Lactobacillus paracasei and application thereof

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to a lactobacillus paracasei strain and application thereof. The invention discloses a Lactobacillus paracasei strain, the name of the Lactobacillus paracasei strain is Lactobacillus paracasei WG-Lpc 63, the Lactobacillus paracasei strain is preserved in China General Microbiological Culture Collection Center on August 27th, 2024, and the preservation number is CGMCC No. 31768. The Lactobacillus paracasei strain is named as Lactobacillus paracasei WG-Lpc 63, and the Lactobacillus paracasei strain is named as Lactobacillus paracasei WG-Lpc 63. The strain disclosed by the invention has good acid production capacity, cholate tolerance and intestinal tract adhesion capacity, and has the effects of regulating intestinal flora balance and relieving intestinal inflammation.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, and more specifically, relates to a strain of Lactobacillus paracasei and its applications. Background Technology

[0002] Colitis is an inflammatory bowel disease, primarily characterized by inflammation and damage to the mucous membranes of the colon (large intestine). This inflammation and damage can interfere with the normal digestion and absorption of food, leading to discomfort and malnutrition. Colitis often causes loss of appetite and indigestion, resulting in weight loss.

[0003] As a type of live microorganism that plays a positive role in the human body, probiotics play an important role in the treatment of colitis. First, they can competitively inhibit the colonization of pathogenic bacteria on the intestinal epithelium, effectively reducing the damage these pathogens cause to the intestinal mucosa. Second, probiotics can significantly improve the intestinal microecological environment, increasing the number of beneficial bacteria while reducing the proportion of harmful bacteria, thus effectively alleviating the intestinal flora imbalance problem in colitis patients. Furthermore, probiotics can stimulate the intestinal mucosal immune system, enhance local immunity, and strengthen the body's defense against pathogens. Finally, probiotics can also promote the proliferation and repair of intestinal mucosal cells, thereby alleviating the intestinal inflammatory symptoms in colitis patients.

[0004] Therefore, it is of great significance to screen for a strain that can alleviate and / or treat colitis. Summary of the Invention

[0005] The purpose of this invention is to provide a strain of Lactobacillus paracasei and its applications. This strain has good acid production capacity, bile salt tolerance and intestinal adhesion ability, and has the effect of regulating the balance of intestinal flora and relieving intestinal inflammation.

[0006] Therefore, the present invention provides the following technical solution.

[0007] The first aspect of the invention provides a strain of *Lactobacillus paracasei*, named *Lactobacillus paracasei* (… Lacticaseibacillus paracasei WG-Lpc 63 was deposited on August 27, 2024, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 31768.

[0008] In a preferred embodiment of the present invention, the strain has good acid production capacity, bile salt tolerance and intestinal adhesion capacity, and has the function of regulating the balance of intestinal flora and relieving intestinal inflammation.

[0009] A second aspect of the invention provides an application of *Lactobacillus paracasei* or its products as described above, as described in any of the following: (1) Prepare products that regulate the balance of intestinal flora; (2) Prepare products for the prevention and / or treatment of intestinal inflammation.

[0010] In a preferred embodiment of the present invention, the product comprises at least one of the following: a probiotic preparation containing Lactobacillus paracasei, a freeze-dried powder, a microcapsule, a solid beverage, fermented milk, and a lactic acid bacteria beverage.

[0011] In a preferred embodiment of the present invention, the product includes health food, functional food and / or pharmaceuticals.

[0012] A third aspect of the invention provides a composition comprising Lactobacillus paracasei as described above; The viable count of *Lactobacillus paracasei* in the composition is 2.0 × 10⁻⁶. 10 -6.0 ×10 11 CFU / g.

[0013] In a preferred embodiment of the present invention, it further comprises prebiotics, γ-aminobutyric acid, hydrolyzed egg yolk powder, and jujube seed powder.

[0014] In a preferred embodiment of the present invention, the prebiotic is selected from one or more of lactose-N-neotetrasaccharide, fructooligosaccharide, galactooligosaccharide, isomaltooligosaccharide, xylooligosaccharide, and spirulina.

[0015] In a preferred embodiment of the present invention, the product comprises the following components by weight: 1-3 parts of Lactobacillus paracasei, 5-10 parts of prebiotics, 1-2 parts of γ-aminobutyric acid, 1-2 parts of hydrolyzed egg yolk powder, and 0.4-0.6 parts of jujube seed powder.

[0016] A fourth aspect of the invention provides the use of the composition as described above in the preparation of a medicament for treating intestinal inflammation.

[0017] By employing the above technical solution, the present invention has at least the following advantages: The Lactobacillus paracasei screened in this invention ( Lacticaseibacillus paracasei WG-Lpc 63 exhibits good acid and bile salt resistance, and demonstrates strong inhibitory effects against four types of putrefactive and pathogenic bacteria, while also exhibiting good cell adhesion. Animal experiments have shown that WG-Lpc 63 can significantly alleviate DSS-induced colitis in mice by improving pathological symptoms such as weight loss, elevated DAI, and colonic shortening caused by DSS. It can also restore the concentration of isobutyric acid in the mouse intestine, alleviate the adverse effects of DSS-induced intestinal inflammation, and significantly increase the abundance of beneficial microorganisms in the mouse intestine, thus promoting the recovery of intestinal health.

[0018] The above description is only a summary of the technical solutions of the present application. In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the following will describe the technical solutions in the preferred embodiments of the present application in detail. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A strain non-targeted screening separation roadmap is shown; Figure 2 WG-Lpc 63 effects on the body weight changes of mice are shown; Figure 3 WG-Lpc 63 effects on the body weight growth rate (A) and DAI index (B) of mice are shown; Figure 4 WG-Lpc 63 effects on the colon length (A), thymus index (B) and spleen index (C) of mice are shown; Figure 5 WG-Lpc 63 effects on the intestinal content short-chain fatty acids acetic acid (A), isobutyric acid (B), butyric acid (C) and isovaleric acid (D) of mice are shown; Figure 6 WG-Lpc 63 effects on the intestinal flora difference OTU (A) and β-diversity (B) of mice are shown; Figure 7 WG-Lpc 63 effects on the intestinal flora α-diversity related index of mice are shown; Figure 8 WG-Lpc 63 effects on the intestinal flora phylum level of mice are shown; wherein, A: phylum level average species abundance in the group, B: phylum level sample species abundance in the group; Figure 9 WG-Lpc 63 effects on the intestinal flora genus level of mice are shown; wherein, A: genus level average species abundance in the group, B: genus level sample species abundance in the group; Figure 10 WG-Lpc 63 significant effects on the intestinal flora genus level of mice are shown; Figure 11 Colony morphological characteristics of WG-Lpc 63 are shown. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the following will describe the technical solutions in the preferred embodiments of the present application in detail, obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0021] Example 1: Sample collection and strain isolation 1 Experimental methods 1.1 Collection of traditional fermented products 1.1.1 Original sample collection Traditional fermented foods such as Qula, soybean, butter, pickles and fermented beef products from Tibet Autonomous Region, Qinghai Province, Gansu Province, Sichuan Province, Guizhou Province, etc. were collected into sterile sampling bags, and the sample information was recorded. The samples were refrigerated and sent back to the laboratory for strain isolation. The collected samples were placed in centrifuge tubes containing sample protection liquid, and the protection liquid was immersed in the samples. The sample information was recorded, and the samples were refrigerated and sent back to the laboratory for strain isolation.

