KR20230169689A - Bacteria Cellulose-Milk Protein Complex and Method Thereof - Google Patents

Abstract

The present invention provides a porous structure comprising bacterial cellulose fibers; and a bacterial cellulose-milk protein particle complex comprising milk protein particles provided in pores inside the porous structure or on the surface of the porous structure, and a method for manufacturing the same. The bacterial cellulose-milk protein complex according to the present invention has excellent shape stability, washing fastness, spindle resistance, water resistance, and flame retardancy, so it can replace animal leather and can be used in flame-retardant articles made from leather.

Description

Bacteria Cellulose-Milk Protein Complex and Method Thereof}

The present invention relates to bacterial cellulose-milk protein complexes and methods for their preparation.

Natural leather is widely used in products such as clothing, furniture, and accessories, but its resources are limited and cannot fully meet demand, and supply and demand are further decreasing due to various environmental and animal protection issues. Artificial leather is used as a replacement for natural leather. Artificial leather refers to an artificial leather imitation made of non-woven fabric and polyurethane. The existing artificial leather currently used does not have as good flexibility and spindle resistance as animal leather, making it difficult to replace existing animal leather. In addition, some natural leathers exhibit flame retardant properties and are used in the manufacture of welding tool storage boxes, gloves and boots used for fire suppression, etc. However, supply is difficult due to animal protection and environmental issues, so animal leather, although flame retardant, is difficult to supply. There is a need for leather substitutes similar to these.

Republic of Korea Registered Publication No. 10-2192110 (2020.12.10)

One aspect includes a porous structure comprising bacterial cellulose fibers; and a bacterial cellulose-milk protein complex containing milk protein particles provided in pores inside the porous structure or on the surface of the porous structure, and artificial leather containing the same.

Another aspect includes mixing milk protein with purified water to produce a milk protein solution; Adding a cross-linking agent and a catalyst to the milk protein solution to create a mixture; immersing a porous structure containing bacterial cellulose fibers in the mixture to prepare a composite in which milk proteins are provided on at least a portion of the inner pores or surface of the porous structure; and drying the complex; to provide a method for producing a bacterial cellulose-milk protein complex, and a cellulose-milk protein complex produced thereby.

As used herein, the term 'composite' refers to an object containing two or more components. For example, 'bacterial cellulose-milk protein particle complex' includes bacterial cellulose and milk protein particles.

One aspect includes a porous structure comprising bacterial cellulose fibers; and providing a bacterial cellulose-milk protein complex including milk protein particles provided in pores inside the porous structure or on the surface of the porous structure.

The porous structure containing the bacterial cellulose fibers can be manufactured by methods known to those skilled in the art. For example, the porous structure may be manufactured by culturing bacterial cellulose gel (BC gel) with yeast extract, or it may be a porous structure manufactured from SCOBY (symbiotic culture of bacteria and yeast). For example, mixing carbon source powder such as glucose, sucrose, and mannitol with nitrogen source such as yeast extract and peptone powder with distilled water, heating, cooling at 25°C, and bacterial cellulose gel (BC gel). It can be prepared by repeating the steps of adding to the mixture and culturing for 8 days, then washing with NaOH, neutralizing with acetic acid, bleaching with H2O2, and drying. Specifically, the paper [Han, Shim and Kim. Effects of cultivation, washing, and bleaching conditions on bacterial cellulose fabric production. You can refer to the method described in [Textile Research Journal 2018, 89(6): 1094-1104].

The cellulose of the porous structure containing the bacterial cellulose fibers is manufactured through bacteria that produce cellulose, and any bacteria that can produce cellulose can be used.

According to one embodiment, the bacterial cellulose may be manufactured from Acetobacter xylinum, Komagataeibacter xylinus , or Gluconacetobacter xylinus .

According to one embodiment, the milk protein may be whey protein isolate (WPI) or casein.

According to one embodiment, the milk protein particles may be 30 parts by weight to 70 parts by weight, 40 parts by weight to 60 parts by weight, or 45 parts by weight to 55 parts by weight based on 100 parts by weight of the bacterial cellulose porous structure. The flame retardancy may be the best when the composite contains 45 to 55 parts by weight of milk protein particles based on 100 parts by weight of the bacterial cellulose porous structure.

The bacterial cellulose-milk protein particle complex may exhibit flame retardant properties. The flame retardancy refers to the property of a material that is difficult to burn, and can play a role in slowing or stopping the spread of a fire.

According to one embodiment, the bacterial cellulose-milk protein complex may further include a cross-linking agent.

