Preparation method of bacterial cellulose Pickering emulsion based on temperature control segmented enzymolysis and low-temperature two-stage homogenization

Abstract

The invention relates to a bacterial cellulose Pickering emulsion preparation method based on temperature control segmented enzymolysis and low-temperature two-stage homogenization, and belongs to the field of emulsion stabilizer preparation and application thereof. According to the method, bacterial cellulose is taken as a raw material, and a temperature control gradient enzymolysis procedure is implemented under the synergistic effect of a natural polyphenol auxiliary system and a compound enzyme system, that is, segmented reaction is carried out at a plurality of temperature stages (40 DEG C, 45 DEG C and 50 DEG C), so that the cellulose depolymerization rate and the particle formation size are effectively controlled. And mixing the obtained enzymatic hydrolysate with an oil phase, and carrying out two-stage high-pressure homogenization (50 MPa + 90 MPa) treatment under the condition of 0-5 DEG C to prepare the Pickering emulsion which is uniform in particle size, compact in structure and excellent in storage stability. The method does not depend on chemical modifiers, is green in process and controllable in parameters, and is suitable for development and application of natural emulsifiers in the fields of foods, cosmetics, medicines and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of natural emulsion stabilizer preparation, food and functional material processing, and relates to a bacterial cellulose Pickering emulsion preparation method based on temperature-controlled segmented enzymatic hydrolysis and low-temperature two-stage homogenization. BACKGROUND

[0002] Bacterial cellulose (BC) is a natural polysaccharide synthesized by microorganisms, and its basic structural unit is β-D-glucose. The molecular chain is connected by β-1, 4-glycosidic bond to form a three-dimensional network nanometer structure. Compared with plant cellulose, BC has the advantages of high purity, high crystallinity, large mechanical strength, large specific surface area, good biocompatibility and strong degradability, and thus has wide application potential in the fields of food, cosmetics, biological medicine and the like.

[0003] In recent years, with the growing demand for green, non-toxic and efficient emulsion systems, Pickering emulsion has gradually become an important direction to replace traditional surfactant emulsion. Pickering emulsion is an emulsion system stabilized by solid particles at the oil-water interface. The particles used can be firmly adsorbed at the oil-water interface to form a spatial barrier, inhibit the coalescence of emulsion droplets and phase separation, and thus achieve the stability of the emulsion. BC can form nanoscale fibrous particles after nanocrystallization treatment, which not only has good interfacial activity and adsorption performance, but also can form a synergistic stabilizing effect through physical barrier and network structure, and thus is widely studied for preparing Pickering emulsion system.

[0004] At present, there are many patents and documents reporting the preparation method of Pickering emulsion stabilized by nanocellulose. For example, patent CN115232328A discloses a Pickering emulsion prepared by nanocellulose with ribbon shape, and its preparation method relies on ultrasonic or physical homogenization emulsification; patent CN118562152A uses cellulose nanocrystals (CNC) and functional polymers to realize emulsion stabilization through electrostatic self-assembly at the oil-water interface; and patent CN118325346A uses sulfonated CNC to embed fat-soluble active substances to prepare a composite emulsion system. However, these methods generally have the following problems: (1) Many of them rely on physical crushing, chemical modification (such as sulfonation and grafting) to treat cellulose, which not only has a complex process, but also has the risk of introducing chemical residues or toxicity; (2) The emulsion stabilization strategies used are mostly single, which is difficult to balance the dispersibility of nanometer particles and the control of emulsion particle size; (3) The particle size of the nanometer particles is large or the distribution is not uniform, which leads to limited emulsion stabilization time and poor long-term storage performance; (4) Some of the stabilizers used in the method are not natural, which is difficult to meet the use requirements in high safety fields such as food and cosmetics.