[0022] 1.2 Non-targeted screening of strains 1.2.1 Non-enrichment culture for isolation of strains The collected samples were diluted to 10 1 , and then inoculated into MRS (pH 3.5, 5.5, 6.8), MRS-Mal and MRS-MC solid culture medium for streaking. The samples diluted to 10 3 , 10 5 were spread on the above solid culture medium, and then incubated at 37°C for 24-48 h (anaerobic culture of Bifidobacterium) for screening of Lactobacillus acidophilus, Enterococcus, Pediococcus and Paracaseicolaus strains.

[0023] The collected samples were diluted to 10 1 , 10 3 , 10 5 , and then inoculated into M17 solid culture medium. The 10 1 sample was used for streaking, and the 10 3 and 10 5 samples were used for spreading, and then incubated at 42°C for 24-48 h for screening of Streptococcus and Enterococcus strains.

[0024] The collected samples were diluted to 10 1 , and then inoculated into MRS-SUC solid culture medium and YPD solid culture medium for streaking. The samples diluted to 10 3 , 10 5 were spread on the above solid culture medium, and then incubated at 30°C for 24-48 h for screening of Leuconostoc mesenteroides and yeast strains.

[0025] Typical single colonies (3-5 colonies were picked from each plate) were picked into MRS, M17, MRS-MC liquid medium and YPD liquid medium and cultured at 30°C, 37°C and 42°C for 24 h (Bifidobacterium anaerobic culture), respectively. After secondary streaking, single colonies were picked again for enrichment culture and streaking. Pure colonies were obtained, numbered, and subjected to Gram staining and 16S rDNA sequencing or rDNA intergenic spacer sequence identification. Finally, the strains were lyophilized and stored in the library.

[0026] 1.2.2 Enrichment culture and isolation of strains The collected samples were inoculated into screw tubes containing MRS (pH 3.5, 5.5, 6.8), MRS-Mal liquid medium at different pH, and shaken to mix. After enrichment culture at 37°C for 18-24 h, the samples were used for screening of Lactobacillus acidophilus, Lactobacillus paracasei, Enterococcus, Pediococcus, etc.

[0027] The collected samples were inoculated into screw tubes containing M17 liquid medium, shaken to mix, and then enriched at 42°C for 18-24 h. The samples were used for screening of Streptococcus, Leuconostoc mesenteroides, Enterococcus, etc.

[0028] The collected samples were inoculated into screw tubes containing YPD liquid medium, shaken to mix, and then enriched at 28°C for 18-24 h. The samples were used for screening of yeast. Typical single colonies (3-5 colonies were picked from each plate) were picked into MRS, M17, MRS-MC liquid medium and YPD liquid medium and cultured at 30°C, 37°C and 42°C for 24 h (Bifidobacterium anaerobic culture), respectively. After secondary streaking, single colonies were picked again for enrichment culture and streaking. Pure colonies were obtained, numbered, and subjected to Gram staining and 16S rDNA sequencing or rDNA intergenic spacer sequence identification. Finally, the strains were lyophilized and stored in the library.

[0029] 1.3 Identification of lactic acid bacteria The genomic DNA of lactic acid bacteria was extracted using the Genomic DNA Extraction Kit from Tiangen, and the extracted genomic DNA of lactic acid bacteria was used as a template for 16S rDNA-PCR amplification (primer sequence: F: AGAGTTTGATCCTGGCTCAG (SEQ ID NO. 2), R: GGCTGCTGGCACGTAGTTAG (SEQ ID NO. 3)). After electrophoretic detection of the amplification product, Shanghai Shengong Biological Engineering Co., Ltd. was contacted for sequencing. The sequencing results were compared with the GenBank database by BLAST program to obtain the results.

[0030] 1.4 Lyophilization and preservation of strains The lactic acid bacteria were inoculated in skim milk and cultured to curd (strains that cannot curdle were cultured in the medium to the stationary phase, centrifuged and resuspended in skim milk powder), protective agents were added, and then the mixture was divided into a test tube; the cultured yeast fermentation broth was centrifuged to collect the bacterial precipitate, washed with PBS, and then protective agents were added, and then the mixture was divided into a test tube; the test tube was quickly transferred to a freeze-drying device for vacuum freeze-drying (pre-freezing at -80℃ for 6 h, condenser at -70℃, baffle temperature control at -10℃ for sublimation drying for 30 h, 10℃ for desorption drying for 10 h, and pressure at 0.3 pa), and then stored in a -80℃ refrigerator.

[0031] Bacillus protective agent: skim milk 9.1%, sucrose 6%, trehalose 4%, mannitol 2%, sodium glutamate 5%, glycerol 2%, sterilized at 115℃ for 20 min, and cooled for standby.

[0032] Coccus protective agent: skim milk 9.1%, lactose 2.5%, trehalose 6%, sorbitol 2%, sodium glutamate 2%, glycerol 2%, sterilized at 115℃ for 20 min, and cooled for standby.

[0033] Yeast protective agent: sucrose 11.27%, mannitol 4.88%, malt dextrin 15.43%, skim milk powder 7.82%, sterilized at 115℃ for 20 min, and cooled for standby.

[0034] 2 Experimental results According to the above method, a total of 103 strains of 21 species of lactic acid bacteria were isolated and purified from 84 traditional fermented foods, and were preserved for standby.

[0035] Example 2: Study on the bacteriostatic properties of the strains 1 Experimental method 1.1 Culture and treatment of lactic acid bacteria After the lactic acid bacteria screened and preserved in the above example 1 were activated, they were inoculated into the corresponding liquid medium at an inoculation amount of 3%, and cultured at 37℃ or 42℃ for 24 h. After two generations of continuous activation, activated bacterial liquid was obtained for standby. The activated bacterial liquid was centrifuged at 12000×g for 10 min, and the supernatant was discarded. The bacterial body was collected, washed twice with sterilized 0.9% physiological saline, and resuspended to obtain a bacterial suspension. The turbidity of the bacterial body was measured by a spectrophotometer, and the OD 600nm was 1.00.