The crosslinking agent may be citric acid, glucose, glyoxal, glutaraldehyde, polyacrylic acid, or BTCA (1,2,3,4-butanetetracarboxylic acid). . For example, it may be citric acid.

The cross-linking agent may have a concentration of 5% to 15% of the total, or may have a concentration of 50 to 150 parts by weight based on 100 parts by weight of bacterial cellulose. For example, citric acid may be 70 to 130 parts by weight based on 100 parts by weight of bacterial cellulose.

Other aspects include porous structures comprising bacterial cellulose fibers; and a bacterial cellulose-milk protein complex containing milk protein particles provided in pores inside the porous structure or on the surface of the porous structure.

According to one embodiment, the milk protein particles may be whey protein isolate (WPI) or casein.

According to one embodiment, the milk protein particles may be 30 parts by weight to 70 parts by weight, 40 parts by weight to 60 parts by weight, or 45 parts by weight to 55 parts by weight based on 100 parts by weight of the bacterial cellulose porous structure. The flame retardancy may be the best when the composite contains 45 to 55 parts by weight of milk protein particles based on 100 parts by weight of the bacterial cellulose porous structure.

The artificial leather may exhibit flame retardant properties. The flame retardancy refers to the property of a material that is difficult to burn, and can play a role in slowing or stopping the spread of a fire.

The artificial leather can be manufactured by laminating an elastic sheet attached to the opposite side of the outer skin and an inner skin attached to the back side of the elastic sheet. The outer shell can be coated with an acrylic-based or urethane-based resin to improve the texture, and can be embossed to create a natural leather pattern or geometric pattern on the outer shell.

Another aspect includes mixing milk protein with purified water to produce a milk protein solution; Adding a cross-linking agent and a catalyst to the milk protein solution to create a mixture; immersing a porous structure containing bacterial cellulose fibers in the mixture to prepare a composite in which milk protein particles are provided on at least a portion of the inner pores or surface of the porous structure; and drying the complex. To provide a method for producing a bacterial cellulose-milk protein complex including a step.

According to one embodiment, the step of generating the mixture may further include a protein denaturation process. The protein denaturation process may include titrating to pH 9 to pH 11 and cultivating with shaking, and the shaking culturing may be performed at 75 to 85°C. Additionally, the shaking culture may be performed at 60 to 100 rpm for 10 to 30 minutes.

According to one embodiment, the milk protein may be whey protein isolate (WPI) or casein.

According to one embodiment, the composition ratio of the crosslinking agent and catalyst may be 4:3 to 1:2.

According to one example, it was confirmed that flame retardancy significantly increased when the composition ratio of the crosslinking agent and catalyst was changed from 2:1 to 1:1, and that flame retardancy gradually decreased when changed from 1:1 to 1:2.

According to one embodiment, the cross-linking agent is citric acid, glucose, glyoxal, glutaraldehyde, polyacrylic acid, BTCA (1,2,3,4- butanetetracarboxylic acid). For example, it may be citric acid.

The cross-linking agent may have a concentration of 5% to 15% of the total, or may have a concentration of 50 to 150 parts by weight based on 100 parts by weight of bacterial cellulose. For example, citric acid may be 70 to 130 parts by weight based on 100 parts by weight of bacterial cellulose.

According to one embodiment, the catalyst may be sodium hypophosphite, titanium dioxide, hydrogen chloride, sulfuric acid, or potassium persulfate. For example, it may be sodium hypophosphite.

Another aspect includes mixing milk protein with purified water to produce a milk protein solution; Adding a cross-linking agent and a catalyst to the milk protein solution to create a mixture; immersing a porous structure containing bacterial cellulose fibers in the mixture to prepare a composite in which milk protein particles are provided on at least a portion of the inner pores or surface of the porous structure; and drying the complex. To provide a bacterial cellulose-milk protein complex prepared by a method for producing a bacterial cellulose-milk protein complex comprising.

The steps for producing the mixture, crosslinking agents, and catalysts are the same as described above.

The bacterial cellulose-milk protein complex can be used as artificial leather, and the artificial leather can be manufactured by laminating an elastic sheet attached to the opposite side of the outer skin and an inner skin attached to the back side of the elastic sheet. The outer shell can be coated with an acrylic-based or urethane-based resin to improve the texture, and can be embossed to create a natural leather pattern or geometric pattern on the outer shell.

The bacterial cellulose-milk protein complex according to the present invention has excellent shape stability, washing fastness, spindle resistance, water resistance, and flame retardancy, so it can replace animal leather and can be used in flame-retardant articles made from leather.

