Lactobacillus paracasei YT805 and application thereof

Abstract

The invention relates to the field of microorganisms, and particularly discloses lactobacillus paracasei YT805 and application thereof. The strain is separated from fermented yak milk, is preserved in the China General Microbiological Culture Collection Center (CGMCC), the preservation address is No.3, No.1 yard, Beichen West Road, Chaoyang District, Beijing, the preservation number is CGMCC No.31830, the preservation date is September 3, 2024, and the strain is identified as Lactobacillus paracasei. The strain can efficiently and specifically metabolize and utilize inulin, can be used for preparing various fermented products containing prebiotic inulin, and is beneficial to improving intestinal microecological balance, enhancing immunity and promoting nutrient absorption.

Description

Technical Field

[0001] The present application relates to the field of microorganisms, and more specifically, to a Lactobacillus paracasei YT805 and an application thereof. Background Art

[0002] Yak fermented milk is a dairy product made from yak milk, which is fermented by adding lactic acid bacteria (such as thermophilic Streptococcus, Lactobacillus bulgaricus) and other microbial strains during the fermentation process. During the fermentation process, lactic acid bacteria decompose lactose to produce lactic acid, which causes the pH value to drop, thereby promoting the coagulation and thickening of the fermented milk. Fermented milk has a richer taste, is rich in protein and probiotics, and has many benefits for the human body. Studies have found that compared with yak milk, yak fermented milk is richer in nutrients, has more protein, higher fat content, and higher nutritional value. Not only that, the lactose contained in yak fermented milk will be decomposed in large quantities during the fermentation process. For lactose-intolerant groups, yak fermented milk is easier to be digested and absorbed by the human body, which is beneficial to human health.

[0003] However, the taste of yak milk fermented with traditional strains is relatively simple, the aroma is insufficient, the fat degradation is not sufficient, and the market competitiveness is weak. High-quality fermented milk should have a unique flavor. If you want to improve its market competitiveness, improving the flavor of yak fermented milk is an indispensable link. Studies have found that acetic acid, the main flavor substance in fermented milk, is produced by fermentation of Lactobacillus bulgaricus, and diacetyl is produced by fermentation of Streptococcus thermophilus. However, Lactobacillus bulgaricus and Streptococcus thermophilus are not probiotic microorganisms because they are not natural components of the human microbiome.

[0004] In view of this, in order to improve the nutritional value and efficacy of fermented milk, it is necessary to screen strains with special physiological activities in a more targeted manner, especially probiotics that can specifically metabolize the prebiotic inulin. Summary of the invention

[0005] The first purpose of the present application is to provide a Lactobacillus paracasei YT805 (Lactobacillus paracasei), which is isolated from naturally fermented yak milk and can metabolize and utilize inulin efficiently and specifically. The strain is preserved by the General Microbiological Center of the China Microbiological Culture Collection Administration, with a preservation address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, with a preservation number of CGMCC No. 31830, a preservation date of September 3, 2024, and is identified as Lactobacillus paracasei.

[0006] The second object of the present application is to provide a microbial agent, which includes the above-mentioned Lactobacillus paracasei YT805.

[0007] Furthermore, the Lactobacillus paracasei YT805 is a live bacterium with a cell concentration of 10 6 ~10 14 CFU / mL.

[0008] The third object of the present application is to provide a fermentation composition, which includes the above-mentioned Lactobacillus paracasei YT805 and may also include some physiologically acceptable excipients. The composition can be a food, a health product or a medicine.

[0009] Furthermore, the composition also includes prebiotics. Prebiotics are food for probiotics, which can promote the proliferation and survival of probiotics in the intestines, provide intestinal colonization ability, regulate intestinal flora, and thus exert probiotic effects.

[0010] Preferably, the prebiotic is inulin, which is a polysaccharide naturally present in plants. It cannot be digested or hydrolyzed by human saliva and gastrointestinal digestive enzymes. It can be used as a prebiotic to reach the rear end of the intestine in the form of a complete structure, and is selectively utilized by beneficial bacteria such as bifidobacteria and lactobacilli, thereby achieving the purpose of significantly improving the proportion of microbial populations in the intestine. At the same time, as a soluble dietary fiber, inulin can also reduce intestinal pH, accelerate intestinal peristalsis, prevent and relieve constipation, and help food digestion. However, according to existing research reports, not all lactic acid bacteria can utilize inulin, and only a very small number of lactic acid bacteria species or strains have the ability to specifically metabolize and utilize inulin, especially the ability of lactic acid bacteria species or strains derived from yak milk or fermented yak milk to metabolize and utilize inulin has hardly been reported.