[0036] 1.2 Basic property test of lactic acid bacteria 1.2.1 Determination of lactic acid bacteria tolerance to artificial gastric juice Preparation of artificial gastric juice: 0.32% (mass fraction) pepsin was added to 0.18% (mass fraction) NaCl solution, and 1 mol / L hydrochloric acid was used to adjust the pH of the solution to 2.0 or 3.0. Then, the solution was sterilized by filtering through a 0.22 μm sterile microporous filter membrane, and stored at 4°C for standby use.

[0037] The bacterial suspension prepared in step 1.1 above (viable bacterial count: 10 9 cfu / mL) 1.0 mL was inoculated into 9.0 mL of artificial gastric juice at pH 2.0 and pH 3.0, respectively, and anaerobic culture was carried out at 37°C for 3 h. The viable bacterial count was determined by plate counting at 0 h and 3 h, respectively, and the survival rate (%) was calculated according to the following formula (1): ;

[0038] 1.2.2 Determination of bile salt tolerance of lactic acid bacteria The lactic acid bacteria with a survival rate of more than 80% in artificial gastric juice at pH 3.0 were selected for testing of their tolerance to different concentrations of bile salts. 1 mL of bacterial suspension (viable bacterial count: 10 9 cfu / mL) was inoculated into 9 mL of PBS solution containing 0.1% and 0.3% bile salts, respectively, and anaerobic culture was carried out at 37°C. The viable bacterial count was determined by plate counting at 0 h and 3 h, respectively, and the survival rate (%) was calculated according to the following formula (2): ;

[0039] 1.2.3 Inhibition of pathogenic bacteria by lactic acid bacteria Four common pathogenic bacteria, i.e., Escherichia coli, Salmonella, Bacillus subtilis and Staphylococcus aureus, were selected, and the agar diffusion method was used to determine the inhibition of the pathogenic bacteria by the lactic acid bacteria. 100 μL of each pathogenic bacteria was inoculated into LB liquid medium, and culture was carried out at 37°C for 24 h. 100 μL of each pathogenic bacteria was uniformly spread on LB solid medium, and 3 holes were punched in the horizontal plate using a puncher. 200 μL of lactic acid bacteria suspension at a certain concentration was taken and placed in the holes. The plate was placed in a 18°C incubator for diffusion for 12 h, and then transferred to a 37°C incubator. The diameter of the inhibition zone was measured after an obvious inhibition zone appeared, and the measurement was repeated 3 times for each hole.

[0040] 1.3 Determination of adhesion of lactic acid bacteria to epithelial cells The Caco-2 cells were digested and the concentration was adjusted to 2×10 5 ​cell / mL, inoculated in 24-well cell culture plates, and cultured in a 37 °C, 5% CO2 incubator until a single layer of cells was formed. Then washed twice with PBS, and 500 μL of a bacterial suspension with a viable count of 1 x 10 8 CFU / mL was added, and the culture was continued in a 37 °C, 5% CO2 incubator for 2 h. The liquid in the wells was discarded, and the wells were washed twice with sterile PBS solution to remove unattached bacteria. Then, 150 μL of trypsin cell digestion solution was added, and after the cells were completely detached, 350 μL of complete cell culture medium was added to terminate the digestion. The adherent bacteria were counted by the plate colony counting method, and the adhesion rate was calculated according to the following formula (3).

[0041] ;

[0042] 1.4 Determination of the ability of lactic acid bacteria to inhibit the adhesion of pathogenic bacteria to intestinal epithelial cells Caco-2 cells with a concentration of 2 x 10 5 cell / mL were inoculated into 24-well cell culture plates and cultured in a 37 °C, 5% CO2 incubator. After the entire well was covered with a single layer of cells, the ability of lactic acid bacteria to inhibit the adhesion of pathogenic bacteria, including Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella, to intestinal epithelial Caco-2 cells by exclusion, competition, and replacement was studied. The specific steps included the following: 1) Single test: 0.5 mL of Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella with a concentration of 10 8 CFU / mL was added to each well, and the culture was continued in a 37 °C, 5% CO2 incubator for 2 h. Then, the wells were washed twice with sterile PBS to remove unattached bacteria. After that, 0.15 mL of trypsin cell digestion solution was added to each well for digestion, and after the cells were completely detached, 0.35 mL of complete cell culture medium was added to terminate the digestion. The bacterial suspension was collected, and the viable count of adherent pathogenic bacteria was detected in LB medium by the pour plate counting method.

[0043] 2) Exclusion test: 0.5 mL of a lactic acid bacterial suspension with a concentration of 10 8 CFU / mL was added to 24-well cell culture plates, and the culture was continued in a 37 °C, 5% CO2 incubator for 1 h. Then, the wells were washed with sterile PBS to remove unattached lactic acid bacteria. Then, 0.5 mL of Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella with a concentration of 10 8The pathogenic bacterial suspension (CFU / mL) was cultured for another 1 h, then washed twice with sterile PBS to remove unattached cells. Next, 0.15 mL of trypsin cell digestion solution was added to each well for digestion. After complete cell detachment, 0.35 mL of complete cell culture medium was added to terminate digestion. The bacterial suspension was collected and plated on LB medium using the pour plate method to determine the number of viable pathogenic bacteria.

[0044] 3) Competition test: 0.5 mL of a 10% concentration was used. 8 CFU / mL lactic acid bacteria suspension and 0.5 mL of 10 CFU / mL lactic acid bacteria suspension 8 CFU / mL of pathogenic bacteria suspension was added to 24-well cell culture plates and incubated at 37 °C in a 5% CO2 incubator for 2 h. The plates were washed with PBS to remove unattached bacteria. Then, 0.15 mL of trypsin cell digestion solution was added to each well for digestion. After complete cell detachment, 0.35 mL of complete cell culture medium was added to stop digestion. The bacterial suspension was collected and the viable number of attached pathogenic bacteria was determined using the pour plate method on LB medium.

[0045] 4) Substitution test: 0.5 mL of pathogenic bacterial suspension (concentration of 10) 8 Add CFU / mL to 24-well cell culture plates and incubate at 37 °C with 5% CO2 for 1 h. Wash with sterile PBS to remove unattached cells, then add 0.5 mL of lactic acid bacteria suspension (concentration 10). 8 (CFU / mL) and continue culturing for 1 h. Wash with sterile PBS to remove unattached cells, then add 0.15 mL of trypsin cell digestion solution to each well for digestion. After the cells have completely detached, add 0.35 mL of complete cell culture medium to stop digestion. Collect the bacterial suspension and use the pour plate method to detect the number of viable pathogenic bacteria adhering to the suspension in LB medium.