Figure 1 is a schematic diagram of a method for preparing bacterial cellulose-milk protein complex using a physical encapsulation method.
Figure 2 is a schematic diagram of a method for producing a bacterial cellulose-milk protein complex through cross-linking.
Figure 3 is a schematic diagram of a method for producing a bacterial cellulose-milk protein complex through physical encapsulation and cross-linking.
Figure 4A shows data confirming the appropriate content of whey protein isolate, which can significantly exhibit flame retardant properties when manufacturing a bacterial cellulose-milk protein complex, and Figure 4B shows the titration of casein, which can significantly exhibit flame retardant properties when manufacturing a bacterial cellulose-milk protein complex. This is data confirming the content.
Figure 5 shows data confirming the flame retardant properties of the bacterial cellulose-milk protein complex by changing the order of the physical encapsulation method and the cross-linking method.
Figure 6 is data showing the surface of a bacterial cellulose-milk protein complex prepared by changing the type of cross-linker and the shape when the complex is folded.
Figure 7 shows data confirming the degree of flame retardancy according to the content of citric acid, a cross-linking agent, when manufacturing a bacterial cellulose-milk protein complex.
Figure 8 shows data confirming the degree of flame retardancy according to the ratio of cross-linking agent and catalyst when producing a bacterial cellulose-milk protein complex.
Figure 9 is data analyzing the chemical structure by FT-IR, where A is a bacterial cellulose porous structure, a bacterial cellulose-milk protein complex (BC-WPI-ent) prepared by physical encapsulation using whey protein isolate, and whey protein isolate. FT-IR analysis results of bacterial cellulose-milk protein complex (BC-WPI-x) prepared by physical inclusion and cross-linking using B, B is bacterial cellulose porous structure, bacterial cellulose prepared by physical inclusion using casein. -This is the result of FT-IR analysis of milk protein complex (BC-casein-ent) and bacterial cellulose-milk protein complex (BC-casein-x) prepared by physical encapsulation and cross-linking using casein.
Figure 10 shows data analyzing the crystallinity by B is the XRD analysis result of the bacterial cellulose-milk protein complex (BC-WPI-x) prepared by physical inclusion and cross-linking, and B is the bacterial cellulose-milk protein complex prepared by physical inclusion using the bacterial cellulose porous structure, casein ( This is the result of XRD analysis of bacterial cellulose-milk protein complex (BC-casein-x) prepared by physical inclusion and cross-linking using BC-casein-ent) and casein.
Figure 11 is a photograph of the surface structure of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex observed by SEM.
Figure 12 shows data analyzed by EDS on surface elements of a bacterial cellulose porous structure and a bacterial cellulose-milk protein complex.
Figure 13 shows data confirming the flame retardant properties of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.
Figure 14 shows data confirming the contact angle of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.
Figure 15 is data confirming the degree of water absorption (degree of waterproofing) of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.
Figure 16 shows data confirming the degree of flexibility of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.
Figure 17 is data confirming the spindle diagram of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.
Figure 18 shows data confirming the morphological stability of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.
Figure 19 shows data confirming the washing fastness of the bacterial cellulose porous structure and the bacterial cellulose-milk protein complex.

Hereinafter, one or more embodiments will be described in more detail through examples. However, these examples are intended to illustrate one or more embodiments and the scope of the present invention is not limited to these examples.

Example 1. Preparation of porous structure containing bacterial cellulose fibers

Paper [Han, Shim and Kim. Effects of cultivation, washing, and bleaching conditions on bacterial cellulose fabric production. A porous structure containing bacterial cellulose fibers (bacterial cellulose structure) was fabricated, washed, and bleached according to the method described in Textile Research Journal 2018, 89(6): 1094-1104, and the paper [Song JE, Su J , Loureiro A, Martins M, Cavaco-Paulo A, Kim HR, Silva C (2017) Ultrasound-assisted swelling of bacterial cellulose. Swelling pretreatment was performed according to the method described in [Engineering in Life Science 17(10): 1108-1117.].

Example 2. Preparation of bacterial cellulose-milk protein complex via physical inclusion

Bacterial cellulose-milk protein complex through physical inclusion was prepared through the procedure shown in Figure 1. 0 to 60% by weight of whey protein isolate (WPI, Purunsan Agricultural Corp.) or casein extracted from cow milk (Casein, Sigma-Aldrich) compared to 100% by weight of the bacterial cellulose structure prepared in Example 1 in a beaker. It was placed in a container, and 10 times the amount of distilled water was added and mixed. Afterwards, it was denatured at pH 9.5 to pH 10.5 at 80 rpm for 20 minutes at 80°C, and 100% by weight of the bacterial cellulose structure was immersed and treated with ultrasonic waves at 25°C for 30 minutes. To prepare a bacterial cellulose complex encapsulating whey protein or casein, culture was performed at 30°C for 1 hour with shaking at 80 rpm. Afterwards, it was dried at 20°C for 24 hours to prepare a bacterial cellulose-milk protein complex through physical encapsulation.

