CN109810923B

CN109810923B - Aerobic denitrifying bacterium SLY2-21 for sewage denitrification and application thereof

Info

Publication number: CN109810923B
Application number: CN201910191583.3A
Authority: CN
Inventors: 王晓慧; 杨静丹; 刘琳
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2019-03-14
Filing date: 2019-03-14
Publication date: 2021-02-19
Anticipated expiration: 2039-03-14
Also published as: CN109810923A

Abstract

An aerobic denitrifying bacterium SLY2-21 for sewage denitrification and application thereof belong to the field of environmental microorganism and water treatment biological denitrification, the strain is preserved in China general microbiological culture Collection center (CGMCC) in 2019 for 1 month, and the address is No. 3 of No.1 Siro of Beijing city facing-Yang district, the institute of microbiology of China academy of sciences, the preservation number is as follows: CGMCC No. 17221; the strain is obtained by screening from landfill leachate, can effectively remove ammonia nitrogen and nitrate nitrogen in sewage, can be directly used for denitrification of a river water body after being subjected to expanded culture, has a large application potential in practical engineering, and can play a certain role in promoting environmental protection in the long term.

Description

Aerobic denitrifying bacterium SLY2-21 for sewage denitrification and application thereof

Technical Field

The invention relates to the field of environmental microorganism and water treatment biological denitrification, in particular to an aerobic denitrifying bacterial strain for sewage treatment, and provides denitrification efficiency and practical application of the bacterial strain.

Background

At present, nitrogen pollution is ubiquitous, and the nitrogen forms in the water body comprise protein nitrogen, ammonia nitrogen, organic nitrogen, nitrite nitrogen and nitrate nitrogen, so that the efficient and rapid removal of the nitrogen in the water is an important subject in the field of water pollution prevention and control at present. The theoretical basis of the traditional biological denitrification technology is nitrification and denitrification of microorganisms, but the traditional biological denitrification technology has a plurality of defects, so that the discontinuity and the low efficiency of the denitrification process are caused.

The traditional theory considers denitrification to be a strict anaerobic process, but since the 80 s in the 20 th century, aerobic denitrification bacteria are continuously reported, and the aerobic denitrification is more and more concerned. The biological explanation of the aerobic denitrification phenomenon is that scientists find aerobic denitrifying bacteria existing in the environment and aerobic denitrifying enzyme systems contained in the aerobic denitrifying bacteria, and research on the aerobic denitrifying enzyme systems shows that two nitrate reductases exist in Thiosphaea Pantotropha cells, namely intramembrane nitrate reductase which is combined with cell membranes and periplasmic nitrate reductase which exists between cell walls and cell membranes. Under anaerobic conditions, the expressed enzyme is an intramembrane nitrate reductase (in good condition)It does not work with oxygen); under aerobic conditions, the expressed enzyme is periplasmic nitrate reductase (which is still active at very high DO concentrations). Nitrite reductase (Nir) is an enzyme that plays a major role in the denitrification process, the Nir gene is also the most studied of the denitrification functional genes, and Nir is distributed in the periplasm of the cell membrane and has 2 types: one is cytochrome cd1 type (cd1Nir) and the other is the copper-containing ionic type (CuNir). Nitric oxide reductase binds to cell membrane and catalyzes the reduction of NO to N₂And O, transferring two electrons in the reaction process. Three nitric oxide reductases have been discovered so far: membrane-bound cytochrome bc, mainly present in cells; soluble cytochrome P450, found mainly in fungi; flavoprotein A-form, found in non-denitrifying bacteria. The nitrous oxide reductase is located in periplasmic space of the membrane, and is a soluble copper ion-containing enzyme₂Reduction of O to N₂It is the last step of the denitrification process. Robertson et al believe that co-respiration is an important mechanism of aerobic denitrification, i.e., denitrifying bacteria can transfer electrons from the reduced species to oxygen and also to nitrate.

So far, the species are found to be single, and the research mostly focuses on the aspects of degradation genes and degradation mechanisms, so that the practical application research is limited. Therefore, the strain with high-efficiency aerobic denitrification efficiency is screened from the nature, and the growth characteristic, denitrification characteristic and application thereof in sewage denitrification are deeply researched. Further explores the strain resources of the aerobic denitrifying bacteria, provides materials for the research on the denitrification mechanism of the aerobic denitrifying bacteria in the future, and has important theoretical significance and good application prospect.

