Lactobacillus plantarum grx402 having the ability to promote intestinal absorption of short-chain fatty acids

Abstract

This invention discloses a strain of *Lactobacillus plantarum* Grx402 with the ability to promote intestinal absorption of short-chain fatty acids. *Lactobacillus plantarum* Grx402 was isolated from the intestines of long-lived individuals in Bama, Guangxi (CGMCC No. 28585). Using a Caco-2 cell model to construct an intestinal absorption model of short-chain fatty acids (SCFAs), it was found that *Lactobacillus plantarum* Grx402 can promote the absorption and transport of acetic acid, propionic acid, and butyric acid by intestinal epithelial cells, exhibiting excellent ability to promote intestinal absorption of short-chain fatty acids. It can be used to prepare dairy products or beverages that promote the intestinal absorption of short-chain fatty acids.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology and relates to a strain of Lactobacillus plantarum Grx402 that has the ability to promote the intestinal absorption of short-chain fatty acids. Background Technology

[0002] Short-chain fatty acids (SCFAs), as the most important biomarkers and key substances in gut microbial metabolites, not only provide energy to body tissues and enhance their immunity and motor capabilities, but also improve carbohydrate and fat metabolism, maintain gut immune homeostasis, and inhibit the infection of pathogenic bacteria in the gut. Recent studies have also shown that SCFAs can enhance the body's antiviral immunity and help resist novel coronavirus infection. Furthermore, as signaling regulatory molecules, SCFAs also play an important role in gut-microbe-brain communication. The content of SCFAs in the gut is gradually becoming a key indicator for evaluating and diagnosing various chronic diseases.

[0003] The body primarily absorbs SCFAs through the intestines, but when the gut microbiota is disrupted, this absorption is inhibited. Increasing research indicates that lactic acid bacteria can restore the gut microbiota by improving the body's gut flora. Recent studies have also found that lactic acid bacteria can promote the absorption of nutrients in the intestines. Existing literature ([1] Fan Chenyu. Screening of lactic acid bacteria that promote the absorption of short-chain fatty acids in intestinal epithelial cells and their mechanism of action [D]. Yangzhou University, 2021. [2] Chen Dawei, Ren Chenyu, Fan Chenyu, et al. Promotion effect of Lactobacillus on intestinal absorption of short-chain fatty acids in Caco-2 cell model [J]. Bulletin of Microbiology, 2021. [3] CHEN DW, CHEN CM, QU HX, et al. Screening of Lactobacillus strains that enhance SCFA uptake in intestinal epithelial cells [J]. European Food Research and Technology, 2021, 247(5): 1049-1060.) reported that several strains of Lactobacillus fermentum and Lactobacillus plantarum have the function of promoting the intestinal absorption of propionic acid and butyric acid respectively in the intestinal absorption of single SCFAs (propionic acid or butyric acid) model, but their absorption promotion ability is limited. However, since acetic acid, propionic acid and butyric acid are the main SCFAs in the intestine, they exist in the intestine in a certain proportion. Therefore, the role of lactic acid bacteria in promoting the absorption of SCFAs by intestinal epithelial cells in the intestinal absorption model of single SCFAs described in the aforementioned literature cannot accurately reflect the role of lactic acid bacteria in promoting the intestinal absorption of SCFAs. Furthermore, the ability of lactic acid bacteria to promote the transport of SCFAs by intestinal epithelial cells is also an important indicator for measuring their role in promoting the intestinal absorption of SCFAs. Summary of the Invention

[0004] This invention provides a strain of Lactobacillus plantarum Grx402 that has the ability to promote the intestinal absorption of short-chain fatty acids.

[0005] The *Lactobacillus plantarum* Grx402, which has the ability to promote the intestinal absorption of short-chain fatty acids, as described in this invention, was deposited on October 7, 2023, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, China, with accession number CGMCC No. 28585.

[0006] The *Lactobacillus plantarum* Grx402 described in this invention has the ability to promote the intestinal absorption of short-chain fatty acids, and can promote the absorption and transport of acetic acid, propionic acid and butyric acid by intestinal epithelial cells.

