A beneficial Lactobacillus plantarum strain SWUN3927 and its applications

Abstract

This invention relates to the field of probiotic development and utilization technology, specifically to a probiotic strain of *Lactobacillus plantarum* SWUN3927 and its applications. The *Lactobacillus plantarum* (… Lactobacillus plants SWUN3927, isolated from colostrum of Tibetan yaks, was used in this invention to identify the probiotic effects of *Lactobacillus plantarum* SWUN3927 through animal experiments. The results showed that *Lactobacillus plantarum* SWUN3927 is resistant to acid and bile salts and has an inhibitory effect on pathogenic bacteria; its hydrophobicity is 74.67% and its self-aggregation is 58.98%, demonstrating that *Lactobacillus plantarum* SWUN3927 of this invention has good intestinal adhesion and possesses the potential of a probiotic. This invention verifies that *Lactobacillus plantarum* SWUN3927 can effectively regulate animal immunity, improve the body's antioxidant capacity, increase lysozyme content and alkaline phosphatase activity, improve daily weight gain, and ultimately improve animal growth performance.

Description

Technical Field

[0001] This invention relates to the field of probiotic development and utilization technology, specifically to a probiotic strain of Lactobacillus plantarum SWUN3927 and its applications. Background Technology

[0002] Currently, antibiotics are commonly used to alleviate or control bacterial diseases such as Escherichia coli and Salmonella in clinical practice. Therefore, antibiotics remain an important means of treating bacterial infections in animal husbandry. However, repeated, excessive, or abusive use of antibiotics can lead to drug side effects. Furthermore, while antibiotics kill pathogens, they may also adversely affect the gut microbiota, potentially causing irritable bowel syndrome (IBS) and various immune diseases. More importantly, the overuse and abuse of antibiotics can lead to the emergence and spread of antibiotic-resistant strains, posing a serious threat to the livestock industry and, consequently, to human safety and health. Against this backdrop, probiotic preparations offer a new avenue for producing natural, safe, high-quality, green, and healthy animal products. As a novel feed additive, it has advantages in alleviating feed resource shortages, improving nutritional structure, reducing feed costs, and protecting the environment. It can be widely used in poultry, pig, and ruminant farming, and is of great significance to the healthy and sustainable development of my country's livestock industry.

[0003] Lactic acid bacteria are the most common Gram-positive bacteria among probiotics, providing various beneficial functions to the host, mainly including the following four points: 1. By producing antibacterial substances such as organic acids, bacteriocins, and hydrogen peroxide, they competitively bind to the adhesion sites of intestinal mucosal epithelial cells, thereby reducing the content of pathogenic bacteria such as Escherichia coli and Salmonella in the intestine, thus maintaining the balance of the intestinal flora; 2. By stimulating the host's immune system, resisting pathogen infection, and promoting humoral and cellular immunity, they exert an immunomodulatory effect; 3. By eliminating harmful substances in the body, such as free radicals and toxins, they enhance the animal's antioxidant capacity, intervene in fatty acid metabolism, and significantly improve the brightness and tenderness of meat products; 4. They produce various digestive enzymes, such as cellulase and protease, to help the body digest better, promote the absorption of nutrients by the host, and thus promote host growth. Furthermore, feed fermented with lactic acid bacteria contains a large amount of lactic acid bacteria and lactic acid, which can inhibit the growth of putrefactive bacteria and extend the shelf life of the feed. It is also rich in organic acids and various sugars, alcohols, esters, and other flavor compounds, which can improve palatability and increase animal feed intake. Currently, the lactic acid bacteria strains used are mostly *Lactobacillus plantarum*, *Lactobacillus acidophilus*, *Pediococcus lactis*, *Enterococcus faecalis*, and *Enterococcus faecium*. *Lactobacillus plantarum*, as a type of lactic acid bacteria, can not only produce antibacterial substances such as bacteriocins and organic acids, but also extracellular polysaccharides, thus attracting significant attention in the pharmaceutical and food industries.