[0005] Therefore, developing a green, safe, simple process, controllable particle size, and excellent emulsion stability BC-based Pickering emulsion preparation method is a key problem to be solved in the current field. SUMMARY

[0006] The present application aims to solve the following problems existing in the preparation of cellulose Pickering emulsion: wide particle size distribution of cellulose nanoparticles, low interfacial activity, unstable emulsion, and complex modification steps with chemical residues. To this end, the present application provides a bacterial cellulose Pickering emulsion preparation method based on temperature-controlled segmented enzymolysis and low-temperature two-stage homogenization, which is green and efficient, and can prepare an emulsion system with concentrated particle size, strong interfacial activity, and excellent storage stability.

[0007] The technical solution of the present application is as follows: One of the technical solutions of the present application provides a bacterial cellulose Pickering emulsion preparation method based on temperature-controlled segmented enzymolysis and low-temperature two-stage homogenization, comprising the following steps: S1. Temperature-controlled gradient complex enzymolysis: adding natural polyphenols, cellulase and xylanase to the BC suspension, and performing enzymolysis according to the segmented temperature control mode; after the enzymolysis reaction is completed, the enzyme is inactivated, cooled to room temperature, and the pH is adjusted to obtain a bacterial cellulose enzymolysis solution; S2. Shear emulsification: mixing the bacterial cellulose enzymolysis solution with the oil phase, and shearing to obtain a preliminary emulsion; S3. Low-temperature two-stage high-pressure homogenization: the preliminary emulsion is alternately treated by the first-stage pressure system and the second-stage pressure system in sequence to obtain the final emulsion, i.e. the bacterial cellulose Pickering emulsion.

[0008] Further, the preparation method of the BC suspension in step S1 is as follows: cutting the purified bacterial cellulose membrane, dispersing it in deionized water, and obtaining the BC suspension after shearing; the shearing speed is 10000-16000 rpm, the shearing time is 5-10 min, and the mass concentration of the obtained BC suspension is 0.5-1%; Further, the natural polyphenol in step S1 is any one or a combination of tannic acid, procyanidine, and epigallocatechin gallate (EGCG), and the mass concentration of the natural polyphenol added in the BC suspension is 0.01-0.5%; the pH of the BC suspension after adding the natural polyphenol is preferably 4.5-5.5; the enzyme activity ratio of the cellulase and xylanase is 1:1-3:1, and the total addition amount is 500-1500 U / g of dry BC mass; The enzymolysis in step S1 is a segmented gradient temperature control, and is carried out at three temperature nodes of 40℃, 45℃ and 50℃, respectively, and each temperature node is 6-12 hours, and the total time is 18-36 hours; or the enzymolysis is a programmed temperature gradient control, and is slowly increased from 40℃ to 50℃ at a temperature increasing rate of 0.5-1.0℃ / h, and then is kept at 50℃ for 8-12 hours; the programmed temperature gradient control is closer to the gradient of natural temperature change, and can avoid the impact of temperature sudden change on the enzyme activity, and is suitable for the scene that needs to moderately control the enzymolysis process.

[0009] Further, the enzyme inactivation condition in step S1 is 92-99℃, and the time is 5-30min; preferably, 95℃, and 20min; the enzyme inactivation can be realized by using a water bath, a metal bath and the like; and the pH adjustment refers to adjusting the pH to 6.8-7.2, preferably 7.0.

[0010] Further, the oil phase in step S2 comprises at least any one or a combination of carvacol, limonene, thymol, cinnamaldehyde, eugenol or menthol; The use amount ratio of the bacterial cellulose enzymolysis liquid to the oil phase is 1:9-3:7 in volume ratio; The shearing pre-emulsification speed is 5000-15000 rpm, and the time is 5-10 min; Further, the treatment temperature in step S3 is 0-5℃; the pressure of the first-stage pressure system is 50 MPa, and the pressure of the second-stage pressure system is 90 MPa; the number of times of the alternating treatment is 2-5 times; and the high-pressure homogenization device is a tandem double-stage homogenization pump, and a cooling module is arranged between the first-stage pressure system and the second-stage pressure system to ensure the low-temperature state.

