Fermentation method for xanthan gum

Abstract

The present invention relates to the technical field of microbial fermentation. Disclosed is a fermentation method for xanthan gum. The method comprises activating the Xanthomonas campestris strain, then culturing liquid seeds, and then inoculating the liquid seeds into a liquid fermentation medium to prepare xanthan gum. The method used for strain activation can effectively reduce the time for strain activation, and retains the strain activity of Xanthomonas campestris, which facilitates subsequent fermentation and production. The method for culturing liquid seed enables the Xanthomonas campestris strain in the liquid seeds to have a relatively high purity, relatively large strain density, and relatively high strain activity, and the total amount and concentration of the strain can meet fermentation requirements to the greatest extent. After being transferred to the liquid fermentation medium, the strain can grow rapidly. The method can produce xanthan gum at a low cost and with high efficiency by means of fermentation.

Description

A kind of fermentation method of xanthan gum

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on December 19, 2023, with application number CN202311758137.9 and invention name “A fermentation method for xanthan gum”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of microbial fermentation technology, and in particular to a xanthan gum fermentation method. Background Art

[0003] Xanthan gum, also known as xanthan gum or xanthan gum, is a water-soluble microbial exopolysaccharide produced by Xanthomonas campestris using carbohydrates as the primary raw material through aerobic fermentation. It is currently the world's largest microbial polysaccharide. Xanthan gum is an acidic extracellular heteropolysaccharide formed by aerobic fermentation of sugars by Xanthomonas campestris, cleaving 1,6-glycosidic bonds, opening side chains, and synthesizing linear chains along 1,4-linkages. Due to its unique macromolecular structure and colloidal properties, xanthan gum possesses excellent physical and chemical properties, such as suspending, emulsifying, thickening, pseudoplasticity, and thermal stability. It is widely used in various fields as a thickener, emulsifier, stabilizer, gelling agent, wetting agent, and film-forming agent, making it one of the most superior bio-glue products.

[0004] Xanthan gum possesses many properties, including: 1. Water solubility: Xanthan gum dissolves rapidly in water and possesses strong hydrophilicity. 2. Stability: The viscosity of xanthan gum solutions does not change significantly with temperature. The gum molecules undergo virtually no conformational changes in aqueous solutions between 20°C and 80°C, resulting in stable viscosity, even at low concentrations. 3. Suspension: Xanthan gum has an excellent suspending effect on insoluble solids and oil droplets. The gum molecules form super-bonded, ribbon-like helical copolymers in solution, creating a fragile, gel-like network structure that supports the morphology of solid particles, liquid droplets, and bubbles, demonstrating strong emulsification stabilization and high suspending capacity. 4. Pseudoplasticity: Aqueous xanthan gum solutions exhibit high viscosity under static or low shear conditions. Under high shear, the viscosity drops sharply, while the molecular structure remains unchanged. Upon removal of shear, the original viscosity is immediately restored, making it a highly effective thickener.

[0005] In industrial production, aerobic fermentation is performed using Xanthomonas campestris. After fermentation, cells are removed by centrifugation, followed by precipitation with water-miscible isopropyl alcohol, ethanol, or acetone. The pH is adjusted to neutral, and the product is dehydrated and dried. Xanthan gum production is influenced by reactor type, culture medium composition, fermentation conditions, and the strain of fermentation bacteria.

[0006] In fermentation production, the choice of carbon source and the C / N ratio have a significant impact on fermentation speed and cycle. Traditional culture medium formulations typically use glucose as the carbon source and beef extract or yeast extract powder as the nitrogen source, resulting in high production costs and little improvement in fermentation yield. Summary of the Invention

[0007] In order to solve the problems of high cost and low yield of xanthan gum liquid fermentation culture medium, the present application provides a xanthan gum fermentation method.

[0008] The technical solutions adopted in this application are as follows:

[0009] The present invention provides a xanthan gum fermentation culture medium, comprising a liquid seed culture medium and a liquid fermentation culture medium;

[0010] The composition of the liquid seed culture medium includes, by weight percentage, 1% corn starch, 0.5% industrial ammonium sulfate, 0.3% potassium dihydrogen phosphate, and a pH value of 7.0;

[0011] The liquid fermentation medium comprises, by weight percentage, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and 4.0%, 5.0%, 6.0%, 7.0%, or 8.0% corn starch;

[0012] Alternatively, the liquid fermentation medium comprises, by weight percentage, 5.0% corn starch, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and 0.5%, 1.0%, 1.5%, 2.0%, or 2.5% industrial ammonium sulfate.

[0013] The present invention provides a method for culturing liquid seeds of Xanthomonas campestris, comprising inoculating the Xanthomonas campestris into a liquid seed culture medium in the xanthan gum fermentation culture medium described in the above technical solution to perform strain activation and liquid seed culture to obtain liquid seeds;

[0014] The method for activating the strain comprises: campestris) lyophilized tubes were sterilized by wiping the tube surfaces with 75% alcohol cotton in a clean bench. The tops of the lyophilized tubes were evenly heated over the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to rupture the tube walls. The ruptures were knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the lyophilized tubes to completely dissolve the lyophilized bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed thoroughly. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in a slant test tube. The liquid test tubes and slant test tubes were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tubes was then inoculated into a 250 mL Erlenmeyer flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore activity.

[0015] The liquid seed culture is as follows: the bacterial liquid obtained by bacterial strain activation is inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium according to a 1% inoculation amount, and cultured in a constant temperature shaking incubator at 30° C. and 180 rpm for 24 hours to complete the liquid seed culture.

[0016] The present invention provides a xanthan gum fermentation method, which comprises activating Xanthomonas campestris strains, then performing liquid seed culture, and then inoculating the liquid seeds into a liquid fermentation medium to prepare xanthan gum.

[0017] The method for activating the strain includes: campestris) lyophilized tubes were sterilized by wiping the tube surface with 75% alcohol cotton in a clean bench. The top of the lyophilized tube was evenly heated over the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to rupture the tube wall. The ruptured area was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the lyophilized tube to completely dissolve the lyophilized bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed thoroughly. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in a slant test tube. The liquid test tube and slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL Erlenmeyer flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore activity. The invention can effectively save the activation time of the strain and maintain the strain activity of Xanthomonas campestris, which is beneficial to the subsequent fermentation production.

[0018] The liquid seed culture medium comprises, by weight, 1% corn starch, 0.5% industrial ammonium sulfate, and 0.3% potassium dihydrogen phosphate, with a pH of 7.0. A 1% inoculum of activated bacterial liquid is inoculated into a 250mL conical flask containing 100mL of the liquid seed culture medium and incubated in a constant temperature shaker at 30°C and 180 rpm for 24 hours to complete the liquid seed culture. Under these conditions, the Xanthomonas campestris strain in the liquid seed has high purity, high density, and high bacterial activity. The total amount and concentration can meet fermentation requirements to the greatest extent possible. After being transplanted into the liquid fermentation medium, the strain can grow rapidly.

[0019] Preferably, the method for preparing xanthan gum by inoculating liquid seeds into liquid fermentation medium comprises: inoculating the liquid seeds at an inoculum rate of 5% into a 250mL conical flask containing 100mL of liquid fermentation medium, and culturing at a constant temperature of 30°C and 180r / min in a shaking incubator for 72h; after the fermentation is completed, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation broth to dilute the fermentation broth, and then adding 3 times the volume of anhydrous ethanol to precipitate xanthan gum, centrifuging at 8000r / min for 15min, discarding the supernatant, retaining the precipitate, and then washing the precipitate twice with anhydrous ethanol, drying in a 60°C oven, grinding and weighing to obtain the fermentation product xanthan gum.

[0020] This dilution ratio is beneficial to the yield of the xanthan gum product, will not cause excessive burden on the use of anhydrous ethanol, and is beneficial to the quality of the xanthan gum product.

