Lactobacillus rhamnosus and application thereof in brown fermented milk beverage

Abstract

The invention provides a lactobacillus rhamnosus strain and application of the lactobacillus rhamnosus strain in a brown fermented milk beverage, and the lactobacillus rhamnosus strain IMAU13187 has the preservation number of CCTCC (China Center for Type Culture Collection) No. M2024949. The lactobacillus rhamnosus IMAU13187 disclosed by the invention can be effectively applied to preparation of brown fermented milk beverages, the fermentation stability is improved, and the production cost is reduced. The Maillard reaction and long-time fermentation in the milk endow the brown fermented milk beverage with prominent characteristic flavor, and the brown fermented milk beverage has better production and application characteristics.

Description

Technical Field

[0001] The present invention belongs to the field of milk fermentation, and provides a Lactobacillus rhamnosus IMAU13187 and its application in fermenting brown milk beverages. Background Art

[0002] Lactic acid bacteria beverages are made from milk (or milk powder, milk powder, etc.) as raw materials. After processes such as material preparation and homogenization, the base material is obtained by fermenting with lactic acid bacteria. Then, it is mixed and formulated with sugar and acid content in an appropriate ratio with the base material, and then processed through processes such as homogenization. Lactic acid bacteria beverages are naturally fermented by microorganisms, and their fermented flavor and refreshing taste are superior to artificially formulated beverages. Among them, brown lactic acid bacteria beverages are a type of beverage with high sugar and high acid content and containing active lactic acid bacteria. Milk and reducing sugar undergo the Maillard reaction after a certain period of high-temperature treatment, presenting a unique brown color. The Maillard reaction generates brown, even black macromolecular substances such as carboxylic acids, ketones, and aldehydes, which not only provide special flavors and colors but also have characteristics such as antioxidant properties.

[0003] Lactobacillus rhamnosus belongs to the genus Lactobacillus. It is an anaerobic and acid-tolerant, non-spore-forming Gram-positive anaerobic bacterium, mostly existing in the intestines of humans and animals. It is one of the normal flora of the human body and can colonize in the human body for a long time. When Lactobacillus rhamnosus is mixed and fermented with other strains, it can promote the growth and reproduction of other strains, thereby accelerating the fermentation speed of fermented milk and shortening the fermentation time. Moreover, Lactobacillus rhamnosus has good stability in fermented milk. Lactobacillus rhamnosus cannot metabolize lactose, but can metabolize monosaccharides such as glucose and arabinose as well as maltose, and only produces L-lactic acid during the fermentation process without producing other acids, that is, fermented foods containing Lactobacillus rhamnosus will not cause adverse reactions in humans (especially infants and young children). Therefore, this strain can be used as a probiotic for the production of functional fermented dairy products and has broad application prospects in the field of fermented foods. Summary of the Invention

[0004] From the perspective of the starter culture, the present application provides a strain of Lactobacillus rhamnosus, named Lactobacillus rhamnosus IMAU13187. The Lactobacillus rhamnosus IMAU13187 of the present invention can be effectively applied to the preparation of brown fermented milk beverages and improve the fermentation stability. The Maillard reaction in milk and long-term fermentation endow brown fermented milk beverages with prominent characteristic flavors and have good production application characteristics.

[0005] In the first aspect, the present invention provides a strain of Lactobacillus rhamnosus IMAU13187, and its deposit number is CCTCC No. M2024949.

[0006] In a second aspect, there is provided the use of Lactobacillus rhamnosus IMAU13187 of the present invention in the preparation of a brown fermented milk beverage.

[0007] In a third aspect, there is provided a method for preparing a brown fermented milk beverage, which includes using Lactobacillus rhamnosus IMAU13187 of the present invention as a starter.

[0008] Preferably, the fermentation method includes: adding Lactobacillus rhamnosus IMAU13187 to milk and fermenting for a certain period of time at a fermentation temperature; wherein, the method further includes adding glucose to the milk.

