CN112899185A

CN112899185A - Screening and application of benzo [ a ] anthracene degrading bacteria in black and odorous bottom mud

Info

Publication number: CN112899185A
Application number: CN202110122938.0A
Authority: CN
Inventors: 王宏杰; 董文艺; 周婷; 王�锋; 赵子龙; 杨墨; 黄潇
Original assignee: Shenzhen Graduate School Harbin Institute of Technology
Current assignee: Shenzhen Graduate School Harbin Institute of Technology
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2021-06-04
Anticipated expiration: 2041-01-29
Also published as: CN112899185B

Abstract

The invention relates to the fields of microbial degradation technology and environmental protection, in particular to screening and application of a strain MZ-5(Microbacterium xylonii lyticum) with a degradation effect on benzo [ a ] anthracene. The strain was named MZ-5. The strain is preserved in the common microorganism center of China Committee for culture Collection of microorganisms, and the address is No. 3 Hospital of Xilu of Beijing, Chaoyang, China academy of sciences, the preservation number is: CGMCC No.20668, preservation date: 9/18/2020. The strain is screened from Shenzhen Shenzhou black stink substrate sludge, and the screening conditions are as follows: the culture solution has a pH of about 7.0, 20mg/L benzo [ a ] anthracene, 140r/min, and is cultured at a constant temperature of 30 ℃. Under the condition of pure culture, when the pH value is 5.0 and the temperature is 30 ℃, the degradation efficiency of the strain to benzo [ a ] anthracene is highest and can reach 67% within 72 h. In addition, the strain has good adaptability in substrate sludge and shows good multi-substrate degradation capability. Through the research on the biological characteristics and the degradation characteristics of the strain, the strain can provide technical support for the biological treatment of refractory organic matters such as benzo [ a ] anthracene and the like in the sediment.

Description

Screening and application of benzo [ a ] anthracene degrading bacteria in black and odorous bottom mud

Technical Field

The invention relates to the fields of microbial degradation technology and environmental protection, in particular to screening and application of a strain MZ-5(Microbacterium xylonii lyticum) with a degradation effect on benzo [ a ] anthracene.

Background

The black and odorous bottom sludge in the current stage of China is seriously polluted, the pollutants in the black and odorous bottom sludge are various, and the black and odorous bottom sludge not only contains nitrogen, phosphorus and other nutrient elements generated by daily water consumption, but also contains various heavy metals and refractory organic matters generated by fuel combustion and various industrial wastewater. Polycyclic aromatic hydrocarbon substances are one of main organic matters difficult to degrade in the black and odorous bottom mud, and can exist for a long time in the environment due to high hydrophobicity and difficult degradability, so that the treatment difficulty of the black and odorous bottom mud is increased. In addition, polycyclic aromatic hydrocarbon is a strong toxic substance, and can cause damage such as teratogenesis, carcinogenesis and the like to human bodies. Therefore, how to effectively remove the polycyclic aromatic hydrocarbons in the black and odorous substrate sludge becomes a research difficulty and a hotspot in substrate sludge remediation at present.

The polycyclic aromatic hydrocarbon is mainly attached to solid particles in the black and odorous substrate sludge and can be removed by physical treatment (solidification, bioleaching and wet air oxidation), chemical treatment (solvent extraction, decomposition, chemical detoxification and the like), biological treatment (phytoremediation, animal remediation, microbial remediation and the like) and other technologies. Compared with physical and chemical treatment, biological treatment has the advantages of strong pertinence, low economic cost, difficulty in causing secondary pollution and the like, and is an economic, efficient and eco-friendly remediation technology. Microbial remediation is the removal of environmental pollutants by the ability of microorganisms to oxidize, reduce, separate, and transfer elemental valences. The method solves the pollution problem in the specific environment by domesticating and enriching and culturing microorganisms with special performance by utilizing stronger tolerance, specific adaptability and genetic diversity of the microorganisms in the polluted environment, and becomes an important development direction for solving the pollution problem of soil and bottom mud at present.

