Streptococcus thermophilus and application thereof

Abstract

The invention relates to streptococcus thermophilus and application thereof, in particular to novel streptococcus thermophilus YSC1003 which has good fermentation performance and safety, and prepared fermented milk is short in fermentation time, large in viable count, high in viscosity and water-holding capacity and high in antioxidant activity. In addition, the invention also provides a compound strain containing the streptococcus thermophilus YSC1003, the compound strain has better fermentation performance and safety, and compared with a single strain, the fermentation time of the fermented milk prepared by the compound strain is obviously shortened, the viable count is obviously increased, and the fermentation time of the fermented milk prepared by the compound strain is obviously shortened under the condition of consistent bacterial quantity through strain interaction and synergistic interaction. The viscosity and the water-holding capacity are obviously improved, and the antioxidant activity is obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of microorganisms, and particularly to Streptococcus thermophilus and its applications. Background Art

[0002] Streptococcus thermophilus belongs to the genus Streptococcus, is facultatively anaerobic, sporeless, non-motile by flagella, homofermentative, and is a Gram-positive lactic acid bacterium. Its safety and effectiveness have been repeatedly certified, and it is a generally recognized as safe (GRAS) microorganism in the food field.

[0003] In recent years, with the rapid development of the probiotic industry in China, the demand for probiotics has been increasing day by day. However, currently, the largest proportion of domestic probiotic starters is from foreign companies, accounting for about 85% of the entire domestic probiotic starter market. This is related to the late start of China's lactic acid bacteria industry and the lack of self-owned strains with good fermentation performance. Further, fermented milk has a long history and is fermented by lactic acid bacteria, rich in various nutrients such as protein, minerals, and vitamins. The probiotic properties of fermented milk have also received extensive attention. For example, products with functions such as blood sugar lowering, blood lipid lowering, cholesterol lowering, and immune enhancement are made from it. With the improvement of people's pursuit of quality of life, fermented milk has received more and more attention from consumers. If single-strain or traditional lactic acid bacteria are used as starters to prepare fermented milk, there are usually problems such as too long fermentation time, slightly poor taste, and poor stability. Therefore, there is an urgent need to develop Streptococcus thermophilus strains or compound agents with good fermentation performance and stable production. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the inventors of the present application have conducted research and exploration, and provided a new Streptococcus thermophilus YSC1003, which has good fermentation performance and safety. The fermented milk prepared therefrom has a short fermentation time, a large number of viable bacteria, high viscosity and water holding capacity, and high antioxidant activity. In addition, the present application also provides a compound strain containing the aforementioned Streptococcus thermophilus YSC1003, which has good fermentation performance and safety. Through the interaction of the two strains, they synergistically enhance the effect. Under the same amount of bacteria, compared with a single strain, the fermented milk prepared from this compound strain has a significantly shorter fermentation time, a significantly increased number of viable bacteria, a significantly improved viscosity and water holding capacity, and a significantly enhanced antioxidant activity.

[0005] Specifically, in the first aspect of the present invention, the present invention provides Streptococcus thermophilus, which is deposited in the China General Microbiological Culture Collection Center, with the deposit number CGMCC No. 28253.

[0006] In a second aspect of the present invention, the present invention provides a composition comprising a first Streptococcus thermophilus, wherein the first Streptococcus thermophilus is as described in the first aspect.

[0007] In some embodiments, the composition further comprises a second Streptococcus thermophilus, which is deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the deposit number CGMCC No. 28251.

[0008] In some embodiments, in the composition, the viable cell number ratio of the first Streptococcus thermophilus to the second Streptococcus thermophilus is from 1:20 to 20:1, such as 1:20 - 1:15, 1:20 - 1:10, 1:20 - 1:5, 1:20 - 1:1, 1:20 - 5:1, 1:20 - 10:1, 1:20 - 15:1, 1:20 - 20:1, 1:15 - 1:10, 1:15 - 1:5, 1:15 - 1:1, 1:15 - 5:1, 1:15 - 10:1, 1:15 - 15:1, 1:15 - 20:1, 1:10 - 1:5, 1:10 - 1:1, 1:10 - 5:1, 1:10 - 10:1, 1:10 - 15:1, 1:10 - 20:1, 1:5 - 1:2, 1:5 - 1:1, 1:5 - 2:1, 1:5 - 5:1, 1:5 - 10:1, 1:5 - 15:1, 1:5 - 20:1, 1:2 - 1:1, 1:2 - 2:1, 1:2 - 5:1, 1:2 - 10:1, 1:2 - 15:1, 1:2 - 20:1, 1:1 - 2:1, 1:1 - 5:1, 1:1 - 10:1, 1:1 - 15:1, 1:1 - 20:1, 2:1 - 5:1, 2:1 - 10:1, 2:1 - 15:1, 2:1 - 20:1, 5:1 - 10:1, 5:1 - 15:1, 5:1 - 20:1, 10:1 - 15:1, 10:1 - 20:1 or 15:1 - 20:1.

[0009] In some embodiments, in the composition, the viable cell number ratio of the first Streptococcus thermophilus to the second Streptococcus thermophilus is from 1:2 to 2:1.

[0010] In some embodiments, in the composition, the viable cell number ratio of the first Streptococcus thermophilus to the second Streptococcus thermophilus is 1:1.

[0011] In some embodiments, the composition further comprises additional probiotic bacteria and / or probiotic fungi (such as yeast), wherein the additional probiotic bacteria and / or probiotic fungi are edible.

[0012] In some embodiments, the additional probiotic bacteria are selected from the genus Lactobacillus, the genus Casei, the genus Bifidobacterium, the genus Lactobacillus mucosae, the genus Lactobacillus plantarum subsp. plantarum, the genus Lactobacillus collinoides, the genus Lactobacillus paraplantarum, the genus Streptococcus, the genus Lactococcus, the genus Propionibacterium, the genus Propionibacteria, the genus Leuconostoc, the genus Pediococcus, the genus Weissella, the genus Carnobacterium, the genus Staphylococcus, the genus Bacillus, the genus Acetobacter, the genus Komagataeibacter, the genus Gluconacetobacter, the genus Gluconobacter, or any combination thereof.

[0013] In some embodiments, the bacteria of the genus Lactobacillus are selected from: Lactobacillus paracasei, Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus jensenii, Lactobacillus iners, Lactobacillus casei, Lactobacillus crispatus, Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillus fermentum, Lactobacillus gasseri, Lactobacillus helveticus, Lactobacillus johnsonii, Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus rhamnosus, Lactobacillus sakei, Lactobacillus salivarius, or any combination thereof.

[0014] In some embodiments, the bacteria of the genus Bifidobacterium are selected from: Bifidobacterium animalis, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium infantis, Bifidobacterium longum, Bifidobacterium adolescentis, or any combination thereof.

[0015] In some embodiments, the bacteria of the genus Bacillus are selected from: Bacillus subtilis, or any combination thereof.

[0016] In some embodiments, the bacteria of the genus Propionibacterium are selected from: Propionibacterium shermanii, Propionibacterium freudenreichii, Propionibacterium acidipropionici, or any combination thereof.

[0017] In some embodiments, the bacteria of the genus Streptococcus are selected from: Streptococcus thermophilus, Streptococcus salivarius, or any combination thereof.

[0018] In some embodiments, the bacteria of the genus Lactococcus is Lactococcus lactis.

[0019] In some embodiments, the yeast is selected from Brettanomyces anomalus, Saccharomyces cerevisiae, Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Zygosaccharomyces bailii, or any combination thereof.

[0020] In some embodiments, the composition further comprises additional additives or food excipients.

[0021] In some embodiments, the additional additive is a nutrient selected from dietary fiber, prebiotics, proteins, lipids, minerals, vitamins, plant extracts, or any combination thereof.

[0022] In some embodiments, the food excipient is selected from bleaching agents, preservatives, antioxidants, colorants, sweeteners, acidulants, flavor enhancers, color fixatives, or any combination thereof.

