Melanin-containing regenerated cellulose fiber and preparation method therefor

Abstract

The present application discloses a melanin-containing regenerated cellulose fiber and a preparation method therefor. The regenerated cellulose fiber of the present application internally contains uniformly dispersed melanin, and the mass ratio of melanin to cellulose is preferably 0.005-0.2:1. In the present application, melanin is creatively dispersed and firmly bound inside the fiber, and the present application solves for the first time the technical problem in the prior art of the gradually deteriorating color fastnesses of a melanin coating and a color masterbatch with use and washing. The ultraviolet resistance of the fiber does not gradually deteriorate during use, and the impacts of a medium material on the appearance, color and texture of the fiber are also avoided. The regenerated cellulose fiber of the present application is particularly suitable for preparing a high-performance biomass fiber material having ultraviolet resistance and radiation resistance effects.

Description

A regenerated cellulose fiber containing melanin and its preparation method

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese Patent Application No. 202411935210.X, filed on December 24, 2024, entitled "A Regenerated Cellulose Fiber Containing Melanin and a Method for Preparing the Same", and also claims priority to Chinese Patent Application No. 202510146762.0, filed on February 8, 2025, entitled "A Regenerated Cellulose Fiber Containing Melanin and a Method for Preparing the Same", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of biotechnology, specifically to a regenerated cellulose fiber containing melanin and a method for preparing the same. Background Technology

[0004] In daily life, the ubiquitous ultraviolet radiation from sunlight and potential environmental radiation threaten human health. Recent turbulent international situations and the looming threat of nuclear war have led to an increasing demand for radiation protection from both the military and the public. Technological advancements have also accelerated human exploration of the space environment, making the resistance to and adaptation to ultraviolet radiation and high-energy rays in space one of the main challenges for astronauts in manned spaceflight and space exploration. These scenarios share a common need: a new type of clothing material that can provide radiation protection simply by wearing it, while simultaneously meeting the performance requirements of biocompatibility, comfort, environmental friendliness, and sustainability.

[0005] Melanin, a molecule naturally present in most living organisms, resists ultraviolet and high-energy radiation. It is a polymer composed of monomers such as tyrosine or 3'4'-dihydroxyphenylpropylamine, widely found in animals (e.g., human skin and hair, cuttlefish ink), plants, and microorganisms. Melanin molecules absorb ultraviolet and other high-energy rays, converting their energy into heat (rather than free radicals), thus protecting living organisms from damage caused by free radicals frequently generated by high-energy rays. Black fungi resistant to nuclear radiation were discovered in the Chernobyl nuclear power plant ruins; their survival in high-intensity radiation was due to the secretion of high concentrations of melanin molecules. Furthermore, melanin possesses numerous beneficial materials science properties. For example, as a process and final stage in electron transfer within living organisms, it absorbs free electrons and scavenge free radicals, thus holding great potential applications in sun protection, skin care, industrial chemistry, electrochemistry, and electronic products. Melanin is also a type of brown to black natural pigment. It has extremely low solubility in water and is often used as a black coloring agent in food additives (such as the application of squid ink in the food industry). As a biological macromolecule, it is naturally biodegradable in the natural environment.

[0006] However, melanin is rarely used in textile materials at present. This may be related to the large polymer chains and complex tertiary structure of melanin molecules, and the academic community has not yet reached a unified understanding of the complex structure of melanin molecules. Because melanin molecules have extremely low solubility in neutral aqueous solutions and are difficult to dissolve in common organic solvents, conventional fabric dyeing processes struggle to allow large melanin particles to penetrate into the fiber interior, making it difficult for melanin molecules to adhere and bind. When preparing conventional chemical fibers, the large size of natural melanin particles makes it difficult to disperse in the spinning system, hindering the preparation of fibrils. Conventional methods require the use of other materials to bind and disperse the melanin before use. For example, combining natural melanin extracted from yak with polydimethylsiloxane (PDMS) to modify the surface of wool fabrics has enhanced the wool's UV protection function (UV protection factor level 198.48), photothermal properties, and hydrophobicity (hydrophobic angle 164°). Another example is the preparation of a melanin / titanium dioxide composite material, which was then used as a coating on the wool surface, significantly improving the fabric's UV resistance. Clearly, using melanin and a medium as a fabric coating or to prepare color masterbatches is a conventional technical approach for utilizing melanin. However, coating structures or color masterbatches require a medium to carry the melanin molecules, and the color fastness of the coating and masterbatch will gradually decrease with use and washing. Furthermore, adding melanin through coating methods makes it difficult to control the coating thickness on the fiber surface, which can significantly affect the fiber's appearance, color, and texture. Summary of the Invention

[0007] The purpose of this application is to provide a regenerated cellulose fiber containing melanin to enhance the performance of the regenerated cellulose fiber.

[0008] A regenerated cellulose fiber containing melanin, wherein the regenerated cellulose fiber contains uniformly dispersed melanin.

[0009] Optionally, the melanin is extracted from at least one of the following: cuttlefish ink, mammalian hair, or microbial fermentation.

[0010] Optionally, in the melanin-containing regenerated cellulose fiber, the mass ratio of melanin to cellulose is 0.005-0.2:1.

[0011] Preferably, in the melanin-containing regenerated cellulose fiber, the mass ratio of melanin to cellulose is 0.01-0.2:1.

[0012] Optionally, the regenerated cellulose fiber further contains uniformly dispersed proteins; the proteins contain carbohydrate-binding domains.

[0013] Optionally, the protein comprises a natural animal protein amino acid sequence; the N-terminus and C-terminus of the natural animal protein amino acid sequence are respectively connected to carbohydrate-binding domains;

[0014] Optionally, the amino acid sequence of the natural animal protein includes at least one of the following: spider silk protein amino acid sequence, squid beak protein amino acid sequence, and bee silk protein amino acid sequence;

[0015] Optionally, the amino acid sequence of the protein containing the squid beak protein amino acid sequence is shown in SEQ ID NO.1, the amino acid sequence of the protein containing the spider silk protein amino acid sequence is shown in SEQ ID NO.3, and the amino acid sequence of the protein containing the bee silk protein amino acid sequence is shown in SEQ ID NO.5.

