Comamonas S1-158 and application thereof

Abstract

The invention discloses comamonas sp. S1-158 and application of the comamonas sp. S1-158. The strain S1-158 is a new comamonas sp. Strain capable of efficiently synthesizing volatile selenium, and the preservation number of the strain S1-158 is GDMCC No: 63731. The comamonas S1-158 has high tolerance to selenate, selenite and elemental selenium, the selenite, the elemental selenium and the like can be efficiently converted into volatile selenium, a method for preparing a large amount of methyl selenic acid through a bioreactor is established, the comamonas S1-158 can be used for treatment of selenium-containing wastewater and bioremediation of selenium-polluted environments, and the comamonas S1-158 has good application prospects. The application prospect is wide.

Description

Technical Field

[0001] The invention relates to the technical field of microbiology and selenium-polluted environment restoration, and in particular to a Comamonas S1-158 strain and application thereof. Background Art

[0002] Selenium (Se), as an essential trace element for humans and animals, is crucial for maintaining a variety of physiological functions of organisms. However, there is an extremely narrow boundary between the bioavailability and toxicity of selenium, which makes excessive intake of selenium a potential risk of selenium poisoning. Environmental selenium pollution poses a major threat to ecosystems and human health. Industrial activities, especially the mining of coal and phosphate, metallurgy, and the production and processing of selenium products, are the main sources of environmental selenium pollution. If selenium-containing wastewater generated by industrial activities is discharged directly into the environment without treatment, it will aggravate this problem. At present, chemical flocculation and biological reduction methods are mainly used to treat selenium-contaminated wastewater. The chemical flocculation method removes selenate (Se(VI)) and selenite (Se(IV)) by co-precipitation with selenium oxide using zero-valent iron, iron salts, etc., but it will produce selenium-containing chemical sludge that is difficult to treat. The biological reduction principle reduces selenium oxides to low-toxic elemental selenium through microorganisms, but the generated elemental selenium mostly exists in the form of colloidal selenium nanoparticles (SeNPs), which are difficult to settle in water and are toxic to aquatic organisms. The precipitated SeNPs form a new source of selenium pollution in the sludge and require secondary treatment.

[0003] Recent studies have found that specific microorganisms can convert selenium compounds such as selenite and selenate into volatile organic selenium, such as dimethyl selenium (DMSe), dimethyl diselenide (DMDSe), and dimethyl selensulfur (DMSeS) through a methylation process, thereby transferring selenium in soil and water environments to the atmosphere. Currently reported selenium volatile microorganisms include Escherichia coli, Staphylococcus aureus, Bacillus sp. LHVE, Pseudomonas stutzeri NT-1, Pseudomonas tolaasii, and Stenotrophomonas bentonitica. CN115975881A discloses a new species of selenium volatile colorless bacteria (Achromobacterseleniivolatilans), which can convert selenium compounds in wastewater into volatile selenium, and recover it in the form of methylselenoic acid through a tail gas capture device, providing a new idea for selenium pollution environmental management and resource processing. However, compared with elemental selenium-synthesizing bacteria, the types and numbers of selenium-volatile bacteria discovered so far are relatively small.

[0004] Comamonas belongs to the family Comamonadaceae and the order Burkholderiales, and currently has 28 officially published species. Among them, the aerobic bacterium Comamonas testosteroni S44 strain showed tolerance to 100mM Se(IV) and was able to reduce Se(VI) and Se(IV) to nano-selenium with a size of 100–200nm. Related studies revealed its selenium reduction mechanism and nano-selenium stabilization mechanism (Tan et al., 2018; Xu et al., 2018). Although Comamonas has shown great potential in selenium reduction, there are currently no reports on the synthesis of volatile selenium by microorganisms of this genus. The present invention aims to provide a new species of Comamonas with selenium volatilization ability, and utilizes the biological methylation pathway of the strain to convert selenium compounds such as Se(IV) and SeNPs into volatile selenium, which can not only achieve effective treatment of selenium-contaminated wastewater and promote the recycling of selenium resources, but also provide a new strategy for the development of the anticancer drug methylselenoic acid. Summary of the invention

[0005] The purpose of the present invention is to provide a new species of Comamonas S1-158 strain capable of efficiently synthesizing volatile selenium and its application in the restoration of selenium-polluted environment and the preparation of methylselenoic acid.

