Bacillus velezensis LYB-S and application thereof in improving hexavalent chromium reduction rate by combining with exosomes

Abstract

The application is a bacillus velezensis LYB-S and its application in improving the reduction rate of hexavalent chromium combined with exosomes, belonging to the technical field of environmental remediation. The bacillus velezensis LYB-S was preserved in the China General Microbiological Culture Collection Center on May 6, 2025, and the preservation number is CGMCC NO. 34429. The bacillus velezensis (Bacillus velezensis) Bacillus velezensis ) LYB-S can be combined with exosomes to jointly improve the reduction rate of hexavalent chromium.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing an environment by combining exosomes with microorganisms, and specifically relates to a strain of Bacillus Velezii LYB-S and its application in improving the hexavalent chromium reduction rate in combination with exosomes. Background Art

[0002] With the development of industry and agriculture, chromium has become the second largest inorganic pollutant. Chromium pollution in the environment can easily enter plant biomass, ultimately threatening people's food safety and health through the food chain.

[0003] Cr exists primarily in the environment in the forms of Cr(VI) and Cr(III). Cr(III) is primarily insoluble and a biologically important micronutrient. However, Cr(VI) can interfere with plant growth, nutrient absorption, and photosynthesis, induce the production of reactive oxygen species (ROS), lead to lipid peroxidation, and alter antioxidant activity, inducing phytotoxicity. Chromium pollution not only affects crop growth, resulting in reduced yields and poor quality, but excessive chromium can also damage crop cell structure, impair photosynthesis and nutrient absorption, and in severe cases, even lead to plant death. Chromium in crops can enter the human body through the food chain and accumulate in the body. Cr(VI) is a strong oxidant and carcinogenic. Long-term exposure can lead to a variety of health problems, such as skin ulcers, respiratory problems, liver and kidney damage, and even an increased risk of cancer.

[0004] Therefore, Cr(VI) has caused serious impacts on ecosystems and human health, and the control of chromium pollution is imminent. Summary of the Invention

[0005] The present invention aims to address the problems existing in the prior art and provide a strain of Bacillus velezensis LYB-S. The strain can be used in combination with exosomes to improve the reduction rate of hexavalent chromium. Through this method, the reduction efficiency of Cr(VI) by Bacillus velezensis LYB-S can be significantly improved.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] One of the objects of the present invention is to protect a strain of Bacillus velezinis ( Bacillus velezensis )LYB-S, the strain was deposited in the General Microbiology Center of China Culture Collection Administration on May 6, 2025, with the deposit number CGMCC NO.34429. The depository address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0008] The present invention also protects the above-mentioned Bacillus Velezii ( Bacillus velezensis ) Application of LYB-S in combination with exosomes to improve the hexavalent chromium reduction rate.

[0009] Furthermore, in the application of the Bacillus Velez subtilis LYB-S in combination with exosomes to improve the hexavalent chromium reduction rate, the Bacillus Velez subtilis LYB-S has the following characteristics:

[0010] 1) It can grow in conjunction with exosomes and significantly increase the hexavalent chromium reduction rate;

[0011] 2) Bacillus Velez LYB-S has high tolerance to chromium.

[0012] Bacillus velez ( Bacillus velezensis ) LYB-S is a strain isolated from the wild and obtained through gradient acclimation to hexavalent chromium; the original isolated strain has a tolerance to chromium of 150 mg / L; the strain obtained through gradient acclimation to hexavalent chromium has a tolerance to chromium of 350 mg / L.

[0013] The second object of the present invention is to protect Bacillus Velezii LYB-S in combination with exosomes to improve the hexavalent chromium reduction rate, comprising the following steps:

[0014] 1) Preparation of exosomes;

[0015] 2) The exosomes prepared in step 1) were mixed with the Bacillus velezensis ( Bacillus velezensis ) LYB-S is used in combination to improve the hexavalent chromium reduction rate.

[0016] Furthermore, the exosomes described in step 1) are highland barley exosomes.

[0017] Furthermore, in the method for improving the hexavalent chromium reduction rate by combining Bacillus Velez subtilis LYB-S with exosomes, the specific steps of step 2) are: Bacillus velezensis ) LYB-S was activated, and then the Velez-Bacillus ( Bacillus velezensis ) LYB-S bacterial suspension, followed by the Velez-Bacillus ( Bacillus velezensis ) The bacterial suspension of LYB-S is added to LB medium containing exosomes and hexavalent chromium for cultivation, that is, the hexavalent chromium is reduced to achieve an increase in the reduction rate of hexavalent chromium. This method can significantly increase the reduction rate of hexavalent chromium.

