Candida tropicalis AX1 and application thereof

Abstract

The invention discloses Candida tropicalis AX1 and application thereof, the preservation number of the Candida tropicalis AX1 is CCTCC (China Center for Type Culture Collection) NO: M20251761, and the Candida tropicalis AX1 is preserved in China Center for Type Culture Collection on August 4, 2025. The strain is separated from southern humid and hot soil, shows good environmental adaptability, can grow in a temperature range of 24-36 DEG C, has an optimal temperature of 30 DEG C, has an atrazine degradation rate of 20.78% at a high temperature of 36 DEG C, and is suitable for soil remediation application in southern high-temperature and high-humidity areas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microbial technology, and particularly relates to a Candida tropicalis AX1 and application thereof. BACKGROUND

[0002] Atrazine, a triazine herbicide, with chemical name of 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine, molecular formula of C8H 14 ClN5, is widely used in the control of annual grass weeds and broadleaf weeds in crops such as sugarcane, sorghum, corn, and carrots. Since its introduction in the 1950s, due to its high efficiency and broad spectrum, it has played an important role in global agricultural production, especially in developing countries and North America. According to relevant reports, the annual use of atrazine reaches tens of thousands of tons worldwide, mainly through foliar spraying or soil treatment to inhibit weed growth and increase crop yield.

[0003] However, atrazine and its metabolites have a long half-life and strong mobility in soil, and their residues have been widely detected in soil, surface water, and groundwater. For example, Fareed et al. (2021) reported that the residual concentration of atrazine in soil was 1.64-16.87 μg·kg -1 , and in groundwater, it was 0.61-1.53 μg·L -1 ; Abuzeid et al. (2022) detected atrazine residues in 26 surface water sampling sites, ranging from 3.13 to 109.18 μg·L -1 . In addition, studies have shown that the half-life of atrazine in soil can be up to 4-57 weeks, and in water, it is 30-100 days, leading to its persistence in the environment. Related investigations have shown that atrazine has been identified in at least 20 National Priorities List (NPL) hazardous waste sites in the United States, and its pollution can spread to the surrounding ecosystems through runoff, infiltration, etc. The European Union has set the maximum allowable concentration of atrazine in drinking water at 0.1 μg·L -1 as a preventive threshold. The U.S. Environmental Protection Agency (EPA) has also established a corresponding concentration equivalent level of concern (CE-LOC) to assess its potential adverse effects on aquatic plants. These residues not only affect soil fertility and water quality, but also can accumulate through the food chain, threatening ecological balance.

[0004] Previous studies have shown that long-term exposure to atrazine at low doses can interfere with the endocrine system of organisms, and atrazine has been listed as an endocrine disruptor. Specifically, it can affect hormone regulation, leading to abnormal reproductive development, and trigger effects such as gender reversal in aquatic organisms. Numerous toxicology studies have confirmed that the degradation products of atrazine are also toxic and difficult to biodegrade, further exacerbating environmental risks.

[0005] To address the problem of atrazine pollution, bioremediation technology has attracted attention due to its low cost, high efficiency, and no secondary pollution. This technology mainly relies on the metabolic action of microorganisms to degrade atrazine into harmless substances such as carbon dioxide, ammonia, water, and biomass. Currently, a variety of microbial strains that can degrade atrazine have been isolated from the environment, including Arthrobacter, Rhodococcus, Pseudomonas, Bacillus, and Citricoccus. These strains are mostly bacteria, which usually achieve degradation through enzymatic reactions such as hydrolysis and dechlorination. However, there are fewer reports on fungi that can degrade atrazine.

[0006] In addition, there are significant climate differences between northern and southern China, leading to large differences in soil physical and chemical properties, such as alkaline and dry soils in the north, and acidic and humid soils in the south. Most existing strains are isolated from farmland soils in the north, and their degradation efficiency and adaptability in southern soils are not yet clear. Environmental factors such as pH, temperature, soil nutrients, and organic matter content can all affect the degradation process, so it is necessary to develop adaptive strains for regional differences to improve the practical application of bioremediation. SUMMARY

[0007] The present application aims to overcome the shortcomings of the prior art and provide a Candida tropicalis AX1.

[0008] Another object of the present application is to provide a preparation method of the above-mentioned Candida tropicalis AX1.