[0016] Optionally, in the melanin-containing regenerated cellulose fiber, the mass ratio of protein to cellulose is 0.001-1:1;

[0017] Preferably, in the melanin-containing regenerated cellulose fiber, the mass ratio of protein to cellulose is 0.01-0.2:1.

[0018] A method for preparing regenerated cellulose fibers containing melanin includes:

[0019] Step 1) Add melanin to an alkaline solution and mix thoroughly to obtain a melanin dispersion;

[0020] Step 2) Mix the spinning solution raw materials containing cellulose, solvent and melanin dispersion evenly to obtain a spinning solution;

[0021] Step 3) Spinning is performed using the aforementioned spinning solution. During the spinning process, an acidic solution is used in a coagulation bath to coagulate the fibers, thereby obtaining the regenerated cellulose fibers containing melanin.

[0022] Optionally, in step one), melanin is first dissolved in a NaOH solution with a pH of 10-14 to remove impurities, and then dried to obtain melanin powder; then the melanin is added to an alkaline solution and mixed evenly to obtain a melanin dispersion.

[0023] Optionally, the solvent for the spinning solution in step two) may be at least one of lithium chloride / DMAc or imidazole chloride.

[0024] Optionally, the pH of the acidic solution used in step three) is 1-5. The acidic solution can be any of the strong acids such as sulfuric acid and hydrochloric acid, or it can be one of the organic acids or weak acids such as formic acid and acetic acid, or it can be one of the salts of a strong acid and a weak base.

[0025] Preferably, the acidic solution is a sulfuric acid solution with a pH range of 2-3.

[0026] Optionally, the spinning solution raw material further includes protein; the protein contains carbohydrate-binding domains;

[0027] Optionally, the protein comprises a natural animal protein amino acid sequence; the N-terminus and C-terminus of the natural animal protein amino acid sequence are respectively connected to carbohydrate-binding domains.

[0028] Optionally, the protein is synthesized by microorganisms;

[0029] Optionally, the protein is synthesized using the following method:

[0030] The nucleic acid sequence encoding the protein is transferred into microorganisms for culture to synthesize the protein and obtain a bacterial culture medium. The bacterial culture medium is then subjected to sonication and centrifugation, and the supernatant is used to purify the protein using a nickel column to obtain the protein.

[0031] Optionally, the nucleic acid sequence encoding the protein is any one of SEQ ID NO.2, SEQ ID NO.4, and SEQ ID NO.6.

[0032] This application also proposes the application of the aforementioned melanin-containing regenerated cellulose fibers in textile materials.

[0033] This application also proposes a textile material with anti-ultraviolet and anti-radiation effects, namely the above-mentioned melanin-containing regenerated cellulose fiber.

[0034] This application has the following beneficial effects:

[0035] This application disperses and binds melanin within the fiber, solving the problem in existing technologies where the colorfastness of melanin coatings and masterbatches gradually diminishes with use and washing. The fiber's UV resistance does not gradually decrease with use, and the influence of the medium on the fiber's feel is also avoided.

[0036] In existing cellulose-based composite systems, most are protein-cellulose composites, but the bonding effect between protein and cellulose is not ideal, failing to fully utilize the reinforcing effect of protein on the composite material. This application utilizes the solubility properties of melanin molecules to disperse melanin, making it easier to prepare fibers and other chemical materials. Simultaneously, this application draws inspiration from the beak structure of cephalopods (cuttlefish, squid, or octopus)—a structure composed of polysaccharide chains (chitosan), polyphenol chains (polytyrosine or polyphenolic tea), and proteins (cuttlefish beak proteins, etc.). This three-phase structure possesses good stability, endowing the beak structure with excellent mechanical strength and toughness. This application introduces melanin (polyphenols) into a cellulose (polysaccharide) and protein fiber system. These materials interact and bind together, creating either soft or hard structural materials through variations in their proportions.

[0037] This application presents a suitable solvent system for combining cellulose, melanin, and protein, enabling the composite preparation of these natural materials into high-performance bio-based fibers. This application innovatively combines melanin with cellulose, or adds recombinant animal proteins (modified spider silk protein, squid beak protein, bee silk protein, etc.) to a melanin-cellulose composite, firmly binding melanin within the fiber. This type of fiber can be used to prepare high-performance biomass fiber materials with UV resistance and radiation protection. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1. Stretching curves of melanin samples with different concentrations;

[0040] Figure 2. Stretching curves of spider silk protein samples with different concentrations;

[0041] Figure 3. Stretching curves of samples with different melanin / protein contents;

[0042] Figure 4. Stretching curves of samples with different spider silk protein contents;

[0043] Figure 5. Stretching curve of bee silk protein sample

[0044] Figure 6. Stretching curves of samples with different squid beak protein / melanin contents;

[0045] Figure 7. Comparison of melanin dissolution by different solutions;

[0046] Figure 8 Comparison of spinning solutions after dissolving melanin in different solutions;

[0047] Figure 9. Fiber diagrams with different amounts of added melanin;

[0048] Figure 10 shows the antioxidant test results of fibers containing composite melanin; where A is a photograph of the free radical scavenging experiment and B is the free radical scavenging efficiency.

[0049] Figure 11. SDS-page electrophoresis diagram of recombinant protein;

[0050] Figure 12. Physical image of composite melanin / spider silk protein fiber produced in industrial settings. Detailed Implementation

[0051] Various exemplary embodiments of this application are now described in detail. This detailed description should not be considered as a limitation of this application, but rather as a more detailed description of certain aspects, features, and implementations of this application. It should be understood that the terminology used in this application is merely for describing particular embodiments and is not intended to limit this application.

[0052] Furthermore, regarding the numerical ranges in this application, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0053] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art described herein. While only preferred methods and materials are described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this application.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] First, this application utilizes the fact that melanin molecules can dissolve or disperse into extremely small aggregates in alkaline aqueous solutions (pH>10), but aggregate and precipitate when the pH returns to neutral to acidic. This application leverages this property to directly freeze-dry or spray-dry alkaline solutions of melanin, thereby maintaining its nanoscale dispersion. The treated melanin remains soluble in aqueous solutions or is uniformly dispersed at the nanoscale.

