Application of Bacillus subtilis to enhance the use of black soldier flies in treating livestock and poultry manure and kitchen waste

Abstract

The invention discloses the application of Bacillus subtilis to enhance the treatment of livestock and poultry feces and kitchen waste by black soldier flies, and relates to the field of biological strain utilization and development technology. Bacillus subtilis SJM1732 has been deposited in the General Microbiological Center of China Microbiological Culture Collection Committee on September 17, 2019, and is classified and named Bacillus subtilis SJM1732, with a deposit number of CGMCC No.18496, and a deposit address of Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing. The Bacillus subtilis SJM1732 disclosed in the invention has the characteristics of antibacterial, deodorizing, reducing the mortality rate of black soldier flies, and improving the activity of digestive tract enzymes of black soldier flies, and has a significant effect in enhancing the treatment of livestock and poultry feces and kitchen waste by black soldier flies.

Description

Technical Field

[0001] The invention relates to the technical field of biological strain utilization and development, in particular to the application of Bacillus subtilis in enhancing black soldier flies to treat livestock and poultry excrement and restaurant kitchen waste. Background Art

[0002] The production of organic solid waste is large and difficult to treat, especially livestock and poultry manure and kitchen waste. my country produces about 3.8 billion tons of livestock and poultry manure every year, and the effective utilization rate is less than 60%. Livestock and poultry manure has become the main source of pollution in rural areas and around farms, leading to frequent soil-borne pests and diseases, causing eutrophication of water bodies, producing a large amount of foul-smelling gases, breeding pathogens, and seriously threatening public health safety. Biogas fermentation is one of the effective means of treating livestock manure. At present, biogas projects have been widely used in livestock manure treatment, but its byproduct biogas liquid can easily become a secondary pollution source. If there is not enough land around to absorb it, it is difficult for biogas projects to make a profit. In addition, manure, straw, etc. can also be used to produce organic fertilizer after aerobic composting and fermentation, but traditional composting fermentation management is extensive, the cycle is long, the nutrient loss is large, and the fertilizer efficiency is low. The stench during the composting process can easily lead to environmental pollution, and the use of turners, aeration pipes, odor collection systems, etc. will greatly increase the costs of land, factory buildings, equipment, and energy. Food waste also faces a similar dilemma. Traditional treatment methods such as incineration and landfill, composting and biogas fermentation still dominate, which easily regenerates waste residue, wastewater and waste gas.

[0003] In recent years, the method of treating organic solid waste with insects has received widespread attention. Black soldier flies (Hermetia illucens L.) are saprophytic insects. The larvae have the advantages of omnivorous diet, large appetite, strong stress resistance, no disease transmission, rapid reproduction, large biomass, high absorption conversion rate, easy management, and low feeding cost. They can feed on livestock and poultry manure and food waste to produce high-value animal protein feed. In October 2013, the Food and Agriculture Organization of the United Nations listed black soldier flies as the most important protein feed alternative insect in the "Edible Insects Report". Black soldier flies have become a resource insect with the same reputation as maggots, mealworms, and barley worms, and have been promoted worldwide. Black soldier flies are currently widely distributed in Guizhou, Guangxi, Guangdong, Shanghai, Yunnan, Taiwan, Hunan, Hubei and other places in my country, and are widely used to treat livestock and poultry manure and food waste. Studies have shown that black soldier flies can efficiently remove nitrogen, phosphorus and potassium from organic solid waste, kill pathogens, and reduce accumulation. However, organic solid waste needs to undergo microbial fermentation before it can be used for black soldier fly treatment. Selecting suitable microbial strains will help improve the subsequent black soldier fly treatment effect. Otherwise, organic solid waste is prone to produce odor and will also cause a large number of black soldier flies to die.

