Bifidobacterium lactis BL-YR55 with weight losing and fat reducing functions and application of bifidobacterium lactis BL-YR55

Abstract

The invention discloses bifidobacterium lactis BL-YR55 screened from yoghourt, the bifidobacterium lactis BL-YR55 is preserved in China Center for Type Culture Collection, the preservation number is CCTCC No.M 20221997, the bifidobacterium lactis BL-YR55 is classified and named as bifidobacterium lactis BL-YR55, the preservation date is December 23, 2022, and the preservation address is Wuhan University, China. The composition has efficient weight-losing and fat-reducing effects, is effective in viable bacteria sterilization, also has a function of relieving lactose intolerance, and has a wide application prospect of medicinal or health-care products.

Description

Technical Field

[0001] The present application relates to the technical field of Bifidobacterium lactis, and in particular to a strain of Bifidobacterium lactis BL-YR55 having weight loss and fat reduction functions and its application. Background Art

[0002] Bifidobacterium lactis is a Gram-positive bacterium with a short rod or fusiform shape. The size of Bifidobacterium lactis is about 0.5 to 0.9 microns wide and 2.0 to 10.0 microns long, sometimes slightly curved or branched. Its surface is covered with filamentous pili, which help it attach and grow in the intestine. Bifidobacterium lactis is an anaerobic bacterium that can grow and reproduce in an environment without oxygen. It can use a variety of carbon sources for nutrition, including glucose, lactose, maltose, fructose, galactose and xylose. In addition, Bifidobacterium lactis has the ability to produce lactic acid and acetic acid, which are organic acids that can lower the pH value of the intestine and inhibit the reproduction of harmful bacteria. Bifidobacterium lactis is a non-pathogenic bacterium, safe and non-toxic. It exists in the natural microbial community of the human body and coexists symbiotically with the human body. Therefore, Bifidobacterium lactis is widely used in health products and pharmaceutical products and is considered to be a safe and effective probiotic. Bifidobacterium lactis has antibacterial activity and can inhibit the growth of harmful bacteria in the intestines to prevent them from causing harm to intestinal health. It can break down complex carbohydrates, proteins and fats in food, promote the absorption of nutrients, improve digestive function, stimulate the immune response in the intestines, increase the production and activity of immune cells, and enhance the body's defense against disease.

[0003] The present invention aims to provide a strain of Bifidobacterium lactis BL-YR55 with weight loss and fat reduction function and application thereof. Summary of the invention

[0004] In view of this, the purpose of the embodiments of the present application is to broaden the research and understanding of Bifidobacterium lactis, to provide its application in multiple fields, and even to obtain a strain of Bifidobacterium lactis BL-YR55 with weight loss and fat reduction function and its application through a large number of screenings, especially, even in an inactivated state, it has a certain effect.

[0005] In the first aspect, the embodiments of the present application disclose a strain of Bifidobacterium lactis BL-YR55, which is deposited in the China Center for Type Culture Collection with a deposit number of CCTCC No.M 20221997, classified as Bifidobacterium lactis BL-YR55, deposited on December 23, 2022, and deposited at Wuhan University, China.

[0006] In a second aspect, the examples of the present application disclose the use of the Bifidobacterium lactis BL-YR55 in a weight loss and fat reduction preparation.

[0007] In a third aspect, the examples of the present application disclose the bacterial powder prepared from the Bifidobacterium lactis BL-YR55.

[0008] In a fourth aspect, the present application discloses a method for preparing the bacterial powder of Bifidobacterium lactis BL-YR55.

[0009] The preparation method is as follows:

[0010] S1, prepare seed suspension, melt the glycerol tube of Bifidobacterium lactis BL-YR55 preserved at -20 ℃, take 1mL and inoculate into 45~108mL containing 10-12g / L of protein Chen, 10-12g / L of beef extract, 5-7g / L of yeast powder, 2-4g / L of dipotassium hydrogen phosphate, 2-4g / L of tricitrate, 5-7g / L of sodium acetate, 1-3mL / L of Tween-80, 0.2-0.5g / L of magnesium sulfate, 0.05-0.07g / L of sulfuric acid, 20-23g / L of glucose sterilized separately, pH=6.5, sterilized at 122 ℃ for 30min in MRS liquid medium, and culture at 32~36 ℃ for 11~17h. After the culture is completed, centrifuge and wash 3 times with sterile physiological water, and then adjust the bacterial suspension to a suitable concentration with sterile water for standby use;