Disclosure of Invention

One of the purposes of the invention is to provide an aerobic denitrifying bacterium (Achromobacter marplanensis) SLY 2-21. The strain can effectively degrade nitrate nitrogen and ammonia nitrogen in a water body under an aerobic condition, but cannot degrade nitrite nitrogen, and provides an efficient bacterial preparation for biological enhancement of a sewage biological denitrification process.

The invention also aims to provide the application efficiency of the strain SLY2-21 in the denitrification of river sewage.

In order to achieve the purpose, the invention adopts the following technical scheme:

an aerobic denitrifying bacterium (Achromobacter marplatenisis) SLY2-21, identified as Achromobacter marplatenisis by 16S rDNA, belongs to Achromobacter, and has been preserved in China general microbiological culture Collection center (address: Beijing, North Cheng Xilu No.1 Hospital, No. 3, postal code 100101), with a preservation date of 2019, 1 month and 21 days, and a preservation number of CGMCC No. 17221.

The aerobic denitrifying bacterium SLY2-21 provided by the invention is biologically characterized in that the aerobic denitrifying bacterium SLY2-21 is identified as a gram-negative bacterium, is milky white, is regular in a circle, has a smooth and moist surface, is easy to pick up, and has a rod-shaped thallus, the length of 1-2 um and the width of 0.3-0.5 um. Heterotrophic growth, an optimal carbon source of sodium citrate, an optimal C/N15, an optimal pH value of 7.0-8.0 and an optimal temperature of 30 ℃.

The invention provides a method for screening aerobic denitrifying bacteria.

The strain screening method combines various screening methods, firstly, the aerobic denitrifying bacteria are enriched through an LB culture medium, and then, the aerobic denitrifying bacteria are quickly and effectively screened by adding a pH indicator into the culture medium.

In order to achieve the purpose, the steps of the technical scheme adopted by the invention are sampling, LB enrichment culture, primary screening and secondary screening in sequence, and finally the strain which can degrade nitrate nitrogen and ammonia nitrogen in sewage simultaneously under aerobic condition and has higher denitrification capability is obtained.

Taking the landfill leachate, firstly carrying out enrichment culture on an LB (lysogeny broth) culture medium, and adopting a Grignard reagent to preliminarily screen aerobic denitrifying bacteria; then according to the property of the denitrifying bacteria for producing alkali, an indicator of bromothymol blue is added into the culture medium to effectively screen the aerobic denitrifying bacteria; and after heterotrophic nitrification and enrichment, re-screening the autotrophic denitrifying bacteria with high denitrification capacity by using simulated sewage.

The invention provides a method for identifying strains.

The strain identification method is mainly characterized in that a 16S rDNA identification method is adopted, a general primer is used for amplifying a conservative 16S rDNA fragment in the evolution process to perform sequencing, then the sequencing is compared with data in a gene library, the attribute of the strain is determined according to the strain homology ratio, and finally the confirmation is performed according to a phylogenetic tree.

The aerobic denitrifying bacteria of the invention are applied to degrading nitrate nitrogen and ammonia nitrogen in polluted water. Specifically, the bacteria are inoculated to water polluted by nitrate nitrogen and ammonia nitrogen after being subjected to amplification culture.

Due to the adoption of the technical scheme, the invention has the remarkable technical effects that:

the strain provided by the invention can effectively remove nitrate nitrogen and ammonia nitrogen in sewage, aerobic denitrifying bacteria are expanded and cultured and then are put into a water body containing nitrate nitrogen according to the proportion of 2%, and the aerobic denitrifying bacteria are expanded and cultured and then are put into a water body containing ammonia nitrogen according to the proportion of 2%, so that the removal rate of nitrate nitrogen is 98.78%, and the removal rate of ammonia nitrogen is 63.03%, and the strain has wide application prospects in the development of denitrification microbial agents or sewage treatment agents.

Biological material preservation information

Name of the biomaterial: SLY2-21(Achromobacter marplantensis);

the preservation unit: china general microbiological culture Collection center;

the preservation date is as follows: year 2019, month 1, day 21;

the preservation number is: CGMCC No. 17221.

Drawings

FIG. 1 is an electron micrograph of SLY2-21 strain.

FIG. 2 is a phylogenetic tree of the strain 16S rDNA of the present invention.

