Cadmium-resistant surfactant-producing serratia and application thereof in remediation of cadmium-contaminated soil

Abstract

The invention belongs to the field of applied microbiology, and relates to cadmium-resistant surfactant-producing serratia and application thereof in repairing cadmium-polluted soil. The preservation number of the strain is CGMCC (China General Microbiological Culture Collection Center) The invention discloses Serratia surfactantfaciens, which is classified and named as Serratia surfactantfaciens for producing a surfactant. The screened serratia marcescens for producing the surfactant can tolerate heavy metal Cd < 2 + > of 2000 mg / L, the adsorption rate of the serratia marcescens for Cd < 2 + > of 1000 mg / L is 72.8%, the adsorption rate of the serratia marcescens for Cd < 2 + > of 2000 mg / L is 64.1%, the serratia marcescens has good Cd < 2 + > adsorption capacity, and the serratia marcescens has an improvement effect on Cd < 2 + > polluted soil and seed germination. Therefore, the serratia marcescens for producing the surfactant has great application potential in the aspects of adsorption of the heavy metal Cd < 2 + > and soil improvement of the heavy metal Cd < 2 + >.

Description

Technical Field

[0001] This invention belongs to the field of applied microbiology and relates to a cadmium-resistant surfactant-producing Serratia marcescens strain and its application in the remediation of cadmium-contaminated soil. Background Technology

[0002] Soil is a vital basic resource for human survival. However, in the process of rapid global industrialization, activities such as mineral resource development, metal smelting and processing, chemical production, urban waste disposal, pesticide application, and wastewater irrigation have led to the continuous release of large amounts of heavy metals into the environment, causing increasingly serious soil heavy metal pollution problems. Cadmium pollution in soil poses a serious threat to human health, agricultural production, and the ecological environment, and its harm is characterized by its insidious, cumulative, and long-term nature. As a highly toxic heavy metal, cadmium can accumulate in the human body through the food chain, damaging kidney function and causing osteoporosis (such as "Itai-itai disease"), and even leading to cancer. In agricultural production, cadmium inhibits crop growth, leading to excessive levels of harmful substances in rice and other agricultural products, threatening food security, while also disrupting soil microbial balance and reducing fertility. At the ecological level, cadmium migrates with rainwater, polluting water bodies and harming the entire food chain through biomagnification.

[0003] Currently, heavy metal pollution control faces severe challenges. Traditional physicochemical remediation technologies are limited by high costs and the risk of secondary pollution, making widespread implementation difficult in practice. Against this backdrop, bioremediation technologies centered on microorganisms are gaining increasing attention due to their environmental friendliness and sustainability. Microorganisms, with their rich species diversity, strong environmental adaptability, and complex metabolic pathways, can effectively reduce the toxicity and mobility of heavy metals through various mechanisms such as biosorption, valence transformation, and mineralization fixation. This remediation strategy based on natural ecological processes opens up a more economical and environmentally friendly new path for heavy metal pollution control.

[0004] In recent years, various strains tolerant to the heavy metal cadmium have been reported. Chinese patent CN 116574661A discloses a strain of Bacillus altitudinis C10-4, which is tolerant to Cd. 2+ The tolerance level is 1600 mg / L. Chinese patent CN112592855A discloses a highly cadmium-tolerant Bacillus subtilis, whose maximum tolerance concentration for cadmium is only 200 mg / L. However, the cadmium tolerance of these microorganisms is far from meeting the needs for treating high-concentration cadmium-contaminated soil. Summary of the Invention

[0005] This invention provides a strain of Serratia surfactantfaciens, which is tolerant to high concentrations of cadmium and produced by screening from the gut of black soldier fly larvae. This strain can be used to remediate cadmium-contaminated soil.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention relates to the heavy metal Cd 2+ A strain capable of tolerating high concentrations of Cd was screened from the gut of stressed black soldier fly larvae. 2+ The 16S rDNA sequence of strain W-L4 was compared with that of *Serratia surfactantfaciens* in NCBI, and the results showed that it had the highest homology with *Serratia surfactantfaciens*, thus identifying it as *Serratia surfactantfaciens* W-L4. The 16S rDNA sequence of *Serratia surfactantfaciens* W-L4 is shown in SEQ ID NO:1.