[0018] Furthermore, in the method for improving the hexavalent chromium reduction rate by combining Bacillus Velez subtilis LYB-S with exosomes, the preparation steps of highland barley exosomes are as follows:

[0019] 1) Sample pretreatment

[0020] The barley roots were cut and separated with a scalpel, washed with distilled water and then the surface water was filtered to obtain the sample;

[0021] The obtained sample was minced and soaked in 75wt% alcohol for 1 min. After washing with distilled water to remove the alcohol residue, it was dried with sterile paper and enzymatically hydrolyzed at 50℃ for 6 h. The obtained sample was then centrifuged at 10,000 rpm for 1 h to allow the enzymatic hydrolysis tissue residue to settle. The supernatant was passed through a cell sieve and the filtrate was collected to obtain the highland barley root sample.

[0022] 2) Extraction of highland barley exosomes (HBELNs) by ultracentrifugation

[0023] After the highland barley root sample was thawed at a moderate speed at 37°C, it was centrifuged at 4°C at 2000×g for 30 min, the supernatant was collected at 10000×g for 45 min to remove large vesicles, and filtered through a 0.45 μm membrane. The filtrate was subjected to ultracentrifugation, the supernatant was discarded, 10 mL of the obtained liquid was pre-cooled and resuspended in PBS and then centrifuged under the same conditions. The final precipitate was resuspended in 150 μL PBS and divided into: 20 μL for electron microscopy, 10 μL for particle size detection, and the remaining sample was used for RNA extraction to obtain highland barley exosomes, namely, highland barley-derived HBELNs.

[0024] Furthermore, the culture temperature in the LB medium is 34° C., the pH value is 7, and the culture time is more than 12 h.

[0025] Furthermore, during sample pretreatment, the enzyme solution contained 4% cellulase by mass, 2% pectinase by mass, 0.6 mol / L mannitol, and the remainder was water, with a pH value of 5.8.

[0026] Furthermore, the conditions for ultracentrifugation were 100,000 × g, 4°C, 70 min.

[0027] Furthermore, in the above method, the concentration of hexavalent chromium is 100-350 mg / L.

[0028] Contains Bacillus velezensis ( Bacillus velezensis ) The concentration of LYB-S bacterial suspension was 10^8 CFU / mL; the concentration of highland barley exosomes was 50 μg / mL; the concentration of Bacillus velezinoffii ( Bacillus velezensis ) The volume ratio of LYB-S bacterial suspension to highland barley exosomes was 1:2.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The isolated Bacillus velezensis LYB-S can combine with exosomes to enhance the hexavalent chromium reduction rate;

[0031] 2) Exogenous addition of HBELNs could alleviate the stress of Cr(VI) on the domesticated strain LYB-S and significantly improve the hexavalent chromium reduction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Bacillus velezensis ( Bacillus velezensis ) Phylogenetic tree of LYB-S;

[0033] Figure 2 Electron micrographs, particle size, and concentration of HELN.

[0034] (a) Electron micrograph of HBELNs. (b) Concentration and particle size of HBELNs.

[0035] Figure 3 is the growth curve of bacteria LYB-S;

[0036] Figure 4 Figure 7 shows the reduction efficiency of LYB to 100, 200, and 300 mg / L Cr(VI) in the acclimated strain LYB-S within 72 days;

[0037] Figure 5 These are morphological analysis diagrams of bacteria, where A is the FTIR change diagram of the domesticated strain LYB-S, and B is the SEM analysis diagram. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described in further detail below in conjunction with the examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the invention. The present invention encompasses all possible alternatives, improvements, and equivalents within the scope of the claims. Specific techniques or conditions not specified in the following examples are all conventional techniques or conditions, or are based on the techniques or conditions described in the literature in this field, or are carried out according to the product instructions.

[0039] In this application, any % not explicitly stated refers to mass percentage, i.e. wt%.