FIG. 3 shows the heterotrophic nitrification growth and denitrification efficiency of aerobic denitrifying bacteria.

FIG. 4 shows the aerobic denitrification growth and denitrification efficiency of aerobic denitrifying bacteria.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention will be described in further detail with reference to the following figures 1 to 4 and examples:

example 1

The screening of the aerobic denitrifying bacteria comprises the following specific steps:

1. domestication and enrichment: inoculating 10mL of the thoroughly mixed fresh landfill leachate into a 250mL conical flask of 100mL LB culture medium, placing the conical flask on a shaker at 30 ℃ and 150rpm, culturing for 48h, and sampling every 12h to qualitatively detect N0 in the culture medium₃ ^--N and NO₂ ^--the content of N. 10mL of the enriched culture solution was transferred to a fresh LB liquid medium for 5 times, and the total enrichment was 10 days.

Respectively and qualitatively detecting N0 in the culture medium by diphenylamine reagent and Grignard reagent every 12h₃ ^--N and NO₂ ^--the content of N. 3 drops of culture solution are absorbed into a sterilized test tube by a sterilized dropper, and 3 drops of Grignard reagent are added into the test tube, if the culture solution becomes pink or brown, the existence of nitrite is proved, the nitrite is positive for nitrate reduction, and the strain can be aerobic denitrifying bacteria. If the color is colorless, the sterilized test tube is taken out and 3 drops of culture solution and 3 drops of diphenylamine reagent are dripped, if the culture solution is changed into blue, the existence of nitrate is proved, the nitrate is not converted into nitrite, the reaction is negative, the strain is probably not aerobic denitrifying bacteria, the strain is discarded, and the test result is changed into pink when meeting the Grignard reagent.

The griiss reagent solution a: sulfanilic acid 0.5g was dissolved in 150mL of acetic acid (30%) in a brown bottle; and B, liquid B: adding 0.5g of 1-naphthylamine into 50mL of distilled water, boiling, slowly adding 150mL of 30% diluted acetic acid, and storing in a brown bottle; the solutions A, B were mixed in equal volumes before use.

Diphenylamine reagent: 1g of diphenylamine dissolved in 20ml of distilled water was slowly added to 100ml of concentrated H₂SO₄In a brown bottle.

The enrichment medium LB (g/L): tryptone 1.0; fermentation method0.5 of mother extract; KNO₃2.0; the pH value is 7.2.

2. Separating and purifying

Taking l0mL enriched domestication liquid, transferring into a conical flask containing 90mL sterile water, shaking, mixing, diluting according to multiple ratio to obtain 10^-1,10^-2,10^-3,10^-4,10^-5,10^-6，10^-7The dilution of (A) is selected to have a gradient of 10^-4,10^-5,10^-6，10^-7(ii) a And respectively taking 1mL of diluted bacterium liquid, coating the diluted bacterium liquid on a BTB culture medium, placing the BTB culture medium in a constant temperature incubator, and culturing for 2-3 d at the temperature of 30 ℃. The aerobic denitrifying bacteria can use nitrate to produce alkalinity, thereby turning the culture medium around the colonies blue. Observing single bacterial colony on BTB culture medium, changing bacterial colony into blue or generating halo around bacterial colony, namely, primary screening aerobic denitrifying bacteria, selecting single bacterial colony with different forms and changing into blue to perform streak purification for many times, obtaining basically consistent bacterial colony characteristics after 5 generations of purification, and obtaining 16 primary screening bacterial strains. Then inoculated in a slant culture medium at 4 ℃ and stored for subsequent experiments.

The BTB prescreening culture medium comprises: agar 20g, KNO₃ 1g、FeSO₄·7H₂O 0.05g、CaCl₂·2H₂O 0.2g、MgSO₄·7H₂O1 g, sodium succinate 8.5g, KH₂PO₄1g of bromothymol blue (0.1 g of bromothymol blue is dissolved in 10mL of alcohol) 1mL, the volume is determined to be 1000mL by using distilled water after the bromothymol blue is dissolved, and the pH value is adjusted to 7.0-7.3 by using 1mol/L of NaOH.

3. Double sieve

Inoculating the purified strain into LB culture medium for amplification culture, centrifuging at 4000rpm for 5min, discarding supernatant, preparing bacterial suspension (OD value is about 1.5) with sterile water, inoculating into a conical flask containing heterotrophic nitrification liquid culture medium according to 2% inoculum size, and performing shake culture at 30 deg.C and 150rpm for 36h to perform heterotrophic nitrification enrichment.