[0009] In a preferred embodiment, the fermentation conditions are: the glucose addition amount is 2%, the sucrose addition amount is 6.5%, the protein content in the milk is 2.6%, the inoculation amount is 5.0×10 6 CFU / mL, the fermentation temperature is 37°C, and the fermentation time is 60 h. The optimal addition ratios of the stabilizers are: pectin 0.4%, soybean polysaccharide 0.1%, sodium tripolyphosphate 0.04%,

[0010] In a fourth aspect, there is provided a brown fermented milk beverage prepared by the preparation method of the present invention.

[0011] For the Lactobacillus rhamnosus IMAU13187 of the present invention, the applicant's strain number is CCTCC No. M2024949. The strain was deposited at the China Center for Type Culture Collection on May 22, 2024, with the deposit number: CCTCC NO: M2024949, and the deposit address is Wuhan University, Wuhan, China.

[0012] The Lactobacillus rhamnosus IMAU13187 of the present invention can effectively ferment a brown milk beverage. The electronic nose detected that the flavor substances generated by the milk base fermented with strain IMAU13187 are generally richer. According to the metabolomics data, the metabolite species of strain IMAU13187 are significantly richer than those of IMAU99155. Among the fatty acid metabolites after fermentation, the levels of stearic acid and oleic acid increase the most. Oleic acid and stearic acid are beneficial because they can soften blood vessels and are therefore likely to promote health. In addition to being beneficial to health, the fatty acid composition also affects the smell, taste and texture of food. Free fatty acids can also participate in the metabolic reaction matrix related to aroma and aromatic substances. After being fermented into a beverage, the contents of various metabolites including polypeptides, free amino acids, carbohydrates, fatty acids, vitamins and nucleosides have changed significantly. Some of these changes contribute to the unique sensory quality of the fermented brown milk beverage. The Lactobacillus rhamnosus of the present invention can be a potential choice as a milk fermenting agent. Description of the Drawings

[0013] Figure 1It is the colony morphology of Lactobacillus rhamnosus IMAU13187 of the present invention.

[0014] Figure 2 Mean value diagram of each level of factors in the orthogonal test for the fermentation of the milk beverage base of IMAU13187.

[0015] Figure 3 Results of pH value, fermentation time test, titratable acidity and viable cell count after orthogonal optimization of the milk base.

[0016] Figure 4 Changes in flow factor (FI), solid-liquid balance value (SLB), macroscopic viscosity index (MVI), and elasticity factor (EI) during the fermentation process.

[0017] Figure 5 Changes in the viable cell count of milk beverages of each strain during storage at different temperatures.

[0018] Figure 6 Radar chart of the electronic nose detection results of the milk beverage product.

[0019] Figure 7 KEGG enrichment diagram of differential metabolites, LGG group vs. IMAU13187 group.

[0020] Figure 8 KEGG enrichment diagram of differential metabolites, IMAU13187 group vs. IMAU99155 group. Detailed implementation manners

[0021] The following will describe the detailed implementation manners of the present invention with reference to the accompanying drawings. The experimental methods used in the implementation examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0022] Materials and methods

[0023] Unless otherwise specified, the reagents and instruments used in the following examples are all conventional reagents and instruments in the art and can be obtained through commercial purchase. The methods used are conventional methods, and those skilled in the art can, without any doubt, know how to carry out the described solutions and obtain the corresponding results according to the content of the implementation.

[0024] Materials used in the examples:

[0025] Lactobacillus rhamnosus IMAU13187 and IMAU99155 were separately isolated from breast milk and traditional fermented milk. Lactobacillus rhamnosus IMAU99155 was deposited at the China Center for Type Culture Collection on May 22, 2024, and its deposit number is CCTCC NO: M2024950.

[0026] Lactobacillus rhamnosus IMAU13187 was deposited at the China Center for Type Culture Collection on May 22, 2024, with the deposit number: CCTCC NO: M2024949.

[0027] Lactobacillus rhamnosus LGG was purchased from Chr. Hansen (China) Biological Co., Ltd.

[0028] Skim milk powder (protein content 3.3%, NZMP, New Zealand);

[0029] Glucose (Fuchen (Tianjin) Chemical Reagent Co., Ltd.), white granulated sugar (COFCO Sugar Co., Ltd.);

[0030] MRS solid medium, M17 solid medium, Shanghai Yili Biotechnology Co., Ltd.;

[0031] The main reagents used in the examples are shown in Table 1.