[0008] Then, the heavy metal Cd assay was performed on strain W-L4. 2+ Adsorption experiment, adsorption of Cd 2+ Post-strain performance characterization, soil leaching germination experiments, etc., showed that the Serratia surfactantfaciens W-L4 involved in this invention is effective against heavy metal Cd. 2+ Adsorption and heavy metal Cd 2+ It has shown good results in soil improvement.

[0009] Based on the above, this invention first provides a strain of surfactant-producing Serratia (Serratia surfactantfaciens W-L4), with the following accession number: CGMCC No. 35365; classification name: Serratia surfactantfaciens; depositary institution: China General Microbiological Culture Collection Center; address of depositary institution: No. 3, No. 1 Courtyard, Beichen West Road, Chaoyang District, Beijing; deposit date: July 24, 2025.

[0010] Secondly, the present invention also provides a microbial inoculant containing the aforementioned surfactant-producing Serratia surfactantfaciens W-L4. Further, the microbial inoculant contains a culture medium of the aforementioned surfactant-producing Serratia surfactantfaciens W-L4.

[0011] Furthermore, the preparation method of the culture medium includes: inoculating surfactant-producing Serratia (Serratia surfactantfaciens W-L4) into LB liquid medium and culturing at 30°C for 12-48 hours to obtain the culture medium.

[0012] Furthermore, the culture medium is a supernatant or a bacterial suspension. The supernatant is the liquid obtained by centrifuging the culture medium; the bacterial suspension is obtained by resuspending the precipitate after centrifuging the culture medium.

[0013] Thirdly, the present invention provides the application of one or more of the following components in the adsorption of heavy metal cadmium:

[0014] (1) The surfactant-producing Serratia surfactantfaciens W-L4;

[0015] (2) The culture medium of the surfactant-producing Serratia surfactantfaciens W-L4;

[0016] (3) The microbial agent mentioned above.

[0017] Fourthly, this invention provides the application of one or more of the following components in the remediation of cadmium-contaminated soil:

[0018] (1) The surfactant-producing Serratia surfactantfaciens W-L4;

[0019] (2) The culture medium of the surfactant-producing Serratia surfactantfaciens W-L4;

[0020] (3) The microbial agent mentioned above.

[0021] In addition, the present invention also provides a soil remediation product for heavy metal cadmium contaminated soil, the product containing one or more of the following active ingredients:

[0022] (1) The surfactant-producing Serratia surfactantfaciens W-L4;

[0023] (2) The culture medium of the surfactant-producing Serratia surfactantfaciens W-L4;

[0024] (3) The microbial agent mentioned above.

[0025] The beneficial effects of this invention are as follows:

[0026] The surfactant-producing Serratia surfactantfaciens W-L4 strain screened in this invention can tolerate 2000 mg / L of the heavy metal Cd. 2+ For 1000 mg / L of Cd2+ The adsorption rate was 72.8% for 2000 mg / L Cd. 2+ The adsorption rate is 64.1%, indicating good Cd adsorption capacity. 2+ Adsorption capacity, and for Cd 2+ It has a modifying effect on contaminated soil and seed germination. Therefore, the Serratia surfactantfaciens W-L4 involved in this invention has a modifying effect on heavy metal Cd. 2+ Adsorption and heavy metal Cd 2+ It has great potential for application in soil improvement. Attached Figure Description

[0027] Figure 1 strain WL-4 at different concentrations of Cd 2+ Growth on LB agar plates. Each plate shows a gradient of bacterial suspensions from left to right, with dilutions of 1, 10, etc. 1 10 2 10 3 and 10 4 From left to right, in the flat plate, Cd 2+ The concentrations were 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L and 2500 mg / L, respectively.

[0028] Figure 2 Strain WL-4 in different concentrations of Cd 2+ Growth in LB liquid medium.

[0029] Figure 3 Classification and identification analysis of strain W-L4. (A) Colony morphology of strain W-L4; (B) Individual morphology and Gram staining of W-L4; (C) Phylogenetic tree of strain W-L4.

[0030] Figure 4 Analysis was performed using scanning electron microscopy (SEM) and energy dispersive chromatograph (EDS). Control group: (A) SEM image; (C) Cd elemental distribution map; (E) EDS elemental distribution overlay map. Experimental group: (B) SEM image; (D) Cd elemental distribution map; (F) EDS elemental distribution overlay map.

