CN117887593A - Mixed nutrition type denitrifying bacterium Penicillium sp.N8 and application thereof - Google Patents

Abstract

The present invention belongs to the technical field of water pollution control, specifically to a mixed-trophic denitrifying bacterium Penicillium sp.N8 and its application. The strain is preserved in the China Type Culture Collection, the preservation address is Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, the preservation number is CCTCC M 20232691, the preservation date is December 27, 2023, and it is identified as Penicillium.

Description

A mixed nutritional denitrifying bacterium Penicillium sp. N8 and its application

Technical Field

The present invention relates to the technical field of water pollution control, and in particular to a mixed-trophic denitrifying bacterium Penicillium sp. N8 and an application thereof.

Background technique

Current research shows that most surface water bodies are in a state of micro-pollutation. Water bodies with concentrations of pollutants such as nitrates and organic matter below 10 mg/L are called micro-polluted water bodies. Control of endogenous pollutants in micro-polluted lakes and reservoirs, especially nitrogen pollution, is a key way to inhibit eutrophication of water bodies. In response to the hazards of nitrate accumulation, physical, chemical, and biological removal methods have achieved certain results. Among them, biological removal methods are widely used because of their high efficiency and economy. Biological denitrification technology involves aerobic denitrification reactions. Aerobic denitrification reactions have strong tolerance to dissolved oxygen, moderate cost, high treatment efficiency, and clean byproducts that are harmless to the environment, making it a hot topic in current denitrification research.

Fungi play an important role in the nitrogen cycle. They can not only mineralize organic nitrogen and assimilate inorganic nitrogen to enable cell growth, but some fungi can also reduce nitrates or nitrites to gaseous nitrogen compounds through denitrification or co-denitrification. Compared with other microorganisms, fungi have two main advantages in denitrification: first, they have a higher denitrification rate and a stronger ability to decompose organic matter; second, fungal spores have complex cell walls, which increase the resistance of fungi to toxic compounds and harsh environments (such as lower pH and higher temperature).

The reduction of organic pollutants and the low concentration of organic matter lead to low aerobic denitrification efficiency, while the addition of additional carbon sources may introduce secondary pollution; oxygenating the water body cannot fundamentally improve the water quality, so it is necessary to provide a way to improve the denitrification efficiency.

Summary of the invention

In order to solve the above technical problems, the present invention provides a mixed-trophic denitrifying bacterium Penicillium sp. N8 and its application, which solves the technical problem that the efficiency of biological denitrification treatment of micro-polluted water bodies in the prior art needs to be further improved.

A mixed-trophic denitrifying bacterium Penicillium sp. N8, preserved by the China Type Culture Collection, with the preservation address at Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, the preservation number is CCTCC M 20232691, and the preservation date is December 27, 2023.

The application of the mixed nutritional denitrifying bacteria Penicillium sp. N8 in the remediation of nitrogen-containing water bodies.

Preferably, the remediation of nitrogen-containing water bodies is to remove nitrogen from the water bodies.

Preferably, the remediation of nitrogen-containing water bodies is carried out in the presence of an electron donor.

Preferably, when repairing nitrogen-containing water bodies, the usage amount of the mixed nutritional denitrifying bacteria Penicillium sp. N8 is 1-5% based on the mass fraction of the nitrogen-containing water body.

Preferably, the carbon-nitrogen ratio in the nitrogen-containing water is 1-2.5.

Preferably, the temperature of the nitrogen-containing water is 25-30°C.

Preferably, the flow rate of the nitrogen-containing water is 80-160 rpm.

Preferably, the dosage of iron is 10-15 g/L.

A method for treating nitrate in polluted water comprises inoculating the mixed trophic denitrifying bacteria Penicillium sp. N8 into the nitrogen-containing water body and adding iron as an electron donor.

The present invention also has the following technical features:

The culture medium of the aerobic denitrifying fungus is light yellow and divergent. Using ITS sequencing technology and a phylogenetic tree based on the neighbor joining method, it was found that the gene sequence similarity between Penicillium goetzii and Penicillium sp. N8 exceeded 99%, indicating that N8 belongs to the genus Penicillium.