[0011] Since Lactobacillus paracasei YT805 can specifically metabolize inulin, when the composition includes both Lactobacillus paracasei YT805 and inulin, the inulin can provide a carbon source for Lactobacillus paracasei YT805 in the intestine as a prebiotic, and the two can play a synergistic role, greatly improving the survival rate and colonization ability of Lactobacillus paracasei YT805 in the intestine, playing a role in regulating the optimal balance of intestinal flora, and bringing benefits to the digestive tract health of the host.

[0012] The fourth objective of the present application is to provide an application of Lactobacillus paracasei YT805 in the preparation of health products or functional foods.

[0013] Furthermore, the functional food includes fermented dairy products, fermented bean products, and fermented fruit and vegetable products.

[0014] The fifth object of the present application is to provide a synbiotic fermented milk, which is prepared by compounding the above-mentioned Lactobacillus paracasei YT805 with a fermented milk starter, adding inulin, and fermenting milk.

[0015] Furthermore, the fermented milk starter includes Lactobacillus bulgaricus and Streptococcus thermophilus, and the ratio of the Lactobacillus paracasei YT805 to the fermented milk starter is 40-60:1, preferably 45-55:1.

[0016] Preferably, the total inoculation amount of the Lactobacillus paracasei YT805 and the fermented milk starter is 3-5%, more preferably, the total inoculation amount is 4-5%.

[0017] Preferably, the amount of inulin added is: 10-20 mg per mL of milk; more preferably, the amount of inulin added is: 13-18 mg per mL of milk.

[0018] In the above technical scheme, Lactobacillus paracasei YT805 (Lactobacillus paracasei) which can specifically metabolize inulin is used as lactic acid bacteria, compounded with a conventional commercial fermented milk starter, and inulin is added as a prebiotic, and the milk is fermented to obtain synbiotic fermented milk, that is, fermented milk rich in both probiotics and prebiotics.

[0019] Synbiotics are a mixture of probiotics and prebiotics. Synbiotics are designed to solve the problem of probiotics surviving in the harsh environment of the gastrointestinal tract. It can promote the physiological activity of probiotics, selectively increase the number of probiotics, inhibit the growth and metabolism of pathogenic bacteria, activate the body's immune response, and restore the balance of intestinal microecology, thereby having a positive effect on the body. Probiotics can increase the number of probiotics in the host's intestines and improve intestinal homeostasis. Although probiotics have a weak ability to survive in the harsh conditions of the gastrointestinal tract, prebiotics such as inulin can promote the proliferation of lactic acid bacteria and help them colonize in the intestine. In addition, inulin can accelerate the production of lactic acid and shorten the fermentation time of fermented milk; during the refrigeration process, it can accelerate the post-acidification rate, so that the product quickly reaches the required acidity, thereby enhancing the flavor of the product. At the same time, the addition of inulin improves the water holding capacity and viscosity of fermented milk, reduces the whey precipitation rate during refrigeration, and improves lipid properties and sensory quality.

[0020] The Lactobacillus paracasei obtained by screening in this application can specifically metabolize inulin and can be used as a starter to obtain synbiotic fermented milk; and because the source of the Lactobacillus paracasei YT805 is naturally fermented yak fermented milk, it is applied to the fermentation of yak milk or ordinary cow milk system, and has strong adaptability, which helps to decompose milk protein and produce acid. This synbiotic fermented milk is milky white, has a strong frankincense, a coordinated smell, and a delicate and mellow taste, a moderate sweet and sour ratio, and is rich in a variety of flavor ingredients. It helps to improve the balance of intestinal microecology, improve immunity, and promote nutrient absorption. It is particularly suitable for special groups such as pregnant women, infants, and gastrointestinal patients. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a thin layer chromatography (TLC) analysis chart of inulin metabolites by Lactobacillus paracasei YT805 in Example 1;

[0022] Figure 2 It is a colony state diagram of Lactobacillus paracasei YT805 in Example 2;

[0023] Figure 3 is a physical picture of three kinds of fermented milk provided in Example 3;

[0024] Figure 4 The acidity test results of the three fermented milks provided in Example 3 are as follows;