[0009] The technical solution of the present application is as follows:

[0010] A Candida tropicalis AX1, with the accession number CCTCC NO: M20251761, was deposited at the China Center for Type Culture Collection (Wuhan, China, Wuhan University; postcode 430072) on August 4, 2025.

[0011] Use of the above-mentioned Candida tropicalis AX1 in degrading atrazine in soil.

[0012] In a preferred embodiment of the present application, the temperature is 30 DEG C and the pH is 6-8 in degrading atrazine in soil.

[0013] Further preferably, glucose is added as a carbon source in degrading atrazine in soil.

[0014] A composition for degrading atrazine in soil, which effective component comprises the above-mentioned Candida tropicalis AX1.

[0015] A method for degrading atrazine in soil, which uses the above-mentioned Candida tropicalis AX1.

[0016] In a preferred embodiment of the present application, the temperature is 30 DEG C and the pH is 6-8.

[0017] Further preferably, glucose is added as a carbon source.

[0018] Use of the above-mentioned Candida tropicalis AX1 in preparing an animal feed composition.

[0019] An animal feed composition, which effective component comprises the above-mentioned Candida tropicalis AX1.

[0020] The present application has the following advantages:

[0021] 1. The present application is isolated from the hot and humid soil in the south, and shows good environmental adaptability, and can grow in the temperature range of 24-36 DEG C, and the optimum temperature is 30 DEG C, and the degradation rate of atrazine is still 20.78% under the high temperature of 36 DEG C, which is suitable for soil remediation application in the high temperature and high humidity area in the south.

[0022] 2. The present application has strong acid and alkali resistance, and the optimum pH range is 6-8, and although the growth is slow under the condition of strong acid (pH=4) or strong alkali (pH=10), the degradation rate is still more than 10%, which is better than the performance of many bacterial strains isolated in the north in the soil in the south.

[0023] 3. The present application has good tolerance to atrazine concentration, and still has growth (OD 600 =0.24) and about 20% degradation rate under the high concentration of 140 mg·L⁻¹, and the 72 h degradation rate is as high as 49.67% under the low concentration (20 mg·L -1 ), and the 72 h degradation rate is as high as 49.67% under the low concentration (20 mg·L -1The degradation rate is 42.26%, which shows high efficient degradation potential.

[0024] 4、The application can grow with atrazine as the only carbon source under the condition of no external carbon source, but the efficiency can be further improved by adding simple carbon source (such as glucose).

[0025] 5、The growth curve of the application is synchronous with the degradation curve, and the degradation rate is more than 40% within 96 h, statistical analysis shows that the difference is significant (P<0.05), which confirms that it has good stability and reliability.

[0026] 6、The application enriches the fungal resource library of atrazine degradation, and fills the blank of southern environmental fungal research. The protein content of the strain reaches 55%, which can be directly used as animal feed nutrition source, and the biological safety level is I level, without pathogenic risk, so as to realize the win-win of environmental protection and economic benefit. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure shows the colony characteristics (a) and gram staining morphology (b) of the strain AX1 in the embodiment 1 of the application (100x magnification).

[0028] Figure 2 The figure is a phylogenetic tree of the strain AX1 in the embodiment 1 of the application based on ITS sequence.

[0029] Figure 3 The figure is the growth curve (a) and atrazine degradation curve (b) of the strain AX1 in the embodiment 1 of the application.

[0030] Figure 4 The figure is the influence of temperature on the growth (a) and atrazine degradation (b) of the strain AX1 in the embodiment 1 of the application, and the different letters represent that the atrazine degradation rate is significantly different (P<0.05).

[0031] Figure 5 The figure is the influence of pH on the growth (a) and atrazine degradation (b) of the strain AX1, and the different letters represent that the atrazine degradation rate is significantly different (P<0.05).

[0032] Figure 6 The figure is the influence of the inoculum size of the bacterial liquid on the growth (a) and atrazine degradation (b) of the strain AX1 in the embodiment 1 of the application, and the different letters represent that the atrazine degradation rate is significantly different (P<0.05).

[0033] Figure 7 The figure is the influence of the atrazine concentration on the growth (a) and atrazine degradation (b) of the strain AX1 in the embodiment 1 of the application, and the different letters represent that the atrazine degradation rate is significantly different (P<0.05).