[0004] Bacillus subtilis is a Gram-positive bacterium widely found in the natural environment. It has no capsule, flagella around it, can move, has spores, can withstand acid, salt, high temperature, and extrusion. It also has strong resistance to adversity, has no resistance to antibiotics, is non-toxic to humans and animals, and does not pollute the environment. As a feed additive, it can produce a variety of antibiotics and enzymes after entering the animal body, which not only has the effects of improving production performance and enhancing immunity, but also can oxidize odor-source indole compounds into odorless and non-toxic substances, thereby reducing the content of harmful gases in the intestine and excrement. However, most of Bacillus subtilis is isolated from soil, and the effect is not significant in the black soldier fly treatment system. The reason may be that it forms a competitive relationship with the intestinal flora of black soldier flies, and it is difficult to multiply in large quantities to form a population advantage in the process of black soldier flies treating organic solid waste, which limits the play of its role. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the Bacillus subtilis strain of the present invention has the characteristics of antibacterial, deodorizing, reducing the mortality rate of black soldier flies, and improving the activity of digestive tract enzymes of black soldier flies, and has a significant application effect in enhancing the use of black soldier flies to treat livestock and poultry manure and kitchen waste.

[0006] Technical solution: To achieve the above-mentioned purpose, the present invention provides a Bacillus subtilis SJM1732, which is isolated from the intestine of black soldier flies and has been deposited in the General Microbiological Center of China Microorganism Culture Collection Administration on September 17, 2019, and is classified and named Bacillus subtilis SJM1732, with a deposit number of CGMCC No.18496; the 16SrRNA gene sequence of the strain is shown in SEQ ID NO:1.

[0007] A bacterial agent, comprising the above-mentioned Bacillus subtilis SJM1732.

[0008] A method for preparing the bacterial agent comprises the following steps:

[0009] S1. Strain activation: Pick Bacillus subtilis SJM1732 strain and inoculate it onto solid slant medium, and culture it in a constant temperature incubator at 28-37°C for 24-48h;

[0010] S2. Preparation of liquid seeds: inoculate the activated Bacillus subtilis SJM1732 in step S1 into a container containing liquid seed culture medium, seal the container with gauze, and culture under shaking conditions of 28-37° C. and 160-220 r / min for 24-48 h to obtain liquid seeds;

[0011] S3, liquid fermentation: the liquid seeds prepared in step S2 are inoculated into the fermentation medium at a volume ratio of 1-10%, the rotation speed is 200-700 r / min, the dissolved oxygen is controlled at 20-40%, the pH is 6.0-7.5, the temperature is 28-37° C., and the 10L fermenter is aerated and cultured for 24-48 hours to obtain a liquid bacterial agent of Bacillus subtilis SJM1732.

[0012] Furthermore, the bacterial agent can be concentrated to form a liquid bacterial agent or freeze-dried to form a solid bacterial powder, and the amount of live bacteria of Bacillus subtilis SJM1732 in the bacterial agent is not less than 10 8 cfu / mL or 10 8 cfu / g.

[0013] Furthermore, the solid slant culture medium is: 1-5 g / L glucose, 3-7 g / L yeast extract, 5-15 g / L peptone, 3-7 g / L NaCl, 15-20 g / L agar, dissolved in distilled water to 1 L, pH 7.0-7.2, and sterilized by high-pressure steam at 121°C for 15-20 min.

[0014] Furthermore, the liquid seed culture medium is: glucose 5-15 g / L, beef extract 1-5 g / L, yeast extract powder 3-7 g / L, KH2PO4 0.5-2.0 g / L, MgSO4·7H2O 0.1-1.0 g / L, CaCl2·2H2O0.1-0.5 g / L, (NH4)2SO4 1-5 g / L, dissolved in distilled water to 1 L, pH 7.0-7.2, and sterilized by high-pressure steam at 121°C for 15-20 min.

[0015] Furthermore, the fermentation medium is: glucose 10-30 g / L, beef extract 1-5 g / L, yeast extract powder 0.5-2.0 g / L, KH2PO4 0.5-2.0 g / L, MgSO4·7H2O 0.2-0.6 g / L, CaCl2·2H2O0.1-0.5 g / L, ammonium citrate 1-5 g / L, corn steep liquor 5-15 g / L, FeSO4 0.5-2.0 mg / L, vitamin B1 1-3 mg / L, dissolved in distilled water to 1 L, pH 7.0-7.2, and sterilized by high-pressure steam at 121°C for 15-20 min.