[0046] Three parallel experiments were conducted in each group, and the adhesion inhibition rate of lactic acid bacteria against pathogens was calculated according to the following formula (4): ;

[0047] In the formula: A1 is the number of viable pathogens adhering to Caco-2 cells in the absence of lactic acid bacteria; A2 is the number of viable pathogens adhering to Caco-2 cells in the presence of lactic acid bacteria.

[0048] 1.5 The ability of lactic acid bacteria to regulate gut microbiota 1.5.1 Feed and Animal Sources The basic feed (20% wheat flour, 10% rice flour, 20% corn, 26% stalks, 20% soybeans, 2% fish meal, and 2% bone meal) was purchased from Jiangsu Xietong Pharmaceutical Biotechnology Co., Ltd.

[0049] Six-week-old 60 ICR mice with body weight of about 25.0 ± 4.5 g were purchased from the Comparative Medicine Center of Yangzhou University.

[0050] 1.5.2 Preparation of samples After the lactic acid bacteria were activated, they were inoculated into MRS liquid medium at an inoculation amount of 3%, and cultured anaerobically at 37℃ for 24 h, then centrifuged at 4000 x g for 10 min to collect the bacterial bodies.

[0051] Lactic acid bacteria skim milk suspension: the collected bacterial bodies were suspended in 10% sterilized skim milk, and the viable cell count was adjusted to 10 9 CFU / mL, and stored at 4℃.

[0052] 1.5.3 Test animals and grouping The test animals were raised in the Test Animal Room of the College of Food Science and Engineering of Yangzhou University. The laboratory temperature was 23.0 ± 1.0℃, the humidity was 50 ± 5%, and the light conditions were cycled every 12 h (8:00-20:00), with free access to water and food. The experimental conditions met the “Standard for Laboratory Animal Environment and Facilities of the Ministry of Public Health of the People’s Republic of China”.

[0053] First, 40 ICR mice were adaptively fed for one week, then they were divided into 7 groups according to the random number table method, except for the blank group (NC) of 10, the remaining modeling groups were 8 in each group. The formal experimental period was 21 days, and the first 7 days were given 3% DSS drinking water to the modeling group to establish the colitis model. On the 8th day, the model group was divided into 3 groups (M group, WG-Lpc63 group, and BB12 group (derived from the animal Bifidobacterium lactis subspecies BB12 produced by Danish company Danisco)) according to the random number table method. There was no significant difference in the body weight of the mice in each group after grouping, so the grouping was reasonable.

[0054] During the experiment, the mice were allowed to drink water and eat freely, and the bedding was changed every two days. The mental state, body weight, feed and water consumption of the mice were recorded every day. Each cage was provided with 100 g of feed every day, and then the remaining amount of feed in each cage was weighed at the same time the next day to calculate the food consumption, and it was supplemented to 100 g.

[0055] During the 3% DSS modeling period, the feces of each mouse were collected every day, and the properties and hematochezia were recorded in time, and the DAI was calculated.

[0056] Table 1 Experimental grouping ; 1.5.4 Mouse diet and body weight The remaining amount of feed was weighed and recorded every day during the experiment, and the body weight of the mice in each group was weighed and recorded at a certain period every week, and the fasting body weight was weighed before sacrifice.

[0057] 1.5.5 Disease activity index assessment During the DSS-induced colitis process, the body weight of mice was recorded daily, and the stool character and blood in stool were observed. The daily disease activity index (DAI) was assessed according to the standard shown in Table 2 below, which was summarized according to the literature method. The assessment result of DAI was the sum of the scores of three parts. The score standard was: 0-3 points: healthy intestine; 4-6 points: mild problem of intestine; 7-9 points: moderate problem of intestine; 10-12 points: major problem of intestine.

[0058] Table 2 Assessment of disease activity index of mice colitis ; *Stool character: normal: formed stool; loose: paste-like, not sticking to the anus, semi-formed stool; watery: watery stool, sticking to the anus.

[0059] 1.5.6 Determination of mouse organ index The spleen and thymus of mice were taken and weighed, and the organ index was calculated according to the following formula (5): ;

[0060] 1.5.7 Determination of fecal short-chain fatty acid content of mice The day before the mice were sacrificed, fresh fecal samples were frozen at -80°C for later use. 0.50 g of fecal sample was mixed with 900 μL of ethyl acetate solution of 0.50% phosphoric acid. The mixture was shaken at 4°C for 2 min, then centrifuged at 12,000 rpm for 10 min, the supernatant was reserved, and analyzed by GC-MS using Agilent 7890A / 5975C. Agilent DB-WAX capillary column (30 m x 0.25 mm ID x 0.25 um) was used to separate short-chain fatty acids (SCFA). Next, 1 μL of sample was automatically pumped into the inlet with a split ratio of 10:1. High-purity helium was used as the carrier gas at a flow rate of 1.0 mL / min. The programmed temperature was: initial temperature of 90°C. Then, the temperature was increased to 120°C at a rate of 10°C / min, then to 150°C at a rate of 5°C / min, finally to 250°C at a rate of 25°C / min, and maintained for 2 min. The mass spectrometer used an electron impact ion source (EI) in full SIM mode with an electron energy of 70 eV. The retention time of the detected SCFA was compared with the retention time of the standard sample, and the content of SCFA was calculated from the peak area.

[0061] 1.5.8 Determination of fecal intestinal flora of mice 1.5.8.1 Collection of fecal samples and metagenomic sequencing Fresh fecal samples of mice in each group were collected before gavage at the 1st day of the 4th week of the test, and suspended with 35.0 mL (0.1 mol / L, pH 7.4) of sterile PBS buffer. First, 15.0 mL of buffer was added and vortexed for 5 min, then 10.0 mL of buffer was added and vortexed for 5 min, and finally 10.0 mL of buffer was added and vortexed, so that the sample was uniformly turbid. Centrifugation was performed at 200 x g for 5 min, and the supernatant (bacterial cells) was collected and the precipitate (dregs) was discarded. The washing was repeated twice to remove coarse particles, and then centrifugation was performed at 9000 x g for 3 min, and the precipitate was collected. The precipitate was washed twice with 30.0 mL of PBS, and then the precipitate was collected. The suspension sample was soaked with DETs at 8 times the volume of the fecal sample (1.0 mg of fecal sample was converted to 1.0 μL of preservation solution), and then divided into five parts and stored at -70°C for subsequent DNA extraction.

[0062] DNA of the fecal sample was extracted using the QIAamp Fecal DNA Extraction Kit, and then sent to Shanghai Paissen Biotechnology Co., Ltd. for metagenomic sequencing of the genomic DNA of the sample using the Illumina Miseq sequencing system.