[0011] S2, obtaining a fermentation broth, wherein the fermentation broth is obtained by transferring the seed suspension to the fermentation broth, wherein the fermentation broth comprises 50-52 g / L skim milk powder, 8-10 g / L soy protein isolate, 20-23 g / L glucose, 8-10 g / L beef extract, 23-25 ​​g / L NaCl, 2-5 g / L MgSO 4 7H 2 O, 1-3g / L Span S-80, adjust pH=5.80, sterilize at 122°C for 20min, transfer the seed suspension obtained in step S1 to the fermentation medium, and ferment at 32-37°C, 100-120rpm stirring conditions, and ferment for 30-72h to obtain the fermentation liquid, wherein the ratio of air volume to tank volume is 1:0.5-1 (v / vm);

[0012] S3, centrifugal collection, collect the fermented liquid 30-35ml and place it in a sterile 50ml centrifuge tube for centrifugation, the centrifugation conditions are 5000r / min, 20min, 4℃ or 8000r / min, 10min, 4℃, after the centrifugation is completed, discard the supernatant and collect the bacterial mud;

[0013] S4. Preparation of freeze-dried bacterial suspension: collect centrifuged bacterial cells, add a bacterial mud protective agent prepared by 20% milk powder, 10-12% trehalose, 2-5% glycerol, 5-8% xylo-oligosaccharide and ultrapure water, vortex and mix well, the volume of the protective agent added is 1 / 5 of the culture solution before centrifugation, and the freeze-dried bacterial suspension is obtained, and placed at room temperature for 1 hour to allow the protective agent and the bacterial cells to fully fuse;

[0014] S5. Vacuum freeze drying: pre-freeze in a -70°C refrigerator for 3 hours to freeze the freeze-dried bacterial suspension into a solid. Put it into a freeze dryer immediately after taking it out to avoid damage to the bacteria due to a sudden rise in temperature. Place the sample in a freeze dryer and continue freeze drying for 24 hours to obtain Bifidobacterium lactis BL-YR55 powder. Before starting freeze drying, the freeze dryer should be turned on in advance to reduce the cold trap temperature to -60°C and the vacuum degree to 1000Pa during operation.

[0015] The Bifidobacterium lactis BL-YR55 screening yogurt of the present invention.

[0016] Compared with the prior art, this application has at least the following beneficial effects:

[0017] The present application screened a strain of Bifidobacterium lactis BL-YR55 with weight loss and fat reduction function from yogurt and its application, which can regulate energy intake, absorption and consumption by affecting the composition and metabolic activity of intestinal flora, can affect the release of gastrointestinal hormones through interaction with the nervous system, regulate appetite and satiety, and can also inhibit fat absorption, reduce fat deposition and storage, and is effective in both live and inactivated states. In addition, it was unexpectedly found that the bacteria has the function of alleviating lactose intolerance and has a wide range of application prospects for medicinal or health products. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an optical microscope image of Bifidobacterium lactis BL-YR55.

[0019] Figure 2 This is a graph showing the TC (cholesterol) and TG (triglyceride) levels in mice.

[0020] Figure 3 This is a graph showing the levels of HDL-C (high-density lipoprotein cholesterol) and LDL-C (low-density lipoprotein cholesterol) in mice.

[0021] Figure 4 This is a graph of lactase activity in mouse large intestine.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0024] Example 1 Screening and identification of Bifidobacterium lactis BL-YR55

[0025] The applicant has conducted a large number of screenings from yogurt and obtained several strains of bacteria with good health functions, among which the one involved in the present invention is named Bifidobacterium lactis BL-YR55.

[0026] Identification of Bifidobacterium lactis BL-YR55

[0027] Physiological and biochemical identification

[0028] According to the Bergey's Bacteria Identification Manual and the Common Bacteria System Identification Manual, the API physiological and biochemical indicators of strain BL-YR55 were determined. The specific results are shown in Table 1. Referring to the bacterial species identification manual, it can be known that strain BL-YR55 meets the characteristics of Bifidobacterium bacteria and can be preliminarily determined to be Bifidobacterium bacteria.

[0029] Table 1 Identification results of API physiological and biochemical characteristics of strain BL-YR55

[0030]

[0031]

[0032] Bifidobacterium lactis BL-YR55 isolation medium (MRS medium): beef extract 10g, protein 10g, acetic acid 5g, potassium dihydrogen phosphate 2g, hydrogen citrate 2g, magnesium sulfate heptahydrate 0.58g, sulfuric acid tetrahydrate 0.25g, glucose 20g, Tween-80 1mL, distilled water 1L, pH 6.2-6.4, 115°C, 20min sterilization for standby use, solid culture medium plus 0.5-2% agar.