At present, the research of the polycyclic aromatic hydrocarbon microbial agent mainly aims at the environmental fields of polluted soil, activated sludge and the like. Among them, it was found by pottery good rain, etc. that polycyclic aromatic hydrocarbon-degrading bacteria can be separated from plants such as ophiopogon root, etc. growing in polycyclic aromatic hydrocarbon-contaminated soil. Kumar et al screened 4 fluoranthene-degrading bacteria from oil sludge deposits and had a good remediation effect on oil sludge contaminated with fluoranthene. Three strains of salt-tolerant naphthalene degrading bacteria are screened from high-saline-alkali soil seriously polluted by petroleum, and are determined to be pseudomonas through gene detection, and the strains are found to have a new salt-tolerant and naphthalene degrading mechanism. The Wangxiang dynasty separates and screens two fluorene degrading bacteria from activated sludge of a certain coking plant, and researches show that the two fluorene degrading bacteria can degrade pyrene, phenanthrene and the like simultaneously, so that the fluorene degrading bacteria can be applied to the restoration of polycyclic aromatic hydrocarbon composite polluted environment. However, the application of the current polycyclic aromatic hydrocarbon microbial agent in black smelly substrate sludge is less, and related researches on benzo [ a ] anthracene degrading bacteria are rarely carried out through literature summarization and comparison.

Therefore, single benzo [ a ] anthracene degrading bacteria are screened from the black and odorous substrate sludge, and a technical support and a theoretical basis can be provided for the biological treatment of benzo [ a ] anthracene in the black and odorous substrate sludge by researching the biological characteristics and the degradation performance of the benzo [ a ] anthracene degrading bacteria.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a strain for degrading benzo [ a ] anthracene, which can effectively degrade the benzo [ a ] anthracene.

Specifically, the invention is realized by the following technical scheme: a strain for degrading benzo [ a ] anthracene, which is named as MZ-5(Microbacterium xylanilyticum) with the deposition number: CGMCC No. 20668.

The specific preservation information of the strain is as follows:

name: microbacterium xylanilyticum

The preservation unit: institute of microbiology, national academy of sciences

The address of the depository: xilu No. 3 Hospital of the Chao Yang district, Beijing City of China

Preservation time: 9 and 18 months in 2020

The preservation number is: CGMCC No.20668

MZ-5(Microbacterium xylanilyticum) belongs to the genus Microbacterium; the cells of the strain are gram-positive, non-motile and non-sporulation rod-shaped cells; the colony is round, yellow and transparent, the surface is moist and glossy, and the diameter is about 1 mm.

In addition, the invention provides a screening method of a strain for degrading benzo [ a ] anthracene, which comprises the steps of collecting a black smelly bottom sediment sample from a certain river section of the Shenzhen province river, feeding a liquid culture solution containing a single target carbon source into the bottom sediment sample in a sterile room, performing oriented acclimation step by step, coating the bottom sediment sample by using a solid culture medium containing the single target carbon source, and placing the bottom sediment sample in an incubator at 30 ℃ for inverted culture. Through multiple separation, single dominant bacterial strain with high efficiency degradation of benzo [ a ] anthracene is purified.

As a preferred technical scheme of the invention, the screening method of the strain for degrading benzo [ a ] anthracene comprises the following steps:

1) collecting black odorous bottom sediment samples from a certain river section of the Shenzhen province river, and refrigerating and storing in dark. 5g of the substrate sludge was dissolved in 10mL of sterile water, and after shaking at a constant temperature for 24 hours, 1mL of the substrate sludge leachate was inoculated into 50mL of a liquid medium containing 1mg/L of benzo [ a ] anthracene. Culturing at 30 deg.C and 140r/min for 7 days. 2mL of the enriched liquid of the substrate sludge was cultured in 50mL of a liquid medium containing 10mg/L of benzo [ a ] anthracene under the same conditions for 7 days. The operation is repeated for 4 times, and the concentration of the benzo [ a ] anthracene is gradually increased to 100mg/L, thereby achieving the purpose of enrichment and domestication.