[0063] 1.5.8.2 Illumina library construction The TruSeq library construction kit was used to construct the library, and the 3'-5' exonuclease and polymerase were used to repair the DNA fragments with overhanging ends. A single base "A" was introduced at the 3' end of the repaired DNA fragments, and the 3' end of the adapter contained a single base "T", thereby ensuring that the DNA fragments and the adapter could be connected through "A" "T" complementary pairing, and preventing the mutual connection of DNA inserts during the connection of the adapter to the DNA fragments. Under the action of the ligase, the adapter containing the tag was connected to the DNA fragments. PCR amplification was used to selectively enrich the DNA fragments with adapters at both ends, and the DNA library was amplified, and the number of PCR amplification cycles was minimized to avoid errors in the PCR amplified library. The library was quantified using a fluorescence spectrophotometer, and the PCR enriched fragments were quality controlled using an Agilent 2100 bioanalyzer, and the fragment size and distribution of the DNA library were verified.

[0064] 1.5.8.3 Uniformization of the library and sequencing After the DNA libraries of multiple samples were uniformized to 10.0 nmol / L, they were mixed in equal volumes, and then the mixed library (10.0 nmol / L) was gradually diluted and quantified to 4.0-5.0 pmol / L for sequencing.

[0065] 1.5.8.4 Raw data processing and sample sequence number statistics The test used pair-end sequencing. First, the raw data was subjected to quality control, and low-quality sequences (average quality of 50 consecutive bases > 25, sequence length > 50) were truncated or discarded. The software Flash was used to connect the two ends of the sequences subjected to quality control, and sequences that could not be connected were discarded. According to the requirements of the test, the sequences connected were filtered (consecutive identical bases < 6; ambiguous bases < 1), and the final sequences used for analysis were obtained.

[0066] 1.5.8.5 Bioinformatics analysis The Qiime software was used to divide the sequences into multiple OTUs (Operational Taxonomic Unit). After the OTU was generated, the OTU contained in each sample and the number of sequences contained in each OTU were counted. By finding the nearest relative species, the taxonomic information of each OTU was obtained, and the dilution curve of the OTU generated under the condition of 97% similarity was selected to indicate the sampling depth of the sample genomic DNA. The software mothur was used to calculate the richness index Chao1 and ACE and the diversity index Simpson and Shannon for Alpha diversity analysis, and the data was processed by Excel, PcoA, etc.

[0067] Results and analysis 2.1 Lactic acid bacteria tolerance to artificial gastric juice The 97 strains of lactic acid bacteria were inoculated into pH 2 and pH 3 artificial gastric juice, and the survival rate of each strain was detected. The results are shown in Table 3 below.

[0068] Table 3 Evaluation of lactic acid bacteria tolerance to artificial gastric juice (n = 3, x ± sd) ;

[0069] Table 3 continued ; Note: "NA" means that the survival rate of the strain in the corresponding environment is 0, and the same below.

[0070] 2.2 Lactic acid bacteria tolerance to artificial intestinal juice The 29 strains of lactic acid bacteria with strong acid tolerance were inoculated into sterilized PBS solution with 0.1% and 0.3% bile salt concentration, respectively, and their bile salt tolerance is shown in Table 4 below.

[0071] Table 4 Bile salt tolerance of lactic acid bacteria (n = 3, x ± sd) ; 2.3 Lactic acid bacteria inhibition of intestinal pathogenic bacteria The agar diffusion method was used to detect the bacteriostatic ability of 97 strains of lactic acid bacteria, and the results are shown in Table 5 below. As can be seen from Table 5, WG-Lpc 63 has good inhibitory effect on four kinds of spoilage bacteria and pathogenic bacteria.

[0072] Table 5 Inhibition of lactic acid bacteria on four kinds of pathogenic bacteria (n = 3, x ± sd) ;

[0073] Table 5 Table 1 continued ;

[0074] Table 5 Table 2 continued ;

[0075] Table 5 Table 3 continued ; 2.4 By detecting the adhesion ability of lactic acid bacteria to Caco-2 cells, the results are shown in Table 6 below. As can be seen from Table 6, the adhesion rate of lactic acid bacteria WG-Lpc 63 to Caco-2 cells is good.

[0076] Table 6 Adhesion ability of lactic acid bacteria to Caco-2 cells (n = 3, x ± sd) ; Note: The same row with different superscripts letters means significant difference (p < 0.05).

[0077] The above experiments screened 8 strains with good acid and bile salt tolerance and good inhibitory effect on four kinds of spoilage bacteria and pathogenic bacteria by detecting the artificial gastric juice tolerance, artificial intestinal juice tolerance and inhibitory ability of pathogenic bacteria. The strains are L.P WG 16, L.p WG 20, L.re WG 56, WG-Lpc 63, L.P WG 76, L.la WG 83, L.P WG 84 and L.P WG 90. Among them, the four strains with the highest adhesion rate are WG-L.Pc 63, WG-L.P 84, WG-L.P 79 and WG-L.P 65.

[0078] 2.5 Effect of lactic acid bacteria on adhesion ability of pathogenic bacteria 2.5.1 Effect of lactic acid bacteria on bacteriostatic ability of repulsive adhesion In the exclusion adhesion test, the four preferred strains of lactic acid bacteria can effectively exclude the adhesion of pathogenic bacteria, and the results are shown in Table 7. As shown in Table 7, the adhesion exclusion rates of the four selected strains to Salmonella and Staphylococcus aureus are all more than 60%, among which the adhesion exclusion rate of WG-Lp65 to Salmonella is significantly higher than that of the other three strains (p<0.05); the adhesion exclusion rates of WG-Lpc 63 to Bacillus subtilis, Escherichia coli and Staphylococcus aureus are significantly higher than those of the other three strains (p<0.05).

[0079] Table 7 Inhibition of bacteria by lactic acid bacteria in exclusion adhesion (n=3, x±sd) ; Note: Different superscripts in the same row represent significant differences (p<0.05).

[0080] 2.5.2 Effect of lactic acid bacteria on competitive adhesion inhibition In the competitive adhesion test, the four preferred strains of lactic acid bacteria can effectively inhibit the adhesion of pathogenic bacteria, and the results are shown in Table 8. As shown in Table 8, the competitive adhesion ability of L.P WG65 to Salmonella, Bacillus subtilis and Escherichia coli is significantly higher than that of the other three strains (p<0.05); the adhesion inhibition rates of the four selected strains to Staphylococcus aureus are all more than 80%, among which the competitive adhesion ability of L.P WG79 to Staphylococcus aureus is significantly higher than that of the other three strains (p<0.05).

[0081] Table 8 Inhibition of bacteria by lactic acid bacteria in competitive adhesion (n=3, x±sd) ; Note: Different superscripts in the same row represent significant differences (p<0.05).