[0031] Figure 5 FTIR observation of LB liquid medium without added Cd 2+ And add 1000 mg / L Cd 2+ Changes on the surface of the bacteria.

[0032] Preservation Information

[0033] Preserved biological material: strain W-L4;

[0034] Accession number: CGMCC No. 35365;

[0035] Classification and nomenclature: Serratia surfactantfaciens;

[0036] Preservation institution: China General Microbiological Culture Collection Center, China Committee on the Preservation and Management of Microbial Culture Collections;

[0037] Address of the depository: No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing;

[0038] Preservation date: July 24, 2025. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] Example 1

[0041] 1. Domestication of gut microbiota in black soldier fly larvae

[0042] Black soldier fly eggs were hatched using a mixture of 70% corn flour and 30% wheat bran and cultured for 7 days in a constant temperature and humidity incubator at 28°C and 70% humidity. 300 mg / L of Cd was added to the substrate of the seven-day-old black soldier fly larvae. 2+ Black soldier fly larvae were reared for 15-20 days with CdSO4 (analytical grade). The larvae were then exposed to CdSO4. 2+ Under stress, the gut microbiota will respond and adjust the species and abundance of the flora, that is, in Cd 2+ Under stress, gut microbiota are domesticated.

[0043] 2.Cd 2+ Isolation of Cd-resistant strain W-L4 2+ Tolerance

[0044] 2.1Cd 2+ Isolation and purification of resistant strain W-L4

[0045] (1) Sterilize the tools needed for dissecting black soldier fly larvae. Wash the black soldier fly larvae twice with water and then immerse them in 75% alcohol for 10 minutes for disinfection. Use a scalpel to cut from the anus on the back of the black soldier fly to the thorax, and then use sterile forceps to remove the intestines and place them in a centrifuge tube. Dissect the intestines of 10-20 larvae, add 10 mL of sterile water and grind to prepare a bacterial suspension.

[0046] (2) The bacterial suspension was inoculated into LB solid medium (10g tryptone, 5g yeast extract, 10g NaCl, 15g agar powder, 1000mL distilled water) for enrichment culture. After repeated streak purification, Cd was obtained. 2+ Bacteria can be cultured from the gut under stress.

[0047] (3) Prepare 50 g / L Cd 2+ The stock solution was added to LB solid medium at a final concentration of 200 mg / L and plated. The activated and purified enteric bacteria were cultured in LB liquid medium and diluted 1, 10, 100, 1000, and 10000 times for later use. 20 μL of each serially diluted bacterial solution was inoculated into the medium and incubated at 30°C for 48 h. Cd was gradually increased. 2+ The ion solution concentrations were increased to 500 mg / L, 1000 mg / L, 1500 mg / L, and 2000 mg / L. The above steps were repeated to continue the screening until the most Cd-tolerant solution was selected. 2+ strain W-L4.

[0048] 2.2W-L4 for Cd 2+ Tolerance

[0049] W-L4 was inoculated into LB liquid medium and cultured at 30°C, pH 7, and 150 rpm for 12 h to obtain a bacterial suspension. The bacterial suspension was then diluted 1, 10, and 10 times sequentially. 1 10 2 10 3 and 10 4 Times. Preparation of materials containing different concentrations of Cd. 2+ LB solid plate (Cd 2+ Concentrations were set at 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, and 2500 mg / L. 10 μL of each diluted bacterial suspension was inoculated onto substrates containing different concentrations of Cd. 2+ The cells were incubated on LB solid plates at 30°C for 24 hours, and the growth was observed. Figure 1 As shown, in Cd 2+ In LB plates with concentrations of 500–2000 mg / L, undiluted W-L4 growth was not affected by Cd. 2+ Impact. When Cd 2+ At a concentration of 2500 mg / L, the growth of W-L4 was significantly inhibited at all dilutions. These results indicate that W-L4 can tolerate 2000 mg / L of Cd. 2+ This also indicates that as the dilution of the inoculated bacterial solution increases, W-L4's effect on Cd... 2+ Its tolerance weakens.