[0011] The second technical scheme of the present application provides a bacterial cellulose Pickering emulsion prepared by the above method. The average particle size of the Pickering emulsion is 80-200 nm, the PDI is less than 0.1, the absolute value of the Zeta potential is greater than 35 mV, and the emulsion is not obviously layered after standing for 30 days.

[0012] The third technical scheme of the present application provides the application of the above bacterial cellulose Pickering emulsion. The emulsion is used for preparing food, cosmetics, medicines or agricultural preparations, has the properties of antioxidant, anti-settling and controlled release, and can be used as an emulsion stabilizer for loading and controlled release of natural essential oil, plant functional oil and fat-soluble perfume.

[0013] The bacterial cellulose Pickering emulsion provided by the present application is particularly suitable for encapsulation and stabilization of functional oil phase components (such as essential oil, natural perfume and the like), and is helpful to improve the utilization efficiency and product safety.

[0014] The Pickering emulsion prepared by the present application has unique advantages in many fields due to its excellent biocompatibility and stability: it can be used as a natural emulsifier for functional beverages to avoid gastrointestinal irritation caused by traditional surfactants; it can load antioxidant essential oils (such as thymol) to prepare nanoemulsions, improve skin permeability, and reduce the irritability of essential oils; as a carrier for lipid-soluble drugs, it realizes drug controlled release through the biodegradability of bacterial cellulose particles, reduces the frequency of drug administration, and stabilizes plant-derived pesticides (such as carvacrol), reduces their photolysis and volatilization in the environment, and improves the utilization rate of pesticides.

[0015] Compared with the prior art, the present application has the following obvious advantages and beneficial effects: (1) Green and safe: The whole process does not depend on any toxic chemical modifier or surfactant, and is suitable for food, cosmetics, drugs and other high safety fields; in the prior art, part of the cellulose-based Pickering emulsion preparation relies on chemical modification (such as sulfonation, silanization, etc.) to introduce active groups to improve interfacial activity. These chemical reagents may remain in the product, limiting their application in food, baby cosmetics, oral drugs and other fields with extremely high safety requirements; the present application replaces chemical modifiers to realize efficient depolymerization and dispersion of cellulose through the synergistic effect of natural polyphenols and complex enzyme system. Polyphenols, as natural antioxidants, not only can regulate the enzymatic pathway, but also can enhance the biocompatibility of the emulsion; the complex enzyme (cellulase + xylanase) precisely breaks the glycosidic bond through biological catalysis, avoiding the toxicity risk brought by chemical reagents; (2) Accurate particle size control: complex enzyme synergistic + polyphenol assisted + temperature controlled depolymerization, product particle size is concentrated (80-200 nm), PDI is less than 0.1; the cellulose particles prepared by traditional physical crushing method (such as high pressure homogenization, ultrasonic treatment) have wide particle size distribution (usually >300 nm, PDI >0.2), mainly due to the uneven mechanical force leading to large differences in fiber fracture degree; single enzymatic method is prone to local over-degradation or insufficient degradation due to the influence of enzyme activity on temperature and pH fluctuations; (3) Strong emulsion stability: the low-temperature two-stage high-pressure homogenization process significantly improves the uniformity of emulsion particle size and storage stability, the Zeta potential is greater than 35 mV, and there is no stratification after 30 days of standing; in the prior art, the stability of the emulsion is often limited by the insufficient adsorption strength of the particles on the oil-water interface or the liquid drop coalescence; (4) Strong process replicability: the enzyme activity ratio, temperature control program, and high pressure parameters in the present application can be modularly adjusted; some existing preparation methods rely on specific equipment or complex reaction conditions, and parameter fluctuations easily lead to product performance differences, making it difficult to scale up; (5) Unpredictable effect: compared with plant fibers or single enzyme enzymatic system, the present system shows better particle size, dispersibility and interfacial stability.

