Lysobacter strain and application thereof

Abstract

The invention discloses a lysobacter strain and application of the lysobacter strain. The lysobacter strain is a new species in lysobacter, and the preservation number of the lysobacter strain is CGMCC (China General Microbiological Culture Collection Center) No. 1.19230. The strain D1-1-M9 obtained by separation is a new species different from a known species of Lysobacter, and can be used for producing extracellular protease (Protease). The produced extracellular protease can keep relatively high protease activity in medium-temperature and low-temperature environments, so that the extracellular protease has very wide development and application prospects in medicine, food and industrial production.

Description

Technical Field

[0001] The invention relates to the field of microbial technology, in particular to a lysobacter strain and application thereof, and more particularly to a study on the enzymatic properties of the extracellular protease of the lysobacter strain. Background Art

[0002] Lysobacter was first proposed by Canadian scholars Christensen and Cook in 1978. It belongs to the Procaryotes, Proteobacteria, Gammaproteobacteria, Xanthomonadales, and Xanthomonadaceae. The main characteristics of Lysobacter are: Gram-negative, aerobic rod-shaped bacteria; the main respiratory quinone is ubiquinone Q-8, polar lipids are mainly diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE); the genome size is 2.5-6.7Mb, and the genome G+C% content is 61.6%-71.6%.

[0003] Lysobacter is widely distributed in terrestrial soils, especially in the rhizosphere soil of crops. Most of them have a broad spectrum of antagonistic effects on plant pathogens. Lysobacter has also been found in freshwater, seawater and Antarctic coastal sediments, indicating that Lysobacter has a strong adaptability to extreme environments. New species of Lysobacter have also been found in samples of plants and animals and their related environments, such as tomato stems, sponge samples, Antarctic penguin feathers, giant panda breeding pens, Pacific shrimp intestines, python respiratory tracts, human meibomian gland secretions, Oriental white stork feces, and cow dung accumulations.

[0004] Lysobacter has high metabolic activity and can secrete a variety of active substances such as antibiotics and extracellular hydrolases. These active substances have good antagonistic activity against a variety of plant pathogens, nematodes, bacteria, etc. Therefore, it can be used as a new type of biocontrol bacteria with broad-spectrum antagonistic activity against bacteria, fungi and nematodes.

[0005] Lysobacter can secrete a variety of macromolecular active substances, such as phosphatases bound to cell membranes, nucleases produced after the exponential growth phase of the bacteria, cellulases with β-1,4-glucanase and chitosanase activities, keratinase with high decomposition activity on keratin, endopeptidase (hydrolase) that can specifically recognize the carboxyl group of lysine residues, and chitinase, α-1,3-glucanase, and protease that degrade the cell walls of microorganisms such as nematodes. Lysobacter can use these extracellular enzymes to antagonize the growth of plant pathogenic microorganisms, thereby achieving the purpose of preventing and controlling crop diseases.

[0006] Protease hydrolysis activity is one of the most common characteristics of Lysobacter, which can be used as a hemostatic agent after cleaning wounds. In the food industry, proteases play an important role in the processing and production of meat, dairy products and beverages. Bacterial proteases are important detergent enzymes, accounting for 90% of global enzyme sales. Existing experimental data show that the proteases produced by Lysobacter have antagonistic activity against different pathogens. Researchers have used protease inhibitor experiments to confirm that proteases are related to the formation and release of spores and spores.

[0007] Proteases from bacteria have the characteristics of short production cycle, low cost, and easy management and control. Moreover, most proteases synthesized by microorganisms are extracellular enzymes, which are relatively easy to purify and prepare, and the production cost is greatly reduced. Microorganisms are increasingly becoming the main source of industrial enzyme preparations. The acquisition of excellent strains is the key to protease production, so the isolation and identification of new strains is an important step in obtaining high-yield protease strains. With the continuous deepening of research on Lysobacterium resources and their natural products, it is believed that more and more active natural products will be discovered, providing rich lead compounds for the development of biological control and biomedicine. Summary of the invention

[0008] The main purpose of the invention is to provide a Lysobacter sp.D1-1-M9 strain.

[0009] The Lysobacter strain D1-1-M9 provided by the present invention is isolated from the soil on the shore of Longmu Co Lake in Ali region, Tibet. The strain has been deposited in the General Microbiological Center of China Microbiological Culture Collection Administration Committee, with a deposit number of CGMCC No.1.19230 and a deposit date of November 8, 2023. After bacterial strain identification, it was found that the strain is a new species in the genus Lysobacter. The 16S rRNA gene sequence of the strain is shown in SEQ.NO.1.