[0032] Table 1 Main reagents

[0033]

[0034]

[0035] Table 2 Main instruments and equipment

[0036]

[0037] Example 1: Screening and identification of strains

[0038] 1. Observation of strain phenotypic characteristics

[0039] Colony characteristics: The strain was streaked on MRS solid medium and cultured in a constant temperature incubator at 37°C for 48 h. Observe the colony morphology. Pick small and typical colonies after 48 h of culture and prepare slides by smearing method, then perform Gram staining, observe with a microscope and take microscopic examination photos.

[0040] Electron microscope pictures: Take 1 mL of Lactobacillus rhamnosus bacterial liquid cultured in liquid MRS medium for 12 h, wash it twice with phosphate buffer solution (0.1 M, pH 7.4); centrifuge at 5,000 rpm for 5 min, discard the supernatant; add an equal volume of sterilized glutaraldehyde solution to resuspend, repeat the operation to adjust the bacterial liquid concentration to 1×10 8 CFU / mL, pipette 10 μL of the bacterial liquid and drop it on a clean silicon wafer, dry it in an oven at 37°C, and then observe it under a scanning electron microscope (Hitachi FlexSEM1000Ⅱ) at U = 10 kV and spot = 20.

[0041] 2. Strain identification

[0042] Colony morphology pictures are shown in the attached drawingsFigure 1 (a), The colony morphology of Lactobacillus rhamnosus IMAU13187 was circular, with neat edges, smooth and plump surfaces, prominent centers, milky white in color, and uniform texture. All of them conformed to the individual colony morphology of Lactobacillus rhamnosus. See the microscopic examination photos at Figure 1 (b), Under an optical microscope, both strains showed short rod shapes, no spores, and were Gram-positive. This conformed to the microscopic examination characteristics of Lactobacillus rhamnosus. See the results of the electron microscope photos at Figure 1 (c), Both strains of Lactobacillus rhamnosus were short rod-shaped, with blunt rounded ends, and the bacterial cells were arranged dispersedly without a fixed arrangement form. There were irregular depressions on the surface of the bacterial cells, which conformed to the characteristics of the electron microscope photos of Lactobacillus rhamnosus.

[0043] Example 2: Preparation of brown milk fermentation base material

[0044] Weigh the milk base powder separately and mix them evenly. While stirring, add them to the pre-weighed and pre-heated distilled water at 60 °C. Keep stirring for 15 min and then hydrate for 30 min. During this period, remove the floating foam, homogenize (15 - 20 MPa), raise the temperature to 97 °C, carry out browning for 3 h, then cool to 37 °C, inoculate Lactobacillus rhamnosus IMAU99155, and then place it in a constant temperature incubator pre-heated to the target temperature for fermentation. Stop fermentation after reaching the fermentation end point (pH is 3.60 - 3.80 and the titratable acidity is 180 °T - 200 °T), break the emulsion and quickly cool to about 4 °C. At this time, it is the brown milk fermentation base material.

[0045] Preparation of milk beverage

[0046] After obtaining the fermented milk base material, keep it for 0-pressure homogenization. Weigh white granulated sugar, other ingredients and distilled water according to the ratio in Table 3 below and add them to the pre-weighed distilled water. After stirring evenly, raise the temperature to 95 °C and keep it for 5 minutes for sterilization. After cooling to room temperature, weigh the homogenized fermented base material and mix it fully with other components, homogenize (15 - 20 MPa), and then package and store. Conduct sensory evaluation at 1 d (at the beginning of storage) and 21 d (at the end of storage) respectively, and measure the pH value, titratable acidity, and viable bacteria count every 7 d during this period. At the same time, use non-targeted metabolomics to further analyze the growth characteristics and action mechanisms of each strain during the fermentation and storage of the milk beverage.

[0047] Table 3 Recipe details of active lactic acid bacteria beverage

[0048]

[0049]

[0050] Example 3: Experimental design for optimizing the recipe process of milk beverage base material with each strain

[0051] Differences in strains directly affect the fermentation characteristics of milk-based substrates and the flavor and composition of active functional substances in the prepared beverages of the fermentation products. In this study, three strains of Lactobacillus rhamnosus, IMAU13187, IMAU99155, and LGG, were used to conduct a set of orthogonal tests with four factors and three levels under the conditions in Tables 4 and 5. During fermentation, the pH value and titratable acidity were measured every 12 hours to explore the optimal milk-based fermentation conditions for each strain.

