Method for preparing regenerated cellulose fibers

Abstract

A method of making regenerated bacterial cellulose fibers, the method comprising: contacting a bacterial cellulose powder with an aqueous solution comprising a quaternary ammonium hydroxide and optionally urea under conditions that cause at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; or contacting the bacterial cellulose powder with an aqueous solution comprising a metal complex under conditions that cause at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; and extruding the cellulose slurry in a coagulating bath, thereby forming regenerated bacterial cellulose fibers.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 485,028, filed on February 15, 2023, the entire contents of which are hereby incorporated by reference. Technical Field

[0003] The present disclosure generally relates to methods of preparing regenerated cellulose fibers from bacterial cellulose powder produced during a kombucha fermentation process. Background Art

[0004] For thousands of years, cellulose-based materials obtained from wood, cotton and bamboo have been widely used as materials for paper, construction, energy, textiles and furniture. Cotton fibers and wood-based regenerated cellulose fibers are the most common types of cellulose fibers in the textile industry. However, cellulose fibers also have some disadvantages.

[0005] Cotton is a natural plant fiber that grows around the seeds of the cotton plant. Cotton fiber is obtained from the cotton plant and then spun into yarn. The cotton yarn is then braided or woven into fabric. According to the World Wildlife Fund, the most prominent impacts of cotton on the environment come from the use of pesticides, high water consumption and high land space requirements.

[0006] Regenerated cellulose fibers can be made from cellulose extracted from wood pulp, which is then chemically dissolved and extruded into continuous filaments.

[0007] Conventional processes for making regenerated cellulose fibers often involve toxic chemicals and / or by-products.

[0008] For example, Figure 1 As shown, the Kraft process, which is commonly used to prepare regenerated cellulose fibers, can cause severe pollution because H2S is used to break the bonds between lignin, hemicellulose and cellulose.

[0009] like Figure 2 As shown, in another example, rayon is produced by reacting cellulose with sodium hydroxide to form alkali cellulose, which in turn reacts with highly toxic carbon disulfide to form xanthate cellulose, which is then dissolved in dilute sodium hydroxide and extruded into regenerated cellulose fibers.

[0010] Therefore, there is a need for new methods of preparing regenerated cellulose fibers that avoid the use of polluting chemicals used in traditional processes.

[0011] Kombucha is a fermented tea that has grown in popularity in recent years, in part because people believe that drinking it will eliminate toxins, increase energy, strengthen the immune system and aid in weight loss. The global kombucha market size was valued at $2.64 billion in 2021 and is expected to expand at a compound annual growth rate of 15.6% from 2022 to 2030.

[0012] like Figure 3 As shown in Figure 1, SCOBY biofilm is a gel-like biofilm containing bacterial cellulose that is formed during the kombucha tea making process. Kombucha bacterial cellulose does not contain other biopolymers such as lignin, hemicellulose and pectin. Its high purity, high degree of polymerization (DP) and high crystallinity make SCOBY biofilm an attractive alternative source for cellulose fiber production.

[0013] There remains a need for improved methods of producing and isolating bacterial cellulose fibers from kombucha SCOBY biofilms. SUMMARY OF THE INVENTION

[0015] In the present disclosure, bacterial cellulose, using SCOBY biofilm produced as a side stream of kombucha fermentation, is developed as a sustainable source for the production of regenerated cellulose fibers. The methods described herein address several challenges, such as Figure 5 As shown, (1) a solvent system that effectively dissolves bacterial cellulose is developed; and (2) the conditions for wet spinning of regenerated bacterial cellulose fibers are optimized. Bacterial cellulose with high purity, high degree of polymerization and high crystallinity can be used as an alternative source for cellulose fiber production. The advantages of the methods described herein include, but are not limited to, the rapid growth rate of SCOBY biofilms and the bacterial cellulose fibers included therein, the absence of pesticides and toxic chemicals, and low water requirements.