2) Diluting the domesticated solution step by step, taking the diluted domesticated solution by an inoculating loop, streaking the diluted domesticated solution on an inorganic salt solid culture medium containing benzo [ a ] anthracene, and culturing in a constant temperature incubator for 5 days at the temperature of about 30 ℃.

3) Shaped colonies of different forms were picked and inoculated onto a new solid medium containing benzo [ a ] anthracene at a concentration of 50mg/L for purification culture. And repeating the streaking separation and purification for many times until the colony forms formed on the solid culture medium are consistent, thus obtaining the single dominant strain with the high-efficiency degradation of the benzo [ a ] anthracene.

4) The liquid culture medium is calculated by 1L and consists of the following components in parts by weight:

2.0g(NH₄)₂SO₄，0.2g MgSO₄·7H₂O，0.01g CaCl₂·2H₂O，0.001g FeSO₄·7H₂O， 1.5g Na₂HPO₄·12H₂O，1.5g KH₂PO₄，0.004g MnCl₂·4H₂O，0.001g ZnCl₂，0.001g CoCl₄·6H₂O，0.002g NiCl₂·6H₂O，0.0003g CuSO₄·5H₂O。

5) the solid culture medium is calculated by 1L of the solid culture medium and comprises the following components in parts by weight:

2.0g(NH₄)₂SO₄，0.2g MgSO₄·7H₂O，0.01g CaCl₂·2H₂O，0.001g FeSO₄·7H₂O， 1.5g Na₂HPO₄·12H₂O，1.5g KH₂PO₄，0.004g MnCl₂·4H₂O，0.001g ZnCl₂，0.001g CoCl₄·6H₂O，0.002g NiCl₂·6H₂O，0.0003g CuSO₄·5H₂o, 18g agar.

The purification and separation of target strains are carried out by combining a solid culture medium with a coating method, namely 100 mu L of liquid culture medium after gradual domestication is subjected to gradient dilution, and then the liquid culture medium is coated on the solid culture medium through the experimental method steps of the solid culture medium. Culturing in 30 deg.C incubator. After 7 days, single colony is picked out for culture by using a solid medium experiment method, the strain is obtained by amplification culture in a liquid medium, then the bacterial liquid is added into a sterilized 50mL centrifugal tube, the centrifugal tube is centrifuged for 6min under the condition of 6000r/min, and the supernatant is discarded.

The strain for degrading benzo [ a ] anthracene can be used for treating black smelly substrate sludge containing benzo [ a ] anthracene. The strain for degrading benzo [ a ] anthracene is inoculated into a plastic tank containing benzo [ a ] anthracene black smelly bottom mud, a layer of 10cm pure water is coated on the tank, and the tank is placed in a dark sealing mode, so that a good benzo [ a ] anthracene degradation effect is obtained.

The bacterial strain for degrading benzo [ a ] anthracene degrades benzo [ a ] anthracene under the conditions of 30-35 ℃ and pH 6. Experiments show that the strain can completely degrade benzo [ a ] anthracene in different initial concentrations (10-500mg/L, calculated by the volume of a 250mL conical flask) in a liquid culture medium within 70 h; the strain has good bottom mud broad spectrum, and can utilize fluoranthene, phenol and dimethyl phthalate as carbon source and energy source.

The beneficial effects of the invention compared with the prior art comprise:

a strain for degrading benzo [ a ] anthracene is provided and named as MZ-5, and the strain is gram-positive bacteria, the colony of the strain is round, yellow and transparent, the surface of the strain is moist and glossy, and the diameter of the strain is about 1 mm. The method has the capability of efficiently degrading the benzo [ a ] anthracene, can use fluoranthene, phenol and dimethyl phthalate as a carbon source and an energy source, and can be used for the biodegradation treatment process of the benzo [ a ] anthracene in the black and odorous substrate sludge.