[0006] In order to achieve the purpose of the present invention, in the first aspect, the present invention provides a strain of Comamonas S1-158 isolated and purified from soil, classified and named Comamonas sp., which has been deposited in the Guangdong Microbiological Culture Collection Center (GDMCC), address: 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou City, Guangdong Province, Institute of Microbiology, Guangdong Academy of Sciences, Postal Code 510070, Deposit Number GDMCC No: 63731, Deposit Date August 11, 2023.

[0007] In a second aspect, the present invention provides the use of Comamonas S1-158 in the remediation of selenium-contaminated environments and the preparation of methylselenoic acid.

[0008] In a third aspect, the present invention provides a method for biosynthesis of nano-selenium, wherein Comamonas sp. S1-158 is inoculated into a culture medium supplemented with sodium selenite and / or sodium selenate, and after culturing for a period of time, nano-selenium is separated and purified from the culture medium.

[0009] Furthermore, in the culture medium added with sodium selenite and / or sodium selenate, the initial sodium selenate concentration is 100-200 mM, the initial sodium selenite concentration is 1-20 mM, and preferably the initial selenium concentration is 5 mM sodium selenite.

[0010] In a fourth aspect, the present invention provides a method for synthesizing volatile selenium, wherein Comamonas sp. S1-158 is inoculated into a culture medium supplemented with sodium selenite and / or nano-selenium, and after culturing for a period of time, the generated volatile selenium is collected.

[0011] The volatile selenium includes, but is not limited to, dimethyldiselenide, dimethylselenone, triselenothane, dimethylselenothane and the like, mainly dimethyldiselenide and dimethylselenone.

[0012] Furthermore, in the culture medium added with sodium selenite and / or nano-selenium, the initial selenium concentration is 10-400 mg / L, preferably the initial selenium concentration is 10, 20 or 40 mg / L.

[0013] Furthermore, the culture medium may be LB or TSB culture medium.

[0014] Furthermore, the culture conditions were: 28°C, 150 rpm.

[0015] In a fifth aspect, the present invention provides application of the method in the preparation of methylselenic acid.

[0016] The volatile selenium produced according to the method is introduced into a capture liquid containing an oxidant, so that the volatile selenium (such as dimethyl diselenide and dimethyl selenone) is oxidized into water-soluble methylselenoic acid.

[0017] Furthermore, the oxidant includes but is not limited to nitric acid or hydrogen peroxide.

[0018] By means of the above technical solution, the present invention has at least the following advantages and beneficial effects:

[0019] The Comamonas sp. S1-158 of the present invention has strong tolerance to selenate, selenite and elemental selenium, can efficiently convert selenite and elemental selenium into volatile selenium, and a method for preparing methylselenic acid using a bioreactor is established. The method can be used for the treatment of selenium-containing wastewater and the bioremediation of selenium-polluted environments, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The colony (a) and bacterial cell (b) morphological characteristics of strain S1-158 in a preferred embodiment of the present invention.

[0021] Figure 2This is a phylogenetic tree of the 16S rRNA gene of strain S1-158 in a preferred embodiment of the present invention. The evolutionary tree was constructed using the maximum likelihood method, and the model was Kiruma's 2-parametermodel. The numbers at the branches represent 1000 Bootstrap values. The Bootstrap values ​​greater than 50% are shown in the figure. The GenBank accession number of the strain 16S rRNA gene sequence is in brackets. The ruler represents the 1% nucleotide substitution rate. Note: In 2023, Acidovorax antarcticus was renamed Comamonasantarctica (Du et al. 2023).

[0022] Figure 3 The whole genome and core gene evolution tree of strain S1-158 in the preferred embodiment of the present invention. a is a phylogenetic tree based on the whole genome constructed using the TYGS tool, the branch length is calculated according to the GBDP evolutionary distance formula d5, the displayed branch value is from 100 GBDPpseudo-bootstrap values, the average branch support rate is 84.8%, and the scale represents 2% nucleotide difference. b is a phylogenetic tree based on 92 single-copy core genes constructed using the UBCG tool, the data at the node represents the gene support index (GSI), and the scale represents 10% nucleotide difference.