[0010] The study found that the Lysobacterium strain D1-1-M9 can produce extracellular protease (Protease). And can use D-trehalose, D-cellobiose, D-raffinose, β-methyl-D-glucoside, N-acetyl-D-glucosamine, N-acetyl-β-D-mannoamine, N-acetyl-D-glucosamine, α-D-glucose, D-fructose, D-galactose, 3-methyl-D-glucose, D-fucose, L-fucose, L-rhamnose, inositol, glycerol, D-glucose-6-PO4, D-fructose-6-PO4, D-aspartic acid, alum Gum, L-alanine, L-arginine, L-aspartic acid, L-glutamic acid, L-histidine, L-pyroglutamic acid, L-serine, pectin, D-galactonic acid, L-galactonolactone, D-gluconic acid, D-glucuronic acid, L-lactic acid, citric acid, α-keto-glutaric acid, L-malic acid, Tween 40, α-hydroxy-butyric acid, β-hydroxy-D, L-butyric acid, α-keto-butyric acid, acetoacetic acid, propionic acid, and acetic acid are the sole carbon sources, with a broad spectrum of substrates.

[0011] According to physiological experiments, strain D1-1-M9 can grow at a temperature of 10-35°C, a pH of 6.5-10, and a NaCl concentration of 1.0%-4.0% (w / v). The strain grows best at 25°C, pH 7.0, and a NaCl concentration of 1.0%.

[0012] Through optimization of culture, it was found that when the NaCl concentration was 1.0% and 10% glucose was added to the 2216 medium, D1-1-M9 had the best protease production ability. Enzyme property studies found that the highest reaction conditions for the protease activity produced by Lysobacterium D1-1-M9 were 40°C and pH 7. It can maintain relatively high protease activity in medium and low temperature environments, but is not resistant to high temperatures. Metal ions Mg 2+ and Fe 3+ (5.0mmol / L) can inhibit its activity, and the relative activity after inhibition is only 52.3% and 30.6% of the control. This strain has a wide application prospect in the research of microbial extracellular protease production.

[0013] In addition, the present invention also discloses a fermentation liquid and a liquid bacterial agent prepared from the above-mentioned Lysobacter strain and a preparation method thereof, the method comprising:

[0014] 1) Strain activation: Pick the strain and inoculate it onto 2216 solid culture medium, place it in a constant temperature incubator, and culture it at 25°C for 24 hours;

[0015] 2) Preparation of seed solution: Pick activated bacteria and inoculate them into a large test tube containing seed culture medium, seal it with a rubber stopper, place it on a shaker at 25°C, and shake and culture at 160 rpm for 16-24 hours to obtain seed solution;

[0016] 3) Liquid fermentation: The seed liquid and seed culture medium are then expanded with an inoculation amount of 5-10% by volume, and the culture conditions are 25°C and 160rpm; the culture obtained after 48 hours of culture is the fermentation liquid; the fermentation liquid is centrifuged at 12000rpm for 10 minutes, and the bacteria are collected to obtain a liquid bacterial agent.

[0017] Among them, the seed culture medium is 2216 liquid culture medium, and the formula of the 2216 liquid culture medium is: 5.0g peptone, 1.0g yeast extract, 0.1g ferric citrate, 19.45g sodium chloride, 8.8g magnesium chloride, 3.24g sodium sulfite, 1.3g calcium chloride, 0.55g potassium chloride, 0.16g sodium bicarbonate, 0.08g potassium bromide, 34.0mg strontium chloride, 22.0mg boric acid, 4.0mg sodium silicate, 2.4mg sodium fluoride, 1.6mg ammonium nitrate, 8.0mg disodium hydrogen phosphate, distilled water is added to make the volume to 1000mL, and sterilized at 121°C for 20min; the formula of the 2216 solid culture medium is 15.0g agar added to the 2216 liquid culture medium.

[0018] In addition, experiments have shown that the Lysobacterium strain of the present invention or the fermentation broth and liquid bacterial agent obtained by using the strain can produce extracellular protease.

[0019] The optimal culture conditions for producing extracellular proteases were also obtained. When the NaCl concentration in the 2216 liquid culture medium was 1.0% and 10% glucose was added, the ability of D1-1-M9 to synthesize proteases was optimal.