[0056] This application utilizes the characteristic that melanin dissolves in alkaline aqueous solutions. An alkaline viscose fiber spinning system can be used to uniformly mix the dissolved melanin with an alkaline cellulose system dissolved in carbon disulfide, and then obtain black viscose fibers through wet spinning. Since the spinning coagulation bath is an acidic solution such as sulfuric acid, it can solidify melanin molecules while solidifying cellulose. The phenolic hydroxyl groups of the melanin molecules can form hydrogen bonds with the hydroxyl groups of the cellulose sugar chains, thus firmly binding them to the cellulose chains.

[0057] This application discovers that uniformly dispersed melanin molecules can be effectively dissolved in NMMO solutions, making them suitable for the preparation of cellulose fibers using a lyocell system. Furthermore, the applicant's proposed method for preparing regenerated cellulose fibers bound to recombinant proteins (CN118835343A) demonstrates that proteins with carbohydrate-binding domains (CBMs) can interact with cellulose in an NMMO system. Therefore, we utilize this system to add melanin molecules to the cellulose-protein interaction, forming a three-way interacting composite material: melanin can interact with cellulose chains via hydrogen bonds using phenolic hydroxyl groups; melanin can interact with the N-terminal amino residues of protein chains via aldehyde-amine condensation to form a Schiff base; and protein and cellulose can interact through the binding of CBMs and sugar chains.

[0058] This application prepares novel recombinant spider silk protein, squid beak protein, bee silk protein, and other animal proteins, which, together with the spider silk protein reported in the aforementioned patent, are used to further enhance the fiber effect. This application improves and adjusts the regenerated cellulose fiber system based on lyocell, replacing the coagulation bath with a weakly acidic solution with a pH of 2-3, thereby utilizing the change in material solubility due to pH to solidify and retain silk protein and melanin within the fiber.

[0059] Example 1: Design and Expression of Recombinant Proteins

[0060] This embodiment describes the preparation of the recombinant proteins used in the various embodiments and comparative examples. The amino acid and nucleic acid sequences of all recombinant proteins in this application are as follows:

[0061] Recombinant squid beak protein, containing the squid beak protein HBP-1 repeat region and connected to CBM at both ends, the amino acid sequence of CBM-HBP-1-CBM is SEQ ID NO.1, where positions 162-322 are the squid beak protein HBP-1 repeat region sequence;

[0062] The DNA sequence encoding the above CBM-HBP-1-CBM is SEQ ID NO.2.

[0063] Recombinant spider silk protein containing the MaSp2 spider silk protein repeat region and connected to CBM at both ends. The amino acid sequence of the recombinant spider silk protein is SEQ ID NO.3, where positions 160-353 are the MaSp2 spider silk protein repeat region sequence.

[0064] The DNA sequence encoding the above recombinant spider silk protein is SEQ ID NO.4.

[0065] Recombinant bee silk protein, containing the bee silk protein AF3 repeat region and connected to CBM at both ends, the amino acid sequence of CBM-AF3-CBM is SEQ ID NO.5, where positions 164-498 are the bee silk protein AF3 repeat region sequence;

[0066] The DNA sequence encoding the above CBM-AF3-CBM is SEQ ID NO.6.

[0067] All the above sequences were synthesized by BGI Genomics. The synthesized sequences were inserted into the commercial pET28a plasmid vector at the insertion site between BamHI and XhoI. Finally, the plasmid was transformed into Escherichia coli BL21(DE3) strain by chemical transformation (completed by BGI Genomics).

[0068] The constructed strain was fermented, purified, and freeze-dried to obtain recombinant protein powder, as detailed below:

[0069] (1) Shake-flask fermentation culture of bacterial cells

[0070] Once the strain was constructed, streak the preserved glycerol tubes onto a solid LB agar plate (containing 50 μg / ml kanamycin) and incubate overnight at 37°C. Pick single colonies and grow them overnight in 4-5 mL LB liquid medium (containing 50 μg / ml kanamycin) at 37°C and 200 rpm on a shaker. The next day, transfer 1% of the culture to a 400 mL shake flask for fermentation, incubating at 37°C and 200 rpm for 2-3 hours until OD600 = 0.6. Add isopropyl thiogalactoside (IPTG) to a final concentration of 0.3 mM and induce induction at 20°C for 12-16 hours. Centrifuge at 12000 rpm for 5 minutes and collect the bacterial cells.

[0071] (2) Protein purification

[0072] Reconstitute the bacterial cells with 20 mM Tris-HCl to prepare a concentrated bacterial solution with an OD600 of approximately 20. Sonicate at 25 kHz, 70-80% power, for 3 seconds followed by a 6-second pause, for a total of 30 minutes, until the solution changes from turbid to clear. Centrifuge at 12000 rpm for 10-15 minutes and collect the supernatant. Repeat the supernatant process 2-3 times through a packed nickel column (Sangon Biotech, product number NO. A600657), collecting the throughflow. Wash the column stock 3-5 times with 20 mM Tris-HCl (1-3 column volumes each time) until the eluent is clear. Wash the column stock at least 3 times with 1-2 column volumes of 0.5 M imidazole solution, collecting the eluent sequentially. Wash away any remaining 0.5 M imidazole solution with 5 column volumes of 20 mM Tris-HCl, and finally preserve with 20% ethanol. The washed column stock can be reused. Mix the collected protein eluents and then dialyze against pure water.

[0073] (3) SDS-PAGE electrophoresis

[0074] Prepare a 10% concentration SDS-PAGE gel (Beyotime, product number: P0012A).

[0075] Sample preparation and detection: 20 μL of the protein purification sample was added to 5 μL of loading buffer for SDS-PAGE detection. The electrophoresis results are shown in Figure 11.

[0076] (4) Freeze-dried protein

[0077] After dialysis, the protein solution was placed in a -80°C freezer until it was completely solidified. Then, it was freeze-dried at -55°C under a vacuum of 5 Pa. The freeze-dried protein was weighed to obtain purified recombinant spider silk protein powder.