[0050] Preparation of Cd with different concentrations 2+ LB liquid medium. Cd 2+ The concentrations were set at 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, and 2500 mg / L. W-L4 was inoculated into LB liquid medium and cultured at 30°C, pH 7, and 150 rpm for 12 h to obtain bacterial suspensions. These suspensions were then inoculated at a 2% inoculum into media containing different concentrations of Cd. 2+ In LB liquid medium, cultured for 24 h, and OD was measured. 600nm The absorbance value characterizes the growth of bacterial cells. For example... Figure 2 As shown, the absorbance values ​​of W-L4 at concentrations of 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, and 2500 mg / L were 1.80, 1.73, 1.17, 0.76, and 0.12, respectively. When the incubation time was extended to 48 h, the absorbance values ​​of W-L4 at concentrations of 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, and 2500 mg / L were 2.17, 2.06, 2.00, 1.72, and 0.22, respectively. This indicates that W-L4 can grow at concentrations below 2000 mg / L and has strong tolerance to the heavy metal cadmium.

[0051] 3. Identification of strains

[0052] 3.1 Identification of colony and strain morphology:

[0053] (1) Colony culture: The W-L4 strain was streaked onto LB solid medium and cultured for 48 hours. Colony morphology was then observed. Figure 3 As shown in (A), the colonies are milky white, opaque, moist, round, with neat edges and a slightly raised center.

[0054] (2) Gram staining: Smears of the screened strain W-L4, laboratory-preserved *Escherichia coli*, and *Diabolus luteum* were fixed (*Escherichia coli* and *Diabolus luteum* served as negative and positive controls for Gram staining, respectively). After staining with crystal violet for 1 min, the smear was slowly rinsed with distilled water and the surrounding moisture was absorbed. After covering with iodine solution for 1 min, the smear was slowly rinsed with distilled water and the surrounding moisture was absorbed. After destaining with 95% alcohol for 30 s, the smear was slowly rinsed with distilled water and the surrounding moisture was absorbed. After counterstaining with safranin for 1 min, the smear was slowly rinsed with distilled water and the surrounding moisture was absorbed. Microscopic observation and image acquisition were then performed. Figure 3 As shown in (B), W-L4 is a short rod-shaped bacterium that stains red with Gram stain and is a Gram-negative bacterium.

[0055] 3.2 Molecular biological identification of the strain:

[0056] (1) Prepare the lysis buffer: 20 μL 1 mol / L NaOH, 30 μL ddH2O, 50 μL 2% SDS, mix well.

[0057] (2) Genomic DNA extraction: Take 1 mL of the bacterial culture in the logarithmic growth phase and place it in a 1.5 mL centrifuge tube. Centrifuge at 5000 rpm for 5 min and collect the bacterial cells. Take a portion of the centrifuged bacterial cells and place them in a new 1.5 mL centrifuge tube. Add 10 μL of lysis buffer and react for 5 min. Add 200 μL of ddH2O and mix well.

[0058] Figure 3 As shown in (C), strain W-L4 has the highest homology with surfactant-producing Serratia surfactantfaciens and is identified as Serratia surfactantfaciens W-L4.

[0059] Strain W-L4 was deposited with accession number CGMCC No. 35365; classification name: Serratia surfactantfaciens; depositary institution: China General Microbiological Culture Collection Center; depositary institution address: No. 3, No. 1, Beichen West Road, Chaoyang District, Beijing; deposit date: July 24, 2025.

[0060] 4. Determination of heavy metal adsorption capacity of strain W-L4

[0061] 4.1W-L4 for the metal ion Cd 2+ adsorption rate

[0062] The W-L4 strain was activated using LB liquid medium at 30°C and 150 rpm. The activated W-L4 bacterial solution was then inoculated at a 2% inoculum onto cells containing Cd. 2+ The samples were cultured in 1000 mg / L and 2000 mg / L LB liquid medium at 30℃ and 150 rpm for 48 h, centrifuged at 8000 rpm for 10 min, and the supernatant was collected. The residual Cd in the supernatant was determined using an atomic absorption spectrophotometer (TAS990, Beijing Purkinje). 2+ The concentration of W-L4 for the metal ion Cd is calculated using the following formula. 2+ Adsorption rate:

[0063]

[0064] In the above formula, R is the adsorption rate; C0 is the initial metal ion concentration; C e This represents the concentration of metal ions in the supernatant solution.