[0034] Figure 8 Effects of additional carbon sources on the growth (a) and atrazine degradation (b) of strain AX1 in Example 1 of the present application, different letters represent significant differences (P<0.05) in atrazine degradation rate. DETAILED DESCRIPTION

[0035] The technical solutions of the present application are further described and explained below by specific embodiments in conjunction with the accompanying drawings.

[0036] Example 1

[0037] 1. Materials and methods

[0038] 1.1 Test materials

[0039] 1.1.1 Test soil: soil samples were collected from the vegetable planting area of Xiamen City, Fujian Province (24°45'3" N, 118°5'2" E), dried naturally, ground through a 2 mm sieve and used. The basic physicochemical properties of the soil were pH 6.5, organic matter content 38.05 g·kg -1 , total nitrogen content 1.54 g·kg -1 , available phosphorus content 18.20 mg·kg -1 , available potassium content 135.74 mg·kg -1 .

[0040] 1.1.2 Main reagents and instruments: atrazine solution standard in methanol (100 μg·mL -1 ) purchased from the National Standard Material Center. Atrazine (purity 98%) purchased from Shanghai Yuan Ye Biological Technology Co., Ltd. UV spectrophotometer, Shanghai Midea Instrument Co., Ltd.; high performance liquid chromatograph, Waters Company.

[0041] 1.1.3 Culture medium Minimal Salt Medium (MSM): glucose (10.00 g), K2HPO4 (1.79 g), KH2PO4 (0.45 g), MgSO4 (0.10 g), NaCl (0.40 g), 1 mL trace element stock solution, distilled water to 1000 mL. Trace element stock solution was prepared according to the literature (Yang LJ, Shi DZ, Peng W, et al. Isolation and identification of atrazine-degrading bacteria ATR3 and soil remediation. Journal of Microbiology [J]. 2021, 41 (5): 37-42.). The amount of agar powder added in the solid culture medium was 15 g·L -1 . PDA medium: 40 g of potato dextrose agar powder, dissolved in distilled water and made up to 1000 mL. After the above medium was prepared, it was autoclaved at 121°C for 30 min and ready for use.

[0042] 1.2 Method

[0043] 1.2.1 Isolation and purification of degrading bacteria: 10.0 g of soil sample was added to 100 mg·L -1 MSM containing 100 mg·L -1 of atrazine, and incubated at 30 ℃, 180 r·min -1 for 7 days. The concentration of atrazine was increased by 100 mg·L -1 in each cycle, and the incubation was terminated after the concentration of atrazine reached 700 mg·L –8 . The last cycle of culture was diluted to 10 -1 concentration gradient, and spread on MSM solid plates containing 200 mg·L -1 of atrazine. The strains that formed atrazine hydrolysis rings were further purified, and a single colony strain was finally obtained, numbered AX1, which was stored in a refrigerator at 4 ℃.

[0044] 1.2.2 Morphological observation of the strain and construction of phylogenetic tree: The purified strain was transferred to a PDA solid plate and incubated at 30 ℃ for 2-3 days. The strain was observed for its appearance and morphology, and was identified based on the Fungus Identification Manual and Chinese Fungus Records. Meanwhile, the purified bacterial liquid was stored in a centrifuge tube and sent to Beijing Qikexin Biological Technology Co., Ltd. for sequencing using the universal fungal primers ITS1 (5'-tccgtaggtgaacctgcgg-3', SEQ ID NO. 01) and ITS4 (5'-tcctccgcttattgatatgc-3', SEQ ID NO. 02). The sequencing results were subjected to BLAST homology comparison on the NCBI website, and strains with similar homology were selected to construct a phylogenetic tree using the MEGA X neighbor method.

[0045] 1.2.3 Preparation of bacterial suspension: The strain AX1 was inoculated into MSM and incubated at 30 ℃, 180 r·min -1 for 24 h. Then, the bacterial concentration was adjusted with sterile water, and the OD 600 value was detected by a spectrophotometer to be about 1.0, which was used for subsequent experiments.

[0046] 1.2.4 Determination of growth curve of strain AX1 and its degradation curve of atrazine

[0047] 2 mL of the above bacterial liquid was inoculated into MSM containing 100 mg·L -1 of atrazine and incubated at 30 ℃, 180 r·min -1 . The OD 600The growth curve of the strain on the medium containing atrazine was plotted, and the content of atrazine in the culture solution was determined by high performance liquid chromatography to plot the degradation curve of the strain on atrazine.