Drawings

FIG. 1 shows the growth of MZ-5 on a solid medium;

FIG. 2 is a phylogenetic tree of molecular biology of MZ-5;

FIG. 3 is a graph of an experiment for single-factor influence of MZ-5 on degradation of benzo [ a ] anthracene; wherein, (3a) the effect of pH; (3b) influence of temperature; (3c) influence of benzo [ a ] anthracene concentration; (3d) influence of the amount of bacteria dosed.

Detailed Description

The invention is further described below with reference to specific embodiments and the accompanying drawings. The examples are provided merely as illustrations of the methods of the invention and are not intended to limit the remainder of the invention in any way.

Example 1 domestication and screening of benzo [ a ] anthracene-degrading bacteria

1. Acclimatization and culture of strain

The experimental sample is collected from black odorous bottom mud of a certain river section of the Cogeneration river of Shenzhen, Guangdong province, and immediately placed in the lake sectionAnd storing in a cold storage at the temperature of 4 ℃ in a laboratory in a dark place. Dissolving 5g of substrate sludge in 10mL of sterile water, oscillating at constant temperature for 24h, inoculating 1mL of substrate sludge leachate in 50mL of benzo [ a ] benzene]Anthracene concentration of 1mg/L in liquid medium. Culturing at 30 deg.C and 140r/min for 7 days. 2mL of the enriched sediment solution is added into 50mL of benzo [ a ]]Liquid medium with anthracene concentration of 10mg/L (medium component: 2.0g/L (NH)₄) ₂SO₄，0.2g/L MgSO₄·7H₂O，0.01g/L CaCl₂·2H₂O，0.001g/L FeSO₄·7H₂O，1.5g/L Na₂HPO₄·12H₂O，1.5g/L KH₂PO₄，0.004g/L MnCl₂·4H₂O，0.001g/L ZnCl₂，0.001g/L CoCl₄·6H₂O，0.002g/L NiCl₂·6H₂O，0.0003g/L CuSO₄·5H₂O), cultured under the same conditions for 7 days. This operation was repeated 4 times to gradually increase benzo [ a ]]The concentration of anthracene is 100mg/L, thus achieving the purpose of enrichment and domestication.

2. Screening and purifying of strains

Benzo [ a ]]Screening and purifying anthracene degrading bacteria: diluting the domestication solution step by step, taking the diluted domestication solution by inoculating loop, and adding the domestication solution into a solution containing benzo [ a ]]Anthracene inorganic salt solid Medium (Medium component: 2.0g/L (NH)₄)₂SO₄，0.2g/L MgSO₄·7H₂O，0.01g/L CaCl₂·2H₂O，0.001g/L FeSO₄·7H₂O，1.5g/L Na₂HPO₄·12H₂O，1.5g/L KH₂PO₄，0.004g/L MnCl₂·4H₂O，0.001g/L ZnCl₂，0.001g/L CoCl₄·6H₂O，0.002g/L NiCl₂·6H₂O，0.0003g/L CuSO₄·5H₂O, 18g/L agar) and cultured in an incubator at about 30 ℃ for 5 days. Shaped colonies of different morphologies were picked and inoculated separately into new colonies containing benzo [ a ]]And performing purification culture on an anthracene solid culture medium. Repeating the streaking separation and purification for many times until the colony forms on the solid culture medium are consistent, thus obtaining the benzo [ a ] with high-efficiency degradation]Mono-of anthraceneA dominant strain. And (3) carrying out slant plate streaking on the strain, and carrying out strain identification after bacterial colonies grow out. The strain was named MZ-5.

