A strain of durella and the exopolysaccharide produced by the strain and applications thereof

Abstract

This invention discloses a strain of *Drugella*, its produced polysaccharide, and its applications. The *Drugella* G3 strain of this invention has the preservation number CCTCC NO: M 2024137. Its extracellular polysaccharide TDG3, as a TLR4 / DC-SIGN dual receptor agonist, exhibits a significant effect in reducing body weight. The extracellular polysaccharide TDG3 of this invention can significantly reduce appetite, decrease food intake, reduce body weight, and reduce adipose tissue content in mice. It can also alleviate or prevent obesity-induced hepatic steatosis. It is safe and non-toxic, suitable for preparing lipid-lowering and weight-loss drugs, and has good clinical application value and broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of microbial extracellular polysaccharide technology, and relates to a strain of Durococcus and the extracellular polysaccharides it produces and their applications. Background Technology

[0002] Obesity affects approximately 19% of women and 14% of men worldwide and is associated with an increasing incidence rate. Anti-obesity drugs can alter biological processes affecting appetite and significantly improve outcomes such as type 2 diabetes, hypertension, and dyslipidemia. Bariatric surgery is the most effective treatment for morbid obesity, but we need less aggressive treatment options. An ideal weight-loss drug should possess the following characteristics: effectiveness and safety. Specifically, it should effectively reduce hunger and suppress food cravings, thereby significantly alleviating obesity symptoms and achieving a marked reduction in weight and body fat percentage. In terms of safety, the drug must ensure that it does not cause adverse side effects such as organ damage or cardiovascular disease while exerting its weight-loss effects, avoiding any potential threats to health. It should focus on reducing unhealthy excess adipose tissue while carefully protecting muscles and bones, ensuring a healthy and comprehensive weight-loss process. Furthermore, an ideal weight-loss drug should be convenient to use, meaning low dosing frequency and long-lasting effects. Ideally, it should fit people's daily routines, such as requiring medication only once a week, or even once a week for longer periods, to ensure that the weight loss process does not interfere with an individual's quality of life and well-being due to frequent medication use.

[0003] Weight-loss drugs currently on the market and in research can be classified into several types based on their mechanisms of action. Orlistat, for example, primarily works by blocking the absorption of dietary fat and increasing patients' acceptance of low-fat diets and snacks. However, orlistat use may be accompanied by a range of mild to moderate gastrointestinal discomforts, such as oily stools, diarrhea, abdominal pain, and even blood in the stool. More seriously, a few cases have been reported that it may cause serious liver adverse reactions, including cholelithiasis, cholestatic hepatitis, and even subacute liver failure. Another type of centrally acting drug, such as phentermine-topiramate and naltrexone-bupropion, achieves weight loss by regulating the appetite center in the brain. Approximately 20% of patients using these drugs experience constipation, while the incidence of other adverse reactions (such as paresthesia and nausea) varies depending on the type of drug. GLP-1 receptor agonist-based drugs, such as liraglutide and semaglutide, not only alter the central appetite regulation mechanism by mimicking the action of enteropancreatic hormones, but also provide various cardiometabolic weight loss benefits. However, these drugs are also accompanied by a range of adverse reactions, including nausea (incidence 28%-44%), diarrhea (21%-30%), and constipation (11%-24%).

[0004] In conclusion, although several weight-loss drugs have demonstrated good weight-loss effects in clinical practice, they are all accompanied by varying degrees of adverse reactions. Furthermore, not all patients experience sufficient weight loss with existing medications. Therefore, there is an urgent need to develop new weight-loss drugs and to provide new ideas for their research and development. Summary of the Invention

[0005] This invention provides a strain of Durococcus and the extracellular polysaccharide it produces, as well as its applications.

[0006] The Duganella sp. described in this invention is Duganella G3, which was deposited on January 18, 2024, at the China Center for Type Culture Collection (CCTCC) with accession number CCTCC NO: M 2024137, located at Wuhan University, Wuhan, China.

[0007] The cultivation method for the above-mentioned Duroc G3 is as follows: Duroc G3 is inoculated into a fermentation medium and cultured at a pH of 5-9 and a temperature of 26-32℃.