[0016] In summary, this invention, through the combination of green processes and precise control, solves the bottlenecks in safety, stability, and scalability of existing cellulose-based Pickering emulsions, demonstrating significant technological innovation and application value. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation process of the bacterial cellulose Pickering emulsion of the present invention. Figure 2 Comparison of the appearance of Pickering emulsion under different treatment methods; Figure 3 Comparison of optical microscope images of emulsions. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0019] Unless otherwise specified, all raw materials used in this invention are not subject to any particular restriction on their source; they may be purchased commercially or prepared using conventional methods known to those skilled in the art. Unless otherwise specified, all reagents are of analytical grade, and all instruments are standard laboratory equipment.

[0020] Example 1: Temperature-controlled segmented enzymatic hydrolysis for the preparation of bacterial cellulose particles The preparation steps provided in this embodiment are the same as those in Example 2. Figure 1 : 1. Material preparation: Take the bacterial cellulose membrane obtained by static fermentation for 7 days, treat it with 1% NaOH at 95℃ for 4 h to remove impurities, and wash it repeatedly with deionized water until neutral to obtain purified bacterial cellulose membrane.

[0021] 2. Preparation of suspension: The bacterial cellulose membrane was cut into pieces, deionized water was added, and the mixture was processed using a high-speed shear machine (12000 rpm, 8 min) to obtain a uniform bacterial cellulose suspension with a concentration of 1%.

[0022] 3. Temperature-controlled segmented enzymatic hydrolysis: Add 0.05% tannic acid (natural polyphenol) to 100 mL of suspension, adjust pH to 5.0, add a mixture of cellulase and xylanase (enzyme activity ratio 2:1, total addition 1000 U / g), and perform enzymatic hydrolysis sequentially at 40℃, 45℃, and 50℃, with each stage of reaction lasting 8 hours, for a total reaction time of 24 hours. After the reaction, inactivate the enzymes in a 95℃ water bath for 20 min, cool, and adjust pH to 7 to obtain the bacterial cellulase hydrolysate.

[0023] Particle size analysis: DLS measured the average particle size to be 172.3 nm, the PDI to be 0.11, the Zeta potential to be -43.2 mV, and the suspension to be free of precipitation or flocculation.

[0024] In this embodiment, bacterial cellulose membranes are prepared by static fermentation. The selected bacterial strain is generally *Acetobacter*, preferably *Acetobacter xylinum*. Taking *Acetobacter xylinum* as an example, the process of preparing bacterial cellulose membranes by static fermentation is as follows: Activated *Acetobacter xylinum* seed culture is inoculated into HS medium (pH=4.7) at an inoculation rate of 5%-10%, and statically cultured at a constant temperature of 30℃. After 7 days, the cellulose membrane formed at the gas-liquid interface is collected. After 7 days of static culture, the thickness of the cellulose membrane at the gas-liquid interface can reach 1.0-3.0 mm, with a dense structure and high water content (approximately 99%). At this point, the mechanical strength and uniformity of the membrane are suitable for subsequent processing.

[0025] Example 2: Preparation of Pickering Emulsion 1. Shear emulsification: The bacterial cellulase hydrolysate obtained in Example 1 was mixed with carvacrol at a volume ratio of 7:3 and subjected to high-speed shearing (14000 rpm, 8 min) to form a primary emulsion; 2. Two-stage high-pressure homogenization treatment: The primary emulsion is passed through two high-pressure homogenization systems (first stage 50 MPa, second stage 90 MPa) at 4°C, and the process is repeated 3 times. Emulsion characterization: The final emulsion had an average particle size of 95.4 nm, a PDI of 0.06, and a Zeta potential of -48.1 mV. The emulsion showed no stratification after standing for 30 days, and the droplets were stable and uniformly distributed.

[0026] Comparative Example 1: Enzymatic hydrolysis treatment without polyphenols The procedure is the same as in Example 1, except that tannic acid is not added.

[0027] The experimental results are shown in Table 1: the obtained nanoparticles have a particle size of 196.3 nm and a PDI of 0.22. After preparing the emulsion, the particle size is 196.3 nm, and obvious stratification occurs after standing for 30 days.