[0048] The liquid phase conditions for atrazine detection were as follows: 250 mm×4.6 mm C 18 18-BDS HPLC column, the mobile phase was methanol: water = 80:20 (V / V), the flow rate was 0.8 mL·min -1 , the column temperature was 40 ℃, the injection volume was 10 μL, and the variable wavelength ultraviolet detector was used with a detection wavelength of 225 nm.

[0049] According to the HPLC determination results, the degradation rate of atrazine was calculated:

[0050] ;

[0051] In the formula, C t is the final concentration of atrazine, mg·L -1 ; C0 is the initial concentration of atrazine, mg·L -1 .

[0052] 1.2.5 Influence of environmental conditions on the growth and degradation of atrazine by strain AX1

[0053] The influence of environmental conditions on the growth and degradation of atrazine by strain AX1 was studied by changing the temperature, pH, inoculum size, atrazine concentration, and type of carbon source.

[0054] (1) Temperature

[0055] MSM containing 100 mg·L -1 of atrazine was prepared, 2 mL of inoculum was added, the temperature was set to 24, 27, 30, 33, and 36 ℃, the pH was 7.0, and the culture was performed on a 180 r·min -1 shaker, the control group was the medium without the addition of bacterial liquid, each treatment was set in triplicate, and the OD 600 value and the residual amount of atrazine were determined at 48 h and 72 h after culture.

[0056] (2) pH

[0057] MSM containing 100 mg·L -1 of atrazine was prepared, 2 mL of inoculum was added, the pH was set to 4.0, 6.0, 7.0, 8.0, and 10.0, the temperature was 30 ℃, and the culture was performed on a 180 r·min -1 shaker, the control group was the medium without the addition of bacterial liquid, each treatment was set in triplicate, and the OD 600OD value and atrazine residue.

[0058] (3) Inoculum size

[0059] MSM containing 100 mg·L -1 The inoculum size was set as 0.5%, 1%, 2%, 3% and 5%, pH 7.0, 30 ℃, 180 r·min -1 shaking culture. The control group was MSM without adding bacterial liquid. Each treatment was set in triplicate. The OD 600 value and atrazine residue were determined at 48 h and 72 h after culture.

[0060] (4) Initial concentration of atrazine

[0061] MSM was prepared, and the concentration of atrazine was adjusted to 20, 50, 80, 100 and 140 mg·L -1 , 2 mL of inoculum was added, pH 7.0, 30 ℃, 180 r·min -1 shaking culture. The control group was MSM without adding bacterial liquid. Each treatment was set in triplicate. The OD 600 value and atrazine residue were determined at 48 h and 72 h after culture.

[0062] (4) Type of carbon source

[0063] In MSM containing 100 mg·L -1 of atrazine, 1 g / L of glucose, sucrose, soluble starch and trisodium citrate were added respectively, 2 mL of inoculum was added, 30 ℃, 180 r·min -1 shaking culture. The control group was MSM without adding carbon source. Each treatment was set in triplicate. The OD 600 value and atrazine residue were determined at 48 h and 72 h after culture.

[0064] 1.3 Data statistics and analysis

[0065] The significant difference of data was analyzed by SPSS Statistics 26 software (P<0.05), and Origin 9.0 was used for plotting.

[0066] 2. Results and analysis

[0067] 2.1 Isolation and identification of atrazine-degrading bacteria

[0068] A strain numbered AX1 with strong atrazine-degrading ability was isolated and purified from soil by enrichment culture method. The strain AX1 could degrade 200 mg·L -1Atrazine concentrations resulted in a distinct degradation zone on MSM solid plates. The strain was round, with smooth, regular edges, white, and opaque. Figure 1 Gram staining is red. BLAST homology comparison results showed that strain AX1 had a similarity of over 99% with several strains of Candida tropicalis, preliminarily identifying strain AX1 as a Candida fungus. Homologous strains were selected, and a phylogenetic tree of strain AX1 was constructed on MEGA X software using the nearest neighbor method. Figure 2 Strain AX1 clustered with KY 963121.1 Candida tropicalis isolate SY5-3 on the same monophyletic clade, with a support rate as high as 97%, while being significantly distancing from other genera and species. Based on comprehensive sequence homology and phylogenetic analysis, strain AX1 was preliminarily identified as Candida tropicalis. The obtained gene sequence of AX1 was submitted to NCBI GeneBank and obtained the accession number PV916036.