[0023] Figure 4 The tolerance and reducing ability of strain S1-158 in the preferred embodiment of the present invention to sodium selenate and sodium selenite.

[0024] Figure 5 The characteristics of the strain S1-158 in the preferred embodiment of the present invention in reducing sodium selenite to synthesize nano-selenium. a is a TEM photo of the strain reducing 5mM Se(IV) to synthesize nano-selenium, b is a photo of the purified nano-selenium, c is the EDS spectrum of the nano-selenium particles indicated by the arrow in the TEM image, and d is the Raman spectrum of nano-selenium.

[0025] Figure 6 The volatilization efficiency of Se(IV) and SeNPs by strain S1-158 in a preferred embodiment of the present invention is shown.

[0026] Figure 7This is the identification (GC-MS) of volatile selenium synthesized by strain S1-158 in the preferred embodiment of the present invention. The peak numbers in the figure indicate volatile selenium and volatile sulfur compounds, 1-dimethyldisulfide, 2-dimethylselenone, 3-dimethyldiselenide, 4-dimethylselenyl sulfide, and 5-triselenothane. DETAILED DESCRIPTION

[0027] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the examples are all based on conventional experimental conditions, such as Sambrook et al. Molecular Cloning Laboratory Manual (Sambrook J & Russell DW, Molecular Cloning: a Laboratory Manual, 2001), or the conditions recommended by the manufacturer's instructions.

[0028] Example 1 Isolation and identification of Comamonas S1-158 strain

[0029] 1. Strain isolation: Soil was collected from the rhizosphere of Cardamine hupingensis, a selenium hyperaccumulator in Yutangba, Enshi, Hubei. 5 g of soil was added with 95 mL of sterile saline, and the soil was shaken at 25°C and 150 rpm for 30 min. After 10-fold gradient dilution, 100 μL was spread on a NA plate with 10 mM sodium selenite, and cultured at 28°C for 2 days to obtain a sodium selenite-tolerant strain, which was purified by zoning and streaking. A Gram-negative bacterium S1-158 strain capable of synthesizing volatile selenium was isolated from the soil.

[0030] 2. Analysis of colony and bacterial morphology: Gram staining of strain S1-158 was negative. When cultured on TSA medium at 28°C for 2 days, the colonies were round, 1–2 mm in diameter, with a moist and shiny surface, neat edges, and no pigment ( Figure 1 a). TEM observations showed that the bacteria were rod-shaped, 1.7–2.5 μm long, 1.0–1.5 μm wide, and had flagella ( Figure 1 b) It is motile and produces swimming circles on semi-solid culture medium.

[0031] 3. Phylogenetic analysis of 16S rRNA gene: The genomic DNA of strain S1-158 was extracted using a bacterial DNA extraction kit, and its 16S rRNA gene was amplified using universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R (5'-GGTTACCTTGTTACGACTT-3'). The PCR product was purified and sequenced, and the sequencing results were spliced ​​using DNAMAN software (SEQ ID NO: 1). The 16S rRNA gene similarity was compared using the EzBioCloud analysis platform (www.ezbiocloud.net / ). The results showed that strain S1-158 had the highest similarity with strains of Acidovorax, Comamonas, and Delftia, among which Comamonasantarctica 16-35-5 T The similarity with the other strains was the highest, reaching 98.87%, while the similarities with the other strains were all lower than 98.7%.

[0032] The 16S rRNA gene phylogenetic tree of strain S1-158 and its closely related bacterial genera was constructed using MEGA software. The results showed that strain S1-158 and Comamonas antarctica 16-35-5 T , Comamonas granuli NBRC 101663 T and multiple strains of Acidovorax spp. clustered on one branch ( Figure 2 ). However, effective differentiation of Acidovorax, Delftia, and Comamonas strains cannot be achieved using the 16S rRNA gene alone, and further analysis of genome sequences is required.

