Lactobacillus plantarum strain having an intestinal immunity-enhancing activity and composition thereof

Abstract

This invention relates to a strain of *Lactobacillus plantarum* with accession number 35817 from the China General Microbiological Culture Collection Center (CGMCC), and its application in improving intestinal immune function and promoting human intestinal health. This strain can be used as a probiotic ingredient to prepare compositions with the following functions: enhancing resistance to intestinal bacterial infections, maintaining intestinal barrier function, and regulating inflammatory responses. The compositions can be formulated into foods, beverages, or pharmaceuticals for enhancing intestinal immune function and intestinal health.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, specifically to a strain of Lactobacillus plantarum and its application, as well as compositions in which the strain is used, either alone or as an additive, in food, beverages or pharmaceuticals to enhance intestinal immune function and intestinal health. Background Technology

[0002] Under normal physiological conditions, the intestinal mucosal barrier is the first line of defense protecting the intestines from toxins and pathogens. An intact intestinal mucosal barrier consists of physical, immune, chemical, and biological barriers. Disruption of the intestinal mucosal integrity and barrier function increases the host's susceptibility. If pathogens breach the epithelial barrier and invade the body, they can trigger an inflammatory response in the host's intestinal mucosa, and in severe cases, even increase the risk of colorectal cancer.

[0003] Some pathogens can adhere tightly to intestinal epithelial cells, causing attachment / detachment (A / E) damage to host cells and thus affecting the absorption of nutrients from food. For example, enteropathogenic Escherichia coli (EPEC) is one of the leading pathogens causing watery diarrhea in humans, posing a significant threat to public health. In vitro studies have shown that EPEC can adhere to host epithelial cells, inducing epithelial cell dysfunction, including apoptosis and disruption of the tight junction-related mucosal barrier.

[0004] Probiotics were first discovered in 1857 by French microbiologist Louis Pasteur, who identified lactic acid bacteria and revealed the scientific principles behind fermented foods. Probiotics are defined as live microorganisms that, when ingested in sufficient quantities, provide one or more specific health benefits to the host. The most common probiotics include Lactobacillus (Lactobacillus spp.). Lactobacillus ) and Bifidobacterium spp. Bifidobacterium Lactobacillus species produce organic acids (such as lactic acid) during their growth and metabolism, thereby lowering the intestinal pH and creating a microenvironment unfavorable for the growth of pathogenic bacteria, while simultaneously enhancing the antioxidant capacity of intestinal cells. In addition, probiotics have various functional benefits, such as lowering cholesterol, alleviating lactose intolerance, reducing the risk of colon cancer, and enhancing immune function.

[0005] Lactobacilli can form a protective barrier on the surface of the small intestinal mucosa through their own adhesion ability, preventing pathogens from directly contacting intestinal epithelial cells and thus avoiding enteritis caused by pathogens. At the same time, lactobacilli can also compete with pathogens for adhesion sites on intestinal epithelial cells, inhibiting the adhesion of pathogens; in addition, they can also replace pathogens that have already adhered to intestinal epithelial cells through competitive repulsion, thereby reducing or alleviating the occurrence of enteritis.

[0006] Furthermore, probiotics in the host's gut can provide various enzymes and biochemical pathways that the host lacks. They can break down polysaccharides, oligosaccharides, glycoproteins, and other substances in the host's gut, generating short-chain fatty acids (SCFAs) to provide energy for the host. Some probiotics (such as Lactobacillus and Bifidobacterium) can stimulate the production of cytokines through cellular immune mechanisms, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-1 (IL-1), interleukin-4 (IL-4), and interleukin-5 (IL-5). Among these, IL-6 and TNF-α are two key cytokines that play important roles in inflammatory responses, anti-tumor activity, and regulation of the body's immune function. Summary of the Invention

[0007] According to the research described in this application, this invention verified the probiotic function of *Lactobacillus plantarum* using pathogenic *Escherichia coli* ETEC H10407 and HT29 cell models, while using the probiotic LGG (*Lactobacillus rhamnosus* GG strain) as a positive control. Ultimately, it was found that a strain of *Lactobacillus plantarum* isolated from cabbage leaves... Lactobacillus plantarum The strain (preservation number: CGMCC No. 35817) has the effects of improving intestinal flora imbalance, reducing intestinal damage, enhancing intestinal immune function and promoting intestinal health.