[0016] The bacterial agent is used to enhance the ability of black soldier flies to treat livestock and poultry excrement and restaurant kitchen waste.

[0017] The application of the Bacillus subtilis of the present invention to enhance the use of black soldier flies in treating livestock and poultry excrement and food waste has at least the following technical effects:

[0018] (1) The Bacillus subtilis SJM1732 (CGMCC NO.18496) in the present invention is isolated from the intestine of black soldier flies, has the biological characteristics of being Gram-positive, antagonistic to multiple pathogens, and capable of fixing nitrogen and desulfurizing. It has the advantages of fast growth rate, high fermentation density, broad-spectrum antibacterial activity, strong tolerance to adverse environments, and rich digestive enzyme system.

[0019] (2) The Bacillus subtilis SJM1732 (CGMCC NO.18496) in the present invention can be used for deodorizing livestock and poultry manure, effectively reducing the release of malodorous gases and volatile organic compounds in livestock and poultry manure, and reducing the generation of odor from the source.

[0020] (3) The Bacillus subtilis SJM1732 (CGMCC NO.18496) in the present invention can be applied to the treatment of livestock and poultry manure and food waste by black soldier flies, and can stably colonize in the system of livestock and poultry manure and food waste by black soldier flies for a long time and play the role of degrading organic matter, inhibiting pathogens, and reducing the generation and release of odor, thereby achieving the purpose of accelerating the reduction of livestock and poultry manure and food waste and reducing waste gas emissions. By increasing the diversity of intestinal flora of black soldier flies and amylase, protease and lipase, the mortality rate of black soldier flies is reduced, the growth rate of black soldier flies is increased, and the prepupa time of black soldier flies is shortened.

[0021] (4) The Bacillus subtilis SJM1732 (CGMCC NO.18496) in the present invention has the characteristics of simple and efficient preparation process, stable and reliable products, and has obvious technical advantages of being easy to commercialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the colony morphology of Bacillus subtilis SJM1732;

[0023] Figure 2 This is the microscopic morphology of Bacillus subtilis SJM1732;

[0024] Figure 3 This is an electron microscope photo of Bacillus subtilis SJM1732;

[0025] Figure 4 This is the phylogenetic tree of Bacillus subtilis SJM1732 based on 16S rRNA sequence;

[0026] Figure 5 The invention relates to treating pig manure by combining a bacterial agent containing Bacillus subtilis SJM1732 with black soldier flies. DETAILED DESCRIPTION

[0027] The following combination Figures 1 to 5 The principles and features of the present invention are described, and the examples given are only used to explain the present invention, rather than to limit the scope of the present invention.

[0028] Example 1: Isolation and screening of Bacillus subtilis SJM1732 (CGMCC NO.18496).

[0029] 1. Enrichment: Take 20 to 30 black soldier fly larvae, rinse and disinfect them with alcohol and saline, dissect the intestines, grind them in a sterilized mortar, add an appropriate amount of sterile water to make a bacterial suspension. Take 0.5 ml of the bacterial suspension from the mortar and inoculate it into a triangular flask containing 100 mL of liquid enrichment culture medium. Incubate it at 30°C and 220 r / min for 5 days, then transfer the culture medium to 100 mL of fresh liquid enrichment culture medium at a 10% inoculation rate. Repeat 5 times. Take 1 mL of the culture medium for dilution and take 10 -3 , 10 -4 , 10 -5 , 10 -6 Four gradients, two parallels for each gradient, were spread on solid enrichment medium plates and cultured at 30°C for 48 hours. Single colonies were picked from the plates for microscopic examination, their morphology was recorded, and single colonies with different characteristics were transferred to the slant, cultured for 48 hours, and stored at 4°C for later use.