[0069] 2.2 Growth characteristics of strain AX1 and its degradation characteristics of atrazine

[0070] Determination of OD of bacterial culture using ultraviolet spectrophotometer 600 The content of atrazine was determined by high performance liquid chromatography (HPLC), and the growth curves of strain AX1 were obtained. Figure 3 a) and its degradation curve for atrazine ( Figure 3 b). During the first 0-48 hours, strain AX1 grew rapidly; after 48 hours, its growth began to slow down. After 96 hours of culture, the OD of the bacterial culture... 600 The value still shows an upward trend. The degradation rate of atrazine by the strain was low in the early stage of culture (0-12 h), and slightly higher than 10% at 12 h; when the culture time was 12-72 h, the growth OD of strain AX1... 600 The degradation rate of atrazine remained almost constant, but the degradation rate did not reach 40%. After 72 h, the growth of strain AX1 began to slow down, and the degradation rate of atrazine also gradually slowed down. At 96 h, the degradation rate of atrazine exceeded 40%.

[0071] 2.3 Effects of environmental conditions on the growth and atrazine degradation of strain AX1

[0072] 2.3.1 Effect of temperature on the growth and atrazine degradation of strain AX1: During the 0-72 h period, the growth and degradation rate of strain AX1 showed an increasing trend, i.e., the OD of the strain at 72 h was... 600Both the absorbance value and the atrazine degradation rate were higher than 48 h. With increasing temperature, the growth ability of AX1 gradually increased, and the degradation rate of atrazine also gradually increased. At 30℃, strain AX1 exhibited the highest growth, with a degradation rate of 33.68% for atrazine. Above 30℃, the growth of AX1 gradually slowed down. Figure 4 a), the degradation rate of atrazine also decreased accordingly ( Figure 4 b).

[0073] 2.3.2 Effect of pH on the growth and atrazine degradation of strain AX1: From Figure 5 It can be seen that strain AX1 exhibits the best growth ability and degradation effect on atrazine at pH 7, with an OD value of [value missing] after 72 h of culture. 600 At a pH of 0.34, the degradation rate of atrazine was 33.63%, higher than at other pH values. When the pH was strongly acidic (pH=4) and strongly alkaline (pH=10), AX1 grew more slowly, and the degradation rate of atrazine was less than 10%. When the pH was 6-8, AX1 showed better growth trend and degradation ability.

[0074] 2.3.3 Effect of inoculum size on the growth of strain AX1 and degradation of atrazine: With the increase of inoculum size, the degradation rate of atrazine at different time points increased significantly ( Figure 6 Furthermore, the degradation rate at 72 h was higher than that at 48 h. When the inoculum size was 5 mL and the culture time was 72 h, the OD of the bacterial culture was [missing value]. 600 The value was 0.67, and the degradation rate of atrazine was 44.22%. The degradation rate of atrazine by the strain continued to increase with increasing inoculum size.

[0075] 2.3.4 Effect of initial atrazine concentration on the growth and degradation of strain AX1: With increasing atrazine concentration, the OD of the bacterial culture increased. 600 The values ​​showed a trend of first increasing and then decreasing, with concentrations ranging from 20 to 80 mg·L⁻¹. -1 When the range is reached, OD 600 The value gradually increases; the concentration exceeds 80 mg·L⁻¹. -1 At that time, OD 600 The value shows a downward trend ( Figure 7 a). The degradation rate of atrazine by this bacterium decreases with increasing concentration. Figure 7 b). Atrazine concentration was 80 mg·L⁻¹ -1 At a concentration of 20 mg / L, strain AX1 exhibited the highest growth capacity, but its degradation rate of atrazine was only 36.83%; -1 At that time, strain AX1 had the highest degradation ability, with a degradation rate of 49.67%.

[0076] 2.3.5 The effect of different carbon sources on the growth of strain AX1 and the degradation of atrazine: The addition of glucose, sucrose and sodium citrate in MSM can significantly promote the growth of strain AX1 and the degradation of atrazine. Figure 8 When glucose is used as the carbon source, the strain grows in a larger amount and has a higher degradation rate of atrazine, followed by sucrose and sodium citrate. The strain grows slowly in the treatment group with the addition of starch, and there is no significant difference between the treatment group and the control group.