[0008] The fermentation medium described in this invention is a conventionally used culture medium for *Durga rotundifolia*, for example, a fermentation medium with the following formulation: carbon source 20–50 g / L, nitrogen source 1–4 g / L, NaH₂PO₄ 0.5–2 g / L, CaCl₂ 0.02–0.1 g / L, MgSO₄·7H₂O 0.1–0.5 g / L, FeSO₄·7H₂O 0.01–0.06 g / L, MnSO₄·H₂O 0.005–0.01 g / L, ZnCl₂ 0.01–0.02 g / L. The carbon source in the fermentation medium described in this invention is a conventionally used carbon source for *Durga rotundifolia*, such as one or more of glucose, sucrose, and starch.

[0009] The nitrogen source in the fermentation medium of the present invention is one or more of the nitrogen sources commonly used by Durococcus, such as potassium nitrate, sodium nitrate, ammonium nitrate, peptone, and yeast extract.

[0010] The extracellular polysaccharide described in this invention is extracellular polysaccharide TDG3, produced by the aforementioned Duroc G3, and composed of glucose, mannose, and galactose in a molar ratio of 3:2:1. Its glycosidic bond linkage is: 4)-β-D-Glcp-(1→4)[α-D-Manp-(1→2)]-β-D-Manp-(1→4)-β-D-Glcp-(1→3)-β-D-Galp-(1→4)-β-D-Glcp-(1→2), and its structural formula is: Where n = 100 to 100000.

[0011] The method for producing the above-mentioned extracellular polysaccharide TDG3 includes the following steps:

[0012] The fermentation broth of Durantalum G3 was diluted with water to remove proteins. Then, 2-3 times the volume of ethanol was added to the supernatant, the precipitate was collected by centrifugation, and dried to obtain pure extracellular polysaccharide TDG3.

[0013] The method for removing proteins described in this invention employs methods conventionally used in the art, such as one or more of the following: adding 0.05–0.2% NaOH, using a 20 nm–2 μm filter membrane for filtration, and using an ultrafiltration membrane with a molecular weight cutoff of 5 kD–50 kD.

[0014] In a specific embodiment of the present invention, the specific steps of the above-mentioned method for producing extracellular polysaccharide TDG3 are as follows: the fermentation broth of Duroc G3 is mixed with twice the volume of pure water, NaOH is added to make the final concentration 0.1% to 0.2%, boiled for 10 to 20 minutes, then filtered through a 1 μm filter membrane to precipitate, and finally 0.1% to 0.3% sodium acetate and 3 times the volume of ethanol are added and stirred evenly, the precipitate is collected by centrifugation and dried to obtain pure extracellular polysaccharide TDG3.

[0015] This invention provides the application of the above-mentioned extracellular polysaccharide TDG3 in the preparation of a drug for treating obesity.

[0016] The obesity described in this invention refers to obesity as commonly known in the art, and its contributing factors include, but are not limited to, environmental factors such as diet, lack of physical activity, ultra-processed foods, fast food, microbiome, and chemical pollutants. The obesity phenotypes described include, but are not limited to, subtypes such as metabolically healthy obesity, metabolically abnormal obesity, metabolically abnormal, normal weight, and sarcopenic obesity.

[0017] The medication for treating obesity described in this invention can be administered via intraperitoneal injection or subcutaneous injection.

[0018] The drug for treating obesity described in this invention can be administered to any obese animal. These animals include both human and non-human animals, such as pets or livestock.

[0019] The concentration and dosage of the drug for treating obesity described in this invention depend on the recipient's age, health and weight, treatment frequency and route of administration, etc.

[0020] The pharmaceutical carrier used in the drug for treating obesity described in this invention can be a pharmaceutical carrier conventionally used in the art, such as an isotonic NaCl solution, an isotonic glucose solution, or an isotonic solution containing a buffer system, such as PBS solution.

[0021] In a specific embodiment of the present invention, the pharmaceutical carrier used is 0.9% physiological saline.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) This invention is the first to discover a strain of Duroc G3, whose extracellular polysaccharide TDG3 can be used as a weight loss drug to effectively improve the obesity phenotype of mice. The extracellular polysaccharide TDG3 is safe and non-toxic, has strong efficacy, and has a good prospect for medicinal use.

[0024] (2) The extracellular polysaccharide TDG3 of the present invention can achieve weight loss by suppressing appetite and reducing energy intake;

[0025] (3) The extracellular polysaccharide TDG3 of the present invention can reduce excessive fat accumulation, has little effect on muscle components, and has no adverse effects on the liver and cardiovascular system.

[0026] (4) The extracellular polysaccharide TDG3 of the present invention is a dual receptor agonist of TLR4 / DC-SIGN. It can bind to TLR4 and DC-SIGN receptors, resulting in simultaneous activation of the two signaling pathways and has a significant effect on reducing body weight. Attached Figure Description

[0027] Figure 1 Infrared absorption spectrum of TDG3, an extracellular polysaccharide produced by Duroc G3.