[0016] In a first aspect, the present invention provides a method for preparing regenerated bacterial cellulose fibers, the method comprising: contacting bacterial cellulose powder with an aqueous solution comprising quaternary ammonium hydroxide and optionally urea under conditions causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; or contacting bacterial cellulose powder with an aqueous solution comprising a metal complex under conditions causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; and extruding the cellulose slurry in a coagulation bath, thereby forming regenerated bacterial cellulose fibers.

[0017] In certain embodiments, the bacterial cellulose powder is kombucha bacterial cellulose powder.

[0018] In certain embodiments, the quaternary ammonium hydroxide is NR4OH, wherein R for each instance is independently alkyl, cycloalkyl, or phenyl; and the metal complex comprises a metal selected from the group consisting of aluminum, calcium, copper, iron, nickel, and zinc.

[0019] In certain embodiments, the quaternary ammonium hydroxide is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide; and the metal complex is bis(ethylenediamine)copper(II) hydroxide.

[0020] In certain embodiments, the quaternary ammonium hydroxide is present in the aqueous solution at a concentration of 20-60% w / w; and the metal complex is present in the aqueous solution at a concentration of 0.5-2M.

[0021] In certain embodiments, urea is present in the aqueous solution at a concentration of 0.1-0.5% w / w.

[0022] In certain embodiments, the coagulation bath includes a primary drawing bath and also includes a secondary drawing bath.

[0023] In certain embodiments, the pH of the primary drawing bath and the secondary drawing bath are each independently in the range of 0-1.

[0024] In certain embodiments, the primary drawing bath and the secondary drawing bath each comprise an aqueous H2SO4 solution, and optionally an aqueous Na2SO4 solution.

[0025] In certain embodiments, the concentration of H2SO4 in each of the primary drawing bath and the secondary drawing bath is independently 0.25M to 1M.

[0026] In certain embodiments, the cellulose slurry comprises bacterial cellulose at a concentration of 2-10% w / w.

[0027] In certain embodiments, the method further comprises: providing a symbiotic colony of bacteria and yeast (SCOBY) biofilm; contacting the SCOBY biofilm with an alkaline aqueous solution to form a treated SCOBY biofilm; optionally washing and drying the treated SCOBY biofilm; and powdering the treated SCOBY biofilm to form bacterial cellulose powder.

[0028] In certain embodiments, the method further comprises: washing the regenerated bacterial cellulose fibers with water, and drying the washed regenerated bacterial cellulose fibers.

[0029] In certain embodiments, the conditions that cause at least a portion of the bacterial cellulose powder to dissolve include: maintaining an aqueous solution comprising quaternary ammonium hydroxide and optionally urea at 25-50°C for 8-24 hours; or maintaining an aqueous solution comprising a metal complex at 75-90°C for 1-2 hours.

[0030] In certain embodiments, the method comprises: contacting bacterial cellulose powder with an aqueous solution comprising 20-60% w / w N(C1-C5)4OH and optionally 0.1-0.5% w / w urea at 25-40°C for 8-24 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose at a concentration of 4-10% w / w; or contacting bacterial cellulose powder with an aqueous solution comprising 0.5M to 2M bis(ethylenediamine)copper(II) hydroxide at 75-90°C for 1-2 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose at a concentration of 2-6% w / w; and extruding the cellulose slurry in a coagulation bath comprising a primary drawing bath and a secondary drawing bath, wherein the pH of the primary drawing bath and the secondary drawing bath are independently 0-0.5, thereby forming regenerated bacterial cellulose fibers.

[0031] In certain embodiments, the cellulose slurry comprises bacterial cellulose at a concentration of 3.5-5.5% w / w.

[0032] In certain embodiments, the method further comprises: providing a symbiotic colony of bacteria and yeast (SCOBY) biofilm; contacting the SCOBY biofilm with an alkaline aqueous solution to form a treated SCOBY biofilm; optionally washing and drying the treated SCOBY biofilm; and powdering the treated SCOBY biofilm to form bacterial cellulose powder.