[0004] Currently, research and application of *Lactobacillus plantarum* derived from yak colostrum in animal probiotics are relatively limited. However, existing studies indicate that *Lactobacillus plantarum* is a probiotic with good probiotic properties and significant research potential. Therefore, screening for a strain of *Lactobacillus plantarum* with good tolerance, self-aggregation, antibacterial, growth-promoting, and immune-boosting properties is of great significance for the healthy and green development of the yak farming industry. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a beneficial Lactobacillus plantarum strain SWUN3927, which has broad-spectrum antibacterial ability, acid and bile salt resistance, and can improve the daily weight gain of animals and has the ability to adhere to the intestinal epithelium.

[0006] To achieve the above objectives, the following technical solution is provided:

[0007] This invention relates to a strain isolated from colostrum of Tibetan yaks and named SWUN3927. 16S rRNA gene sequence analysis confirmed that SWUN3927 is *Lactobacillus plantarum*. This strain was deposited on July 22, 2024, at the China Center for Type Culture Collection (CCTCC), Wuhan, China, and is classified as *Lactobacillus plantarum* SWUN3927, with accession number CCTCC NO: M 20241631.

[0008] The *Lactobacillus plantarum* SWUN3927 is a Gram-positive bacterium.

[0009] The present invention provides a bacterial agent containing the aforementioned Lactobacillus plantarum SWUN3927.

[0010] This invention also provides the application of Lactobacillus plantarum SWUN3927 in the preparation of feed additives or animal feed.

[0011] Preferably, the feed additive or animal feed has broad-spectrum antibacterial properties.

[0012] Preferably, the feed additive or animal feed is a product that promotes animal growth and regulates the animal's immunity.

[0013] Preferably, the feed additive or animal feed is a product that enhances antioxidant capacity.

[0014] This invention demonstrates through animal experiments that the aforementioned *Lactobacillus plantarum* SWUN3927 can improve animal growth performance, enhance the body's antioxidant capacity, and effectively regulate the animal's immunity.

[0015] In this invention, the antibacterial spectrum of the *Lactobacillus plantarum* SWUN3927 is selected from Gram-positive bacteria or Gram-negative bacteria.

[0016] In this invention, the Gram-negative bacteria are pathogenic Escherichia coli and Salmonella enteritidis.

[0017] The present invention also provides a drug containing the aforementioned *Lactobacillus plantarum* SWUN3927.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. This invention uses mice as an animal model to identify the probiotic effects of *Lactobacillus plantarum* SWUN3927 through animal experiments. The results show that *Lactobacillus plantarum* SWUN3927 is resistant to acid and bile salts, and can withstand the gastrointestinal environment; its hydrophobicity is 74.67% and its self-aggregation is 58.98%, proving that *Lactobacillus plantarum* SWUN3927 of this invention has good intestinal adhesion and has the potential to become a probiotic.

[0020] 2. This invention verifies that Lactobacillus plantarum SWUN3927 can effectively regulate animal immunity, improve the body's antioxidant capacity, lysozyme content and alkaline phosphatase activity, increase daily weight gain, and ultimately improve animal growth performance. Attached Figure Description

[0021] Figure 1 A is a streak diagram of Lactobacillus plantarum SWUN3927 on MRS agar medium in this invention;

[0022] Figure 1 B represents the staining and microscopic examination results (10×100μm) of Lactobacillus plantarum SWUN3927 in this invention;

[0023] Figure 2 This refers to the hemolysis results in the embodiments of the present invention; Figure 2 A is a positive control bacterium: Staphylococcus aureus; Figure 2 B is Lactobacillus plantarum SWUN3927;

[0024] Figure 3 The organ index results are shown in the embodiments of the present invention;

[0025] Figure 4 This refers to the daily weight gain results in the embodiments of the present invention;

[0026] Figure 5 The results of SOD, AKP, and LZM in mouse serum in the embodiments of the present invention are shown below; 5A: SOD result; 5B: AKP result; 5C: LZM result; CG represents the control group; LG represents the low-dose group; HG represents the high-dose group.

[0027] Figure 6 6A: IgG content in mouse blood and sIgA content in jejunum in the embodiments of the present invention; 6B: sIgA content in jejunum. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that, unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0030] Statistical analysis: GraphPad Prism 8.0.2 was used for statistical analysis, and the significance level was set as P<0.05 or P<0.01.