Inoculating the bacterial suspension after the heterotrophic nitrification enrichment into 250mL conical flasks respectively filled with 100mL of heterotrophic nitrification culture medium and aerobic denitrification culture medium by 5 percent of inoculum size again, performing shake culture at 30 ℃ and 150rpm for 5 days, and detecting NH before and after inoculation₄ ⁺-N and NO₃ ^--concentration variation of N. The strain with ammonia nitrogen removal rate of 60.21% and nitrate nitrogen removal rate of 98.86% was selected as the target strain for further study.

The heterotrophic nitrification medium (NI) (g/L): c₄H₄Na₂O₄·6H₂O 11；MgSO₄·7H₂O 0.1；Na₂HPO₄·12H₂O 6.7；KH₂PO₄ 1；NH₄Cl 1.5; 2mL of trace element solution; the pH value is 7.0-7.3.

The above Denitrifying Medium (DM) (g/L): c₄H₄Na₂O₄·6H₂O 13；MgSO₄·7H₂O 0.1；Na₂HPO₄·12H₂O 7.9；KH₂PO₄ 1.5；KNO ₃3; 2mL of trace element solution; the pH value is 7.0-7.3.

The above trace element solution (g/L): EDTA 50; ZnSO₄ 2.2；CaCl₂ 5.5；MnCl₂·4H₂O 2.06；FeSO₄·7H₂O 5.0；(NH₄)₆Mo₇O₂₄·4H₂O 1.1；CuSO₄·5H₂O 1.57；CoCl₂·6H₂O1.61; the pH value is 6.0.

Example 2

Molecular biological identification of aerobic denitrifying bacteria SLY 2-21:

the aerobic denitrifying bacterium SLY2-21 with good denitrification effect is obtained after screening and separation, the strain is gram-negative, milky white and regular in round shape through physiological and biochemical tests, the surface is smooth and wet and is easy to pick up, and SEM scanning shows that the SLY2-21 thallus is rod-shaped, and the size of the thallus is 1-2 um multiplied by 0.3-0.5 um (shown in figure 1).

1. Bacterial genomic DNA extraction

Inoculating a target strain into an LB culture medium, culturing overnight, centrifuging 1mL to obtain thalli, extracting bacterial genome by using a genome kit, performing PCR amplification, performing agarose gel electrophoresis (1%) verification, and checking an electrophoresis result by using an ultraviolet analyzer.

2. PCR amplification of 16SrDNA fragment

PCR reaction was performed using the universal primers (27f: 5'-AGAGTTTGATCCTGGCTCAG-3', 1492 r: 5'-GGTTACCTTGTTACGACTT-3'), followed by agarose gel electrophoresis (1%) validation, and the electrophoresis results were checked by an ultraviolet analyzer.

PCR reaction system (total volume 50. mu.l): 10 XEx Taq buffer 5.0. mu.l; 2.5mM dNTP Mix 4.0. mu.l; 10p Primer 11.0. mu.l; 10p Primer 21.0. mu.l; template 2.0. mu.l; 5u Ex Taq 0.5u l; ddH₂O 36.5μl。

And (3) PCR reaction conditions: pre-denaturation at 95 ℃ for 5 min; denaturation at 95 ℃ for 30 s; annealing at 54 ℃ for 30 s; extension at 72 ℃ for 1min30 s; the second step was repeated for 30 cycles; final extension at 72 deg.C for 1 time in 10 min; infinity at 4 ℃.

3. Electrophoresis detection, gel cutting, purification and sequencing, and sequencing by the Merginia organisms.

The sequence length of the strain SLY2-21 is 1420, and the gene sequence table is shown in SEQ ID NO: 1.

the fragments obtained by sequencing are compared in an EzBioCloud database, and the result shows that the strain has higher similarity with the 16S rDNA sequence of Achromobacter marplatenis, and the similarity is 99.31%. A phylogenetic tree is constructed by adopting a Mega7.0 software ortho-position linkage (NJ) method to analyze the genetic characteristics of the strain, the species condition of the strain and the evolutionary position of the strain in genetics are determined, and the result is shown in figure 2.