[0033] In certain embodiments, the pH of the alkaline aqueous solution is 13-14.

[0034] In certain embodiments, the basic aqueous solution comprises NaOH.

[0035] In certain embodiments, the method comprises: providing a symbiotic colony of bacteria and yeast (SCOBY) biofilm; contacting the SCOBY biofilm with an alkaline aqueous solution having a pH of 13-13.5 to form a treated SCOBY biofilm; optionally washing and drying the treated SCOBY biofilm; powdering the treated SCOBY biofilm to form a bacterial cellulose powder; mixing the bacterial cellulose powder with a 20-60% w / w N (C1-C5) 4 OH and optionally 0.1-0.5% w / w urea in water at 25-40 ° C for 8-24 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry containing a concentration of 3.5-5.5% w / w bacterial cellulose; or the bacterial cellulose powder is contacted with an aqueous solution containing 0.5M to 2M bis (ethylenediamine) copper (II) hydroxide at 75-90 ° C for 1-2 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry containing a concentration of 3.5-5.5% w / w bacterial cellulose; and the cellulose slurry is extruded in a coagulation bath comprising a primary drawing bath and a secondary drawing bath, wherein the primary drawing bath and the secondary drawing bath each contain an aqueous solution of H2SO4 and Na2SO4 at a pH of 0-0.5, thereby forming regenerated bacterial cellulose fibers.

[0036] The methods disclosed herein may include one of three different bacterial cellulose powder dissolution methods:

[0037] 1.Quaternary ammonium hydroxide (QAH) water solvent system

[0038] QAH solutions including tetramethylammonium hydroxide (TMAH, 25% aqueous solution), tetraethylammonium hydroxide (TEAH, 30% aqueous solution), tetrapropylammonium hydroxide (TPAH, 35% aqueous solution), and tetrabutylammonium hydroxide (TBAH, 55% aqueous solution) can be used as a solvent system for dissolving bacterial cellulose powder.

[0039] Without wishing to be bound by theory, it is believed that anions and cations play a crucial role in the dissolution of bacterial cellulose powder. Anions can participate in interactions with hydroxyl protons on cellulose, while the hydrophobic substituents present on QAH can interact with the hydrophobic part of cellulose via van der Waals forces to form QA +-cellulose intermediates, thereby promoting the dissolution of bacterial cellulose powder. These actions can lead to the destruction of intermolecular and intramolecular hydrogen bonds, thereby effectively dissolving bacterial cellulose powder.

[0040] 2.QAH / urea water solvent system

[0041] Without wishing to be bound by theory, it is believed that urea can increase the solubility and stability of cellulose in solution by aggregating near hydrophobic regions via van der Waals forces. Adding urea to the aqueous QAH solution can not only reduce the amount of QAH solution required, but also promote dissolution at ambient temperature.

[0042] 3. Metal complex based solvent system

[0043] The advantage of using metal complexes as solvent systems is that they can form stronger metal coordination bonds with the substituents present on cellulose. Decomplexation of the metal complex can release cellulose. Unlike hydrogen-bonding solvents, the proposed metal complex solvent system can effectively improve the solubility of bacterial cellulose powder.

[0044] The Box-Behnken design was used to optimize the culture medium concentration, culture environment temperature and culture medium.

[0045] The purpose of the present disclosure is to provide a method for preparing regenerated cellulose fiber from bacterial cellulose. The cellulose bacterial film formed by fermentation is purified under alkaline treatment conditions, and then a washing and drying process is performed. After grinding the dried bacterial cellulose, the bacterial cellulose powder can be used to prepare a spinning slurry, and the spinning slurry can then be used to spin fibers.

