A method for preparing a modified bacterial cellulose

Abstract

The application relates to the technical field of bacterial cellulose and provides a preparation method of modified bacterial cellulose, which solves the problems that the modification method of bacterial cellulose in the prior art is single, the modification treatment steps cannot be considered in advance and in the rear, the product is difficult to consider various forms, and the multifunctional customization requirements such as antibacterial, antiviral, hydrophobic, whitening and antioxidation cannot be met; the method comprises the following steps: S1, preparing bacterial cellulose; S2, modifying the bacterial cellulose, wherein the modification treatment is physical modification or chemical modification; S3, obtaining modified bacterial cellulose; in step S1, the bacterial cellulose is prepared by static fermentation or dynamic fermentation.

Description

Technical Field

[0001] This invention relates to the field of bacterial cellulose technology, and more particularly to a method for preparing modified bacterial cellulose. Background Technology

[0002] Bacterial cellulose (BC) is a natural polymer nanomaterial synthesized by microorganisms (such as Acetobacter xylinum). It has excellent properties such as ultra-fine three-dimensional network structure, high crystallinity, high water retention, good biocompatibility and biodegradability, and shows great application potential in biomedical materials (such as wound dressings and artificial blood vessels), food packaging, papermaking industry and functional textiles.

[0003] Chinese Patent Publication No. CN108951144A discloses a method for preparing a bacterial cellulose-modified breathable wool fabric, comprising the following steps: S1. Preparing a bacterial cellulose gel membrane; S2. Preparing bacterial cellulose powder; S3. Dissolving the bacterial cellulose obtained in step S2 in acetone solution to prepare a bacterial cellulose solution; S4. Preparing a maleic anhydride-modified bacterial cellulose solution; S5. Gradually adding methyl methacrylate to deionized water to obtain a monomer emulsion, placing the wool fabric into the monomer emulsion, then adding the maleic anhydride-modified bacterial cellulose, stirring thoroughly, adding an initiator, and reacting to obtain the bacterial cellulose-modified breathable wool fabric. The modified wool fabric prepared by this invention, through grafting bacterial cellulose, has nearly twice the moisture permeability and nearly twice the quick-drying effect of the ungrafted fabric, thus improving the moisture absorption and quick-drying performance of wool products. However, this method requires the cumbersome step of completely drying the bacterial cellulose into hard sheets before dissolving or dispersing it, which reduces energy consumption and extends the production cycle.

[0004] Chinese Patent Publication No. CN120401061A discloses an antiviral home textile fabric based on bio-based fibers and its preparation method. The spun fibers of the home textile fabric are prepared by blending lactic acid fibers and functionalized fibers. The functionalized fibers include modified lignin fibers and nano-bacterial cellulose. The raw materials for the modified lignin fibers include alkali lignin and polyethylene glycol. The nano-bacterial cellulose is obtained by culturing bacterial fiber membranes in Acetobacter xylinum culture medium, followed by fragmentation and nano-sizing. The nano-bacterial cellulose undergoes antiviral functionalization treatment, including the construction of an organometallic framework structure. This invention can maintain and improve the antiviral effect of the antiviral home textile fabric while increasing its durability. However, this nano-bacterial cellulose modification method is singular and cannot meet the needs of multifunctional customization. Summary of the Invention

[0005] Therefore, in view of the above problems, the present invention provides a method for preparing modified bacterial cellulose, which solves the problems of the existing bacterial cellulose modification methods being singular, the modification treatment steps being unable to take into account both pre- and post-processing, the products being difficult to take into account multiple forms, and the inability to meet the multifunctional customized needs such as antibacterial, antiviral, hydrophobic, whitening, and antioxidant properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing modified bacterial cellulose includes the following steps: S1. Preparation of bacterial cellulose; S2. Modify the bacterial cellulose by means of physical modification or chemical modification. S3. Obtain modified bacterial cellulose; In step S1, the bacterial cellulose is prepared by static fermentation or dynamic fermentation. The static fermentation process involves inoculating bacteria into a culture medium and allowing them to be statically cultured, so that the bacteria form a bacterial cellulose film at the gas-liquid interface, and then removing the bacterial cellulose film from the surface of the culture medium. The dynamic fermentation process involves inoculating bacteria into a culture medium for dynamic fermentation, allowing the bacteria to synthesize bacterial cellulose within the liquid to form a bacterial cellulose slurry, which is then collected by centrifugation and / or filtration.