[0008] Therefore, this application provides a *Lactobacillus plantarum* (… Lactobacillus plantarum The strain is identified by its accession number CGMCC No. 35817.

[0009] Furthermore, this application also discloses a composition comprising the aforementioned *Lactobacillus plantarum* and / or the fermentation product of the aforementioned *Lactobacillus plantarum*.

[0010] In addition, this application provides a pharmaceutical preparation whose raw materials include the Lactobacillus plantarum or the composition, as well as pharmaceutically acceptable excipients.

[0011] Meanwhile, this application provides a food product whose raw materials include the aforementioned Lactobacillus plantarum or the aforementioned composition.

[0012] Furthermore, this application discloses the use of the Lactobacillus plantarum strain in the preparation of products for the prevention or treatment of intestinal flora imbalance, and the use of the Lactobacillus plantarum strain in the preparation of preparations that enhance intestinal immune function and improve gastrointestinal health.

[0013] Furthermore, this application provides a treatment method that combines prevention / treatment of gut microbiota dysbiosis with enhancement of gut immune function. The method includes using 3.0 × 10⁻⁶... 6 CFU / kg body weight / day up to 1.2×10 9The probiotic dosage is CFU / kg body weight / day, and the composition containing the strain or its derivatives is administered. The specific dosage is calibrated based on the live bacteria content of the probiotics in the composition.

[0014] The specific embodiments of the present invention will be further described in detail with reference to the accompanying drawings and specification. Through the complete disclosure in the specification (including experimental data and claims), the additional technical features, objectives, and advantages of the present invention will become more apparent. Attached Figure Description

[0015] Reference may be made to one or more accompanying drawings to better describe and illustrate embodiments and / or examples of the invention disclosed herein. Additional details or examples used to describe the drawings should not be construed as limiting the scope of any disclosed invention, the currently described embodiments and / or examples, or the currently accepted best mode of carrying out the invention.

[0016] Figure 1 This is a viable count diagram of Lactobacillus plantarum YSB1.

[0017] Figure 2 This is a schematic diagram of the adhesion experiment of Lactobacillus plantarum on HT-29 cells.

[0018] Figure 3 This is a schematic diagram illustrating how Lactobacillus plantarum inhibits the adhesion of pathogenic Escherichia coli.

[0019] Figure 4 This is a schematic diagram of a competitive adhesion experiment between Lactobacillus plantarum and Escherichia coli.

[0020] Figure 5 A schematic diagram of Lactobacillus plantarum replacing pre-adhered Escherichia coli.

[0021] Figure 6 This is a schematic diagram illustrating the measurement of IL-8 secretion in HT-29 cells after co-stimulation with Lactobacillus plantarum and Escherichia coli.

[0022] Figure 7 This is a schematic diagram illustrating the effect of Lactobacillus plantarum on the transepithelial electrical resistance (TEER) of a monolayer of HT-29 cells. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more comprehensive description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for illustrative purposes only and is not intended to limit the scope of the invention.

[0025] The term “colony forming unit” (CFU) used in this article refers to the number of bacterial cells as shown by the growth of microorganisms on agar medium.

[0026] As used in this article, “treatment” refers to the administration of one or more active pharmaceutical agents to a subject who has a disease, has symptoms of a disease, or is predisposed to a disease, with the aim of treating, curing, alleviating, reducing, altering, correcting, improving, enhancing, or influencing the disease, symptoms, or predisposition. For example, “treatment of inflammatory diseases” in this article refers to reducing excessive local or systemic inflammatory responses by inhibiting the expression of IL-8.

[0027] As used herein, the term "effective dose" refers to the amount of an active drug or composition sufficient in the body of a subject to achieve the therapeutic effect described herein. Effective doses can vary, for example, depending on the type or dosage of the drug or composition, as well as the weight, age, and health condition of the subject being treated.

[0028] One embodiment of the present invention provides a strain of *Lactobacillus plantarum* YSB1 isolated from Chinese cabbage leaves. This strain was deposited on September 4, 2025, at the China General Microbiological Culture Collection Center (CGMCC, address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Beichen West Road, Chaoyang District, Beijing, 100101, China), and is classified as *Lactobacillus plantarum* (…). Lactobacillus plantarum (The accession number is CGMCC 35817).