[0020] Advantages of the present invention:

[0021] The lytic bacillus D1-1-M9 of the present invention is separated from the soil on the shore of Longmu Co Salt Lake in Ali area of ​​Tibet, and the environment is not polluted, and it has no ecological toxicity, high safety and strong stability.

[0022] The Lysobacter D1-1-M9 of the present invention is identified as a new species of the genus Lysobacter through 16S rRNA gene sequence analysis, genome analysis, phylogenetics and multiple taxonomic analyses.

[0023] The Lysobacterium D1-1-M9 of the present invention has simple culture, short cycle, strong stability, broad substrate spectrum, and can produce extracellular protease. The produced extracellular protease can maintain relatively high protease activity under medium and low temperature environments, so it has very broad development and application prospects in medicine, food and industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1:The morphology of strain D1-1-M9 under electron transmission microscope (left) and the transparent circle formed on the milk plate (right);

[0025] Figure 2 : Phylogenetic tree of 16S rRNA gene of strain D1-1-M9;

[0026] Figure 3 :The effect of NaCl concentration on the protease synthesis of strain D1-1-M9;

[0027] Figure 4 :The effect of carbon source on the protease synthesis of strain D1-1-M9;

[0028] Figure 5 : Relative protease activity of strain D1-1-M9 at different temperatures;

[0029] Figure 6 : Relative protease activity of strain D1-1-M9 under different pH conditions;

[0030] Figure 7 : Relative protease activity of strain D1-1-M9 under different metal ions. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific examples, and the advantages and features of the present invention will become clearer as the description proceeds. However, the specific experimental methods involved in the following examples are all conventional methods or implemented under the conditions recommended by the manufacturer's instructions unless otherwise specified.

[0032] Unless otherwise specified, the technical means used in the examples are conventional means known to those skilled in the art. The test methods in the following examples are conventional methods unless otherwise specified. Unless otherwise specified, the reagents and materials used can all be purchased from the market.

[0033] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only.

[0034] Example 1 Isolation and identification of Lysobacterium D1-1-M9 strain

[0035] a. Soil sample collection: Soil was collected from the shore of Longmu Co Lake in Ali region of Tibet, placed at 4°C and brought back to the laboratory for strain isolation using the plate dilution coating method.

[0036] b. The culture medium for isolating the strain is 2216 solid culture medium: 5.0 g of peptone, 1.0 g of yeast extract, 0.1 g of ferric citrate, 19.45 g of sodium chloride, 8.8 g of magnesium chloride, 3.24 g of sodium sulfite, 1.3 g of calcium chloride, 0.55 g of potassium chloride, 0.16 g of sodium bicarbonate, 0.08 g of potassium bromide, 34.0 mg of strontium chloride, 22 mg of boric acid, 4.0 mg of sodium silicate, 2.4 mg of sodium fluoride, 1.6 mg of ammonium nitrate, 8.0 mg of disodium hydrogen phosphate, 15 g of agar, distilled water is added to make up to 1000 mL, pH 7.2-7.4, and sterilized at 121°C for 20 min.

[0037] c. Separation by plate dilution and coating method: Mix the collected soil samples thoroughly, weigh 10g, put into a triangular flask with appropriate amount of glass beads and 90mL sterile water, place the triangular flask on a shaker, shake for 20min, let stand for 5min, dilute in sequence by 10-fold gradient dilution method, take 10 -4 , 10 -5 , 10 -6 200 μL of soil dilution was evenly spread on the solid plate of 2216 medium. Three plates were spread for each dilution, inverted and cultured in a constant temperature incubator at 20°C for 14 days, and single colonies with different colony morphology were selected for further streaking purification. The purified strains were transferred to 2216 slant medium and stored at 4°C for later use.

[0038] d. Identification of strains: After streaking, the purified strain D1-1-M9 was streaked on a 2216 plate and the colony morphology was observed: the colonies were round, yellow and creamy, with a smooth, opaque surface and neat edges. The cell morphology was observed under an electron transmission microscope and the cells were long rod-shaped ( Figure 1 ). The PCR amplicon was sequenced using 16S rRNA universal primers 27F and 1492R, and the resulting sequence is shown in SEQ ID NO.1. By comparing the 16S rRNA sequences of known strains in the Genbank database, it was found that the 16S rRNA gene sequence of strain D1-1-M9 was the most similar to that of Lysobacter erysipheiresistens RS-LYSO-3 (97.80%). According to the Bergey Manual of Bacterial Identification and multiple taxonomic methods, the phenotypic and physicochemical characteristics of the strains were analyzed, and the phylogenetic tree analysis was combined with the 16S rRNA gene sequence ( Figure 2 ) and genome sequencing analysis, it was determined that the D1-1-M9 strain was a new species of the genus Lysobacter (Lysobacter sp.nov.). The strain has been deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration, with the deposit number CGMCC No.1.19230 and the deposit date of November 8, 2023.