[0033] Preparation of TE buffer: Take 5 ml of Tris-HCl Buffer solution with a pH of 8.0 and a concentration of 1 M, and then take 1 ml of EDTA solution with a pH of 8.0 and a concentration of 0.5 M, place them in a beaker, add about 400 ml of deionized water to the beaker and mix evenly, then transfer to a volumetric flask and make up the solution to 500 ml, sterilize it at high temperature and high pressure, and store it at room temperature.

[0034] The Bifidobacterium lactis BL-YR55 strain was inoculated into MRS medium at a 1% inoculation rate, cultured overnight at 37°C for 12 hours, 5 ml of the bacterial solution was centrifuged at 9000 pm for 2 minutes, and the supernatant was discarded to obtain the bacteria. After centrifugation and washing twice with TE buffer, the genome of the target strain was extracted using the bacterial genome extraction kit of OMEGA.

[0035] The PCR amplification and sequence determination of 16SrDNA gene used universal primers for prokaryotic 16SrDNA amplification, forward primer: fD1 5'-CGATCAGCTCGAGTCGAAGA-3', reverse primer: rP1 5'-CACTCGCTGGATCATCTCCT-3'.

[0036] PCR reaction system includes: 10x PCR buffer, 5pL; 10mmol / L MgCl 2 , 3μL; 2.0μmol / L dNTP, 4μL; 10mol / L fD1, 3μL; 10mol / L rP1, 3μL; 1.0mol / L DNA template, 1μL, 5U / μL Tag TM DNA polymerase (TaKaRa), 1 μL; ddH 2 O,30L; the total reaction system is 50pL. The target fragment obtained by PCR amplification is connected to the T vector to transform Escherichia coli DH5a, and then the transformant is picked and sent to Shanghai Sangon Biotechnology Co., Ltd. for sequencing, and the obtained 16SrDNA gene sequence is searched and compared for homology in the gene library. The results show that the bifidobacterium screened in the embodiment of the present application has 99.6% homology with Bifidobacterium lactis CMCC1.2226, so it is named Bifidobacterium lactis BL-YR55, which is deposited in the China Center for Type Culture Collection with a deposit number of CCTCC No.M 20221997, and is classified and named Bifidobacterium lactis BL-YR55. The deposit date is December 23, 2022, and the deposit address is Wuhan University, China.

[0037] Example 2 Preparation of bacterial powder

[0038] S1, prepare seed suspension, melt the glycerol tube of Bifidobacterium lactis BL-YR55 preserved at -20 ℃, take 1mL and inoculate into 40~105mL containing 10g / L protein Chen, 10g / L beef extract, 5g / L yeast powder, 2g / L dipotassium hydrogen phosphate, 2g / L tricitrate, 5g / L sodium acetate, 1mL / L Tween-80, 0.2g / L magnesium sulfate, 0.05g / L sulfuric acid, 20g / L of glucose sterilized separately, pH=6.5, in MRS liquid medium sterilized for 30min at 121 ℃, stand and culture for 12~18h at 32~37 ℃, after culturing, centrifuge and wash 3 times with sterile physiological water, and then adjust the bacterial suspension to suitable concentration with sterile water for standby use;

[0039] S2, obtaining a fermentation broth, wherein the fermentation broth is obtained by transferring the seed suspension to the fermentation broth, wherein the fermentation broth consists of 50 g / L skim milk powder, 8 g / L soy protein isolate, 20 g / L glucose, 8 g / L beef extract, 23 g / L NaCl, 2 g / L MgSO 4 7H 2 O, 1g / L Span S-80, adjust pH=5.80, sterilize at 121°C for 20min, transfer the seed suspension obtained in step S1 to the fermentation medium, and ferment at 32-37°C, 100-120rpm stirring conditions, and ferment for 32-76h to obtain the fermentation liquid, wherein the ratio of air volume to tank volume is 1:0.5-1 (v / vm);

[0040] S3, centrifugal collection, collect the fermented liquid 35ml and place it in a sterile 50ml centrifuge tube for centrifugation, the centrifugation conditions are 5000r / min, 20min, 4℃ or 8000r / min, 10min, 4℃, after the centrifugation is completed, discard the supernatant and collect the bacterial mud;