[0029] The strain named YSB1 was isolated and identified as *Lactobacillus plantarum* (YSB1). Lactobacillus plantarum (The accession number is CGMCC No.35817).

[0030] This invention confirms that the *Lactobacillus plantarum* strain has the following characteristics: inhibiting the adhesion of intestinal pathogens; enhancing intestinal barrier integrity; reducing the production of pro-inflammatory cytokines (such as IL-6) induced by enterotoxigenic *Escherichia coli* ETEC H10407 infection and / or enteropathogenic *Escherichia coli* EPEC 0119, thereby alleviating intestinal inflammation and promoting intestinal health.

[0031] The taxonomic characteristics of strain YSB1 were determined by 16S rDNA sequence analysis and biochemical spectrometry analysis using the API bacterial identification system. Its detailed morphological and physiological characteristics are as follows: Morphological characteristics: 1) When cultured in MRS medium, the colonies are small, moist and smooth, with regular edges, and are white; the cells are Gram-positive straight or slightly curved rods, arranged singly, in pairs, or in short chains. 2) This strain is non-motile, facultatively anaerobic, and does not produce cytochrome.

[0032] Fermentation culture conditions for Lactobacillus plantarum strain YSB1: The MRS liquid medium formula is as follows: 10.0 g peptone, 10.0 g beef extract, 5.0 g yeast extract powder, 20.0 g glucose, 5.0 g dipotassium hydrogen phosphate, 2.0 g diammonium hydrogen citrate, 5.0 g sodium acetate, 0.5 g magnesium sulfate heptahydrate, 0.2 g manganese sulfate tetrahydrate, 1.0 g Tween 80, 15.0 g agar, and 1000 mL distilled water; adjust the pH to 6.2-6.4, and sterilize at 121℃ for 30 minutes.

[0033] Lactobacillus plantarum strain YSB1 is a microaerophilic bacterium that grows best in a facultative anaerobic environment; the optimal culture temperature is 37℃, the optimal culture pH is 6.2, and the optimal culture time is 12 hours.

[0034] Data Analysis in the Examples All experimental data were derived from at least three independent biological replicates, and results are expressed as mean ± standard error of mean (SEM). Statistical analysis was performed using IBM SPSS Statistics v17.0 (IBM, USA). Significance testing was conducted using one-way ANOVA combined with the least significant difference (LSD) post-hoc test. The statistical significance threshold was set as follows: P < 0.05 (marked as...). P<0.01 P<0.001 P<0.0001 The charts were created using Microsoft Excel 2016 (Microsoft Corporation, Washington, USA) and conform to the data visualization standards for scientific publications.

[0035] viable count of Lactobacillus plantarum YSB1 Pick a strain of Lactobacillus plantarum from an MRS agar plate ( Lactobacillus plantarum (Accession number: CGMCC 35817) Single colonies, taxonomically confirmed by 16S rDNA sequencing, were cryopreserved at -80°C in glycerol cryopreservation solution. Before the experiment, the strain was inoculated into MRS medium and thawed at 37°C; after reaching mid-logarithmic growth, the cells were collected by centrifugation. Viable cell count and bacterial activity were determined using fluorescence activated cell sorting (FACS), and the results are as follows: Figure 1 As shown, this strain entered a growth plateau phase after 12 hours of culture, with the viable cell count stabilizing; after 6 hours of culture, the viable cell count stabilized at 102. 9 Approximately CFU / mL. The viable count of the strain used in the embodiments of this invention is 1×10⁻⁶. 8 CFU / mL.

[0036] Example 1: Adhesion ability of Lactobacillus plantarum Adhesion assay of *Lactobacillus plantarum* on HT-29 cells: Colonization of *Lactobacillus* on intestinal epithelial cells is a prerequisite for its probiotic effects. Once colonized in the intestine, *Lactobacillus* strains with strong adhesion capabilities can effectively prevent pathogenic microorganisms from contacting and adhering to intestinal mucosal cells, thereby inhibiting enteritis-related diseases caused by pathogens. Therefore, determining the adhesion ability of strains to the human intestinal mucosal surface is one of the key indicators for screening probiotic strains.