[0082] 2.5.3 Effect of lactic acid bacteria on replacement adhesion inhibition In the replacement adhesion test, all lactic acid bacteria can effectively replace the adhered pathogenic bacteria, and the results are shown in Table 9. As shown in Table 9, the adhesion replacement rates of the four selected strains to Bacillus subtilis and Staphylococcus aureus are all more than 80%; among them, the adhesion replacement rate of L.Pc WG 63 to Salmonella, Bacillus subtilis and Staphylococcus aureus is significantly higher than that of the other three strains (p<0.05); the adhesion replacement rate of L.P WG 65 to Escherichia coli is significantly higher than that of the other three strains (p<0.05).

[0083] Table 9 Inhibition of bacteria by lactic acid bacteria in replacement adhesion (n=3, x±sd) ; Note: Different superscripts in the same row represent significant differences (p<0.05).

[0084] The above by measuring the adhesion ability of the 8 strains of lactic acid bacteria to Caco-2 cells, 4 strains with adhesion rate more than 20% are selected, which are WG-Lpc 63, L.P WG 65, L.P WG 79, L.P WG 84 respectively. Then the bacteriostatic properties of the 4 strains at the cell level are explored, and the results show that the 4 selected strains repel, compete and replace the adhesion of Salmonella, Bacillus subtilis, Escherichia coli and Staphylococcus aureus. Among them, the repelling, competing and replacing rate of WG-Lpc 63 to the four kinds of spoilage bacteria or pathogenic bacteria is significantly higher than that of the other three strains. Therefore, WG-Lpc 63 is selected for subsequent animal experiments.

[0085] 2.6 Changes in body weight of mice From Figure 2 It can be found that after DSS modeling, the body weight of mice in the model group (M) increased significantly slower than that in the NC group. After intervention with BB12, the body weight of mice in the BB12 group still approached that of the mice in the M group, while after intervention with the Paracasei WG-Lpc 63 (WG63) of the application, the body weight of mice was closer to that in the NC group.

[0086] In further statistics of the body weight gain rate, it can be found that the body weight gain rate of mice in the WG-Lpc 63 group during the 21 d feeding period was 20.62%, that of the NC group was 18.42%, and that of the M group and the BB12 group was 10.64% and 11.33% respectively, indicating that after DSS modeling, the diarrhea caused by intestinal inflammation and the influence on nutrient absorption of mice caused the body weight gain rate of mice to decrease, while the application of WG-Lpc 63 can effectively improve the body weight gain rate of mice (p<0.05). Figure 3 A).

[0087] The disease activity index (DAI) comprehensively evaluates the daily body weight change, stool character and anal bleeding of mice during the process of DSS-induced colitis. Figure 3 B can be found that the number of mice in the M group distributed in the high DAI index range is the most, and the mice still have symptoms such as soft stool and blood in stool, while after intervention with WG-Lpc 63, the mice are distributed in the medium and low DAI index range, indicating that the symptoms such as soft stool and blood in stool of mice are relieved.

[0088] DSS-induced colitis is usually located in the colon, and is accompanied by the pathological symptom of shortening of the colon length. From Figure 4 A can be seen that the colon length of mice in the M group and the BB12 group is significantly shorter than that in the NC group (p<0.05), and the colon length of mice in the WG63 group intervened with L.Pc WG63 has no significant difference with that in the NC group (p>0.05). The DSS drinking water modeling used in this experiment has no significant effect on the thymus and spleen index of mice (p>0.05)Figure 4 B and 4C). The above results suggest that WG-Lpc 63 significantly alleviates DSS-induced colitis in mice by improving the pathological symptoms of DSS-induced weight loss, DAI increase, and colon shortening.

[0089] 2.7 Short-chain fatty acid content in the intestinal contents of mice Studies have shown that changes in the composition of the intestinal flora often lead to changes in the function of the flora, among which short-chain fatty acids (SCFAs) are a class of metabolites produced by the fermentation of carbohydrates in food by intestinal flora, mainly including acetic acid, butyric acid, isobutyric acid, and isovaleric acid, etc. SCFAs are easily absorbed by the colon and become the preferred energy substrate for colon cells.

[0090] From Figure 5 It can be found that the concentrations of acetic acid, isobutyric acid, butyric acid, and isovaleric acid in the intestinal contents of mice in group M were significantly lower than those in the other groups (p<0.05), indicating that DSS-induced colitis in mice had a significant impact on the concentrations of the four short-chain fatty acids acetic acid, isobutyric acid, butyric acid, and isovaleric acid. The concentrations of acetic acid, isobutyric acid, butyric acid, and isovaleric acid in the intestinal contents of mice in the WG-Lpc 63 group were significantly higher than those in group M (p<0.05), indicating that after WG-Lpc 63 intervention, the adverse effects caused by DSS on intestinal inflammation in mice could be alleviated by restoring the concentrations of acetic acid, isobutyric acid, butyric acid, and isovaleric acid in the intestinal flora of mice.

[0091] 2.8 Effect of lactic acid bacteria on the diversity of intestinal flora in mice The number of OTUs common to or unique to each sample or each group was calculated based on the OTU abundance of each sample. The Venn diagram can present the number of OTUs unique to the group and common to the group.

[0092] Beta diversity (β-diversity) is used to compare the species diversity between samples. Principal coordinates analysis (PCoA) based on the non-weighted UniFrac distance matrix can reflect the β-diversity difference between species, and the closer the distance between two samples, the more similar the species composition of the two samples.

[0093] Alpha diversity (a-diversity) reflects the richness and diversity of the flora within the sample by analyzing the diversity of a single sample, flora abundance (Chao1 and PD whole tree) and flora diversity index (Shannon and Simpson). The Chao1 index and the observed species index refer to the estimated number of OTUs in the sample and the actual number of OTUs contained, respectively. The higher the index, the higher the species abundance in the sample. Both the Simpson index and the Shannon index are used to estimate the diversity of the flora. The larger the index, the higher the diversity of species in the sample.

[0094] 2.8.1 Effect of WG-Lpc 63 on the intestinal flora diversity of mice As shown in Figure 6 A, the number of OTUs common to the NC, M, BB12 and WG63 groups was 65, of which the NC group contained an average of 659 OTUs, and 311 unique OTUs; the M group contained an average of 659 OTUs, and 177 unique OTUs; the BB12 group contained an average of 679 OTUs, and 164 unique OTUs; and the WG63 group contained an average of 615 OTUs, and 164 unique OTUs.

[0095] As shown in Figure 6 B, PCoA analysis of beta diversity showed that the samples were significantly separated from the NC and M groups, and the intestinal flora of the mice in the M group changed significantly. When compared with the WG63 and BB12 groups, it was found that the intestinal flora of the mice in the M group was more similar to that in the NC group. WG63 and BB12 were significantly different from the NC group, but from the diarrhea, colon length and body weight of the mice, the changes in the flora had a positive effect, and further analysis of the phylum and genus levels of the intestinal flora was needed.