[0025] Figure 5 The pH measurement results of the three fermented milks provided in Example 3 are as follows;

[0026] Figure 6 These are the results of measuring the water holding capacity, moisture content, and total solid content of the three fermented milks provided in Example 3. DETAILED DESCRIPTION

[0027] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0028] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0029] Example 1

[0030] Screening and identification of strains

[0031] The Lactobacillus paracasei YT805 in the present embodiment is isolated from yak fermented milk in Ganzi Prefecture, Sichuan Province, and is fermented and cultured in a culture medium with inulin as the sole carbon source to evaluate the ability of lactic acid bacteria to metabolize and utilize inulin (Inulin, represented by inu in the table), and the Lactobacillus paracasei YT805 that can efficiently metabolize and utilize inulin is screened out, and the steps are as follows:

[0032] (1) After the sample is thoroughly shaken and evenly diluted with physiological saline, 10-fold gradient dilution is performed in sequence. 100 μL of the dilution is spread on MRS medium and cultured at 37°C for 24-48 hours. Suspected lactic acid bacteria colonies are selected and inoculated into MRS solid plates. The characteristics of the colonies are observed and recorded. The plates are streaked until single colonies of consistent size and morphology are purified.

[0033] (2) Observe and record the characteristics of the colonies, select colonies with calcium-soluble rings and typical characteristics of lactic acid bacteria, and repeatedly streak and culture them until the colonies are purified.

[0034] (3) Evaluation of the ability of lactic acid bacteria to metabolize and utilize inulin: The above-isolated and purified strains were cultured overnight in MRS liquid medium, and the overnight culture was inoculated into bMRS+(1%, w / v) inulin, bMRS+(1%, w / v) glucose and bMRS+H2O at 1% (v / v), respectively, and cultured anaerobically at 37°C for 72 hours. After the 72-hour fermentation, the OD value and pH of the culture solution at 600nm were measured with bMRS+H2O as a negative control and bMRS+glucose as a positive control to determine the ability of lactic acid bacteria to metabolize and utilize inulin. The results are shown in Table 1:

[0035] Table 1. Metabolism of inulin by isolated strains

[0036]

[0037]

[0038] As shown in Table 1, among the 17 strains isolated, in the experimental group with bMRS + inulin (1% inu) using inulin as the sole carbon source, only the strain numbered YT805 was able to metabolize inulin and glucose, and produce a large amount of acid to reduce the pH of the system. This shows that YT805 is a strain that can efficiently metabolize and utilize inulin.

[0039] (4) Thin layer chromatography (TLC) analysis of metabolites: TLC was used to analyze the changes in inulin composition of strain YT805 during inulin fermentation. The fermentation broth of strain YT805 was centrifuged at 12000rpm for 2min to obtain the supernatant. 6μL of the supernatant was aspirated with a capillary and spotted on a GF254 thin layer chromatography plate, and 6μL of 1% inulin and 3μL of 1% glucose were used as controls. The developing agent was prepared in a ratio of n-butanol: acetic acid: water = 2:2:1 (v / v), and the spotted thin layer chromatography plate was placed in the solvent for development. The color developer was prepared by adding 2g of diphenylamine to 100mL of acetone, and mixing 2mL of aniline and 10mL of phosphoric acid (wt% = 85%). Finally, the developed thin layer chromatography plate was sprayed with the color developer and heated at 105°C for 10min for color development.

[0040] The results are as follows Figure 1 As shown, after the strain YT805 was fermented in the medium with inulin as the only carbon source for 72 hours, it was found that inulin was completely degraded and metabolized by the strain YT805. It can be seen that Lactobacillus paracasei YT805 exhibits a very efficient metabolic ability.

[0041] Example 2

[0042] Identification of bacterial species

[0043] (1) Observe the colonies of strain YT805

[0044] The purified strain YT805 was streaked on an MRS plate and cultured at 37°C for 24-48 hours. The colony characteristics on the MRS medium are: transparent, small dots, irregular, flat, and dry on the surface. Figure 2 shown.