[0031] Example 1: Isolation and Identification of Lactobacillus plantarum SWUN3927 from Yak Colostrum

[0032] 1. Isolation of *Lactobacillus plantarum*: Colostrum samples from yaks were collected from a region in Tibet. The collected colostrum samples were serially diluted with PBS and spread onto GYP solid medium, then incubated in a constant-temperature anaerobic incubator at 37℃ for 24 h. Single colonies with calcification zones were picked and purified on MRS agar medium until the colony morphology remained unchanged. *Lactobacillus plantarum* colonies on MRS agar were small, round, and moist, white or milky white. The colony surface was smooth with regular, neat edges. Figure 1 A.

[0033] Place a drop of sterile saline solution on a clean glass slide. Use an inoculation loop to pick up a small amount of bacteria, spread it on the slide, and allow it to dry. Perform Gram staining, examine under a microscope, and observe the colony morphology. Select rod-shaped, Gram-positive strains and number them accordingly. After screening for resistance to artificial gastrointestinal fluid and other tests, strain SWUN3927 was found to have the best biological characteristics. Strain SWUN3927 is a Gram-positive bacterium, typically appearing under a microscope as rod-shaped, single, paired, or chain-like arrangements. Figure 1 As shown in B.

[0034] 2. PCR identification

[0035] DNA extraction: DNA of the bacterial strain with antibacterial activity was extracted by phenol-chloroform method, and the DNA concentration and purity were detected by an ultra-micro nucleic acid protein analyzer.

[0036] Using bacterial DNA as a template, universal primers for 16S rRNA were selected.

[0037] 27F(5´-AGAGTTTGATCCTGGCTCAG-3´),1492R(5´-GGTTACCTTGTTACGACT T-3´), primers were synthesized by Sangon Biotech (Shanghai) Co., Ltd., and PCR amplification was performed on the synthesized primers.

[0038] The PCR amplification system was as follows: 2 µL DNA template, 10 µL 2T5 Super PCR Mix, 1 µL 27F, 1 µL 1492R, and double-distilled water (dd H2O) to make up to 20 µL. The PCR amplification conditions were: 95℃ pre-denaturation for 30 min; 94℃ denaturation for 30 s; 50.8℃ annealing for 30 s; 72℃ extension for 90 s, 35 cycles; and 72℃ final extension for 5 min.

[0039] Agarose gel electrophoresis: PCR amplification products were detected by electrophoresis using a 2% agarose gel with 1×TAE buffer as the electrophoresis medium. Electrophoresis conditions: voltage 120 V, current 200 mA, time 26 min. PCR product sequencing was performed by Sangon Biotech Co., Ltd. Sequencing results were assembled and submitted to the GenBank database of the National Center for Biotechnology Information (NCBI) for comparison using the basic local alignment search tool (BLAST) to determine the species.

[0040] Strain preservation information:

[0041] Lactobacillus plantarum SWUN3927 was deposited at the China Center for Type Culture Collection (CCTCC), Wuhan, Hubei Province, China, with accession number CCTCC NO: M 20241631, classified as Lactobacillus plantarum SWUN3927, and deposited on July 22, 2024.

[0042] Example 2: Determination of the antibacterial activity of the supernatant of *Lactobacillus plantarum* SWUN3927 derived from yak colostrum.

[0043] The bacterial culture was inoculated into MRS liquid medium at the specified ratio and cultured at 37°C for 24 h to prepare a seed culture. The culture was then centrifuged at 10,000 rpm at 4°C for 15 min to obtain the fermentation supernatant. After removing the bacterial cells and other impurities from the supernatant using a 0.22 µm disposable sterile filter, the supernatant was stored at -20°C for later use.

[0044] The antibacterial activity of the fermentation supernatant was determined using the Oxford cup method. *Escherichia coli* ATCC25922 and *Salmonella* ATCC14028 were selected as quality control strains. LB nutrient agar was used for testing, and the indicator bacteria were analyzed using an ultraviolet spectrophotometer with an OD value of [missing information]. 600 The turbidity of the bacterial suspension was adjusted to 0.5 nm to serve as the indicator bacterial suspension turbidity. 0.2 mL of the bacterial suspension was added to LB medium and evenly spread on the surface using a disposable spreader. Oxford cups were placed in the center of the petri dishes, and approximately 0.2 mL of fermentation supernatant was slowly added to each cup. A control was also included. The dishes were then refrigerated at 4°C for 8 hours to allow the supernatant to diffuse. Afterward, they were incubated at 37°C for 12 hours, and the inhibition zones were observed and recorded (results are shown in Table 1).

