Method for preparing bacterial cellulose by using supernatant after extracting protein from distiller's grains and application thereof

Abstract

The application discloses a method for preparing bacterial cellulose by using supernatant after protein extraction from distiller's grains and application thereof. The method comprises the following steps: S1, performing protein extraction treatment on a distiller's grains hydrolysate to obtain supernatant after protein extraction from the distiller's grains, then mixing the supernatant with a Henley-Schramm culture medium, adjusting the pH value to 5.5-6.8 to obtain a compound culture medium; S2, inoculating a Komagataeibacter xylinus seed liquid into the compound culture medium, performing shallow static culture, collecting a surface bacterial cellulose membrane, and performing purification to obtain the bacterial cellulose. It is found by experiments that, under the same compound ratio, the yield of the bacterial cellulose prepared by using the supernatant after protein extraction from the distiller's grains is higher than that of the bacterial cellulose prepared by directly using the distiller's grains hydrolysate without protein extraction, and the crystallinity of the obtained bacterial cellulose product is also higher. The preparation process is simple, and can provide an effective way for low-cost industrial production of the bacterial cellulose and efficient utilization of distiller's grains waste.

Description

Technical Field

[0001] This invention relates to the field of microbial fermentation technology, and in particular to a method and application for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains. Background Technology

[0002] Bacterial cellulose (BC) is an extracellular polysaccharide material synthesized by specific microorganisms (such as *Xylostella spp.*) during liquid culture. Compared with plant cellulose, bacterial cellulose has advantages such as high purity, high crystallinity, well-developed nanofiber network structure, good water retention, and excellent mechanical properties, thus showing promising applications in food, medical dressings, adsorption separation, sensors, and membrane materials. Currently, one of the main factors limiting the further application of bacterial cellulose is its high culture cost, especially since conventional culture systems typically rely on refined carbon sources such as glucose and sucrose, as well as nutrients such as yeast extract and peptone, resulting in high unit product costs. Therefore, developing low-cost, renewable substrates to replace traditional culture medium raw materials has become an important research direction in this field.

[0003] In recent years, brewing waste (such as baijiu lees, rice wine lees and their leachates and hydrolysates) has been studied as a potential substrate for bacterial cellulose fermentation due to its relatively rich content of organic matter, crude protein, cellulose degradation products and inorganic salts. Related technologies have disclosed methods for preparing bacterial cellulose using lees leachates or hydrolysates, such as increasing yield by optimizing culture medium formulations, adding additional carbon and nitrogen sources, or employing deep and shallow layer coupled fermentation. However, some shortcomings remain: Firstly, most studies still rely heavily on the addition of refined components such as glucose, peptone, and yeast extract to maintain high yields, failing to effectively address the complex composition of the distillers' grains system and the coexistence of inhibitory substances from the perspective of substrate composition regulation. Secondly, there is insufficient understanding of the inhibitory effects of potentially unfavorable components in the distillers' grains (especially proteins and their associated components) on bacterial cellulose formation, and a lack of acid-base regulation and compound utilization schemes for the special substrate "supernatant after protein extraction". In addition, although related studies mention that shallow static culture is beneficial to improving oxygen supply efficiency, there is a lack of systematic research on the balance between culture volume, liquid layer thickness, gas-liquid interface area and evaporation rate, resulting in poor film-forming stability and large yield fluctuations.

[0004] Therefore, there is an urgent need to develop a preparation method that can fully utilize the supernatant after protein extraction from distiller's grains, while overcoming acid inhibition, improving film-forming stability and bacterial cellulose yield, so as to achieve high-value utilization of brewing waste and low-cost, stable production of bacterial cellulose. Summary of the Invention

[0005] The first objective of this invention is to provide a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains.

[0006] A second aspect of the present invention is to provide a bacterial cellulose obtained by the above method.

[0007] A third aspect of the present invention aims to provide the use of bacterial cellulose obtained by the method described above in the preparation of medical materials and / or food packaging films.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, comprising the following steps: S1. Protein extraction is performed on the hydrolysate of distiller's grains to obtain the supernatant after protein extraction. Then, it is mixed with Heinz-Schram (HS) medium and the pH is adjusted to 5.5-6.8 to obtain the compound medium. S2. Inoculate the Xylose-containing Bacillus seed culture into the compound culture medium, and after shallow static culture, collect the surface bacterial cellulose membrane, and purify it to obtain the final product.