[0021] Preferably, the composition of the liquid fermentation medium includes, by weight percentage, 4.0% corn starch, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate and 0.1% potassium dihydrogen phosphate, and the pH value is 7.0.

[0022] The use of corn starch and industrial ammonium sulfate for fermentation can maintain a high productivity and rubber yield. At the same time, industrial ammonium sulfate, as a low-priced industrial raw material, is much lower than the price of peptone and corn steep liquor, which reduces production costs and is conducive to industrial production.

[0023] Preferably, the method for preparing xanthan gum by inoculating liquid seeds into a liquid fermentation medium comprises: inoculating the liquid seeds at a 5% inoculum into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and incubating the liquid in a shaker at 30° C. and 180 rpm for 72 hours; after fermentation, using an ethanol precipitation method, diluting the fermentation liquid by adding 3 times the volume of deionized water, then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000 rpm for 15 minutes, discarding the supernatant, retaining the precipitate, washing the precipitate twice with anhydrous ethanol, drying in a 60° C. oven, grinding, and weighing to obtain the fermentation product xanthan gum. This dilution ratio is beneficial to the yield of the xanthan gum product, does not impose an excessive burden on the amount of anhydrous ethanol used, and is beneficial to the quality of the xanthan gum product.

[0024] Preferably, the composition of the liquid fermentation medium includes, by weight percentage, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate and 4.0%, or 5.0%, or 6.0%, or 7.0%, or 8.0% corn starch; and the pH value of the liquid fermentation medium is 7.0.

[0025] Starting from the logarithmic growth phase, the use of a higher C / N ratio can promote the synthesis of xanthan gum. The appropriate carbon source concentration can stimulate the growth of Xanthomonas campestris, meet the nutritional needs, and is beneficial to the growth of the strain and xanthan gum synthesis.

[0026] Preferably, the method for preparing xanthan gum by inoculating liquid seeds into a liquid fermentation medium comprises: inoculating the liquid seeds at a 5% inoculum into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and incubating the liquid in a shaker at 30° C. and 180 rpm for 72 hours; after fermentation, using an ethanol precipitation method, diluting the fermentation liquid by adding 3 times the volume of deionized water, then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000 rpm for 15 minutes, discarding the supernatant, retaining the precipitate, washing the precipitate twice with anhydrous ethanol, drying in a 60° C. oven, grinding, and weighing to obtain the fermentation product xanthan gum. This dilution ratio is beneficial to the yield of the xanthan gum product, does not impose an excessive burden on the amount of anhydrous ethanol used, and is beneficial to the quality of the xanthan gum product.

[0027] Preferably, the liquid fermentation medium comprises, by weight, 5.0% corn starch, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and 0.5%, 1.0%, 1.5%, 2.0%, or 2.5% industrial ammonium sulfate; and the pH of the liquid fermentation medium is 7.0. Nitrogen source concentration significantly influences xanthan gum synthesis rate, gum concentration, and gum yield. Starting in the logarithmic growth phase, a higher C / N ratio can promote xanthan gum synthesis. An appropriate nitrogen source concentration can stimulate the secretion of xanthan gum from the cell wall, thereby increasing xanthan gum yield.

[0028] Preferably, the composition of the liquid fermentation medium includes, by weight percentage: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate and 0.1% potassium dihydrogen phosphate, and the pH value of the liquid fermentation medium is 7.0;

[0029] The method for preparing xanthan gum by inoculating liquid seeds into a liquid fermentation medium comprises: inoculating the liquid seeds at an inoculum size of 5%, 10%, 15%, 20%, or 25% into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and incubating the mixture in a shaker at 30°C and 180 rpm for 72 hours; after fermentation, using an ethanol precipitation method, diluting the fermentation broth by adding 3 volumes of deionized water, then adding 3 volumes of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000 rpm for 15 minutes, discarding the supernatant, and collecting the precipitate. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground, and weighed to obtain the fermentation product xanthan gum. An appropriate inoculum size is beneficial for improving xanthan gum yield. As fermentation proceeds with a high-concentration bacterial solution, the viscosity of the fermentation broth increases, the volumetric mass transfer coefficient decreases, and the oxygen supply capacity gradually decreases, the synthesis rate slows, and the yield decreases.

[0030] Preferably, the liquid fermentation medium comprises, by weight percentage, 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, and 0.1% potassium dihydrogen phosphate, and has a pH of 7.0;

[0031] The method for preparing xanthan gum by inoculating liquid seeds into a liquid fermentation medium comprises: inoculating the liquid seeds at an inoculum amount of 15% into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and culturing in a shaking incubator at 30° C. and 180 rpm for 48 hours, or 72 hours, or 96 hours, or 120 hours, or 144 hours; after the fermentation is completed, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation liquid to dilute the fermentation liquid, and then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000 rpm for 15 minutes, discarding the supernatant, retaining the precipitate, and then washing the precipitate twice with anhydrous ethanol, drying in a 60° C. oven, grinding and weighing to obtain the fermentation product xanthan gum.

[0032] Too long a fermentation time will reduce the xanthan gum yield. The carbon source in the liquid fermentation medium will be fully utilized. In order to survive, Xanthomonas campestris will use xanthan gum as a new carbon source. The gum yield will show a downward trend. Choosing the optimal fermentation time is conducive to improving the gum yield.

[0033] Preferably, the liquid fermentation medium comprises, by weight percentage, 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, and 0.1% potassium dihydrogen phosphate, and has a pH of 7.0;

[0034] The method for preparing xanthan gum by inoculating liquid seeds into a liquid fermentation medium comprises: inoculating the liquid seeds at a 15% inoculum into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and culturing the mixture in a shaker at 180 rpm for 120 hours at a temperature of 25°C, 30°C, 35°C, 40°C, or 50°C; after fermentation, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation broth to dilute the fermentation broth, and then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000 rpm for 15 minutes, discarding the supernatant, retaining the precipitate, washing the precipitate twice with anhydrous ethanol, drying in a 60°C oven, grinding, and weighing to obtain the fermentation product xanthan gum. Higher temperatures can increase the yield of xanthan gum and also have a certain effect on the pyruvic acid content of the xanthan gum product; excessively high temperatures in the early and middle stages of fermentation can cause rapid cell aging, and in the late fermentation stage, cell viability decreases, carbon source consumption slows, and the xanthan gum production rate slows. However, if the fermentation temperature is too low, the growth rate of the bacteria will slow down, the fermentation cycle will be extended, the cell metabolism will be slow, and the gum production rate will be reduced. Therefore, the appropriate fermentation temperature is conducive to increasing the yield of xanthan gum.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The strain activation method adopted in the present application can effectively save the strain activation time and maintain the strain activity of Xanthomonas campestris, which is beneficial to subsequent fermentation production;

[0037] The liquid seed culture method of the present application can ensure that the Xanthomonas campestris strain in the liquid seed has a high purity, a high strain density, and a high bacterial activity. The total amount and concentration can meet the fermentation requirements to the greatest extent. After being transplanted into the liquid fermentation medium, the strain can grow rapidly.

[0038] The present application can produce xanthan gum by fermentation at low cost and high efficiency.

[0039] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the following specifically cites the embodiments of the present application and provides a detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0041] FIG1 is a bar graph showing the rubber yield of Xanthomonas campestris at different passage times in Example 1;

[0042] FIG2 is a bar graph showing the corresponding gelatin yields of liquid fermentation medium with different corn starch contents in Example 2;

[0043] FIG3 is a bar graph showing the corresponding rubber yields of liquid fermentation medium containing different contents of industrial ammonium sulfate in Example 3;

[0044] FIG4 is a bar graph showing the rubber yield corresponding to different inoculation amounts in Example 4;

[0045] FIG5 is a bar graph showing the rubber yield corresponding to different fermentation times in Example 5;

[0046] FIG6 is a bar graph showing the rubber yields corresponding to different fermentation temperatures in Example 6. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0048] The present application provides a xanthan gum fermentation method, which comprises activating Xanthomonas campestris strains, then performing liquid seed culture, and then inoculating the liquid seeds into a liquid fermentation medium to prepare xanthan gum.