[0065] The results showed that W-L4 was effective against 1000 mg / L Cd. 2+ The adsorption rate was 72.8% for 2000 mg / L Cd. 2+ The adsorption rate was 64.1%, as detailed in Table 1. These results indicate that with the adsorption of metal ions Cd... 2+ As the concentration increases, the adsorption rate decreases.

[0066] Table 1. Effects of W-L4 on Cd in LB liquid medium 2+ adsorption rate

[0067] metal ions <![CDATA[Cd 2+ ]]> <![CDATA[Cd 2+ ]]> Initial concentration mg / L 1000 2000 Supernatant concentration mg / L 272 718 Adsorption rate % 72.8 64.1％

[0068] Next, strain W-L4 was used to adsorb Cd. 2+ Subsequent analysis was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). Specifically, the experimental group was inoculated with activated W-L4 at a dose of 2% in 1000 mg / L Cd. 2+ In LB liquid medium (the control group was inoculated with activated W-L4 at a 2% inoculation rate into Cd-free medium), 2+ The samples were cultured in LB liquid medium at 30°C and 150 rpm for 48 h, centrifuged at 8000 rpm for 10 min to obtain a precipitate, washed with Na2HPO4-NaH2PO4 buffer (pH=7.0), and fixed overnight in 2.5% glutaraldehyde solution (v / v). The precipitate was then washed with Na2HPO4-NaH2PO4 buffer (pH=7.0) and dehydrated with 30%, 50%, 70%, 90%, 95%, and 100% ethanol, followed by freeze-drying. After fixation with conductive carbon gel, the samples were sputter-coated with gold for 90 seconds to ensure a sufficiently thick conductive layer while avoiding interference with surface morphology observation and EDS elemental analysis. The cell surface morphology was observed using a Sigma 300 scanning electron microscope, and specific regional chemical composition analysis was performed using an Xplore 30 energy dispersive spectroscopy (EDS) spectrometer. Fourier transform infrared (FTIR) wavenumber range was set to 4000–400 cm⁻¹. -1 32 scans, 4cm resolution -1 The result is as follows Figure 4 As shown, without Cd 2+ The treated W-L4 strain was rod-shaped. 2+ After treatment, the presence of the metal element Cd was detected on the cell surface, indicating that W-L4 has a good adsorption capacity for Cd. Figure 5 As shown, the FTIR results are displayed at 1000-1200 cm⁻¹. -1 Changes in the peak position of phosphate groups (P=O) may reflect a precipitation reaction between phosphate groups in phospholipids or nucleic acids and cadmium (such as the formation of Cd3(PO4)2); sulfur-related peaks (500-700 cm⁻¹) -1 The changes suggest that thiol (-SH) or sulfur-containing amino acids are involved in the complexation of cadmium.

[0069] 4.2 Adsorption of heavy metal ions in soil by W-L4

[0070] Soil pretreatment: Take three 1kg portions of sieved farmland soil and place them in empty flowerpots. Add water and 1000mg / kg Cd to each soil portion respectively. 2+ and 2000mg / Kg Cd 2+Next, add 20 mL of activated W-L4 bacterial solution to the flowerpot and mix well. Incubate at room temperature in the dark for 20 days, turning the soil every 48 hours and spraying with sterile water to keep the soil moist. After incubation, randomly take 10 g of soil using the five-point sampling method, add 100 mL of sterile deionized water, and shake horizontally at 150 rpm for 1 hour. After standing until the soil and liquid separate into layers, collect the supernatant and determine the remaining Cd in the supernatant using an atomic absorption spectrophotometer (TAS990, Beijing Purkinje). 2 The concentration of Cd in soil is calculated using the following formula: W-L4. 2+ Adsorption rate:

[0071]

[0072] In the above formula, R is the adsorption rate; C0 is the initial metal ion concentration; C e This represents the concentration of metal ions in the supernatant solution.

[0073] The results showed that W-L4 was effective against Cd at a concentration of 1000 mg / kg in soil. 2+ The adsorption rate was 98.7% for 2000 mg / kg Cd in soil. 2+ The adsorption rate was 84.5%, as detailed in Table 2. These results indicate that W-L4 effectively adsorbs Cd from soil. 2+ The adsorption effect of soil in this medium was better than that in LB liquid medium, possibly because soil has a lower adsorption capacity for heavy metal ions such as Cd. 2+ It also has a certain degree of adhesion.