[0037] The digested HT-29 cells were then subjected to a reaction at a concentration of 2.5 × 10⁻� 5 HT-29 cells were seeded at a density of 1 cell per well into 12-well cell culture plates and cultured in a CO2 incubator (5% CO2, 95% air) until cell confluence reached 80%-90%. The HT-29 cells in the 12-well plates were washed three times with sterile PBS (pH 7.3), and 100 μL of *Lactobacillus plantarum* suspension (10 μL / well) was added to each well. 8 (CFU / mL) The culture plate was incubated in a 37℃ CO2 incubator for 2 hours to promote bacterial adhesion. The bacterial suspension in the wells was removed, and the plates were washed 5 times with sterile PBS to remove unadhered bacteria. 500 μL of 5% Triton X-100 was added to each well, and the plates were incubated on ice for 5 minutes to lyse the cells and release the adhered bacteria. The lysis buffer was thoroughly pipetted and serially diluted. The viable colonies were counted using the pour plate method (MRS agar plate), and the colony count was recorded as the "adherent Lactobacillus plantarum count". Control group: Included a control group incubated under the same conditions with a bacterial suspension without HT-29 cells. Adhesion rate calculation: The adhesion rate was calculated using the following formula: Adhesion rate (%) = (Adhered bacterial count / Control bacterial count) × 100.

[0038] The results showed that *Lactobacillus plantarum* has a strong adhesion ability to intestinal epithelial cells and can form a biofilm with a wide coverage area, which has a certain inhibitory effect on the adhesion of pathogenic bacteria. Figure 2 ).

[0039] Inhibitory effect of Lactobacillus plantarum on the adhesion of pathogenic Escherichia coli After washing the HT-29 cell monolayer in the 12-well plate three times with PBS (pH 7.3), 400 μL of cell culture medium was added to each well, followed by 100 μL of Lactobacillus plantarum suspension (10... 8 CFU / mL), and incubated in a 37℃ CO2 incubator for 1 hour. Wash 5 times with sterile PBS to remove unadhered lactobacilli; then add 100 μL of Escherichia coli ATCC25922 bacterial suspension (10 CFU / mL) to each well. 8(CFU / mL), and incubated again in a 37℃ CO2 incubator for 1 hour. After incubation, the cells were washed four times with sterile PBS to remove unbound bacteria; 500 μL of 5% (v / v) Triton X-100 was added to lyse the cells, and after mixing with a pipette, the cells were serially diluted. The Escherichia coli ATCC25922 colonies in the experimental and control groups were counted using eosin methylene blue (EMB) agar plates.

[0040] The control group was treated with only Escherichia coli ATCC25922, without prior intervention with Lactobacillus. Each experiment consisted of three technical replicates, each independently repeated three times.

[0041] In the experiment of inhibiting Escherichia coli adhesion, *Lactobacillus plantarum* showed a stronger inhibitory effect on E. coli adhesion, with an inhibition rate of 60%; while the standard strain LGG had an inhibition rate of 53.8% on E. coli adhesion. Figure 3 ).

[0042] Competitive adhesion experiment between Lactobacillus plantarum and Escherichia coli After washing the HT-29 cell monolayer three times with PBS (pH 7.3), 400 μL of cell culture medium was added to each well; then 100 μL of Lactobacillus plantarum suspension (10) was added. 8 CFU / mL) and 100 μL of Escherichia coli ATCC25922 bacterial suspension (10 8 CFU / mL was co-inoculated into each well, and the plates were incubated in a 37°C CO2 incubator for 2 hours. The plates were washed four times with sterile PBS to remove unattached bacteria; 500 μL of 5% (v / v) Triton X-100 was added to lyse the cells, and the mixture was mixed by pipetting and serially diluted. The number of Escherichia coli ATCC25922 colonies in the experimental and control groups was counted using eosin methylene blue (EMB) agar plates.

[0043] Control group: treated with only Escherichia coli ATCC25922, without co-inoculation with Lactobacillus. Each experiment consisted of three technical replicates, each independently repeated three times.