[0040] Example 1

[0041] Isolation and identification of bacteria

[0042] On January 11, 2023, the test soil was collected in Deyang City, Sichuan Province. A total of 10 samples were collected, each 10g. After collection, they were stored in self-sealing bags at -80℃ ultra-low temperature refrigerator until use. 500ml of sterile distilled water was added to 5g of soil sample, stirred at room temperature for 1 hour, and serially diluted to 10 -6, and obtain the supernatant. The supernatant was spread on LB (10 g peptone, 3 g beef extract, 5 g NaCl, 5 g sucrose) plates and incubated at 30°C for 48 hours. Different colonies were separated by streaking on the plates according to their morphology. The minimum inhibitory concentration (MIC) of each isolated bacterium was determined using plates containing 50-500 mg / L Cr (VI). The three strains with the highest Cr (VI) MIC values ​​(one of which was LYB-WT) were selected for domestication. The isolated strain LYB-WT was identified based on morphology and 16 S rRNA gene sequencing. The 16 S rDNA sequence of this strain was consistent with that of Bacillus velezensis The 16 S rRNA sequence of strain FZB42 has 99.93% similarity, and the two have a close relationship in the evolutionary tree (the other two strains were also determined and analyzed as Bacillus velezensis strains). Therefore, strain LYB-WT was classified as B. velezensis and confirmed to be a strain of B. velezensis. Its chromium tolerance was 150 mg / L, while the other two strains were 148 mg / L and 145 mg / L, respectively.

[0043] Bacterial domestication: Improve the tolerance of isolated bacteria to Cr(VI) through domestication, and further improve their tolerance to Cr(VI). The specific domestication steps are as follows:

[0044] The three strains with the highest MIC values ​​of Cr (VI) were first inoculated (1%) into liquid LB medium containing 120 mg / L Cr (VI) and divided into 5 biological replicates. After incubation at 30°C for 12 h, the optical density (OD) was detected at 600 nm. The treatment group with the highest bacterial concentration was selected for further domestication. 1 mL of bacterial solution from the treatment group with the largest OD600 value was added to the LB medium containing 170 mg / L Cr (VI), and the culture was continued for 12 h, and its OD value was measured. Repeat the above steps until a certain concentration was reached and the bacteria stopped growing. At this point, the domestication of chromium-resistant bacteria was completed, and we named these three domesticated strains LYB-S, LYB-S-1, and LYB-S-2. Among them, LYB-S has the highest chromium tolerance. Comparison of 16 S rDNA sequence and phylogenetic tree showed that LYB-WT and domesticated strain LYB-S belong to the same species. Detailed evolutionary tree information of domesticated strain LYB-S is shown in Figure 1 The results show that the tolerance of the acclimated LYB-S strain to chromium is 350 mg / L, the tolerance of the LYB-S-1 strain to chromium is 340 mg / L, and the tolerance of the LYB-S-2 strain to chromium is 320 mg / L.

[0045] Since LYB-S has the highest tolerance to chromium, the acclimated Bacillus velezinis ( Bacillus velezensis ) LYB-S strain was preserved, which was deposited in the General Microbiology Center of China Culture Collection of Microorganisms on May 6, 2025, with the deposit number CGMCC NO.34429. The address of the depository is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0046] Example 2

[0047] 1 Extraction process of highland barley exosomes (HBELNs)

[0048] (1) Sample pretreatment

[0049] Highland barley roots were excised and separated using a scalpel, washed with distilled water, and dried with filter paper. All sampling instruments were sterilized under high temperature and high pressure in a clean bench. The samples were minced and soaked in 75% alcohol for 1 minute. After rinsing with distilled water to remove any residual alcohol, they were wiped dry with sterile paper. 20 mL of enzyme solution (4% cellulase, 2% pectinase, 0.6 mol / L mannitol, pH 5.8) was added and enzymatically digested at 50°C for 6 hours. The samples were centrifuged at 10,000 rpm for 1 hour to allow the digested tissue residue to settle. The supernatant was passed through a cell sieve, and the filtrate was collected. Samples were collected in triplicate.

[0050] (2) Extraction of HBELNs by ultracentrifugation

[0051] After moderate thawing of highland barley root samples at 37°C, centrifugation was performed at 2000 × g for 30 min at 4°C. The supernatant was collected and filtered through a 0.45 μm membrane at 10,000 × g for 45 min to remove large vesicles. The filtrate was then ultracentrifuged (100,000 × g, 4°C, 70 min), the supernatant discarded, resuspended in 10 mL of pre-chilled PBS, and centrifuged again under the same conditions. The final pellet was resuspended in 150 μL of PBS and aliquoted: 20 μL for electron microscopy, 10 μL for particle size analysis, and the remaining aliquot for RNA extraction.