[0009] The method according to embodiments of the present invention has at least the following beneficial effects: This invention discovers that by treating the hydrolysate of distiller's grains with protein extraction, unfavorable components that inhibit bacterial cellulose synthesis (such as proteins and their associated organisms) can be effectively removed from the original system, significantly improving the conversion efficiency (yield) of the chemical oxygen demand per unit of culture medium. Furthermore, experiments show that, under the same compounding ratio, the bacterial cellulose yield of the supernatant after protein extraction reaches 10.8%, while the yield of the hydrolysate of distiller's grains without protein extraction is only 7.2%. Simultaneously, the protein extraction treatment from distiller's grains also helps to improve the crystallinity of the product (from 79.0% to 87.8%).

[0010] Furthermore, this invention has found that adjusting the pH of the supernatant after protein extraction (preferably 6.0) and mixing it with Heinz-Schram medium in a specific ratio (preferably 1:1) helps overcome the acidity inhibition of the original supernatant (yield is only 3.1% without pH adjustment), while avoiding the high cost of relying entirely on purified medium, and enabling synergistic optimization of waste resources and nutrient substrates.

[0011] In some embodiments of the present invention, the volume ratio of the supernatant after protein extraction from distillers' grains to Heinz-Schram medium is 1:3 to 2:1.

[0012] In some embodiments of the present invention, the preparation method of the distillers' grains hydrolysate includes: adding distillers' grains powder to a sodium hydroxide solution, hydrolyzing at 100~130°C, centrifuging to obtain the supernatant.

[0013] In some embodiments of the present invention, the lees powder is baijiu (Chinese white liquor) lees powder.

[0014] In some embodiments of the present invention, the particle size of the distiller's grains powder is less than 0.5 mm.

[0015] In some embodiments of the present invention, the concentration of the sodium hydroxide solution is 0.05~0.2 mol / L.

[0016] In some embodiments of the present invention, the mass-to-volume ratio of the distiller's grains powder to the sodium hydroxide solution is 5-20 g: 250 mL. Preferably, it is 10-15 g: 250 mL.

[0017] In some embodiments of the present invention, the hydrolysis time is 2 to 4 hours.

[0018] The preparation method of this invention uses distiller's grains (such as brewing waste) as the main raw material, which significantly reduces the production cost of bacterial cellulose, while realizing the high-value resource utilization of distiller's grains. Moreover, the preparation process is simple, easy to scale up and promote, and provides an effective means for low-cost industrial production of bacterial cellulose and green disposal of distiller's grains waste.

[0019] In some embodiments of the present invention, the protein extraction process includes: adding hydrochloric acid to the distillers' grains hydrolysate until the protein flocculates and precipitates, and centrifuging to obtain the supernatant, which is the final product.

[0020] In some embodiments of the present invention, the concentration of the hydrochloric acid is 0.05~0.2 mol / L.

[0021] In some embodiments of the present invention, the pH value of the supernatant after protein extraction from distiller's grains is 3 to 4.

[0022] In some embodiments of the present invention, the COD of the supernatant after protein extraction from distiller's grains is 8-12 g / L, preferably 10-11 g / L.

[0023] Compared with unextracted distiller's grains hydrolysate, the supernatant after protein extraction showed a decrease in the content of water-soluble protein and total phosphorus. However, after subsequent pH adjustment and culture medium recombination, it was more conducive to bacterial cellulose synthesis.

[0024] In some embodiments of the present invention, the Heinz-Schram medium comprises: 20-30 g / L glucose, 4-6 g / L yeast extract, 4-6 g / L peptone, 5-8 g / L disodium hydrogen phosphate dodecahydrate, and 4-8 g / L citric acid monohydrate.

[0025] In some embodiments of the present invention, in step S1, the pH value of the compound culture medium is preferably 5.8 to 6.5.

[0026] This invention reveals that when the pH is not adjusted, the supernatant after protein extraction is acidic, with a system pH of approximately 3-4, which significantly inhibits bacterial cellulose production. However, adjusting the pH to around 6 can significantly improve the bacterial cellulose yield and productivity of the system.