[0007] In step S1, the process of preparing bacterial cellulose includes: (1) Selection and culture of strains Select bacterial strains for culture and pre-culture the strains in liquid culture medium to obtain sufficient active bacteria; (2) Preparation of culture medium Prepare HS medium (Hestrin-Schramm medium), whose components include glucose, yeast extract, peptone, sodium citrate, and potassium dihydrogen phosphate. The composition of the medium can be adjusted as needed to optimize the yield and quality of bacterial cellulose. (3) Fermentation culture The pre-cultured bacteria are inoculated into the prepared culture medium. Fermentation is then carried out under suitable temperature (usually 15-30℃) and conditions. Static culture: A thin film forms at the gas-liquid interface, which is the membrane material; Dynamic fermentation: Bacteria synthesize cellulose inside the liquid, resulting in a slurry state; Fermentation time is usually 7-14 days, depending on the required cellulose thickness and quality; (4) Collection and purification of cellulose After static fermentation, the bacterial cellulose membrane was removed from the surface of the culture medium. The cellulose membrane was washed several times with distilled water to remove culture medium residue and bacteria. After dynamic fermentation is complete, the bacterial cellulose slurry is collected by centrifugation and filtration. The washed cellulose is treated with alkali to thoroughly remove bacterial cells and other impurities. Finally, the alkali solution is neutralized with plenty of distilled water until the pH is close to neutral.

[0008] Furthermore, the modification treatment is carried out during static fermentation or dynamic fermentation.

[0009] Furthermore, when preparing bacterial cellulose using static fermentation, step S2 involves modifying the bacterial cellulose film removed from the surface of the culture medium.

[0010] Furthermore, when preparing bacterial cellulose using dynamic fermentation, step S2 involves modifying the bacterial cellulose slurry.

[0011] Furthermore, the chemical modification involves grafting the bacterial cellulose with a compound containing a target functional group, wherein the target functional group in the compound is selected from at least one of the following general formulas: general formula (I) containing an antibacterial group, general formula (II) containing an antiviral group, general formula (III) containing a hydrophobic group, general formula (IV) containing a melanin-blocking group, or general formula (V) containing an antioxidant group. The general formula (I) is R1-N + (CH3)2-(CH2) n -X - Where R1 is C 12 -C 18 Alkyl or containing C 12 -C 18 Alkyl chain organic macromolecular groups, n=2-6, X - It is a halide anion; The general formula (II) is R2-(CH2). m -COOH, where R2 is a substituted phenyl group, m=1-3; The general formula (III) is R3-Si(OCH3)3, where R3 is a perfluoroalkyl chain C6F. 13 -C8F 17 ; The general formula (IV) is R4-Ar-Y, where R4 is -OCH3 or -NH-; Ar is phenolic hydroxyphenyl; and Y is -OH, -NH2, -COOH or -CONH2. The general formula (V) is R5-BZ, where R5 is a linking group used to graft the group onto bacterial cellulose, and is -O- or -NH-; B is a cyclic structure derived from catechol, phenolic hydroxyphenyl, thiol phenyl, or ascorbic acid; and Z is -OH, -OCH3, -COOH, or -NH2.

[0012] Furthermore, vitamin B3 derivatives or thiols are added to the bacterial cellulose.

[0013] Furthermore, the physical modification involves forming ionic bonds, hydrogen bonds, or van der Waals forces on the surface of bacterial cellulose through post-treatment.

[0014] Furthermore, after completing the modification treatment in step S2, the following steps are also included: post-processing the modified system to obtain modified bacterial cellulose; The post-processing can be one of the following methods: a. The first system after modifying the bacterial cellulose film obtained from static fermentation is sequentially subjected to molding, washing and drying to obtain membrane-like modified bacterial cellulose. b. The second system after direct modification of bacterial cellulose slurry is washed, dried and ground in sequence to obtain powdered modified bacterial cellulose; c. The second system after direct modification of bacterial cellulose slurry is coated onto the fabric base, and the fabric base is dried to obtain functional bacterial cellulose fabric.