[0078] Example 2: Pretreatment and dispersion of melanin molecules

[0079] This embodiment relates to a melanin molecule pretreatment and dispersion process, which specifically includes the following steps:

[0080] (1) Pretreatment of melanin: The melanin raw material used in this application was purchased from the microbial fermented melanin product of Shenzhen Lingzhu Technology Co., Ltd., and the melanin involved in this application also includes, but is not limited to, melanin extracted from microorganisms such as cuttlefish ink extract, mammalian hair extract, and microbial fermentation fungi and bacteria. The melanin raw material was added to a NaOH solution with pH=10-12 and stirred to dissolve. Then, the insoluble impurities in the melanin raw material were removed by centrifugation. The supernatant melanin solution was then freeze-dried to obtain purified melanin powder for later use.

[0081] (2) Dispersion of melanin: Prepare a NaOH solution with pH=10-12 in advance, dissolve and disperse the purified melanin pigment raw material in the NaOH solution, and stir and disperse overnight for 12 hours.

[0082] (3) Preparation of spinning solution: Wood pulp board with a cellulose content of 99 wt%, an ash content of 0.2 wt%, and an average degree of polymerization of 700 was used as the cellulose raw material. Recombinant spider silk protein raw material was purchased from Shenzhen Lingzhu Technology Co., Ltd. 120 g of 50% NMMO solution, 0.128 g of propyl gallate, a certain mass of spider silk protein powder, and melanin dispersion (concentration 2.5 g / L) were added to the spinning tank. Sodium hydroxide was added dropwise to adjust the pH of the solution to 10-12. The mixture was stirred until there were no obvious insoluble substances, and then 7.5 g of cellulose raw material was added, with the melanin solid content controlled at 5 wt% of the cellulose raw material mass fraction, and the spider silk protein powder content controlled to be consistent with the melanin solid content. The above mixture was stirred and dissolved at 95℃ and 90 kPa for 2-3 h until a transparent spinning solution was obtained.

[0083] The dissolution and dispersion of the composite melanin / recombinant spider silk protein lyocell fiber spinning solution were observed under a microscope. The dispersion effects of different dissolution processes were compared to select the optimal dissolution process.

[0084] Comparative Example 2

[0085] The only difference between this comparative example and Example 2 is that, in the melanin dispersion step (2) of a melanin molecule pretreatment and dispersion process, an aqueous solution with pH=7 is used to disperse the melanin powder. The other preparation processes and testing methods are exactly the same as in Example 2.

[0086] Comparative Example 3

[0087] The only difference between Comparative Example 3 and Example 2 is that in the melanin dispersion step (2) of the melanin molecule pretreatment and dispersion process, a NaOH solution with pH=10-12 is used to dissolve the melanin, but the overnight dispersion for 12 hours is not performed. The other preparation processes and testing methods are exactly the same as in Example 2.

[0088] Figures 7 and 8 show the physical images of Examples 2, 2, and 3, and their spinning solutions under a microscope, respectively. Figure 7 shows that in Comparative Example 2, dispersing melanin powder with an aqueous solution of pH 7 resulted in a clearly layered mixed solution, indicating that an aqueous solution of pH 7 is not conducive to melanin dispersion. In Example 2, dissolving melanin with a NaOH solution of pH 10-12 resulted in a uniformly dispersed mixed solution, indicating that the alkaline solution used in this application is more conducive to melanin dispersion. Figure 8 shows the microscopic images of the spinning solutions. In Comparative Example 2, the dispersion used to prepare the spinning solution contained a large number of obvious large particle aggregates under a microscope. In Comparative Example 3, melanin was dissolved in a NaOH solution of pH 10-12 but not stirred overnight; the resulting dispersion, after being prepared into a spinning solution, still contained a small amount of particulate matter under a microscope. In Example 2, melanin was dissolved in a NaOH solution of pH 10-12 and stirred overnight; the spinning solution under a microscope was transparent and free of particulate matter. Examples 2, 2, and 3 illustrate that the method of using alkali solution and overnight stirring dispersion in this application can obtain a uniformly dispersed melanin solution, which is very beneficial for the subsequent preparation of spinning solution and spinning.

[0089] Example 3: Preparation of Lyocell Fibers with Composite Microbial Melanin Molecules

[0090] This embodiment relates to a preparation process for a composite microbial melanin molecule lyocell fiber, which specifically includes the following steps:

[0091] (1) Microbial fermentation extraction of melanin: The melanin raw material is derived from microbial synthesis. Bacillus megaterium ACCC 11107 (purchased from Beijing Biotechnology Center) was cultured in 1L shake flasks containing 200ml LB medium (5g / L yeast extract, 10g / L peptone, and 10g / L sodium chloride, pH 7.0) for 48h. The pH was adjusted to 2-3 with 30% sulfuric acid. After ultrasonic disruption, the melanin precipitate was collected by centrifugation at 10000rpm for 2min. The precipitate was soaked in sulfuric acid solution with pH=3 for 2h, and the supernatant was removed by centrifugation at 10000rpm for 2min. The melanin precipitate was then freeze-dried to obtain the melanin raw material used in the test.

[0092] (2) Dispersion of melanin: The method is described in Example 2.

[0093] (3) Preparation of spinning solution: Wood pulp board with a cellulose content of 99 wt%, an ash content of 0.2 wt%, and an average degree of polymerization of 700 was used as the cellulose raw material. 120 g of 50% NMMO solution, 0.128 g of propyl gallate, and the above-mentioned melanin dispersion were added to the spinning tank and stirred until homogeneous. Then, 7.5 g of cellulose raw material was added, with the melanin solid content controlled at 1, 5, 10, and 20 wt% of the cellulose raw material mass fraction, respectively. The mixture was stirred and dissolved at 95℃ and 90 kPa for 2-3 hours until no obvious particulate matter was visible under a microscope, thus obtaining the spinning solution.