[0052] Table 4 Orthogonal test factor level design during milk-based fermentation

[0053]

[0054] Scoring rules for the results of the orthogonal test during milk-based fermentation:

[0055] 1. Time score = 100 - n × 1.05 n

[0056] Taking 12 hours as a full score of 100 points, adding n 12-hour periods will deduct n × 1.05 n

[0057] 2. pH score = 100 - |pH - 3.7| × 2

[0058] 3. Titratable acidity score = 100 - |°T - 190| × 2

[0059] Total score = (time score + pH score + titratable acidity score) ÷ 3

[0060] Note:

[0061] The fermentation end point determination rule is pH 3.6 - 3.8 and titratable acidity 180°T - 200°T, and the longest fermentation time is 204 hours; for scores of individual items exceeding the standard, multiply by 0.95, and if the sample still does not reach the fermentation end point at 204 hours, multiply the total score by 0.95 again.

[0062] Table 5 Orthogonal test design table during milk-based fermentation

[0063]

[0064]

[0065] Table 6 Range analysis table of orthogonal test for the fermentation of milk beverage base by IMAU13187

[0066]

[0067] According to the above table and Figure 2 It shows that IMAU13187 has the best tolerance to different temperatures within the temperature range set in the experiment.

[0068] Example 4: Optimization Test Design of Stabilizer Formula for Probiotic Milk Beverage

[0069] Table 7 Factor-Level Design of Orthogonal Test for Milk Beverage Stability

[0070]

[0071]

[0072] Table 8 Orthogonal Test Design Table for Milk Beverage Stability

[0073]

[0074] After fully considering avoiding or reducing the negative factors that may be unfavorable to the stability of milk beverages in the experiment, such as the negative impacts of the addition amount of granulated sugar, water quality, and homogenization pressure, the milk beverage without stabilizer will quickly stratify and precipitate after being made, and it is not suitable for sale as a commodity. To solve this problem, it is considered to introduce a stabilizer into the milk beverage system. After verification, pectin, soybean polysaccharide, and sodium tripolyphosphate are selected as stabilizers and added to the beverage, and a three-factor and three-level orthogonal test is designed as shown in Table 7 and Table 8:

[0075] Scoring Rules for the Results of Orthogonal Test on Milk Beverage Stability:

[0076] Total Score = Sensory Score - TSI Overall

[0077] Note: The TSI overall value is the result measured by accelerating the aging of the beverage for one day at 37°C using Turbiscan.

[0078] According to the above analysis results, the optimal formula process for fermentation by three strains is determined as shown in Table 9:

[0079] Table 9 Optimal Condition Combinations for Milk-Based Fermentation

[0080]

[0081] Example 5: Fermentation Characteristics of Each Strain

[0082] 1. Analysis of the Characteristics of the Fermentation Substrate of Each Strain

[0083] In this experiment, the three strains were used to ferment the substrate according to the optimal conditions (Table 9) respectively, and the fermentation results of the substrate are as Figure 3 shown. Figure 3(a) shows the trend of the pH value of the bacterial liquid changing with the fermentation time. The results of one-way ANOVA indicate that there are significant differences in the fermentation rates of the three strains (p < 0.05). Among them, the fermentation time of IMAU99155 to the end point is 36 h, which is significantly faster than that of IMAU13187 (60 h) and LGG (60 h) strains (p < 0.05), while there is no significant difference in the fermentation time between IMAU13187 (60 h) and LGG (60 h) strains (p > 0.05). The results of the titratable acidity test are shown in Figure 3 (b). At the end of fermentation, the pH values and titratable acidities of the three strains are all in the central range of the indicators. The results of one-way ANOVA indicate that there is no significant difference in the titratable acidity among the strains (p > 0.05). Figure 3 (c) is a graph showing the trend of viable cell count changes. The viable cell counts of the three strains all increase with the increase of fermentation time. The viable cell counts at the end of fermentation are IMAU13187 (1.64×10 9 cfu / mL), IMAU99155 (1.68×10 9 cfu / mL), and LGG (1.68×10 9 cfu / mL) respectively. The results of one-way ANOVA indicate that there is no significant difference in the viable cell counts of the three strains (p > 0.05). At the end of fermentation, their respective optimized conditions are more suitable for the fermentation of milk-based substrates that meet the screening conditions by these three strains. Through the fermentation characteristics reflected by the three indicators of fermentation time and the changes of pH, titratable acidity and viable cell count during fermentation, the fermentation characteristics of IMAU13187 and LGG are closer.

