Methylobacterium sp. capable of degrading 2,4-dichlorophenoxyacetic acid and application thereof

Abstract

The application discloses a stenotrophomonas maltophilia capable of degrading 2,4-dichlorophenoxyacetic acid, and a stenotrophomonas maltophilia strain GDUTXIONG3 is screened, wherein the strain GDUTXIONG3 is preserved in the China Center for Type Culture Collection on October 26, 2022, and the preservation number is CCTCC NO: M 20221673. The application discloses, for the first time, the degradation effect of the stenotrophomonas maltophilia on 2,4-dichlorophenoxyacetic acid, and the degradation rate of the strain on 50 mg / L of 2,4-dichlorophenoxyacetic acid can reach 82.9% or more within 96 hours. The GDUTXIONG3 strain is pollution-free and harmless in use, and can be used for repairing and treating an environment polluted by 2,4-dichlorophenoxyacetic acid.

Description

Technical Field

[0001] This invention belongs to the field of microbial degradation technology. More specifically, it relates to a strain of Stenotrophomonas maltophilia that degrades 2,4-dichlorophenoxyacetic acid and its applications. Background Technology

[0002] 2,4-Dichlorophenoxyacetic acid (2,4-D) is a phenoxycarboxylic acid herbicide and also a synthetic plant growth regulator. As a herbicide, 2,4-dichlorophenoxyacetic acid is widely used in agricultural production, such as weed control in rice paddies, forests, and lawn maintenance. In recent years, the use of 2,4-dichlorophenoxyacetic acid has increased year by year. Due to its low adsorption and high water solubility, 2,4-dichlorophenoxyacetic acid sprayed on the ground can penetrate into various media such as water bodies, sediments, and soil. Toxicological studies have shown that 2,4-dichlorophenoxyacetic acid has teratogenic, carcinogenic, mutagenic, and neurotoxic risks; even exposure to low concentrations can cause potentially significant harm to human health over long-term accumulation.

[0003] Biological degradation utilizes the metabolic activity of microorganisms to degrade 2,4-dichlorophenoxyacetic acid in the environment. It offers advantages such as no secondary pollution, high processing capacity, low operating costs, and good purification effects. Currently, there are relatively few microbial strains suitable for biological degradation of 2,4-dichlorophenoxyacetic acid. Existing technologies have only reported the following strains: *Flav obacterium*, *Acinetobacter calcoaceticus*, *Alcaligenes denitrificans*, *Pseudomonas glycinea*, *Bacillus sp.*, *Corynebacterium*, and *Pseudomonas sp.*.

[0004] To date, there are few reports on other microbial strains that can be used for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-dichlorophenoxyacetic acid). Therefore, discovering more 2,4-dichlorophenoxyacetic acid-degrading bacteria with better degradation capabilities and applying them to contaminated environments to effectively reduce the levels of harmful pollutants can provide more options for the biological degradation of 2,4-dichlorophenoxyacetic acid. However, due to differences in the genetic characteristics and metabolic activities of degrading microorganisms, the degradation efficiency varies significantly among different bacteria. Therefore, obtaining degrading microorganisms with efficient and stable degradation activity for 2,4-dichlorophenoxyacetic acid is a current challenge and a key focus for the green remediation of 2,4-dichlorophenoxyacetic acid pesticide residue pollution. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a strain of Stenotrophomonas maltophilia that degrades 2,4-dichlorophenoxyacetic acid, which can rapidly and efficiently degrade 2,4-dichlorophenoxyacetic acid and can be used to remediate soil, water bodies, and other environments contaminated with 2,4-dichlorophenoxyacetic acid.

[0006] The first objective of this invention is to provide a Stenotrophomonas maltophilia strain GDUTXIONG3 that degrades 2,4-dichlorophenoxyacetic acid.

[0007] A second objective of this invention is to provide the use of Stenotrophomonas maltophilia strain GDUTXIONG3 or its bacterial suspension in the degradation of 2,4-dichlorophenoxyacetic acid.