[0027] In some embodiments of the present invention, the xylocoryloylcabrella is xylocoryloylcabrella CICC10529.

[0028] In some embodiments of the present invention, the OD600 value of the *Xylostella spp.* seed culture is 0.6 to 1.0.

[0029] In some embodiments of the present invention, the inoculation amount of the *Xylostella xylostella* seed solution is 8-15% (v / v).

[0030] In some embodiments of the present invention, the thickness of the culture medium liquid layer in the shallow static culture is 1.7 to 3.2 mm.

[0031] Preferably, the shallow static culture is carried out using a culture dish with a diameter of 90 mm, and 15-20 mL of culture medium is added to each dish.

[0032] When the culture medium volume is fixed at 20 mL, the bacterial cellulose yield and productivity are highest at a petri dish diameter of approximately 120 mm. If the surface area continues to increase, evaporation becomes too rapid, leading to poor reproducibility. In a 90 mm diameter petri dish, when the culture medium volume increases to 30 mL, the liquid layer becomes too thick, restricting oxygen transfer, causing the film to become brittle, and reducing the yield. Using shallow static culture, by synergistically adjusting the liquid layer thickness, culture medium volume, and gas-liquid interface area, helps improve the efficiency of bacterial cellulose production and film stability.

[0033] In some embodiments of the present invention, disposable sterile culture dishes with a diameter of 90 mm are used, each containing 20 mL of a compound culture medium, with the pH adjusted to 6, and an inoculation volume of 12% (v / v). After sealing with sealing film, the dishes are incubated statically at 30°C for 7 days. This method is simple to implement, has good reproducibility, and is convenient for implementation and scale-up verification under laboratory conditions.

[0034] In some embodiments of the present invention, the temperature of the shallow static culture is 28~32°C.

[0035] In some embodiments of the present invention, the shallow static culture time is 5 to 10 days.

[0036] In some embodiments of the present invention, the purification includes: sequentially washing, decellularizing and drying the surface bacterial cellulose membrane.

[0037] In some embodiments of the present invention, the decellularization treatment includes: placing the washed bacterial cellulose membrane in a 0.1~0.3 mol / L sodium hydroxide solution and treating it in a water bath at 70~90°C for 2~4 hours.

[0038] In some embodiments of the present invention, the drying temperature is 70~90°C.

[0039] In some embodiments of the present invention, the drying time is 16 to 48 hours.

[0040] First, filter or directly collect the bacterial cellulose membrane from the fermentation surface and rinse it repeatedly with deionized water to remove residual culture medium. Then, place the bacterial cellulose membrane in a 0.2 mol / L sodium hydroxide solution and incubate it in a water bath at 80°C for 3 hours to remove bacterial cells and culture medium residues. Rinse it repeatedly with deionized water until the pH of the washing solution is close to 7. Finally, dry the purified bacterial cellulose membrane at 80°C for 24 hours, which helps to obtain a bacterial cellulose product with higher crystallinity.

[0041] A second aspect of the present invention provides bacterial cellulose prepared using the method described in the first aspect.

[0042] In some embodiments of the present invention, the crystallinity of the bacterial cellulose is not less than 80%. Preferably, the crystallinity of the bacterial cellulose is not less than 85%.

[0043] A third aspect of the invention provides the use of bacterial cellulose obtained by the method described in the first aspect in the preparation of medical materials and / or food packaging films.

[0044] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a flowchart of the bacterial cellulose preparation process of the present invention; Figure 2 This is a comparison chart of bacterial cellulose yield and productivity obtained by adding different proportions of HS culture medium and supernatant after protein extraction from distiller's grains according to the present invention. Figure 3 The XRD patterns are of bacterial cellulose produced in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0046] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0047] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0048] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0049] In the description of this invention, the reference term "and / or" includes all and any combination of one or more of the associated listed items. For example, A and / or B includes (A and B) and (A or B).

[0050] In a specific embodiment of the present invention, the lees powder is made from the lees waste of Moutai Group. First, it is dried. The dried lees are then crushed and sieved through a 0.5 mm sieve to obtain lees powder with relatively uniform particle size. The sieved lees powder is then sealed and stored for subsequent hydrolysis pretreatment. Alternatively, commercially available conventional baijiu lees powder can also achieve comparable results.