[0041] S4. Preparation of freeze-dried bacterial suspension: collect centrifuged bacterial cells, add a bacterial mud protective agent prepared by 20% milk powder, 10% trehalose, 2% glycerol, 5% xylo-oligosaccharide and ultrapure water, vortex and mix well, the volume of the protective agent added is 1 / 5 of the culture solution before centrifugation, and obtain a freeze-dried bacterial suspension, which is placed at room temperature for 1 hour to allow the protective agent and bacterial cells to fully fuse;

[0042] S5. Vacuum freeze drying: pre-freeze in a -80°C refrigerator for 3 hours to freeze the freeze-dried bacterial suspension into a solid. Put it into a freeze dryer immediately after taking it out to avoid damage to the bacteria due to a sudden rise in temperature. Place the sample in a freeze dryer and continue freeze drying for 24 hours to obtain Bifidobacterium lactis BL-YR55 powder. Before starting freeze drying, the freeze dryer should be turned on in advance to reduce the cold trap temperature to -60°C and the vacuum degree to 1000Pa during operation.

[0043] Preparation of inactivated bacteria powder: except that the bacterial sludge obtained in the above step S3 is treated at 121° C. for 30 minutes to obtain inactivated bacteria, the remaining steps are the same as the above steps.

[0044] Comparative Example 1: In order to verify the performance difference with ordinary Bifidobacterium lactis, the present application also provides an existing Bifidobacterium lactis as Comparative Example 1. The steps are the same as those in the above Example 1, except that the strain used for fermentation is Bifidobacterium lactis CMCC1.2226 (Lactobacillus casei, referred to as Bifidobacterium lactis BL, purchased from Shanghai Xuanke Biotechnology Co., Ltd.), and BL bacterial powder is also obtained through the above steps.

[0045] Example 3 Fat reduction function test

[0046] Animal Experimentation:

[0047] Fifty SPF male C57BL / 6 mice, weighing 26-28 g, were adaptively raised in an SPF animal room for three weeks and then randomly divided into a normal group, a model group, an embodiment group, a comparative example group, and an inactivated group, a total of 5 groups, with 10 mice in each group.

[0048] Feeding conditions: animals were free to eat and drink, the temperature was maintained at 23℃~25℃, the humidity was 55%±5%, and the cycle was 12h per day. Except for the normal group, which continued to be fed normally, the feed of the other groups was replaced with high-fat feed. After 2 months of feeding, 1 mL of blood was collected from the tail of one mouse in the model group and the blank group, and centrifuged at 4℃ and 3000r for 10 minutes. After centrifugation, the serum was collected and stored in a -80℃ refrigerator. The serum measurement indicators: TC (cholesterol), TG (triglycerides), HDL-C (high-density lipoprotein cholesterol), LDL-C (low-density lipoprotein cholesterol) content, and body weight were analyzed for differences. If the results were significantly different, the modeling was successful.

[0049] From the 61st day, bacterial powder intervention was carried out. The blank group and the model group were fed normally every day. For the example group, the comparative example group and the inactivated group, each mouse was fed with the Bifidobacterium lactis BL-YR55 bacterial powder prepared in Example 2, the Bifidobacterium lactis BL bacterial powder prepared in Comparative Example 1 and the inactivated Bifidobacterium lactis BL-YR55 bacterial powder at an average dose of 0.2 g / mouse / day per day for the next four weeks.

[0050] Mouse sample collection and processing:

[0051] On the 89th day, the weight and length of the mice were measured and recorded, and then the mice were dissected, and 1 mL of blood was collected by eye sampling into a heparin tube, and after centrifugation at 3000 r / min for 10 min within 1 hour, the collected serum was frozen in a -80°C refrigerator for use, the liver was taken out and weighed, and 0.2 g of liver tissue was cut off and immersed in 4% paraformaldehyde fixative, and the other part was frozen in a -80°C refrigerator for use. The levels of TC (cholesterol), TG (triglycerides), HDL-C (high-density lipoprotein cholesterol), and LDL-C (low-density lipoprotein cholesterol) in liver tissue and serum were detected using a kit.

[0052] Table 2

[0053]

[0054] According to the experimental results in Table 2, compared with the normal group, the levels of TC (cholesterol), TG (triglyceride), and LDL-C (low-density lipoprotein cholesterol) in the model group mice were significantly increased, and the HDL-C (high-density lipoprotein cholesterol) was significantly decreased, indicating that the high-fat model was successfully established.