[0044] The results are as follows Figure 4 As shown in the competitive adhesion experiment with Escherichia coli on HT-29 cells, Lactobacillus plantarum YSB1 significantly inhibited the adhesion of Escherichia coli, with an inhibition rate of 52.9%; while in the same competitive experiment, LGG inhibited the adhesion of Escherichia coli on HT-29 cells by 51.4%.

[0045] Lactobacillus plantarum replaces the adhering Escherichia coli After washing the HT-29 cell monolayer three times with PBS (pH 7.3), 400 μL of cell culture medium was added to each well; subsequently, 100 μL of Escherichia coli ATCC25922 bacterial suspension (10) was added to each well. 8 (CFU / mL), and incubate the plates in a 37°C CO2 incubator for 1 hour. Wash three times with sterile PBS to remove unadhered E. coli; then add 100 μL of Lactobacillus plantarum suspension (10 CFU / mL) to each well. 8 (CFU / mL), and incubate the plates again in a 37°C CO2 incubator for 1 hour. After incubation, wash four times with sterile PBS to remove any unattached lactobacilli.

[0046] Add 0.5 mL (500 μL) of 5% (v / v) Triton X-100 to each well to lyse the cells. After mixing with a pipette, perform serial dilutions and count the number of Escherichia coli ATCC25922 colonies in the experimental and control groups using eosin methylene blue (EMB) agar plates.

[0047] The control group only added E. coli ATCC25922 (100 μL, 10 μL) to the HT-29 cell monolayer. 8 Adhesion experiments were conducted using CFU / mL of HT-29 cells, without Lactobacillus replacement treatment. Each experiment was performed in triplicate, with each cell independently repeated three times. After the experiments, the HT-29 cell monolayer was washed four times with sterile PBS to remove unadhered bacteria. 500 μL of 5% (v / v) Triton X-100 was added to lyse the cells, and after mixing with a pipette, serial dilutions were performed. The number of E. coli colonies in the experimental and control groups was counted using eosin methylene blue (EMB) agar plates.

[0048] Control group: Only E. coli ATCC25922 (100 μL, 10⁸ CFU / mL) was added to the HT-29 cell monolayer for adhesion experiments, without any Lactobacillus treatment. Each experiment was performed in triplicate, and each experiment was independently repeated three times.

[0049] The results showed that in the displacement experiment, *Lactobacillus plantarum* YSB1 inhibited the displacement of *Escherichia coli* by 32.3%; while in the same type of displacement experiment, the standard strain LGG inhibited the adhesion of *E. coli* to HT-29 cells by 25.7%. Figure 5 ).

[0050] Example 2: Anti-inflammatory ability – Determination of IL-8 secretion in HT-29 cells after co-stimulation with Lactobacillus plantarum and Escherichia coli Previous studies have shown that when pathogenic bacteria act on cells, they can damage the cellular structure and immune system of epithelial cells, triggering inflammatory responses. These inflammatory responses lead to the production of pro-inflammatory cytokines (such as IL-8). *Lactobacillus plantarum* can prevent pathogenic bacteria from inducing the production of the inflammatory cytokine IL-8 in epithelial cells, thereby inhibiting the development of inflammation.

[0051] Adjust HT-29 cells to 4-5 × 10⁻⁵ 5 The cells were cultured at a concentration of 80%-90% and seeded into 12-well cell culture plates. After the cells reached a confluence of 80%-90%, the HT-29 cells were subjected to microbial intervention.

[0052] To assess the production of the cytokine IL-8, after intervention, the cell culture supernatant was centrifuged (8000×g, 4℃, 10 min) to collect the supernatant; the changes in IL-8 levels in the cell culture supernatant were quantitatively analyzed using a commercially available human IL-8 enzyme-linked immunosorbent assay (ELISA) kit.

[0053] Experiment on inducing IL-8 secretion in HT-29 cells by Lactobacillus plantarum and Escherichia coli: HT-29 cells were adjusted to 4-5 × 10⁻⁶ cells / cells. 5 Cells were cultured at a concentration of [number] cells / mL and seeded into 12-well plates. After the cells formed a completely adherent monolayer, they were washed three times with sterile PBS (pH 7.3), and then the following experimental treatments were performed: Lactobacillus treatment group: 100 μL of Lactobacillus plantarum suspension (1×10⁻⁶ cells / mL) was added to the cell culture plate. 8 CFU / mL), incubated in a 37℃, 5% CO2 incubator for 3 hours; Positive control group (E. coli treatment group): 100 μL of E. coli ATCC25922 bacterial suspension (1×10⁻⁶ CFU / mL) was added to the cell culture plate. 8 CFU / mL), under the same conditions (37℃, 5% CO2), 2、 Incubate for 3 hours.