[0045] (2) Identification method

[0046] The overnight culture of YT805 was centrifuged and the bacteria were collected. The lactic acid bacteria genomic DNA was extracted according to the instructions of the DNA extraction kit for subsequent 16S rRNA gene amplification and Sanger sequencing. The primers were the universal primers of the bacterial 16S rRNA gene - 27F-5'-AGAGTTTGATCCTGGCTCAG-3 and 1492R-5'-GGTTACCTTGTTACGACTT-3'. The total volume of the PCR reaction system was 50μL, including 25μL of 1×Taq PCR MasterMix, 2μL of DNA, 1μL of forward primer, 1μL of reverse primer, and finally 21μL of ddH2O. The reaction conditions were: 94℃4min; 94℃30s, 55℃30s, 72℃1.5min, running 34-35 cycles; 72℃10min, and stored at 4℃. After successful amplification, the PCR amplification product was sent to Chengdu Qingke Biotechnology Co., Ltd. for purification and sequencing identification. The obtained sequence was compared with the nucleic acid sequences of known bacteria in the GenBank database by the BLAST program (http: / / blast.ncbi.nlm.nih.gov / Blast.cgi), and the evolutionary tree was constructed using MAGE-X software.

[0047] (3) Identification results

[0048] The sequence of 16S rRNA of strain YT805 is as follows:

[0049] TCCCTAAAAGGGTTACGCCACCGGCTTCGGGTGTTACAAACTCT

[0050] CATGGTGTGACGGGCGGTGTGTACAAGGCCCGGGAACGTATTCACCG

[0051] CGGCGTGCTGATCCGCGATTACTAGCGATTCCGACTTCGTGTAGGCGA

[0052] GTTGCAGCCTACAGTCCGAACTGAGAATGGCTTTAAGAGATTAGCTT

[0053] GACCTCGCGGTCTCGCAACTCGTTGTACCATCCATTGTAGCACGTGTG

[0054] TAGCCCAGGTCATAAGGGGCATGATGATTTGACGTCATCCCCACCTTC

[0055] CTCCGGTTTGTCACCGGCAGTCTTACTAGAGTGCCCAACTAAATGCTG

[0056] GCAACTAGTCATAAGGGTTGCGCTCGTTGCGGGACTTAACCCAACAT

[0057] CTCACGACACGAGCTGACGACAACCATGCACCACCTGTCATTTTGCC

[0058] CCCGAAGGGGAAACCTGATCTCTCAGGTGATCAAAAGATGTCAAGAC

[0059] CTGGTAAGGTTCTTCGCGTTGCTTCGAATTAAACCACATGCTCCACCG

[0060] CTTGTGCGGGCCCCCGTCAATTCCTTTGAGTTTCAACCTTGCGGTCGT

[0061] ACTCCCCAGGCGGAATGCTTAATGCGTTAGCTGCGGCACTGAAGGGC

[0062] GGAAACCCTCCAACACCTAGCATTCATCGTTTACGGCATGGACTACCA

[0063] GGGTATCTAATCCTGTTCGCTACCCATGCTTTCGAGCCTCAGCGTCAG

[0064] TTACAGACCAGACAGCCGCCTTCGCCACTGGTGTTCTTCCATATATCT

[0065] ACGCATTTCACCGCTACACATGGAGTTCCACTGTCCTCTTCTGCACTC

[0066] AAGTTTCCCAGTTTCCGATGCGCTTCCTCGGTTAAGCCGAGGGCTTTC

[0067] ACATCAGACTTAAAAAACCGCCTGCGCTCGCTTTACGCCCAATAAATC

[0068] CGGATAACGCTTGCCACCTACGTATTACCGCGGCTGCTGGCACGTAGT

[0069] TAGCCGTGGCTTTCTGGTTGGATACCGTCACGCCGACAACAGTTACTC

[0070] TGCCGACCATTCTTCTCCAACAACAGAGTTTTACGACCCGAAAGCCT

[0071] TCTTCACTCACGGCGGCGTTGCTCCATCAGACTTGCGTCCATTGTGGAA

[0072] GATTCCCTACTGCTGCCTCCCGTAGGAGTTTGGGCCGTGTCTCAGTCC

[0073] CAATGTGGCCGATCAACCTCTCAGTTCGGCTACGTATCATCGCCTTGG

[0074] TGAGCCATTACCTCACCAACTAGCTAATACGCCGCGGGTCCATCCAAA

[0075] AGCGATAGCTTACGCCATCTTTCAGCCAAGAACCATGCGGTTCTTGGA

[0076] TCTATGCGGTATTAGCATCTGTTTCCAAATGTTATCCCCACTTAAGGG

[0077] CAGGTTACCCACGTGTTACTCACCCGTCCGCCACTCGTTCCATGTTGA

[0078] ATCTCGGTGCAAGCACCGATCATCAACGAGAACT(SEQ ID:01)

[0079] Strain YT805 and Lacticaseibacillus paracasei PC-H1 (Gen Bank accession number: CP123910.1) clustered on the same branch, and the homology reached 100%. Combined with the results of 16s rRNA analysis and morphological characteristics, it can be determined that strain YT805 is Lacticaseibacillus paracasei.