[0049] The experimental bacteria were Xanthomonas campestris as the starting strain, which appeared as round, smooth, light white colonies on the plate culture medium. The cells were thin rod-shaped, Gram-negative bacteria, and were plant pathogens.

[0050] Six examples and six comparative examples are provided below to illustrate that the method of the present application can reduce the production cost of xanthan gum and increase the yield of xanthan gum.

[0051] Example 1

[0052] 1) Bacteria activation

[0053] The freeze-dried tube containing Xanthomonas campestris was wiped with 75% alcohol cotton in a clean bench for disinfection. The top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to break the tube wall. The broken part was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the freeze-dried tube to completely dissolve the freeze-dried bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in the slant test tube. The liquid test tube and the slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h for passage to restore its activity.

[0054] Among them, a total of six groups of activated Xanthomonas campestris bacterial liquids were obtained, and the number of passages of each group was 2 generations, 4 generations, 6 generations, 8 generations, 10 generations and 12 generations respectively.

[0055] 2) Liquid seed culture

[0056] The liquid seed culture medium used is composed of 1% corn starch, 0.5% industrial ammonium sulfate, and 0.3% potassium dihydrogen phosphate by weight, and has a pH value of 7.0.

[0057] The activated Xanthomonas campestris bacteria were inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculation rate and cultured in a constant temperature shaker at 30°C and 180 rpm for 24 h to complete the liquid seed culture. It should be noted that the OD value of the liquid seed should be ensured. 600 A value of 0.8 indicates that the cell has grown to the logarithmic phase. In this embodiment, this condition is achieved after 24 hours of culture.

[0058] Based on the bacterial liquid of the six groups of activated Xanthomonas campestris strains, six groups of liquid seeds were cultured accordingly.

[0059] 3) Xanthan gum extraction

[0060] A liquid fermentation medium is obtained, wherein the liquid fermentation medium is composed of 4.0% corn starch, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate and 0.1% potassium dihydrogen phosphate, by weight percentage, and has a pH value of 7.0.

[0061] The liquid seeds were inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium at an inoculum rate of 5%, and cultured in a shaker at 30°C and 180 r / min for 72 hours. After the fermentation was completed, an ethanol precipitation method was used, and 3 times the volume of deionized water was added to the fermentation liquid to dilute the fermentation liquid. Then, 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum. The mixture was centrifuged at 8000 r / min for 15 minutes, the supernatant was discarded, and the precipitate was retained. The precipitate was then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum.

[0062] Based on the six groups of liquid seeds, six groups of fermentation products xanthan gum were obtained.

[0063] 4) Calculate the rubber yield

[0064] The xanthan gum yield is obtained by dividing the mass of xanthan gum by the mass of the fermentation liquid.

[0065] The bar graph of the rubber production rate corresponding to different passage numbers of Xanthomonas campestris is shown in FIG1 .

[0066] Example 2

[0067] 1) Bacteria activation

[0068] The freeze-dried tube containing Xanthomonas campestris was wiped with 75% alcohol cotton in a clean bench for disinfection. The top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to break the tube wall. The broken part was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the freeze-dried tube to completely dissolve the freeze-dried bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in the slant test tube. The liquid test tube and the slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore its activity.

[0069] 2) Liquid seed culture

[0070] The liquid seed culture medium used is composed of 1% corn starch, 0.5% industrial ammonium sulfate, and 0.3% potassium dihydrogen phosphate by weight, and has a pH value of 7.0.

[0071] The activated Xanthomonas campestris bacteria were inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculation rate and cultured in a constant temperature shaker at 30°C and 180 rpm for 24 h to complete the liquid seed culture. It should be noted that the OD value of the liquid seed should be ensured. 600 A value of 0.8 indicates that the cell has grown to the logarithmic phase. In this embodiment, this condition is achieved after 24 hours of culture.

[0072] 3) Optimization of corn starch content and extraction of xanthan gum

[0073] Five sets of liquid fermentation media were obtained, wherein the pH value of the liquid fermentation media was 7.0 and the composition of the liquid fermentation media was: corn starch, industrial ammonium sulfate, magnesium sulfate heptahydrate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate. The weight percentages of industrial ammonium sulfate, magnesium sulfate heptahydrate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate were 1.0%, 0.3%, 0.1%, and 0.1%, respectively. The weight percentages of corn starch in the five sets of liquid fermentation media were 4.0%, 5.0%, 6.0%, 7.0%, and 8.0%, respectively.

[0074] Xanthan gum was extracted based on the liquid fermentation culture medium of each group. The process of xanthan gum extraction for each group was as follows: liquid seeds were inoculated at an inoculum size of 5% into a 250mL conical flask containing 100mL of liquid fermentation culture medium, and cultured in a shaker at 30°C and 180r / min for 72 hours; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation liquid to dilute the fermentation liquid, and then 3 times the volume of anhydrous ethanol was added to precipitate the xanthan gum, and the mixture was centrifuged at 8000r / min for 15 minutes, the supernatant was discarded, and the precipitate was retained. The precipitate was then washed twice with anhydrous ethanol and dried and ground in a 60°C oven.

[0075] A total of five groups of fermentation products xanthan gum were obtained, and each group of xanthan gum was weighed.

[0076] 4) Calculate the rubber yield

[0077] The xanthan gum yield is obtained by dividing the mass of xanthan gum by the mass of the fermentation liquid.

[0078] The bar chart of the gum yield corresponding to liquid fermentation medium with different corn starch contents is shown in Figure 2.

[0079] Example 3

[0080] 1) Bacteria activation

[0081] The freeze-dried tube containing Xanthomonas campestris was wiped with 75% alcohol cotton in a clean bench for disinfection. The top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to break the tube wall. The broken part was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the freeze-dried tube to completely dissolve the freeze-dried bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in the slant test tube. The liquid test tube and the slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore its activity.

[0082] 2) Liquid seed culture

[0083] The composition of the liquid seed culture medium used is as follows: 1% corn starch, 0.5% industrial ammonium sulfate, 0.3% potassium dihydrogen phosphate, and a pH value of 7.0.

[0084] The activated Xanthomonas campestris bacteria were inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculation rate and cultured in a constant temperature shaker at 30°C and 180 rpm for 24 h to complete the liquid seed culture. It should be noted that the OD value of the liquid seed should be ensured. 600 A value of 0.8 indicates that the cell has grown to the logarithmic phase. In this embodiment, this condition is achieved after 24 hours of culture.

[0085] 3) Optimization of industrial ammonium sulfate content

[0086] Five sets of liquid fermentation media were obtained, wherein the pH value of the liquid fermentation media was 7.0 and the composition of the liquid fermentation media was: corn starch, industrial ammonium sulfate, magnesium sulfate heptahydrate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate. The weight percentages of corn starch, magnesium sulfate heptahydrate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate were 5.0%, 0.3%, 0.1%, and 0.1%, respectively. The weight percentages of industrial ammonium sulfate in the five sets of liquid fermentation media were 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%, respectively.

[0087] Xanthan gum was extracted based on the liquid fermentation culture medium of each group. The process of xanthan gum extraction in each group included: inoculating liquid seeds at an inoculum size of 5% into a 250mL conical flask containing 100mL of liquid fermentation culture medium, and culturing in a constant temperature shaker at 30°C and 180r / min for 72 hours; after the fermentation, using the ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation liquid to dilute the fermentation liquid, and then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000r / min for 15 minutes, discarding the supernatant, retaining the precipitate, and then washing the precipitate twice with anhydrous ethanol, and drying and grinding in a 60°C oven.

[0088] A total of five groups of fermentation products xanthan gum were obtained, and each group of xanthan gum was weighed.

[0089] 4) Calculate the rubber yield

[0090] The xanthan gum yield is obtained by dividing the mass of xanthan gum by the mass of the fermentation liquid.