[0023] Those skilled in the art can select appropriate excipients and formulate them in combination with conventional technical means in the fields of microbial processes, pharmaceutical preparations, or food production and processing technologies (such as "Introduction to Food Production", "Encyclopedia of Food and Food Production", "Food Processing Technology", "Encyclopedia of Pharmaceutical Technology", "Pharmaceutical Dosage Form Technology", etc.) according to actual production needs, and can prepare the above-mentioned compositions of the present invention into various dosage form products that meet the requirements of process production. In some embodiments, the dosage forms of the composition are selected from powder, tablet, liquid, pill, capsule, granule, film coating agent, sachet, and sugar-coated pill.

[0024] In the third aspect of the present invention, the present invention provides a compound bacterial powder, which comprises a first Streptococcus thermophilus bacterial powder and a second Streptococcus thermophilus bacterial powder. The first Streptococcus thermophilus is as described in the first aspect, and the second Streptococcus thermophilus is deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the deposit number CGMCC No. 28251.

[0025] In some embodiments, the ratio of the viable count of the first Streptococcus thermophilus bacterial powder to the second Streptococcus thermophilus bacterial powder is 1:20 - 20:1, such as 1:20 - 1:15, 1:20 - 1:10, 1:20 - 1:5, 1:20 - 1:1, 1:20 - 5:1, 1:20 - 10:1, 1:20 - 15:1, 1:20 - 20:1, 1:15 - 1:10, 1:15 - 1:5, 1:15 - 1:1, 1:15 - 5:1, 1:15 - 10:1, 1:15 - 15:1, 1:15 - 20:1, 1:10 - 1:5, 1:10 - 1:1, 1:10 - 5:1, 1:10 - 10:1, 1:10 - 15:1, 1:10 - 20:1, 1:5 - 1:2, 1:5 - 1:1, 1:5 - 2:1, 1:5 - 5:1, 1:5 - 10:1, 1:5 - 15:1, 1:5 - 20:1, 1:2 - 1:1, 1:2 - 2:1, 1:2 - 5:1, 1:2 - 10:1, 1:2 - 15:1, 1:2 - 20:1, 1:1 - 2:1, 1:1 - 5:1, 1:1 - 10:1, 1:1 - 15:1, 1:1 - 20:1, 2:1 - 5:1, 2:1 - 10:1, 2:1 - 15:1, 2:1 - 20:1, 5:1 - 10:1, 5:1 - 15:1, 5:1 - 20:1, 10:1 - 15:1, 10:1 - 20:1 or 15:1 - 20:1.

[0026] In some embodiments, the ratio of the viable count of the first Streptococcus thermophilus bacterial powder to the second Streptococcus thermophilus bacterial powder is 1:2 - 2:1.

[0027] In some embodiments, the ratio of the viable cell count of the first Streptococcus thermophilus bacterial powder to that of the second Streptococcus thermophilus bacterial powder is 1:1.

[0028] In some embodiments, the viable cell count of the first Streptococcus thermophilus bacterial powder or the second Streptococcus thermophilus bacterial powder is 1×10 9 CFU / g to 1×10 11 CFU / g, such as 1×10 9 CFU / g to 3×10 9 CFU / g, 1×10 9 CFU / g to 5×10 9 CFU / g, 1×10 9 CFU / g to 7×10 9 CFU / g, 1×10 9 CFU / g to 9×10 9 CFU / g, 1×10 9 CFU / g to 1×10 10 CFU / g, 3×10 9 CFU / g to 5×10 9 CFU / g, 3×10 9 CFU / g to 7×10 9 CFU / g, 3×10 9 CFU / g to 9×10 9 CFU / g, 3×10 9 CFU / g to 1×10 10 CFU / g, 5×10 9 CFU / g to 7×10 9 CFU / g, 5×10 9 CFU / g to 9×10 9 CFU / g, 5×10 9 CFU / g to 1×10 10 CFU / g, 9×10 9 CFU / g to 1×10 10 CFU / g, 1×10 10 CFU / g to 3×10 10 CFU / g, 1×10 10 CFU / g to 5×10 10 CFU / g, 1×10 10 CFU / g to 7×10 10 CFU / g, 1×10 10 CFU / g to 9×10 10 CFU / g, 1×10 10 CFU / g to 1×10 11 CFU / g, 3×10 10CFU / g to 5×10 10 CFU / g, 3×10 10 CFU / g to 7×10 10 CFU / g, 3×10 10 CFU / g to 9×10 10 CFU / g, 3×10 10 CFU / g to 1×10 11 CFU / g, 5×10 10 CFU / g to 7×10 10 CFU / g, 5×10 10 CFU / g to 9×10 10 CFU / g, 5×10 10 CFU / g to 1×10 11 CFU / g, 9×10 10 CFU / g to 1×10 11 CFU / g, or such as 1×10 9 CFU / g, 2×10 9 CFU / g, 3×10 9 CFU / g, 4×10 9 CFU / g, 5×10 9 CFU / g, 6×10 9 CFU / g, 7×10 9 CFU / g, 8×10 9 CFU / g, 9×10 9 CFU / g, 1×10 10 CFU / g, 2×10 10 CFU / g, 3×10 10 CFU / g, 4×10 10 CFU / g, 5×10 10 CFU / g, 6×10 10 CFU / g, 7×10 10 CFU / g, 8×10 10 CFU / g, 9×10 10 CFU / g or 1×10 11 CFU / g.

[0029] In some embodiments, the viable count of the first Streptococcus thermophilus powder or the second Streptococcus thermophilus powder is 10 10 CFU / g.

[0030] In some embodiments, the first Streptococcus thermophilus powder or the second Streptococcus thermophilus powder is obtained by freeze-drying the first Streptococcus thermophilus bacterial liquid or the second Streptococcus thermophilus bacterial liquid.

[0031] In some embodiments, the viable cell counts of the first Streptococcus thermophilus bacterial solution and the second Streptococcus thermophilus bacterial solution are equal.

[0032] In some embodiments, the viable cell count of the first Streptococcus thermophilus bacterial solution or the second Streptococcus thermophilus bacterial solution is 1×10 9 CFU / mL to 1×10 11 CFU / mL, such as 1×10 9 CFU / mL to 3×10 9 CFU / mL, 1×10 9 CFU / mL to 5×10 9 CFU / mL, 1×10 9 CFU / mL to 7×10 9 CFU / mL, 1×10 9 CFU / mL to 9×10 9 CFU / mL, 1×10 9 CFU / mL to 1×10 10 CFU / mL, 3×10 9 CFU / mL to 5×10 9 CFU / mL, 3×10 9 CFU / mL to 7×10 9 CFU / mL, 3×10 9 CFU / mL to 9×10 9 CFU / mL, 3×10 9 CFU / mL to 1×10 10 CFU / mL, 5×10 9 CFU / mL to 7×10 9 CFU / mL, 5×10 9 CFU / mL to 9×10 9 CFU / mL, 5×10 9 CFU / mL to 1×10 10 CFU / mL, 9×10 9 CFU / mL to 1×10 10 CFU / mL, 1×10 10 CFU / mL to 3×10 10 CFU / mL, 1×10 10 CFU / mL to 5×10 10 CFU / mL, 1×10 10 CFU / mL to 7×10 10 CFU / mL, 1×10 10 CFU / mL to 9×10 10 CFU / mL, 1×10 10 CFU / mL to 1×1011 CFU / mL, 3×10 10 CFU / mL to 5×10 10 CFU / mL, 3×10 10 CFU / mL to 7×10 10 CFU / mL, 3×10 10 CFU / mL to 9×10 10 CFU / mL, 3×10 10 CFU / mL to 1×10 11 CFU / mL, 5×10 10 CFU / mL to 7×10 10 CFU / mL, 5×10 10 CFU / mL to 9×10 10 CFU / mL, 5×10 10 CFU / mL to 1×10 11 CFU / mL, 9×10 10 CFU / mL to 1×10 11 CFU / mL, or such as 1×10 9 CFU / mL, 2×10 9 CFU / mL, 3×10 9 CFU / mL, 4×10 9 CFU / mL, 5×10 9 CFU / mL, 6×10 9 CFU / mL, 7×10 9 CFU / mL, 8×10 9 CFU / mL, 9×10 9 CFU / mL, 1×10 10 CFU / mL, 2×10 10 CFU / mL, 3×10 10 CFU / mL, 4×10 10 CFU / mL, 5×10 10 CFU / mL, 6×10 10 CFU / mL, 7×10 10 CFU / mL, 8×10 10 CFU / mL, 9×10 10 CFU / mL or 1×10 11 CFU / mL.