[0028] Figure 2 This is a liquid chromatogram of the components determined after the extracellular polysaccharide TDG3 was derivatized. The components are labeled as: Man (mannose), Glc (glucose), and Gal (galactose).

[0029] Figure 3 Gas chromatogram of the extracellular polysaccharide TDG3 after methylation and acetylation.

[0030] Figure 4 The left image shows the heteronuclear single-quantum coherent NMR spectrum and the right image shows the heteronuclear multi-quantum correlation spectrum of the extracellular polysaccharide TDG3.

[0031] Figure 5 The images show representative body shapes of mice in each experimental group. ND represents the body shape of mice in the normal diet group, HFD represents the body shape of obese mice fed a high-fat diet, and HFD+LG and HFD+HG represent the body shape of obese mice fed a high-fat diet after intraperitoneal injection of TDG3 at doses of 2 mg / kg and 5 mg / kg, respectively, once a week for 3 consecutive weeks.

[0032] Figure 6 The graphs show changes in mouse skin composition, with the left graph showing changes in body weight, the middle graph showing changes in body fat, and the right graph showing changes in muscle mass.

[0033] Figure 7This is a graph showing the total food intake of mice in each experimental group during the 21-day experimental period.

[0034] Figure 8 MST analysis of the interactions between extracellular polysaccharide TDG3 and DC-SIGN, and between extracellular polysaccharide TDG3 and TLR4.

[0035] Figure 9 To evaluate the in vivo safety of the extracellular polysaccharide TDG3. Detailed Implementation

[0036] Unless otherwise specified, all technical and scientific terms used in this invention have the meaning commonly understood by one of ordinary skill in the art to which this invention pertains. The specific embodiments and examples described below are for illustrative purposes only and are not intended to limit the invention. Unless otherwise specified, the reagents or materials used in the following examples can be commercially available or synthesized by referring to existing methods. The invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0037] Example 1: Screening, 16S sequence identification, and fermentation purification of extracellular polysaccharides from Duroc G3.

[0038] 1. Screening for Duroc G3:

[0039] (1) The screening medium formula is as follows: KH2PO4 1g / L, CaCl2 0.1g / L, MgCl2·6H2O 0.3g / L, FeSO4 0.0125g / L, KNO3 2g / L, sucrose 20g / L, pH 7.2. For solid medium, 15g / L of agar needs to be added. The medium is sterilized at 121℃ for 20min.

[0040] (2) Screening method: Soil from Nanjing Garden was placed in a 2mL EP tube, 1mL of physiological saline was added, the mixture was shaken evenly, and centrifuged at 50g for 1min to remove the precipitated soil particles. 500μL of the supernatant was taken and centrifuged at 12000g for 3min. The supernatant was discarded, and the precipitated bacterial cells were then rinsed with 1mL of physiological saline, centrifuged, and finally dissolved in 200μL of physiological saline to prepare a soil leachate. The soil leachate was diluted and spread on solid agar plates and incubated at 28℃ for 2-3 days. After colonies grew, single colonies with surface viscous polysaccharides were selected based on their morphological characteristics, diluted and spread on a new solid agar plate, and incubated at 28℃. After colonies grew, single colonies were picked again for dilution and spread, and this process was repeated until the colonies growing on the solid agar plate had a uniform morphology. The fermentation potential was then tested using a liquid screening medium.

[0041] 2. Molecular identification: The 16S rDNA of the selected single-colony strain (see SEQ ID NO.1 in the sequence listing) was subjected to BLAST alignment. BLAST alignment showed a sequence similarity of 99.02% with *Duganella* PAMC 2743, identifying it as *Duganella* sp., and naming it *Duganella* G3.

[0042] 3. Production and purification method of extracellular polysaccharide TDG3 produced by Duroc G3:

[0043] (1) The fermentation liquid culture medium used was formulated as follows: sucrose 20-50 g / L, KNO3 1-4 g / L, NaH2PO4 0.5-2 g / L, CaCl2 0.02-0.1 g / L, MgSO4·7H2O 0.1-0.5 g / L, FeSO4·7H2O 0.01-0.06 g / L, MnSO4·H2O 0.005-0.01 g / L, ZnCl2 0.01-0.02 g / L, pH 7. The solid culture medium was prepared by adding 15 g / L agar powder to the liquid culture medium.