[0084] 2. Determination of micro-rheological parameters during the fermentation of cow's milk

[0085] Use an optical micro-rheometer for monitoring. Take 20 mL of the inoculated substrate and place it in a special sample bottle, and then put it into the micro-rheological sample cell. Set the temperature to the fermentation temperature, and monitor the elastic factor, viscosity factor, solid-liquid equilibrium value and flow factor indicators during fermentation. Collect data every 5 s until the end of fermentation.

[0086] From Figure 4As can be seen from (a) and (b), the FI values and SLB values of IMAU13187 and LGG in the first 15 h and IMAU99155 in the first 10 h before fermentation were both in a fluctuating state. The SLB values were between 0.5 and 1, and the samples were closer to Newtonian fluids. Subsequently, the FI values and SLB values decreased rapidly, and the fermented milk base reached the gel point. Lactic acid bacteria fermented the milk base to produce acid, neutralizing the negative charges on the protein surface, causing the protein complex to form a gel under hydrophobic interactions. After gelation, the SLB value of LGG stabilized at about 0.3, being closer to a solid. The SLB value of IMAU13187 was the lowest, showing a weak gel structure and being closer to a liquid. The SLB value of IMAU99155 was between the two. The Macroscopic Viscosity Index (MVI) characterized the viscosity of the sample, and the Elastic Index (EI) characterized the elastic characteristics of the sample. From Figure 4 As can be seen from (c) and (d), the viscoelasticity of IMAU13187 and LGG in the first 15 h and IMAU99155 in the first 10 h before fermentation remained basically unchanged. Subsequently, the MVI value and EI value showed inflection points and increased rapidly, and the viscosity of the system also increased rapidly, which was the same as the change results shown by the SLB value and FI value. After gelation, the change trends of the elastic factors of the three samples were consistent with the performance of the solid-liquid equilibrium value. The overall results of micro-rheology showed that among the three strains, after fermentation, LGG was in a state of high elasticity and low viscosity, being closer to a solid; IMAU13187 was in a state of low elasticity and high viscosity, being closer to a liquid; and IMAU99155 was in a state of low elasticity and medium viscosity, being between the two.

[0087] 3. Changes in the viable count of brown fermented milk beverage during storage

[0088] The change trends of the viable count of milk beverages fermented by different strains at different temperatures during storage are as Figure 5 shown. At different storage temperatures, at the beginning (7 d), the viable counts of the three groups all increased slightly. This may be because new nutrients were introduced after adding granulated sugar, pectin, soy polysaccharide, and sodium tripolyphosphate to the system, and Lactobacillus rhamnosus GG obtained an environment for growth and reproduction again. However, the increase was very small at 4 °C and relatively large at 25 °C. At 4 °C, the viable counts of the three groups of beverages were relatively stable, and there was only a slight decrease at the end of storage. There was no significant difference among the groups. The total viable counts of the three groups at 28 days were IMAU13187: 1.9×10 8 CFU / mL, IMAU99155: 3.1×10 8 CFU / mL, and LGG: 3.8×10 8 CFU / mL. During storage at 25 °C, the viable counts of the three groups all increased slightly at 7 days, then remained stable until after 21 days and began to decline. Among them, the viable count of IMAU13187 decreased sharply at 28 days.

[0089] 4. Detection Results and Comparison of the Milk Base and Beverage of Brown Fermented Milk Beverage by Electronic Nose

[0090] Electronic nose technology is a food flavor detection device that simulates the human sense of smell. The sensors in the array sense different volatile flavor substances and generate different response signals, which are compared, judged, and identified with a large amount of flavor substance information in the database to obtain the overall information of the volatile flavor substances in the sample. At present, the research on electronic noses at home and abroad is very rich, and its application in dairy products is also very extensive.