[0080] Example 3

[0081] The synbiotic fermented milk is prepared by using Lactobacillus paracasei YT805, and the specific steps are as follows:

[0082] 1. Preparation of bacterial seed solution:

[0083] (1) Preparation of commercial fermentation seed solution:

[0084] Take 0.1g of commercial yogurt starter (purchased from Baizuan Company, containing Lactobacillus bulgaricus and Streptococcus thermophilus) and inoculate it into 100mL skim milk medium. After fermentation at 42℃ until curdling, take it out immediately and refrigerate it at 4℃ for use. The commercial bacteria fermentation seed liquid (1×10 10 CFU / mL).

[0085] The formula of skim milk culture medium is: 100g skim milk powder, 10g glucose, 1000mL distilled water, sterilized at 115℃ for 15min.

[0086] (2) Preparation of Lactobacillus paracasei YT805 seed liquid:

[0087] The Lactobacillus paracasei YT805 stored at -40°C was streaked and activated, and a single colony was inoculated into 5 mL of MRS broth. After culturing for 12 hours, 5 mL of the culture solution was centrifuged at 8000 r / min for 10 min, and then the supernatant was removed. The bacterial precipitate was washed twice with sterile saline, and the precipitate was transferred into 100 mL of skim milk culture medium. After fermentation at 42°C until the milk curdled, it was immediately taken out and refrigerated at 4°C for use, and the lactic acid bacteria fermentation seed solution (concentration of 4×10 9 CFU / mL).

[0088] 2. Fermentation process:

[0089] (1) To clean the glass bottles, boil water and scald the glass bottles and other utensils that come into contact with milk;

[0090] (2) Add 95 mL of yak milk, weigh 4 g of white sugar, and fortify with 2 g of skim milk powder, add to the yak milk, and stir at 60°C until melted.

[0091] (3) The yak milk was then pasteurized at 90°C for 10 min, cooled to 42°C, and inoculated according to the following groups:

[0092] Group F1 (control group): inoculated with 5 mL of yogurt starter (v / v);

[0093] Group F2 (probiotic group): inoculated with 4.90 mL of lactic acid bacteria seed solution and 0.1 mL of commercial bacteria fermentation seed solution;

[0094] Group F3 (synbiotic group): inoculated with 4.90 mL of lactic acid bacteria seed solution, 0.1 mL of commercial bacteria fermentation seed solution, and 1.5 g of inulin;

[0095] (4) The prepared yak milk is placed in an incubator at 42°C and fermented until curdled. The fermented yak yogurt is placed in a refrigerator at 4°C and then ripened for 12 hours. Figure 3 As shown, the fermented yogurt was stored in a 4°C refrigerator.

[0096] Example 4

[0097] The difference between this embodiment and embodiment 3 is that in the F2 and F3 groups, Lactobacillus paracasei YT805 seed liquid and commercial yogurt starter culture were inoculated into milk at a ratio of 40:1, respectively, and the total inoculation amount was controlled at 4%.

[0098] Example 5

[0099] The difference between this embodiment and embodiment 3 is that: in the F2 and F3 groups, Lactobacillus paracasei YT805 seed liquid and commercial yogurt starter culture were inoculated into milk at a ratio of 60:1, respectively, and the total inoculation amount was controlled at 3%.

[0100] Example 6

[0101] The difference between this embodiment and embodiment 3 is that in group F3, the added amount of inulin is 1 g.

[0102] Example 7

[0103] The difference between this embodiment and embodiment 3 is that in group F3, the added amount of inulin is 2 g.

[0104] Performance testing

[0105] The performance of the prepared synbiotic fermented milk provided in Example 3 was measured:

[0106] Detection method / test method

[0107] The titratable acidity, pH value, total solids content, water holding capacity (WHC), and moisture content of the three groups of yogurt were measured at the end of fermentation (0 day) and on the 7th, 14th, and 21st days.