[0039] Wherein, the sequence of SEQ ID NO.1 is as follows:

[0040]

[0041] After studying the strain, it was found that strain D1-1-M9 can utilize D-trehalose, D-cellobiose, D-raffinose, β-methyl-D-glucoside, N-acetyl-D-glucosamine, N-acetyl-β-D-mannoamine, N-acetyl-D-glucosamine, α-D-glucose, D-fructose, D-galactose, 3-methyl-D-glucose, D-fucose, L-fucose, L-rhamnose, inositol, glycerol, D-glucose-6-PO4, and D-fructose-6-PO4. 4. D-aspartic acid, gelatin, L-alanine, L-arginine, L-aspartic acid, L-glutamic acid, L-histidine, L-pyroglutamic acid, L-serine, pectin, D-galactonic acid, L-galactonic acid lactone, D-gluconic acid, D-glucuronic acid, L-lactic acid, citric acid, α-keto-glutaric acid, L-malic acid, Tween 40, α-hydroxy-butyric acid, β-hydroxy-D, L-butyric acid, α-keto-butyric acid, acetoacetic acid, propionic acid, acetic acid as the sole carbon source, with a broad spectrum of substrates. In addition, according to physiological experiments, strain D1-1-M9 can grow at a temperature of 10-35°C, pH 6.5-10, and a NaCl concentration of 1.0-4.0% (w / v); when under the conditions of 25°C, pH 7.0, and 1.0% NaCl, the growth state of strain D1-1-M9 is the best.

[0042] And the strain D1-1-M9 can form a transparent circle on the milk plate ( Figure 1 We first optimized the culture conditions for the protease synthesis of the Lysobacter strain D1-1-M9, and then conducted further experiments to verify some enzymatic properties of the produced protease.

[0043] Example 2 Optimization of culture conditions for protease synthesis by Lysobacterium strain D1-1-M9

[0044] 1) Effect of NaCl concentration on D1-1-M9 protease synthesis

[0045] NaCl was added to the 2216 liquid medium to make the final salt concentration of the medium 1.0%, 2.0%, 3.0%, 4.0%, and the inoculation volume ratio of the seed liquid and the fermentation medium (2216 liquid medium) was 5-10% for expansion culture. The culture conditions were 25°C, 160rpm, and cultured for 48h. The obtained culture was the fermentation liquid. The bacterial cells were collected according to the above method to obtain the crude enzyme liquid, and the enzyme activity of the crude enzyme liquid was determined. The results are as follows Figure 3When the NaCl concentration was 1.0%, the ability of D1-1-M9 to synthesize protease was the best.

[0046] 2) Effect of carbon source on protease production

[0047] 10% glucose, sucrose, lactose, maltose, soluble starch and corn flour were added to the 2216 liquid medium as supplementary carbon sources, and the inoculation volume was 5-10% according to the seed liquid and the fermentation medium (2216 liquid medium) for expansion culture. The culture conditions were 25°C, 160rpm, and cultured for 48h. The obtained culture was the fermentation liquid. The cells were collected according to the above method to obtain the crude enzyme liquid, and the enzyme activity of the crude enzyme liquid was determined. The results are as follows Figure 4 When 10% glucose was added, the ability of D1-1-M9 to synthesize protease was the best.

[0048] Example 3 Enzymatic properties of Lysobacter strain D1-1-M9

[0049] 1. Drawing of the tyrosine standard curve of Lysobacterium strain D1-1-M9

[0050] a. Take 18 test tubes and divide them into six groups, 3 tubes in each group. Add standard tyrosine, deionized water, 0.4 mol / L Na2CO3 and Folin phenol reagent according to Table 1 and mix well.