[0052] 2. Characterization of HBELNs

[0053] Characterization of HBELNs included dynamics, particle size, and concentration. Transmission electron microscopy was used to characterize the morphology of HBELNs, TEM analysis was performed according to existing methods, and nanoflow cytometry was used to identify the particle size and concentration of HBELNs.

[0054] Result Analysis

[0055] Characterization of HBELNs

[0056] Figure 2Electron micrographs, particle size, and concentration of HBELNs. (a) Electron micrographs of HBELNs. (b) Concentration and particle size of HBELNs.

[0057] As shown in the electron microscopy image of HBELNs, HBELNs are oval vesicles with an average particle size of 79.0 nm and a concentration of 4.56E+10 (Particles / mL).

[0058] Example 3:

[0059] Effect of HBELNs and LYB-S on the reduction rate of Cr(VI)

[0060] In Example 2, highland barley exosomes (HBELNs) were extracted from the roots of highland barley seedlings by ultracentrifugation. The preserved Bacillus lybdenum lybdenum in Example 1, as well as the unpreserved LYB-S-1 (only preserved in the laboratory) and LYB-S-2 (only preserved in the laboratory) were activated together, and then (using conventional methods) the Bacillus lybdenum ( Bacillus velezensis )LYB-S, containing Bacillus velezensis ( Bacillus velezensis )LYB-S-1, containing Bacillus velezensis ( Bacillus velezensis LYB-S-2 bacterial suspensions (both at a concentration of 10^8 CFU / mL) were inoculated into LB medium containing 100 mg / L Cr(VI) + HBELNs (highland barley exosome concentration of 50 μg / mL), 200 mg / L Cr(VI) + HBELNs (highland barley exosome concentration of 50 μg / mL), and 300 mg / L Cr(VI) + HBELNs (highland barley exosome concentration of 50 μg / mL), respectively (the volume ratio of bacterial suspension to highland barley exosomes was 1:2). The cultures were incubated at 34°C and pH 7, and the OD values ​​were measured every 12 hours. Cr(VI) concentrations in the culture medium were determined using a 1,5-diphenylcarbourea spectrophotometer. The Cr(VI) removal efficiency was calculated according to the following formula:

[0061]

[0062] Cr(VI)0——initial concentration of Cr(VI) N ——Concentration of Cr(VI) at Nh

[0063] All experiments included five biological replicates and were analyzed for variance using SPSS software. Significant differences were considered between treatment groups when the P value was less than 0.05. Visualization was performed using Origin 2024. The results of the reduction efficiency of hexavalent chromium by the three strains combined with exosomes are shown in Table 1. Figure 3 and Figure 4 .

[0064] Table 1: Comparison of the reduction efficiency of hexavalent chromium by three strains combined with exosomes

[0065]

[0066] Definition of unit efficiency: The percentage (%) of hexavalent chromium reduction per unit time (72 hours) to the initial concentration

[0067] From Table 1, Figure 3 and Figure 4 It can be seen that when the pH value was 7 and the growth temperature was 34℃, when HBELNs were added alone, the growth curves of the blank group and the group treated with HBELNs alone overlapped in the 0-12h period, while the growth curves of the group treated with HBELNs alone were higher than those of the control group in the 12h-72h period, and the OD value reached the maximum value at about 60h of culture ( Figure 3 When HBELNs were exogenously added to LB medium containing 110 mg / L Cr(VI), the growth curve of the bacterial strain LYB-S was higher than that of the treatment group without HBELNs, and the two growth curves intersected at 60 hours. When the acclimated strain LYB-S was subjected to 200 and 300 mg / L Cr(VI) stress, its OD value reached its maximum within 24 hours and remained at a low level. Specifically, under optimal growth conditions, the acclimated strain LYB-S achieved 98.25%, 78.38%, and 67.31% reduction efficiencies for 100, 200, and 300 mg / L Cr(VI), respectively, within 72 hours. After exogenous addition of HBELNs, the reduction efficiency of acclimated LYB-S for 100, 200, and 300 mg / L Cr(VI) reached 98.70%, 84.0%, and 71.24%, respectively, which were increased by 0.46%, 6.70%, and 5.80% ( Figure 4 ).