[0007] Furthermore, the present invention provides the application of the above-mentioned Lactobacillus plantarum Grx402 in the preparation of dairy products or dairy beverages that promote intestinal absorption of short-chain fatty acids.

[0008] In the above applications, the dairy product is fermented milk, and the milk beverage is a probiotic solid beverage or a fermented milk beverage.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] This invention isolates Lactobacillus plantarum Grx402 from the intestines of long-lived people in Bama, Guangxi. Using Caco-2 cells, a model of intestinal absorption of multiple short-chain fatty acids (acetic acid, propionic acid, and butyric acid) was constructed. It was found that Lactobacillus plantarum Grx402 can promote the absorption and transport of acetic acid, propionic acid, and butyric acid by intestinal epithelial cells, and has excellent ability to promote the intestinal absorption of short-chain fatty acids. It can be used to prepare dairy products or dairy beverages that promote the intestinal absorption of short-chain fatty acids. Attached Figure Description

[0011] Figure 1 This is a Gram staining image of the strain isolated in Example 1.

[0012] Figure 2 This is a microscope image of Caco-2 cells that adhered to the wall in Example 2, magnified to 100×.

[0013] Figure 3 The values ​​are the TEER values ​​of Caco-2 cell monolayers after different culture times in Example 2.

[0014] Figure 4 This is the standard curve for phenol red in Example 2.

[0015] Figure 5 The images shown are scanning electron microscope (SEM) images of the Caco-2 cell monolayer model in Example 2, where A: Caco-2 cell morphology at 2000× magnification, B and C: Caco-2 cell morphology at 5000× magnification, and D: Caco-2 cell morphology at 15000× magnification.

[0016] Figure 6 The images shown are transmission electron micrographs of the Caco-2 cell model in Example 2, where A and B represent the morphology of Caco-2 cells at 8000× magnification, and C and D represent the morphology of Caco-2 cells at 20000× magnification.

[0017] Figure 7 The effect of SCFA concentration on the survival rate of Caco-2 cells in the model in Example 2 is shown, where different letters indicate significant differences in data (p<0.05).

[0018] Figure 8The effect of six strains of lactic acid bacteria in Example 3 on the absorption of SCFAs by intestinal epithelial Caco-2 cells is shown in Figure 3. A represents the intracellular + basal-side acetic acid content, B represents the intracellular + basal-side propionic acid content, C represents the intracellular + basal-side butyric acid content, and D represents the total intracellular + basal-side acetic acid, propionic acid, and butyric acid content. Different letters indicate significant differences in the data (p<0.05).

[0019] Figure 9 Electrophoresis image of 16S rDNA PCR amplification product of strain Grx402. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to embodiments, accompanying drawings and tables.

[0021] This invention involves seeding Caco-2 cells onto Transwell plates and constructing an intestinal absorption model of SCFAs using indicators such as transepithelial electrical resistance (TEER), phenol red permeability, cell morphology, and cell viability. Then, isolated lactic acid bacteria are inoculated into the model for intervention. Finally, GC-MS is used to determine the content of acetic acid, propionic acid, and butyric acid in the Caco-2 cells and the basal-side culture medium of the Transwell plate in the model to study the effect of lactic acid bacteria on intestinal absorption of SCFAs.

[0022] The relevant culture medium and reagent formulations and test methods in the following examples are as follows.

[0023] (1) MRS liquid medium: 10.0 g peptone, 20.0 g glucose, 10.0 g beef extract, 5.0 g yeast extract, 1 mL Tween-80, 5.0 g C2H3NaO2, 0.2 g K2HPO4·7H2O, 0.05 g MnSO4·4H2O, add deionized water to 1000 mL, sterilize at 121℃ for 15 min, and let cool to room temperature before use. MRS solid medium is based on MRS liquid medium with 15.0 g agar added.

[0024] (2) MEM culture medium: 500mL contains 3000mg / L L-glucose, 219.2mg / L L-glutamine, Hepes, and 10mg / L phenol red. Store at 4℃ for later use.