[0033] 4. Genome sequencing and genome similarity analysis: The whole genome of strain S1-158 was sequenced using the Illumina NovaSeq platform, and the genome size was measured to be 6.39 Mb, with a G+C content of 65.0 mol% (Table 1). The genome-based species identification results conducted by the Model (Strain) Genome Server (TYGS, https: / / tygs.dsmz.de) showed that strain S1-158 was a potential new species. The average nucleotide similarity (ANI) between strain S1-158 and closely related bacteria such as Acidovorax, Comamonas and Delftia was calculated using JSpeciesWS (https: / / jspecies.ribohost.com / jspeciesws / #analyse), and the digital DNA-DNA hybridization (dDDH) was calculated using GGDC Calculator 3.0 (http: / / ggdc.dsmz.de). The results showed that strain S1-158 had a similar genome structure to Comamonasantarctica 16-35-5 T and Comamonas endophytica 5MLIR T The genome similarity of S1-158 was the highest, with ANI values ​​of 85.1% and 84.6%, and dDDH values ​​of 30.3% and 29.5%, respectively (Table 2), which were all lower than the species threshold (ANI = 95-96%, dDDH = 70%), indicating that S1-158 was a new species of Comamonas.

[0034] Table 1 Sequence information used for genome analysis and ANI and dDDH values ​​of strain S1-158 and its closely related bacteria

[0035]

[0036] 5. Genome phylogenetic analysis: The whole genome phylogenetic tree constructed using TYGS showed that strain S1-158 was similar to Comamonas antarctica 16-35-5 T and Comamonas endophytica 5MLIR T Gathered in a small branch ( Figure 3a). The UBCG tool (www.ezbiocloud.net / tools / ubcg) was used to extract 92 common single-copy core genes in the genome and draw a phylogenetic tree of the concatenated sequences. It also showed that strain S1-158 belonged to the genus Comamonas and was closely related to Comamonasantarctica 16-35-5 T and Comamonas endophytica 5MLIR T The closest relative ( Figure 3 b).

[0037] 6. Stress resistance experiment of strain S1-158

[0038] The strain S1-158 was inoculated on TSA plates and cultured at 4, 10, 20, 28, 30, 32, 34, 37, 40 and 42°C for 4 days to observe the growth of the strain. 1, 2, 3, 4, 5, 6, 7, 8% (w / v) NaCl was added to the TSB medium to prepare a salt-containing medium. After inoculating the strain S1-158, the medium was shaken at 28°C and 150rpm for 4 days to observe the growth. The pH values ​​of the TSB culture solution were adjusted to 4, 5, 6, 7, 8, 9, 10, and 11 with HCl (6M) and NaOH (2M). After inoculating the strain S1-158, the medium was shaken at 28°C and 150rpm for 4 days to observe the growth. The results showed that the strain S1-158 had a higher stress resistance than the closely related bacteria, with a growth temperature range of 4-37°C and a growth pH range of 6-11, and could tolerate 5% NaCl (Table 2).

[0039] 7. Physiological and biochemical index determination: strain S1-158 grows facultatively anaerobic, is positive for oxidase and catalase, and negative for hemolysis. API 20NE identification results show that strain S1-158 reduces nitrate, is negative for arginine dihydrolase, urease, and β-galactosidase, does not synthesize indole, does not hydrolyze esculin or gelatin, and does not ferment glucose; it can utilize gluconate, adipic acid, and malic acid, but does not utilize glucose (D-glucose), arabinose (L-arabinose), mannose (D-mannose), mannitol (D-mannitol), N-acetyl-β-glucosamine (N-acetyl-glucosamine), maltose (D-maltose), capric acid (capric), citric acid (citrate), and phenylacetic acid (phenylacetic acid). API ZYM identification results showed that C4 esterase, C8 lipid esterase, leucine aminopeptidase, acid phosphatase, and naphthol-AS-Bl-phosphamidase were positive.