3. Strain morphology and molecular biology identification

The obtained strain for degrading benzo [ a ] anthracene is subjected to 16S rDNA sequencing, and comprises strain DNA extraction and 16S rDNA in-vitro PCR amplification ((using 16S universal primers 27F and 1492R, 27F: 5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R: 5'-TACCTTGTTACGACTT-3') to obtain a gene fragment of 1500 bp. . The sequence results obtained by sequencing were brought into the NCBI database for BLAST gene sequence comparison, and through MEGA software analysis, compared with the 16S rDNA sequences of similar strains in the database, and a strain 16S rDNA phylogenetic tree was established, as shown in FIG. 2. The result shows that the strain has a closest genetic relationship with Microbacterium xylanilyticum, and the similarity is as high as more than 99%. This strain was thus assigned to the genus Microbacterium xylanilyticum and named MZ-5.

The strain is preserved for a long time in the institute of microbiology of Chinese academy of sciences, and the address is as follows: west road No. 3, north chen chaoyang district, beijing, china, the preservation date: year 2020, 9, 18, accession number: CGMCC No. 20668.

[ example 2 ] degradation characteristics of MZ-5 vs. benzo [ a ] anthracene

1. Degradation characteristics of MZ-5 to benzo [ a ] anthracene under different pH conditions (4-10)

MZ-5 is inoculated in fresh inorganic salt culture solution containing 200mg/L benzo [ a ] anthracene, and is put in a constant temperature incubator with 30 ℃ and 140r/min for enrichment culture to logarithmic phase. Centrifuging the enrichment solution at 6000r/min for 6min, discarding supernatant, resuspending with sterilized phosphate buffer solution, centrifuging again, repeating the operation for three times, adjusting OD600 of bacterial suspension to 0.2, and refrigerating for use.

The pH of the sterilized fresh inorganic salt culture solution containing 100mg/L of benzo [ a ] anthracene was adjusted to pH 4, pH 5, pH 6, pH7, pH 8, pH 9 and pH 10 using 1mol/L HCl (43mL concentrated hydrochloric acid diluted to 500mL with deionized water) and 1mol/L NaOH (4g NaOH dissolved in 100mL deionized water), respectively, and 2% of the suspension was inoculated and continuously cultured in a 30 ℃ and 140r/min incubator at regular intervals, and sampled and analyzed (see fig. 3 (a)). Three replicates were designed for each pH. The results show that MZ-5 achieves optimal degradation when the pH is 5 to 6; degradation of benzo [ a ] anthracene by MZ-5 is inhibited differently when the pH is greater than 6 or less than 5. On the whole, MZ-5 can better degrade benzo [ a ] anthracene under acidic condition, and alkaline condition has obvious inhibition effect on the degradation of benzo [ a ] anthracene.

2. Degradation characteristics of MZ-5 to benzo [ a ] anthracene at different temperatures (15-40℃)

Sterilized fresh inorganic salt culture solution (pH 6) containing 100mg/L benzo [ a ] anthracene was inoculated with 2% of the bacterial suspension, and the suspension was continuously cultured in a constant temperature incubator (140r/min) at 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃ and 40 ℃ respectively, and sampled and analyzed at regular intervals (the result is shown in FIG. 3 (b)). Three replicates were designed for each temperature. The result shows that MZ-5 shows better degradation characteristics at the temperature of 25-35 ℃, wherein 35 ℃ is the optimal temperature; too high or too low of a temperature is not good for MZ-5 to degrade benzo [ a ] anthracene.

3. Degradation characteristics of MZ-5 to benzo [ a ] anthracene under different benzo [ a ] anthracenes (5-200mg/L)

A2% bacterial suspension was inoculated into fresh solutions of inorganic salts (pH 6) having sterilized benzo [ a ] anthracene concentrations of 5mg/L, 10mg/L, 20mg/L, 50mg/L, 100mg/, and 200mg/L, respectively, and the suspension was continuously cultured at 30 ℃ and 140r/min in a constant temperature incubator with sampling analysis at regular intervals (the results are shown in FIG. 3 (c)). Three replicates were designed for each concentration. The result shows that MZ-5 can endure 200mg/L benzo [ a ] anthracene, and the degradation rate can reach 98% within 56 h.