[0015] The coating method is any one of spraying, roller coating, blade coating, dip coating, comma blade coating, curtain coating, and gravure coating.

[0016] Furthermore, the solid content of the second system is 0.5 wt.%-20 wt.

[0017] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows: 1. In static fermentation, surface modification can be performed after film formation, ensuring that the modifier acts only on the film surface or shallow layer, preserving the excellent tensile strength of the bacterial cellulose film. In dynamic fermentation, modification can be performed in the slurry state, where the bacterial cellulose nanofibers are uniformly dispersed, the modifier has a large contact area, and the reaction efficiency is high, making it particularly suitable for powder and fabric impregnation processes. Placing the modification step before or after processing avoids the cumbersome steps of traditional methods that require completely drying the bacterial cellulose into hard sheets before dissolving or dispersing, significantly reducing energy consumption and production cycle time.

[0018] 2. By controlling the fermentation and post-processing methods, this technical solution can prepare three different forms of modified bacterial cellulose: membrane, powder, and fabric composite. The membrane product retains the natural three-dimensional nano-network structure of the bacterial cellulose film, and has high water retention, high air permeability, and biocompatibility, making it suitable for wound dressings or high-end packaging. The powder product, obtained through dynamic fermentation combined with freeze-drying and grinding, yields micro-nano powders that are easy to store and transport, and can be used as a functional additive in cosmetics. The fabric product endows ordinary fabrics with antibacterial, hydrophobic, and antiviral functions. Detailed Implementation Example 1

[0019] A method for preparing modified bacterial cellulose includes the following steps: S1. Preparation of bacterial cellulose; S1-1. Selection and Cultivation of Strains Select *Glucosidobacterium* for culture, and pre-culture the strain in liquid medium to obtain sufficient active bacteria; S1-2, Preparation of Culture Medium Prepare HS medium (Hestrin-Schramm medium), the components of which include glucose, yeast extract, peptone, sodium citrate and potassium dihydrogen phosphate; S1-3, Fermentation Culture The pre-cultured bacteria were inoculated into the prepared culture medium and fermented at 28°C for 10 days. The culture was carried out by static fermentation, which allowed the bacteria to form a bacterial cellulose film at the gas-liquid interface, which is the membrane material. The bacterial cellulose film was then removed from the surface of the culture medium. S1-4. Collection and purification of cellulose After static fermentation, the bacterial cellulose film was removed from the surface of the culture medium and washed repeatedly with distilled water to remove culture medium residues and bacteria. The washed cellulose was then treated with NaOH solution to thoroughly remove bacterial cells and other impurities. Finally, the alkali solution was neutralized with a large amount of distilled water until the pH value was close to neutral to obtain the bacterial cellulose film. S2. The bacterial cellulose is modified by chemical modification. The chemical modification involves grafting the bacterial cellulose with a compound containing a target functional group, wherein the target functional group in the compound is of general formula (I) containing an antibacterial group; and general formula (I) is R1-N. + (CH3)2-(CH2) n -X - Where R1 is the chitosan macromolecular chain, n=2, X - For Br - ; S2-1, Preparation of modified solution N-trimethyl chitosan was dissolved in deionized water to prepare a solution with a concentration of 1.5 wt.%, thus obtaining the modified solution. S2-2, Grafting reaction The purified bacterial cellulose film was immersed in the modified solution and stirred in a 50°C constant temperature water bath for 6 hours. N-trimethyl chitosan was firmly grafted onto the BC surface through electrostatic attraction (adsorption of negatively charged BC by quaternary ammonium salt cations) and hydrogen bonding, thus endowing it with antibacterial properties. S3. Obtain modified bacterial cellulose; The modified system was then subjected to post-processing. The first system, after being modified from the bacterial cellulose film obtained from static fermentation, was sequentially subjected to molding, washing, and drying to obtain a membrane-like modified bacterial cellulose with antibacterial function. Example 2

[0020] The difference from Example 1 is as follows: In steps S1-3, the fermentation culture method is dynamic fermentation. The dynamic fermentation is as follows: bacteria are inoculated into a culture medium for dynamic fermentation, so that the bacteria synthesize bacterial cellulose in the liquid to form a bacterial cellulose slurry, and then the bacterial cellulose slurry is collected by centrifugation and filtration. After completing the modification treatment in step S2, the following steps are also included: post-processing the modified system to obtain modified bacterial cellulose; The post-processing involves washing, drying, and grinding the second system after directly modifying the bacterial cellulose slurry to obtain powdered modified bacterial cellulose.