[0033] In some embodiments, the viable count of the first Streptococcus thermophilus bacterial solution or the second Streptococcus thermophilus bacterial solution is 10 10 CFU / mL.

[0034] In some embodiments, the first Streptococcus thermophilus bacterial solution and the second Streptococcus thermophilus bacterial solution are obtained by the following method: The first Streptococcus thermophilus and the second Streptococcus thermophilus are separately activated and inoculated into M17 broth medium at an inoculation amount of 5%, and after being cultured at 37°C for 48 h with expansion, the first Streptococcus thermophilus bacterial solution and the second Streptococcus thermophilus bacterial solution are obtained respectively.

[0035] In some embodiments, the components and ratios (g\L) of the M17 broth medium are as follows: soy peptone 5.0 g\L; peptone 2.5 g\L; casein peptone 2.5 g\L; yeast extract powder 2.5 g\L; beef extract powder 5.0 g\L; lactose 5.0 g\L; sodium ascorbate 0.5 g\L; β-glycerophosphate 19.0 g\L; magnesium sulfate 0.25 g\L; pH value at 25°C is 7.2 ± 0.2, and the solvent is water.

[0036] In some embodiments, the first Streptococcus thermophilus bacterial powder or the second Streptococcus thermophilus bacterial powder is obtained by successively performing centrifugation, homogenization, and freeze-drying steps on the first Streptococcus thermophilus bacterial solution or the second Streptococcus thermophilus bacterial solution respectively.

[0037] In some embodiments, after centrifugation, the first Streptococcus thermophilus bacterial sludge or the second Streptococcus thermophilus bacterial sludge is taken for the homogenization step.

[0038] In some embodiments, the homogenization is carried out in the presence of a freeze-drying protectant.

[0039] In some embodiments, after homogenization and before freeze-drying, a pre-freezing step is further included.

[0040] In some embodiments, the time for freeze-drying is 24 h.

[0041] In some embodiments, the pre-freezing is carried out at -80°C for 24 h.

[0042] In some embodiments, the mass ratio of the first Streptococcus thermophilus bacterial sludge or the second Streptococcus thermophilus bacterial sludge to the freeze-drying protectant is (1 - 1.5):(3.5 - 4.5), such as 1:3.5 - 1:4, 1:3.5 - 1:4.5, 1:4 - 1:4.5, 1.5:3.5 - 1.5:4, 1.5:3.5 - 1.5:4.5, or 1.5:4 - 1.5:4.5, or such as 1:3.5, 1:4, 1:4.5, 1.5:3.5, 1.5:4, or 1.5:4.5.

[0043] In some embodiments, the mass ratio of the first Streptococcus thermophilus bacterial sludge or the second Streptococcus thermophilus bacterial sludge to the freeze-drying protectant is 1:4.

[0044] In some embodiments, the cryoprotectant comprises skim milk powder, trehalose, maltodextrin, sodium glutamate, and water.

[0045] In some embodiments, the mass ratio of the skim milk powder, trehalose, maltodextrin, sodium glutamate, and water is: skim milk powder: trehalose: maltodextrin: sodium glutamate: water = 5:4:2:2:37.

[0046] In some embodiments, the first Streptococcus thermophilus powder or the second Streptococcus thermophilus powder (by mass ratio) comprises: Streptococcus thermophilus cells of the first or second type: skim milk powder: trehalose: maltodextrin: sodium glutamate = 1:20:16:8:8.

[0047] In a fourth aspect of the present invention, the present invention provides a food, health product, or drug, which comprises the Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect.

[0048] In some embodiments, the food is selected from fermented dairy products, fermented soy products, fermented fruit and vegetable products, fermented meat products, fermented beverages, probiotic starters, and probiotic solid beverages.

[0049] In some embodiments, the fermented dairy products are selected from fermented milk, yogurt (such as ambient temperature yogurt, low temperature yogurt, stirred yogurt, set yogurt, or drinking yogurt), kefir, fermented buttermilk, yogurt wine, milk wine, cheese, and lactic acid bacteria beverages.

[0050] In some embodiments, the food, health product, or drug further comprises prebiotics.

[0051] In a fifth aspect of the present invention, the present invention provides a fermented dairy product, which is fermented using the Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect.

[0052] In some embodiments, the fermentation medium is a skim milk powder medium, and the skim milk powder medium comprises skim milk powder, sucrose, inulin, and water.

[0053] In some embodiments, in the skim milk powder medium, the mass ratio of the skim milk powder to the sucrose is (11 - 12):(7 - 8), such as 11:7, 11:7.5, 11:8, 12:7, 12:7.5, or 12:8.

[0054] In some embodiments, in the skim milk powder medium, the mass ratio of the skim milk powder to the inulin is (11 to 12):(3.5 to 4.5), such as 11:3.5, 11:4, 11:4.5, 12:3.5, 12:4 or 12:4.5.

[0055] In some embodiments, the fermented dairy product is selected from fermented milk, yogurt (such as ambient temperature yogurt, low temperature yogurt, stirred yogurt, set yogurt or drinking yogurt), kefir, fermented buttermilk, yogurt wine, milk wine, cheese, lactic acid bacteria beverage.

[0056] In some embodiments, the fermented dairy product is fermented milk.

[0057] In some embodiments, the skim milk powder medium is prepared by the following method:

[0058] 1) Ultrasonically treat and sterilize an aqueous solution of the skim milk powder;

[0059] 2) Mix and homogenize the solution obtained in step 2) with the inulin and the sucrose to obtain the skim milk powder medium.

[0060] In some embodiments, the ultrasonic treatment is carried out at a power of 550 to 600 W (such as 550 to 560 W, 550 to 570 W, 550 to 580 W, 550 to 590 W, 550 to 600 W, 560 to 570 W, 560 to 580 W, 560 to 590 W, 560 to 600 W, 570 to 580 W, 570 to 590 W, 570 to 600 W, 580 to 590 W, 580 to 600 W or 590 to 600 W, or such as 550 W, 560 W, 570 W, 580 W, 590 W or 600 W), for a time of 15 to 20 min (such as 15 to 16 min, 15 to 17 min, 15 to 18 min, 15 to 19 min, 15 to 20 min, 16 to 17 min, 16 to 18 min, 16 to 19 min, 16 to 20 min, 17 to 18 min, 17 to 19 min, 17 to 20 min, 18 to 19 min, 18 to 20 min, 19 to 20 min, or such as 15 min, 16 min, 17 min, 18 min, 19 min or 20 min), with an intermittent ratio of 1:1.

[0061] In some embodiments, the mixing and homogenization are carried out at a temperature of 40°C to 60°C (such as 40°C, 45°C, 50°C, 55°C or 60°C).

[0062] In some embodiments, the sterilization conditions are 105°C for 15 min.

[0063] In some embodiments, the fermented dairy product is obtained by inoculating Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect into a skim milk powder medium for fermentation.

[0064] In some embodiments, the inoculation amount of Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect is 10 6 CFU / g to 10 8 CFU / g, preferably 10 7 CFU / g.

[0065] In some embodiments, the temperature of the skim milk powder medium during inoculation is 40°C to 60°C (such as 40°C, 45°C, 50°C, 55°C or 60°C).

[0066] In some embodiments, after inoculation and before fermentation, a homogenization step is further included.

[0067] In some embodiments, the fermentation is carried out in a 37°C incubator.

[0068] In some embodiments, when the pH value of the fermented dairy product reaches 4.5, the fermentation ends.