[0094] (4) Preparation of composite melanin lyocell fibers: The spinning solution was added to the spinning system and subjected to high-temperature filtration and degassing. The spinning solution was then pumped to the spinneret for dry-wet spinning. A spinning needle with an orifice diameter of 0.3 mm was used, the spinning speed was controlled at 30 m / min, the air gap was 20 mm, and the coagulation bath was a sulfuric acid solution at room temperature with a pH of 3. The high-viscosity spinning solution was vertically drawn into the coagulation bath after passing through an air section. As NMMO in the spinning solution was displaced to form fiber bundles, the melanin molecules in the fibers were solidified inside the fibers by the acidic coagulation bath, thus initially obtaining composite melanin lyocell fibers. The fibers were then immersed again in an acetic acid solution at room temperature with a pH of 3 for 10 min to further solidify the melanin. After repeated washing with hot and cold water to remove residual NMMO and acetic acid, oiling, drying, and cutting were performed to obtain the final composite melanin lyocell fibers.

[0095] The obtained composite melanin lyocell fiber was subjected to mechanical property tests, and its dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0096] Comparative Example 4

[0097] The only difference between Comparative Example 4 and Example 3 is that no melanin is added during the preparation process of the composite melanin lyocell fiber; the other preparation processes and testing methods are exactly the same as in Example 3.

[0098] Table 1. Mechanical data for Example 3 and Comparative Example 4

[0099] The mechanical property test results of Example 3 and Comparative Example 4 are shown in Table 1 and Figure 1. The strength and elongation of the lyocell fibers after melanin composite were significantly improved to varying degrees. The strength of the 20% melanin fiber was increased by 48.97% compared to the control fiber. This is because the interaction between the polyhydroxy structure of melanin and the hydroxyl groups of cellulose polysaccharides provides the fiber with excellent mechanical properties. Product images of fibers with different melanin contents are shown in Figure 9.

[0100] Example 4: Preparation of Lyocell fibers composed of squid ink melanin and recombinant spider silk protein

[0101] This embodiment relates to a process for preparing lyocell fibers composed of composite cuttlefish ink melanin and recombinant spider silk protein, which specifically includes the following steps:

[0102] (1) Extraction of melanin: Melanin was extracted from cuttlefish ink powder, which was purchased from Henan Zhongda Hengyuan Biotechnology Co., Ltd. 5g of ink powder was placed in 30mL of concentrated hydrochloric acid and reacted at 48-50℃ for 30min. The melanin precipitate was then collected by centrifugation at 10000rpm for 2min, soaked in sulfuric acid solution (pH=3) for 2h, and centrifuged again at 10000rpm for 2min to remove the supernatant. The melanin precipitate was then freeze-dried to obtain the melanin raw material used in the test.

[0103] (2) Dispersion of melanin: The preparation steps of the melanin dispersion are the same as in Example 3.

[0104] (3) Preparation of spinning solution: The preparation steps of spinning solution are the same as in Example 3, except that the content of added melanin solids is controlled to be 1, 5, 10 and 20 wt% of the mass fraction of cellulose raw materials, and recombinant spider silk protein dry powder with the same proportion as the melanin solids content is added, namely 1, 5, 10 and 20 wt% of recombinant spider silk protein.

[0105] (4) Preparation of Lyocell fiber with composite melanin and recombinant spider silk protein: The spinning steps are the same as in Example 3, except that the spinning solution is a melanin / recombinant spider silk protein mixed spinning solution.

[0106] The obtained composite melanin and recombinant spider silk protein lyocell fibers were subjected to mechanical property tests, and their dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0107] Comparative Example 5

[0108] The only difference between Comparative Example 5 and Example 4 is that no melanin is added during the preparation process of a composite melanin and recombinant spider silk protein lyocell fiber, and the amount of recombinant spider silk protein added is 1, 5, 10 and 20 wt%. The other preparation processes and testing methods are exactly the same as those in Example 4.

[0109] Table 2 Mechanical data of Example 4 and Comparative Example 5

[0110] The mechanical property test results of Examples 4 and Comparative Examples 4 and 5 are shown in Table 2 and Figures 2 and 3. Compared with the composite fibers of melanin or spider silk protein alone, the lyocell fibers with dual composites of melanin and recombinant spider silk protein have a very significant improvement in strength. Among them, the 10% melanin + 10% spider silk protein composite fiber has a strength increase of 95.17% compared with the control fiber. This is because there is a binding force between melanin, cellulose, and spider silk protein, and the three-phase structure formed by the combination of the three provides the fiber with superior mechanical properties.

[0111] Example 5: Preparation of Lyocell fibers with different contents of recombinant spider silk protein and wool melanin

[0112] This embodiment relates to a process for preparing lyocell fibers with wool melanin and different contents of recombinant spider silk protein, which specifically includes the following steps:

[0113] (1) Extraction of melanin: Melanin was extracted from black wool. 5g of black wool was placed in 30mL of concentrated hydrochloric acid and reacted at 48-50℃ for 30min. Then, the melanin precipitate was collected by centrifugation at 10000rpm for 2min. The precipitate was soaked in sulfuric acid solution with pH=3 for 2h. The supernatant was removed by centrifugation at 10000rpm for 2min. The melanin precipitate was freeze-dried to obtain the melanin raw material used for testing.

[0114] (2) Dispersion of melanin: The preparation steps of the melanin dispersion are the same as in Example 3.

[0115] (3) Preparation of spinning solution: The preparation steps of spinning solution are the same as in Example 3, except that the content of added melanin solid is controlled to be 10 wt% of the mass fraction of cellulose raw material, and 1, 2, 5 and 10 wt% of recombinant spider silk protein of cellulose raw material are added at the same time.

[0116] (4) Preparation of Lyocell fiber with composite melanin and recombinant spider silk protein: The spinning steps are the same as in Example 3, except that the spinning solution is a melanin / recombinant spider silk protein spinning solution of different concentrations.

[0117] The obtained composite melanin and recombinant spider silk protein lyocell fibers were subjected to mechanical property tests, and their dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0118] Comparative Example 6

[0119] The only difference between Comparative Example 6 and Example 5 is that no spider silk protein is added during the preparation process of melanin-composite recombinant spider silk protein lyocell fibers. Only 10 wt% of melanin is added from the cellulose raw material. The other preparation processes and testing methods are exactly the same as in Example 5.

[0120] Table 3 Mechanical data for Example 5 and Comparative Example 6

[0121] The mechanical data for Example 5 and Comparative Example 6 are shown in Table 3 and Figure 4. Compared with pure melanin fibers, the melanin fibers with different amounts of spider silk protein showed varying degrees of improvement in both strength and elongation. Among them, the improvement in strength was more significant, with the strength increasing by 77.13% compared to the comparative example when the amount of spider silk protein added was 2%.