Example 3. Preparation of bacterial cellulose-milk protein complex through cross-linking

The bacterial cellulose-milk protein complex through cross-linking was prepared through the procedure shown in Figure 2. 0 to 60% by weight of whey protein isolate (WPI, Purunsan Agricultural Corp.) or casein extracted from cow milk (Casein, Sigma-Aldrich) compared to 100% by weight of the bacterial cellulose structure prepared in Example 1 in a beaker. It was placed in a container, and 10 times the amount of distilled water was added and mixed. As a crosslinking agent, citric acid was mixed at 10 to 200% by weight based on 100% by weight of the bacterial cellulose structure, and sodium hypophosphite was mixed at 5 to 100% by weight based on 100% by weight of the bacterial cellulose. Afterwards, it was denatured at pH 9.5 to pH 10.5 at 80 rpm for 20 minutes at 80°C, and 100% by weight of the bacterial cellulose structure was immersed in the mixture. After 30 minutes, the immersed bacterial cellulose was taken out and cured at 160°C for 5 minutes to induce a crosslinking reaction. Afterwards, it was dried at 20°C for 24 hours to prepare a bacterial cellulose-milk protein complex through cross-linking.

Example 4. Preparation of bacterial cellulose-milk protein complex through physical inclusion and cross-linking.

The bacterial cellulose-milk protein complex through physical encapsulation and cross-linking was prepared through the sequence shown in Figure 3. 0 to 60% by weight of whey protein isolate (WPI, Purunsan Agricultural Corp.) or casein extracted from cow milk (Casein, Sigma-Aldrich) compared to 100% by weight of the bacterial cellulose structure prepared in Example 1 in a beaker. It was placed in a container, and 10 times the amount of distilled water was added and mixed. Then, as a crosslinking agent, citric acid was mixed at 10 to 200% by weight based on 100% by weight of the bacterial cellulose, and sodium hypophosphite was mixed at 5 to 100% by weight based on 100% by weight of the bacterial cellulose. It was denatured at pH 9.5 to pH 10.5 at 80 rpm for 20 minutes at 80°C, and 100% by weight of the bacterial cellulose structure was immersed and sonicated at 25°C for 30 minutes to physically encapsulate the protein. To prepare a bacterial cellulose complex encapsulating isolated whey protein or casein, culture was performed at 30°C for 1 hour with shaking at 80 rpm. Afterwards, it was cured at 160°C for 5 minutes to induce a crosslinking reaction. Afterwards, it was dried at 20°C for 24 hours to prepare a bacterial cellulose-milk protein complex through physical encapsulation and cross-linking.

Example 5. Selection of optimal content conditions for whey protein isolate and casein

TGA analysis was performed to confirm the optimal content of whey protein isolate and casein. TGA is the simplest method used to analyze flame retardancy. Through thermogravimetric analyzer, TA Instruments, Discovery SDT 650, USA, after burning at a high temperature of 1000°C, the weight ratio of the remaining residue was confirmed and compared.

As shown in Figure 4, it was confirmed that the amount of residue was the highest when whey protein isolate and casein were at 50% by weight, and therefore, it was confirmed that flame retardancy was the best when it was at 50% by weight relative to the weight of bacterial cellulose.

Example 6. Production method selection

In order to confirm the production method with the best flame retardancy using TGA in the same manner as in Example 5 above, bacterial cellulose fibers, bacterial cellulose-milk protein complex using only physical inclusion, and bacterial cellulose with crosslinking performed before and after physical inclusion were used. Thermogravimetric analysis was performed on the milk protein complex and the bacterial cellulose-milk protein complex in which cross-linking was performed simultaneously with physical inclusion as in Example 4.

As a result, as shown in Figure 5, the bacterial cellulose-milk protein complex that was cross-linked after physical encapsulation had significantly better flame retardancy, followed by the bacterial cellulose-milk protein complex that was cross-linked after physical encapsulation. It was confirmed that this was more remarkable than other fiber or protein complexes.