Example 3

Growth and denitrogenation characteristics of SLY2-21 Strain:

1. the SLY2-21 strain preserved in a refrigerator at 4 ℃ is inoculated in LB culture medium at 30 ℃ and is subjected to amplification culture at 150rpm, a bacterial suspension with the OD being about 1.5 is prepared by sterile water, and then the bacterial suspension is inoculated in a 250mL conical flask containing 100mL heterotrophic nitrification culture medium according to the inoculum concentration of 2 percent, is fully and uniformly mixed, and is subjected to shake culture at 30 ℃ and 150rpm for 96 hours. Periodically sampling and measuring NH in supernatant respectively₄ ⁺-N，OD₆₀₀The value is obtained. To reduce errors, three parallel tests were set up and the results are shown in FIG. 3.

As can be seen from the curve, the SLY2-21 strain enters the logarithmic phase after 12h of growth in the nitrification medium, enters the stationary phase after about 27h, and enters the small stationary phase after a small period of timeThen entering the decline period. NH while the strain is growing₄ ⁺Decrease in N concentration, NH at log phase₄ ⁺N concentration decreases fastest, NH after stationary phase₄ ⁺Slow decrease of-N concentration, NH₄ ⁺the-N removal rate was 63.03%, and since this bacterium was a heterotrophic bacterium, it was presumed that the carbon source was decreased.

2. The SLY2-21 strain preserved in a refrigerator at 4 ℃ is inoculated in LB culture medium at 30 ℃ and expanded at 150rpm, then a bacterial suspension with OD about 1.5 is prepared by sterile water, and then the bacterial suspension is inoculated in a 250mL conical flask containing 100mL aerobic denitrification culture medium according to the inoculum size of 2 percent, and is fully and evenly mixed, and is cultured for 96 hours at 30 ℃ and 150rpm by a shaking table. Respectively and periodically sampling to determine NO in supernatant₃ ^--N、NO₂ ^--N、OD₆₀₀The value is obtained. To reduce errors, three parallel experiments were set up and the results are shown in fig. 4.

According to the curve, the SLY2-21 strain enters the logarithmic phase after growing in the aerobic denitrification culture medium for 15 hours, which is probably because the nitrate nitrogen concentration of the LB culture medium is similar to that of the denitrification culture medium, and the strain has better adaptability. From OD₆₀₀And NO₃ ^-The relation of-N removal is known that aerobic denitrification occurs mainly in the log phase, NO by 30h, since the strain grows fastest in the log phase and cell synthesis and metabolism are mainly in this phase₃ ^-The concentration of N is stable, and the removal rate reaches 98.78%. However, during the whole denitrification process, the nitrite state is accumulated to a certain extent, which is probably related to the selected carbon source and the carbon-nitrogen ratio.

Example 4

The application of aerobic denitrifying bacteria SLY2-21 in actual sewage treatment:

adding the aerobic denitrifying strain SLY2-21 into sewage of Tianjin river according to the strain adding amount of 1% for aeration denitrification treatment. The quality of inlet water is as follows: ammonia nitrogen 7.41 mg.L^-10.009 mg.L of nitrite nitrogen^-1Nitrate nitrogen 0, total nitrogen 10.08 mg.L^-1Supplementing KNO in river wastewater₃So that the nitrate nitrogen is 10 mg.L^-1. Blank group A was not treated, group B was supplemented with sodium citrate (as C/N15), group CSodium citrate was added with 1% bacterial suspension. All are subjected to aeration culture at the optimum temperature of 30 ℃, and sampling is carried out every 12h to determine the contents of ammonia nitrogen, nitrite, nitrate nitrogen and total nitrogen. The results are shown in Table 1.

TABLE 1 ability of the strains to remove nitrogen from river wastewater

After 24 hours of reaction, the ammonia nitrogen removal rate of the control group A without adding denitrifying bacteria is only 55.2 percent, the nitrate nitrogen removal rate is 10.27 percent, and the total nitrogen removal rate is 9.32 percent; only adding the group B of carbon sources, wherein the ammonia nitrogen removal rate is 89.57%, the nitrate nitrogen removal rate is 27.15%, and the total nitrogen removal rate is 31.89%; after the carbon source and the denitrifying bacteria are added into the group C, the ammonia nitrogen removal rate is 96.76%, the nitrate nitrogen removal rate is 43.71%, and the total nitrogen removal rate is 36.41%; in the three groups, a small amount of nitrite is accumulated, and compared with a control group, the denitrification efficiency of the sewage can be obviously improved by adding the denitrifying bacteria. The results show that the strain can obtain better sewage treatment effect and has better application prospect when being used for wastewater treatment.