[0096] As shown in Figure 7 From the analysis of the a-diversity-related index, it was found that compared with the NC group, the M group, the BB12 group and the WG-Lpc 63 group had no significant difference in Chao1, Shannon and Simpson index. Therefore, the above results suggest that after intervention with lactic acid bacteria, the species abundance does not change, but the proportion of some genera may change, thereby affecting the uniformity of the overall flora.

[0097] 2.9 Analysis of the composition of the intestinal flora of mice 2.9.1 Analysis of the composition of the intestinal flora of mice by WG-Lpc 63 To illustrate the specific changes in the composition of the bacterial flora, the present application further analyzed the species changes in the NC group, the M group, the BB12 group and the WG-Lpc 63 group at the door level, and the results are shown in Figure 8 As shown in Figure 8 , compared with other groups, the species abundance of Verrucomicrobiota and Desulfobacterota was higher in the M group, and the species abundance of Bacteroidota was lower. Compared with the M group, the abundance of Actinobacterota and Campilobacterota in the intestinal flora of mice increased after WG63 intervention.

[0098] The species changes in the NC group, the M group, the BB12 group and the WG-Lpc 63 group were further analyzed at the door level, and the results are shown in Figure 9 As shown in Figure 9 , compared with other groups, the species abundance of norank_f_Muribaculaceae, Staphylococcus and Staphylococcus in the M group decreased, and the species abundance of Lactobacillus increased. Compared with the M group, the abundance of norank_f_Muribaculaceae, Staphylococcus, Helicobacter and Bifidobacterium in the intestinal flora of mice increased after WG-Lpc 63 intervention.

[0099] For further analysis, the difference in the species level of each group was analyzed, and the results are shown in Figure 10 As shown in Figure 10It can be seen that compared with the M group and the BB12 group, after the intervention of WG-Lpc 63, the abundance of Staphylococcus_lentus_g-Staphylococcus (research shows that Staphylococcus lentus (slow staphylococcus) species, and it is found that the response of mice to pathogenic bacteria infection is related to the abundance of Staphylococcus in the intestinal flora. Further in vitro experiments confirm that in the breast milk of mice and humans, Staphylococcus lentus can activate the whole complement pathway through complement protein C1q, and ultimately form a complement membrane attack complex (Membrane Attack Complex, MAC) to cause the death of the bacteria themselves.), Staphylococcus_xylosus (xylose staphylococcus, probiotic species), Bifidobacterium_pseudolongum (can enhance immune response through metabolite inosine), uncultured_bacterium_g_Rikenella (no functional report), uncultured_bacterium_g_Jeotgalicoccus (no functional report), Corynebacterium_stationis (no functional report) in the intestinal flora of mice significantly increased, indicating that after the intervention of L. pc WG63, the abundance of beneficial microorganisms in the intestinal flora of mice significantly increased, which was beneficial to the recovery of their intestinal health.

[0100] In further animal experiments, after DSS modeling, the growth rate of mice decreased, the colon became shorter, and pathological changes such as inflammatory response were caused, and compared with the NC group (blank group), the concentration of acetic acid and isobutyric acid in the intestinal contents of mice was significantly reduced, and the species abundance of Verrucomicrobiota and Desulfobacterota in the feces of mice increased, and the species abundance of Bacteroidota decreased.

[0101] WG-Lpc 63 significantly alleviated DSS-induced colitis in mice by improving the pathological symptoms such as DSS-induced weight loss, DAI increase, and colon shortening, and could restore the concentration of isobutyric acid in the intestinal tract of mice, and alleviate the adverse effects caused by DSS-induced intestinal inflammation in mice. After WG-Lpc 63 intervention, the abundance of Actinobacterota and Campilobacterota in the intestinal flora of mice increased, and the abundance of Staphylococcus lentus, Staphylococcus xylosus and Bifidobacterium pseudolongum and other species also significantly increased, indicating that the abundance of beneficial microorganisms in the intestinal tract of mice was significantly improved after WG-Lpc 63 intervention, which was beneficial to the recovery of intestinal health of mice.

[0102] Based on the above screening, the strain with the best comprehensive performance finally determined is WG-Lpc 63.

[0103] Example 3: Identification and preservation of the strain Based on the screening results of Example 2 above, WG-Lpc 63 was finally selected as the dominant strain for strain identification and preservation: 1.1 Colony characteristics In MRS medium, 37C anaerobic culture for 48h, the bacterial body is rod-shaped.

[0104] 1.2 Microscope morphology Colony smear: Gram-positive, single or paired arrangement.

[0105] 1.3 16S rDNA identification The genomic DNA of lactic acid bacteria was extracted by using Tian Gen Bacterial Genomic DNA Extraction Kit, and the extracted genomic DNA of lactic acid bacteria was used as the template for 16S rDNA-PCR amplification (primer sequence F: AGAGTTTGATCCTGGCTCAG, R: GGCTGCTGGCACGTAGTTAG). After electrophoretic detection of the amplification product, Shanghai Shengong Biological Engineering Co., Ltd. was sent for sequencing, and the results are shown in SEQ ID NO. 1. The sequencing results were compared with the GenBank gene library by BLAST program online, and the results showed that the sequence had more than 99% homology with the identified 16S rDNA sequence of Paracaseolovis casei.