[0008] A third objective of this invention is to provide the use of Stenotrophomonas maltophilia strain GDUTXIONG3 or a suspension thereof in the preparation of products that degrade 2,4-dichlorophenoxyacetic acid.

[0009] A fourth object of the present invention is to provide the application of Stenotrophomonas maltophilia strain GDUTXIONG3 or a suspension thereof in the remediation of environments contaminated with 2,4-dichlorophenoxyacetic acid.

[0010] A fifth object of the present invention is to provide a bacterial agent for the degradation of 2,4-dichlorophenoxyacetic acid.

[0011] A sixth object of the present invention is to provide a method for degrading 2,4-dichlorophenoxyacetic acid or remediating the environment contaminated by it.

[0012] The above-mentioned objective of this invention is achieved through the following technical solution:

[0013] A Stenotrophomonas maltophilia strain GDUTXIONG3 that degrades 2,4-dichlorophenoxyacetic acid was deposited at the China Center for Type Culture Collection on October 26, 2022, with accession number CCTCC NO: M 20221673.

[0014] The inventors isolated and purified a highly efficient degrading bacterium for 2,4-dichlorophenoxyacetic acid (2,4-dichlorophenoxyacetic acid): Stenotrophomonas maltophiliae strain GDUTXIONG3, from sludge of a wastewater treatment plant in Guangzhou, Guangdong Province. The GDUTXIONG3 strain is a Gram-negative bacterium with round, pale yellow, semi-transparent colonies, 0.5–1.0 mm in diameter; the cells are rod-shaped, 0.8–1.0 × 0.2–0.3 μm in size, and have flagella; it grows aerobicly, is negative for oxidase tests, decomposes glucose and maltose, but not xylose or mannitol; glucose OF is oxidized (slowly); gelatin and nitrate reduction tests are positive, and citrate tests are negative. Through extensive experiments and research, the inventors found that the GDUTXIONG3 strain exhibits excellent degradation ability for 2,4-dichlorophenoxyacetic acid, achieving a degradation rate of over 82.9% for 50 mg / L of 2,4-dichlorophenoxyacetic acid within 96 hours. The GDUTXIONG3 strain can be used for the rapid degradation of 2,4-dichlorophenoxyacetic acid and can be applied to the remediation and treatment of environments contaminated with 2,4-dichlorophenoxyacetic acid.

[0015] Therefore, the following applications should all fall within the scope of protection of this invention:

[0016] The application of the Stenotrophomonas maltophilia strain GDUTXIONG3 or its bacterial suspension in the degradation of 2,4-dichlorophenoxyacetic acid.

[0017] The application of the Stenotrophomonas maltophilia strain GDUTXIONG3 or its bacterial suspension in the preparation of a product that degrades 2,4-dichlorophenoxyacetic acid. The product can be an inoculum containing the Stenotrophomonas maltophilia strain GDUTXIONG3, or a herbicide containing the Stenotrophomonas maltophilia strain GDUTXIONG3 and conventional formulation components.

[0018] Application of the Stenotrophomonas maltophilia strain GDUTXIONG3 or its bacterial suspension in the remediation of natural environments contaminated with 2,4-dichlorophenoxyacetic acid.

[0019] In addition, this application also claims protection for a bacterial agent for degrading 2,4-dichlorophenoxyacetic acid, comprising the above-mentioned Stenotrophomonas maltophilia strain GDUTXIONG3 or a suspension thereof.

[0020] Preferably, the number of cells in the Stenotrophomonas maltophilia strain GDUTXIONG3 is not less than 1.0 × 10⁻⁶. 6 CFU / mL.

[0021] More preferably, the number of cells in the Stenotrophomonas maltophilia strain GDUTXIONG3 is 1.0–9.0 × 10⁻⁶. 6 CFU / mL.

[0022] In addition, this application also claims protection for a method for degrading 2,4-dichlorophenoxyacetic acid or remediating an environment contaminated by it, the method being treatment using the aforementioned microbial agent.