[0040] In addition, the closely related fungus Comamonas antarctica 16-35-5 T and Comamonas endophytica5MLIR T In comparison, strain S1-158 differed in the following parameters: growth temperature and pH range, salt tolerance, nitrate reduction, utilization of carbon sources such as glucose, gluconate, adipic acid, and malic acid, and alkaline phosphatase activity ( Table 2 ).

[0041] Table 2 Differential physiological and biochemical characteristics of strain S1-158 and related species

[0042]

[0043] Based on the above 16S rRNA gene and genome phylogenetic analysis as well as morphological characteristics and physiological and biochemical properties, strain S1-158 was identified as a new species of the genus Comamonas, and has been deposited in Guangdong Microbial Culture Collection (GDMCC) with the deposit number GDMCC No: 63731.

[0044] Example 2 Tolerance and reduction of selenate and selenite by strain S1-158

[0045] Prepare TSA solid medium (BD Bacto), wait for it to cool to about 60°C, add filter-sterilized sodium selenate and sodium selenite solutions, shake gently to mix, and pour on the plate to prepare a selenium-containing plate containing 0-200mM sodium selenate and 0-100mM sodium selenite. Pick a single colony of strain S1-158 and inoculate it into a TSB test tube (BD Bacto), shake and incubate at 28°C and 150rpm for 12h for activation, and adjust the bacterial solution OD 600 The concentration of 0.8 was used as the seed solution. After 10-fold gradient dilution with sterile saline, 2.5 μL of each gradient was added dropwise to the selenium-containing plate. After being blown dry with sterile air, it was cultured at 28°C for 4 days to observe the growth of the strain.

[0046] Results Figure 4 The growth on selenium-containing plates showed that S1-158 could tolerate at least 200 mM selenate and 20 mM selenite, and the colonies on the selenite plates were bright red, indicating the production of red elemental selenium. On the selenate plates, the colonies synthesized red elemental selenium only at high concentrations (100–200 mM). Figure 4 ).

[0047] Example 3 Characteristic Analysis of the Synthesis of Elemental Selenium by Strain S1-158

[0048] A single colony of S1-158 was selected and inoculated into an LB tube (5 g / L yeast extract, 10 g / L tryptone, 10 g / L sodium chloride, pH 7.0–7.2, sterilized at 121°C for 20 min), and cultured at 28°C and 150 rpm for 12 h for activation. The bacterial solution OD was adjusted. 600 The inoculum concentration of the strain S1-158 was 0.8, and it was inoculated in an LB shake flask at a 1% inoculation rate. The corresponding volumes of sodium selenite and sodium selenate mother liquor (filtered and sterilized) were added to make the initial sodium selenite concentration 1-5 mM or the sodium selenate concentration 100-200 mM. The strain was placed at 28 ° C and 150 rpm for 2 days. The morphology of the elemental selenium synthesized by the strain S1-158 was observed by transmission electron microscopy (TEM), and the element types of the elemental selenium were analyzed by X-ray energy dispersive spectrometer (EDS). After extraction and purification, the crystal form of the elemental selenium was analyzed by Raman spectrometer.

[0049] The results showed that the elemental selenium synthesized by the reduction of Se(IV) and Se(VI) by strain S1-158 was spherical nanoparticles. The TEM image of the 5 mM sodium selenite treatment group is shown in Figure 5 , the particle size of nano-selenium is distributed in the range of 50-600nm, and the average particle size is distributed in the range of 200-300nm ( Figure 5 , a and b). EDS spectrum analysis of the nanoparticles shown in the figure shows characteristic peaks of selenium at 1.37keV, 11.22keV and 12.50keV, indicating that the nanoparticles synthesized by the strain are nano-selenium ( Figure 5 c). Raman spectrum visible at 253cm -1 The characteristic Raman shift peak of amorphous elemental selenium at , indicating that the crystal form of nano-selenium is amorphous ( Figure 5 d).