[0046] In the present disclosure, the preparation of slurry by directly dissolving bacterial cellulose powder in three dissolution systems was studied. In certain embodiments, the bacterial cellulose powder dissolution method includes: 1) tetrabutylammonium hydroxide solution (TBAH, 40%-55% aqueous solution); 2) tetrabutylammonium hydroxide (TBAH) / urea water solvent system; 3) metal complex-based solvent system. Advantageously, these solvent systems can eliminate excessive spinning temperatures and eliminate the use of polluting chemicals and synthetic polymers in solvents and raw materials. The characteristics of cellulose slurries at different dissolution concentrations were analyzed. In addition, wet spinning of different slurries was demonstrated and the fibers were characterized.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and other objects and features of the present disclosure will become apparent from the following description of the present disclosure in conjunction with the accompanying drawings.

[0049] Figure 1 The kraft pulping process is depicted.

[0050] Figure 2 Depicting the production of rayon.

[0051] Figure 3 Photographs showing exemplary SCOBY biofilms are depicted.

[0052] Figure 4 Graphs showing the solubility and time required for complete dissolution of bacterial cellulose in common solvents such as N-methylmorpholine N-oxide (NMMO), ionic liquid zinc chloride trihydrate, 1-ethyl-3-methylimidazolium acetate (EMIMAc), and N,N-dimethylacetamide / lithium chloride (LiCl / DMAc) are depicted.

[0053] Figure 5 Depicted is a flow chart showing an exemplary process for preparing regenerated bacterial cellulose fibers according to certain embodiments described herein.

[0054] Figure 6 A theoretical reaction sequence showing the use of metal complex complexation to drive dissolution of bacterial cellulose and decomplexation of the metal complex to regenerate cellulose is depicted.

[0055] Figure 7 A picture showing the product of Example 3 after cutting and grinding is depicted. DETAILED DESCRIPTION OF THE INVENTION

[0057] definition

[0058] Throughout this disclosure, unless the context requires otherwise, the words "comprise" or "comprises" or "comprising" and other variations should be understood to mean the inclusion of the stated integer or groups of integers but not the exclusion of any other integer or groups of integers. It should also be noted that in this disclosure, especially in the claims and / or paragraphs, terms such as "comprises", "comprised", "comprising", etc. may have the meanings ascribed to them in U.S. patent law, for example, they may mean "includes", "included", "including", etc.; while terms such as "consisting essentially of" and "consists essentially of" have the meanings ascribed to them in U.S. patent law, for example, they take into account elements not expressly recited, but do not include elements found in the prior art or elements that affect the basic or novel characteristics of the invention.

[0059] Furthermore, in the present disclosure and claims, unless the context requires otherwise, the word "include" or "includes" or "including" and variations such as "including" will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0060] Unless specifically stated otherwise, as used herein, the singular includes the plural (and vice versa). In addition, unless specifically stated otherwise, when the term "about" is used before a quantitative value, the present teachings also include the specific quantitative value itself.

[0061] Unless otherwise stated or inferred, as used herein, the term "about" refers to a variation of ±10%, ±7%, ±5%, ±3%, ±1%, or ±0% from the nominal value.

[0062] The present disclosure provides methods for preparing cellulose pulp, methods for preparing regenerated cellulose fibers from cellulose pulp, and products thereof. The regenerated cellulose fibers may optionally contain functional materials that affect the physical, chemical, mechanical and / or optical properties of the regenerated cellulose fibers.

[0063] In a first aspect, the present invention provides a method for preparing regenerated bacterial cellulose fibers, the method comprising: contacting bacterial cellulose powder with an aqueous solution comprising quaternary ammonium hydroxide and optionally urea under conditions causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; or contacting bacterial cellulose powder with an aqueous solution comprising a metal complex under conditions causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; and extruding the cellulose slurry in a coagulation bath, thereby forming regenerated bacterial cellulose fibers.

[0064] Regenerated bacterial cellulose fibers prepared according to the methods described herein can be used in a variety of potential applications including, but not limited to, paper and packaging, biomedicine and pharmaceuticals, food and cosmetics, biosensors and energy storage, and / or textiles and materials.