[0021] The solid content of the second system is 20 wt%.

[0022] Other technical solutions are the same as in Example 1. Example 3

[0023] The difference from Example 2 is as follows: After completing the modification treatment in step S2, the following steps are also included: post-processing the modified system to obtain modified bacterial cellulose; The post-processing involves coating the modified bacterial cellulose slurry onto the fabric base by spraying; and drying the fabric base to obtain the functional bacterial cellulose fabric.

[0024] The solid content of the second system is 10 wt%.

[0025] Other technical solutions are the same as in Embodiment 2. Example 4

[0026] The difference from Example 2 is as follows: S2. The bacterial cellulose is modified by chemical modification. The chemical modification is as follows: the bacterial cellulose is grafted with a compound containing a target functional group, wherein the target functional group in the compound containing the target functional group is a general formula (V) containing an antioxidant group; the general formula (V) is R5-BZ, wherein R5 is a linking group used to graft the group to the bacterial cellulose, which is -O-; B is phenolic hydroxyphenyl; and Z is -COOH; S2-1, Preparation of modified solution Gallic acid was dissolved in deionized water, and the pH was adjusted to 8.0 with NaOH to prepare a 1 wt.% solution. S2-2, Grafting reaction Bacterial cellulose slurry was added to gallic acid solution and stirred at 70°C for 12 h. Gallic acid was grafted onto the bacterial cellulose molecular chain through esterification, introducing antioxidant groups. After completing the modification treatment in step S2, the following steps are also included: post-processing the modified system to obtain modified bacterial cellulose; The post-processing involves washing, drying, and grinding the second system after directly modifying the bacterial cellulose slurry to obtain antioxidant powdered modified bacterial cellulose.

[0027] The solid content of the second system is 5 wt.%.

[0028] Other technical solutions are the same as in Embodiment 2. Example 5

[0029] The difference from Example 2 is as follows: S2. The bacterial cellulose is modified by chemical modification. The chemical modification is performed by grafting the bacterial cellulose with a compound containing a target functional group, wherein the target functional group in the compound containing the target functional group is a general formula (II) containing an antiviral group. The general formula (II) is R 2- (CH2) m- COOH, where R2 is a substituted phenyl group, m=1; S2-1, Preparation of modified solution Take bacterial cellulose slurry and add 1 wt.% sodium dodecylbenzenesulfonate (surfactant, to aid dispersion) and 0.5 wt.% N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC, to activate carboxyl groups). S2-2, Mixed Coating Chlorogenic acid, a modifier, was added to the modification solution, along with dibutyltin dilaurate, a catalyst. The mixture was stirred until homogeneous, and then the system was uniformly coated onto the surface of polyester fabric. The fabric was then dried to obtain functional bacterial cellulose fabric.

[0030] The solid content of the second system is 15 wt.%.

[0031] Other technical solutions are the same as in Embodiment 2. Example 6

[0032] The difference from Example 1 is as follows: S2. The bacterial cellulose is modified by chemical modification. The chemical modification is performed by grafting the bacterial cellulose with a compound containing a target functional group, wherein the target functional group in the compound containing the target functional group is a general formula (IV) containing a melanin-blocking group. The general formula (IV) is R4-Ar-Y, where R4 is -OCH3; Ar is phenolic hydroxyphenyl; and Y is -COOH. S2-1, Preparation of modified solution Ferulic acid was dissolved in a mixed solvent to prepare a solution with a concentration of 1.0 wt.%, and the pH was adjusted to 6.0-7.0 using NaOH solution to obtain a ferulic acid modified solution; the mixed solvent was a mixture of ethanol and water in a 1:1 ratio. S2-2, Grafting reaction The purified bacterial cellulose membrane was immersed in the ferulic acid modified solution prepared in step S1-1, and stirred in a constant temperature water bath at 60℃ for 10h. The ferulic acid reacted with the hydroxyl groups of BC through esterification or etherification via its phenolic or carboxyl groups to form stable chemical bonds. S3. Obtain modified bacterial cellulose; The modified system was then subjected to post-processing. The first system, after being modified from the bacterial cellulose film obtained from static fermentation, was sequentially subjected to molding, washing, and drying to obtain a membrane-like modified bacterial cellulose with the function of blocking melanin deposition.