[0023] Preferably, to achieve better and more stable degradation results, when using the strain GDUTXIONG3 to degrade 2,4-dichlorophenoxyacetic acid or remediate its contaminated environment, the preferred environmental conditions are: a temperature of 25–35°C; more preferably, a temperature of 30–35°C; and most preferably, a temperature of 30°C. Therefore, in practical work, environmental remediation work can be preferably carried out under these temperature conditions.

[0024] Preferably, to achieve a better and more stable degradation effect, when using the strain GDUTXIONG3 to degrade 2,4-dichlorophenoxyacetic acid or remediate its contaminated environment, the environmental conditions are preferably: pH 6-9; more preferably, pH 6.5-7.5; and most preferably, pH 7. Therefore, in practical work, it is preferable to adjust the pH value of the remediation environment or to prepare the degrading agent to this pH range.

[0025] This invention has the following beneficial effects: It discloses for the first time the degradation effect of *Stenotrophomonas maltophilia* on 2,4-dichlorophenoxyacetic acid (2,4-dichlorophenoxyacetic acid), and screened and obtained a *Stenotrophomonas maltophilia* strain GDUTXIONG3 capable of degrading 2,4-dichlorophenoxyacetic acid. This strain exhibits excellent degradation ability for 2,4-dichlorophenoxyacetic acid, achieving a degradation rate of over 82.9% for 50 mg / L of 2,4-dichlorophenoxyacetic acid within 96 hours, classifying it as a highly efficient degrading bacterium. Furthermore, strain GDUTXIONG3 is pollution-free and harmless during use, and can be used to remediate and treat environments contaminated with 2,4-dichlorophenoxyacetic acid. This has significant practical importance and value for the degradation and remediation of 2,4-dichlorophenoxyacetic acid in contaminated environments. Attached Figure Description

[0026] Figure 1 This is a morphological image of strain GDUTXIONG3 under a scanning electron microscope.

[0027] Figure 2 This is a single colony morphology diagram of strain GDUTXIONG3.

[0028] Figure 3 Phylogenetic tree diagram of strain GDUTXIONG3.

[0029] Figure 4 The graph shows the degradation rate of strain GDUTXIONG3 under different initial concentrations of 2,4-dichlorophenoxyacetic acid.

[0030] Figure 5 The graph shows the degradation rate of 2,4-dichlorophenoxyacetic acid in wastewater by strain GDUTXIONG3.

[0031] Figure 6 The graph shows the degradation rate of 2,4-dichlorophenoxyacetic acid in soil by strain GDUTXIONG3.

[0032] Figure 7 The graph shows the degradation efficiency of 2,4-dichlorophenoxyacetic acid by strain GDUTXIONG3 under different pH conditions.

[0033] Figure 8 The graph shows the degradation efficiency of 2,4-dichlorophenoxyacetic acid by strain GDUTXIONG3 under different temperature conditions. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are preferred embodiments of the present invention, but do not limit the scope of protection of the present invention in any way. The present invention mainly describes the strain and the application ideas based on the strain. Simple parameter substitutions in the embodiments cannot be fully described in all examples, but this does not limit the present invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and should be included within the scope of the present invention.

[0035] Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0036] The culture medium formulations described in the following examples are as follows:

[0037] The inorganic salt culture medium formulation used in the following examples is as follows: phosphate buffer solution: K₂HPO₄·H₂O 1.75 g / L, NaHPO₄·12H₂O 3.40 g / L, KH₂HPO₄ 1.5 g / L; MgSO₄ solution: MgSO₄ 1.5 g / L; CaCl₂ solution: 1.4 g / L; FeCl₃ solution: FeCl₃·6H₂O 0.25 g / L, MnSO₄·H₂O 0.9 mg / L; trace element solution: ZnSO₄·H₂O 0.8 mg / L, (NH₄)₆Mo₇O 24 ·4H2O 0.7mg / L.

[0038] The solid culture medium formula is: beef extract 3.0 g / L, peptone 10.0 g / L, NaCl 5.0 g / L.