[0025] (3) MEM complete culture medium: 80% MEM culture medium, 20% high-quality fetal bovine serum, stored at 4℃ for later use.

[0026] Example 1

[0027] 1. Sample collection and lactic acid bacteria isolation

[0028] Fecal samples were collected from long-lived individuals in Bama, Guangxi, who had not taken antibiotics within the past week. After the collected samples were shaken and mixed, they were diluted to the appropriate gradient in a sterile operating table. An appropriate amount was inoculated into MRS solid medium and anaerobically cultured at 37°C. Typical colonies on the plates were picked, streaked to obtain pure colonies, and then inoculated into MRS liquid medium. After anaerobic culture, the pure colonies were freeze-dried for later use.

[0029] 2. Physiological and biochemical tests of lactic acid bacteria

[0030] The isolated strains were Gram-stained, and physiological and biochemical tests were performed on catalase, catalase, nitrate reduction, etc. The results are shown in [Figure number missing]. Figure 1 .

[0031] Nine strains were isolated from the collected samples. Six of them were Gram-positive, rod-shaped, and negative for catalase, catalase, nitrate reduction, and indole tests. Therefore, the six strains were preliminarily identified as lactic acid bacteria and named P97, P1, Grx402, F36, P198, and F18, respectively.

[0032] Example 2

[0033] Construction of a model for intestinal absorption of SCFAs

[0034] (1) Cell recovery and passage

[0035] Thawed Caco-2 cell suspension was rapidly transferred to centrifuge tubes containing MEM complete culture medium. After centrifugation, the supernatant was discarded, and the cells were resuspended in MEM complete culture medium and transferred to cell culture flasks. MEM complete culture medium was then added, and the flasks were incubated at 37°C, 5% CO2, and 95% relative humidity in a CO2 incubator. The culture medium was changed every 1 day. When Caco-2 cells reached 80%-90% confluence and adherent growth, they were passaged. Cells at passages 20-30 can be used for subsequent experiments; morphology is shown in the figure. Figure 2 .

[0036] Depend on Figure 2 It can be seen that, under the microscope, Caco-2 cells growing adherently exhibit a typical cobblestone arrangement, forming tight cell junctions, clear and continuous cell boundaries, smooth surfaces, and only a few small vacuoles, indicating that the cells are in good growth condition.

[0037] (2) Measurement of TEER value of Caco-2 cell monolayer

[0038] The concentration of Caco-2 cells was adjusted to 5 × 10⁻⁶ using MEM complete culture medium. 5Cells / mL were added to the epicalal side (AP) of a 12-well Transwell plate, and 1.5 mL of preheated MEM complete culture medium was added to the basolateral side (BL) of the Transwell plate. The plate was then incubated at 37°C and 5% CO2 for 21 days. The culture medium was changed, the solution on both sides was carefully aspirated, and complete culture medium was added to promote the differentiation and polarization of Caco-2 cells. After changing the medium on day 2, the medium was changed every 2 days, and after day 7, the medium was changed daily, and the culture was continued until day 21.

[0039] The cellular resistance meter electrode was immersed in 70% ethanol for 15 min, dried, and then equilibrated in HBSS solution for 15 min. The short end of the electrode was inserted into the middle of the microwell, and the long end was inserted into the base side. To ensure the accuracy of the measurement results, measurements were taken at three different positions in each microwell, and the average value was calculated. The resistance value of the blank well (cell-free) was used as a control. The TEER value of the Caco-2 cell monolayer was calculated according to formula (1). The results are shown in […]. Figure 3 .

[0040] Resistance value (Ω·cm) 2 )=(R 样品孔 -R 空白孔 )×1.12 (1)

[0041] like Figure 3 As shown, the TEER of the Caco-2 cell model began to proliferate on day 5, with a TEER value of 473 Ω·cm. 2 On day 7, the cellular TEER increased steadily to 600 Ω·cm. 2 This indicates that a cell monolayer has begun to form; the concentration increased to 1647.33 Ω·cm on days 13, 15, and 17, respectively. 2 1679Ω·cm 2 and 1654.33Ω·cm 2 This indicates that Caco-2 cells have formed a continuous, dense monolayer, and their morphology and function are basically stable. Based on the changes in TEER values, it can be determined that Caco-2 cells successfully formed a continuous, dense monolayer on day 13 of culture, exhibiting good barrier function, demonstrating that this cell line has good cell proliferation capacity and density, and possesses absorption and transport functions.