[0077] In this embodiment, strain AX1 is a fungus and is screened from the hot and humid soil environment in southern China, which is of great significance to enrich the strain library of atrazine-degrading bacteria, and the degradation rate of the strain on atrazine is expected to be further improved as the environmental conditions change and domestication. Candida tropicalis is a protein-rich feed yeast, and its protein content reaches 55%. This makes it can be directly used as a nutrient source in animal feed. At the same time, its biosafety laboratory level is I level, and there is no pathogenic risk. Therefore, the use of the present application not only expands the scope of the study of microorganisms degrading atrazine, but also improves the economic feasibility of the process of biodegrading atrazine, achieving a win-win of environmental protection and economic benefits.

[0078] The degradation ability of the strain is related to the environment. The results of this embodiment show that the degradation of atrazine is closely related to the growth of the strain, and the degradation rate and the growth of the strain show obvious synchronism. Strain AX1 can grow at 24-36℃, and 30℃ is the most suitable growth temperature. The degradation rate of atrazine at 36℃ high temperature is still 20.78%, which shows that the strain can tolerate a certain degree of high temperature limitation and has more advantages in the survival of the soil in southern areas. The optimal pH of strain AX1 is 6-8, which shows a certain degree of acid and alkali resistance, that is, the degradation rate of phenol by Candida tropicalis is the highest at pH 6-8.

[0079] With the increase of the initial inoculation amount, the degradation rate of atrazine at different time points is significantly increased ( Figure 6 ), and when the inoculation amount is 5% and the culture time is 72h, the degradation rate of atrazine is 44.22%, which shows that with the increase of the inoculation amount, the degradation rate of the strain on the pollutants is significantly increased. A larger inoculation amount helps the strain to pass the adaptation period more quickly, so that it can more quickly establish and play its role in the new environment, and a too small inoculation amount will lead to slow growth of the strain and low cell activity. In this embodiment, the initial concentration of atrazine is increased from 20 mg·L -1 to 140 mg·L -1 , and the degradation rate of atrazine by strain AX1 within 72h is decreased from 49.67% to 21.14% ( Figure 7b), which indicated that atrazine had a certain toxicity to the growth of strain AX1, and the toxicity inhibition of growth and metabolism of strain AX1 was weakened with the decrease of atrazine concentration, and the degradation rate gradually increased. Strain AX1 could tolerate a higher concentration of atrazine, and still grew when the concentration of atrazine was 140 mg·L -1 -1, and the OD 600 value was 0.24 Figure 7 a), and the degradation rate of atrazine was about 20%.

[0080] Strain AX1 could grow with atrazine as the only carbon source without relying on external carbon source, but the additional carbon source would significantly affect the growth Figure 8 of strain AX1. In this embodiment, glucose, sucrose and sodium citrate could improve the growth amount and atrazine degradation capacity of the strain, and the effect of adding glucose was better, and there was no significant difference between adding starch and the control group, which indicated that the strain could not grow by utilizing starch. That is, AX1 would preferentially utilize the carbon source with simpler structure (glucose).

[0081] The above is only a preferred embodiment of the present application, and therefore cannot limit the scope of the present application, that is, equivalent changes and modifications made according to the scope of the present patent and the content of the specification should still be within the scope covered by the present application.

Claims

1. A Candida tropicalis AX1, characterized in that: The preservation number is CCTCC NO: M20251761, which was preserved in China Center for Type Culture Collection on August 4, 2025.

2. Use of the Candida tropicalis AX1 in claim 1 in degrading atrazine in soil.

3. Use according to claim 2, characterized in that: In the degradation of atrazine in soil, the temperature is 30℃, and the pH is 6-8.

4. Use according to claim 3, characterized in that: In the degradation of atrazine in soil, glucose is added as a carbon source.

5. A composition for the degradation of atrazine in soil, characterized in that: The effective component includes the Candida tropicalis AX1 in claim 1.

6. A method of degrading atrazine in soil, characterized by: The Candida tropicalis AX1 in claim 1 is used.

7. The degradation method of claim 6, wherein: The temperature is 30℃, and the pH is 6-8.

8. The degradation method of claim 7, wherein: Glucose is added as a carbon source.

9. Use of the Candida tropicalis AX1 in claim 1 in preparing an animal feed composition.

10. An animal feed composition, characterized by: The effective component includes the Candida tropicalis AX1 in claim 1.

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