The application method includes: setting different inorganic electron donor iron dosages, 0, 5, 10, 15, 20 g/L; different C/N, 1, 1.5, 2.5; different rotation speeds, rpm=40, 80, 160 and different temperatures, T=5, 10, 15, 20°C, to explore the denitrification performance under different environmental conditions; and then using a kinetic model to explore the joint effects of changes in C/N, rpm and temperature on the denitrification effect.

Compared with the prior art, the present invention has the following beneficial effects:

The aerobic denitrifying fungi of the present invention, when C/N decreases from 2 to 1.5 and 1, the TN removal rate of strain N8 decreases from 100% to 90% and 95%; with the continuous increase of the oscillation speed, the denitrification rate of strain N8 continues to increase, and the nitrate removal rate can reach 100% at 160rpm; with the gradual decrease of temperature, the TN removal rate of strain N8 decreases from 93.36% to 75.34%, 50.80% and 29.18%; in addition, the denitrification rate under the changes of C/N, rpm and temperature is more consistent with the half-order rate equation, indicating that the reaction rate is affected by the external environmental conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the phylogenetic tree (a) and strain morphology (b) of aerobic denitrifying fungi Penicillium sp. N8;

Figure 2 shows the denitrification performance of Penicillium sp.N8 under different iron dosages, including (a) change in nitrate nitrogen concentration; (b) change in nitrite nitrogen concentration; (c) change in ammonia nitrogen concentration; (d) change in total nitrogen concentration;

Figure 3 shows the denitrification performance of Penicillium sp.N8 at different carbon-nitrogen ratios, where (a) the carbon-nitrogen ratio is 1, (d) the carbon-nitrogen ratio is 1.5, and (c) the carbon-nitrogen ratio is 2.5;

Figure 4 shows the denitrification performance of Penicillium sp.N8 at different rotation speeds, where (a) rpm = 40, (b) rpm = 80, and (c) rpm = 160;

Figure 5 shows the denitrification performance of Penicillium sp. N8 at different temperatures, where (a) T = 5, (b) T = 10, (c) T = 15, and (d) T = 20;

Figure 6 shows the zero-order (a), half-order (b) and first-order (c) kinetic models of aerobic denitrifying fungi at different C/N; the zero-order (d), half-order (e) and first-order (f) kinetic models of strain N8 at different rpm; the zero-order (g), half-order (h) and first-order (i) kinetic models of strain N8 at different temperatures;

Figure 7 shows the denitrification, cell growth and DOC removal of aerobic denitrifying fungi under optimal conditions, where (a) is a denitrification performance graph, and (b) is a result graph of cell growth and DOC removal;

Figure 8 shows the release of Fe ³⁺ and Fe ²⁺ in the aerobic denitrifying fungi system;

Figure 9 shows the nitrate removal kinetic model of aerobic denitrifying fungi under different parameters.

Detailed ways

The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

The fungal culture medium (DRBC) adopts the Bengal Rose Red Agar medium known in the prior art, and its formula is: 5g/L peptone, 0.025g/LC ₂₀ H ₂ C _l4 I ₄ Na ₂ O ₅ , 10g/LC ₆ H ₁₂ O ₆ , 0.002g/LC ₆ H ₄ Cl ₂ N ₂ O ₂ , 1 g/L KH ₂ PO ₄ , 0.1g/LC ₁₁ H ₁₂ Cl ₂ N ₂ O ₅ , 0.5g/L MgSO ₄ , pH is 5.6-5.8. The fungal solid culture medium is based on the above formula and 20g/L agar powder is added.

The denitrification liquid medium (DM) adopts the conventional denitrification liquid medium known in the prior art, and its formula and preparation method are as follows: KNO ₃ is 0.108 g/L, KH ₂ PO ₄ is 1.5 g/L, glucose is 0.413 g/L, MgSO ₄ ·7H ₂ O is 0.1 g/L, Na ₂ HPO ₄ ·12H ₂ O is 5.0 g/L, and trace element mother solution is 2 mL; the above components are added to ultrapure water to make up to 1 L, stirred until completely dissolved, and then the pH value is adjusted to 7.0-7.2, and sterilized at 121°C for 30 minutes before use.