[0054] 100 μL of Lactobacillus plantarum suspension (1×10⁻⁶) was added to the HT-29 cell monolayer simultaneously. 8 CFU / mL) and 100 μL of Escherichia coli ATCC25922 bacterial suspension (1×10 8 CFU / mL), and co-cultured at 37℃ in a 5% CO2 incubator for 3 hours. (Pretreatment group) HT-29 cells were pretreated with 100 μL of Lactobacillus plantarum suspension (1×10⁻⁶ CFU / mL). 8 After treatment with CFU / mL for 1 hour, the bacteria were washed three times with PBS to remove unadhered lactobacilli, and then 100 μL of Escherichia coli ATCC25922 bacterial suspension (1×10⁻⁶ CFU / mL) was added. 8CFU / mL), and incubated for 2 hours under the same conditions. (Post-treatment group) HT-29 cells were first treated with 100 μL of E. coli ATCC25922 bacterial suspension (1×10⁻⁶ CFU / mL). 8 Stimulate with CFU / mL for 1 hour, wash three times with PBS, and then add 100 μL of Lactobacillus plantarum suspension (1×10⁻⁶ CFU / mL). 8 (CFU / mL) cells were incubated for 2 hours under the same conditions. Negative control group: Untreated HT-29 cells served as the negative control group. Post-experiment processing: Supernatants from all groups were collected, aliquoted, and stored at -80°C for subsequent cytokine analysis.

[0055] like Figure 6 Statistical analysis showed that *E. coli* stimulation induced significant IL-8 production in HT-29 cells (1921 pg / mL), a significant difference compared to the control group (p<0.001). Conversely, the YSB1 strain did not stimulate HT-29 cells to produce IL-8 (46 pg / mL) and also inhibited IL-8 production. Pre-intervention with YSB1 significantly reduced the IL-8 level induced by *E. coli* in HT-29 cells (689 pg / mL), indicating that *Lactobacillus plantarum* YSB1 can protect epithelial cells from damage by inhibiting IL-8 production in HT-29 cells.

[0056] Example 3: Enhancing Intestinal Barrier Capacity – Effects of Lactobacillus plantarum on Transepithelial Resistance (TEER) of HT-29 Cell Monolayers Transepithelial electrical resistance (TEER) is a key indicator for assessing the integrity of the intestinal epithelial cell monolayer. Impaired monolayer integrity leads to increased intestinal permeability, allowing intestinal contents to enter the systemic circulation, triggering abnormal mucosal immune responses, and consequently causing gastrointestinal or systemic diseases.

[0057] Adjust HT-29 cells to 2×10 5 A concentration of cells / mL was determined, and 500 μL of cell suspension was seeded into each well of a cell culture plate. TEER values ​​were measured starting from day 8 of culture to monitor the formation of a cell monolayer. A stable TEER value exceeding 300 Ω·cm² was considered a successful in vitro intestinal epithelial monolayer model. Subsequently, *Lactobacillus plantarum* was added, and the changes in TEER values ​​before and after incubation were measured. The calculation method is as follows: TEER (%) = (TEER value after co-incubation with Lactobacillus plantarum / TEER value before incubation with Lactobacillus plantarum) × 100%.

[0058] like Figure 7 As shown, compared with the negative control group (NC group), the YSB1 strain can significantly increase the TEER value of the cell monolayer by about 52%, indicating its potential to enhance intestinal barrier function.

[0059] These findings suggest that Lactobacillus plantarum YSB1 can reduce intestinal permeability and enhance epithelial integrity, which is crucial for preventing intestinal inflammation and systemic immune activation.

[0060] In summary, the application of *Lactobacillus plantarum* (L.) in in vitro and in vivo intestinal cell models is effective. Lactobacillus plantarum After testing with CGMCC No. 35817, it was confirmed that this strain showed significant activity in enhancing intestinal immune function, improving resistance to pathogenic bacterial infections, maintaining intestinal barrier function, and reducing inflammatory responses such as the secretion of IL-8 and IP-10 induced by Escherichia coli strains.