4. Degradation characteristics of MZ-5 to benzo [ a ] anthracene under different bacterial charge (0.1-5% mg/L)

Sterilized fresh solutions of benzo [ a ] anthracene at 100mg/L (pH 6) were inoculated with 0.1%, 0.5%, 1%, 2%, 3%, 5% of each suspension, and continuously cultured in a 30 ℃ and 140r/min incubator at regular intervals, and sampled and analyzed (see fig. 3 (d)). Three replicates were designed for each concentration. The results show that the optimal amount of bacteria added is 2%. When the bacterial dose is low, the microbial biomass is insufficient; when the bacterial dose is higher, the competition among microorganisms is more prominent, so that the degradation rate is inhibited.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Sequence listing

<110> Harbin Industrial university (Shenzhen)

<120> screening and application of benzo [ a ] anthracene degrading bacteria in black and odorous bottom mud

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<211> 1343

<212> PRT

<213> Artificial Sequence (Artificial Sequence)

<220>

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<223> MZ-5

<400> 1

TGAGCAACCT GCCCCTCACT CTGGGATAAG CGCTGGAAAC GGCGTCTAAT ACTGGATACG 60

AGTTGGAGCC GCATGGTTAC CAACTGGAAA GATTTTTTGG TGGGGGATGG GCTCGCGGCC 120

TATCAGCTTG TTGGTGAGGT AATGGCTCAC CAAGGCGTCG ACGGGTAGCC GGCCTGAGAG 180

GGTGACCGGC CACACTGGGA CTGAGACACG GCCCAGACTC CTACGGGAGG CAGCAGTGGG 240

GAATATTGCA CAATGGGCGG AAGCCTGATG CAGCAACGCC GCGTGAGGGA TGACGGCCTT 300

CGGGTTGTAA ACCTCTTTTA GCAGGGAAGA AGCGAAAGTG ACGGTACCTG CAGAAAAAGC 360

ACCGGCTAAC TACGTGCCAG CAGCCGCGGT AATACGTAGG GTGCAAGCGT TATCCGGAAT 420

TATTGGGCGT AAAGAGCTCG TAGGCGGTTT GTCGCGTCTG CTGTGAAATC CCGAGGCTCA 480

ACCTCGGGCC TGCAGTGGGT ACGGGCAGAC TAGAGTGCGG TAGGGGAGAT TGGAATTCCT 540

GGTGTAGCGG TGGAATGCGC AGATATCAGG AGGAACACCG ATGGCGAAGG CAGATCTCTG 600

GGCCGTAACT GACGCTGAGG AGCGAAAGGG TGGGGAGCAA ACAGGCTTAG ATACCCTGGT 660

AGTCCACCCC GTAAACGTTG GGAACTAGTT GTGGGGTCCT TTCCACGGAT TCCGTGACGC 720

AGCTAACGCA TTAAGTTCCC CGCCTGGGGA GTACGGCCGC AAGGCTAAAA CTCAAAGGAA 780

TTGACGGGGA CCCGCACAAG CGGCGGAGCA TGCGGATTAA TTCGATGCAA CGCGAAGAAC 840

CTTACCAAGG CTTGACATAC ACCAGAACAC CGTAGAAATA CGGGACTCTT TGGACACTGG 900

TGAACAGGTG GTGCATGGTT GTCGTCAGCT CGTGTCGTGA GATGTTGGGT TAAGTCCCGC 960

AACGAGCGCA ACCCTCGTTC TATGTTGCCA GCACGTAATG GTGGGAACTC ATGGGATACT 1020

GCCGGGGTCA ACTCGGAGGA AGGTGGGGAT GACGTCAAAT CATCATGCCC CTTATGTCTT 1080

GGGCTTCACG CATGCTACAA TGGCCGGTAC AAAGGGCTGC AATACCGTGA GGTGGAGCGA 1140

ATCCCAAAAA GCCGGTCCCA GTTCGGATTG AGGTCTGCAA CTCGACCTCA TGAAGTCGGA 1200

GTCGCTAGTA ATCGCAGATC AGCAACGCTG CGGTGAATAC GTTCCCGGGT CTTGTACACA 1260

CCGCCCGTCA AGTCATGAAA GTCGGTAACA CCTGAAGCCG GTGGCCTAAC CCTTGTGGAG 1320

GGAGCCGTCG AAGGTGCATT CGT 1343

Claims