The formula and preparation method of the above-mentioned trace element mother solution are as follows: 4.4 mg of _ZnSO4 , 100 mg of ethylenediaminetetraacetic acid, 10.2 mg of _MnCl2 · _4H2O , 11 mg of _CaCl2 , 10 mg of _FeSO4 · _7H2O , 3.2 mg of _CuSO4 · _5H2O , 2.2 mg of ( _NH4 ) _6Mo7O24 · _4H2O , and 3.2 mg of _CoCl2 · _6H2O ; add _the above-mentioned components into ultrapure water and make up to 1L, stir until completely dissolved, then adjust _the pH value to 7.0-7.2, and sterilize at 121°C for 30 minutes for use.

The "iron" mentioned in the present invention is zero-valent iron, which can be zero-valent iron powder or iron rod.

Example 1

The screening and identification method of aerobic denitrifying fungi specifically comprises the following steps:

Step 1: Enrichment of aerobic denitrifying fungi:

Water samples were collected from the reservoir at 0.5 m, and 100 mL of the water sample was filtered through a 0.22 μm filter membrane to enrich the fungi. The filter membrane was then attached to a DRBC solid culture medium plate. The culture dish was inverted in a biochemical incubator and cultured at 30°C for 3-4 days until colonies were formed on the culture medium.

Step 2: Screening of aerobic denitrifying fungi:

(1) After colonies are formed on the culture dish, use an inoculation loop to scrape the fungal colonies on the DRBC into a 150 mL conical flask containing 100 mL of low C/N (C/N=2) denitrification liquid medium (DM) (n=3). This is the case without the addition of inorganic electron donors.

(2) Add 1.0 g/L of inorganic electron donors to the shaker for 1 h, and use an inoculation loop to scrape the fungal colonies on the same DRBC into another 150 mL conical flask containing 100 mL of low C/N (C/N = 2) DM medium (n = 3) to eliminate the stress of inorganic electron donors on the fungi.

The two conical flasks were cultured at 30℃ and 125±5 rpm. Samples were taken every 24 hours for 3 days. The concentrations of nitrate nitrogen and nitrite nitrogen were measured after passing through a 0.45μm membrane. The two were compared, and fungi with a certain nitrate removal rate in the absence of inorganic electron donors and a nitrate removal rate greater than 80% in the presence of inorganic electron donors were selected for further study.

Step 3, strain identification:

The selected efficient aerobic denitrifying fungi were subjected to Sanger sequencing. After sequencing determined the corresponding species of the fungi, the fungi were named and numbered, and stored in 50% glycerol (1:1) at -20°C for further study.

PCR was performed using primers.

The primers are:

ITS1: 5'-TCCGTAGGTGAACCTGCGG-3', recorded as SEQ ID NO.2,

ITS4: 5’-TCCTCCGCTTATTGATATGC-3’, SEQ ID NO.3.

The PCR reaction system (25 µL) was as follows: genomic DNA template was 20-50 ng/µL, PCR Premix was 12.5 µL, primer ITS1 (10 µM) was 1 µL, primer ITS4 (10 µM) was 1 µL, and ddH ₂ O was 9.5 μ L.

The PCR program was: 95°C, 5 min; 94°C, 30 s; 57°C, 30 s; 72°C, 90 s; 30 cycles of amplification, followed by 72°C extension for 10 min. After the PCR, the 16S rDNA fragment was obtained, and its 16S rDNA nucleotide sequence was obtained after sequencing, specifically:

CTGCGGAAGGATCATTACCGAGTGAGGGCCCTCTGGGTCCAACCTCCCACCCGTGTTTATTTTACCTTGTTGCTTCGGCGGGCCCGCCTTAACTGGCCGCCGGGGGGCTTACGCCCCCGGGCCCGCCCGCCGAAGACACCCTCGAACTCTGTCTGAAGATTGTAGTCTGAGTGAAAATATAAATTATTTAAAACTTTCAACAACGGATCTCTTGGTTCCGGCATCGATGAAGAACGCAGCGAAATGCGATACGTAATGTGAATTGCAAATTCAG TGAATCATCGAGTCTTTGAACGCACATTGCGCCCCCTGGTATTCCGGGGGGCATGCCTGTCCGAGCGTCATTTCTGCCCTCAAGCACGGCTTGTGTGTTGGGCCCCGTCCTCCGATCCCGGGGGACGGGCCCGAAAGGCAGCGGCGGCACCGCGTCCGGTCCTCGAGCGTATGGGGCTTTGTCACCCGCTCTGTAGGCCCGGCCGGCGCTTGCCGATCAACCCAAATTTTTATCCAGGTTGACCTCGGATCAGGTAGGGATACCCGCTGA, which is recorded as SEQ ID NO.1. The sequence starts from the 5' end and ends at the 3' end.