[0074] Table 2. Effects of W-L4 on Cd in soil 2+ adsorption rate

[0075] metal ions <![CDATA[Cd 2+ ]]> <![CDATA[Cd 2+ ]]> Initial concentration mg / Kg 1000 2000 Supernatant concentration mg / Kg 13 310 Adsorption rate % 98.7 84.5％

[0076] 5. Effects of W-L4 on radish seed germination

[0077] W-L4 cells were activated to the logarithmic phase using LB liquid medium, centrifuged at 8000 rpm for 10 min to obtain a precipitate, washed three times with Na2HPO4-NaH2PO4 buffer (pH=7.0), and then prepared as an OD200 using Na2HPO4-NaH2PO4 buffer (pH=7.0). 600 =2.0 bacterial suspension. Select plump and healthy radish seeds, disinfect them with hypochlorous acid, and then soak them in the above bacterial suspension for 6 hours. Seeds soaked in Na2HPO4-NaH2PO4 buffer (pH=7.0) served as a control. Add 5 mL of sterile water and Cd to each of the following solutions in a petri dish (9 cm in diameter). 2+(10 mg / L) Two layers of sterile filter paper were placed in a dish, and 15 soaked radish seeds were evenly placed on top. The dish was incubated at 28°C. Germination rate and root length were calculated after 3 days (see Table 3 for details). The results showed that W-L4 could alleviate Cd 2+ To address seed stress, increasing seed germination rate promotes root growth.

[0078] Table 3. Germination of radish seeds under different treatments

[0079] Metal elements <![CDATA[Cd 2+ ]]> water Germination rate (control) 53.3％ 66.7％ Germination rate (W-L4) 65.0％ 79.8％ Root length (control) 2.2cm 6.3cm Root length (W-L4) 2.7cm 10.2cm

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surfactant-producing Serratia strain (Serratia sp. W-L4), characterized in that, Serratia surfactantfaciens W-L4), which is characterized in that, The strain has a preservation number of CGMCC No. 35365; and a classification name of Serratia surfactans Serratia surfactantfaciens .

2. A microbial inoculant, characterized in that, The microbial inoculant contains the surfactant-producing Serratia sp. of claim 1 Serratia surfactantfaciens W-L4).

3. The microbial inoculant of claim 2, wherein, The microbial agent contains the culture solution of the surfactin-producing Serratia marcescens (W-L4). Serratia surfactantfaciens W-L4).

4. The microbial inoculant of claim 3, wherein, The preparation method of the culture solution comprises the following steps: inoculating surfactin-producing Serratia marcescens (W-L4) into LB liquid culture medium, and culturing at 30 DEG C for 12-48 h. Serratia surfactantfaciens W-L4) into LB liquid culture medium, and culturing at 30 DEG C for 12-48 h.

5. The microbial inoculant of claim 3, wherein, The culture solution is supernatant or bacterial suspension, the supernatant is the liquid obtained after centrifugation of the culture solution; the bacterial suspension is obtained after resuspension of the precipitate after centrifugation of the culture solution.

6. The use of one or more of the following components in the adsorption of heavy metal cadmium, characterized in that: (1) The surfactant-producing Serratia sp. according to claim 1, Serratia surfactantfaciens W-L4); (2) A culture of surfactant-producing Serratia marcescens (S. marcescens) of claim 1; W-L4 Serratia surfactantfaciens W-L4 (3) The microbial inoculant of any one of claims 2-5.

7. The use of one or more of the following components in the remediation of heavy metal cadmium contaminated soil, characterized in that: (1) The surfactant-producing Serratia sp. according to claim 1, Serratia surfactantfaciens W-L4); (2) A culture of surfactant-producing Serratia marcescens (S. marcescens) of claim 1; W-L4 Serratia surfactantfaciens W-L4) (3) The microbial inoculant of any one of claims 2-5.

8. A product for remediation of heavy metal cadmium contaminated soil, characterized by: The product contains one or more of the following active ingredients: (1) The surfactant-producing Serratia sp. according to claim 1, Serratia surfactantfaciens W-L4); (2) A culture of surfactant-producing Serratia marcescens (S. marcescens) of claim 1; W-L4 Serratia surfactantfaciens W-L4 (3) The microbial inoculant of any one of claims 2-5.

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