[0068] The highland barley exosomes (HBELNs) extracted from the roots of highland barley seedlings by ultracentrifugation in Example 2 were taken, and the Bacillus Velezii LYB-S preserved in Example 1 was inoculated into LB culture medium containing 0 mg / L, 110 mg / L, 110 mg / L+HBELNs (5%), 200 mg / L and 300 mg / L Cr (VI), respectively, and cultured at 34°C and pH 7.

[0069] Bacterial morphological analysis

[0070] (1) SEM analysis

[0071] Scanning electron microscope images show ( Figure 5Middle B) When the acclimated strain LYB-S was subjected to Cr(VI) stress alone, irregular depressions and wrinkles appeared on its surface, and the bacterial length was significantly shortened. At a Cr(VI) concentration of 200 mg / L, the acclimated strain LYB-S was severely dried and shrunk, with the entire bacterial body covered in wrinkles. When exogenous HBELNs were added to the treatment containing 110 mg / L Cr(VI), the length of the acclimated strain LYB-S did not change significantly compared to the treatment with 110 mg / L Cr(VI) alone, but the surface also showed irregular depressions and wrinkles.

[0072] (2) FTIR and XRD analysis

[0073] Under high concentration Cr(VI) stress, the peak shapes of -OH, CH, amide group, and C-OH in the domesticated strain LYB-S changed ( Figure 5 Figure A). When the acclimated strain LYB-S was subjected to Cr(VI) stress at concentrations of 0 and 200 mg / L, the stretching vibration position of OH shifted from 3434.03 cm －1 Transfer to 3443.40 cm －1 The stretching vibration positions of OH in the treatment group containing 110 mg / L Cr(VI) and the treatment group without HBELNs were 3419.57 cm －1 and 3444.13 cm －1 , occurred -24.56 cm －1 XRD analysis results showed that the domesticated strain did not produce different types of crystals after reduction with HBELNs and different concentrations of Cr(VI), and the peaks that appeared did not correspond to Cr(III) hydroxide crystals, indicating that Cr(III) did not form crystals or the amount of crystallization was too low to form peaks.

[0074] (3) Exogenous addition of HBELNs promoted the OD of the domesticated strain LYB-S. Exogenous HBELNs could significantly improve the Cr(VI) reduction efficiency of the domesticated strain LYB-S.

[0075] (2) Through bacterial morphological and structural analysis, it was found that Cr(VI) stress (200 mg / L) caused the surface of LYB-S bacteria to wrinkle, shorten and dehydrate. After adding HBELNs (110 mg / L Cr(VI) treatment group), the length of the bacteria did not change significantly, but irregular depressions still existed on the surface. Cr(VI) stress (200 mg / L) caused the surface of LYB-S bacteria to wrinkle, shorten and dehydrate. After adding HBELNs (110 mg / L Cr(VI) treatment group), the length of the bacteria did not change significantly, but irregular depressions still existed on the surface. FTIR and XRD analysis showed that Cr(VI) stress caused the peak positions of -OH, CH and amide groups of strain LYB-S functional groups to shift. After exogenous addition of HBELNs, the -OH peak position shifted. Morphological and structural analysis showed that Cr(VI) stress caused the bacterial morphology to shift.

[0076] Those skilled in the art should understand that the method of the present invention is not limited to the embodiments described in the specific embodiments. The above specific description is only for the purpose of explaining the present invention and is not intended to limit the present invention. Those skilled in the art may derive other embodiments based on the technical solution of the present invention, which also fall within the scope of the technical innovation of the present invention. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A strain of Bacillus velezinoffii ( Bacillus velezensis ) LYB-S was deposited in the General Microbiology Center of China Culture Collection of Microorganisms on May 6, 2025, with the deposit number CGMCC NO.34429. The depository address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