[0033] Other technical solutions are the same as in Example 1.

[0034] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for preparing modified bacterial cellulose, characterized in that, Includes the following steps: S1. Preparation of bacterial cellulose; S2. Modify the bacterial cellulose by means of physical modification or chemical modification. S3. Obtain modified bacterial cellulose; In step S1, the bacterial cellulose is prepared by static fermentation or dynamic fermentation. The static fermentation process involves inoculating bacteria into a culture medium and then allowing them to be statically cultured to form a bacterial cellulose film at the gas-liquid interface. The bacterial cellulose film is then removed from the surface of the culture medium. The dynamic fermentation process involves inoculating bacteria into a culture medium for dynamic fermentation, allowing the bacteria to synthesize bacterial cellulose within the liquid to form a bacterial cellulose slurry, which is then collected by centrifugation and / or filtration.

2. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, The modification treatment is carried out during static fermentation or dynamic fermentation.

3. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, When preparing bacterial cellulose using static fermentation, step S2 involves modifying the bacterial cellulose film removed from the surface of the culture medium.

4. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, When preparing bacterial cellulose using dynamic fermentation, step S2 involves modifying the bacterial cellulose slurry.

5. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, The chemical modification is as follows: grafting the bacterial cellulose with a compound containing a target functional group, wherein the target functional group in the compound is selected from at least one of the following general formulas: general formula (I) containing an antibacterial group, general formula (II) containing an antiviral group, general formula (III) containing a hydrophobic group, general formula (IV) containing a melanin-blocking group, or general formula (V) containing an antioxidant group. The general formula (I) is R1-N + (CH3)2-(CH2) n -X - Where R1 is C 12 -C 18 Alkyl or containing C 12 -C 18 Alkyl chain organic macromolecular groups, n=2-6, X - It is a halide anion; The general formula (II) is R2-(CH2). m -COOH, where R2 is a substituted phenyl group, m=1-3; The general formula (III) is R3-Si(OCH3)3, where R3 is a perfluoroalkyl chain C6F. 13 -C8F 17 ; The general formula (IV) is R4-Ar-Y, where R4 is -OCH3 or -NH-; Ar is phenolic hydroxyphenyl; and Y is -OH, -NH2, -COOH or -CONH2. The general formula (V) is R5-BZ, where R5 is a linking group used to graft the group onto bacterial cellulose, and is -O- or -NH-; B is a cyclic structure derived from catechol, phenolic hydroxyphenyl, thiol phenyl, or ascorbic acid; and Z is -OH, -OCH3, -COOH, or -NH2.

6. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, The chemical modification involves adding a vitamin B3 derivative or a thiol compound to the bacterial cellulose.

7. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, The physical modification involves forming ionic bonds, hydrogen bonds, or van der Waals forces on the surface of bacterial cellulose through post-treatment.

8. The method for preparing modified bacterial cellulose according to claim 1, characterized in that, After completing the modification treatment in step S2, the following steps are also included: post-processing the modified system to obtain modified bacterial cellulose; The post-processing can be one of the following methods: a. The first system after modifying the bacterial cellulose film obtained from static fermentation is sequentially subjected to molding, washing and drying to obtain membrane-like modified bacterial cellulose. b. The second system after direct modification of bacterial cellulose slurry is washed, dried and ground in sequence to obtain powdered modified bacterial cellulose; c. The second system after direct modification of bacterial cellulose slurry is coated onto the fabric base, and the fabric base is dried to obtain functional bacterial cellulose fabric.

9. The method for preparing modified bacterial cellulose according to claim 8, characterized in that, The solid content of the second system is 0.5 wt.%-20 wt.