[0091] The odors of the milk base and milk beverage samples in each group were analyzed and compared by an electronic nose, and the results are as Figure 6 shown. For the brown milk base, all ten receptors of the electronic nose changed. The changes of the three strains at the W5S receptor were significantly larger than those of other receptors, and the change amplitude of IMAU13187 was particularly obvious, nearly twice that of IMAU99155 and LGG. This receptor is sensitive to nitrogen oxides. The changes of IMAU13187 at the WlW receptor (sensitive to sulfides) and W2W (aromatic components, sensitive to organic sulfides) receptors were also larger than those of the other two strains. For the beverage, the changes of the three strains at the W5S receptor were also larger than those of other receptors, and the change amplitude of IMAU13187 was more obvious, but the difference was significantly smaller than that of the milk base, indicating that a large amount of this type of component was lost during the process from the milk base to the milk beverage for IMAU13187; the change amplitudes of IMAU13187 at the WlW receptor and W2W receptor in the beverage were slightly higher than those of the other two strains and were already very close, indicating that a part of the sulfide and organic sulfide aromatic components in the milk base of IMAU13187 were lost during the process of making the beverage. The electronic nose detected that the flavor substances produced by the milk base fermented with the strain IMAU13187 were generally richer.

[0092] For the same strain, during the process from the milk base to the beverage, the signals received by IMAU13187 at the W5S, WlW, and W2W receptors all decreased. The signal received by IMAU99155 only decreased at the W5S receptor, and the signals received by LGG decreased at the W1S and W2S receptors, corresponding to methyl substances and alcohol substances, aldehyde and ketone substances respectively. All three strains lost a part of the flavor substances during the process from the milk base to the beverage, but the types of changes were different.

[0093] 5. Determination of pH Value and Titratable Acidity

[0094] Determination of pH value: After the lactic acid bacteria beverage fermentation base material was placed at room temperature, it was measured with a precision pH meter (Leici PHS-3C), and continuous pH measurement was carried out with a multi-parameter pH meter (Mettler Toledo S400-B).

[0095] Determination of titratable acidity: The titratable acidity of milk beverages was detected by the "phenolphthalein indicator method" specified in the national standard GB5009.239-2016.

[0096] 6. KEGG annotation and enrichment analysis of differential metabolites

[0097] It can be seen from Figure 7 that the pathways with significant KEGG enrichment of differential metabolites in the IMAU13187 group by LGG are: ABC transporters, aminoacyl-tRNA biosynthesis, biosynthesis of amino acids, D-amino acid metabolism, 2-oxalate metabolism, nucleotide metabolism, dicarboxylic acid metabolism, carbon metabolism, two-component system, pyrimidine metabolism, citric acid cycle (TCA cycle), microbial metabolism in different environments, arginine biosynthesis, (alanine, aspartate and glutamate metabolism).

[0098] It can be seen from Figure 8 that the pathways with significant KEGG enrichment of differential metabolites in the IMAU99155 group by IMAU13187 are: two-component system (signal transduction system), purine metabolism, microbial metabolism in different environments, cyanide amino acid metabolism, arginine and proline metabolism, alanine, aspartate and glutamate metabolism, nucleotide metabolism, valine, leucine and isoleucine biosynthesis, galactose metabolism, 2-oxalate metabolism, biosynthesis of amino acids, D-amino acid metabolism, aminoacyl-tRNA biosynthesis and ABC transporters.

[0099] 6. Results of metabolic differences between fermented milks with different strains

[0100] Through metabolomics analysis of small molecule metabolites produced during the 1-day storage of milk beverages fermented with strains IMAU13187, IMAU99155 and LGG in this study, it was found that there were significant differences in the metabolite content and metabolic pathways in the milk beverages fermented by the LGG group, IMAU99155 group and IMAU13187 group.