[0030] The components and contents of 1L enrichment medium are: glucose 10g, (NH4)2SO4 2g, NaCl 1g, MgSO4·7H2O 1g, K2HPO4·2H2O 1g, FeSO4·7H2O 0.4g, mother solution 1mL, of which the mother solution (1L) is: EDTA 10g, ZnSO4 1.2g, CaCl2 1.5g, MgCl2·4H2O 1g, (NH4)6Mo7O 24 ·4H2O 1g, CuSO4·5H2O 1g, CoCl2·6H2O1g.

[0031] 2. Preliminary screening: All the isolated bacterial strains were inoculated in the corresponding liquid culture medium respectively. After 5 days of shaking culture at 30 ℃ and 220 r / min, the culture solution was inoculated into a plastic box equipped with 200 g of fresh chicken manure at 5% inoculum size (10 mL). The control group added an equal amount of sterilized water, mixed with the chicken manure and sealed, and cultured at 30 ℃ for 7 days. The deodorizing effect was judged by sensory method and the odor grade was divided into 5 grades according to non-smelly "M0", slightly smelly "M1", relatively smelly "M2", very smelly "M3" and foul-smelling "M4", and the bacterial strain with obvious deodorizing effect (the effect reached non-smelly "M0" and slightly smelly "M1") was subjected to a multiple screening test.

[0032] 3. Rescreening: Weigh 200g of fresh chicken manure and place it in a plastic box. Inoculate it with 5% inoculation (10mL) of the primary screening strain culture solution, mix it thoroughly, and use fresh chicken manure with an equal amount of sterile water as a blank control. Set up 3 parallels for each strain. Place a 50mL small beaker containing 20mL of 2% boric acid solution in the plastic box to absorb ammonia. Seal the plastic box and culture it at 30℃. Determine the release of ammonia by acid-base titration, and repeat the test 3 times for each group. Perform differential analysis with the blank control group, calculate the removal rate of ammonia, and select the strain with the best deodorization effect for purification, culture and preservation.

[0033] Ammonia removal rate calculation formula: Ammonia removal rate = difference between ammonia release in the blank control group and ammonia release in the test group / ammonia release in the blank control group × 100%. Through screening work, a strain SJM1732 derived from the intestine of black soldier flies was obtained that can significantly deammonify and deodorize.

[0034] Example 2: Identification of Bacillus subtilis SJM1732 (CGMCC NO.18496).

[0035] 1. Morphological characteristics and physiological and biochemical characteristics

[0036] After culturing strain SJM1732 on LB medium for 48 hours, the colony color is milky white, with irregular edges and diffusion, and the colony surface is rough, opaque, wrinkled and sticky. Gram staining is positive, the bacteria are rod-shaped, blunt at both ends, of varying lengths, without capsules, and can form endospores. The spores are oval, mesogenic or sub-terminal, with flagella around the peritrichous, and motile. Identified by the VITEK2 Compact fully automatic microbial analysis system, strain SJM1732 can grow in 6.5% sodium chloride, can utilize multiple carbon sources such as D-ribose, D-mannose, D-glucose, maltotriose, and ancient sugar, and β-mannosidase, N-acetyl-β-D-glucosaminidase, and kanamycin tolerance are all negative. The LB medium components are: yeast extract 5 g / L, tryptone 10 g / L, NaCl 10 g / L, agar 18 g / L, pH 7.2, and high-pressure steam sterilization at 121°C for 20 min.

[0037] The colony morphology of strain SJM1732 is as follows Figure 1 As shown, the microscopic morphology Figure 2 As shown in the electron microscope photos Figure 3 The physiological and biochemical identification results of strain SJM1732 are shown in Table 1.

[0038] Table 1 Physiological and biochemical identification results of strain SJM1732

[0039]

[0040]

[0041] Note: "+" indicates a positive reaction, "-" indicates a negative reaction

[0042] 2. Phylogenetic analysis

[0043] After DNA extraction and electrophoresis detection, strain SJM1732 was amplified and sequenced by PCR. The length of the sequencing product was 1455 bp. The sequencing results were compared by BLAST on NCBI. The homology was compared using MEGA7.0 software. Gene sequences with close homology were selected to construct a phylogenetic tree. The phylogenetic tree based on 16SrRNA sequence is shown in Figure 4 The homology between strain SJM1732 and Bacillus subtilis was 99.8%. Combined with the results of morphological identification and physiological and biochemical identification, strain SJM1732 was finally determined to be Bacillus subtilis.