[0045] Table 1 Antibacterial effect

[0046] ;

[0047] Note: "-" indicates that the inhibition zone is less than 8 mm and has no antibacterial activity; "+" indicates that the diameter of the inhibition zone is 8-11 mm; "++" indicates that the diameter of the inhibition zone is 12-17 mm; "+++" indicates that the diameter of the inhibition zone is 18-23 mm.

[0048] Table 1 shows that *Lactobacillus plantarum* SWUN3927 has a good inhibitory effect on *Staphylococcus aureus* 4509, *Salmonella enteritidis* reference strain, *Escherichia coli* 4566, *Escherichia coli* 6794, *Salmonella enteritidis* 3807, and *Escherichia coli* 4135.

[0049] Example 3: Biological characteristics of *Lactobacillus plantarum* SWUN3927 derived from yak colostrum

[0050] 1. Growth curve of Lactobacillus plantarum SWUN3927

[0051] Lactobacillus plantarum SWUN3927 was inoculated into 50 mL of MRS broth at a ratio of 2% and incubated at 37°C. Starting from 0 h, 3 mL of bacterial culture was taken every 2 hours to measure the OD of the strain. 600 nm values ​​were recorded, and three parallel controls were performed, with blank MRS medium used as a control. The results showed that *Lactobacillus plantarum* SWUN3927 followed a lag phase, logarithmic growth phase, stationary phase, and death phase. The strain was in the lag phase for the first 2 hours, in the logarithmic growth phase from 2 to 10 hours, and entered the plateau phase after 10 hours. After entering the stationary and death phases, the viable bacteria were inhibited by their own metabolic products, indicating that the optimal harvest time for this strain was 10 hours.

[0052] 2. Test on the resistance of *Lactobacillus plantarum* SWUN3927 derived from yak colostrum to gastrointestinal fluid.

[0053] Preparation of gastrointestinal fluid: Gastric fluid was prepared by adding 0.35 g pepsin to 100 mL of 0.2% sterile physiological saline. The pH of the solution was adjusted to 2.5 with 1 mol / L HCl and stored after passing through a 0.22 μm filter. Intestinal fluid was prepared by adding 0.1 g trypsin and 1.8 g ox bile salts to 100 mL of distilled water containing 1.1 g NaHCO3 and 0.2 g NaCl. The pH of the solution was adjusted to 8.0 with 1 mol / L NaOH and stored after passing through a 0.22 μm filter. The bacterial culture (10... 8 ~10 9 CFU / mL) was inoculated into simulated gastric fluid at 10% of the inoculum size. Plate counts were performed at 0 h and 3 h (4 h for intestinal fluid) to determine the number of viable bacteria. The survival rate (%) of the strain was calculated using the following formula:

[0054] Survival rate (%) = C1 / C2 × 100%;

[0055] In the formula: C1 is the number of viable bacteria (CFU / mL) measured after treatment of gastrointestinal fluid; C2 is the number of viable bacteria (CFU / mL) measured in gastrointestinal fluid at 0 h.

[0056] The results showed that the survival rate of *Lactobacillus plantarum* SWUN3927 in gastric fluid was 84.48% after 3 hours, and the survival rate in intestinal fluid was 71.87% after 4 hours. *Lactobacillus plantarum* SWUN3927 exhibits good acid and bile salt tolerance, and has the potential to become a probiotic.

[0057] 3. Determination of self-aggregation and hydrophobicity of *Lactobacillus plantarum* SWUN3927 derived from yak colostrum

[0058] (1) Self-aggregation: Seed culture was inoculated at 2% in sterilized liquid MRS medium and cultured at 37 ℃ for 24 h. The culture was centrifuged at 4 ℃ and 10000 r / min for 10 min, the supernatant was discarded, and the culture was washed twice with phosphate buffer (pH 7.2). The culture was then resuspended in PBS, and the bacterial suspension concentration was adjusted to 10. 7 ~10 8 For each CFU / mL bacterial suspension, 3 mL of the bacterial suspension was measured at 600 nm and recorded as A0. After standing at 37 °C for 5 h, 3 mL of the supernatant was transferred to another test tube, and the absorbance was measured at 600 nm and recorded as At. The experiment was repeated three times independently, and the average value was taken.