[0042] (3) Determination of phenol red transparency

[0043] A solution containing 1.0 g / L phenol red was prepared using HBSS buffer and diluted to concentrations of 0.5, 1.0, 2.0, 5.0, and 10.0 mg / L. 0.5 mL of each concentration solution was taken and 5.0 mL of 1 mol / L NaOH solution was added. After mixing and color development, the OD values ​​of different concentrations were measured. A standard curve was then established based on the OD values ​​and corresponding concentrations. The results are shown in [Figure number missing]. Figure 4 .

[0044] When Caco-2 cells were cultured for 21 days, three Transwell chambers with good growth were selected, washed with PBS buffer, and 0.5 mL of 5 mg / L phenol red solution was added to the AP side and 1.5 mL of PBS buffer was added to the BL side. The chambers were incubated at 37°C for 2 h. After incubation, 0.5 mL of the BL side solution was taken and 5.0 mL of 1 mol / L NaOH solution was added. The OD value was measured at 560 nm, and the concentration of phenol red on the substrate side was calculated according to the standard curve. The apparent permeability coefficients (Papp) of phenol red were calculated according to formula (2), and the results are shown in Table 1.

[0045]

[0046] Among them, P app The unit of the value is cm / s, dQ / dt is the amount of phenol red transported from the intestinal lumen side of the upper chamber to the basal side per unit time, and A is the filter membrane area of ​​the Transwell chamber (1.12 cm²). 2 ), where ρ is the initial concentration of phenol red.

[0047] Table 1 Apparent penetration coefficients of phenol red (n=3, x±sd)

[0048]

[0049] like Figure 4 As shown, the linear regression equation is obtained as y = 0.0227x + 0.0438 (R²). 2 =0.9995), indicating that within a certain concentration range, the absorbance of phenol red solution exhibits a good linear correlation with its concentration. The leakage amount P of phenol red was measured on day 21 of Caco-2 cell model culture. app 0.22×10 -6 cm / s, when P app <1×10 -6 The cm / s indicates that phenol red did not leak from the chamber to the basal side of the Transwell plate, and the barrier integrity of the Caco-2 cell monolayer was good.

[0050] (4) Morphological observation by scanning electron microscopy

[0051] When Caco-2 cells were cultured for 21 days, the Transwell chambers were removed, and the cells on the Transwell membrane were gently rinsed with PBS buffer. After rinsing, fixative was added and the cells were fixed at room temperature for 2 hours, followed by fixation at 4°C for another 2 hours. The fixative was then aspirated from the fixed samples, washed with PBS buffer, and then fixed with 1% osmium tetroxide pre-cooled to 4°C at room temperature in the dark for 1-2 hours. The samples were washed three times with PBS buffer for 10 minutes each time. Dehydration was then performed using 30%, 50%, 70%, 80%, 90%, 95%, and 100% ethanol, respectively, for 15 minutes each time, twice each time. After critical point drying, the dehydrated samples underwent conductivity treatment, and the samples were observed under a scanning electron microscope. The results are shown in [Figure number missing]. Figure 5 .

[0052] like Figure 5 As shown, preliminary observation under low magnification (2000×) revealed the overall distribution and continuity of the cell monolayer. Caco-2 cells were observed to be covered by microvilli, tightly packed, and fused into a continuous and complete cell monolayer with clear boundaries. Figure 5 As shown in B and 5C, when magnified further to 5000×, the morphology of microvilli can be seen, and the surface microvilli morphology is normally developed; as Figure 5 As shown in Figure D, magnification to 15000× clearly reveals the morphology of individual microvilli. Some cells exhibit longer and more uniform microvilli, while others have shorter and more uneven microvilli. The density may vary depending on the field of view selected. By using scanning electron microscopes at different magnifications, the morphological characteristics of cells can be observed in detail at different levels, laying the foundation for further research on the structure and function of this model.