Example 7. Selection of cross linker

In order to select a suitable cross-linking agent for cross-linking, citric acid, sorbitol, polyethylene glycol (PEG 400), ethylene glycol, and glucose were used as cross-linking agents to prepare bacterial cellulose-milk protein complex. did. After preparation, thermogravimetric analysis (TGA) was performed on the bacterial cellulose-milk protein complex prepared with each cross-linking agent. In the case of citric acid, sodium hypophosphite was used as a catalyst.

As a result, as shown in Table 1 below, flame retardancy was highest when glucose was used as the cross-linking agent, and flame retardancy was confirmed to be high when ethylene glycol and citric acid were used as the cross-linking agent in that order.

Sample Protein Crosslinker Catalyst Residual wt% at 1,000℃ Crosslinking only WPI Citric acid Sodium hypophosphite 15.255 Crosslinking only WPI Sorbitol - 11.012 Crosslinking only WPI PEG 400 - 5.708 Crosslinking only WPI Ehylene glycol - 16.224 Crosslinking only WPI Glucose - 27.531

However, as shown in Figure 6, it was confirmed that the bacterial cellulose-milk protein (WPI) complex prepared using citric acid as a cross-linking agent and sodium hypophosphite as a catalyst had a similar feel to existing bacterial cellulose fibers and was very flexible. In the case of bacterial cellulose-milk protein (WPI) complexes prepared using other cross-linking agents, all of them had a paper-like appearance and feel, and were confirmed to be made of a stiff material, so when bent, they folded in half rather than bending flexibly. did.

Therefore, the flame retardancy was highest when glucose was used as a cross-linking agent, but the bacterial cellulose-milk protein complex that maintains the leather texture and is flame retardant is a bacterial cellulose-milk protein complex prepared using citric acid as a cross-linking agent and sodium hypophosphate as a catalyst. It was confirmed that.

Example 8. Selection of optimal citric acid content

In order to confirm the optimal content of citric acid when manufacturing a bacterial cellulose-milk protein complex showing flame retardant properties, flame retardancy according to the citric acid content was confirmed. Flame retardancy was confirmed using TGA. The citric acid content was expressed as a percentage calculated based on the mixture.

As a result, as shown in Figure 7, it was confirmed that both whey protein isolate and casein had the highest flame retardancy when the citric acid concentration was 10%, and that at higher concentrations, the flame retardancy decreased or appeared to a similar degree.

Example 9. Selection of ratio of crosslinking agent and catalyst

In order to confirm the optimal ratio of cross-linking agent and catalyst when preparing a bacterial cellulose-milk protein complex showing flame retardant properties, TGA analysis was performed.

As a result, as shown in Figure 8, it was confirmed that flame retardancy was significantly increased when the ratio of crosslinking agent and catalyst was 1:1.

Example 10. Surface analysis of bacterial cellulose-milk protein complexes

10-1. FT-IR analysis

The chemical structure of the bacterial cellulose-milk protein complex was analyzed using a FT-IR spectrophotometer (Nicolet IS50; Thermo Fisher Scientific, Waltham, MA, USA). Resolution 0.4 cm ^-1 with 32 scans, fruit tree 650 to 4000 cm ^-1 FT-IR spectra were collected over the range. The baseline of each spectrum was normalized using OMNIC software (Thermo Fisher Scientific, Waltham, MA, USA).

The results of the chemical structure analysis are as shown in Figure 9. In the bacterial cellulose-milk protein complex produced only by the physical inclusion method, an amide peak is observed at 1500~1700 cm ^-1 , but is not observed after cross-linking. confirmed. This was confirmed because the chemical structure changes as the bacterial cellulose structure and milk protein molecules combine due to cross-linking. It was confirmed that bacterial cellulose and milk protein are effectively chemically bonding through cross-linking.

10-2. XRD analysis

The crystallinity of the bacterial cellulose-milk protein complex was confirmed using XRD (X-ray diffraction, D8 ADVANCE diffractometer; Bruker AXS Inc.).

As shown in Figure 10, it was confirmed that the intensity of the cellulose peak decreased overall after crosslinking. In addition, as shown in Table 2 below, it was confirmed that after cross-linking, the crystallinity decreased compared to the physically encompassed or existing bacterial cellulose structure. It was assumed that this phenomenon occurred because the OH group of bacterial cellulose was cross-linked with isolated whey protein or casein molecules.

In addition, as shown in Table 2 below, it was confirmed that although the crystallinity was slightly reduced, it did not affect the strength of the bacterial cellulose-milk protein complex. Therefore, it was confirmed that bacterial cellulose and isolated whey protein or casein molecules were effectively cross-linked.