[0028] In Example 2, the addition of tannic acid resulted in smaller nanoparticle sizes (172.3 nm vs 196.3 nm) and lower PDI (0.06 vs 0.22) after enzymatic hydrolysis. The particle size difference was significant after preparing the emulsion, and Comparative Example 1 showed slight stratification after standing for 30 days. This indicates that tannic acid can assist enzymatic hydrolysis in refining particles and improving emulsion stability, possibly due to the binding of polyphenols and cellulose, regulating the enzymatic hydrolysis pathway or promoting particle dispersion.

[0029] Comparative Example 2: Single-temperature enzymatic hydrolysis treatment The enzymatic hydrolysis process was fixed at 50°C for 24 hours, while the other steps remained the same.

[0030] The experimental results are shown in Table 1: the obtained emulsion had a particle size of 132.4 nm, a PDI of 0.17, a Zeta potential of -34.5 mV, and obvious stratification after standing for 30 days.

[0031] Example 2 employed segmented enzymatic hydrolysis at 40℃-45℃-50℃, while Comparative Example 2 used a single enzymatic hydrolysis at 50℃. The emulsion from Example 1 exhibited smaller particle size (95.4nm vs 132.4nm), lower PDI (0.06 vs 0.17), and superior stability (no stratification after 30 days vs stratification within 3 days). This indicates that segmented temperature-increase enzymatic hydrolysis can more precisely control the degradation process, generating particles with uniform size and good dispersibility, which is beneficial for emulsion stability; single high-temperature enzymatic hydrolysis is prone to over- / uniform degradation, affecting emulsion performance.

[0032] Comparative Example 3: Plant Fiber Replacing BC As shown in Table 1: When modified coconut fiber replaces bacterial cellulose, the emulsion particle size after compound enzymatic hydrolysis and high-pressure homogenization is 278.6 nm, PDI is 0.28, Zeta potential is -25.7 mV, and phase separation occurs within 24 h.

[0033] Comparative Example 3 used modified coconut fiber (plant fiber) to replace bacterial cellulose. The resulting emulsion had a large particle size (278.6 nm) and a high PDI (0.28), and separated into layers within one day. Bacterial cellulose has a regular molecular structure and high crystallinity. After enzymatic hydrolysis, the resulting nanofibers / particles have better dispersibility and interfacial activity, making it a high-quality raw material for preparing stable Pickering emulsions. Plant fiber has a complex composition (containing impurities such as lignin and hemicellulose), and the enzymatic hydrolysis products are difficult to disperse evenly, making the emulsion prone to instability.

[0034] Comparative Example 4: No high-pressure homogenization, only shear emulsification The slurry from Example 1 was subjected to shearing at 14,000 rpm only, without high-pressure homogenization.

[0035] The experimental results are shown in Table 1: the obtained emulsion has a particle size of 211.9 nm, a PDI of 0.18, a Zeta potential of -33.4 mV, and aggregates formed at the interface after 10 days.

[0036] Comparative Example 4, which only underwent shear emulsification without high-pressure homogenization, resulted in a large emulsion particle size (211.9 nm vs. 95.4 nm) and instability within 10 days. This indicates that two-stage high-pressure homogenization (50 MPa, 90 MPa) can further break down droplets, refine particle size, and improve emulsion uniformity and stability; simple shearing is insufficient to achieve ultrafine droplet dispersion, and the emulsion is prone to instability due to droplet aggregation during storage.

[0037] Comparative Example 5: No enzymatic hydrolysis performed As shown in Table 1, the BC suspension was directly used for emulsion preparation. After shearing and two-stage high-pressure homogenization, the emulsion particle size was 318.2 nm, the PDI was 0.31, the Zeta potential was -29.1 mV, and severe stratification occurred within 1 day.