[0061] As can be seen from the above description, the *Lactobacillus plantarum* (Lactobacillus plantarum) described in this invention... Lactobacillus plantarum CGMCC No. 35817 is a stable and well-characterized probiotic strain that significantly promotes human gut health. This strain enhances the integrity of the intestinal epithelial barrier, reduces bacterial adhesion, and modulates immune responses without causing adverse reactions. Therefore, this strain has outstanding application potential in preventing or alleviating intestinal diseases (including diarrhea and intestinal inflammation) caused by pathogenic bacterial infections.

[0062] Therefore, the novel strain of the present invention can be used as an active ingredient in pharmaceutical compositions that improve or maintain intestinal immune function, or as an additive in food or beverage compositions that support intestinal health and prevent intestinal diseases. The strain's excellent safety and immunomodulatory properties make it a valuable candidate strain for health-promoting preparations.

[0063] Therefore, the Lactobacillus plantarum described in this article ( Lactobacillus plantarum CGMCC strain No. 35817 can be used as a novel medical or nutritional preparation to effectively improve intestinal immune function, maintain intestinal homeostasis, and prevent or alleviate gastrointestinal diseases associated with bacterial infection and inflammation.

[0064] It should be understood that the embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Features or aspects of one embodiment may be applied to or combined with features or aspects of other embodiments as needed. Although one or more embodiments have been described in detail, those skilled in the art will understand that modifications and variations may be made without departing from the spirit and scope of the invention as defined by the following claims.

[0065] The embodiments of this invention are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this invention should be included within the protection scope of this invention.

Claims

1. A strain of *Lactobacillus plantarum* with preservation number CGMCC No. 35817 ( Lactobacillus plantarum The strain has the effect of improving intestinal immune function.

2. A probiotic composition, food composition, beverage composition or pharmaceutical composition comprising the *Lactobacillus plantarum* strain of claim 1, or a culture medium comprising the *Lactobacillus plantarum* strain of claim 1.

3. The pharmaceutical composition according to claim 2, wherein, The daily dosage of the *Lactobacillus plantarum* strain or the culture medium is from about 0.001 g to about 1 g, or 1.0 × 10⁻⁶ g per day. 6 Up to 1.0×10 10 CFU.

4. The pharmaceutical composition according to claim 2 or 3, wherein, The pharmaceutical composition reduces the ability of pathogenic bacteria to adhere to intestinal epithelial cells.

5. The pharmaceutical composition according to any one of claims 2 to 4, wherein, The pharmaceutical composition reduces the release of inflammatory factors IL-8 and / or IP-10 from intestinal epithelial cells.

6. The pharmaceutical composition according to any one of claims 2 to 5, wherein, The pharmaceutical composition resists the invasion of pathogenic bacteria, enhances resistance to intestinal bacterial infections, maintains intestinal barrier function, and / or prevents diarrhea caused by pathogenic bacteria.

7. The pharmaceutical composition according to any one of claims 2 to 6, wherein, The pathogenic bacteria include Escherichia coli.

8. The pharmaceutical composition according to claim 7, wherein, The *E. coli* strains include enterotoxin-producing *E. coli* strain ETEC H10407 and / or enteropathogenic *E. coli* strain EPEC 0119.

9. A food or beverage composition for improving intestinal immune function, the pharmaceutical composition comprising the *Lactobacillus plantarum* strain of claim 1, or a culture medium comprising the *Lactobacillus plantarum* strain of claim 1.

10. The food or beverage composition according to claim 9, wherein, The dosage form of the pharmaceutical composition is a liquid beverage, a solid beverage, an oral liquid, a dairy product, a tablet, or a capsule.

11. A method for improving the intestinal immune function of a subject, the method comprising administering to the subject an effective dose of the *Lactobacillus plantarum* strain of claim 1, the pharmaceutical composition of claim 2, or any one of claims 2 to 6.

12. *Lactobacillus plantarum* with accession number CGMCC No. 35817 ( Lactobacillus plantarum Application of strains in the preparation of drugs for improving intestinal immune function in subjects.

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