[0091] The bar chart of the rubber yield corresponding to liquid fermentation medium with different industrial ammonium sulfate contents is shown in Figure 3.

[0092] Example 4

[0093] 1) Bacteria activation

[0094] The freeze-dried tube containing Xanthomonas campestris was wiped with 75% alcohol cotton in a clean bench for disinfection. The top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to break the tube wall. The broken part was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the freeze-dried tube to completely dissolve the freeze-dried bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in the slant test tube. The liquid test tube and the slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore its activity.

[0095] 2) Liquid seed culture

[0096] The composition of the liquid seed culture medium used is as follows: 1% corn starch, 0.5% industrial ammonium sulfate, 0.3% potassium dihydrogen phosphate, and a pH value of 7.0.

[0097] The activated Xanthomonas campestris bacteria were inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculation rate and cultured in a constant temperature shaker at 30°C and 180 rpm for 24 h to complete the liquid seed culture. It should be noted that the OD value of the liquid seed should be ensured. 600 A value of 0.8 indicates that the cell has grown to the logarithmic phase. In this embodiment, this condition is achieved after 24 hours of culture.

[0098] 3) Optimization of fermentation conditions and inoculum size and xanthan gum extraction

[0099] There are five groups of liquid fermentation culture media used. The compositions of the liquid fermentation culture media are as follows, by weight percentage: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and a pH value of 7.0.

[0100] The first group of liquid seeds was inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium at a 5% inoculum rate, and cultured in a constant temperature shaker at 30°C and 180 r / min for 72 hours. After the fermentation was completed, the ethanol precipitation method was used to add 3 times the volume of deionized water to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum. The broth was centrifuged at 8000 r / min for 15 minutes, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the first group of fermentation products, xanthan gum, and weighed.

[0101] The second group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 10%, and cultured in a constant temperature shaker at 30°C and 180r / min for 72h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the second group of fermentation products xanthan gum, and weighed.

[0102] The third group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 30°C and 180r / min for 72h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the third group of fermentation products xanthan gum, and weighed.

[0103] The fourth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 20%, and cultured in a constant temperature shaker at 30°C and 180r / min for 72h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fourth group of fermentation products xanthan gum, and weighed.

[0104] The fifth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 25%, and cultured in a constant temperature shaker at 30°C and 180r / min for 72h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fifth group of fermentation products xanthan gum, and weighed.

[0105] 4) Calculate the rubber yield

[0106] The xanthan gum yield is obtained by dividing the mass of xanthan gum by the mass of the fermentation liquid.

[0107] The bar chart of rubber yield corresponding to different inoculation amounts is shown in Figure 4.

[0108] Example 5

[0109] 1) Bacteria activation

[0110] The freeze-dried tube containing Xanthomonas campestris was wiped with 75% alcohol cotton in a clean bench for disinfection. The top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to break the tube wall. The broken part was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the freeze-dried tube to completely dissolve the freeze-dried bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in the slant test tube. The liquid test tube and the slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore its activity.

[0111] 2) Liquid seed culture

[0112] The composition of the liquid seed culture medium used is as follows: 1% corn starch, 0.5% industrial ammonium sulfate, 0.3% potassium dihydrogen phosphate, and a pH value of 7.0.

[0113] The activated Xanthomonas campestris bacteria were inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculation rate and cultured in a constant temperature shaker at 30°C and 180 rpm for 24 h to complete the liquid seed culture. It should be noted that the OD value of the liquid seed should be ensured. 600 A value of 0.8 indicates that the cell has grown to the logarithmic phase. In this embodiment, this condition is achieved after 24 hours of culture.

[0114] 3) Fermentation conditions, fermentation time optimization and xanthan gum extraction

[0115] There are five groups of liquid fermentation culture media used. The compositions of the liquid fermentation culture media are as follows, by weight percentage: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and a pH value of 7.0.

[0116] The first group of liquid seeds was inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium at a 15% inoculum rate, and cultured in a constant temperature shaker at 30°C and 180 r / min for 48 hours. After the fermentation was completed, the ethanol precipitation method was used to add 3 times the volume of deionized water to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum. The broth was centrifuged at 8000 r / min for 15 minutes, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the first group of fermentation products, xanthan gum, and weighed.

[0117] The second group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 30°C and 180r / min for 72h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the second group of fermentation products xanthan gum, and weighed.

[0118] The third group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 30°C and 180r / min for 96h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the third group of fermentation products xanthan gum, and weighed.

[0119] The fourth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 30°C and 180r / min for 120h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fourth group of fermentation products xanthan gum, and weighed.

[0120] The fifth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 30°C and 180r / min for 144h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fifth group of fermentation products xanthan gum, and weighed.

[0121] 4) Calculate the rubber yield

[0122] The xanthan gum yield is obtained by dividing the mass of xanthan gum by the mass of the fermentation liquid.

[0123] The bar chart of the rubber yield corresponding to different fermentation times is shown in Figure 5.

[0124] Example 6

[0125] 1) Bacteria activation

[0126] The freeze-dried tube containing Xanthomonas campestris was wiped with 75% alcohol cotton in a clean bench for disinfection. The top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp. Two drops of sterile distilled water were dripped into the heated area to break the tube wall. The broken part was knocked off with tweezers, and 0.5 mL of liquid seed culture medium was pipetted into the freeze-dried tube to completely dissolve the freeze-dried bacterial powder. The dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed. One drop of bacterial suspension remaining in the pipet was transferred to the solid culture medium in the slant test tube. The liquid test tube and the slant test tube were placed in an incubator and cultured statically until the bacterial solution became turbid or colonies grew on the slant surface. The bacterial solution cultured in the liquid test tube was then inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 rpm for 72 h. The culture was passaged twice to restore its activity.

[0127] 2) Liquid seed culture

[0128] The liquid seed culture medium used is composed of 1% corn starch, 0.5% industrial ammonium sulfate, and 0.3% potassium dihydrogen phosphate by weight, and has a pH value of 7.0.

[0129] The activated Xanthomonas campestris bacterial liquid was inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum size and cultured in a constant temperature shaker at 30°C and 180 r / min for 24 h to complete the liquid seed culture. It should be noted that the OD 600 value of the liquid seed must be 0.8, that is, it has grown to the logarithmic phase. In this embodiment, this condition was achieved after 24 h of culture.

[0130] 3) Fermentation conditions: Fermentation temperature optimization and xanthan gum extraction

[0131] There are six groups of liquid fermentation culture media used. The compositions of the liquid fermentation culture media are as follows by weight: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and a pH value of 7.0.

[0132] The first group of liquid seeds was inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium at a 15% inoculum rate, and cultured in a constant temperature shaker at 25°C and 180 r / min for 120 hours. After the fermentation was completed, the ethanol precipitation method was used to add 3 times the volume of deionized water to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum. The mixture was centrifuged at 8000 r / min for 15 minutes, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the first group of fermentation products, xanthan gum, and weighed.

[0133] The second group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at a 15% inoculum rate, and cultured in a constant temperature shaker at 30°C and 180r / min for 120h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the second group of fermentation products xanthan gum, and weighed.

[0134] The third group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 35°C and 180r / min for 120h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the third group of fermentation products xanthan gum, and weighed.

[0135] The fourth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 40°C and 180r / min for 120h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fourth group of fermentation products xanthan gum, and weighed.

[0136] The fifth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 45°C and 180r / min for 120h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fifth group of fermentation products xanthan gum, and weighed.

[0137] The sixth group of liquid seeds was inoculated into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculum size of 15%, and cultured in a constant temperature shaker at 50°C and 180r / min for 120h; after the fermentation was completed, the ethanol precipitation method was used, 3 times the volume of deionized water was added to the fermentation broth to dilute the fermentation broth, and then 3 times the volume of anhydrous ethanol was added to precipitate xanthan gum, centrifuged at 8000r / min for 15min, the supernatant was discarded, and the precipitate was retained. The precipitate was then washed twice with anhydrous ethanol, dried, ground and weighed in a 60°C oven to obtain the sixth group of fermentation products xanthan gum, and weighed.