[0044] 3. Genetic stability

[0045] The strain SJM1732 was subcultured 50 times on solid slant medium by streaking method. The bacterial morphology, growth rate and ability to remove ammonia were measured. There was no significant difference with the original strain and the genetic stability was good.

[0046] 4. The strain was deposited in the General Microbiology Center of China Microbiological Culture Collection on September 17, 2019, and the classification name is Bacillus subtilis SJM1732, the deposit number is CGMCC No.18496, and the deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0047] The 16S rRNA sequence of the Bacillus subtilis SJM1732 is:

[0048]

[0049] Example 3: A method for preparing a bacterial agent containing Bacillus subtilis SJM1732.

[0050] Specifically, the preparation method of the bacterial agent is:

[0051] S1. Strain activation: Pick the strain and streak it onto the solid slant medium, and culture it in a constant temperature incubator at 30°C for 48 hours. When a large number of bacterial cells grow on the slant, they can be used to transfer liquid seeds;

[0052] The solid slant culture medium is composed of 5 g / L glucose, 5 g / L yeast extract powder, 10 g / L peptone, 5 g / L NaCl, and 18 g / L agar, which are dissolved in distilled water to a volume of 1 L, pH 7.0, and sterilized by high-pressure steam at 121° C. for 20 min.

[0053] S2. Preparation of liquid seeds: Select the activated strain and inoculate it into a container filled with seed culture medium, seal it with eight layers of gauze, and culture it in a shaking incubator at 30°C and 220 rpm for 28 hours until a large number of bacteria grow to obtain liquid seeds;

[0054] The liquid seed culture medium is glucose 10g / L, beef extract 3g / L, yeast extract 5g / L, KH2PO4 1g / L, MgSO4·7H2O 0.5g / L, CaCl2·2H2O 0.3g / L, (NH4)2SO4 3g / L, dissolved in distilled water to 1L, pH 7.0, and sterilized by high pressure steam at 121°C for 20min. ;

[0055] S3, liquid fermentation: inoculate the liquid seeds prepared in step 2 into the fermentation medium at a volume ratio of 5%, rotate at 200-700 r / min, control the dissolved oxygen at 30%, pH 7.0, temperature at 30°C, and culture with aeration for 36 h.

[0056] The fermentation medium comprises 20 g / L glucose, 3 g / L beef extract, 1 g / L yeast extract powder, 1 g / L KH2PO4, 0.4 g / L MgSO4·7H2O, 0.2 g / L CaCl2·2H2O, 3 g / L ammonium citrate, 10 g / L corn steep liquor, 1 mg / L FeSO4, and 2 mg / L vitamin B1, which is dissolved in distilled water to a fixed volume of 1 L, pH value is 7.0, and high-pressure steam sterilization is performed at 121° C. for 20 min.

[0057] When used, the bacterial agent can be concentrated into a liquid bacterial agent or freeze-dried into a solid bacterial powder as needed, and the amount of live bacteria of Bacillus subtilis SJM1732 in the bacterial agent is not less than 1×10 8 cfu / mL or 10 8 cfu / g.

[0058] Example 4: Application of a bacterial agent containing Bacillus subtilis SJM1732 in enhancing the treatment of livestock and poultry manure by black soldier flies.

[0059] The moisture content of chicken manure was adjusted to 70% with sawdust as auxiliary material, and the material was evenly divided into 2 portions, each with 1 kg, which were recorded as group A and group B. Group A was not added with a bacterial solution containing Bacillus subtilis SJM1732, and 3000 third-instar larvae of black soldier flies were inoculated; Group B was inoculated with 10 mL of a bacterial solution containing Bacillus subtilis SJM1732 and mixed evenly, and the amount of live bacteria of Bacillus subtilis SJM1732 in the bacterial agent was not less than 1×10 8 cfu / mL, and then 3000 black soldier fly 3rd instar larvae were inoculated. Both groups were treated under natural light, ventilation and 30℃ for 3 days, and the material absorption, moisture content and pH value were tested, the weight and length of black soldier fly larvae were measured, and the ammonia release was detected by boric acid absorption titration. The results are shown in Table 2. The material absorption of the experimental group (group B) was 16% higher than that of the control group (group A), the weight and length of black soldier fly larvae were significantly increased, and the ammonia release was reduced by 84%.