[0059] ;

[0060] At represents the OD at t = 5 h. 600 The value of A0 is OD at t = 0 h. 600The value of .

[0061] (2) Hydrophobicity: Prepare a bacterial suspension as described in (1), then add an equal volume of xylene. Vortex the two-phase system for 3 min, let it stand at 37 ℃ for 1 h, and then take out the supernatant. Measure the absorbance of the aqueous phase at a wavelength of 600 nm and record it as A. Calculate the surface hydrophobicity of the strain according to the formula. Repeat the experiment 3 times independently and take the average value.

[0062] ;

[0063] In the formula: A0 and A represent the absorbance of the Lactobacillus plantarum SWUN3927 bacterial suspension and the aqueous phase after mixing the two phases, respectively.

[0064] Lactobacillus plantarum SWUN3927 needs to possess the ability to colonize the host intestine and prevent pathogens from colonizing it. Self-aggregation ability is an important indicator for assessing its ability to adhere to intestinal cells in vitro. Self-aggregation ability is generally classified into three categories: weak (16%–35%), moderate (35%–50%), and strong (above 50%). In this invention, the self-aggregation and hydrophobicity of Lactobacillus plantarum SWUN3927 were measured to be 58.98% and 74.67%, respectively, indicating that this bacterium has good intestinal adhesion.

[0065] 4. Determination of the in vitro antioxidant capacity of *Lactobacillus plantarum* SWUN3927 derived from yak colostrum

[0066] Determination of total antioxidant capacity (T-AOC) and superoxide dismutase (T-SOD) of Lactobacillus plantarum SWUN3927: The T-AOC and T-SOD activities of Lactobacillus plantarum SWUN3927 supernatant were determined using a kit, and the specific methods were strictly performed in accordance with the kit instructions.

[0067] The results showed that the total antioxidant capacity (T-AOC) was 1.230 U / mL, and the superoxide dismutase (T-SOD) was 116.976 U / mL. This indicates that *Lactobacillus plantarum* SWUN3927 possesses certain antioxidant properties and can enhance the antioxidant capacity of animals.

[0068] Example 4: Safety of *Lactobacillus plantarum* strain SWUN3927 derived from yak colostrum

[0069] (1) Hemolytic activity test of Lactobacillus plantarum SWUN3927: Centrifuged Lactobacillus plantarum SWUN3927 was streaked onto blood agar plates and incubated at 37 °C for 48 h. Hemolysis was observed. Strains that produced a green band around the colony (α-hemolysis) or did not produce any hemolysis on the blood agar plate (γ-hemolysis) were considered non-hemolytic. Strains that showed a hemolytic band (clear band) around the colony were classified as microorganisms with hemolytic (β-hemolytic) characteristics. The appearance of a clear β-hemolytic ring indicated a positive hemolytic phenotype. Hemolytic Staphylococcus aureus was used as a positive control strain.

[0070] The results showed that Lactobacillus plantarum SWUN3927 had a negative hemolysis result, indicating high safety. (See details...) Figure 2 Among them, 2A is Staphylococcus aureus and 2B is Lactobacillus plantarum SWUN3927.

[0071] (2) Antibiotic susceptibility test of Lactobacillus plantarum SWUN3927: The KB disk method was used to detect the susceptibility of the selected strain to common antibiotics. 200 μL of seed culture was inoculated into 8 mL of MRS broth and cultured at 37℃ for 24 h. The bacterial concentration was then adjusted to reach 10. 8 CFU / mL, use a disposable sterile cotton swab to apply bacterial suspension evenly to MH medium. Use sterile forceps to remove the drug sensitivity strips and place them sequentially on the surface of the medium. Gently press the strips with the forceps to ensure tight adhesion. Place four strips on each plate. Incubate at 37 ℃ for 16 h, measure the diameter of the inhibition zone with a ruler, and record the results.

[0072] Table 2 Drug sensitivity results

[0073] ;

[0074] “S” sensitive, “R” resistant, “I” intermediate

[0075] According to the Clinical and Laboratory Standards Institute (CLSI) testing standards, antibiotic resistance was evaluated using the Kirby-Bauer disk diffusion method. The results of the drug susceptibility test were categorized into three levels: Resistant, Intermediate, and Susceptible. As shown in Table 2, *Lactobacillus plantarum* SWUN3927 was sensitive to the vast majority of antibiotics, exhibiting no resistance and demonstrating high safety.