[0138] 4) Calculate the rubber yield

[0139] The xanthan gum yield is obtained by dividing the mass of xanthan gum by the mass of the fermentation liquid.

[0140] The bar chart of rubber yield corresponding to different fermentation temperatures is shown in Figure 6.

[0141] Comparative Example 1

[0142] This comparative example provides a method for preparing a xanthan gum liquid fermentation medium in the prior art, which is as follows:

[0143] 1) Culture medium preparation

[0144] The liquid seed culture medium comprises 4% starch, 0.8% soybean protein, and 0.2% CaCO3 by weight, and has a pH of 7.4.

[0145] The liquid fermentation medium comprises 4% starch, 0.8% soybean protein, and 0.2% CaCO3 by weight, and has a pH of 7.4.

[0146] 2) Fermentation preparation of xanthan gum

[0147] Xanthomonas campestris is inoculated into a liquid seed culture medium, and the activated seed liquid is inoculated into a 250 mL conical flask containing 75 mL of liquid fermentation medium at a rate of 5%. The flask is cultured at 30°C and 180 rpm in a shaking incubator for 96 hours. After the fermentation is completed, an ethanol precipitation method is used to dilute the fermentation broth by adding 3 times the volume of deionized water, and then 3 times the volume of anhydrous ethanol is added to precipitate xanthan gum. The broth is centrifuged at 8000 rpm for 15 minutes, the supernatant is discarded, and the precipitate is retained. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum, which is also weighed.

[0148] Comparative Example 2

[0149] This comparative example provides a method for preparing a xanthan gum liquid fermentation medium in the prior art, which is as follows:

[0150] 1) Culture medium preparation

[0151] The liquid seed culture medium comprises 4% starch, 0.8% corn yellow powder, and 0.2% CaCO3 by weight, and has a pH value of 7.4.

[0152] The liquid fermentation culture medium comprises 4% starch, 0.8% corn yellow powder, 0.2% CaCO3, 10% alkaline protein hydrolysate, and has a pH of 8 by weight.

[0153] 2) Enzymatic hydrolysis of corn yellow powder

[0154] The enzymatic hydrolysis reaction was carried out using 4.00 g of corn yellow powder, a liquid-to-solid ratio of 10 mL / g, an enzyme dosage of 2.5 kU / g, a hydrolysis temperature of 50°C, and an appropriate hydrolysis pH. During the experiment, dilute HCl and NaOH solutions were added to maintain a constant pH in the reaction system. The hydrolysis was continued for 4 hours, and the pH of the hydrolyzate was adjusted to 7.0. The enzyme was inactivated in a boiling water bath for 15 minutes, and solids were removed by centrifugation at 5000 rpm for 15 minutes. The hydrolyzate was then diluted to 50 mL to obtain an 80 g / L corn yellow powder hydrolyzate.

[0155] 3) Fermentation preparation of xanthan gum

[0156] A 10% addition amount of corn yellow powder enzymatic hydrolysate is added to a xanthan gum liquid fermentation medium (the mass concentration of corn yellow powder is 8 g / L), and a 5% inoculum amount of Xanthomonas campestris seed liquid is inoculated into a 250 mL conical flask containing 75 mL of liquid fermentation medium, and cultured in a shaking incubator at 30°C and 180 r / min for 96 hours. After the fermentation is completed, an ethanol precipitation method is adopted, 3 times the volume of deionized water is added to the fermentation liquid to dilute the fermentation liquid, and then 3 times the volume of anhydrous ethanol is added to precipitate xanthan gum, and the mixture is centrifuged at 8000 r / min for 15 minutes, the supernatant is discarded, and the precipitate is retained. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum, which is also weighed.

[0157] Comparative Example 3

[0158] This comparative example provides a method for preparing a xanthan gum liquid fermentation medium in the prior art, which is as follows:

[0159] 1) Culture medium preparation

[0160] The liquid seed culture medium comprises 5% starch, 1.0% corn starch, and 0.2% CaCO3 by weight, and has a pH of 7.4.

[0161] The liquid fermentation medium comprises 5% starch, 1.0% corn yellow powder, 0.2% CaCO3 and 10% neutral protein hydrolysate by weight, and has a pH of 7.

[0162] 2) Enzymatic hydrolysis of corn yellow powder

[0163] The enzymatic hydrolysis reaction was carried out using 5.00 g of corn yellow powder, a liquid-to-solid ratio of 10 mL / g, an enzyme dosage of 2.5 kU / g, a hydrolysis temperature of 50°C, and an appropriate hydrolysis pH. During the experiment, dilute HCl and NaOH solutions were added to maintain a constant pH in the reaction system. The hydrolysis was continued for 4 hours, and the pH of the hydrolyzate was adjusted to 7.0. The enzyme was inactivated in a boiling water bath for 15 minutes, and solids were removed by centrifugation at 5000 rpm for 15 minutes. The hydrolyzate was then diluted to 50 mL to obtain a 100 g / L corn yellow powder hydrolyzate.

[0164] 3) Fermentation preparation of xanthan gum

[0165] A 10% addition amount of corn yellow powder enzymatic hydrolysate is added to a xanthan gum liquid fermentation medium (the mass concentration of corn yellow powder is 10 g / L), and a 10% inoculum amount of Xanthomonas campestris seed liquid is inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and cultured in a shaking incubator at 40°C and 180 r / min for 120 h. After the fermentation is completed, an ethanol precipitation method is adopted, 3 times the volume of deionized water is added to the fermentation liquid to dilute the fermentation liquid, and then 3 times the volume of anhydrous ethanol is added to precipitate xanthan gum, and the mixture is centrifuged at 8000 r / min for 15 min, the supernatant is discarded, and the precipitate is retained. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum, which is also weighed.

[0166] Comparative Example 4

[0167] This comparative example provides a method for preparing a xanthan gum liquid fermentation medium in the prior art, which is as follows:

[0168] 1) Culture medium preparation

[0169] The liquid seed culture medium comprises starch 6%, corn yellow powder 1.2%, CaCO3 0.2% by weight, and has a pH of 7.4.

[0170] The liquid fermentation medium comprises 6% starch, 1.2% corn yellow powder, 0.2% CaCO3, 10% acidic protein hydrolysate, and has a pH of 3.

[0171] 2) Enzymatic hydrolysis of corn yellow powder

[0172] The enzymatic hydrolysis reaction was carried out using 6.00 g of corn yellow powder, a liquid-to-solid ratio of 10 mL / g, an enzyme dosage of 2.5 kU / g, a hydrolysis temperature of 50°C, and an appropriate hydrolysis pH. During the experiment, dilute HCl and NaOH solutions were added to maintain a constant pH in the reaction system. The hydrolysis was continued for 4 hours, and the pH of the hydrolyzate was adjusted to 7.0. The enzyme was inactivated in a boiling water bath for 15 minutes, and solids were removed by centrifugation at 5000 rpm for 15 minutes. The hydrolyzate was then diluted to 50 mL to obtain a 120 g / L corn yellow powder hydrolyzate.

[0173] 3) Fermentation preparation of xanthan gum

[0174] A 10% addition amount of corn yellow powder enzymatic hydrolysate is added to a xanthan gum liquid fermentation medium (the mass concentration of corn yellow powder is 12 g / L), and a 10% inoculum amount of Xanthomonas campestris seed liquid is inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and cultured in a shaking incubator at 40°C and 180 r / min for 120 h. After the fermentation is completed, an ethanol precipitation method is adopted, 3 times the volume of deionized water is added to the fermentation liquid to dilute the fermentation liquid, and then 3 times the volume of anhydrous ethanol is added to precipitate xanthan gum, and the mixture is centrifuged at 8000 r / min for 15 min, the supernatant is discarded, and the precipitate is retained. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum, which is also weighed.