[0060] Table 2 Effect of the bacterial agent containing Bacillus subtilis SJM1732 on the treatment of livestock and poultry manure by black soldier flies

[0061]

[0062]

[0063] Example 5: Application of a bacterial agent containing Bacillus subtilis SJM1732 in enhancing the ability of black soldier flies to treat kitchen waste.

[0064] The kitchen waste was crushed and pulped, and sawdust was used as an auxiliary material to adjust the moisture content of the material to 70%. The material was evenly divided into two portions, each with 1 kg, and recorded as Group A and Group B. Group A was not added with a bacterial solution containing Bacillus subtilis SJM1732, and 3,000 third-instar black soldier flies were inoculated; Group B was inoculated with 10 mL of a bacterial solution containing Bacillus subtilis SJM1732 and mixed evenly, and the amount of live bacteria of Bacillus subtilis SJM1732 in the bacterial agent was not less than 1×10 8cfu / mL, and then 3000 black soldier fly 3rd instar larvae were inoculated. Both groups were treated with natural light, ventilation and 30℃ for 3 days. About 20 black soldier fly larvae were randomly selected from the two groups, and the intestines were dissected by sterile operation and sent to the sequencing company for 16S and ITS amplicon sequencing, intestinal flora diversity was analyzed, larval intestinal digestive enzyme activity was detected, the weight and length of black soldier fly larvae were measured, the material digestion capacity, water content and pH value were measured, and the ammonia release was detected by boric acid absorption titration. The results are shown in Tables 3 and 4. The intestinal flora diversity of black soldier flies in the experimental group (Group B) increased significantly, amylase, protease and lipase increased significantly, the material digestion capacity increased by 8% compared with the control group (Group A), the weight and length of black soldier fly larvae increased significantly, and the ammonia release decreased by 57%.

[0065] Table 3 Effects of the inoculant containing Bacillus subtilis SJM1732 on the diversity of intestinal flora and digestive enzymes of black soldier flies

[0066]

[0067]

[0068] Table 4 Effect of the bacterial agent containing Bacillus subtilis SJM1732 on the treatment of restaurant kitchen waste by black soldier flies

[0069] Detection indicators A. Black soldier fly B. Black soldier fly + strain SJM1732 Material consumption (g) 344±25 372±28 Material moisture content (%) 63.0±1.5 61.9±1.4 Material pH 6.72±0.11 7.32±0.42 Weight of black soldier flies (g / 20) 2.39±0.19 2.67±0.42 Black soldier fly length (cm) 1.60±0.03 1.64±0.03 <![CDATA[Ammonia release amount (×10 -5 mol)]]> 4.87±0.35 2.10±0.10

[0070] Example 6: Application of a bacterial agent containing Bacillus subtilis SJM1732 to improve the pupation rate of black soldier flies cultured in livestock and poultry manure

[0071] The moisture content of fresh pig manure was adjusted to 70% with sawdust, and 1 kg was weighed and placed in 6 round plastic lunch boxes with a volume of 2L, with 3 lunch boxes as a group. The bacterial solution containing Bacillus subtilis SJM1732 was added to the materials of one group at a 10% inoculation rate and mixed well as the experimental group, and the other group was not added with any bacteria as the blank control group. Figure 5 As shown, 3,000 third-instar black soldier fly larvae were placed in each lunch box, and placed under natural light, ventilation, and 30°C. When pupation occurred in the lunch box, the pupae were picked out and counted. When the pupation rate of one box exceeded 50%, the experiment was stopped and the relevant data were counted. The results showed that when the pupation rate of the experimental group (Group B) reached 51%, the pupation rate of the blank control group (Group A) was only 39%. It can be seen that the bacillus subtilis SJM1732 bacterial agent increased the pupation rate of black soldier flies, which is beneficial to shorten the breeding cycle of black soldier flies larvae and improve breeding efficiency.