[0055] Hyperlipidemia refers to the biochemical changes of abnormal lipid metabolism in plasma, characterized by increased TC, TG, LDL-C content or decreased HDL-C content. Figure 2 and 3 As shown in Table 2, after the intervention of Bifidobacterium lactis BL-YR55 powder in the embodiment group, the hyperlipidemia of mice was significantly improved, and it can be seen that the fat content also has a certain decline under the inactivated state, while the intervention improvement effect in the comparative group is not significant, indicating that Bifidobacterium lactis BL-YR55 has a specific excellent weight loss and lipid-lowering function. At the same time, it is shown that Bifidobacterium lactis BL-YR55 can effectively reduce the fat content in mice, whether it is live bacteria or inactivated state, to achieve the effect of weight loss and fat reduction.

[0056] Example 4: Lactose intolerance relief test

[0057] Animal Experimentation:

[0058] Fifty SPF male C57BL / 6 mice, weighing 26-28 g, were adaptively raised in an SPF animal room for three weeks and then randomly divided into a normal group, a model group, an embodiment group, a comparative example group, and an inactivated group, a total of 5 groups, with 10 mice in each group.

[0059] Housing conditions: Animals were allowed to eat and drink freely, the temperature was maintained at 23℃~25℃, the humidity was 55%±5%, and the day and night cycle was 12h per day. In addition to the normal group continuing normal feeding and being gavaged with pure water, the model group was gavaged with the lactose inhibitor Castanospermine in addition to normal feeding. The example group added the bacterial powder of Bifidobacterium lactis BL-YR55 prepared in Example 2 in an amount of 0.2 g / mouse / day to the feed, and also gavaged with the lactose inhibitor Castanospermine; the comparative group added the bacterial powder of Bifidobacterium lactis BL prepared in Example 2 in an amount of 0.2 g / mouse / day to the feed, and also gavaged with the lactose inhibitor Castanospermine; the inactivated group added the inactivated bacterial powder of Bifidobacterium lactis BL-YR55 prepared in Example 2 in an amount of 0.2 g / mouse / day to the feed, and also gavaged with the lactose inhibitor Castanospermine; the gavage dose was 3 mg / 100 g for all mice. The mice were killed after 28 days of feeding, and the small intestine was taken out immediately after killing to measure the lactase activity.

[0060] Table 3

[0061] Group Lactase activity U / mg Normal group 163.49±10.41 Model Group 54.23±7.37 Example Group 166.45±10.12 Comparative group 56.19±9.91 Inactivation group 127.38±9.63

[0062] According to Table 3, the lactase activity of the model group was significantly reduced, indicating that the mouse lactose intolerance model was successfully established. Figure 4 From the lactose activity graph, we can see that after intervention with Bifidobacterium lactis BL-YR55, the lactase activity in mice increased significantly, effectively alleviating the symptoms of lactose intolerance in mice, while the intervention with Bifidobacterium lactis BL powder in the control group did not alleviate the symptoms of lactose intolerance in mice. At the same time, it can be found that the inactivated Bifidobacterium lactis BL-YR55 can also alleviate the symptoms of lactose intolerance in mice.

[0063] Example 5 BL-YR55 safety test

[0064] Acute toxicity test

[0065] Thirty clean-grade Kunming male mice that had undergone adaptive feeding were randomly divided into three groups, with 10 mice in each group. They were divided into a normal group, a BL-YR55 group, and a BL-YR55 inactivated group. The prepared bacterial powder was fed at a dose of 0.2g / 10g body weight per mouse, three times a day, with an interval of 3h each time. The normal group was fed the same amount of feed. The activity status of the mice was observed within 7 days. After feeding, the mice were weighed and killed by cervical dislocation, and the liver coefficient and kidney coefficient of the mice were calculated.

[0066] Table 3

[0067] Group Weight / g Liver organ index / % Renal organ index / % Normal group 27.07±1.26 4.59±0.24 1.32±0.06 BL-YR55 Group 27.13±1.18 4.58±0.30 1.34±0.04 BL-YR55 inactivation group 27.01±1.40 4.58±0.28 1.33±0.03

[0068] Within 7 days of feeding, the mice's eating, drinking and activities were normal, with no abnormal behavior and normal fur. According to Table 3, the weight results showed that the mice in the BL-YR55 group and the BL-YR55 inactivated group had normal weights, with no significant difference from the normal group. The liver organ coefficient and kidney organ coefficient of the mice in the BL-YR55 group and the BL-YR55 inactivated group were not significantly different from those in the normal group, indicating that Bifidobacterium lactis BL-YR55 is safe and non-toxic.