The comparison result of the above 16S rDNA nucleotide sequence is shown in Figure 1. As can be seen from Figure 1, the 16S rDNA nucleotide sequence has a similarity of more than 99% with Penicillium goetzii and belongs to Penicillium sp. (Penicillium), and is named Penicillium sp. N8. The preservation unit is China Center for Type Culture Collection, the preservation address is Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan City, the preservation number is CCTCC M 20232691, and the preservation date is December 27, 2023.

Example 2

In this example, the aerobic denitrification ability of aerobic denitrifying fungi Penicillium sp. N8 (hereinafter referred to as N8) was tested. Fungi N8 with a mass concentration of 1% were inoculated into sterilized DM medium with N=5mg/L, and different iron dosages, carbon-nitrogen ratios, rotation speeds, and temperatures were set. Samples were taken every 2 days and filtered through a pre-combusted 0.45 μm GF/F glass fiber filter to determine the concentrations of nitrate nitrogen (NO ₃ ^- -N), nitrite nitrogen (NO ₂ ^- -N), ammonia nitrogen (NH ₄ ⁺ -N), and total nitrogen (TN) in each system, as follows:

(1) Under the conditions of C/N=2, temperature of 30℃ and rotation speed of 120rpm, the effect of different iron dosages (0, 5, 10, 15, 20g/L, i.e., 0, 5, 10, 15, 20g of zero-valent iron powder were added per liter of treated water, respectively) on the nitrogen removal efficiency.

As shown in Figure 2, without adding exogenous inorganic electron donors, the nitrate removal rate of N8 in the culture medium with C/N=2 was about 55%, and no obvious nitrite accumulation was observed. With the increase of iron dosage, the nitrate removal rate of N8 gradually increased, and complete removal could be achieved in 6 days at the maximum dosage; but at the same time, the accumulation of ammonia nitrogen continued to increase, indicating that the proportion dominated by the chemical action of iron was gradually increasing. Based on the above situation, the nitrate removal rate was fast, and ammonia nitrogen accumulated in small amounts but could eventually be removed by nitrification. 10g/L dosage was selected as the optimal dosage.

(2) Under the conditions of iron dosage of 10 g/L, temperature of 30°C and rotation speed of 120 rpm, the effects of different C/N ratios (1, 1.5 and 2.5) on nitrogen reduction of N8 were investigated.

As shown in Figure 3, when C/N decreased from 2.5 to 1.5 and 1, the removal rate of TN by strain N8 decreased from 100% to 90% and 95%, and nitrate nitrogen could be completely removed. However, ammonia nitrogen re-accumulated in the later stage of culture. The reason may be that the cells died after entering the decay period, resulting in the release of ammonia nitrogen. It also shows that the available organic carbon of the strain is low under low C/N conditions, which may limit its denitrification activity and cell activity. As C/N increased to 2.5, the removal rate of TN by strain N8 reached complete removal on the 10th day, and there was no accumulation of ammonia nitrogen in the later period, indicating that increasing C/N can promote its TN removal efficiency. Considering the oligotrophic conditions of the reservoir, the lower nutrient condition of C/N=2, which can achieve complete removal, was selected for further study.

(3) The oscillation speed reflects the concentration of DO (dissolved oxygen), and the change of DO concentration is crucial to aerobic denitrifying bacteria. Under the conditions of iron dosage of 10 g/L, temperature of 30°C, and C/N=2, the effect of different rotation speeds on N8 nitrogen reduction was investigated.