[0038] Comparative Example 5, without enzymatic hydrolysis, directly prepared an emulsion from the BC suspension. This emulsion exhibited a large particle size (318.2 nm) and a high PDI (0.31), and separated into layers within one day. This indicates that enzymatic hydrolysis can degrade bacterial cellulose, reducing fiber length and entanglement, and generating nanoscale particles with a large specific surface area and strong interfacial activity. These particles can effectively adsorb onto the oil phase interface, stabilizing the emulsion. In contrast, the un-enzymatically hydrolyzed BC fibers are long, poorly dispersed, and difficult to uniformly coat oil droplets, leading to easy emulsion separation.

[0039] Table 1. Comparison of Test Results like Figure 2 As shown, in Example 2, from day 1 to day 30, the emulsion appeared uniform without stratification or precipitation, maintaining a milky white liquid state. This indicates that the Pickering emulsion prepared therein has excellent stability, consistent with the "no stratification after 30 days" data in Table 1. The interfacial film formed after high-pressure homogenization of the bacterial cellulose enzymatic hydrolysis products is strong and can inhibit oil phase aggregation and emulsion instability for a long time. In Comparative Example 1, the emulsion was uniform on day 1, but slight stratification appeared on day 30 (a small amount of clear liquid on the surface). Due to the lack of tannic acid, the dispersibility of the enzymatic hydrolysis particles was poor, and the particles gradually aggregated during storage, making it impossible to stably coat the oil phase, verifying the "stratification after 30 days" result in Table 1, demonstrating the key role of tannic acid in the long-term stability of the emulsion. In Comparative Example 3, the emulsion showed signs of flocculation on day 1 (visually less uniform than the previous two), and completely stratified and demulsified on day 30. The lack of effective enzymatic hydrolysis control, coupled with the use of plant fiber raw materials, resulted in poor particle dispersion and weak interfacial activity, leading to the instability of the emulsion within a short period of time. This aligns with the conclusion of "stratification within 24 hours" in Table 1, highlighting the advantages of bacterial cellulose as a raw material.

[0040] like Figure 3As shown, in Example 2, the droplets were small in size and extremely uniformly distributed, with almost no aggregation. Corresponding to a particle size of 95.4 nm and a PDI of 0.06 in Table 1, the synergistic effect of two-stage high-pressure homogenization, segmented enzymatic hydrolysis, and tannins ensured uniform dispersion of bacterial cellulose particles, stabilized the adsorption oil phase interface, and prepared an emulsion with a well-defined microstructure, providing the microscopic basis for 30-day stability. In Comparative Example 1, the droplets were slightly larger in size and had a small number of agglomerated areas. Due to the lack of tannins to aid dispersion, the enzymatically hydrolyzed particles easily aggregated, resulting in decreased droplet dispersibility at the microscopic level, corresponding to "particle size 196.3 nm, PDI 0.22" in Table 1. Agglomeration intensified during storage, macroscopically manifesting as stratification. In Comparative Example 3, the droplets were large in size, randomly distributed, and severely agglomerated. The enzymatic hydrolysis products of plant fibers contained many impurities and had uneven particle size, failing to effectively stabilize the droplets. The chaotic microstructure directly led to rapid macroscopic stratification of the emulsion, consistent with "particle size 278.6 nm, PDI 0.28" in Table 1 and the instability results.

[0041] In summary, the results indicate that the synergistic strategy of temperature-controlled segmented enzymatic hydrolysis combined with two-stage high-pressure homogenization significantly reduces emulsion particle size, improves homogeneity and electrical stability, and results in emulsion storage stability far superior to other treatment groups. The characteristics of bacterial cellulose raw materials, tannic acid-assisted enzymatic hydrolysis, segmented temperature-controlled enzymatic hydrolysis, and two-stage high-pressure homogenization are key to preparing stable Pickering emulsions. The synergistic effect of these factors, by refining particle size, improving dispersion uniformity, and enhancing emulsion stability, provides a direction for process optimization in the development of high-performance emulsions.