[0065] In certain embodiments, the bacterial cellulose powder is a kombucha bacterial cellulose powder from a SCOBY biofilm produced during the fermentation of a kombucha culture.

[0066] The kombucha culture may include a carbon source and a nitrogen source.

[0067] The carbon source is not particularly limited as long as it can support the growth of the SCOBY. In certain embodiments, the carbon source is selected from the group consisting of ethanol, glucose, sucrose, fructose, galactose, inositol, glycerol, xylose, dextrose, lactose, dextrin, ribitol, mannitol, mannose, maltose, raffinose, coconut palm sugar, sugar cane, raw sugar, honey, malt extract, molasses, etc.

[0068] In certain embodiments, the nitrogen source comprises at least one organic nitrogen source selected from the group consisting of yeast extract, peptone, soy, casamino acids, trypsin and malt extract, NH4Cl, NH4NO3, NaNO3, (NH4)2SO4, tea (e.g., green tea or black tea), coffee, red wine, white wine, malt, beer, juice, fruit, peel, vegetable, coconut milk or other nitrogen-containing organic matter.

[0069] In certain embodiments, the kombucha culture comprises tea and sucrose.

[0070] The SCOBY may comprise one or more bacteria and one or more yeasts. In certain embodiments, the SCOBY comprises acetic acid bacteria, lactic acid bacteria, and osmophilic yeast.

[0071] The bacteria are not particularly limited as long as they can produce bacterial cellulose. In certain embodiments, one or more bacteria are selected from the group consisting of Gluconobacter, Komagataeibacter, Pseudomonas, Agrobacterium, Rhizobium, Lactobacillus, Acetobacter, Azotobacter, Gluconacetobacter, Aerobacter, Sarcina, and Alcaligenes. Specific examples of bacteria that can be used in the methods described herein include, but are not limited to, Komagataeibacter xylinus, Komagataeibacter intermedius, Komagataeibacter rhaeticus, Komagataeibactersaccharivorans, Komagataeibacter kombuchae, Acetobacter pasteurianus, Acetobacter aceti, Acetobacter xylinum, Acetobacter ransens, and Enterobacter sp.

[0072] The one or more yeasts may be selected from the group consisting of Zygosaccharomyces, Candida, Torulaspora, Pichia, Koleckera, Brettanomyces, Schizosaccharomyces, Saccharomyces, Saccharomycodes, and Cyberlindnera jadini. Specific examples of yeast that can be used in the methods described herein include, but are not limited to, Candida stellata, Saccharomycodes ludwigii, Saccharomycodes apiculatus, Schizosaccharomyces pombe, Brettanomyces bruxellensis, Zygosaccharomyces bailii, and Saccharomyces cerevisiae.

[0073] Bacterial cellulose powder can be prepared from SCOBY biofilms, which are typically formed on the surface of the culture medium during the fermentation process. The SCOBY biofilm can be optionally purified before dissolution, wherein the purification includes liquid-solid extraction with an alkaline aqueous solution to remove any unwanted contaminants. In certain exemplary embodiments, the alkaline solution is prepared by dissolving a metal hydroxide such as LiOH, NaOH, KOH, Ca(OH)2, or the like in water. In an exemplary embodiment, about 6-12 g of sodium hydroxide is dissolved in 1 L of water. The SCOBY biofilm can be completely immersed in the alkaline aqueous solution and then heated, for example, at 70-90°C for 0.5-1 hour to assist in purification. Contaminants can diffuse out of the SCOBY biofilm, thereby obtaining a purified SCOBY biofilm. The alkaline aqueous solution is then exchanged with water and heated, for example, at 60-80°C for 0.5-1 hour to wash the SCOBY biofilm. The washing process can then be optionally repeated 2, 3, 4 or more times until the pH of the wash water becomes 6-8.

