L, agar 15.0g / L, gelatin 2.0g / L.

[0047] (2) Detection of amylase: The activated strain was inoculated onto a culture medium plate and incubated at 37°C for 24 hours. Then, an appropriate amount of Lugol's iodine solution was added to the surface of the medium to ensure even and complete coverage of the entire plate. A clear hydrolysis zone around the colony against a purple background indicates that the bacterium produces amylase. Amylase detection medium: 5 g / L soluble starch, 5 g / L sodium chloride. All components except agar were dissolved in distilled water, the pH was adjusted, and 2% agar was added.

[0048] (3) Protease detection: The activated strain was punctured and inoculated onto protease detection medium plates. One strain was inoculated on each plate, with three replicates. After incubation at 37°C for 24 hours, the presence of a clear zone around the colony was observed. The presence of a clear zone indicates that the strain can produce protease. Protease detection medium: peptone 5.0 g / L, yeast extract 3.0 g / L, glucose 1.0 g / L, skim milk 100 mL / L, agar 15.0 g / L.

[0049] (4) Detection of lysozyme: The activated strains were punctured and inoculated onto lysozyme detection medium plates. Three strains were inoculated onto each plate, and three replicates were set up for each type of lysozyme plate. After incubation at 30℃ for 3 days, the lysozyme situation was observed, and the diameter of the lysozyme zone was counted. Lysozyme detection medium: glucose 10g / L, (NH4)2SO4 0.5g / L, NaCl 0.3g / L, MgSO4 0.3g / L, MnSO4 0.3g / L, FeSO4 0.03g / L, K2SO4 0.3g / L, Ca3(PO4)2 5g / L, agar 15.0g / L, pH 7.0.

[0050] The results showed that the strain produced high levels of protease and amylase, exhibited excellent cellulose-degrading ability, and could also effectively dissolve organic phosphorus compounds, such as... Figure 8 As shown.

[0051] (5) Verification of biocontrol efficacy: The plate confrontation method was used to study the effect of biocontrol on Fusarium oxysporum (Fusarium oxysporum) Fusarium oxysporum ), Alternaria brassicae ( Alternaria brassicae Rhizoctonia solani ( ), Rhizoctonia solani Rhizoctonia solaniTo investigate the antagonistic effect of Bacillus vesiculosus L-29 on these three pathogens, the antibacterial effect was precisely determined on PDA medium. The inoculation point between the strain and the pathogen was 2 cm apart, and the antibacterial effect was observed after culturing at 27°C for 72 hours.

[0052] The results showed that *Bacillus belye* L-29 had inhibitory effects on three pathogens: *Fusarium oxysporum*, *Alternaria brassicae*, and *Rhizoctonia solani*, with inhibition zone diameters of 35 mm, 42 mm, and 32 mm, respectively. Figure 9 As shown.

[0053] 3. Fermentation test to promote saponification by strains: Based on practical experience in organic fertilizer production, livestock and poultry manure is classified into primary fermentation (high-temperature fermentation with forced ventilation) and secondary fermentation (aging stage under natural ventilation conditions). The Bacillus berberis L-29 bacterial solution is thoroughly mixed with the material after the primary fermentation for secondary fermentation.

[0054] Control group (CK): No bacteria added; Group 1: Bacillus belye L-29 1×10 5 CFU / g wet material; Group 2: Bacillus belye L-29 5×10 5 CFU / g wet material; Group 3: Bacillus belyceta var. var. L-29 1×10 6 CFU / g wet material; In the inoculation group, Bacillus vesiculosus L-29 fermentation broth was evenly applied while turning the compost pile; in the control group, only an equal volume of sterile water was added. The secondary fermentation stage was maintained for 8–20 days, with a moisture content of 50–55% and a temperature of 45–55°C, followed by a cooling and maturation stage. Samples were taken evenly during the fermentation process, and samples were collected on days 1, 2, 3, 4, 7, 10, 14, and at the end of maturation to monitor temperature changes and humic content.

[0055] The results showed that all inoculated groups exhibited better heating effects and higher product humus content compared to the control group. Inoculation group 3 showed the best results. Figure 10 , Figure 11 As shown.

[0056] After the composting process was completed in inoculation groups 1, 2, and 3, compost samples were collected, serially diluted, and spread onto nutrient agar plates. After incubation at 37°C for 24 hours, the samples were counted, and the results showed a concentration of 1.8 × 10⁻⁶. 7 CFU / g, 2.5×10 7 CFU / g, 3.8×10 7 L-29 with CFU / g, such as Figure 12As shown, this demonstrates that L-29 has good colonization ability and stability in the complex environment of composting.