[0051] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0052] Example 1 This embodiment provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, and its technical roadmap is shown below. Figure 1 As shown, it specifically includes the following content.

[0053] (1) Preparation of distiller's grains hydrolysate Weigh 12.5 g of distiller's grains powder and add it to 250 mL of 0.1 mol / L sodium hydroxide solution. Hydrolyze the solution in hot water at 120℃ for 3 h. After the reaction is complete, cool the solution to room temperature, dispense the solution into centrifuge tubes, centrifuge at 4000 rpm for 10 min, collect the supernatant to obtain the distiller's grains hydrolysate for later use.

[0054] (2) Preparation of supernatant after protein extraction from distiller's grains Take 100 mL of the hydrolysate obtained in the above steps and place it in an Erlenmeyer flask. Slowly add 50 mL of 0.1 mol / L hydrochloric acid solution while stirring until the system becomes noticeably turbid. Then allow it to stand for 15 min to allow the proteins in the system to fully flocculate and precipitate, forming a flocculent precipitate. After standing, transfer the entire system to a centrifuge tube and centrifuge at 4000 rpm for 10 min to separate the supernatant and precipitate. The precipitate after centrifugation is the distillers' grains protein, which can be further utilized for high-value extraction; the supernatant after centrifugation is the supernatant after protein extraction from the distillers' grains, with a pH of approximately 3.85 and a COD of approximately 10.88 g / L.

[0055] (3) Large-scale culture of microbial strains After reviving and activating *Xylostella spp.* CICC 10529, a single colony was picked and inoculated into 5 mL of HS liquid medium. The culture was then shaken at 30℃ and 200 rpm for 36 h to obtain the primary seed culture. The culture was then transferred at a 5% (v / v) inoculation rate to a 200 mL Erlenmeyer flask containing 100 mL of HS liquid medium and shaken at 30℃ and 200 rpm until the bacterial OD600≈0.885 was obtained to obtain the secondary seed culture for later use.

[0056] The HS liquid culture medium comprises: 30 g / L glucose, 5 g / L yeast extract, 5 g / L peptone, 6.8 g / L disodium hydrogen phosphate dodecahydrate, and 5 g / L citric acid monohydrate, with the pH adjusted to 6, and sterilized at 115°C for 30 min. Preferably, 1.8% (w / v) agar powder is added to the solid HS culture medium.

[0057] (4) Shallow static culture The HS culture medium was mixed with the supernatant from the above-mentioned protein extraction from distiller's grains at a volume ratio of 1:1, and the initial pH of the system was adjusted to 6.0 to obtain the compound culture medium.

[0058] Then, the above secondary seed culture was added to the compound culture medium at an inoculation rate of 12% (v / v), gently shaken, and dispensed into disposable sterile culture dishes with a diameter of 9 cm. 20 mL of culture medium was added to each dish (i.e., the culture thickness was about 2 mm). The dishes were sealed with PARAFILM sealing film and incubated at 30°C for 7 days.

[0059] (5) Purification of bacterial cellulose After cultivation, the bacterial cellulose membrane formed on the surface was collected, rinsed repeatedly with deionized water, placed in 0.2 mol / L sodium hydroxide solution, and subjected to decellularization treatment by water bath at 80℃ for 3 h. It was then washed with deionized water until neutral, and finally dried at 80℃ for 24 h to obtain bacterial cellulose.

[0060] Example 2 This embodiment provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), the volume ratio of HS culture medium to the supernatant after protein extraction from distillers' grains is 3:1, and the rest of the methods are the same.

[0061] Example 3 This embodiment provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), the volume ratio of HS culture medium to the supernatant after protein extraction from distillers' grains is 2:1, and the rest of the methods are the same.

[0062] Example 4 This embodiment provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), the volume ratio of HS culture medium to the supernatant after protein extraction from distillers' grains is 1:2, and the rest of the methods are the same.

[0063] Comparative Example 1 This comparative example provides a method for preparing bacterial cellulose using distillers' grains hydrolysate, which differs from Example 1 in that: In step (4), the supernatant after protein extraction from the lees is replaced with lees hydrolysate, and the rest of the method is the same.