Sample Crystallinity (%) Original B.C. 89.3±6.9 BC-WPI-ent 88.0±1.1 BC-WPI-x 60.2±3.1 BC-casein-ent 89.9±0.8 BC-casein-x 62.4±4.6

10-3. FE-SEM analysis

To analyze the surface structure of the bacterial cellulose-milk protein complex, the surface was observed using FE-SEM (JSM-7800F Prime; JEOL Ltd.).

As shown in Figure 11, as a result of observing the surface structure, it was confirmed that the surface of the cross-linked bacterial cellulose-milk protein complex was tightly coated, while the bacterial cellulose-milk protein complex using only the physical encapsulation method was The internal fiber structure was visible, and it was confirmed that the isolated whey protein or casein molecules were not evenly distributed inside the fiber structure. Therefore, it was confirmed that the flame retardancy of the bacterial cellulose composite was improved because the isolated whey protein or casein was tightly coated on the surface of the bacterial cellulose structure through cross-linking.

10-4. EDS analysis

To analyze the elements on the surface of the bacterial cellulose-milk protein complex, EDS (JSM-7800F Prime; JEOL Ltd.) was used.

As shown in Figure 12 and Table 3, it was confirmed that the content of nitrogen (N) and phosphorus (P) elements significantly increased after crosslinking, and the content of sulfur (S) also increased. At this time, it was confirmed that the increased nitrogen and phosphorus are the main components of the flame retardant, and that the elemental content of phosphorus and nitrogen in the bacterial cellulose-milk protein complex significantly increases during cross-linking, showing a flame retardant effect.

Elements (wt%) Sample C N O P S Original B.C. 48.74 - 40.79 - - BC-WPI-ent 60.57 3.46 35.05 0.14 0.77 BC-WPI-x 52.02 6.62 32.18 8.26 0.92 BC-casein-ent 49.59 - 50.10 0.23 0.08 BC-casein-x 44.04 5.04 43.68 7.13 0.12

Example 11. Comparison of weight, thickness and flame retardancy of bacterial cellulose-milk protein complexes

Thickness, weight, and flame retardancy of the bacterial cellulose-milk protein complex were compared according to the manufacturing method.

As a result, as shown in Table 4 below, it was confirmed that the thickness of the bacterial cellulose-milk protein complex that was physically encapsulated and cross-linked was significantly increased compared to the thickness of the bacterial cellulose-milk protein complex that was physically encapsulated only. It was confirmed that the thickness of the cross-linked bacterial cellulose-milk protein complex was similar to the thickness of cow leather, but it was confirmed that it was significantly heavier than cow leather of similar thickness.

In addition, as shown in Figure 13, it was confirmed that the physically encapsulated and cross-linked bacterial cellulose-milk protein complex had significantly better flame retardant properties than the physically encapsulated bacterial cellulose-milk protein complex and cowhide of similar thickness. .

Fabric Thickness (mm) Weight (g/m ² ) Original B.C. 0.92±0.13 186.67±12.47 cowhide leather 0.72±0.14 466.67±18.26 BC-WPI-ent 0.20±0.03 127.80±8.61 BC-WPI-x 0.76±0.08 1036.80±92.89 BC-casein-ent 0.27±0.10 171.73±41.61 BC-casein-x 0.76±0.05 1053.2±76.60

Example 12. Durability confirmation

12-1. Contact angle analysis

To analyze the contact angle of water on the surface, water was dropped on the bacterial cellulose-milk protein complex and the contact angle (WCA, water contact angle) was checked.

As shown in Figure 14, the complex using only physical inclusion and whey isolate protein (BC-WPI-ent) had a smaller contact angle than regular cowhide, but the complex using only physical inclusion and casein (BC-casein-ent) ) was confirmed to have a larger contact angle than regular cowhide. However, it was confirmed that the composites (BC-WPI-x and BC-casein-x) prepared using physical encapsulation and cross-linking had significantly larger contact angles than cowhide leather.

12-2. Check the waterproof effect

To confirm the waterproof effect, water was dropped on the bacterial cellulose structure, cowhide, and bacterial cellulose-milk protein complex, and then the absorbency was checked.

As shown in Figure 15, it was confirmed that the bacterial cellulose-milk protein complex produced by the physical encapsulation method absorbed all water within 5 to 10 minutes. On the other hand, in the case of the bacterial cellulose-milk protein complex using both the physical encapsulation method and the cross-linking method, water was not absorbed even 10 minutes after dropping the water, and it was confirmed that all water was absorbed after 30 minutes.

Therefore, it was confirmed that the bacterial cellulose-milk protein complex prepared by physical encapsulation and cross-linking method absorbed relatively less water.