2. The Bacillus Velezii according to claim 1 ( Bacillus velezensis ) The use of LYB-S in combination with exosomes to improve the hexavalent chromium reduction rate is characterized by: The concentration of hexavalent chromium is 100-350 mg / L; the exosomes are highland barley exosomes; The preparation steps of highland barley exosomes are as follows: 1) Sample pretreatment The barley roots were cut and separated with a scalpel, washed with distilled water and then the surface water was filtered to obtain the sample; The sample was minced and soaked in 75wt% alcohol for 1 min. After washing with distilled water to remove the alcohol residue, it was dried with sterile paper and enzymatically hydrolyzed at 50°C for 6 h. The sample was then centrifuged at 10,000 rpm for 1 h to allow the enzymatic residue to settle. The supernatant was passed through a cell sieve and the filtrate was collected to obtain the highland barley root sample. 2) Extraction of highland barley exosomes by ultracentrifugation After rapidly thawing highland barley root samples at 37°C, they were centrifuged at 4°C at 2,000 × g for 30 min. The supernatant was collected at 10,000 × g for 45 min, large vesicles removed, and filtered through a 0.45 μm membrane. The filtrate was subjected to ultracentrifugation, the supernatant discarded, and 10 mL of the resulting liquid was pre-cooled and resuspended in PBS before centrifugation under the same conditions. The final precipitate was resuspended in 150 μL PBS, aliquoted, and 20 μL was used for electron microscopy and 10 μL for particle size analysis. RNA was extracted from the remaining sample to obtain highland barley exosomes. In the sample pretreatment step, the enzyme solution contains 4% by mass of cellulase, 2% by mass of pectinase, 0.6 mol / L of mannitol, the balance being water, and a pH value of 5.8; the ultracentrifugation conditions are: 100,000 × g, 4° C., 70 min.

3. Bacillus velezinoffii ( Bacillus velezensis ) A method for improving the hexavalent chromium reduction rate by combining LYB-S with exosomes, characterized in that The following steps are involved: 1) preparing exosomes, wherein the exosomes are highland barley exosomes; The preparation steps of highland barley exosomes are as follows: 1-1) Sample pretreatment The barley roots were cut and separated with a scalpel, washed with distilled water and then the surface water was filtered to obtain the sample; The sample was minced and soaked in 75wt% alcohol for 1 min. After washing with distilled water to remove the alcohol residue, it was dried with sterile paper and enzymatically hydrolyzed at 50°C for 6 h. The sample was then centrifuged at 10,000 rpm for 1 h to allow the enzymatic residue to settle. The supernatant was passed through a cell sieve and the filtrate was collected to obtain the highland barley root sample. 1-2) Extraction of highland barley exosomes by ultracentrifugation After rapidly thawing highland barley root samples at 37°C, they were centrifuged at 4°C at 2,000 × g for 30 min. The supernatant was collected at 10,000 × g for 45 min, large vesicles removed, and filtered through a 0.45 μm membrane. The filtrate was subjected to ultracentrifugation, the supernatant discarded, and 10 mL of the resulting liquid was pre-cooled and resuspended in PBS before centrifugation under the same conditions. The final precipitate was resuspended in 150 μL PBS, aliquoted, and 20 μL was used for electron microscopy and 10 μL for particle size analysis. RNA was extracted from the remaining sample to obtain highland barley exosomes. In the sample pretreatment step, the enzyme solution contains 4% by weight of cellulase, 2% by weight of pectinase, 0.6 mol / L of mannitol, the balance being water, and a pH value of 5.8; the ultracentrifugation conditions are: 100,000 × g, 4°C, 70 min; 2) the exosomes prepared in step 1) are mixed with the Bacillus velezensis described in claim 1 ( Bacillus velezensis ) LYB-S is combined to improve the hexavalent chromium reduction rate; the hexavalent chromium concentration is 100-350 mg / L.

4. The method according to claim 3, wherein The specific steps of step 2) are as follows: Bacillus velez ( Bacillus velezensis ) LYB-S was activated, and then the Velez-Bacillus ( Bacillus velezensis ) LYB-S bacterial suspension; then the Bacillus Velezii ( Bacillus velezensis ) The bacterial suspension of LYB-S is added to the LB medium containing exosomes and hexavalent chromium for cultivation, that is, the hexavalent chromium is reduced, thereby improving the reduction rate of hexavalent chromium.

5. The method according to claim 3, wherein: Contains Bacillus velezensis ( Bacillus velezensis ) The concentration of LYB-S bacterial suspension was 10^8 CFU / mL; the concentration of highland barley exosomes was 50 μg / mL; the concentration of Bacillus velezensis ( Bacillus velezensis ) The volume ratio of LYB-S bacterial suspension to highland barley exosomes was 1:

2.

6. The method according to claim 3, wherein: The culture temperature in LB medium was 34°C, the pH value was 7, and the culture time was more than 12 hours.

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