[0101] The significantly enriched differential metabolic pathways in the LGG group and the IMAU13187 group mainly include: ABC transporters, aminoacyl-tRNA biosynthesis, biosynthesis of amino acids, D-amino acid metabolism, 2-oxalate metabolism, nucleotide metabolism, dicarboxylic acid metabolism, carbon metabolism, two-component system, pyrimidine metabolism, citric acid cycle (TCA cycle), microbial metabolism in different environments, arginine biosynthesis, alanine, aspartate and glutamate metabolism. These metabolic pathways have important functions in microbial metabolism. For example, amino acid metabolism can not only produce more nutrients but also form specific flavor substances under certain conditions. The differences in amino acid metabolism during fermentation by different strains will make the taste and flavor of milk beverages more diverse. In addition, the citric acid cycle (TCA cycle) is an important energy metabolism pathway during microbial fermentation. The differences in the metabolites of this pathway may affect the microbial fermentation rate, which may become one of the important bases for selecting strains in industrial fermentation. Combining the analysis of the differentially enriched metabolites in the LGG group and the IMAU13187 group, xanthine is one of the precursor substances of uric acid. An increase in the content of this metabolite in milk beverages may lead to an increase in the uric acid content of users; allopurinol can significantly inhibit the activity of xanthine oxidase and thus inhibit uric acid production. In addition, allopurinol also has the effect of preventing cerebral ischemia injury. Leu-Trp is a cyclic short peptide that can lower blood pressure and has antidepressant effects. A decrease in the content of Leu-Trp indicates that the milk beverage of the LGG group may have stronger blood pressure-lowering and antidepressant functions; wighteone is a furan flavonoid that has toxic effects on cancer cells. A decrease in the content of wighteone indicates that the milk beverage of the LGG group may have better anti-cancer effects; acetohexamide has the function of lowering blood sugar. A decrease in the content of acetohexamide may lead to a more significant blood sugar-lowering effect of the milk beverage of the LGG group. In summary, compared with the LGG group, the milk beverage fermented by the IMAU13187 group may have advantages in aspects such as broad-spectrum antiviral activity, anti-leukemia, prevention of cerebral ischemia injury, and inhibition of uric acid production.

[0102] Xanthine is one of the precursor substances of uric acid, and a decrease in its content reduces the probability of gout induced by uric acid; allopurinol is a xanthine oxidase inhibitor that has the effects of inhibiting uric acid production and preventing cerebral ischemia injury; ammonium glycyrrhizinate is a drug clinically used to treat immune-mediated liver injury. It is derived from glycyrrhizic acid, and a decrease in its content may weaken the efficacy of milk beverages in preventing liver injury; thiamine is an essential trace element in the human body, also known as vitamin B1, which is related to the occurrence of various human diseases such as Alzheimer's disease, dementia, and depression; D-proline is a common amino acid in the human body that has sedative and hypnotic effects. In summary, compared with the IMAU99155 group, the milk beverage fermented by the IMAU13187 group has better efficacy in treating liver injury, reducing uric acid, preventing brain injury, supplementing vitamins, enhancing sedation and hypnosis, etc.

Claims

1. A strain of Lactobacillus rhamnosus ( Lacticaseibacillus rhamnosus )IMAU13187, characterized in that The Lactobacillus rhamnosus IMAU13187 is preserved in China Center for Type Culture Collection, and its preservation number is CCTCC No.M2024949.

2. A method for preparing fermented milk, characterized in that: The preparation method comprises inoculating the Lactobacillus rhamnosus IMAU13187 described in claim 1 into raw milk for fermentation to obtain the fermented milk.

3. The preparation method according to claim 2, characterized in that: The raw milk includes cow's milk, goat's milk, horse's milk and / or camel's milk.

4. A fermented milk, characterized in that: The fermented milk is obtained by fermenting the Lactobacillus rhamnosus IMAU13187 according to claim 1, or is prepared by the preparation method according to claim 2.

5. Use of the Lactobacillus rhamnosus described in claim 1 in fermented dairy products.

6. The use according to claim 5, characterized in that The fermented milk includes fermented cow's milk, goat's milk, horse's milk and / or camel's milk.

7. Use of the Lactobacillus rhamnosus IMAU13187 according to claim 1 in the preparation of a product for lowering blood sugar.

8. Use of the Lactobacillus rhamnosus IMAU13187 according to claim 1 in the preparation of products for treating liver damage, reducing uric acid, preventing brain damage, supplementing vitamins, and enhancing calmness and hypnosis.

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