[0044] (2) Fermentation process: First, pick a single colony on a solid plate and culture it at 28℃ and 230rpm for 2 days to obtain a high-viability colony. Then, pick the colony into 10mL of liquid culture medium and culture it at 28℃ and 230rpm for 2 days as a seed liquid. Then, expand the fermentation by inoculating at a ratio of 2% and continue to culture for 2-3 days to obtain a high-viscosity fermentation liquid.

[0045] (3) Purification: The fermentation broth was purified by NaOH and filtration. The specific process was as follows: the obtained fermentation broth was mixed with two times the volume of pure water, NaOH was added to make the final concentration 0.1%, and the mixture was boiled for 20 minutes. The precipitate was then filtered through a 1 μm filter membrane. Finally, 0.2% sodium acetate and three times the volume of ethanol were added and stirred evenly. The precipitate was collected by centrifugation and dried to obtain pure extracellular polysaccharide TDG3.

[0046] Example 2: Structural analysis of extracellular polysaccharide TDG3

[0047] For the pure extracellular polysaccharide TDG3, its structure was analyzed and deduced using techniques such as infrared spectroscopy, high-performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance. The structural analysis is as follows:

[0048] The functional groups of the purified extracellular polysaccharide TDG3 were analyzed using a NICOLETIS 10 infrared scanner (Thermo Fisher Scientific). The specific testing procedure was as follows: A pressed potassium bromide blank was placed on the sample holder of the infrared scanner sample chamber. A reference background spectrum was collected, and then the sample to be tested was placed into the spectrometer for scanning. The sample dosage was 2–5 mg each time. The infrared test results are shown below. Figure 1 As shown, the pure extracellular polysaccharide TDG3 was measured at 3320, 2931, 1615, 1410, and 1023 cm⁻¹. -1 It exhibits a distinct absorption peak at 3320 cm⁻¹. -1 The broad absorption peak belongs to the hydroxyl groups in various environments within the polysaccharide molecule; 2931 cm⁻¹ -1 The absorption peak originates from the stretching and bending vibrations of CH in the sugar ring; 1615 cm⁻¹ -1 The absorption peak originates from hydrogen bonds formed between crystalline water and sugar; 1410 cm⁻¹ -1 The absorption peak originates from the OCO bond in the acetal group; 1023 cm⁻¹ -1 The absorption peak originates from the C-C bonds in the pyranose ring.

[0049] High-performance liquid chromatography (HPLC) was used to quantitatively analyze various monosaccharides present in pure extracellular polysaccharide TDG3. The procedure was as follows: TDG3 was completely hydrolyzed with trifluoroacetic acid, derivatized with PMP, extracted with chloroform, and filtered with aqueous phase. The resulting solution was then analyzed by HPLC using a Waters HPLC system (Waters Inc., USA) equipped with a Zorbax SB-Aq column (4.6 mm × 150 mm, Agilent Technologies, Inc., USA). Figure 2 The liquid chromatogram for the determination of monosaccharide components is provided by... Figure 2 It is known that the extracellular polysaccharide TDG3 is composed of glucose, mannose and galactose in a molar ratio of 3:2:1.

[0050] The glycosidic bond types of the extracellular polysaccharide TDG3 were analyzed using gas chromatography-mass spectrometry (GC-MS). The procedure was as follows: exposed hydroxyl groups in the polysaccharide were labeled using a methylation reaction; the polysaccharide was then hydrolyzed to break the glycosidic bonds, exposing the corresponding hydroxyl groups; these hydroxyl groups were then acetylated. After these steps, the polysaccharide was converted into various volatile, thermally stable monosaccharide derivatives. Gas chromatography (Thermo Scientific ISQ LT, USA) equipped with a TG-200MS column was used to separate monosaccharide derivatives with different numbers or spatial positions of acetyl groups, thereby identifying the types of glycosidic bonds in the polysaccharide. The GC results are shown below. Figure 3As shown, combined with mass spectrometry data, it can be seen that the extracellular polysaccharide TDG3 is composed of T-Manp with a peak time of 18.5 min, 1,4-linked Glcp with a peak time of 21.7 min, 1,3-linked Manp with a peak time of 21.9 min, and 1,2,4-linked Manp with a peak time of 24.1 min.