1. A strain for degrading benzo [ a ] anthracene, which is named as MZ-5(Microbacterium xylonilyticum), and is preserved in China general microbiological culture Collection center at 9 and 18 days 2020, with the address of No. 3 Hospital, West Lu, North Cheng, Yangxi, China academy of sciences, and the preservation number: CGMCC No. 20668.

2. A screening method for the benzo [ a ] anthracene-degrading strain according to claim 1, comprising the steps of:

(1) taking 5g of black odorous bottom mud at multiple sites of Shenzhen Shenzhou river, adding 500mL of ultrapure water, placing the mixture on a stirrer, stirring for 24h, taking 5mL of suspension, adding the suspension into 145mL of sterilized liquid culture solution taking benzo [ a ] anthracene liquid as a single carbon source, and culturing for 7 days at constant temperature.

(2) After a certain period of incubation, 5mL of the culture broth was added to 145mL of sterilized fresh liquid culture broth, and incubation was continued. Repeating the step for 5 times, and gradually increasing the concentration of the benzo [ a ] anthracene to finally obtain the domesticated benzo [ a ] anthracene degrading flora.

(3) Based on the coating method, the purification and separation of the target strain are carried out by means of a solid culture medium, and the strain for degrading benzo [ a ] anthracene is obtained.

3. The screening method according to claim 2, wherein the benzo [ a ] anthracene-degrading strain is cultured in a liquid medium 1L, the liquid medium comprising the following components in parts by weight:

2.0g(NH₄)₂SO₄，0.2g MgSO₄·7H₂O，0.01g CaCl₂·2H₂O，0.001g FeSO₄·7H₂O，1.5g Na₂HPO₄·12H₂O，1.5g KH₂PO₄，0.004g MnCl₂·4H₂O，0.001g ZnCl₂，0.001g CoCl₄·6H₂O，0.002g NiCl₂·6H₂O，0.0003g CuSO₄·5H₂O。

4. the screening method according to claim 2, wherein the benzo [ a ] anthracene-degrading strain is cultured in a solid medium 1L, the solid medium comprising the following components in parts by weight:

2.0g(NH₄)₂SO₄，0.2g MgSO₄·7H₂O，0.01g CaCl₂·2H₂O，0.001g FeSO₄·7H₂O，1.5g Na₂HPO₄·12H₂O，1.5g KH₂PO₄，0.004g MnCl₂·4H₂O，0.001g ZnCl₂，0.001g CoCl₄·6H₂O，0.002g NiCl₂·6H₂O，0.0003g CuSO₄·5H₂o, 18g agar.

5. The screening method according to claim 3 or 4, wherein the pH of the culture medium/medium is adjusted to about 7.0, the culture medium/medium is sterilized in a sealed state at 121 ℃ for 20 minutes, and then the culture medium/medium is cooled and used for culturing the degrading bacteria.

6. The screening method according to claim 5, wherein the cultivation temperature is 30 ℃, the rotation speed is 140r/min, the cultivation period is 5 to 7 days, and the benzo [ a ] anthracene concentration is 0 to 50mg/L and is not 0.

7. A method for degrading benzo [ a ] anthracene in black and odorous bottom mud, which is characterized in that the method for degrading benzo [ a ] anthracene in the black and odorous bottom mud is applied to the black and odorous bottom mud according to claim 1.