[0039] The liquid culture medium formula is as follows: glucose 5.0 g / L, ammonium tartrate 0.2 g / L, K2HPO4 0.5 g / L, CaCl2 0.1 g, thiamine 1 mg, 10 mmol acetate-ammonium acetate buffer (pH 4.5), and trace element mixture 70 mL.

[0040] Example 1: Isolation and Identification of Strain GDUTXIONG3

[0041] 1. Screening and isolation of Stenotrophomonas maltophilia GDUTXIONG3:

[0042] The sample used in this embodiment was soil from a farmland in Guangzhou City, Guangdong Province. 2,4-Dichlorophenoxyacetic acid (2,4-dichlorophenoxyacetic acid) was used as both a carbon and energy source. A certain amount of 2,4-dichlorophenoxyacetic acid was added to an inorganic salt culture medium for screening. The substrate concentrations for acclimatization were successively 1 mg / L, 5 mg / L, 10 mg / L, 15 mg / L, and 20 mg / L. First, 10 g of contaminated soil was added to an inorganic salt culture medium containing 1 mg / L 2,4-dichlorophenoxyacetic acid and acclimatized at 37°C for 5 days. Then, a 10% inoculum was transferred to the next concentration for further acclimatization, and so on, gradually increasing the concentration for acclimatization.

[0043] After acclimatization, dilute the final concentration of bacterial solution by 10. -1 ~10 -7 times, and select 10 -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 Seven dilutions were prepared, and 0.2 mL of each was evenly spread on a solid culture medium with 2,4-dichlorophenoxyacetic acid as the carbon source. The cultures were then incubated, and single colonies with good growth were selected for further enrichment culture for subsequent identification of the bacterial species.

[0044] 2. Identification of Stenotrophomonas maltophilia GDUTXIONG3:

[0045] The colonies obtained after the enrichment culture were used for species identification, and their morphological characteristics after 24 hours of incubation on solid culture medium were observed under an electron microscope. Figure 1 and Figure 2 The images shown are morphological images of the strain under a scanning electron microscope, and images of single colonies of the strain. Figure 1 and Figure 2 It can be seen that the colony morphology is round, pale yellow, and semi-transparent, with a colony diameter of 0.5–1.0 mm; the bacterial body morphology is rod-shaped, with a size of (0.8–1.0) × (0.2–0.3) μm, and without flagella.

[0046] Next, physiological and biochemical characteristics were identified. The identification process was based on Bergey's Manual of Bacteriological Identification, 8th Edition. The identification results are shown in Table 1 below.

[0047] Table 1 Physiological and biochemical characteristics of bacterial cells

[0048] Gram staining - Anaerobic growth - Oxidase - Nitrate reduction + Simon's citrate utilization - Hydrolyzed gelatin (liquid at 4°C) + Glucose OF utilization + Utilization of arabinose - Mannitol utilization - Xylose utilization -

[0049] Note: The reaction status is divided into positive and negative. Positive shape is coded as "+" and negative shape is coded as "-".

[0050] Molecular biological identification was then performed, and total bacterial DNA was extracted using a DNA extraction kit. Universal primers for bacterial 16S rDNA were used.

[0051] Upstream primer: 27F: 5'-AGAGTTTGATCCTGGCTCAG-3

[0052] Downstream primer: 1492R: 5'-GGTTACCTTGTTACGACTT-3

[0053] The 16S rDNA gene was amplified, and the sequencing results are shown in SEQ ID: No.1. The 1500bp 16S rRNA gene sequence was compared with gene sequences already registered in GenBank, and a phylogenetic tree was constructed. The results are as follows. Figure 3 As shown, comparative analysis revealed that the strain isolated in this invention is most similar to Stenotrophomonas maltophilia strain PaKu7, with a similarity of 100.00%.