[0051] The linkage sequence of the extracellular polysaccharide TDG3 was analyzed using nuclear magnetic resonance (NMR). The procedure was as follows: TDG3 was partially hydrolyzed with trifluoroacetic acid, dissolved in D2O, and deuterated. TMSP was added as an internal standard. NMR analysis was performed using a Bruker Avance 500MHz analyzer (Bruker, Karlsruhe, Germany). The heteronuclear single-quantum coherence NMR (HSQC) and heteronuclear multi-quantum correlation (HMBC) spectra are shown below. Figure 4 As shown. And for TDG3 1 H NMR and 13 The C NMR shifts (ppm) were distributed, and the results are shown in Table 1.

[0052] Table 1 TDG3 1 H NMR and 13 C NMR shift (ppm)

[0053]

[0054] Example 3: Dose-dependent weight loss in mice after one week of administration of extracellular polysaccharide TDG3.

[0055] (1) Establishment of animal models:

[0056] The experimental animals were male C57BL / 6 mice, 6-8 weeks old, weighing 20±2g. They were housed under standard experimental conditions with a 12-hour light-12-hour dark cycle and free access to water and food. At the start of the study, the mice were randomly divided into 10 groups based on body weight. Group 1 maintained a normal diet (ND), while groups 2 through 10 were provided with a high-fat diet to induce an obesity model in mice. After 8 weeks, mice in group 2 (HFD) did not receive TDG3 injections, while mice in groups 3 through 10 received intraperitoneal injections of TDG3 at doses of 0.5, 1, 2, 5, 10, 20, 50, and 100 mg / kg, respectively.

[0057] (2) Mouse weight tracking

[0058] Data on changes in mouse body weight were measured and recorded one week after intraperitoneal injection of TDG3.

[0059] (3) Results Analysis

[0060] As shown in Table 2, after one week, both the CK and HFD groups showed a significant increase in body weight. However, obese mice injected intraperitoneally with 0.5 mg / kg of TDG3 showed a significantly smaller increase in body weight compared to the HFD group. Body weight began to decrease when the TDG3 injection dose reached 1 mg / kg. Furthermore, the decrease in body weight was dose-dependent within the dose ranges of 1 mg / kg, 2 mg / kg, and 5 mg / kg. When the TDG3 injection dose was further increased from 5 mg / kg, the decrease in body weight did not change significantly compared to the 5 mg / kg dose.

[0061] Table 2. Statistics on the change in mouse body weight relative to initial body weight one week later.

[0062]

[0063] Example 4: Effect of extracellular polysaccharide TDG3 on weight loss in obese mice after three weeks of continuous administration.

[0064] (1) Establishment of animal models:

[0065] The experimental animals were male C57BL / 6 mice, 6-8 weeks old, weighing 20±2g. They were housed under standard experimental conditions with a 12-hour light-12-hour dark cycle and free access to water and food. At the start of the study, the mice were randomly assigned to four groups based on body weight. Group I received a normal diet (ND), while groups II, III, and IV were given a high-fat diet (HFD). After 8 weeks, mice in groups III and IV were intraperitoneally injected with TDG3 at doses of 2 mg / kg (HFD+LG) and 5 mg / kg (HFD+HG), respectively, once weekly for 3 weeks.

[0066] (2) Tracking mouse weight and body fat

[0067] During the 21-day experiment, the weight of each mouse was measured daily, and the body fat and lean meat composition of the mice were quantified using a benchtop MRI scanner.

[0068] (3) Mouse feeding tracking

[0069] During the 21-day experiment, the food intake of each mouse was measured daily, and the total food intake of each mouse was calculated.

[0070] (4) Data Analysis

[0071] Data processing was performed using Graphpad Prism 6.0 software. One-way ANOVA was used for statistical analysis to compare multiple groups. A p-value < 0.05 was considered statistically significant.

[0072] (5) Results Analysis

[0073] like Figure 5 and Figure 6 As shown, intraperitoneal injection of TDG3 significantly reduced the obesity phenotype induced by a high-fat diet in mice, with little effect on muscle tissue content. Furthermore, according to... Figure 7 It can be seen that the food intake of mice was significantly reduced during the 21-day experimental period, proving that TDG3 reduces obesity in mice by reducing energy intake.

[0074] Example 5: Establishment of TLR4 / DC-SIGN dual-receptor glycoligand TDG3

[0075] (1) Establishment of cell model

[0076] The pmCherry-N1 plasmid encoding TLR4 or DC-SIGN was transfected into NIH-3T3 cells using the Lipofectamine 2000 transfection kit (Invitrogen). After 48 hours of incubation, the transfected cells were harvested.