[0069] In the sixth aspect of the present invention, the present invention provides the use of Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect in the preparation of health products, and the health products have one or more of the uses selected from the following a)-g):

[0070] a) Contributing to antioxidant; b) Contributing to maintaining a healthy blood glucose level; c) Contributing to maintaining a healthy blood lipid (cholesterol / triglyceride) level; d) Contributing to enhancing immunity; e) Contributing to regulating the intestinal flora; f) Contributing to digestion; g) Contributing to laxation.

[0071] Meanwhile, the present invention also provides Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect, which has one or more of the uses selected from the following a)-g):

[0072] a) Contributing to antioxidant; b) Contributing to maintaining a healthy blood glucose level; c) Contributing to maintaining a healthy blood lipid (cholesterol / triglyceride) level; d) Contributing to enhancing immunity; e) Contributing to regulating the intestinal flora; f) Contributing to digestion; g) Contributing to laxation.

[0073] In addition, the present invention also provides one or more methods selected from the following a)-g), which include administering an effective amount of Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect to a subject in need;

[0074] a) Antioxidant method; b) Method for maintaining a healthy blood glucose level; c) Method for maintaining a healthy blood lipid (cholesterol / triglyceride) level; d) Method for enhancing immunity; e) Method for regulating intestinal flora; f) Method for promoting digestion; g) Method for moistening the intestine and relieving constipation.

[0075] In the seventh aspect of the present invention, the present invention provides the use of Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect in the preparation of a drug for one or more selected from the following A)-I):

[0076] A) Antioxidation; B) Anti-aging; C) Lowering blood glucose; D) Lowering blood lipids; E) Lowering cholesterol; F) Enhancing immunity; G) Regulating intestinal flora; H) Promoting digestion; I) Moistening the intestine and relieving constipation.

[0077] Meanwhile, the present invention also provides Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect for one or more selected from the following A)-I):

[0078] A) Antioxidation; B) Anti-aging; C) Lowering blood glucose; D) Lowering blood lipids; E) Lowering cholesterol; F) Enhancing immunity; G) Regulating intestinal flora; H) Promoting digestion; I) Moistening the intestine and relieving constipation.

[0079] In addition, the present invention also provides one or more methods selected from the following A)-I), which include: administering an effective amount of Streptococcus thermophilus described in any technical solution of the first aspect, or the composition described in any technical solution of the second aspect, or the compound bacterial powder described in any technical solution of the third aspect to a subject in need;

[0080] A) Antioxidant method; B) Anti-aging method; C) Lowering blood glucose method; D) Lowering blood lipids method; E) Lowering cholesterol method; F) Method for enhancing immunity; G) Method for regulating intestinal flora; H) Method for promoting digestion; I) Method for moistening the intestine and relieving constipation.

[0081] In the present invention, the terms "first" and "second" are only used for descriptive purposes for easy distinction and cannot be construed as indicating or implying relative importance.

[0082] In the present invention, a "subject" refers to a vertebrate. In certain embodiments, the vertebrate refers to a mammal. Mammals include, but are not limited to, livestock (such as cattle), pets (such as cats, dogs, and horses), primates, mice, and rats. In certain embodiments, the mammal refers to a human.

[0083] In the present invention, the term "effective amount" refers to an amount sufficient to obtain or at least partially obtain the desired effect. Determining such an effective amount is entirely within the ability of those skilled in the art and depends specifically on the severity of the disease to be treated, the overall status of the patient's own immune system, the general condition of the patient such as age, weight, and gender, the mode of administration of the drug, and other treatments administered simultaneously, etc. It is further understood that for any specific individual,

[0084] In the present invention, the endpoints and any values of the disclosed ranges are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0085] Sequence Information

[0086] Information on the partial sequences related to this application is provided in Table 1 below.

[0087] Table 1: Description of Sequences

[0088]

[0089]

[0090] Biological Deposit

[0091] The Streptococcus thermophilus YSC1001 provided by the present invention was deposited with the General Microbiological Center of the China Committee for Culture Collection of Microorganisms on August 25, 2023, with the deposit number CGMCC No. 28251 and the deposit address being No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences (abbreviated as CGMCC).

[0092] The Streptococcus thermophilus YSC1003 provided by the present invention is deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms. The deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The deposit number is CGMCC No. 28253, and the deposit date is August 23, 2023.

[0093] Advantageous Effects of the Invention

[0094] 1. The present invention provides a new Streptococcus thermophilus YSC1003, which has good fermentation performance and safety. The fermented milk prepared has a short fermentation time, a large number of viable bacteria, high viscosity and water holding capacity, and high antioxidant activity. It can be seen that the new Streptococcus thermophilus of the present invention has great application prospects in the future fermentation market.

[0095] 2. The present invention provides a compound strain, which has good fermentation performance and safety. Through the interaction of the two strains, the compound strain has a synergistic effect. When the amount of bacteria is the same, compared with a single strain, the fermented milk prepared by the compound strain has a significantly shorter fermentation time, a significantly larger number of viable bacteria, significantly higher viscosity and water holding capacity, and significantly improved antioxidant activity. It can be seen that the compound Streptococcus thermophilus of the present invention has great application prospects in the future fermentation market.

[0096] 3. When using the strain or compound strain of the present invention to prepare fermented milk, the skim milk powder in the culture medium is treated by ultrasonic wave, which can effectively improve the fermentation characteristics of the fermented milk and enhance the antioxidant activity of the fermented milk of Streptococcus thermophilus.

[0097] 4. When using the strain or compound strain of the present invention to prepare fermented milk, adding prebiotic inulin to the culture medium can effectively improve the fermentation characteristics of the fermented milk and enhance the antioxidant activity of the fermented milk of Streptococcus thermophilus. Description of the Drawings

[0098] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention in combination with the drawings, where

[0099] Figure 1 Screening strains with better taste for small cup milk fermentation by Streptococcus thermophilus.

[0100] Figure 2 Verification of large cup milk fermentation experiment by Streptococcus thermophilus.

[0101] Figure 3 Colony morphology of Streptococcus thermophilus YSC1001 in MRS medium.

[0102] Figure 4 It is the stained morphology of Streptococcus thermophilus YSC1001 under an electron microscope.

[0103] Figure 5 It is the phylogenetic tree of Streptococcus thermophilus YSC1001 based on the 16S rRNA gene sequence.

[0104] Figure 6 It is the carbon source utilization analysis of Streptococcus thermophilus YSC1001.

[0105] Figure 7 It is the growth curve and acid production curve of Streptococcus thermophilus YSC1001.

[0106] Figure 8 It is the antibiotic sensitivity analysis of Streptococcus thermophilus YSC1001 strain.

[0107] Figure 9 It is the map of different morphological colonies in the petri dish of -7 gradient of the present invention.

[0108] Figure 10 It is the DPPH free radical scavenging rate map of the fermented milk of the present invention.

[0109] Figure 11 It is the hydroxyl free radical scavenging rate map of the fermented milk of the present invention.

[0110] Figure 12 It is the ABTS + free radical scavenging rate map of the fermented milk of the present invention. Detailed implementation manners

[0111] The present invention will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and should not be regarded as limiting the present invention. The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0112] In the following embodiments, the composition and ratio (g\L) of the M17 agar medium: soybean peptone 5.0 g\L; peptone 2.5 g\L; casein peptone 2.5 g\L; yeast extract powder 2.5 g\L; beef extract powder 5.0 g\L; lactose 5.0 g\L; sodium ascorbate 0.5 g\L; β-glycerophosphate 19.0 g\L; magnesium sulfate 0.25 g\L; agar 12.75 g\L; pH value 7.2 ± 0.2 at 25°C, and the solvent is water.

[0113] In the following examples, the composition and ratio (g / L) of M17 broth medium are as follows: soy peptone 5.0 g / L; peptone 2.5 g / L; casein peptone 2.5 g / L; yeast extract powder 2.5 g / L; beef extract powder 5.0 g / L; lactose 5.0 g / L; sodium ascorbate 0.5 g / L; β-glycerophosphate sodium 19.0 g / L; magnesium sulfate 0.25 g / L; pH value 7.2 ± 0.2 at 25 °C, and the solvent is water.