[0175] Comparative Example 5

[0176] This comparative example provides a method for preparing a xanthan gum liquid fermentation medium in the prior art, which is as follows:

[0177] 1) Culture medium preparation

[0178] The composition of the liquid seed culture medium is as follows by weight: 7% starch, 1.4% corn starch, 0.2% CaCO3, and a pH of 7.4.

[0179] The composition of the liquid fermentation medium is as follows by weight: 7% starch, 1.4% corn yellow powder, 0.2% CaCO3, 10% acidic protein hydrolysate, and pH 3.

[0180] 2) Enzymatic hydrolysis of corn yellow powder

[0181] The enzymatic hydrolysis reaction was carried out using 7.00 g of corn yellow powder, a liquid-to-solid ratio of 10 mL / g, an enzyme dosage of 2.5 kU / g, a hydrolysis temperature of 50°C, and an appropriate hydrolysis pH. During the experiment, dilute HCl and NaOH solutions were added to maintain a constant pH in the reaction system. The hydrolysis was continued for 4 hours, and the pH of the hydrolyzate was adjusted to 7.0. The enzyme was inactivated in a boiling water bath for 15 minutes, and solids were removed by centrifugation at 5000 rpm for 15 minutes. The hydrolyzate was then diluted to 50 mL to obtain a 140 g / L corn yellow powder hydrolyzate.

[0182] 3) Fermentation preparation of xanthan gum

[0183] A 10% addition amount of corn yellow powder enzymatic hydrolysate is added to a xanthan gum liquid fermentation medium (the mass concentration of corn yellow powder is 14 g / L), and a 10% inoculum amount of Xanthomonas campestris seed liquid is inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and cultured in a shaking incubator at 40°C and 180 r / min for 120 h. After the fermentation is completed, an ethanol precipitation method is adopted, 3 times the volume of deionized water is added to the fermentation liquid to dilute the fermentation liquid, and then 3 times the volume of anhydrous ethanol is added to precipitate xanthan gum, and the mixture is centrifuged at 8000 r / min for 15 min, the supernatant is discarded, and the precipitate is retained. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum, which is also weighed.

[0184] Comparative Example 6

[0185] This comparative example provides a method for preparing a xanthan gum liquid fermentation medium in the prior art, which is as follows:

[0186] 1) Culture medium preparation

[0187] The composition of the liquid seed culture medium is as follows by weight: 8% starch, 1.6% corn starch, 0.2% CaCO3, and a pH of 7.4.

[0188] The composition of the liquid fermentation medium is as follows by weight: 8% starch, 1.6% corn yellow powder, 0.2% CaCO3, 10% acidic proteinase hydrolysate, and pH 3.

[0189] 2) Enzymatic hydrolysis of corn yellow powder

[0190] The enzymatic hydrolysis reaction was carried out using 8.00 g of corn yellow powder, a liquid-to-solid ratio of 10 mL / g, an enzyme dosage of 2.5 kU / g, a hydrolysis temperature of 50°C, and an appropriate hydrolysis pH. During the experiment, dilute HCl and NaOH solutions were added to maintain a constant pH in the reaction system. The hydrolysis was continued for 4 h. The pH of the hydrolyzate was adjusted to 7.0, and the enzyme was inactivated in a boiling water bath for 15 min. The solids were removed by centrifugation at 5000 rpm for 15 min, and the hydrolyzate was diluted to 50 mL to obtain a 160 g / L corn yellow powder hydrolyzate.

[0191] 3) Fermentation preparation of xanthan gum

[0192] A 10% addition amount of corn yellow powder enzymatic hydrolysate is added to a xanthan gum liquid fermentation medium (the mass concentration of corn yellow powder is 16 g / L), and a 10% inoculum amount of Xanthomonas campestris seed liquid is inoculated into a 250 mL conical flask containing 100 mL of liquid fermentation medium, and cultured in a shaking incubator at 40°C and 180 r / min for 120 h. After the fermentation is completed, an ethanol precipitation method is adopted, 3 times the volume of deionized water is added to the fermentation liquid to dilute the fermentation liquid, and then 3 times the volume of anhydrous ethanol is added to precipitate xanthan gum, and the mixture is centrifuged at 8000 r / min for 15 min, the supernatant is discarded, and the precipitate is retained. The precipitate is then washed twice with anhydrous ethanol, dried in a 60°C oven, ground and weighed to obtain the fermentation product xanthan gum, which is also weighed.

[0193] The rubber yields of Examples 1-6 are shown in Table 1. Examples 1-6 using the method of the present application are compared with Comparative Examples 1-6, with the rubber yield being the comparison parameter, as shown in Table 2.

[0194] Example 1 shows the xanthan gum yield of Xanthomonas campestris in liquid fermentation medium after 12 passages. As shown in Table 1, the xanthan gum yields of Xanthomonas campestris in liquid fermentation medium containing 4.0% corn starch, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% potassium dihydrogen phosphate and 0.1% potassium dihydrogen phosphate at a pH of 7.0 are 3.854%, 3.797%, 3.811%, 3.901%, 3.827% and 3.790%, respectively, with an average value of 3.830%. As shown in Tables 1 and 2, the xanthan gum yields of the same Xanthomonas campestris in Comparative Example 1 are 3.854%, 3.797%, 3.811%, 3.901%, 3.827% and 3.790%, respectively, with an average value of 3.830%. campestris was used to prepare xanthan gum in different liquid fermentation media and fermentation conditions, and the gum yield was 3.291%. The average gum yield of Example 1 (3.830%) was 16.38% higher than that of Comparative Example 1, indicating that Xanthomonas campestris can achieve a higher gum yield using the liquid fermentation medium components and fermentation conditions in Example 1, and can be stably inherited.

[0195] By optimizing the corn starch in the liquid fermentation medium in Example 2, it was found that when the liquid fermentation medium consisted of 5.0% corn starch, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, and 0.1% potassium dihydrogen phosphate, and the pH value was 7.0, the gum yield of (Xanthomonas campestris) could be increased from the original 3.830% to 4.062%, an increase of 6.01% in gum yield. As shown in Tables 1 and 2, the same Xanthomonas campestris strain in Comparative Example 2 produced xanthan gum under different liquid fermentation media and fermentation conditions, and the gum yield was 1.614%. The highest gum yield in Example 2 (4.062%) was 151.67% higher than that in Comparative Example 2, indicating that the strain can achieve a higher gum yield by utilizing the liquid fermentation medium components and fermentation conditions in Example 2.

[0196] By optimizing the industrial ammonium sulfate in the liquid fermentation medium in Example 3, it was found that when the liquid fermentation medium contained 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, and 0.1% potassium dihydrogen phosphate, and the pH was 7.0, the gum yield of Xanthomonas campestris was increased from the original 3.830% to 4.172%, an increase of 8.88%. As shown in Tables 1 and 2, the same Xanthomonas campestris in Comparative Example 3 was used to prepare xanthan gum under different liquid fermentation media and fermentation conditions, and the gum yield was 2.366%. The highest gum yield (4.172%) in Example 3 was 76.33% higher than that in Comparative Example 3, indicating that the strain can achieve a higher gum yield by utilizing the liquid fermentation medium components and fermentation conditions in Example 3.

[0197] Through the optimization of the liquid seed inoculum amount inoculated into the liquid fermentation medium in Example 4, it was found that when the liquid seed inoculum amount was 15%, the gum yield of (Xanthomonas campestris) could be increased from the original 3.830% to 4.171%, an increase of 8.88%; as shown in Tables 1 and 2, the same wild campestris Xanthomonas campestris in Comparative Example 4 was used to prepare xanthan gum under different liquid fermentation media and fermentation conditions, and the gum yield was 2.501%. The highest gum yield in Example 4 (4.171%) was 66.77% higher than that of Comparative Example 4, indicating that the strain can achieve a higher gum yield by utilizing the liquid fermentation medium components and fermentation conditions in Example 4.