[0054] Based on the above morphological characteristics, physiological and biochemical properties, and 16S rRNA gene sequence identification results, the strain isolated in this invention is classified as *Stenotrophomonas maltophilia*, named *Stenotrophomonas maltophilia* GDUTXIONG3, and deposited at the China Center for Type Culture Collection (CCTCC) on October 26, 2022, with accession number CCTCC NO: M 20221673, deposit address: Wuhan University, Wuhan, China.

[0055] Example 2: Degradation test of 2,4-dichlorophenoxyacetic acid by strain GDUTXIONG3

[0056] This embodiment uses Stenotrophomonas maltophiliae GDUTXIONG3, identified in Example 1 above, to study 2,4-dichlorophenoxyacetic acid. First, 100 mL of inorganic salt culture medium was prepared by adding the components of the inorganic salt culture medium formula to an Erlenmeyer flask and autoclaving at 121°C for 30 min. Then, strain GDUTXIONG3 was enriched and cultured in solid culture medium for 18 h. The cells were collected by centrifugation and washed three times with phosphate buffer. A 10% inoculum was then suspended in the Erlenmeyer flask containing 100 mL of inorganic salt culture medium. A certain amount of 2,4-dichlorophenoxyacetic acid solution was added to achieve concentrations of 1 mg / L, 5 mg / L, 25 mg / L, and 50 mg / L, respectively. The culture was then carried out at 37°C and a vibration frequency of 200 rpm for degradation experiments. At 12, 24, 48, 72, and 96 hours, 1 mL of the degraded inorganic salt liquid culture medium was collected, centrifuged at 10000g for 5 min, and the supernatant was collected. The supernatant was then filtered through a 0.22 μm aqueous filter membrane, and the concentration of 2,4-dichlorophenoxyacetic acid in the solution was determined. The concentration of 2,4-dichlorophenoxyacetic acid during the degradation process was determined using high-performance liquid chromatography (HPLC, Agilent, USA, 1260). The HPLC detection conditions were as follows: a C18 reverse-phase column (150 mm × 4.6 mm) with an injection volume of 20 μL; a mobile phase of methanol:water:acetic acid (v / v ratio 80 / 19.5 / 0.5) and a flow rate of 1 mL / min. -1 The wavelength of the ultraviolet detector is 235nm.

[0057] The degradation results of 2,4-dichlorophenoxyacetic acid by strain GDUTXIONG3 at different initial concentrations are as follows: Figure 4 As shown, the results indicate that strain GDUTXIONG3 achieved a degradation rate of over 82.9% for 50 mg / L 2,4-dichlorophenoxyacetic acid (2,4-dichlorophenoxyacetic acid) after 96 hours, demonstrating its excellent degradation effect. Strain GDUTXIONG3 can be applied to the remediation of water bodies, sediments, and soil contaminated with 2,4-dichlorophenoxyacetic acid, as well as the purification and treatment of 2,4-dichlorophenoxyacetic acid released from herbicides and pesticides.

[0058] Example 3: Degradation test of 2,4-dichlorophenoxyacetic acid in wastewater by strain GDUTXIONG3

[0059] In this embodiment, the *Stenotrophomonas maltophilia* GDUTXIONG3, identified in Example 1 above, was used to study 2,4-dichlorophenoxyacetic acid. After enriching and culturing strain GDUTXIONG3 in liquid culture medium for 18 hours, the bacterial cells were collected by centrifugation, washed three times with phosphate buffer, and then resuspended in a small amount of phosphate buffer for later use.

[0060] The wastewater used in the experiment was taken from the University Town Campus of Guangdong University of Technology (No. 100, Waihuan West Road, Guangzhou University Town, Panyu District, Guangzhou).

[0061] Control group A: Unsterilized wastewater + 50 mg / L 2,4-dichlorophenoxyacetic acid;

[0062] Control group B: Sterilized wastewater + 50 mg / L 2,4-dichlorophenoxyacetic acid;

[0063] Experimental Group C: Unsterilized wastewater + 50 mg / L 2,4-dichlorophenoxyacetic acid + strain GDUTXIONG3 (inoculum size approximately 1.0 × 10⁻⁶) 6 CFU / L);

[0064] Experimental group D: Sterilized soil + 50 mg / L 2,4-dichlorophenoxyacetic acid + strain GDUTXIONG3 (inoculum size approximately 1.0 × 10⁻⁶) 6 CFU / L).