[0050] Example 4 Volatilization efficiency of strain S1-158 for Se(IV) and SeNPs

[0051] Pick a single colony of S1-158 and inoculate it into an LB tube. Cultivate it at 28°C and 150 rpm for 12 hours to adjust the OD value of the bacterial solution. 600 0.8, as seed liquid. Inoculate into a shake flask containing 50mL LB culture medium (LB culture medium: yeast extract 5g / L, tryptone 10g / L, sodium chloride 10g / L, pH7.0-7.2, sterilized at 121°C for 20min) according to 1% inoculum, and add the corresponding volume of sodium selenite or chemically synthesized nano-selenium mother solution (filter sterilized) to make the initial selenium concentration 10, 20 and 40mg / L (in terms of Se), respectively, and place at 28°C, 150rpm shaking culture for 4 days. The reduction of total selenium in the bacterial solution after 4 days of culture was measured by atomic fluorescence spectrometer (HG-AFS), and then the selenium volatilization rate was calculated:

[0052] Selenium volatilization rate (%) = (amount of selenium added to the culture solution - remaining amount of selenium in the culture solution) / amount of selenium added to the culture solution × 100%

[0053] The test results showed that after 4 days of cultivation, the total selenium in the culture medium inoculated with S1-158 was greatly reduced, and a strong garlic-like odor was produced during the cultivation process. At a selenium addition of 10 mg / L, the selenium volatilization rates of S1-158 to Se(IV) and SeNPs reached 92.3% and 86.9%, respectively ( Figure 6 ), the volatilization amount of SeNPs by the strain reached the highest level at 20 mg / L, which was 15.4 mg (per liter of culture fluid), while the volatilization amount of Se(IV) by the strain reached the highest level at 40 mg / L, which was 23.4 mg (per liter of culture fluid) ( Figure 6 ).

[0054] Example 5 Identification of the types of volatile selenium synthesized by strain S1-158

[0055] LB culture medium was added to the headspace bottle, and 40 mg / L of Se(IV) and SeNPs were added respectively. S1-158 seed solution was inoculated and cultured for 4 days. The headspace gas was measured by GC-MS to identify the types of volatile selenium. The results showed that the volatile selenium species synthesized by S1-158 from the two inorganic selenium species Se(IV) and SeNPs included dimethyldiselenide, dimethylselenone, dimethyl selenyl sulfide and triselenothane. The volatile sulfur compound dimethyldisulfide ( Figure 7 Among them, dimethyl diselenide and dimethyl selenone have the highest abundance ( Figure 7 ).

[0056] The methylation process is a key detoxification mechanism in organisms. The methylation process of selenium helps reduce the biological toxicity of selenium compounds and prevents excessive selenium from participating in biological activities such as protein synthesis. In addition, in the biogeochemical cycle of selenium, microorganisms with selenium volatilization ability convert selenate, selenite and elemental selenium into volatile selenium compounds through methylation, thereby transferring selenium in soil and water bodies to the atmosphere, preventing these selenium from entering the food chain and food web, and is a key link in the biogeochemical cycle of selenium.

[0057] Example 6 Removal of Se(IV) and SeNPs and Preparation of Methylselenoic Acid in a Bioreactor Using Strain S1-158

[0058] Pick a single colony of strain S1-158 and inoculate it into an LB test tube. After activation at 28°C and 150rpm for 12h, inoculate 1% to a 70mL LB shake flask, and prepare shake flask seeds at 28°C and 150rpm for 8h. Add 7LLB culture medium to a 10L fermenter, sterilize at 121°C for 20min, wait until the temperature drops to 28°C, access 70mL seed solution, and access 14mL Se(IV) mother solution (10g / L, in terms of Se) and 14mL SeNPs mother solution (10g / L, in terms of Se) to make the fermentation liquid contain 20mg(Se) / L of Se(IV) and SeNPs, respectively. Connect the tail gas pipeline to the buffer bottle, the gas washing bottle and the tail gas absorption bottle, and fill the absorption bottle with concentrated nitric acid to capture the volatile selenium in the tail gas. Control the fermentation temperature at 28±0.5°C, the stirring speed at 150rpm, the ventilation at 210L / h, and ferment for 24h. The residual selenium content in the fermentation broth was determined by atomic fluorescence spectrometry (HG-AFS).