12-3. Check flexibility

To confirm the flexibility, the flexibility of bacterial cellulose structure, cowhide, and bacterial cellulose-milk protein complex was measured.

To check flexibility, KS K 0538 was performed using the heart-loop method. The size of the sample was modified to 5 cm × 10 cm, and the experiment time was modified to 1 minute to create a loop and check the change in each sample after 1 minute. All experiments were performed five times and the results were expressed as average values. It was confirmed that the more flexible the sample, the longer the difference between the length of the loop after 1 minute and the length of the initial loop.

As a result, as shown in Figure 16, it was confirmed that the bacterial cellulose-milk protein complex prepared only by the physical encapsulation method was more flexible than the bacterial cellulose structure, but less flexible than cowhide. On the other hand, the bacterial cellulose-milk protein complex manufactured using physical encapsulation and cross-linking showed a length difference of about twice that of cowhide, confirming that it had significantly superior flexibility.

12-4. Check spindle (Crease recovery)

Spindle degree is the property of returning to its original state without damage when the sample is bent and unfolded. The better the spindle degree, the better the durability of the composite. Therefore, to check the spindle angle, KS K 0550 was performed using the recovery angle method. The sample size was 5 cm × 10 cm, and the experiment time was 1 minute. The wrinkle recovery rate was calculated according to the following formula. All experiments were performed five times and the results were expressed as average values.

[ceremony]

Crease recovery (spindle degree %) = crease recovery angle (wrinkle recovery angle °) / 180° x 100

As a result of measuring the spindle degree, as shown in Figure 17, it was confirmed that the spindle degree of the bacterial cellulose-milk protein complex, excluding the bacterial cellulose-milk protein complex using the physical encapsulation method with casein, was significantly improved compared to the existing bacterial cellulose structure. In the case of the bacterial cellulose-milk protein complex using the physical inclusion method with casein, spindle measurement was not possible because it was stiff. In addition, it was confirmed that the bacterial cellulose-milk protein complex prepared through physical encapsulation and cross-linking had superior spindle strength than cowhide leather of similar thickness.

12-5. Check dimensional stability

Shape stability is the property of an object not changing its size or shape under conditions such as temperature and humidity. To confirm dimensional stability, KS K ISO 7771:1985 Determination of dimensional changes of fabrics induced by cold-water immersion was performed. The sample size was 5 cm To analyze shape stability, each sample was soaked in sodium dodecylbenzenesulfonate (C18H29NaO3S), a wetting agent, for a certain period of time and then dried to measure the degree to which the shape changed. Shape stability was calculated according to the formula below, and all experiments were performed 5 times and the results were expressed as the average value.

[ceremony]

Dimensional stability (shape stability %) = (dimension of sample after immersion/dimension of sample before immersion) × 100

As shown in Figure 18, the shape stability of the bacterial cellulose-milk protein complex produced by physically encapsulating and cross-linking whey protein isolate is the same as that of cowhide of similar thickness, with the shape remaining unchanged even after immersion in a wetting agent for 180 minutes and then drying. It was confirmed that it remained constant. In addition, the bacterial cellulose-milk protein complex produced by physically encapsulating and cross-linking casein maintained a constant shape when dried after immersion for 120 minutes, but it was confirmed that there was a slight change in shape after immersion for 180 minutes. In addition, it was confirmed that the bacterial cellulose-milk protein complex prepared by the physical encapsulation method had lower morphological stability than the bacterial cellulose-milk protein complex prepared by physical encapsulation and cross-linking, and the bacterial cellulose-milk protein complex prepared by the physical encapsulation method using whey protein isolate was confirmed to have lower morphological stability. In the case of cellulose-milk protein complex, it was confirmed that it changed significantly when dried after immersion for 180 minutes.

Therefore, it was confirmed that the bacterial cellulose-milk protein complex prepared by physical inclusion and cross-linking had significantly better shape stability than the bacterial cellulose-milk protein complex prepared using only physical inclusion.

12-6. Water washing fastness measurement

Water washing fastness was measured by the degree to which flame retardant properties remained after washing.

The bacterial cellulose-milk protein complex produced was described in the paper [Kim, Song, and Kim. Ex situ Coloration of Laccase-Entrapped Bacterial Cellulose with Natural Phenolic Dyes. The water washing fastness was measured according to the water washing fastness test method of [Journal of the Korean Society of Clothing and Textiles 2021, 45(5): 866-880.]. The complex was immersed in distilled water 50 times the weight of the bacterial cellulose-milk protein complex, and then washed in a water bath at 25°C for 30 minutes at a speed of 110 rpm. The washed bacterial cellulose-milk protein complex was dried at 25°C for 2 hours, cut into 1.5 × 1.5 cm pieces, exposed to a flame for 5 seconds, and the burned area was measured to calculate the area ratio of the sample before and after combustion.