[0051] b. Place in a 40℃ water bath for 20 minutes, then take out and place at room temperature. Use a UV spectrophotometer for colorimetric measurement, set the wavelength to 680nm, and measure the OD 680 , where the blank control is a solution without tyrosine added; a standard curve of tyrosine solution is drawn based on the experimental results.

[0052] 2. Determination of protease activity of Lysobacterium strain D1-1-M9

[0053] a. Inoculate a single colony of strain D1-1-M9 into 2216 liquid culture medium and culture at 25°C and 160 rpm for 48 h;

[0054] b. Inoculate the bacterial solution into the fermentation medium and culture at 25°C, 160 rpm for 48 hours;

[0055] c. Adjust the bacterial concentration to OD 680 value is 0.500, centrifuge at 12000rpm for 10min, and the supernatant is the crude enzyme solution.

[0056] d. Determine the protease activity using the Folin phenol method. Preheat the crude enzyme solution and casein solution in a 40°C water bath for 5 min before the assay. Take 1 mL of the crude enzyme solution from the test group and add it to 1 mL of 10 g / L casein solution and incubate in a 40°C water bath for 10 min; immediately add 3 mL of 0.4 mol / L trichloroacetic acid solution to terminate the reaction.

[0057] e. Take 1 mL of crude enzyme solution in the control group, add 3 mL of 0.4 mol / L trichloroacetic acid solution, incubate in 40°C water bath for 10 min to inactivate the protease, then add 1 mL of 10 g / L casein solution, let stand for 10 min; centrifuge at 12000 rpm for 10 min.

[0058] f. Take 1 mL of the supernatant from the test group and the control group respectively, add 5.0 mL of 0.4 mol / L Na2CO3 solution and 1 mL of Folin reagent solution, and color in a 40°C water bath for 20 min;

[0059] g. Measure the OD of the sample at 680 nm using a UV-visible spectrophotometer 680 The experimental group OD 680 The OD of the control group was subtracted from the value 680 The net OD value is obtained.

[0060] The enzyme activity calculation formula is:

[0061]

[0062] Where: X is the sample enzyme activity (U / mL); 5 means 1 mL is taken out of 5 mL of reaction solution for measurement, i.e. 5 times; A is the corresponding tyrosine content obtained by checking the standard curve based on the net OD value; n is the dilution factor of the enzyme solution; 10 means 1 minute is taken out of 10 minutes of reaction for calculation, i.e. 1 / 10.

[0063] III. Test on the stability of protease activity of Lysobacterium strain D1-1-M9

[0064] 1) Thermal stability of proteases

[0065] Take the enzyme solution and casein solution in the optimal pH solution and react at 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ for 60min, and measure the enzyme activity to determine the optimal reaction temperature of the enzyme. After the reaction is completed, the system is immediately put in an ice bath, and the enzyme activity is measured to determine the heat resistance of the enzyme. The results are as follows: Figure 5As shown. At 20-40℃, the protease activity of Lysobacter D1-1-M9 slowly increased, reaching the maximum activity at 40℃. At 20℃ and 30℃, the relative protease activity was 86.9% and 91.26%, respectively. As the temperature continued to rise from 40℃, the protease activity of Lysobacter D1-1-M9 began to decline rapidly. When the temperature was 50℃ and 60℃, the relative protease activity decreased to 62.5% and 10.21%; at 70℃, the relative protease activity was only 0.82%. It can be seen that the optimum temperature of the protease produced by Lysobacter D1-1-M9 is 40℃. It can maintain a relatively high protease activity in medium and low temperature environments, but is not resistant to high temperatures.

[0066] 2) Optimal reaction pH of protease

[0067] Prepare a 1 mg / mL substrate casein solution with 50 mmol / L Tris-HCl at a pH range of 1.5-9.0. Take 10 μL of the enzyme solution and 100 μL of the substrate solution at different pH values ​​and react at 30°C for 60 min. Then add trichloroacetic acid to terminate the reaction and measure the enzyme activity to determine the pH stability of the enzyme. The results are as follows: Figure 6 As shown in the figure, the activity of the protease produced by Lysobacter D1-1-M9 gradually increased with the increase of pH value when the pH value was 3.0-7.0, and the relative activity was the largest when the pH value was 7.0. In an alkaline environment, the relative activity decreased relatively slowly. When the pH value reached 10, the activity of the protease basically did not change, and its relative activity was maintained at about 30%.