[0076] (2) Oral test for acute toxicity in mice

[0077] Twelve male SPF-grade KM mice were selected, with six mice in the experimental group and six in the control group. After one week of acclimatization, the experiment was conducted. The experimental group was administered Lactobacillus plantarum SWUN3927 1×10⁻⁶ daily by gavage. 10 Mice were administered the same volume of MRS broth via gavage for 21 consecutive days, with the control group receiving a bacterial culture at CFU / mL. During this period, the mice's mental state, appetite, and fecal condition were observed. After 21 days, the mice were dissected, and their hearts, lungs, livers, spleens, and kidneys were removed to observe for any obvious pathological changes and to measure organ activity indices.

[0078] The results showed that the mice maintained good mental and physical condition and did not experience diarrhea or death during the gavage treatment. Autopsy revealed no significant differences or pathological changes in the heart, liver, spleen, lungs, and weight of the control group mice compared to the experimental group. Measurements of organ weight showed no significant difference in organ indices between the experimental and control groups (P>0.05). See details below. Figure 3 Safety test results indicate that Lactobacillus plantarum SWUN3927 does not pose a high risk as an animal feed additive.

[0079] Example 5: Effects of yak colostrum-derived fused Weissl bacterium DY12 on growth performance, antioxidant capacity, and immunity in mice.

[0080] Lactobacillus plantarum SWUN3927 was streaked onto plates and incubated at 37°C for 24 h. Single colonies were picked and cultured in MRS liquid medium for 24 h. After washing twice with PBS and resuspending, the culture was serially diluted, and the final concentration was determined to be 1×10⁻⁶ after plate counting. 8 CFU / mL and 1×10 10 The concentration of CFU / mL was aliquoted into 10mL centrifuge tubes and stored at -20°C.

[0081] Four-week-old male SPF-grade KM mice, weighing 20±2 g, were selected. Thirty mice were randomly divided into three groups: a control group, a low-dose group, and a high-dose group. Control group: Mice received no treatment and were fed normally; Low-dose group: Mice were administered 0.2 mL of 10 mg ... 8 Lactobacillus plantarum SWUN3927 bacterial suspension at CFU / mL; High-dose group: Mice were administered 0.2 mL of 10 CFU / mL via gavage daily. 10 The mice were treated with a CFU / mL culture of *Lactobacillus plantarum* SWUN3927. The experiment lasted for 21 days. During the experiment, the mice had free access to food and water, and their physiological condition was observed.

[0082] (1) Measurement of daily weight gain in mice: Thirty male SPF-grade KM mice (20±2 g) were selected and divided into three groups of 20 mice each. Mice in the low-dose group were administered 0.2 mL of 10 mg / day via gavage. 8CFU / mL Lactobacillus plantarum SWUN3927 bacterial suspension; high-dose group mice were administered 0.2 mL of 10 CFU / mL Lactobacillus plantarum bacterial suspension by gavage daily. 10 The mice were administered CFU / mL of *Lactobacillus plantarum* SWUN3927 bacterial suspension. The control group was administered 0.2 mL of physiological saline by gavage for 21 consecutive days. From the start of gavage, the mice in each group were weighed every 7 days, and the results were recorded.

[0083] The results showed that there was no significant difference in daily weight gain between mice after 7 and 14 days of gavage (P>0.05); after 21 days of gavage, the high-dose group showed a significantly higher daily weight gain compared to the low-dose group and the control group (P<0.05). Figure 4 The results indicate that Lactobacillus plantarum SWUN3927 significantly promotes daily weight gain in mice.

[0084] (2) Effect of feeding yak colostrum-derived Lactobacillus plantarum SWUN3927 on the antioxidant capacity of mice: Based on the experiment in (1), 5 mice from each of the experimental and control groups were randomly selected at 21 days of age. Blood was collected from the orbital sinus, stored at 37℃ for 2 h, centrifuged at 3,500 rpm for 15 min at 4℃, and the supernatant was collected and stored at 4℃. The SOD, AKP and LZM activities in serum were detected using an SOD detection kit (Lanjieke Technology Co., Ltd.), an AKP kit and an LZM kit (Nanjing Jiancheng Biotechnology Research Institute).