[0122] Example 6: Preparation of Lyocell fibers synthesized from melanin and recombinant bee silk protein using a complex enzyme catalysis

[0123] This embodiment relates to a process for preparing lyocell fibers by synthesizing melanin and recombinant bee silk protein using a composite enzyme catalysis, which specifically includes the following steps:

[0124] (1) Enzymatic extraction of melanin: The melanin raw material is derived from enzyme-catalyzed synthesis. Tyrosinase (purchased from Hunan Wokai Biotechnology Co., Ltd.) was used to prepare a 0.01% (w / v) tyrosinase solution with pH 8.0 pure water. Then, 0.01% copper sulfate was added to the enzyme solution and stirred until homogeneous. 1L of tyrosine solution (2.5g / L) was prepared, and 0.1L of tyrosinase solution was added. The reaction was catalyzed by stirring at room temperature for about 24 hours. Then, the pH was adjusted to 2-3 with 30% sulfuric acid. The melanin precipitate was collected by centrifugation at 10,000 rpm for 2 minutes. The melanin precipitate was then freeze-dried to obtain the melanin raw material for testing.

[0125] (2) Dispersion of melanin: The preparation steps of the melanin dispersion are the same as in Example 3.

[0126] (3) Preparation of spinning solution: The preparation steps of spinning solution are the same as in Example 3, except that the content of added melanin solids is controlled to be 1 and 5 wt% of the mass fraction of cellulose raw materials, and recombinant bee silk protein dry powder with the same ratio as the melanin solids content is added, i.e. 1 and 5 wt% of recombinant bee silk protein.

[0127] (4) Preparation of Lyocell fiber with composite melanin and recombinant bee silk protein: The spinning steps are the same as in Example 3, except that the spinning solution is a melanin / recombinant bee silk protein mixed spinning solution.

[0128] The obtained composite melanin and recombinant bee silk protein lyocell fiber were subjected to mechanical property tests, and their dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0129] Comparative Example 7

[0130] The only difference between Comparative Example 7 and Example 6 is that no melanin is added during the preparation process of a composite melanin and bee silk protein lyocell fiber, and the amount of bee silk protein added is 0, 1 and 5 wt%. The other preparation processes and testing methods are exactly the same as those in Example 6.

[0131] Table 4. Mechanical data of Example 6 and Comparative Examples 2 and 7

[0132] The mechanical data for Example 6 and Comparative Example 7 are shown in Table 4 and Figure 5. The sample with 5% bee fibroin added showed a 64.14% increase in strength and a 33.17% increase in elongation compared to Comparative Example 2, indicating an interaction between bee fibroin and cellulose. The sample of Example 6 with 5% melanin and 5% bee fibroin added showed a 166.90% increase in strength and a 26.30% increase in elongation compared to Comparative Example 2. This indicates a binding force between melanin, bee fibroin, and cellulose, further improving the mechanical strength of the fiber.

[0133] Example 7: Preparation of Lyocell fibers composed of composite melanin and recombinant squid beak protein

[0134] This embodiment relates to a process for preparing lyocell fibers containing composite melanin and recombinant squid beak protein, which specifically includes the following steps:

[0135] (1) Dispersion of melanin: The preparation steps of the melanin dispersion are the same as in Example 3.

[0136] (2) Preparation of spinning solution: The preparation steps of spinning solution are the same as in Example 3, except that the content of added melanin solids is controlled to be 0, 1 and 5 wt% of the mass fraction of cellulose raw materials, and recombinant squid beak protein dry powder with the same proportion as the melanin solids content is added, i.e. 0, 1 and 5 wt% of recombinant squid beak protein.

[0137] (3) Preparation of Lyocell fiber with composite melanin and recombinant squid beak protein: The spinning steps are the same as in Example 3, except that the spinning solution is a melanin / recombinant squid beak protein mixed spinning solution.

[0138] The obtained composite melanin and recombinant squid beak protein lyocell fibers were subjected to mechanical property tests, and their dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0139] Comparative Example 8

[0140] The only difference between Comparative Example 6 and Example 6 is that no melanin is added during the preparation process of a composite melanin and squid beak protein lyocell fiber, and the amount of squid beak protein added is 0, 1 and 5 wt%. The other preparation processes and testing methods are exactly the same as those in Example 6.

[0141] Table 5. Mechanical data of Example 7 and Comparative Examples 2 and 8

[0142] The mechanical data for Example 7 and Comparative Example 8 are shown in Table 5 and Figure 6. Comparative Example 8 showed a 35.86% increase in strength compared to the control cellulose fiber, indicating that an interaction force can be generated between the recombinant squid beak protein and cellulose, thereby improving mechanical properties. Example 7 showed a further increase in strength compared to the sample in Comparative Example 8, with the 5% melanin + 5% squid beak protein sample showing a 29.44% increase in strength compared to Comparative Example 8 and a 75.86% increase in strength compared to the control cellulose.

[0143] Example 8: Scale-up process for manufacturing lyocell fibers composed of melanin / recombinant spider silk protein.

[0144] This embodiment relates to an optimized preparation process for lyocell fibers composed of composite melanin / recombinant spider silk protein. Unlike previous embodiments, the preparation process in this embodiment is a factory-scale process, specifically including the following steps:

[0145] (1) Dispersion of melanin: The preparation steps of the melanin dispersion are the same as in Example 3.

[0146] (2) The preparation process of a lyocell fiber spinning solution composed of composite melanin / recombinant spider silk protein is the same as in Example 3. The melanin content is controlled to be 10 wt% of the fiber content, and the spider silk protein content is 1 wt%.