[0077] (2) Micro-thermal surge analysis (MST)

[0078] After extracting cell membrane proteins, micro-thermal surge experiments were conducted using a Monolith NT.115 system at 20% excitation power and 90% MST power.

[0079] (3) Results Analysis

[0080] MST analysis results of the interactions between TDG3 and TLR4, and between TDG3 and DC-SIGN are as follows: Figure 8 As shown, TDG3 exhibits high affinity for both TLR4 and DC-SIGN, suggesting that it is a potential glycoligand for the TLR4 / DC-SIGN dual receptor.

[0081] Example 6: Safety Analysis of Extracellular Polysaccharide TDG3

[0082] (1) Establishment of animal models

[0083] Mice were administered TDG3 (200 mg / kg) intraperitoneally once weekly for three consecutive weeks. Safety was then assessed by measuring key biomarkers related to liver function and cardiovascular health in serum biochemical parameters. Data were processed using Graphpad Prism 6.0 software, and one-way ANOVA was used for statistical analysis of comparisons between multiple groups. A p-value < 0.05 was considered statistically significant.

[0084] (2) Results Analysis

[0085] Liver function and cardiovascular health-related biochemical markers were assessed, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine (Cre), urea (Urea), creatine kinase (CK), lactate dehydrogenase (LDH), albumin (ALB), and uric acid (UA). No significant changes were observed in these biomarkers. Figure 9 This demonstrates that TDG3 did not cause adverse effects on liver and cardiovascular function.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. Durococcus ( Duganella The strain (sp.) is *Duranthus* G3, with accession number CCTCC NO: M 2024137.

2. The method for culturing *Durgaea* according to claim 1, characterized in that, Specifically, *Durga niger* G3 was inoculated into a fermentation medium and cultured at a pH of 5–9 and a temperature of 26–32 °C. The fermentation medium composition was as follows: carbon source 20–50 g / L, nitrogen source 1–4 g / L, NaH2PO4 0.5–2 g / L, CaCl2 0.02–0.1 g / L, MgSO4·7H2O 0.1–0.5 g / L, FeSO4·7H2O 0.01–0.06 g / L, MnSO4·H2O 0.005–0.01 g / L, and ZnCl2 0.01–0.02 g / L.

3. The cultivation method according to claim 2, characterized in that, The carbon source is one or more of glucose, sucrose, and starch, and the nitrogen source is one or more of potassium nitrate, sodium nitrate, ammonium nitrate, peptone, and yeast extract.

4. The extracellular polysaccharide TDG3 produced by *Durantalum conyzoides* G3 according to claim 1, characterized in that, Composed of glucose, mannose, and galactose in a molar ratio of 3:2:1, with glycosidic bonds linked as follows: 4)-β-D-Glc p - (1→4)[α-D-Man p -(1→2)]-β-D-Man p - (1→4)-β-D-Glc p - (1→3)-β-D-Gal p - (1→4)-β-D-Glc p -(1→, its structural formula is: , where n = 100 ~ 100000.

5. The method for producing the extracellular polysaccharide TDG3 according to claim 4, characterized in that, Includes the following steps: The fermentation broth of Duroc G3 as described in claim 1 was diluted with water to remove protein. Then, 2-3 times the volume of ethanol was added to the supernatant, the precipitate was collected by centrifugation and dried to obtain pure extracellular polysaccharide TDG3.

6. The production method according to claim 5, characterized in that, The methods for removing proteins include one or more of the following: adding 0.05-0.2% NaOH, filtration using a 20nm-2μm filter membrane, and ultrafiltration using an ultrafiltration membrane with a molecular weight cutoff of 5kD-50kD.

7. The production method according to claim 6, characterized in that, Specifically, the fermentation broth of Duroc G3 was mixed with twice the volume of pure water, and NaOH was added to make the final concentration 0.1%~0.2%. The mixture was boiled for 10~20 min, and then the precipitate was filtered through a 1 μm filter membrane. Finally, 0.1%~0.3% sodium acetate and 3 times the volume of ethanol were added and stirred evenly. The precipitate was collected by centrifugation and dried to obtain pure extracellular polysaccharide TDG3.

8. The use of the extracellular polysaccharide TDG3 according to claim 4 in the preparation of a medicament for treating obesity.

9. The application according to claim 8, characterized in that, The drugs for treating obesity are administered via intraperitoneal or subcutaneous injection; they are administered to humans or non-human animals.

10. The application according to claim 8, characterized in that, The drug carriers used to treat obesity are isotonic NaCl solution, isotonic glucose solution, or isotonic solution containing a buffer system.

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