[0065] All groups were cultured at 37℃ and a vibration frequency of 200 r / min, and samples were taken at 12, 24, 48, 72, and 96 h to determine the concentration of 2,4-dichlorophenoxyacetic acid in the wastewater. The concentration of 2,4-dichlorophenoxyacetic acid was determined using high-performance liquid chromatography (HPLC, Agilent, USA, 1260). HPLC detection conditions: C18 reverse-phase column, 150 mm × 4.6 mm, injection volume 20 μL; mobile phase: methanol:water:acetic acid (v / v ratio 80 / 19.5 / 0.5), flow rate 1 ml·min. -1 The wavelength of the ultraviolet detector is 235nm.

[0066] Figure 5 The degradation results of 2,4-dichlorophenoxyacetic acid in wastewater by strain GDUTXIONG3 are shown below. Figure 5 As shown, Stenotrophomonas maltophilia GDUTXIONG3 can effectively degrade 2,4-dichlorophenoxyacetic acid in wastewater and can be used for the treatment of 2,4-dichlorophenoxyacetic acid pollution in wastewater.

[0067] Example 4: Degradation test of 2,4-dichlorophenoxyacetic acid in soil by strain GDUTXIONG3

[0068] In this embodiment, the *Stenotrophomonas maltophilia* GDUTXIONG3, identified in Example 1 above, was used to study 2,4-dichlorophenoxyacetic acid. After enriching and culturing the GDUTXIONG3 strain in liquid culture medium for 18 hours, the bacterial cells were collected by centrifugation, washed three times with phosphate buffer, and then resuspended in a small amount of phosphate buffer for later use.

[0069] The experimental soil was taken from the University Town Campus of Guangdong University of Technology (No. 100, Waihuan West Road, Guangzhou University Town, Panyu District, Guangzhou), and was air-dried and then sieved through a 2mm sieve for later use.

[0070] Control group A: Unsterilized soil + 50 mg / kg 2,4-dichlorophenoxyacetic acid;

[0071] Control group B: Sterilized soil + 50 mg / kg 2,4-dichlorophenoxyacetic acid;

[0072] Experimental group C: Unsterilized soil + 50 mg / kg 2,4-dichlorophenoxyacetic acid + strain GDUTXIONG3 (inoculum size approximately 1.0 × 10⁻⁶) 6 CFU / g);

[0073] Experimental group D: Sterilized soil + 50 mg / kg 2,4-dichlorophenoxyacetic acid + strain GDUTXIONG3 (inoculum size approximately 1.0 × 10⁻⁶) 6 CFU / g).

[0074] The soil moisture content of each group was adjusted to 30% with sterile deionized water and cultured at 37℃ and a vibration frequency of 200 r / min. Samples were taken at 12, 24, 48, 72, and 96 h to determine the concentration of 2,4-dichlorophenoxyacetic acid in the soil. The concentration of 2,4-dichlorophenoxyacetic acid was determined using high-performance liquid chromatography (HPLC, Agilent, USA, 1260). HPLC detection conditions: C18 reverse-phase column, injection volume 20 μL; mobile phase: methanol:water:acetic acid (v / v ratio 80 / 19.5 / 0.5), flow rate 1 ml / min. -1 The wavelength of the ultraviolet detector is 235nm.

[0075] Figure 6 The degradation results of 2,4-dichlorophenoxyacetic acid in soil by strain GDUTXIONG3 are shown below. Figure 6 As shown, Stenotrophomonas maltophiliae GDUTXIONG3 can effectively degrade 2,4-dichlorophenoxyacetic acid in wastewater and can be used for the remediation of 2,4-dichlorophenoxyacetic acid pollution in soil.