[0114] Example 1: Isolation, Screening and Identification of Streptococcus thermophilus Strain YSC1001

[0115] 1. Isolation and screening of Streptococcus thermophilus strains

[0116] Absorb 1 mL of the sample solution from the ethnic characteristic dairy products in rural households in Aba Prefecture, Sichuan Province, and use 0.85% sterile physiological saline to dilute it successively to 10 -3 ,10 -4 ,10 -5 times. Then take 0.1 mL of each dilution and spread it on the plate of MRS solid medium (repeat three times). After the dilution solution is absorbed by the plate, incubate it upside down at 37 °C for 36 - 48 h. Use a sterilized inoculation tube to pick different morphological single colonies and inoculate them into MRS / ST solid medium, and repeat the streak isolation and purification until the colony morphology is completely consistent. Finally, pick a single colony and inoculate it into 5 mL of MRS liquid medium, incubate it at 37 °C for 24 h to obtain a single-strain lactic acid bacteria culture solution, and store it at -80 °C with 50% (v / v) glycerol.

[0117] 2. Identification of the species to which the isolated strains belong

[0118] Extraction of bacterial genomic DNA: Use the SteadyPure bacterial genomic DNA extraction kit. PCR amplification of 16S rRNA sequence: Amplify the 16S rRNA gene sequence, and use the universal primers 27F (SEQ ID NO: 2) and 1492R (SEQ ID NO: 3) as the upstream and downstream primers. PCR amplification program: Pre-denature at 94 °C for 3 min. Then denature at 98 °C for 10 S, anneal at 55 °C for 30 S, extend at 72 °C for 60 S, for a total of 34 cycles. Finally, fully extend at 72 °C for 2 min and store at 4 °C. Detection and sequencing analysis of PCR products: Take 2.5 μL of the PCR product, add it to 1% agarose for gel electrophoresis separation and inspection. The amplified target fragment is about 1500 bp long. Entrust the product containing the target fragment to Shanghai Bioengineering Co., Ltd. to complete the sequencing, and the obtained 16S rRNA sequence is as shown in SEQ ID NO: 1. According to the 16S rRNA gene sequencing results, use NCBI GenBank BALST alignment to preliminarily determine the species, and obtain 23 strains of Streptococcus thermophilus.

[0119] Example 2: Taste Analysis of Fermented Yogurt with Streptococcus thermophilus Strain YSC1001

[0120] The isolated Streptococcus thermophilus was used for milk fermentation and sensory evaluation. First, the strain was activated. The bacterial liquid was pipetted from the glycerol tube and streaked on an MRS plate, and then cultured at 37 °C for 48 h. A single colony was picked and inoculated into 5 mL of liquid medium and cultured at 37 °C for 18 h. A single colony was picked and transferred to liquid, and inoculated into the liquid medium at an inoculation amount of 2% and cultured at 37 °C for 18 h. Then, the milk was sterilized and cooled. Whole-fat pure milk was heated at 95 °C for 15 min for sterilization, and then cooled to 43 °C for standby. Before inoculation, the Streptococcus thermophilus bacterial liquid was centrifuged at 8000 rpm for 3 min, and then the supernatant was removed. Sterile water was added for resuspension and washing, and then shaken and mixed on a vortex mixer. The centrifugation step was repeated once to remove the supernatant, and the bacterial precipitate was retained for inoculation and fermentation. The bacterial precipitate was mixed with sterile milk (43 °C), and statically fermented at 43 °C for 4 - 8 h. The fermented milk was ripened. After the milk coagulated, it was placed in a 4 °C refrigerator overnight (for more than 10 h).

[0121] According to the sensory evaluation standard of fermented milk in GB19302 - 2010, the evaluation was carried out according to six items: curd grade, whey separation, sour taste, milk fat flavor, fresh flavor, and hardness. The score of each item was between 0 and 5, and the higher the number, the better the effect of the strain in fermenting milk in this item.

[0122] The above method was used to conduct a small - cup (40 mL milk) fermentation experiment on 23 strains of Streptococcus thermophilus. Yogurts fermented by 17 strains of Streptococcus thermophilus with certain curdling ability within 8 h were preliminarily screened for sensory evaluation ( Figure 1 , Table 2).

[0123] Table 2 Streptococcus thermophilus strains with good sensory evaluation after small - cup (40 mL) fermented milk screening

[0124]

[0125]

[0126] By comparison, strains with strong curdling ability, less whey separation, moderate sour taste, higher hardness, and strong milk fat flavor were screened out. According to the comprehensive score, Streptococcus thermophilus strain YSC1001 was selected, and a large - cup (800 mL milk) fermentation experiment and sensory evaluation were carried out for verification ( Figure 2 , Table 3). Through the large - cup fermentation experiment, it was confirmed that the comprehensive sensory evaluation of Streptococcus thermophilus YSC1001 was the best.

[0127] Table 3 Re - screening of sensory evaluation of Streptococcus thermophilus YSC1001 after large - cup (800 mL) fermented milk

[0128]

[0129] Example 3: Source and Identification of Streptococcus thermophilus YSC1001

[0130] Streptococcus thermophilus YSC1001 comes from the ethnic characteristic milk residue dairy product, which is fermented from cow's milk and was collected from farmers in Kanglong Village, Shangrangtang Township, Rongtang County, Aba Prefecture in 2022.

[0131] The thermophilic Streptococcus YSC1001 was isolated from the milk pimple sample using MRS medium. The surface colonies were about 2 mm in diameter, convex, round, smooth, dense, and dark yellow ( Figure 3 ), the bacteria are spherical ( Figure 4 ). The phylogenetic tree based on 16S rRNA showed that Streptococcus thermophilus YSC1001 formed a monophyletic branch with Streptococcus thermophilus ( Figure 5 ), and was therefore identified as Streptococcus thermophilus.

[0132] Example 4: Analysis of Fermentation Carbon Source Utilization of Streptococcus thermophilus YSC1001

[0133] API CHL 50 reagent was used to conduct a carbon source characteristic experiment on Streptococcus thermophilus YSC1001. A total of 49 carbon source utilization experiments were conducted, including glycerol, erythritol, D-arabinose, L-arabinose, D-ribose, D-xylose, L-xylose, D-ribitol, methyl-β-D-pyranose, D-galactose, D-glucose, D-fructose, D-mannitol, L-sorbose, L-rhamnose, d-mannitol, inositol, mannitol, sorbitol, methyl-α-D-pyranose, methyl-α-D-pyranose Glucoside, N-acetylglucosamine, amygdalin, arbutin, esculin ferric citrate, salicin, D-cellobiose, D-maltose, D-lactose, D-melibiose, D-sucrose, D-trehalose, inulin, D-melezitose, D-raffinose, starch, glycogen, xylitol, 3-ketogluconate potassium, D-toluentan, D-lyxose, D-tagatose, D-fucose, L-fucose, D-arabinose, L-arabinose, potassium gluconate, 2-ketogluconate potassium and 5-ketogluconate potassium.

[0134] The experimental results showed that YSC1001 could only utilize four carbon sources, namely D-glucose, ferric citrate, D-lactose and D-sucrose ( Figure 6 ), among which glucose, lactose and sucrose are all easily available carbon sources, which are beneficial for the subsequent large-scale production of YSC1001.

[0135] Example 5: Analysis of Growth and Acid Production Characteristics of Streptococcus thermophilus YSC1001

[0136] Streptococcus thermophilus YSC1001 preserved with 50% glycerol was inoculated on MRS solid medium and cultured at 37°C for 36 h. A single colony was picked with an inoculation loop and transferred to 3 mL of liquid medium, followed by culturing at 37°C for 18 h to prepare a stock culture for later use. The prepared stock culture was inoculated into 8 mL of MRS liquid medium at an inoculation amount of 2%, and cultured at 37°C. The OD value and pH value were measured every 2 h from the beginning of the culture until 24 h, and the growth curve and acid production curve were plotted.

[0137] The results showed ( Figure 7 ), the lag phase of Streptococcus thermophilus was 2 h, the logarithmic growth phase was from 4 - 10 h, and the stationary phase started after 12 h; after 6 h of fermentation, the pH was close to 4.5.