Sequence listing of strain SLY2-21, SEQ ID NO: 1:

sequence listing

<110> Beijing university of chemical industry

<120> aerobic denitrifying bacterium SLY2-21 for sewage denitrification and application thereof

<160> 1

<170> SIPOSequenceListing 1.0

<210> 1

<211> 1420

<212> DNA

<213> aerobic denitrifying bacteria (Achromobacter marplantensis SLY2-21)

<400> 1

cctaccgtgg gtatcgcccc ccttgcggtt aggctaacta cttctggtaa aacccactcc 60

catggtgtga cgggcggtgt gtacaagacc cgggaacgta ttcaccgcga catgctgatc 120

cgcgattact agcgattccg acttcacgca gtcgagttgc agactgcgat ccggactacg 180

atcgggtttc tgggattggc tccccctcgc gggttggcga ccctctgtcc cgaccattgt 240

atgacgtgtg aagccctacc cataagggcc atgaggactt gacgtcatcc ccaccttcct 300

ccggtttgtc accggcagtc tcattagagt gccctttcgt agcaactaat gacaagggtt 360

gcgctcgttg cgggacttaa cccaacatct cacgacacga gctgacgaca gccatgcagc 420

acctgtgttc cggttctctt gcgagcactg ccaaatctct tcggcattcc agacatgtca 480

agggtaggta aggtttttcg cgttgcatcg aattaatcca catcatccac cgcttgtgcg 540

ggtccccgtc aattcctttg agttttaatc ttgcgaccgt actccccagg cggtcaactt 600

cacgcgttag ctgcgctacc aaggcccgaa ggccccaaca gctagttgac atcgtttagg 660

gcgtggacta ccagggtatc taatcctgtt tgctccccac gctttcgtgc atgagcgtca 720

gtgttatccc aggaggctgc cttcgccatc ggtgttcctc cgcatatcta cgcatttcac 780

tgctacacgc ggaattccac ctccctctga cacactctag cccggtagtt aaaaatgcag 840

ttccaaagtt aagctctggg atttcacatc tttctttccg aaccgcctgc gcacgcttta 900

cgcccagtaa ttccgattaa cgcttgcacc ctacgtatta ccgcggctgc tggcacgtag 960

ttagccggtg cttattctgc aggtaccgtc agtttcacgg ggtattagcc catgacgttt 1020

ctttcctgcc aaaagtgctt tacaacccga aggccttcat cgcacacgcg ggatggctgg 1080

atcagggttt cccccattgt ccaaaattcc ccactgctgc ctcccgtagg agtctgggcc 1140

gtgtctcagt cccagtgtgg ctggtcgtcc tctcaaacca gctacggatc gtcgccttgg 1200

tgagccgtta ccccaccaac tagctaatcc gatatcggcc gctccaatag tgcaaggtct 1260

tgcgatcccc tgctttcccc cgtagggcgt atgcggtatt agctacgctt tcgcgtagtt 1320

atcccccgct actgggcacg ttccgataca ttactcaccc gttcgccact cgccaccaga 1380

ccgaagtccg tgctgccgtt cgactgcatg tgtaagcatc 1420

Claims

1. An aerobic denitrifying bacterium SLY2-21, which is identified as Achromobacter marplatenis by 16S rDNA molecule and is preserved in China general microbiological culture Collection center, the preservation address is No. 3 of Xilu No.1 of Beijing Korean district, the preservation date is 1 month and 21 days in 2019, and the preservation number is CGMCC No. 17221.

2. The use of the aerobic denitrifying bacterium SLY2-21 of claim 1 for degrading and removing nitrate nitrogen and ammonia nitrogen in sewage.

3. The application of the aerobic denitrifying bacterium SLY2-21 of claim 2, wherein the aerobic denitrifying bacteria are respectively added into the water containing nitrate nitrogen and ammonia nitrogen in a proportion of 2% after being expanded and cultured.

4. The application of the aerobic denitrifying bacterium SLY2-21 of claim 2, wherein the aerobic denitrifying bacterium is added into the actual river sewage in a proportion of 1% after being subjected to expanded culture.