[0059] The results showed that as the fermentation time increased, the bacteria grew rapidly, the dissolved oxygen in the fermentation broth decreased, the pH increased, and the Se(IV) and SeNPs in the fermentation broth were rapidly converted into volatile selenium and removed from the aqueous phase. The selenium volatilization rate in 24 hours reached 88%, and the tail gas capture device recovered 80% of the total selenium, and the capture rate of volatile selenium gas reached 91%. The selenium form in the capture liquid was identified by high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS), and it was found that the selenium compounds in the capture liquid were mainly methylselenic acid (MSA). The study showed that dimethyl selenone can be oxidized to dimethyl diselenide, and in the nitric acid capture liquid, the oxidation product of dimethyl diselenide is MSA, which is consistent with the results of GC-MS.

[0060] MSA is a drug with significant anti-cancer effects. It can be converted into methylselenol in vivo through the action of reducing agents such as glutathione. It has selective cytotoxicity to a variety of cancer cells and can effectively inhibit the proliferation of cancer cells such as lung cancer, breast cancer, esophageal cancer and prostate cancer. Therefore, by culturing high-efficiency selenium volatile strains such as S1-158 on a large scale in a bioreactor, selenium compounds such as selenate, selenite and elemental selenium can be converted into volatile selenium, such as dimethyl diselenide and dimethyl selenone, by using its biotransformation process. By adding oxidants such as nitric acid or hydrogen peroxide as capture liquids in the tail gas treatment device, dimethyl diselenide and dimethyl selenone are oxidized to water-soluble methyl selenoic acid. This technology not only helps the bioremediation of selenium-contaminated environments, but also provides new ideas for the production of methyl selenoic acid, and has important application potential in the fields of environment and medicine.

[0061] Example 7 Using strain S1-158 to reduce the selenium accumulation of plants in high-selenium soil

[0062] In high-selenium soil, by applying the strain S1-158 bacterial agent, Se(VI) and Se(IV) in the soil are converted into nano-selenium and / or volatile selenium through the strain's biological reduction and methylation process, thereby reducing the accumulation of selenium in plants, improving the tolerance of plants to high-selenium environments, and reducing the selenium content entering the food chain, reducing the risk of selenium poisoning in humans and animals in high-selenium areas.

[0063] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. Comamonas sp. S1-158, deposit number GDMCC No: 63731.

2. Use of the Comamonas described in claim 1 in the remediation of selenium-contaminated environments and the preparation of methylselenoic acid.

3. A method for biosynthesis of nano-selenium, characterized in that: The Comamonas described in claim 1 is inoculated into a culture medium supplemented with sodium selenite and / or sodium selenate, and after culturing for a period of time, nano-selenium is separated and purified from the culture solution.

4. The method according to claim 3, characterized in that In the culture medium added with sodium selenite and / or sodium selenate, the initial sodium selenate concentration is 100-200 mM, the initial sodium selenite concentration is 1-20 mM, and preferably the initial selenium concentration is 5 mM sodium selenite.

5. A method for synthesizing volatile selenium, characterized in that: Inoculating the Comamonas described in claim 1 into a culture medium supplemented with sodium selenite and / or nano-selenium, culturing for a period of time, and collecting the generated volatile selenium; The volatile selenium includes dimethyl diselenide, dimethyl selenone, triselenoheterocyclohexane, and dimethyl selensulfide.

6. The method according to claim 5, characterized in that In the culture medium added with sodium selenite and / or nano-selenium, the initial selenium concentration is 10-400 mg / L, preferably the initial selenium concentration is 10, 20 or 40 mg / L.

7. The method according to any one of claims 3 to 6, characterized in that: The culture medium is LB or TSB culture medium; Culture conditions: 28°C, 150 rpm.

8. Use of the method according to any one of claims 5 to 7 in the preparation of methylselenic acid.

9. The use according to claim 8, characterized in that: The volatile selenium produced by the method according to any one of claims 5 to 7 is introduced into a capture liquid containing an oxidant, so that the volatile selenium is oxidized into water-soluble methylselenic acid.

10. The use according to claim 9, characterized in that: The oxidizing agent includes nitric acid or hydrogen peroxide.

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