[0198] Through the optimization of the fermentation time in Example 5, it was found that when the fermentation time was 120 h, the gum yield of Xanthomonas campestris could be increased from the original 3.830% to 4.203%, an increase of 9.66%. As shown in Tables 1 and 2, the same Xanthomonas campestris in Comparative Example 5 was used to prepare xanthan gum under different liquid fermentation media and fermentation conditions, and the gum yield was 2.437%. The highest gum yield (4.203%) in Example 5 was 72.47% higher than that of Comparative Example 5, indicating that the strain can achieve a higher gum yield by utilizing the liquid fermentation medium components and fermentation conditions in Example 5.

[0199] Through the optimization of the fermentation temperature in Example 6, it was found that when the fermentation temperature was 40°C, the gum yield of Xanthomonas campestris could be increased from the original 3.830% to 4.342%, an increase of 13.32%, with the largest increase in gum yield. As shown in Tables 1 and 2, the same Xanthomonas campestris in Comparative Example 6 was used to prepare xanthan gum under different liquid fermentation media and fermentation conditions, and the gum yield was 1.944%. The highest gum yield in Example 6 (4.342%) was 123.35% higher than that of Comparative Example 6, indicating that the strain can achieve a higher gum yield using the liquid fermentation medium components and fermentation conditions in Example 6. In summary, the gum yields of Examples 1-6 were all higher than those of Comparative Examples 1-6, and Example 6 increased the original gum yield of Xanthomonas campestris to the greatest extent, with the most significant improvement effect. Compared with Comparative Examples 1-6, Example 6 has more advantages and is more suitable for fermentation scale-up production.

[0200] Table 1 Rubber yield of Examples 1-6

[0201] Table 2 Comparison of rubber yields of Examples 1-6 and Comparative Examples 1-6

[0202] As shown in FIG1 , the technical effect obtained in Example 1 shows that the xanthan gum yield of Xanthomonas campestris in liquid fermentation medium is stable at about 3.830% after 12 passages, and the bacteria has good genetic stability and can be used for industrial scale-up production.

[0203] As shown in Figure 2 of the results obtained in Example 2 and Figure 3 of the results obtained in Example 3, the present invention uses cheap raw materials, corn starch and industrial ammonium sulfate, as fermentation substrates. The xanthan gum yield of Xanthomonas campestris under unoptimized culture medium substrate content is about 3.830%. In Example 2, after optimizing the corn starch content, the xanthan gum yield continues to increase with the increase of corn starch content. When the corn starch addition amount is 5.0%, the xanthan gum yield of Xanthomonas campestris reaches the highest, which is 4.062%. As the corn starch concentration increases, the bacterial concentration continues to increase. When it exceeds a certain value, it leads to insufficient dissolved oxygen, reduced bacterial activity, and the gel yield begins to decrease continuously. Therefore, the present invention method determines that the optimal addition amount of corn starch is 5.0%. In Example 3, after optimizing the industrial ammonium sulfate content, the rubber production rate continued to increase with the increase in industrial ammonium sulfate content. When the industrial ammonium sulfate content reached 1.5%, the rubber production rate of Xanthomonas campestris reached its highest level, reaching 4.172%. When the concentration of industrial ammonium sulfate was too high, the growth of the strain was also inhibited. When the industrial ammonium sulfate content reached 2.5%, the rubber production rate of Xanthomonas campestris reached its lowest level, at 2.346%. Therefore, the optimal addition amount of industrial ammonium sulfate determined by the present method is 1.5%.

[0204] As shown in Figure 4 of Example 4, Figure 5 of Example 5, and Figure 6 of Example 6, in Example 4, the fermentation conditions and inoculum size were optimized. As the inoculum size of the (Xanthomonas campestris) bacterial liquid continued to increase, the xanthan gum production rate of the strain showed a trend of first increasing and then decreasing. The yield peaked at 4.171% at an inoculum size of 15%. A smaller inoculum size slowed fermentation, prolonged fermentation time, and reduced the yield of xanthan gum synthesized within the specified fermentation time. While an excessive inoculum size can shorten the growth cycle, it can cause the substrate in the liquid fermentation medium to be utilized prematurely, resulting in apoptosis of the strain due to malnutrition in the later stages, reducing xanthan gum synthesis. Therefore, the optimal inoculum size determined by the present application method is 15%.

[0205] In Example 5, the fermentation conditions and fermentation time were optimized. When the fermentation time was less than 120 hours, the xanthan gum yield of (Xanthomonas campestris) gradually increased with the fermentation time, reaching a peak of 4.203% at 120 hours. When the fermentation time was greater than 144 hours, the xanthan gum yield showed a downward trend. Therefore, the optimal fermentation time determined by the present method is 120 hours.

[0206] In Example 6, the fermentation temperature was optimized. As the temperature gradually increased, the gum yield of Xanthomonas campestris also gradually increased, reaching a peak of 4.342% at 40°C. As the fermentation temperature continued to increase, the gum yield showed a downward trend. This may be due to the fermentation temperature being too high. The high temperature inside the liquid fermentation medium affected the normal growth and metabolism of Xanthomonas campestris, thereby reducing xanthan gum production. Therefore, the optimal fermentation temperature determined by the present method is 40°C.

[0207] Example 6 produces xanthan gum through low-cost and efficient fermentation. Using the production medium formula and fermentation conditions described in Example 6, the xanthan gum yield can be significantly increased, providing a high-yield xanthan gum production medium that can be used as a scaled-up production medium. The cost of the liquid fermentation medium formula is reduced by using cheaper and more readily available corn starch as a carbon source to replace a portion of the glucose used. Compared to tryptone, cheaper and more readily available industrial ammonium sulfate is used as a nitrogen source, reducing costs. By optimizing the substrate concentration, inoculum size, fermentation time, and fermentation temperature of the low-cost fermentation production medium, the final xanthan gum yield can be significantly increased, providing a high-yield xanthan gum production medium and fermentation conditions that can be used for scaled-up production.

[0208] In the present application, Xanthomonas campestris is grown and enriched using corn starch and a nitrogen source. After the strain grows to the logarithmic phase, corn starch is used as a carbon source and industrial ammonium sulfate is used as a nitrogen source for xanthan gum synthesis. The cost of the culture medium formula is significantly reduced, and the gum yield is still significantly increased, indicating that the strain and the culture medium formula have value as industrial production strains and liquid fermentation medium. Xanthomonas campestris is subcultured, and the xanthan gum yield is measured every two generations, and the xanthan gum yield remains stable, which is much higher than that of other patented strains. By optimizing the content of corn starch and industrial ammonium sulfate in the liquid fermentation medium, Xanthomonas campestris is synthesized. campestris achieved a maximum xanthan gum yield of 4.172% under the optimal fermentation medium containing, by weight, 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% potassium dihydrogen phosphate, and 0.1% potassium dihydrogen phosphate at a pH of 7.0. By optimizing fermentation conditions (inoculation size, fermentation time, and fermentation temperature), the optimal conditions were determined to be an inoculum size of 15%, a shaker speed of 180 rpm, a fermentation time of 120 hours, and a fermentation temperature of 40°C. Under these optimal conditions, the xanthan gum yield of Xanthomonas campestris reached 4.342%. Compared to the original fermentation conditions and medium concentrations, the xanthan gum yield of Xanthomonas campestris increased by 13.37%.

[0209] In summary, the method of the present application uses cheap production raw materials and relatively simple production equipment, which can greatly reduce costs and improve economic benefits; the production cycle of the method of the present application is lower than that of the traditional xanthan gum fermentation method, which reduces the production time cost and improves production efficiency; compared with the traditional production method, the method of the present application is simpler and easier to implement, and only requires a certain amount of fermentation technology operation experience to produce high-yield xanthan gum, providing a more convenient way for the production of small and medium-sized enterprises; the fermentation raw materials used in the method of the present application are all from renewable resources, and not too much wastewater and waste gas are generated during the production process, and it has good environmental protection characteristics, which meets the demand of modern society for environmentally friendly products.