[0138] Example 6: Antibiotic Sensitivity Analysis of Streptococcus thermophilus YSC1001

[0139] For microorganisms or products applied in the food field, higher safety requirements are imposed. On the one hand, lactic acid bacteria are required to be edible, and on the other hand, they are expected to be sensitive to antibiotics to prevent the impact of the carriage of drug resistance genes and their horizontal transfer on human health.

[0140] Streptococcus thermophilus YSC1001 is an edible lactic acid bacterium. To further analyze its sensitivity to antibiotics, OXOID antibiotic susceptibility discs were used, and the Kirby - Bauer method (K - B method) was adopted to conduct a 6 - antibiotic susceptibility test on the strain. The sensitivities of Streptococcus thermophilus YSC1001 to tetracycline TE 30 mcg, ampicillin AMP 10 mcg, chloramphenicol C 30 μg, penicillin P 10 IU, streptomycin S 10 μg, and erythromycin E 15 μg were analyzed. The target strain was cultured in MRS liquid medium to a 0.5 McFarland turbidity, spread on the surface of the plate, and the antibiotic susceptibility discs were placed on the plate within 15 min after inoculation. Then it was cultured in an inverted position in a 37°C incubator for 18 - 24 h, and the diameter of the complete inhibition zone was measured after culturing.

[0141] The results showed ( Figure 8 , Table 4), the diameters of the inhibition zones of Streptococcus thermophilus YSC1001 were relatively large in tetracycline, erythromycin, chloramphenicol, and ampicillin, and it was sensitive to these 5 antibiotics, with only a certain tolerance to streptomycin. Therefore, the possibility of Streptococcus thermophilus YSC1001 carrying drug resistance genes is low, and it is a relatively safe biological strain.

[0142] Table 4 Analysis of the sensitivity of Streptococcus thermophilus YSC1001 to antibiotics

[0143]

[0144] Example 7: Isolation and Identification of Streptococcus thermophilus Strain YSC1003

[0145] The Streptococcus thermophilus was isolated from Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province. The isolation method includes the following steps:

[0146] 25 g (±0.1 g) of fermented dairy products stored at 4°C and transported at low temperature by laboratory personnel were placed into 225 mL of sterilized physiological saline. After being thoroughly mixed by an oscillator, 1 mL was taken as the -1 gradient in a sterile environment, and 9 mL of sterilized physiological saline was added for 10-fold dilution. The above dilution operation was repeated 7 times to obtain the -7 gradient. The -7 gradient was selected as the colony counting petri dish gradient. 1 mL of the -7 gradient dilution was added to several petri dishes for parallel tests, and 20 mL of M17 agar medium at 50°C was poured in and the dilution and the medium were thoroughly mixed. After it solidified, it was placed in an incubator at 37°C for 48 h; as Figure 9 shown, different-shaped colonies in the corresponding petri dishes (the left and right figures are parallel photos of the -7 gradient colony counting petri dishes) were picked and cultured in M17 broth medium for 24 h. After centrifugation to obtain the bacterial sludge, DNA was extracted using a bacterial DNA kit, and after sequencing, splicing, and retrieval from the base database, it was proved to be Streptococcus thermophilus before being preserved and stored.

[0147] Furthermore, the inventor carried out the same activity test on Streptococcus thermophilus YSC1003 with reference to the methods of the foregoing Examples 2, 5, and 6. The results showed that Streptococcus thermophilus YSC1003 has good fermentation performance and safety. The fermented milk prepared has a short fermentation time, a large number of viable bacteria, high viscosity and water-holding capacity, and high antioxidant activity.

[0148] Example 8: Preparation of Bacterial Powders of Streptococcus thermophilus Strains YSC1001 and YSC1003

[0149] A method for preparing a freeze-dried powder of Streptococcus thermophilus includes the following steps: Streptococcus thermophilus YSC1001 and YSC1003 were separately activated and inoculated into M17 broth medium at an inoculation amount of 5%. After being cultured at 37°C for 48 h with expansion, a fermentation broth containing 10 10 CFU / mL viable bacteria was obtained. After centrifuging the fermentation broth, the mass of the bacterial sludge was weighed and homogenized according to the following mass ratio: Streptococcus thermophilus bacterial sludge: freeze-drying protectant = 1:4. The freeze-drying protectant consists of skim milk powder: trehalose: maltodextrin: sodium glutamate: water = 5:4:2:2:37. After homogenization, it was pre-frozen at -80°C for 24 h and then freeze-dried for 24 h to obtain two kinds of Streptococcus thermophilus powder, YSC1001 and YSC1003.

[0150] Among the two kinds of Streptococcus thermophilus freeze-dried powders, the viable lactic acid bacteria count determination method in the "National Food Safety Standard Food Microbiological Examination Lactic Acid Bacteria Examination" (GB 4789.35-2023) was used to measure that both powders contain 1010 The viable count of Streptococcus thermophilus in CFU / g.

[0151] Example 9: Application of the Compound Bacterial Powders of Streptococcus thermophilus Strains YSC1001 and YSC1003 in the Preparation of Fermented Milk with High Antioxidant Activity in Application

[0152] 1. Preparation of fermented milk

[0153] A method for preparing fermented milk with high antioxidant activity, comprising the following steps: mixing Streptococcus thermophilus powder YSC1001 and YSC1003 in a ratio of 1:1 (ratio of viable counts), inoculating into a sterilized modified skim milk powder medium at an inoculum size of 10 7 CFU / g, ensuring that the medium temperature drops to 50 °C during inoculation, homogenizing thoroughly, placing in an incubator at 37 °C for cultivation, and monitoring the pH value of the fermented milk during cultivation. When the pH value reaches 4.5, it indicates that the fermented milk fermentation is complete, obtaining fermented milk E.

[0154] In addition, fermented milks A, B, C, D, F, and G were also prepared.

[0155] Preparation of fermented milk A: Inoculating Streptococcus thermophilus powder YSC1001 into a sterilized modified skim milk powder medium at an inoculum size of 10 7 CFU / g, ensuring that the medium temperature drops to 50 °C during inoculation, homogenizing thoroughly, placing in an incubator at 37 °C for cultivation, and monitoring the pH value of the fermented milk during cultivation. When the pH value reaches 4.5, it indicates that the fermented milk fermentation is complete, obtaining fermented milk A.

[0156] Preparation of fermented milk B: Inoculating Streptococcus thermophilus powder YSC1003 into a sterilized modified skim milk powder medium at an inoculum size of 10 7 CFU / g, ensuring that the medium temperature drops to 50 °C during inoculation, homogenizing thoroughly, placing in an incubator at 37 °C for cultivation, and monitoring the pH value of the fermented milk during cultivation. When the pH value reaches 4.5, it indicates that the fermented milk fermentation is complete, obtaining fermented milk B.

[0157] Preparation of fermented milk C: Mixing Streptococcus thermophilus powder YSC1001 and YSC1003 in a ratio of 1:1 (ratio of viable counts), inoculating into a sterilized skim milk powder medium that has been ultrasonically treated and does not contain inulin at an inoculum size of 10 7 CFU / g, ensuring that the medium temperature drops to 50 °C during inoculation, homogenizing thoroughly, placing in an incubator at 37 °C for cultivation, and monitoring the pH value of the fermented milk during cultivation. When the pH value reaches 4.5, it indicates that the fermented milk fermentation is complete, obtaining fermented milk C.

[0158] Preparation of fermented milk D: Mixing Streptococcus thermophilus powder YSC1001 and YSC1003 in a ratio of 1:1 (ratio of viable counts), inoculating at an inoculum size of 107 Inoculate into a sterilized skim milk powder medium added with inulin without ultrasonic treatment at an inoculum amount of CFU / g, and ensure that the temperature of the medium drops to 50 °C during inoculation. After sufficient homogenization, place it in an incubator at 37 °C for cultivation, and monitor the pH value of the fermented milk during the cultivation process. When the pH value reaches 4.5, it indicates that the fermented milk is completely fermented, and fermented milk D is obtained.