[0053] (5) Morphological observation by transmission electron microscopy

[0054] When Caco-2 cells were cultured for 21 days, the Transwell chambers were removed, and the cells on the Transwell membrane were gently rinsed with PBS buffer. Cells were then gently scraped from the membrane using a sterile pipette tip. A small amount of PBS buffer was added each time to rinse the Transwell membrane. All cell suspensions collected by centrifugation were used to collect the cell pellet. After fixation, dehydration, and embedding, the pellet was prepared into sections and observed using a transmission electron microscope. The results are shown in the figure below. Figure 6 .

[0055] like Figure 6As shown, after 21 days of culture, the Caco-2 cell monolayer and tight junctions were clearly observed under a low-power microscope (8000×). Further magnification to 20000× revealed clear cell structure and well-differentiated microvilli (arrows in Figures C and D), indicating normal cell structure. Some cells exhibited short and irregular microvilli (arrow in Figure A). Further observation revealed that some cells had longer and more uniform microvilli with tight junctions (arrow in Figure B), indicating established intercellular connections and a dense state with no obvious gaps between cells. Furthermore, Caco-2 cells exhibited a typical asymmetrical distribution, with more microvilli and folds on one side and a flatter side on the other, reflecting the polarity of small intestinal epithelial cells. The more developed microstructure on one side facilitates contact with nutrients in the intestinal lumen, indicating that the Caco-2 cell monolayer model has good structural realism and can serve as a reliable in vitro model for small intestinal nutrient absorption.

[0056] (6) Amount of SCFAs added in the model

[0057] Acetic acid, propionic acid, and butyric acid are the most abundant SCFAs in the human gut, existing in the gut in a molar ratio of approximately 3:1:1. Therefore, in this study, the molar ratio of acetic acid:propionic acid:butyric acid in the SCFAs was 3:1:1. Acetic acid, propionic acid, and butyric acid were mixed in the above ratio to prepare a 1000 mmol / L SCFAs mix stock solution, which was then filtered through a 0.22 μm filter membrane for later use.

[0058] Caco-2 cells were stored at a density of 3 × 10⁶ cells per well. 5 Cells were seeded at a density of [number] cells / mL in Transwell plates and cultured at 5% CO2 and 37°C for 24 h. SCFAs mix was then added to the culture plates to achieve final concentrations of 0, 2.5, 3.0, 4.0, 4.5, 5.0, 10.0, 20.0, and 100 mmol / L in the MEM complete medium. The control group (A) was also included. c The culture medium contains MEM complete medium and cells, but does not contain SCFAs mix; the blank group (A) b The medium contained MEM complete medium but no SCFAs mix or cells; each group had 3 replicates, incubated for 3 h, and then 10 μL of CCK-8 solution was added to each well for another 2 h. The OD value of each well was measured at 450 nm. The survival rate of Caco-2 cells was calculated according to formula (3), and the results are shown in […]. Figure 7 .

[0059]

[0060] Among them, A s Indicates the OD value of the test well, Ac A represents the OD value of the control group. b This represents the OD value of the blank group.

[0061] Depend on Figure 7 It was found that when the concentrations of SCFA mix in the model were 2.5, 10.0, 20.0, and 100.0 mmol / L, the survival rate of Caco-2 cells was significantly lower than that at 0 mmol / L (p<0.05), indicating that these four concentrations of SCFA mix significantly reduced cell viability (p<0.05). However, when the concentrations of SCFA mix were 3.0, 4.0, 4.5, and 5.0 mmol / L, the survival rate of Caco-2 cells was not significantly different from that at 0 mmol / L (p>0.05), indicating that these four concentrations of SCFAs had no significant toxicity to Caco-2 cells (p>0.05). Studies have also shown that the concentration of SCFA mix in the human gut is approximately 5.0 mmol / L, therefore 5.0 mmol / L was chosen as the amount of SCFAs added to the model.