[0210] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A xanthan gum fermentation medium, characterized in that: including liquid seed culture medium and liquid fermentation culture medium; The composition of the liquid seed culture medium includes, by weight percentage: 1% corn starch, 0.5% industrial ammonium sulfate, 0.3% potassium dihydrogen phosphate, and a pH value of 7.0; The liquid fermentation medium is composed of, by weight percentage, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and 4.0%, 5.0%, 6.0%, 7.0% or 8.0% corn starch; Alternatively, the liquid fermentation medium comprises, by weight percentage, 5.0% corn starch, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate and 0.5%, 1.0%, 1.5%, 2.0% or 2.5% industrial ammonium sulfate.

2. A method for culturing liquid seeds of Xanthomonas campestris, characterized in that: Inoculating the Xanthomonas campestris into the liquid seed culture medium in the xanthan gum fermentation culture medium according to claim 1 to activate the strain and perform liquid seed culture to obtain liquid seeds; The method for activating the strains comprises: campestris) was wiped with 75% alcohol cotton in a clean bench to disinfect the surface of the freeze-dried tube, the top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp, 2 drops of sterile distilled water were dripped into the heated part to break the tube wall, the broken part was knocked off with tweezers, 0.5 mL of liquid seed culture medium was sucked into the freeze-dried tube with a pipette to dissolve all the freeze-dried bacterial powder, the dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed, 1 drop of bacterial suspension remaining in the pipette was transferred to the solid culture medium in the slant test tube, the liquid test tube and the slant test tube were placed in an incubator for static culture until the bacterial solution became turbid or colonies grew on the slant surface; then the bacterial solution cultured in the liquid test tube was inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum amount, and cultured in a constant temperature shaker at 30°C and 180 r / min for 72 h, and subcultured twice to restore its activity; The liquid seed culture is as follows: the bacterial liquid obtained after bacterial strain activation is inoculated into a 250mL conical flask containing 100mL of liquid seed culture medium according to a 1% inoculation amount, and cultured in a constant temperature shaking incubator at 30°C and 180r / min for 24h to complete the liquid seed culture.

3. A xanthan gum fermentation method, characterized in that: The strain of Xanthomonas campestris is activated, and then liquid seed culture is performed, and then the liquid seeds are inoculated into a liquid fermentation medium to prepare xanthan gum; The method for activating the strains comprises: campestris) was wiped with 75% alcohol cotton in a clean bench to disinfect the surface of the freeze-dried tube, the top of the freeze-dried tube was evenly heated at the outer flame of an alcohol lamp, 2 drops of sterile distilled water were dripped into the heated part to break the tube wall, the broken part was knocked off with tweezers, 0.5 mL of liquid seed culture medium was sucked into the freeze-dried tube with a pipette to dissolve all the freeze-dried bacterial powder, the dissolved bacterial suspension was transferred to a liquid test tube containing 4 mL of liquid seed culture medium and mixed, 1 drop of bacterial suspension remaining in the pipette was transferred to the solid culture medium in the slant test tube, the liquid test tube and the slant test tube were placed in an incubator for static culture until the bacterial solution became turbid or colonies grew on the slant surface; then the bacterial solution cultured in the liquid test tube was inoculated into a 250 mL conical flask containing 100 mL of liquid seed culture medium at a 1% inoculum amount, and cultured in a constant temperature shaker at 30°C and 180 r / min for 72 h, and subcultured twice to restore its activity; The liquid seed culture medium comprises, by weight percentage, 1% corn starch, 0.5% industrial ammonium sulfate, 0.3% potassium dihydrogen phosphate, and a pH value of 7.0; The liquid seed culture is as follows: the bacterial liquid obtained after bacterial strain activation is inoculated into a 250mL conical flask containing 100mL of liquid seed culture medium according to a 1% inoculation amount, and cultured in a constant temperature shaking incubator at 30°C and 180r / min for 24h to complete the liquid seed culture.

4. The fermentation method of xanthan gum according to claim 3, characterized in that: The method of inoculating liquid seeds into liquid fermentation medium to prepare xanthan gum comprises: inoculating the liquid seeds into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculation amount of 5%, and culturing in a shaking table at 30°C and 180r / min for 72h at a constant temperature; after the fermentation is completed, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation liquid to dilute the fermentation liquid, and then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000r / min for 15min, discarding the supernatant, retaining the precipitate, and then washing the precipitate twice with anhydrous ethanol, drying in a 60°C oven, grinding and weighing, to obtain the fermentation product xanthan gum.

5. The fermentation method of xanthan gum according to claim 4, characterized in that: The composition of the liquid fermentation medium includes, by weight percentage, 4.0% corn starch, 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate and 0.1% potassium dihydrogen phosphate, and the pH value of the liquid fermentation medium is 7.

0.

6. The fermentation method of xanthan gum according to claim 4, characterized in that: The composition of the liquid fermentation medium includes, by weight percentage: 1.0% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and 5.0%, 6.0%, 7.0% or 8.0% corn starch; and the pH value of the liquid fermentation medium is 7.

0.

7. The fermentation method of xanthan gum according to claim 4, characterized in that: The composition of the liquid fermentation medium includes, by weight percentage, 5.0% corn starch, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and 0.5%, 1.0%, 1.5%, 2.0% or 2.5% industrial ammonium sulfate; and the pH value of the liquid fermentation medium is 7.

0.

8. The fermentation method of xanthan gum according to claim 3, characterized in that: The composition of the liquid fermentation medium includes, by weight percentage: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, and 0.1% potassium dihydrogen phosphate, and the pH value of the liquid fermentation medium is 7.0; The method of inoculating liquid seeds into liquid fermentation medium to prepare xanthan gum comprises: inoculating the liquid seeds into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculation amount of 5%, 10%, 15%, 20%, or 25%, and culturing at 30°C and 180r / min in a shaking table for 72h at a constant temperature; after the fermentation is completed, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation liquid to dilute the fermentation liquid, then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000r / min for 15min, discarding the supernatant, retaining the precipitate, washing the precipitate twice with anhydrous ethanol, drying in a 60°C oven, grinding and weighing, and obtaining the fermentation product xanthan gum.

9. The fermentation method of xanthan gum according to claim 3, characterized in that: The composition of the liquid fermentation medium includes, by weight percentage: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and a pH value of 7.0; The method of inoculating liquid seeds into liquid fermentation medium to prepare xanthan gum comprises: inoculating the liquid seeds into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculation amount of 15%, and culturing in a shaking table at 30°C and 180r / min for 48h, or 72h, or 96h, or 120h, or 144h at a constant temperature; after the fermentation is completed, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation liquid to dilute the fermentation liquid, and then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000r / min for 15min, discarding the supernatant, retaining the precipitate, and then washing the precipitate twice with anhydrous ethanol, drying in a 60°C oven, grinding and weighing, to obtain the fermentation product xanthan gum.

10. The xanthan gum fermentation method according to claim 3, characterized in that: The composition of the liquid fermentation medium includes, by weight percentage: 5.0% corn starch, 1.5% industrial ammonium sulfate, 0.3% magnesium sulfate heptahydrate, 0.1% dipotassium hydrogen phosphate, 0.1% potassium dihydrogen phosphate, and a pH value of 7.0; The method of inoculating liquid seeds into liquid fermentation medium to prepare xanthan gum comprises: inoculating the liquid seeds into a 250mL conical flask containing 100mL of liquid fermentation medium at an inoculation rate of 15%, and culturing at a constant temperature of 180r / min on a shaking table for 120h at a temperature of 25°C, 35°C, 40°C, or 50°C; after the fermentation is completed, using an ethanol precipitation method, adding 3 times the volume of deionized water to the fermentation liquid to dilute the fermentation liquid, and then adding 3 times the volume of anhydrous ethanol to precipitate the xanthan gum, centrifuging at 8000r / min for 15min, discarding the supernatant, retaining the precipitate, and then washing the precipitate twice with anhydrous ethanol, drying in a 60°C oven, grinding and weighing, to obtain the fermentation product xanthan gum.

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