[0147] (3) Preparation of Lyocell fibers composed of composite melanin / recombinant spider silk protein: The spinning solution was added to the spinning system and subjected to high-temperature filtration and degassing. The spinning solution was then pumped to the spinneret for dry-spinning and wet spinning. A spinneret with a diameter of 0.075 mm and 10,000 holes was used. The spinning speed was controlled at 50 m / min, the air gap at 40 mm, and the coagulation bath was an ammonium chloride solution at room temperature with a pH of 3. The high-viscosity spinning solution was vertically drawn into the coagulation bath by air, and after solidification and solvent replacement, nascent fiber bundles were obtained. The fibers were then immersed again in an ammonium chloride solution at room temperature with a pH of 3 for 10 min, followed by repeated washing with hot and cold water to remove residual NMMO and ammonium chloride. Oiling, drying, and cutting were then performed to obtain the final composite melanin / recombinant spider silk protein Lyocell fibers. The obtained composite melanin / recombinant spider silk protein Lyocell fibers are shown in Figure 12.

[0148] The obtained composite melanin / recombinant spider silk protein lyocell fiber was subjected to mechanical property testing, and its dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0149] 60-count Siro-spun compact yarn was used to prepare plain weave woven fabric, and its UV resistance was tested according to national standards. The fibers were also used to prepare spunlace nonwoven fabric with a basis weight of 50 g / m². 2 The fabric's UV protection effect was tested according to GB / T 18830-2009; the fabric's free radical scavenging function was tested according to T / CCTA20102-2023 "Determination and Evaluation of Antioxidant Capacity of Textiles - DPPH and ABTS Methods"; and the fabric's wash fastness was tested according to GB / T 3921-2008 "Tests for Color Fastness of Textiles".

[0150] Comparative Example 9

[0151] The only difference between Comparative Example 9 and Example 8 is that no melanin or spider silk protein is added during the optimization of the preparation process of a composite melanin / recombinant spider silk protein lyocell fiber. The other preparation processes and testing methods are exactly the same as those in Example 8.

[0152] Table 6. Mechanical data of Example 8 and Comparative Example 9

[0153] Table 7. UV resistance data for woven and nonwoven fabrics.

[0154] Table 8. Color fastness data for woven fabrics to soap washing.

[0155] The mechanical properties of Example 8 and Comparative Example 9 are shown in Table 6. The strength of Example 8, which added 10% melanin and 10% spider silk protein, was increased by 23.66% compared with Comparative Example 9, indicating that there is a binding force between melanin, recombinant spider silk protein and cellulose, which gives the fiber a significant mechanical strengthening effect.

[0156] As shown in Figure 10A, the ABTS solutions in the fiber with 10% melanin and the control fiber with 0% melanin showed significantly different colors. The ABTS solution in the sample with added melanin was close to the color of distilled water, indicating that the fiber containing melanin has the ability to scavenge free radicals. The free radical scavenging efficiency was tested according to the ABTS method in the T / CCTA20102-2023 standard. As shown in Figure 10B, the free radical scavenging rate of the sample with 10% melanin was 99.67%, while the free radical scavenging rate of the control fiber was only 12.7%, representing an increase of 684.80%. This meets the standard's Level III antioxidant capacity (free radical scavenging rate ≥80%, indicating extremely strong antioxidant capacity).

[0157] The UV resistance properties of woven and nonwoven fabrics are shown in Table 7. According to the test methods in GB / T 18830-2009, the UV resistance performance of woven fabrics was evaluated. The average UPF of woven fabrics was ≥2000, and the average T(UVA) was 0.05%, indicating extremely strong UV resistance. The UPF of the nonwoven fabric sample was 170, and the average T(UVA) was 0.61%, also indicating UV resistance. The colorfastness to washing of woven fabrics is shown in Table 8. According to the test methods in GB / T 3921, the colorfastness to washing of woven fabrics reached grade 4, and the staining fastness to different media reached grades 4-5, indicating excellent colorfastness.

[0158] Example 9: Preparation of a viscose fiber composed of composite melanin / recombinant spider silk protein

[0159] The preparation process of viscose fiber composed of composite melanin / recombinant spider silk protein in this embodiment includes the following steps:

[0160] (1) Preparation of spider silk protein dispersion: Prepare 20mM Tris-hcl solution, adjust the pH of the dispersant to about 7, add recombinant spider silk protein and stir to dissolve until the solution is clear and transparent, and then degas and filter to obtain recombinant spider silk protein dispersion.

[0161] (2) Dispersion of melanin: The preparation steps of the melanin dispersion are the same as in Example 3.

[0162] (3) Preparation of viscose spinning solution of composite melanin / recombinant spider silk protein: Wood pulp raw material with an average degree of polymerization of 700 was impregnated in sodium hydroxide solution with a mass fraction of 18% at 50℃ for 60 min. The alkaline solution dissolved the low degree of polymerization hemicellulose, and the insoluble material obtained was α-cellulose. The obtained α-cellulose was pressed and crushed, and then aged at 25℃ for 2.5 h. Carbon disulfide with a mass fraction of 35% of the total α-cellulose was added for xanthation at 15℃ for 65 min to obtain cellulose sulfonate. The cellulose sulfonate was dissolved in 6% sodium hydroxide solution and then subjected to dissolution, filtration, degassing and aging to obtain cellulose spinning solution.

[0163] (4) Preparation of high-strength composite spider silk protein regenerated fiber: melanin dispersion, spider silk protein dispersion and cellulose spinning solution are blended together, and the proportions of melanin and spider silk protein in the fiber are controlled to be 10wt% and 1wt% respectively. After uniform mixing, the mixture is filtered and degassed to obtain a blended spinning solution. The blended spinning solution is fed into a coagulation bath through a spinneret to obtain a primary fiber bundle. The coagulation bath consists of 80g / L sulfuric acid, 90g / L zinc sulfate and 170g / L sodium sulfate. The reaction temperature is 50℃, the spinning rate is 50m / min and the immersion time is 2s. The obtained primary fiber bundle is stretched to obtain a shaped fiber bundle. The shaped fiber bundle is post-treated to obtain viscose fiber with composite melanin / recombined spider silk protein.

[0164] Mechanical tests were conducted on the viscose fibers obtained from the composite melanin / recombinant spider silk protein. The dry breaking strength, dry breaking elongation and other properties were tested in accordance with GB / T14337-2022.

[0165] Comparative Example 10

[0166] The only difference between Comparative Example 10 and Example 9 is that no melanin molecules or recombinant spider silk protein are added during the preparation process of a composite melanin / recombinant spider silk protein viscose fiber. The other preparation processes and testing methods are exactly the same as those in Example 9.