As shown in Figure 4, when the shaking speed is 40rpm, the nitrate removal rate of strain N8 drops to 85%, which is due to the lack of DO available to aerobic denitrification strains, which is not conducive to denitrification; at the same time, insufficient DO may lead to a decrease in the oxidation rate of iron and a decrease in the supply of electron donors, which will also lead to a decrease in the denitrification rate. In addition, there is a certain amount of ammonia nitrogen accumulation in the later stage of cultivation, reaching a maximum of 0.45mg/L, which may be caused by the autolysis of cell death of the strain. With the continuous increase in the shaking speed, the denitrification rate of strain N8 continues to rise, from 100% nitrate removal rate on the 14th day to 100% on the 10th day; in the end, there is no accumulation of ammonia nitrogen, which may be due to the increase in DO concentration can accelerate the mass transfer rate of oxygen and nitrate, and the oxidation rate of iron will also be accelerated to a certain extent, thereby increasing the activity of nitrogen metabolic enzymes; in addition, no accumulation of nitrite nitrogen was observed during the entire experiment. Therefore, the optimal rotation speed of strain N8 is 160rpm.

(4) The effects of different temperatures (5, 10, 15 and 20°C) on nitrogen reduction of N8 were investigated under the conditions of iron dosage of 10 g/L, C/N=2 and rpm=120.

As shown in Figure 5, as the temperature gradually decreased, the removal rate of TN by strain N8 decreased from 93.36% to 75.34%, 50.80% and 29.18%, and ammonia nitrogen re-accumulated in the late stage of cultivation under low temperature conditions. The reason may be that the cells died after entering the decay period, resulting in the release of ammonia nitrogen, which also shows that the cell activity of the strain is low under low temperature. When the iron dosage was investigated, when the iron dosage was 10g/L, C/N=2, the speed was 120rpm, and the temperature was 30℃, the TN removal rate was 100%. Considering the overall water level and nitrogen removal after the reservoir was mixed, 30℃ with higher removal efficiency was selected as the optimal temperature.

Example 3

This example provides a kinetic model for studying the effects of C/N, rpm (DO) and temperature on denitrification using the aerobic denitrifying fungi of Example 1.

According to the actual seasonal changes of the reservoir in spring, summer, autumn and winter and the thermal stratification phenomenon of the reservoir, changes in three different parameters were set, including C/N, rpm and temperature. In order to specifically analyze the impact of different conditions on the denitrification performance, this study fitted the continuously measured data to different models.

Where C is the nitrate concentration (mg/L) corresponding to the reaction time (T, h). _{K 0V} , R (mg/L), K _1/2V , R (mg ^{1 /2} (L ^1/2 h) ^-1 ) and K _1V , R (h ^-1 ) are the reaction rate constants of the zero-order, half-order and first-order kinetic models. The zero-order kinetic model is often used to indicate that the reaction rate is not limited by the pollutant concentration; the half-order kinetic model is often used to indicate that environmental factors are the limiting step in pollutant removal; the first-order kinetic model is often used to indicate that environmental factors are the limiting step in pollutant removal, and nitrate concentration will become the limiting factor of the reaction rate.

As shown in Figures 6 and 9, with the continuous increase of C/N ratio, the R 2 of the half-order model (R ² =0.8445 when C/N ratio = 1.0, R ² =0.9593 when C/N ratio = 2.0) and the first-order model (R ² =0.7733 when C/N ratio = 1.0, R ² =0.9449 when C/N ratio = 2.0) gradually increased, ^and the corresponding maximum coefficients when the C/N ratio was 2.0 were 0.1326 mg ^1/2 (L ^1/2 h) ^-1 and 0.1650 h ^-1 , respectively. This shows that with the increase of C/N, the denitrification rate continues to accelerate.

As shown in Figures 6 and 9, strain N8 is more consistent with the half-order kinetic model under the change of rpm, and with the continuous increase of rpm, the R ² of the half-order model (R ² =0.9418 when rpm=40, R ² =0.9712 when rpm=160) gradually increases, and the maximum coefficient corresponding to rpm ratio is 0.1628 mg ^1/2 (L ^1/2 h) ^-1 when rpm is 160. This shows that with the increase of rpm, the denitrification rate continues to accelerate. In the first-order kinetic model, when rpm increases to 160, R ² decreases from 0.9449 to 0.9213, and the denitrification rate decreases to a certain extent, indicating that excessive dissolved oxygen will hinder the mass transfer rate and thus reduce the denitrification rate.

As shown in Figures 6 and 9, strain N8 is more consistent with the half-order kinetic model under temperature changes, and as the temperature continues to rise, the R ² of the half-order model (R ² =0.8646 when T=5, R ² =0.9565 when T=20) gradually increases, and the corresponding maximum coefficient is 0.0836 mg ^1/2 (L ^1/2 h) ^-1 when T is 20℃. This shows that as T increases, the denitrification rate continues to accelerate.