[0106] SEQ ID NO. 1: aggctcagga tgaacgctgg cggcgtgcct aatacatgca agtcgaacga gttctcgttg atgatcggtg cttgcaccga gattcaacat ggaacgagtg gcggacgggt gagtaacacg tgggtaacctgcccttaagt gggggataac atttggaaac agatgctaat accgcataga tccaagaacc gcatggttcttggctgaaag atggcgtaag ctatcgcttt tggatggacc cgcggcgtat tagctagttg gtgaggtaat ctcaccaagc ggatgatacg tagccgaact gagaggttgatcggccac attgggactg agacacggcc caaactccta cgggaggcag cagtagggaa tcttccacaa tggacgcaag tctgatggag caacgccgcgt gagtgaagaa ggctttcggg tcgtaaaact ctgttgttgg agaagaatgg tcggcagagt aactgttgtc ggcgtgacgg tatccaacca gaaagccacg gctaactacg tgccagcagc cgcggtaata cgtaggtggc aagcgttata ccggatttat tgggcgtaaa gcgagcgcag gcggtttttt aagtctgatg tgaaagccct cggcttaacc gaggaagcgcatcggaaact gggaaacttg agtgcagaag aggacagtgg aactccatgtgtagcggtga aatgcgtaga tatatggaag aacaccagtg gcgaaggcgg ctgtctggtc tgtaactgacgctgaggctc gaaagcatgg gtagcgaaca ggattagata ccctggtagt ccatgccgta aacgatgaatgctaggtgtt ggagggtttc cgcccttcag tgccgcagct aacgcattaa gcattccgcc tggggagtacgaccgcaagg ttgaaactcaaaggaattga cgggggcccg cacaagcggt ggagcatgtg gtttaattcgaagcaacgcg aagaacctta ccaggtcttg acatcttttg atcacctgag agatcaggtt tccccttcggg ggcaaaatg acaggtggtg catggttgtc gtcagctcgt gtcgtgagat gttgggttaagtcccgcaac gagcgcaacc cttatgacta gttgccagca tttagttggg cactctagta agactgccggtgacaaaccg gaggaaggtg gggatgacgt caaatcatca tgccccttat gacctgggct acacacgtgctacaatggat ggtacaacga gttgcgagac cgcgaggtca agctaatctc ttaaagccat tctcagttcggactgtaggc tgcaactcgc ctacacgaag tcggaatcgc tagtaatcgc ggatcagcac gccgcggtgaatacgttccc gggccttgta cacaccgccc gtcacaccat gagagtttgt aacacccgaa gccggtggcgtaaccctttt agggagcgag ccgtctaagg tgggacaaat gattagggtg aagtcg Based on the above, the paracasei strain is named Lacticaseibacillus paracasei WG-lpc 63, and is preserved in the China General Microbiological Culture Collection Center on August 27, 2024, with the preservation number of CGMCC No. 31768.

[0107] Example 4: Composition containing Lacticaseibacillus paracasei WG-Lpc 63 A composition containing Lacticaseibacillus paracasei WG-Lpc 63 is provided in this example. The components of the composition include, in parts by weight: Lacticaseibacillus paracasei 2 (live bacteria number 1×10 9Lactobacillus paracasei WG-Lpc 63, 2 parts (viable bacterial count 1 x 10

[0108] A method for preparing a composition of Lactobacillus paracasei WG-Lpc 63 is also provided in this example: 1. Preparation of Lactobacillus paracasei WG-Lpc 63 slurry A single colony of Lactobacillus paracasei WG-Lpc 63 was picked and inoculated into 50 mL of MRS liquid medium and placed in a 37 °C incubator for 18 h. Then, the culture was activated in 250 mL of MRS liquid medium at a 5% inoculation rate and placed in a 37 °C incubator for 24 h. Finally, the activated Lactobacillus paracasei WG-Lpc 63 was inoculated into a 10 L fermenter at a 5% inoculation rate for high-density anaerobic culture under the conditions of 37 °C and pH 6.8 for 18 h. After that, the bacterial cells were collected by centrifugation at 8000 r / min and 4 °C for 15 min, the supernatant was discarded, and the bacterial cells were rinsed twice with sterile phosphate buffer (pH 7.0) to obtain the Lactobacillus paracasei WG-Lpc 63 slurry.

[0109] 2. Preparation of a protective agent The freeze-drying protective agent contains 9.1% skim milk, 6% sucrose, 4% trehalose, 2% mannitol, 5% sodium glutamate, and 2% glycerol, with water as the solvent. The mixture was sterilized at 115 °C for 20 min and then cooled for use.

[0110] Preparation of Lactobacillus paracasei WG-Lpc 63 powder The bacterial cell pellet prepared above was mixed with the protective agent solution at a ratio of 1:5. The mixture was pre-frozen at -40 °C for 5 h to ensure uniform freezing on the inner wall of the container, and then vacuum freeze-dried for 18-20 h to obtain the Lactobacillus paracasei WG-Lpc 63 powder. After rehydration with normal saline, the powder was washed twice. The viable bacterial count of the Lactobacillus paracasei WG-Lpc 63 was determined to be 2.0 x 10 10 -6.0 x 10 11 CFU / g.

[0111] Preparation of a probiotic solid composition containing Lactobacillus paracasei WG-Lpc 63 composition According to the weight fraction, 2 parts of Lactobacillus paracasei powder (viable bacterial count 1 x 10 9 cfu / g), 10 parts of lactose-N-neotetraose, 1 part of gamma-aminobutyric acid, 1 part of hydrolyzed egg yolk powder, and 0.5 parts of Chinese date kernel powder were mixed using a three-position mixer to obtain the probiotic solid composition product.

[0112] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make some changes or modifications to the above disclosed methods and technical contents to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not depart from the technical solution of the present application. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application still falls within the scope of the technical solution of the present application.

Claims

1. A strain of *Lactobacillus paracasei*, characterized in that, The strain is named *Lactobacillus paracasei* ( Lacticaseibacillus paracasei WG-Lpc 63 was deposited on August 27, 2024, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 31768.

2. The *Lactobacillus paracasei* according to claim 1, characterized in that, The strain has good acid production capacity, bile salt tolerance and intestinal adhesion ability, and has the effect of regulating the balance of intestinal flora and relieving intestinal inflammation.

3. The application of Lactobacillus paracasei or its products according to any one of claims 1 or 2: (1) Prepare products that regulate the balance of intestinal flora; (2) Prepare products for the prevention and / or treatment of intestinal inflammation.

4. The application according to claim 3, characterized in that, The product includes at least one of the following: probiotic preparations containing Lactobacillus paracasei, freeze-dried powder, microcapsules, solid beverages, fermented milk, and lactic acid bacteria beverages.

5. The application according to claim 4, characterized in that, The products include health foods, functional foods, and / or pharmaceuticals.

6. A composition, characterized in that, Contains Lactobacillus paracasei as described in claim 1 or 2; The viable count of *Lactobacillus paracasei* in the composition is 2.0 × 10⁻⁶. 10 -6.0 ×10 11 CFU / g.

7. The composition according to claim 6, characterized in that, It also contains prebiotics, gamma-aminobutyric acid (GABA), hydrolyzed egg yolk powder, and jujube seed powder.

8. The composition according to claim 7, characterized in that, The prebiotics are selected from one or more of lactose-N-neotetrasaccharides, fructooligosaccharides, galactooligosaccharides, isomaltooligosaccharides, xylooligosaccharides, and spirulina.

9. The composition according to claim 6, characterized in that, Based on weight, it contains the following components: 1-3 parts of Lactobacillus paracasei, 5-10 parts of prebiotics, 1-2 parts of γ-aminobutyric acid, 1-2 parts of hydrolyzed egg yolk powder, and 0.4-0.6 parts of jujube seed powder.

10. The use of the composition in the preparation of a medicament for treating intestinal inflammation, characterized in that, The composition is the composition according to any one of claims 6-9.

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