[0057] 4. Potted plant verification experiment: (1) Experimental Design: To further verify the farmland application effect of L-29 compost, farmland loam was selected as the experimental substrate, and Chinese cabbage was cultivated as the test crop. The experiment was set up with 3 groups: CK: Blank control, no fertilizer applied; T1: Treatment with L-29 bacterial agent alone, bacterial concentration of 1×10⁻⁶ 9 CFU / mL; T2: Composting product treatment containing L-29; The pot experiment was conducted under artificial climate conditions, maintaining suitable temperature and light. The germination rate was recorded on day 7, and plant height and root length were measured on day 28. Disease occurrence was also investigated.

[0058] (2) Detection indicators: Emergence rate % = Number of seedlings / Number of seeds × 100; Plant height: At the end of cultivation, remove the cabbage whole, carefully rinse off the soil adhering to the roots, stems and leaves, and absorb any remaining moisture with absorbent paper. Place the cabbage flat on the work surface, use a ruler to measure and record the length of the plant from the root zone to the tip of the top leaf.

[0059] Root length: Straighten the root system with tweezers, select the longest taproot and measure the root length with a ruler.

[0060] The experimental results are shown in Table 4: Table 4. Germination rate and average plant height under different pH and salinity treatments 21 days after planting

[0061] The results showed that application of compost containing L-29 significantly promoted crop plant height and biomass, and significantly reduced disease incidence. Compared with conventional compost, the L-29-containing compost treatment showed more significant growth-promoting and disease-resistant effects, proving that this strain still has excellent application effects in normal soil. Emergence rate increased by 214.3%, average plant height increased by 34.9%, and average root length increased by 61.7%. Figure 13 As shown.

[0062] Therefore, the stress-resistant Bacillus belyceae L-29 provided by this invention addresses the problems of poor stress resistance and limited functionality of existing microbial strains. It exhibits superior stress resistance, adapting to various extreme environments. It can survive and proliferate under extreme conditions simulating drought (pH 2-12, 15‰ salt concentration, 0-25% PEG 6000). Simultaneously, it possesses multiple functions including soil improvement (organic matter decomposition, phosphorus activation), plant growth promotion, and broad-spectrum disease control. Furthermore, it significantly promotes humus generation and accelerates compost maturation during the secondary fermentation stage, demonstrating excellent colonization ability. When applied to normal soil, the resulting compost product improves nutrient availability, promotes crop growth, and enhances disease resistance.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A stress-tolerant Bacillus velezensis L-29, characterized in that, The bacillus velezensis (Bacillus velezensis) Bacillus velezensis L-29 is preserved in China General Microbiological Culture Collection Center, and the preservation number is CGMCC No. 35587, the preservation time is August 12, 2025, and the preservation address is No. 3, Xili, Beichen, Chaoyang District, Beijing.

2. B. velezensis L-29 according to claim 1, characterized in that, has the following stress resistance: acid and alkali resistance: survive and proliferate in the environment of pH 2~12; salt resistance: survive and proliferate in the environment of 15‰ concentration of NaCl, Na2SO4 or Na2CO3; drought resistance: survive and proliferate in the drought environment simulated by 0~25% PEG6000.

3. The B. velezensis L-29 of claim 1, characterized in that, The Bacillus velezensis L-29 can secrete indole-3-acetic acid and has the ability to produce protease, amylase, cellulase and phosphorus-dissolving enzyme.

4. The B. velezensis L-29 of claim 1, characterized in that, The Bacillus velezensis L-29 has antagonistic effect on Fusarium oxysporum, Alternaria brassicae and Rhizoctonia solani.

5. Use of the Bacillus velezensis L-29 according to any one of claims 1-4 in the preparation of a compost product.

6. Use according to claim 5, characterized in that, The compost product is prepared by inoculating Bacillus velezensis L-29 into the organic material after the first fermentation, carrying out the second fermentation, the inoculation amount is 1 x 10 5 ~1 x 10 6 CFU / g of wet material, and then cooling and curing.

7. A compost product characterised in that, The compost product contains the Bacillus velezensis L-29.

8. Use of the Bacillus velezensis L-29 according to any one of claims 1-4 in promoting plant growth and / or enhancing plant disease resistance.

9. Use of the compost product according to claim 7 in promoting plant growth and / or enhancing plant disease resistance.

Images