[0167] Table 9 Mechanical data of Example 9 and Comparative Example 10

[0168] The mechanical property data of Example 9 and Comparative Example 10 are shown in Table 9. The sample of Example 9 with added melanin and spider silk protein showed different degrees of increase in strength compared with Comparative Example 10. Among them, when the amount of melanin added was 10% and the amount of spider silk protein added was 2%, the fiber strength reached 3.03 cN / dtex, which was 48.53% higher than that of Comparative Example 10. This indicates that the three-phase structure system of melanin, cellulose and spider silk protein has been formed, which greatly improves its strength.

[0169] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A regenerated cellulose fiber containing melanin, characterized in that, The regenerated cellulose fibers contain uniformly dispersed melanin.

2. The regenerated cellulose fiber containing melanin according to claim 1, characterized in that, The melanin is obtained by at least one of the following methods: melanin extracted from cuttlefish ink, melanin extracted from mammalian hair, melanin extracted by microbial fermentation, and melanin obtained by tyrosinase-catalyzed reaction.

3. The melanin-containing regenerated cellulose fiber according to claim 1, characterized in that, In the melanin-containing regenerated cellulose fiber, the mass ratio of melanin to cellulose is 0.005-0.2:1; Preferably, in the melanin-containing regenerated cellulose fiber, the mass ratio of melanin to cellulose is 0.01-0.2:

1.

4. The regenerated cellulose fiber containing melanin according to claim 1, characterized in that, The regenerated cellulose fibers also contain uniformly dispersed proteins; the proteins contain carbohydrate-binding domains.

5. The melanin-containing regenerated cellulose fiber according to claim 1, characterized in that, The protein contains a natural animal protein amino acid sequence; the N-terminus and C-terminus of the natural animal protein amino acid sequence are respectively connected to carbohydrate-binding domains; Preferably, the amino acid sequence of the natural animal protein includes at least one of the following: spider silk protein amino acid sequence, squid beak protein amino acid sequence, and bee silk protein amino acid sequence; Preferably, the amino acid sequence of the protein containing the squid beak protein amino acid sequence is shown in SEQ ID NO.1, the amino acid sequence of the protein containing the spider silk protein amino acid sequence is shown in SEQ ID NO.3, and the amino acid sequence of the protein containing the bee silk protein amino acid sequence is shown in SEQ ID NO.

5.

6. The melanin-containing regenerated cellulose fiber according to claim 1, characterized in that, In the melanin-containing regenerated cellulose fiber, the mass ratio of protein to cellulose is 0.001-1:1; Preferably, in the melanin-containing regenerated cellulose fiber, the mass ratio of protein to cellulose is 0.01-0.2:

1.

7. The method for preparing regenerated cellulose fibers containing melanin according to any one of claims 1-6, characterized in that, include: Step 1) Add melanin to an alkaline solution and mix thoroughly to obtain a melanin dispersion; Step 2) Mix the spinning solution raw materials containing cellulose, solvent and melanin dispersion evenly to obtain a spinning solution; Step 3) Spinning is performed using the aforementioned spinning solution. During the spinning process, an acidic solution is used in a coagulation bath to coagulate the fibers, thereby obtaining the regenerated cellulose fibers containing melanin.

8. The preparation method according to claim 7, characterized in that, In step one), melanin is first dissolved in a NaOH solution with a pH of 10-12 to remove impurities, and then dried to obtain melanin powder; then the melanin is added to an alkaline solution and mixed evenly to obtain a melanin dispersion.

9. The preparation method according to claim 7, characterized in that, In step two), the solvent for the spinning solution is at least one of NMMO solution, alkaline solution of carbon disulfide, or ionic liquid. Preferably, the pH of the spinning solution is greater than 10; Preferably, the ionic liquid is at least one of lithium chloride / DMAc and imidazole chloride. In step two), the spinning solution raw material containing cellulose, solvent and melanin dispersion is stirred and dissolved at 90-110℃ and 85-98KPa for 2-3 hours. In step two), the spinning solution is stirred and dispersed for 10-15 hours.

10. The preparation method according to claim 7, characterized in that, In step three), the pH of the acidic solution used is 2-3; the acidic solution is at least one of inorganic acid solution, organic acid solution, and strong acid-weak base salt solution. Preferably, the acidic solution is at least one selected from sulfuric acid solution, hydrochloric acid solution, formic acid solution, and acetic acid solution; More preferably, the acidic solution is a sulfuric acid solution.

11. The preparation method according to claim 7, characterized in that, The spinning solution raw material also contains protein; the protein contains carbohydrate-binding domains; Preferably, the protein comprises a natural animal protein amino acid sequence; the N-terminus and C-terminus of the natural animal protein amino acid sequence are respectively connected to carbohydrate-binding domains.

12. The preparation method according to claim 7, characterized in that, The protein was synthesized by microorganisms; Preferably, the protein is synthesized using the following method: The nucleic acid sequence encoding the protein is transferred into a microorganism, which is then cultured to synthesize the protein, resulting in a bacterial culture medium. The bacterial culture medium is then subjected to sonication and centrifugation, and the supernatant is used for protein purification using a nickel column to obtain the protein. Preferably, the nucleic acid sequence encoding the protein is any one of SEQ ID NO.2, SEQ ID NO.4, and SEQ ID NO.

6.

13. The preparation method according to claim 7, characterized in that, The spinning process adopts dry-jet wet spinning; the spinning needle orifice diameter in the dry-jet wet spinning is 0.075-0.3mm, the spinning speed is controlled at 10-50m / min, and the air gap is 10-40mm.

14. The use of the melanin-containing regenerated cellulose fiber according to any one of claims 1-6 or the melanin-containing regenerated cellulose fiber prepared by the preparation method according to any one of claims 7-13 in textile materials.

15. A textile material with anti-ultraviolet and anti-radiation effects, characterized in that, The regenerated cellulose fiber containing melanin, as described in any one of claims 1-6, or the regenerated cellulose fiber containing melanin prepared by the preparation method described in any one of claims 7-13.

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