In addition, the denitrification rate under the changes of C/N, rpm and temperature is more consistent with the half-order rate equation, indicating that the reaction rate is affected by the external environmental conditions. In addition, changes in the external environment may also affect the release of iron ions and thus affect the denitrification rate. Therefore, under natural conditions, changes in these environmental conditions will jointly affect the nitrate removal of strain N8, rather than a single effect.

Example 4

In this embodiment, the denitrification ability of N8 and the cell growth were tested, as shown in FIG7 .

In the absence of electron donor addition, the adaptation period was from 0 to 1 day, and the cell number decreased slightly from 1.54×10 ⁶ to 1.07×10 ⁶ . At the same time, the nitrate nitrogen removal rate was also slow, from 5 mg/L to 4.71 mg/L. In the logarithmic period of cell growth (2-5d), the nitrate concentration of strain N8 decreased from 4.51 mg/L to 2.91 mg/L, and the nitrate removal rate reached a maximum of 64.6% on the 8th day and then fluctuated. In the case of electron donor addition, the adaptation period was 0-2 days, and the number of cells decreased slightly, from 1.54×10 ⁶ to 9.45×10 ^5. The adaptation time was slightly longer than that without inorganic electron donors, which may be due to the selection of iron. At the same time, the nitrate removal rate was also slow, from 5 mg/L to 4.51 mg/L. In the logarithmic period of cell growth (3-6 days), the nitrate concentration of strain N8 decreased from 4.51 mg/L to 1.82 mg/L, and the nitrate removal rate reached 100% on the 11th day. At the same time, with the continuous removal of nitrate, the content of DOC also gradually decreased. This phenomenon may be due to the fact that the cells consume DOC for self-reproduction and provide the necessary electron donors for denitrification.

As shown in Figure 8, the concentration of Fe ³⁺ and Fe ²⁺ showed a trend of increasing first and then decreasing. The concentration of Fe ³⁺ varied widely. On the 4th day, the highest content of Fe ³⁺ reached 1.483 mg/L, and then rapidly dropped to about 0.5 mg/L, indicating that the oxidation rate of iron gradually slowed down. The iron oxides generated on the surface blocked the subsequent oxidation of iron, but it was still proceeding slowly, resulting in content fluctuations. The content of divalent iron was low, reaching a peak of 0.12 mg/L on the second day, and then fluctuated in the range of 0.067-0.042 mg/L. The reason may be that the aerobic conditions caused the conversion of divalent iron to trivalent iron at a faster rate and a lower concentration.

It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (10)

1. A mixed-trophic denitrifying bacterium Penicillium sp. N8, the preservation unit is the China Type Culture Collection, the preservation address is Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, the preservation number is CCTCC M 20232691, and the preservation date is December 27, 2023. 2. An application of the mixed nutritional denitrifying bacteria Penicillium sp. N8 according to claim 1 in the remediation of nitrogen-containing water bodies. 3. The use according to claim 2 is characterized in that the remediation of nitrogen-containing water bodies is to remove nitrogen from the water bodies. 4. The use according to claim 3, characterized in that nitrogen-containing water body remediation is carried out in the presence of an electron donor. 5. The use according to claim 4, characterized in that, when repairing nitrogen-containing water bodies, the usage amount of the mixed nutritional denitrifying bacteria Penicillium sp. N8 is 1%-5% based on the mass fraction of the nitrogen-containing water body. 6. The use according to claim 4, characterized in that the carbon-nitrogen ratio in the nitrogen-containing water is 1-2.5. 7. The use according to claim 4, characterized in that the temperature of the nitrogen-containing water is 25-30°C. 8. The use according to claim 4, characterized in that the rotation speed of the nitrogen-containing water is 80-160 rpm. 9. The use according to claim 4, characterized in that the electron donor is iron, and the dosage of the iron is 10-15 g/L. 10. A method for treating nitrate in polluted water, characterized in that the mixed nutritional denitrifying bacteria Penicillium sp. N8 according to claim 1 is inoculated into nitrogen-containing water, and iron is added as an electron donor.