[0064] Comparative Example 2 This comparative example provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), the volume ratio of HS culture medium to the supernatant after protein extraction from distillers' grains is 1:3, and the rest of the methods are the same.

[0065] Comparative Example 3 This comparative example provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), only the hydrolysate after protein extraction from distillers' grains is used as the culture substrate, and the rest of the methods are the same.

[0066] Comparative Example 4 This comparative example provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), the supernatant after protein extraction from distiller's grains is not subjected to pH adjustment (initial pH is 3.85). After being mixed with HS medium, the resulting compound medium has a pH of 4.1. The rest of the process is the same.

[0067] Comparative Example 5 This comparative example provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, which differs from Example 1 in that: In step (4), the supernatant after protein extraction from the above-mentioned lees is mixed with HS culture medium at a volume ratio of 1:1, and the initial pH of the system is adjusted to 7.0. The rest of the methods are the same.

[0068] Example 1: Determination of bacterial cellulose yield and productivity This test example examines the yield and productivity of bacterial cellulose prepared by the methods described in Examples 1-4 and Comparative Examples 1-5. Bacterial cellulose yield (%) = COD of bacterial cellulose / COD of the culture medium; Bacterial cellulose yield (g / L) = bacterial cellulose dry weight (g) ÷ fermentation broth volume (L) Calculate bacterial cellulose yield and production; Bacterial cellulose dry weight (g): The bacterial cellulose gel film was dried in a vacuum oven at 80°C for 24 h, and then weighed using an electronic balance to obtain the bacterial cellulose dry weight (g). COD was determined using the potassium dichromate method.

[0069] The test results are shown in Table 1. A comparison of bacterial cellulose yield and productivity obtained from different addition ratios of HS culture medium and the supernatant after protein extraction from distiller's grains is shown in the figure below. Figure 2 As shown.

[0070] Table 1:

[0071] The above results show that the method of the present invention can obtain a high bacterial cellulose yield and efficiency. Compared with Example 1, when using unextracted distillers' grains hydrolysate as a substrate for culture preparation (such as Comparative Example 1), although the yield can reach 2.0 g / L, the efficiency is only 7.2%, which is significantly lower than that of Example 1 (10.8%) under the same proportion. This indicates that removing associated components such as protein is beneficial to improving substrate utilization efficiency.

[0072] Furthermore, when the supernatant from protein extraction from distiller's grains was mixed with HS culture medium at different volume ratios, the yield and productivity of bacterial cellulose showed a trend of first increasing and then decreasing. Among them, the best overall performance was achieved at a volume ratio of 1:1 (Example 1), with a yield of 2.5 g / L and a productivity of 10.8%.

[0073] Example 2: Detection of bacterial cellulose crystallinity This test example examines the crystallinity of the bacterial cellulose prepared in Example 1 and Comparative Example 1, using the following specific method: XRD analysis was performed on the dried bacterial cellulose using an X-ray diffractometer. The radiation source was Cu-Kα radiation (λ = 1.5418 Å), the tube voltage was 40 kV, the tube current was 40 mA, the scanning range was 2θ = 10°~60°, and the step size was 0.02°. The crystallinity was calculated based on the scanning results and the crystallinity calculation formula.

[0074] The formula used to calculate crystallinity is as follows: ; in: I 200 (200) Maximum intensity of the diffraction peak of the crystal plane; I am The strength of the nearest valley value.

[0075] Figure 3 The XRD patterns of two bacterial celluloses are shown, where HS:SJYB=1:1 is the XRD pattern of bacterial cellulose prepared by the method of Example 1, and HS:SJYA=1:1 is the XRD pattern of bacterial cellulose prepared by the method of Comparative Example 1. The crystallinity of the bacterial cellulose prepared by the method of Example 1 was calculated. CrI (%) = (820-100) / 820×100% = 87.8%, the crystallinity of bacterial cellulose obtained by the method of Comparative Example 1. CrI (%) = (195-41) / 195×100% = 79.0%, indicating that after removing the associated components such as protein from the distillers' grains hydrolysate through protein extraction treatment, it is more conducive to the synthesis of bacterial cellulose with higher crystallinity by *Bacillus xylose*.