[0069] In summary, the present application screened a strain of Bifidobacterium lactis BL-YR55 from yogurt, which has excellent weight loss and fat reduction effects, and is effective in both live bacteria and sterilization. In addition, it has an unexpected effect of alleviating lactose intolerance, and has a wide range of application prospects in medicinal or health products.

[0070] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A strain of Bifidobacterium lactis BL-YR55, deposited in the China Center for Type Culture Collection, with the deposit number CCTCC No.M20221997, classified as Bifidobacterium lactis BL-YR55, deposited on December 23, 2022, and deposited at Wuhan University, China.

2. Use of the Bifidobacterium lactis BL-YR55 according to claim 1 in a weight loss and fat reduction preparation.

3. The bacterial powder prepared from the Bifidobacterium lactis BL-YR55 according to claim 1. The bacterial powder according to claim 3, which is in a live bacteria or inactivated state.

5. The method for preparing the bacterial powder according to claim 3, wherein the steps are as follows: S1, prepare seed suspension, melt the glycerol tube of Bifidobacterium lactis BL-YR55 preserved at -20 ℃, take 1mL and inoculate into 45~108mL containing 10-12g / L of protein Chen, 10-12g / L of beef extract, 5-7g / L of yeast powder, 2-4g / L of dipotassium hydrogen phosphate, 2-4g / L of tricitrate, 5-7g / L of sodium acetate, 1-3mL / L of Tween-80, 0.2-0.5g / L of magnesium sulfate, 0.05-0.07g / L of sulfuric acid, 20-23g / L of glucose sterilized separately, pH=6.5, sterilized at 122 ℃ for 30min in MRS liquid medium, and culture at 32~36 ℃ for 11~17h. After the culture is completed, centrifuge and wash 3 times with sterile physiological water, and then adjust the bacterial suspension to a suitable concentration with sterile water for standby use; S2, obtaining a fermentation broth, wherein the fermentation broth is obtained by transferring the seed suspension to the fermentation broth, wherein the fermentation broth is composed of 50-52 g / L skim milk powder, 8-10 g / L soy protein isolate, 20-23 g / L glucose, 8-10 g / L beef extract, 23-25 ​​g / L NaCl, 2-5 g / L MgSO4·7H2O, 1-3 g / L Span S-80, adjusting pH=5.80, and sterilizing at 122°C for 20 min, transferring the seed suspension obtained in step S1 to the fermentation broth, and aerating and fermenting at 32-37°C, 100-120 rpm stirring conditions, and fermenting for 30-72 h to obtain the fermentation broth, wherein the ratio of air volume to tank volume is 1:0.5-1 (v / vm); S3, centrifugal collection, collect the fermented liquid 30-35ml and place it in a sterile 50ml centrifuge tube for centrifugation, the centrifugation conditions are 5000r / min, 20min, 4℃ or 8000r / min, 10min, 4℃, after the centrifugation is completed, discard the supernatant and collect the bacterial mud; S4. Preparation of freeze-dried bacterial suspension: collect centrifuged bacterial cells, add a bacterial mud protective agent prepared by 20% milk powder, 10-12% trehalose, 2-5% glycerol, 5-8% xylo-oligosaccharide and ultrapure water, vortex and mix well, the volume of the protective agent added is 1 / 5 of the culture solution before centrifugation, and the freeze-dried bacterial suspension is obtained, and placed at room temperature for 1 hour to allow the protective agent and the bacterial cells to fully fuse; S5. Vacuum freeze drying: pre-freeze in a -70°C refrigerator for 3 hours to freeze the freeze-dried bacterial suspension into a solid. Put it into a freeze dryer immediately after taking it out to avoid damage to the bacteria due to a sudden rise in temperature. Place the sample in a freeze dryer and continue freeze drying for 24 hours to obtain Bifidobacterium lactis BL-YR55 powder. Before starting freeze drying, the freeze dryer should be turned on in advance to reduce the cold trap temperature to -60°C and the vacuum degree to 1000Pa during operation.

6. Use of the Bifidobacterium lactis BL-YR55 according to claim 1 in the preparation of a weight loss preparation.

7. The use according to claim 6, wherein: The bacterial powder contains a protective agent.

8. Use of the Bifidobacterium lactis BL-YR55 according to claim 1 in preparing a preparation for alleviating lactose intolerance.

9. The use according to claim 6, wherein: The bacterial powder contains a protective agent.

Images