[0159] Preparation of fermented milk F: Reconstitute Streptococcus thermophilus powder YSC1001 and YSC1003 at a ratio of 2:1 (ratio of viable cell counts), and inoculate at an inoculum amount of 10 7 CFU / g into a sterilized modified skim milk powder medium. Ensure that the temperature of the medium drops to 50 °C during inoculation. After sufficient homogenization, place it in an incubator at 37 °C for cultivation, and monitor the pH value of the fermented milk during the cultivation process. When the pH value reaches 4.5, it indicates that the fermented milk is completely fermented, and fermented milk F is obtained.

[0160] Preparation of fermented milk G: Reconstitute Streptococcus thermophilus powder YSC1001 and YSC1003 at a ratio of 1:2 (ratio of viable cell counts), and inoculate at an inoculum amount of 10 7 CFU / g into a sterilized modified skim milk powder medium. Ensure that the temperature of the medium drops to 50 °C during inoculation. After sufficient homogenization, place it in an incubator at 37 °C for cultivation, and monitor the pH value of the fermented milk during the cultivation process. When the pH value reaches 4.5, it indicates that the fermented milk is completely fermented, and fermented milk G is obtained.

[0161] Among them:

[0162] 1) The preparation method of the sterilized modified skim milk powder medium is as follows:

[0163] Dissolve 12 g of skim milk powder in 100 mL of distilled water, and perform ultrasonic treatment under the conditions of a power of 580 W, a time of 17 min, and an intermittent ratio of 1:1. Then, perform high-pressure sterilization at 105 °C for 15 min. After the temperature drops to 50 °C, add 7.5 g of sucrose and 4 g of inulin, and homogenize and mix thoroughly to obtain the target medium.

[0164] 2) The preparation method of the sterilized skim milk powder medium that has been ultrasonically treated and does not contain inulin is as follows:

[0165] Dissolve 12 g of skim milk powder in 100 mL of distilled water, and perform ultrasonic treatment under the conditions of a power of 580 W, a time of 17 min, and an intermittent ratio of 1:1. Then, perform high-pressure sterilization at 105 °C for 15 min. After the temperature drops to 50 °C, add 7.5 g of sucrose, and homogenize and mix thoroughly to obtain the target medium.

[0166] 3) The preparation method of the sterilized skim milk powder medium added with inulin without ultrasonic treatment is as follows:

[0167] Dissolve 12 g of skim milk powder in 100 mL of distilled water and sterilize it under high pressure at 105 °C for 15 min. After the temperature drops to 50 °C, add 7.5 g of sucrose and 4 g of inulin, and mix them thoroughly by homogenization to obtain the target culture medium.

[0168] 2. Determination of the fermentation time of fermented milk

[0169] Measure the fermentation time of each of the above groups, and the results are shown in Table 5 below.

[0170] Table 5: Fermentation time of fermented milk in each group

[0171] Group Category of Inoculated Strains Fermentation Time / h Group A Streptococcus thermophilus YSC1001, Ultrasonic Treatment, Inulin <![CDATA[7.3±0.10 a > Group B Streptococcus thermophilus YSC1003, Ultrasonic Treatment, Inulin <![CDATA[7.2±0.03 a > Group C Streptococcus thermophilus YSC1001: Streptococcus thermophilus YSC1003 = 1:1, Ultrasonic Treatment <![CDATA[6.7±0.17 b > Group D Streptococcus thermophilus YSC1001: Streptococcus thermophilus YSC1003 = 1:1, Inulin <![CDATA[6.6±0.10 b > Group E Streptococcus thermophilus YSC1001: Streptococcus thermophilus YSC1003 = 1:1, Ultrasonic Treatment, Inulin <![CDATA[6.3±0.09 d > Group F Streptococcus thermophilus YSC1001: Streptococcus thermophilus YSC1003 = 2:1, Ultrasonic Treatment, Inulin <![CDATA[6.4±0.02 cd > Group G Streptococcus thermophilus YSC1001: Streptococcus thermophilus YSC1003 = 1:2, Ultrasonic Treatment, Inulin <![CDATA[6.5±0.05 c >

[0172] As can be seen from Table 5 above, under the same inoculum size, compared with a single strain, the fermentation time of the fermented milk prepared with the compound strain of the present invention is significantly shortened.

[0173] 3. Determination of the viable count of fermented milk

[0174] Adopt the method for determining the viable count of lactic acid bacteria in the "National Food Safety Standard Food Microbiology Examination Lactic Acid Bacteria Examination" (GB 4789.35-2023) to measure the viable count of lactic acid bacteria (LogCFU / mL) in the fermented milk of each of the above groups, and the results are shown in Table 6 below.

[0175] Table 6: Results of viable count of fermented milk in each group

[0176]

[0177] As can be seen from Table 6 above, under the same inoculum size, compared with a single strain, the viable count of the fermented milk prepared with the compound strain of the present invention is significantly increased.

[0178] 4. Determination of the viscosity and water holding capacity of fermented milk

[0179] Measure the viscosity and water holding capacity of each of the above groups. The results are shown in Table 7 below.

[0180] Determination of the viscosity of fermented milk: Use a viscometer with a rotor of LV-4(64) to measure the viscosity of the fermented milk at 100 rpm and take the value at 30 s to measure the viscosity of the fermented milk.

[0181] Determination of the water holding capacity of fermented milk: Weigh a 50 mL centrifuge tube (W 0 ), put the fermented milk (10 mL) of each group after fermentation into it, and record the weight as W 1 . After centrifugation at 5500 r / min for 30 min, take it out and let it stand for stratification, then weigh the centrifuge tube after discarding the supernatant and record it as W 2 . The calculation formula for the water holding capacity of fermented milk is as follows.

[0182] Water holding capacity (%) = (W 2 - W 0 ) / (W 1 - W 0 ) × 100

[0183] Table 7: Viscosity and water holding capacity results of fermented milk

[0184]

[0185] As can be seen from Table 7 above, under the same inoculation amount, compared with a single strain, the viscosity and water holding capacity of the fermented milk prepared with the compound strain of the present invention are significantly improved.

[0186] 5. Determination of antioxidant activity of fermented milk

[0187] Take the fully fermented samples of each group, centrifuge at 4°C and 10,000 × g for 10 min, collect the supernatant and filter it through a 0.45 μm filter membrane to obtain the sample to be tested. Then, evaluate the antioxidant activity of the fermented milk of each group by measuring the DPPH radical scavenging rate, hydroxyl radical scavenging rate, and ABTS + radical scavenging rate.

[0188] 1) Determination of DPPH radical scavenging rate

[0189] Prepare a 0.16 mmol / L DPPH solution (dissolved in 95% ethanol). Take 5 mL of it and mix it with 2 mL of the sample (fermented milk sample or distilled water), then let it stand and react in the dark for 30 min. Put the reacted mixture into a centrifuge tube and centrifuge (4000 r / min, 10 min). After centrifugation, measure the absorbance of the supernatant (wavelength is 517 nm). Among them, A 0 is the measured value of distilled water, A 1 is the measured value of fermented milk, and A 2 is the measured value of the DPPH solution with 95% ethanol. The formula for the DPPH radical scavenging rate is as follows.

[0190] DPPH radical scavenging rate (%) = [A 0 - (A 1 - A 2 )] / A 0 × 100

[0191] 2) Determination of hydroxyl radical scavenging rate

[0192] Prepare H 2 O 2 (8.8 mmol / L), FeSO 4(9 mmol / L) and salicylic acid (9 mmol / L) solutions. Take 1 mL of each of the three different solutions and add them to the sample (1 g of fermented milk or distilled water) in sequence. Add 9 times the volume of 95% ethanol solution to this system. After mixing the mixture, take 2 mL of it and place it in a water bath (37 °C, 30 min). Take it out and let it stand at room temperature, and measure the absorbance value (510 nm) of the supernatant. Among them, A 0 : The measured value of distilled water, A 1 : The measured value of fermented milk, A 2 : Distilled water replaces H in the reaction process 2 O 2 solution, and the measured background absorbance value. The formula for the hydroxyl radical scavenging rate is as follows.