[0076] In summary, this invention provides a method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains. The method includes first subjecting the distiller's grains to alkali dissolution and acid precipitation to remove associated inhibitory components such as proteins, obtaining a supernatant after protein extraction; then, compounding this supernatant with Heinz-Schlamyd medium at a specific volume ratio, adjusting the initial pH to approximately 6, and inoculating with *Xylostella xylostella*, followed by fermentation under shallow static conditions. Finally, the bacterial cellulose product is obtained through alkali washing, water washing, and drying. This invention effectively eliminates the inhibitory effect of unfavorable components such as proteins in the original distiller's grains hydrolysate on bacterial cellulose synthesis through protein extraction, significantly improving the chemical oxygen demand utilization rate (yield) of the culture medium (e.g., the yield in Example 1 reached 10.8%, far exceeding the 7.2% without protein extraction). Simultaneously, this invention finds that compounding and pH adjustment can effectively overcome acid inhibition problems, and combined with shallow static conditions to synergistically control the liquid layer thickness and gas-liquid interface area, helps to further improve film-forming stability and product crystallinity (crystallinity increased from 79.0% to 87.8%). Furthermore, the method of the present invention uses brewing waste as raw material, which significantly reduces the production cost of bacterial cellulose, realizes the high-value resource utilization of distiller's grains, and has a simple preparation process that is suitable for industrial production and has a good application prospect.

[0077] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing bacterial cellulose from the supernatant after protein extraction from distiller's grains, characterized in that, Includes the following steps: S1. Protein extraction is performed on the hydrolysate of distiller's grains to obtain the supernatant after protein extraction. Then, it is mixed with Heinz-Schram medium and the pH is adjusted to 5.5-6.8 to obtain the compound medium. S2. Inoculate the Xylose-containing Bacillus seed culture into the compound culture medium, and after shallow static culture, collect the surface bacterial cellulose membrane, and purify it to obtain the final product.

2. The method according to claim 1, characterized in that, The volume ratio of the supernatant after protein extraction from distillers' grains to Heinz-Schram medium is 1:3 to 2:

1.

3. The method according to claim 1, characterized in that, The preparation method of the distillers' grains hydrolysate includes: adding distillers' grains powder to sodium hydroxide solution, hydrolyzing at 100~130℃, centrifuging to obtain the supernatant; Preferably, the concentration of the sodium hydroxide solution is 0.05~0.2 mol / L; Preferably, the mass-to-volume ratio of the distiller's grains powder to the sodium hydroxide solution is 5-20 g: 250 mL; Preferably, the hydrolysis time is 2-4 hours.

4. The method according to claim 1, characterized in that, The protein extraction process includes: adding hydrochloric acid to the distillers' grains hydrolysate until the protein flocculates and precipitates, centrifuging to obtain the supernatant, which is the final product; Preferably, the concentration of the hydrochloric acid is 0.05~0.2 mol / L.

5. The method according to claim 1, characterized in that, The Heinz-Schram medium contains: 20-30 g / L glucose, 4-6 g / L yeast extract, 4-6 g / L peptone, 5-8 g / L disodium hydrogen phosphate dodecahydrate, and 4-8 g / L citric acid monohydrate.

6. The method according to any one of claims 1 to 5, characterized in that, The xylose-like bacterium is xylose-like bacterium CICC 10529; Preferably, the OD600 value of the *Xylostella tumefaciens* seed culture is 0.6~1.0; Preferably, the inoculation amount of the *Xylostella spp.* seed culture is 8-15% (v / v).

7. The method according to claim 6, characterized in that, The thickness of the culture medium liquid layer in the shallow static culture is 1.7–3.2 mm; And / or, the temperature of the shallow static culture is 28~32℃; And / or, the shallow static culture time is 5 to 10 days.

8. The method according to claim 7, characterized in that, The purification process includes sequentially washing, decellularizing, and drying the surface bacterial cellulose membrane. Preferably, the decellularization treatment includes: placing the washed bacterial cellulose membrane in a 0.1~0.3mol / L sodium hydroxide solution and treating it in a water bath at 70~90℃ for 2~4h.

9. A bacterial cellulose prepared by the method according to any one of claims 1 to 8.

10. The use of bacterial cellulose obtained by the method according to any one of claims 1 to 8 in the preparation of medical materials and / or food packaging films.

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