[0085] Depend on Figure 5 It was found that 5A represented SOD content; 5B represented AKP content; and 5C represented LZM content. The SOD content in the serum of the three groups of mice was significantly higher in the low-dose and high-dose groups compared to the control group (P<0.01). The AKP content in the serum of the low-dose and high-dose groups was significantly higher than that of the control group (P<0.01), and the AKP content in the high-dose group was significantly higher than that in the low-dose group (P<0.01). The LZM content in the high-dose group was significantly higher than that in the control group (P<0.05), and the LZM content in the low-dose group was significantly higher than that in the high-dose group (P<0.05). These results indicate that gavage administration of different doses of *Lactobacillus plantarum* SWUN3927 bacterial solution can increase the levels of superoxide dismutase, alkaline phosphatase, and lysozyme in serum. Especially with gavage administration of 1×10⁻⁶… 10 CFU / mL Lactobacillus plantarum SWUN3927 has better antioxidant effects.

[0086] (3) Effect of feeding yak colostrum-derived Lactobacillus plantarum SWUN3927 on mouse blood IgG: Based on the experiment in (1), on day 21, 5 mice from each of the experimental and control groups were randomly selected, and blood was collected from the orbital sinus. The blood was stored at 37℃ for 2 h, centrifuged at 3,500 rpm for 15 min at 4℃, and the supernatant was collected and stored at 4℃. The IgG content in the blood was detected using an ELISA kit (Wuhan Boster Biological Engineering Co., Ltd.).

[0087] The results showed that at 7 days after gavage, there was no significant difference in serum IgG levels between the low-dose and high-dose groups and the control group (P>0.05); at 14 days after gavage, the serum IgG level in the high-dose group was significantly higher than that in the control group (P<0.05); at 21 days after gavage, the control group showed a significant difference compared to the low-dose group (P<0.05), and a highly significant difference compared to the high-dose group (P<0.01). This indicates that 1×10 10 CFU / mL significantly increased the secretion of IgG in mouse blood, see [reference needed]. Figure 6 A.

[0088] (4) Effect of feeding yak colostrum-derived Lactobacillus plantarum SWUN3927 on sIgA in mouse intestinal mucosa: (2) Based on the experiment, mice were euthanized by dislocation, and jejunum of the same length was taken. The contents were rinsed with sterile physiological saline, homogenized on ice, incubated overnight at -20℃, and repeatedly frozen and thawed twice. The mixture was then centrifuged at 5000×g for 5 min at 4℃, and the supernatant was collected. The intestinal IgA content of mice was determined according to the instructions of the ELISA kit (Wuhan Huamei Biotechnology Co., Ltd.).

[0089] The results showed that at 7 days after gavage, the sIgA levels in both the high-dose and low-dose groups were significantly higher than those in the control group (P<0.01); at 14 days, the sIgA levels in both the low-dose and high-dose groups were significantly higher than those in the control group (P<0.01), and the sIgA levels in the high-dose group were significantly higher than those in the low-dose group (P<0.05); at 21 days, the sIgA levels in both the low-dose and high-dose groups were significantly higher than those in the control group (P<0.01), and the sIgA levels in the high-dose group were significantly higher than those in the low-dose group (P<0.05). This indicates that 1×10 10 CFU / mL significantly increased sIgA secretion in the mouse jejunum, see details. Figure 6 B.

[0090] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. Lactobacillus plantarum SWUN3927, characterized by: It was isolated from colostrum of Tibetan yaks, with the accession number CCTCC NO: M 20241631, and its rDNA sequence is shown in SEQ ID NO:

1.

2. The use of Lactobacillus plantarum SWUN3927 as described in claim 1 in the preparation of feed additives or animal feed.

3. A feed additive that promotes animal growth, regulates animal immunity, and enhances animal antioxidant capacity, characterized in that: Includes Lactobacillus plantarum SWUN3927 as described in claim 1.

4. An animal feed that promotes animal growth, regulates animal immunity, and enhances animal antioxidant capacity, characterized in that: It includes Lactobacillus plantarum SWUN3927 as described in claim 1 and common animal feed nutrient components.

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