As shown in Figure 19, the bacterial cellulose-milk protein complex produced by physically encapsulating and cross-linking whey protein isolate was found to maintain flame retardancy even after washing up to two times, and the bacterial cellulose-milk protein complex produced by physically encapsulating and cross-linking casein It was confirmed that one bacterial cellulose-milk protein complex can be washed repeatedly up to three times. On the other hand, it was confirmed that the flame retardancy of all bacterial cellulose-milk protein complexes produced by the physical encapsulation method was significantly reduced after washing. This means that the milk protein is tightly bound to the bacterial cellulose due to cross-linking, so the flame retardancy is maintained even after washing.

Example 13. Comparison of flame retardancy of bacterial cellulose-milk protein complexes according to cross-linking and physical inclusion.

In order to compare flame retardancy according to the production method, bacterial cellulose-milk protein complexes using whey protein isolate were produced using different production methods, and the flame retardancy was compared.

As a result, as shown in Table 5 below, it was confirmed that the flame retardancy of the bacterial cellulose-milk protein complex using only crosslinking (Crosslinking only) was significantly higher than that of the bacterial cellulose-milk protein complex using only the physical entrapment method (Entrapment only). It was confirmed that the flame retardancy of the bacterial cellulose-milk protein complex using entrapment and cross-linking (Entrapment+Crosslinking) was significantly increased compared to the bacterial cellulose-milk protein complex using only physical entrapment or cross-linking.

Sample Protein Crosslinker Catalyst Residual wt% at 1,000℃ Original B.C. WPI - - 3.080 Entrapment only WPI - - 7.524 Crosslinking only WPI Citric acid Sodium hypophosphite 15.255 Entrapment+Crosslinking WPI Citric acid Sodium hypophosphite 56.298

Example 14. Comparison of components of bacterial cellulose-milk protein complexes according to cross-linking and physical inclusion

In order to determine the cause of the difference in flame retardancy depending on the production method, bacterial cellulose-milk protein complexes using whey protein isolate were produced using different production methods, and EDS analysis was performed.

As a result, as shown in Table 6 below, the content of nitrogen (N), phosphorus (P), and sulfur (S) elements increased in the bacterial cellulose-milk protein complex produced using both physical inclusion and cross-linking methods. , In particular, it was confirmed that the phosphorus content increased significantly.

Sample Elements (wt%) C N O P S Original B.C. 48.74 - 40.79 - - Entrapment only 60.57 3.46 35.05 0.14 0.77 Crosslinking only 58.49 7.97 32.21 1.05 0.28 Entrapment + Crosslinking 52.02 6.62 32.18 8.26 0.92

Claims (9)

A porous structure containing bacterial cellulose fibers; and
A bacterial cellulose-milk protein complex comprising pores inside the porous structure or milk protein particles provided on the surface of the porous structure.
According to paragraph 1,
The milk protein is whey protein isolate (WPI) or casein,
Bacterial cellulose-milk protein complex.
Artificial leather comprising the composite of claims 1 to 2.
Mixing milk protein with purified water to produce a milk protein solution;
Adding a cross-linking agent and a catalyst to the milk protein solution to create a mixture;
immersing a porous structure containing bacterial cellulose fibers in the mixture to prepare a composite in which milk protein particles are provided on at least a portion of the inner pores or surface of the porous structure; and
A method of producing a bacterial cellulose-milk protein complex comprising the step of drying the complex.
According to paragraph 4,
The milk protein is whey protein isolate (WPI) or casein,
Method for preparing bacterial cellulose-milk protein complex.
According to paragraph 4,
The composition ratio of the cross-linking agent and catalyst is 4:3 to 1:2,
Method for preparing bacterial cellulose-milk protein complex.
According to paragraph 4,
The crosslinking agent is citric acid, glucose, glyoxal, glutaraldehyde, polyacrylic acid, and BTCA (1,2,3,4-butanetetracarboxylic acid). ,
Method for preparing bacterial cellulose-milk protein complex.
According to paragraph 4,
The catalyst is sodium hypophosphite, titanium dioxide, hydrogen chloride, sulfuric acid, and potassium persulfate.
Method for preparing bacterial cellulose-milk protein complex.
Bacterial cellulose-milk protein complex prepared by the production method of claims 4 to 8