[0042] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing bacterial cellulose Pickering emulsion based on temperature-controlled segmented enzymatic hydrolysis and low-temperature two-stage homogenization, characterized in that, Includes the following steps: S1. Temperature-controlled gradient enzymatic hydrolysis: Natural polyphenols, cellulase, and xylanase are added to the bacterial cellulose suspension, and enzymatic hydrolysis is carried out in a segmented temperature-controlled manner; after the enzymatic hydrolysis reaction is completed, the enzymes are inactivated, cooled to room temperature, and the pH is adjusted to obtain bacterial cellulose hydrolysate. S2. Shearing emulsification: The bacterial cellulase hydrolysate is mixed with the oil phase and sheared pre-emulsified to obtain the primary emulsion; S3. Low-temperature two-stage high-pressure homogenization: The primary emulsion is alternately processed through the first-stage pressure system and the second-stage pressure system to obtain the final emulsion, namely bacterial cellulose Pickering emulsion.

2. The preparation method according to claim 1, characterized in that, The preparation method of the bacterial cellulose suspension in step S1 is as follows: the purified bacterial cellulose membrane is cut into pieces and dispersed in deionized water. After shearing, the bacterial cellulose suspension is obtained. The shearing speed is 10000-16000 rpm and the shearing time is 5-10 min, resulting in a bacterial cellulose suspension with a mass concentration of 0.5-1%.

3. The preparation method according to claim 1, characterized in that, The natural polyphenols mentioned in step S1 are any one or a combination of tannic acid, proanthocyanidins, epigallocatechin gallate, and tannins; the mass concentration of the added natural polyphenols is 0.01-0.5% of the bacterial cellulose suspension; the enzyme activity ratio of cellulase and xylanase is 1:1-3:1, and the total amount of cellulase and xylanase added is 500-1500 U / g dry bacterial cellulose mass.

4. The preparation method according to claim 1, characterized in that, The enzymatic hydrolysis described in step S1 is a segmented gradient temperature control, with the reaction carried out at three temperature nodes: 40℃, 45℃, and 50℃, for 6-12 hours at each temperature node, for a total time of 18-36 hours; or, the enzymatic hydrolysis is a programmed temperature gradient control, with the temperature slowly increased from 40℃ to 50℃ at a rate of 0.5-1.0℃ / h, and then held at 50℃ for 8-12 hours.

5. The preparation method according to claim 1, characterized in that, The enzyme inactivation conditions described in step S1 are a temperature of 92-99℃ and a time of 5-30 minutes; the pH adjustment refers to adjusting the pH to 6.8-7.

2.

6. The preparation method according to claim 1, characterized in that, The oil phase in step S2 contains at least one or a combination of carvacrol, limonene, thymol, cinnamaldehyde, eugenol, or menthol.

7. The preparation method according to claim 1, characterized in that, In step S2, the volume ratio of bacterial cellulose hydrolysate to oil phase is 1:9-3:7; the shearing pre-emulsification speed is 5000-15000 rpm, and the time is 5-10 min.

8. The preparation method according to claim 1, characterized in that, The processing temperature in step S3 is 0-5℃; the pressure of the first-stage pressure system is 50 MPa, and the pressure of the second-stage pressure system is 90 MPa; the number of alternating processes is 2-5 times; the high-pressure homogenizing device is a series two-stage homogenizing pump, and a cooling module is provided between the first-stage pressure system and the second-stage pressure system to ensure the low-temperature state is maintained.

9. A bacterial cellulose Pickering emulsion prepared by any one of the methods described in claims 1-8, characterized in that, The Pickering emulsion has an average particle size of 80-200 nm, a PDI of less than 0.1, an absolute value of Zeta potential greater than 35 mV, and no obvious stratification after standing for 30 days.

10. An application of the bacterial cellulose Pickering emulsion as described in claim 9, characterized in that, The emulsion is used in the preparation of food, cosmetic, pharmaceutical or agricultural formulations, and as an emulsifying stabilizer for loading and controlled release of natural essential oils, functional plant oils and fat-soluble fragrances.

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