[0062] Example 3

[0063] The effect of lactic acid bacteria on intestinal absorption of SCFAs

[0064] The activated bacterial pellets of the six lactic acid bacteria isolated in Example 1 were collected, washed with sterile PBS buffer, resuspended in antibiotic-free MEM complete culture medium, and the bacterial concentration was adjusted to 1×10⁶. 9 CFU / mL was mixed with MEM complete medium containing 5.0 mmol / L LCFAs mix. After mixing, 0.5 mL was added to the intestinal absorption SCFAs model and incubated at 37°C in a 5% CO2 incubator for 3 h. The cell monolayer after incubation was collected, washed twice with sterile PBS, then once with sterile physiological saline, and finally 1.0 mL of methanol:acetonitrile:water (2:2:1, volume ratio) was added and stored at -80°C for later use.

[0065] Cell monolayers and basal-side culture media containing methanol, acetonitrile, and water were resuspended in 0.5% phosphate solution, centrifuged, and the supernatant was collected. An equal volume of ethyl acetate was added, and the mixture was centrifuged again. The supernatant was collected, and 4-methylvaleric acid (4-methylvaleric acid) at a final concentration of 500 μmol / L was added as an internal standard. The mixture was added to a sample vial, and 1 μL of the supernatant was injected for analysis. Samples were separated using an Agilent DB-WAX capillary column (30 m × 0.25 mm ID × 0.25 μm) gas chromatography system and analyzed by mass spectrometry using an Agilent 7890A / 5975C gas chromatography-mass spectrometry (GC-MS). Peak areas and retention times were extracted using MSD ChemStation software, a standard curve was plotted, and the content of SCFAs in the samples was calculated. Results are shown in [Figure number missing]. Figure 8 .

[0066] Depend on Figure 8 As shown in Figure A, after intervention with strains P97, P1, Grx402, and F36, the content of acetic acid in the model cells and on the basal side was significantly higher than that in the control group (14.74 μg / mL) (p<0.05), while that of P198 was significantly lower than that in the control group (p<0.05). At the same time, Grx402 was significantly higher than the other five strains (p<0.05). This indicates that strains P97, P1, Grx402, and F36 significantly promoted the absorption of acetic acid in the intestine by significantly promoting the absorption and transport of acetic acid by intestinal epithelial cells (p<0.05), while Grx402 had a better absorption-promoting effect than the other five strains, and P198 significantly inhibited the absorption of acetic acid in the intestine (p<0.05).

[0067] Depend on Figure 8 As shown in B, after intervention with the six strains in the experiment, the content of propionic acid in the model cells and on the basal side was greater than 1.36 μg / mL, which was significantly higher than that in the control group (p<0.05). This indicates that all six strains can significantly promote the absorption of propionic acid in the intestine by significantly promoting the absorption and transport of propionic acid by intestinal epithelial cells (p<0.05).

[0068] Depend on Figure 8 C indicates that after intervention with strains P97, P1, Grx402, F36, and F18, the levels of butyric acid in the model cells and on the basal side were significantly higher than those in the control group (3.29 μg / mL, p<0.05), while those in P198 were significantly lower than those in the control group (p<0.05). Meanwhile, Grx402 was significantly higher than the other five strains (p<0.05). This suggests that strains P97, P1, Grx402, F36, and F18 significantly increased intestinal absorption of butyric acid by promoting its absorption and transport in intestinal epithelial cells (p<0.05), with Grx402 showing a better absorption-promoting effect than the other five strains, while P198 significantly inhibited intestinal absorption of butyric acid (p<0.05).

[0069] Depend on Figure 8 As shown in D, after intervention with the five strains, the total content of acetic acid, propionic acid, and butyric acid in the model cells and on the basal side was greater than 19.52 μg / mL, significantly higher than that of the control group and strain P198 (p<0.05). Among them, Grx402 was significantly higher than that of the control group and other strains (p<0.05). This indicates that strain Grx402 promotes the absorption and transport of SCFAs by intestinal epithelial cells, thereby promoting the absorption of SCFAs in the intestine (p<0.05), while strain P198 significantly inhibits the absorption of SCFAs in the intestine (p<0.05).