[0076] Example 6: Degradation of 2,4-dichlorophenoxyacetic acid by strain GDUTXIONG3 under different experimental conditions

[0077] This embodiment uses Stenotrophomonas maltophiliae GDUTXIONG3, identified in Example 1, to study the degradation of 2,4-dichlorophenoxyacetic acid. First, inorganic salt culture medium was prepared by adding the formulation components to an Erlenmeyer flask and autoclaving at 121°C for 30 min. Then, the GDUTXIONG3 strain was enriched and cultured in solid medium for 18 h. The cells were collected by centrifugation and washed three times with phosphate buffer. A 10% inoculum was then suspended in an Erlenmeyer flask containing 100 mL of inorganic salt culture medium. A certain amount of 2,4-dichlorophenoxyacetic acid solution was added to achieve a concentration of 1 mg / L. Degradation experiments were conducted at temperatures of 20, 25, 30, 35, and 40°C, pH values ​​of 4, 5, 6, 7, 8, and 9, and a frequency of 200 rpm. At 96 hours, 1 mL of the degraded inorganic salt liquid culture medium was taken, centrifuged at 10000g for 5 min, and the supernatant was collected. The supernatant was then filtered through a 0.22 μm aqueous filter membrane, and the concentration of 2,4-dichlorophenoxyacetic acid in the solution was determined. The concentration of 2,4-dichlorophenoxyacetic acid during the degradation process was determined using high-performance liquid chromatography (HPLC, Agilent, USA, 1260). HPLC detection conditions: C18 reverse-phase column, 150 mm × 4.6 mm, injection volume 20 μL; mobile phase: methanol:water:acetic acid (v / v ratio 80 / 19.5 / 0.5), flow rate 1 mL / min. -1 The wavelength of the ultraviolet detector is 235nm.

[0078] like Figure 7 and Figure 8 The figure shows the degradation results of 2,4-dichlorophenoxyacetic acid by strain GDUTXIONG3 under different pH and temperature conditions. The results show that strain GDUTXIONG3 has the best degradation effect on 2,4-dichlorophenoxyacetic acid at pH 7 and temperature 30℃.

[0079] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A strain of Stenotrophomonas maltophilia GDUTXIONG3 that degrades 2,4-dichlorophenoxyacetic acid, characterized in that... The strain GDUTXIONG3 was deposited at the China Center for Type Culture Collection on October 26, 2022, with accession number CCTCC NO: M20221673.

2. The use of the Stenotrophomonas maltophilia strain GDUTXIONG3 or its suspension as described in claim 1 in the degradation of 2,4-dichlorophenoxyacetic acid.

3. The use of the Stenotrophomonas maltophilia strain GDUTXIONG3 or its suspension as described in claim 1 in the preparation of products that degrade 2,4-dichlorophenoxyacetic acid.

4. The use of Stenotrophomonas maltophilia strain GDUTXIONG3 or its suspension as described in claim 1 in the remediation of environments contaminated with 2,4-dichlorophenoxyacetic acid.

5. A bacterial agent for degrading 2,4-dichlorophenoxyacetic acid, characterized in that, It contains the Stenotrophomonas maltophilia strain GDUTXIONG3 or its suspension as described in claim 1.

6. The microbial agent according to claim 5, characterized in that, The number of cells in the *Stenotrophomonas maltophilia* strain GDUTXIONG3 is not less than 1.0 × 10⁻⁶. 6 CFU / mL.

7. The microbial agent according to claim 6, characterized in that, The bacterial count of the Stenotrophomonas maltophilia strain GDUTXIONG3 was 1.0–9.0 × 10⁻⁶. 6 CFU / mL.

8. A method for degrading 2,4-dichlorophenoxyacetic acid or remediating its contamination of the environment, characterized in that, Treatment is performed using any one of the bacterial agents described in claims 5 to 7.

9. The method according to claim 8, characterized in that, The processing conditions are controlled at a temperature of 25–35°C.

10. The method according to claim 8 or 9, characterized in that, The treatment conditions are controlled at pH 6 to 9.

Images