[0108] The determination methods and results are as follows:

[0109] (1) Acidity determination:

[0110] Take 5g of yogurt, put it in a conical flask, dilute it with 4mL of distilled water, add 2-3 drops of 1% phenolphthalein indicator, titrate it with 0.1mol / L sodium hydroxide standard solution, and shake it gently until the reddish color does not disappear within 30s. The milliliters of sodium hydroxide consumed in the titration multiplied by 20 is the acidity of 100mL of yogurt. Three groups of parallel determinations were performed.

[0111] The results are as follows Figure 4 As shown in the figure, it can be seen that the acidity of the probiotic group (F2) added with YT805 and the synbiotic group (F3) added with YT805+inulin is lower than that of the commercial starter (control group F1), and the acidity of the F3 group is even lower as the storage time increases, which may be due to the metabolism of inulin by YT805 in the later stage of storage.

[0112] (2) pH determination

[0113] Take 3 mL of yogurt in a 10 mL centrifuge tube, mix it well and measure its pH value with a pH meter. The measurements were performed in three groups in parallel.

[0114] The results are as follows Figure 5 As shown, compared with the control group F1, the pH of the F2 and F3 groups was higher, and the pH of the F2 and F3 groups changed less with the extension of storage time.

[0115] (3) Determination of water holding capacity (WHC)

[0116] Measure 10 mL of yogurt and put it into a 50 mL centrifuge tube. The mass of the centrifuge tube is recorded as w1, and the mass after adding yogurt is recorded as w2. Centrifuge at a speed of 6000 r / min for 10 min, let stand for 10 min, remove the supernatant, and record the mass at this time as w3. Three groups of parallel measurements were performed.

[0117] Water holding capacity calculation formula: M = (w3–w1) / (w2–w1)×100%.

[0118] (4) Determination of moisture content

[0119] The moisture content of yogurt products was determined according to the method of the Association of Official Analytical Chemists (AOAC, 1995). Each yogurt product (10 g) was placed in an oven at 105°C for 10 h. The reading was taken at constant weight. The moisture content was then expressed as a percentage (%) of the dry weight of the sample. The mass of the beaker was weighed (m1), and then 10 g of yogurt was weighed in the beaker (m2), placed in an oven at 105°C for 10 hours, and the mass after drying was recorded (m3).

[0120] Moisture content = (m2-m3 / m2-m1) × 100%

[0121] Total solid content = dried sample mass / sample mass before drying × 100%

[0122] The results are as follows Figure 6 As shown in the figure, compared with the control group F1, the water holding capacity and total solid content of the probiotic group F2 and the synbiotic group F3 increased slightly, and the water content decreased slightly, and the increase in the synbiotic group F3 was greater.

[0123] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A Lactobacillus paracasei YT805 (Lactobacillus paracasei), characterized in that It is preserved by the General Microbiology Center of China Microbiological Culture Collection Administration, the preservation address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, the preservation number is: CGMCC No.31830, and the preservation date is September 3, 2024.

2. A microbial agent, characterized in that: The microbial agent contains the Lactobacillus paracasei YT805 as claimed in claim 1.

3. A fermentation composition, characterized in that The fermented composition comprises the Lactobacillus paracasei YT805 as claimed in claim 1.

4. The fermentation composition according to claim 3, characterized in that The fermented composition also includes prebiotics.

5. Use of the Lactobacillus paracasei YT805 according to claim 1, the microbial agent according to claim 2 or the fermented composition according to claim 3 in health products or functional foods.

6. A synbiotic fermented milk, characterized in that: The method is prepared by compounding the Lactobacillus paracasei YT805 as claimed in claim 1 with a fermented milk starter, adding inulin, and fermenting milk.

7. The synbiotic fermented milk according to claim 6, characterized in that: The fermented milk starter comprises Lactobacillus bulgaricus and Streptococcus thermophilus, and the ratio of Lactobacillus paracasei YT805 to the fermented milk starter is 40-60:

1.

8. The synbiotic fermented milk according to claim 7, characterized in that: The total inoculation amount of the Lactobacillus paracasei YT805 and the fermented milk starter is 3-5%.

9. The synbiotic fermented milk according to claim 6, characterized in that: The amount of inulin added is: 10-20 mg of inulin per mL of milk.

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