[0070] Example 4

[0071] Identification of lactic acid bacteria

[0072] (1) API identification

[0073] The strain Grx402 was identified according to the operating instructions of the API 50CHL series identification reagent strips. The results are shown in Tables 2 and 3.

[0074] Table 2 API 50CHL System Qualification Results

[0075]

[0076]

[0077] Note: "+" indicates a positive result; "-" indicates a negative result.

[0078] Table 3 API Comparison Results

[0079]

[0080] As shown in Tables 2 and 3, strain Grx402 is identified as Lactobacillus plantarum, with an identification rate of 98.60%.

[0081] (2) Identification by 16S rDNA sequencing

[0082] Genomic DNA (SEQ ID No. 1) of strain Grx402 was used as a template for PCR amplification, and universal 16S rDNA primers were used for PCR amplification. After electrophoresis detection of the amplification products, they were sent to Sangon Biotech (Shanghai) Co., Ltd. for sequencing. The sequenced sequences were submitted to BLAST for comparison and analysis. The results are shown in Table 4.

[0083] Table 4.16S rDNA alignment results

[0084]

[0085] As shown in Table 4, strain Grx402 is *Lactobacillus plantarum*, with a homology of 99.18%. Therefore, based on the API 50CHL alignment results and the 16S rDNA sequence alignment results, strain Grx402 was identified as *Lactobacillus plantarum*.

[0086] Application examples

[0087] (1) Method for preparing fermented milk containing strain Grx402

[0088] After standardizing whole milk, add 6%-8% sucrose, preheat to 60-70℃, homogenize under 15-20 MPa pressure, heat treat at 95℃ for 8 minutes, cool to 42℃, and inoculate with Lactobacillus plantarum Grx402 at a 3% inoculation rate. Ferment at 42℃ until the pH reaches 4.5, cool, and store at 4℃ to obtain fermented milk containing lactic acid bacteria that promote intestinal absorption (SCFAs).

[0089] (2) Preparation method of solid beverage containing strain Grx402

[0090] The freeze-drying protectant for lactic acid bacteria mainly contains 40%-65% skim milk, 4%-7% sucrose, 4%-8% inulin, 4.5% monosodium glutamate, 5% maltodextrin, 5%-9% glycerol, and 0.05% gelatin, with deionized water added to a final volume of 1000g. After high-density cultivation of strain Grx402, the bacterial cells are obtained by centrifugation and mixed with the protectant at a 1:1 mass ratio. The mixture is then freeze-dried under vacuum to obtain a freeze-dried powder with a moisture content of less than 3.0%. The freeze-dried powder is then mixed with maltodextrin and xylooligosaccharides in a specific ratio under aseptic conditions to produce a solid beverage of *Lactobacillus plantarum* Grx402.

[0091] (3) Preparation method of fermented milk beverage containing strain Grx402

[0092] Fermented milk containing strain Grx402 was mixed and dissolved in 35% of sterilized and cooled water, syrup and compound emulsifying stabilizer (0.5%), homogenized at 60℃ and 15-20MPa, cooled and aseptically filled to produce a fermented milk beverage containing active Lactobacillus plantarum Grx402.

Claims

1. *Lactobacillus plantarum* with the ability to promote intestinal absorption of short-chain fatty acids (… Lactobacillus plantarum Grx402, with accession number CGMCC No. 28585.

2. The *Lactobacillus plantarum* Grx402 according to claim 1, characterized in that, Short-chain fatty acids include acetic acid, propionic acid, and butyric acid.

3. The use of Lactobacillus plantarum Grx402 as described in claim 1 in the preparation of dairy products or dairy beverages that promote intestinal absorption of short-chain fatty acids.

4. The application according to claim 3, characterized in that, The dairy product is fermented milk, and the dairy beverage is a probiotic solid beverage or a fermented milk beverage.

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