[0193] Hydroxyl radical scavenging rate (%) = [A 0 -(A 1 -A 2 )] / A 0 ×100

[0194] 3) ABTS + Free radical scavenging rate determination

[0195] Prepare ABTS (7.4 mmol / L) and K 2 S 2 O 8 solution (2.6 mmol / L). Take 3 mL of each and mix them well. After fully reacting (in the dark, 4 °C, 16 h), take out the reacted mixture and dilute it (anhydrous ethanol) until the absorbance (734 nm) is 0.70 ± 0.02. Take 3.5 mL of the diluted solution and mix it with 0.5 mL of fermented milk, and react in the dark (20 °C, 10 min). Take the supernatant of the reacted solution and measure the absorbance (734 nm), denoted as A 1 . The formula for the ABTS + free radical scavenging rate is as follows.

[0196] ABTS + Free radical scavenging rate (%) = (A 1 -0.7) / 0.7×100

[0197] The DPPH free radical scavenging rate, hydroxyl radical scavenging rate, and ABTS + free radical scavenging rate determination results of each group of fermented milk are as Figure 10 、 Figure 11 and Figure 12 shown.

[0198] From Figures 10 - 12It can be seen that, under the same inoculation amount, compared with a single strain, the antioxidant activity of the fermented milk prepared from the compound strains of the present invention is significantly improved. Further, the fermented milk prepared by compounding Streptococcus thermophilus YSC1001 and YSC1003 and supplemented with ultrasonic and inulin processes not only has excellent physical and chemical properties, but also has good antioxidant activity, and the health care performance of the fermented milk is improved.

[0199] Although the specific embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details according to all the teachings that have been disclosed, and these changes are within the protection scope of the present invention. The full scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. Streptococcus thermophilus, which is deposited in the General Microbiological Center of China Microbiological Culture Collection Administration, with the deposit number of CGMCC No.28253.

2. A composition comprising a first thermophilic Streptococcus, wherein the first thermophilic Streptococcus is as defined in claim 1; Preferably, the composition further comprises a second thermophilic Streptococcus, which is deposited in the General Microbiological Center of China National Microbiological Culture Collection Administration with a deposit number of CGMCC No.28251.

3. The composition according to claim 2, wherein The ratio of the number of viable bacteria of the first thermophilic streptococcus to the number of viable bacteria of the second thermophilic streptococcus is 1:20-20:1, preferably 1:2-2:1, and more preferably 1:

1.

4. The composition according to any one of claims 2 to 3, wherein The composition further comprises additional probiotic bacteria and / or probiotic fungi (e.g. yeast), wherein the additional probiotic bacteria and / or probiotic fungi are edible; Preferably, the composition further comprises additional additives or edible excipients; Preferably, the additional additive is a nutrient selected from dietary fiber, prebiotics, protein, lipids, minerals, vitamins, plant extracts, or any combination thereof; Preferably, the edible auxiliary material is selected from bleaching agents, preservatives, antioxidants, colorants, sweeteners, acidulants, flavor enhancers, color retainers, or any combination thereof; Preferably, the dosage form of the composition is selected from powder, tablet, liquid, pill, capsule, granule, film-coated tablet, sachet, dragee.

5. A composite bacterial powder comprising a first thermophilic Streptococcus powder and a second thermophilic Streptococcus powder, wherein the first thermophilic Streptococcus is as defined in claim 1, and the second thermophilic Streptococcus is deposited in the General Microbiological Center of China Microorganism Culture Collection Administration, with a deposit number of CGMCC No. 28251; Preferably, the ratio of the number of viable bacteria of the first thermophilic Streptococcus powder to the number of viable bacteria of the second thermophilic Streptococcus powder is 1:20-20:1, preferably 1:2-2:1, more preferably 1:1; Preferably, the viable count of the first thermophilic Streptococcus powder or the second thermophilic Streptococcus powder is 1×10 9 CFU / g~1×10 11 CFU / g, preferably 10 10 CFU / g.

6. The composite bacterial powder according to claim 5, wherein: The first thermophilic streptococcus powder or the second thermophilic streptococcus powder is obtained by freeze-drying the first thermophilic streptococcus liquid or the second thermophilic streptococcus liquid; Preferably, the number of viable bacteria in the first thermophilic streptococcus bacterial liquid and the second thermophilic streptococcus bacterial liquid is equal; Preferably, the viable cell count of the first thermophilic Streptococcus bacterial liquid or the second thermophilic Streptococcus bacterial liquid is 1×10 9 CFU / mL~1×10 11 CFU / mL, preferably 10 10 CFU / mL; Preferably, the first thermophilic streptococcus powder or the second thermophilic streptococcus powder is obtained by sequentially subjecting the first thermophilic streptococcus liquid or the second thermophilic streptococcus liquid to centrifugation, homogenization and freeze-drying steps respectively; Preferably, after the centrifugation, the first thermophilic Streptococcus sludge or the second thermophilic Streptococcus sludge is subjected to a homogenization step; Preferably, the homogenization is performed in the presence of a lyoprotectant; Preferably, after the homogenization and before the freeze-drying, a pre-freezing step is also included.

7. A food, health product or medicine, comprising the thermophilic Streptococcus according to claim 1, the composition according to any one of claims 2 to 4, or the composite bacterial powder according to any one of claims 5 to 6; Preferably, the food is selected from fermented dairy products, fermented bean products, fermented fruit and vegetable products, fermented meat products, fermented beverages, probiotic fermentation agents, and probiotic solid beverages; Preferably, the fermented dairy product is selected from fermented milk, yogurt (such as room temperature yogurt, low temperature yogurt, stirred yogurt, set yogurt or drinkable yogurt), kefir, fermented buttermilk, yogurt wine, milk wine, cheese, and lactic acid bacteria beverage; Preferably, the food, health product or medicine further comprises prebiotics.

8. A fermented dairy product obtained by fermentation using the thermophilic streptococcus according to claim 1, the composition according to any one of claims 2 to 4, or the composite bacterial powder according to any one of claims 5 to 6; Preferably, the fermentation medium is a skim milk powder medium, and the skim milk powder medium comprises skim milk powder, sucrose, inulin and water; Preferably, in the skim milk powder culture medium, the mass ratio of the skim milk powder to the sucrose is (11-12):(7-8); Preferably, in the skim milk powder culture medium, the mass ratio of the skim milk powder to the inulin is (11-12):(3.5-4.5); Preferably, the fermented dairy product is selected from fermented milk, yogurt (such as room temperature yogurt, low temperature yogurt, stirred yogurt, set yogurt or drinkable yogurt), kefir, fermented buttermilk, yogurt wine, milk wine, cheese, and lactic acid bacteria beverage; Preferably, the fermented dairy product is fermented milk.

9. The fermented dairy product according to claim 8, wherein The skim milk powder culture medium is prepared by the following method: 1) subjecting the aqueous solution of skimmed milk powder to ultrasonic sterilization; 2) mixing and homogenizing the solution obtained in step 2) with the inulin and the sucrose to obtain the skim milk powder culture medium; Preferably, the ultrasound is performed at a power of 550 to 600 W, a time of 15 to 20 min, and an intermittent ratio of 1:1; Preferably, the mixing and homogenizing are carried out at a temperature of 40°C to 60°C.

10. Use of the thermophilic streptococcus according to claim 1, the composition according to any one of claims 2 to 4, or the composite bacterial powder according to any one of claims 5 to 6 in preparing health products or medicines, The drug is used for one or more selected from the following A)-I): A) Anti-oxidation; B) Anti-aging; C) Lowering blood sugar; D) Lowering blood lipids; E) Lowering cholesterol; F) Enhancing immunity; G) Regulating intestinal flora; H) Promoting digestion; I) Lubricating the intestines and relieving constipation; The health care product has one or more uses selected from the following a)-g): a) Helps with antioxidants; b) Helps maintain healthy blood sugar levels; c) Helps maintain healthy blood lipid (cholesterol / triglyceride) levels; d) Helps enhance immunity; e) Helps regulate intestinal flora; f) Helps with digestion; g) Helps moisturize the intestines and promote bowel movements.

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