[0068] 3) Metal ion tolerance of proteases

[0069] Take 10 μL of enzyme solution and react with casein solution at the optimal pH and temperature for 60 minutes, then add trichloroacetic acid to terminate the reaction, measure the enzyme activity, and set it as 100%; add 0.2, 1.0, 5.0, 10 mmol / L of FeCl3·6H2O, ZnCl2, CaCl2·2H2O, MnCl2, MgCl2·6H2O to this reaction system, respectively, and perform sample treatment and determination according to the standard sample treatment method. The results are as follows Figure 7 The enzyme activity of the control group (no metal ions added) was set to 100%. Compared with the control group, the Mn 2+ When the concentration of Ca was 5.0mmol / L, the enzyme activity was 115.2% of that in the control group. 2+ and Zn 2+ When the concentration was 5.0mmol / L, the relative protease activities were 102.3% and 98.3% of the control group, respectively. 2+ and Zn 2+ It has little effect on the relative protease activity. 2+and Fe 3+ When the concentration was 5.0mmol / L, the relative activity was inhibited, and its relative activity was only 52.3% and 30.6% of the control.

[0070] The embodiments described above are only preferred embodiments of the present invention and are only used to explain the present invention, not to limit the scope of implementation of the present invention. For those skilled in the art, other implementation methods can certainly be easily made by replacement or modification based on the technical contents disclosed in this specification. Therefore, all changes and improvements made on the principles of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A Lysobacterium strain, characterized in that The strain is Lysobacter sp. D1-1-M9, which is deposited in the General Microbiology Center of China Microbiological Culture Collection Administration, with a deposit number of CGMCC No.1.19230.

2. The Lysobacterium strain according to claim 1, characterized in that The 16SrRNA gene sequence of the strain is shown as SEQ ID NO.

1.

3. The Lysobacterium strain according to claim 1, characterized in that The strain D1-1-M9 can grow under the conditions of a temperature of 10-35° C., a pH value of 6.5-10, and a NaCl concentration of 1.0%-4.0%.

4. The Lysobacterium strain according to claim 3, characterized in that The optimal growth conditions of the strain D1-1-M9 are 25° C., pH 7.0, and NaCl concentration of 1.0%.

5. The fermentation liquid and liquid bacterial agent prepared from the Lysobacterium strain according to claim 1.

6. A method for preparing the fermentation liquid and liquid bacterial agent according to claim 5, characterized in that: The method comprises: 1) Strain activation: Pick the strain and inoculate it onto 2216 solid culture medium, place it in a constant temperature incubator, and culture it at 25°C for 24 hours; 2) Preparation of seed solution: Pick activated bacteria and inoculate them into a large test tube containing seed culture medium, seal it with a rubber stopper, place it on a shaker at 25°C, and shake and culture at 160 rpm for 16-24 hours to obtain seed solution; 3) Liquid fermentation: The seed liquid and seed culture medium are then expanded with an inoculation amount of 5-10% by volume, and the culture conditions are 25°C and 160rpm; the culture obtained after 48 hours of culture is the fermentation liquid; the fermentation liquid is centrifuged at 12000rpm for 10 minutes, and the bacteria are collected to obtain a liquid bacterial agent.

7. The method according to claim 6, characterized in that The seed culture medium is 2216 liquid culture medium, and the formula of the 2216 liquid culture medium is: 5.0g of peptone, 1.0g of yeast extract, 0.1g of ferric citrate, 19.45g of sodium chloride, 8.8g of magnesium chloride, 3.24g of sodium sulfite, 1.3g of calcium chloride, 0.55g of potassium chloride, 0.16g of sodium bicarbonate, 0.08g of potassium bromide, 34.0mg of strontium chloride, 22.0mg of boric acid, 4.0mg of sodium silicate, 2.4mg of sodium fluoride, 1.6mg of ammonium nitrate, 8.0mg of disodium hydrogen phosphate, distilled water is added to make the volume to 1000mL, and sterilized at 121°C for 20min; the formula of the 2216 solid culture medium is 15.0g of agar added to the 2216 liquid culture medium.

8. Use of the Lysobacterium strain according to claim 1 or the fermentation broth and liquid bacterial agent according to claim 5 in producing extracellular protease.

9. The use according to claim 8, characterized in that: The Lysobacter strain can directly synthesize extracellular protease during the culture process. The optimal culture conditions for the Lysobacter strain to synthesize extracellular protease are: the concentration of NaCl in the 2216 liquid culture medium is 1.0%, and 10% glucose is added.

Images