[0072] Table 5 Effect of the bacterial agent containing Bacillus subtilis SJM1732 on the pupation rate of black soldier fly larvae

[0073] Detection indicators A. Black soldier fly B. Black soldier fly + strain SJM1732 Pupation rate (%) 39 51

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A Bacillus subtilis SJM1732, characterized in that: The strain was isolated from the intestine of black soldier fly and was deposited in the General Microbiology Center of China National Microbiological Culture Collection Administration on September 17, 2019. It was classified and named Bacillus subtilis SJM1732 and the deposit number was CGMCC No.18496. The 16S rRNA gene sequence of the strain is shown in SEQ ID NO:

1.

2. A bacterial agent, characterized in that The bacterial agent comprises the Bacillus subtilis SJM1732 described in claim 1.

3. The bacterial agent according to claim 2, characterized in that The bacterial agent can be concentrated to form a liquid bacterial agent or freeze-dried to form a solid bacterial powder, and the amount of live bacteria of Bacillus subtilis SJM1732 in the bacterial agent is not less than 10 8 cfu / mL or 10 8 cfu / g.

4. A method for preparing the bacterial agent according to claim 2, characterized in that: The following steps are involved: S1. Strain activation: Pick Bacillus subtilis SJM1732 strain and inoculate it onto solid slant medium, and culture it in a constant temperature incubator at 28-37°C for 24-48h; S2, liquid seed preparation: inoculate the activated Bacillus subtilis SJM1732 strain in step S1 into a container filled with liquid seed culture medium, seal the container with gauze, and culture under shaking conditions of 28-37° C. and 160-220 r / min for 24-48 hours to obtain liquid seeds; S3, liquid fermentation: the liquid seeds prepared in step S2 are inoculated into the fermentation medium at a volume ratio of 1-10%, the rotation speed is 200-700 r / min, the dissolved oxygen is controlled at 20-40%, the pH is 6.0-7.5, the temperature is 28-37° C., and the 10L fermenter is aerated and cultured for 24-48 hours to obtain a liquid bacterial agent of Bacillus subtilis SJM1732.

5. The method for preparing a bacterial agent according to claim 4, characterized in that: The solid slant culture medium comprises: 1-5 g / L glucose, 3-7 g / L yeast extract, 5-15 g / L peptone, 3-7 g / L NaCl, 15-20 g / L agar, dissolved in distilled water to a volume of 1 L, pH 7.0-7.2, and sterilized by high-pressure steam at 121° C. for 15-20 min.

6. The method for preparing a bacterial agent according to claim 4, characterized in that: The liquid seed culture medium is composed of 5-15 g / L glucose, 1-5 g / L beef extract, 3-7 g / L yeast extract, 0.5-2.0 g / L KH2PO4, 0.1-1.0 g / L MgSO4·7H2O, 0.1-0.5 g / L CaCl2·2H2O, 1-5 g / L (NH4)2SO4, dissolved in distilled water to a volume of 1 L, pH 7.0-7.2, and sterilized by high-pressure steam at 121°C for 15-20 min.

7. The method for preparing a bacterial agent according to claim 4, characterized in that: The fermentation medium comprises: 10-30 g / L glucose, 1-5 g / L beef extract, 0.5-2.0 g / L yeast extract, 0.5-2.0 g / L KH2PO4, 0.2-0.6 g / L MgSO4·7H2O, 0.1-0.5 g / L CaCl2·2H2O, 1-5 g / L ammonium citrate, 5-15 g / L corn steep liquor, 0.5-2.0 mg / L FeSO4, 1-3 mg / L vitamin B1, dissolved in distilled water to a volume of 1 L, pH 7.0-7.2, and sterilized by high-pressure steam at 121°C for 15-20 min.

8. Use of the bacterial agent according to claim 2 in enhancing the ability of black soldier flies to treat livestock and poultry excrement and food waste.

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