[0074] The SCOBY biofilm may optionally be dried, e.g., by vacuum oven, by heating, e.g., at 40-70° C. for 0.5-1 hour, or freeze drying, e.g., for 24-48 hours. The SCOBY biofilm may then be chopped or crushed into smaller particles, e.g., <1.0 mm in diameter, and finally ground into a fine powder, e.g., <0.2 mm in diameter. In certain embodiments, the drying process may be skipped, and the bacterial cellulose may be dissolved in a wet state.

[0075] The solubility of cellulose powder in common solvents is extremely low. However, by properly selecting the solvent system and dissolution conditions, the dissolution rate and solubility of cellulose powder in the solvent system can be increased. Figure 4 Four common solvent systems for dissolving cellulose powder are shown. Although some solvent systems can achieve high solubility and good dissolution rates, they require the use of organic solvents or ionic liquid solvents, which are too expensive to use on a large scale and may pose potential health and environmental risks. In addition, some solvent systems require high temperatures, resulting in extremely slow dissolution rates (up to 70 hours to dissolve), which poses an obstacle to widespread application.

[0076] The cellulose powder dissolution system described herein utilizes readily available reagents and is capable of rapidly dissolving bacterial cellulose powder to produce a cellulose slurry containing cellulose at a concentration of up to 10% w / w.

[0077] The quaternary ammonium hydroxide can have the chemical structure NR4OH, wherein R is independently alkyl, cycloalkyl or phenyl for each instance; or two instances of R together with the nitrogen to which they are attached form a 3-6 membered heterocycloalkyl. In certain embodiments, each R is independently C1-C4 alkyl. Specific examples of quaternary ammonium hydroxides that can be used in the methods described herein include, but are not limited to, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0078] In certain embodiments, the metal complex comprises: a metal selected from the group consisting of aluminum, calcium, copper, iron, nickel, manganese, indium, tungsten and zinc; at least one anion selected from the group consisting of bromide, chloride, sulfate, bisulfate, carbonate, bicarbonate, nitrate, acetate, valerate, oleate, palmitate, stearate, laurate, benzoate, lactate, phosphate, benzoate, citrate, maleate, fumarate, succinate, tartrate, naphthoate (napthylat), methanesulfonate, glucoheptonate, lactobionate, dodecylsulfonate, etc.; and optional ligands. The metal may exist in +1, +2, +3 or +4 oxidation states.

[0079] The type of ligand used is not particularly limited, as long as it can coordinate with at least a portion of the selected metal. In certain embodiments, the ligand is a monodentate ligand, a bidentate ligand, a tridentate ligand or a tetradentate ligand. Exemplary ligands include, but are not limited to, bipyridine, o-phenanthroline, 2-phenylpyridine bipyrimidine, bipyrazole glycinate (bipyrazyl, glycinate), acetylacetone, 2,6-bis (1-methylbenzimidazol-2-yl) pyridine, ethylenediamine, cyclohexanediamine, 1,3-propylenediamine, 1,3-diamino-2-hydroxypropane, 1,6-hexanediamine, acetylacetone (acac), ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, propylenediaminetetraacetic acid, amino acids, etc.

[0080] Metal complexes must be charge balanced. The ratio of metal to at least one anion can be expressed using the formula (A t+ ) U (B u- ) T It is represented by, where A represents the metal, B represents at least one anion, t represents the charge of the metal, u represents the charge of at least one anion, U is equal to the absolute value of the charge of at least one anion, and T is equal to the absolute value of the charge of the metal. For example, when the charge of the metal is 1+ and the anion is SO4 2- (its charge is -2), the charge balance formula is (A 1+ )2(SO4 2- ).

[0081] In certain embodiments, the metal complex is bis(ethylenediamine)copper(II) hydroxide.

[0082] The cellulose powder and the aqueous solution may be contacted at the following mass ratios, respectively: 1-10:90-99, 1-9:91-99, 1-8:92-99, 1-7:93-99, 1-6:94-99, 2-6:90-98, 3-6:90-97, 3-5:95-97 or 3.5-4.5:95.5-96.5.

[0083] The cellulose slurry may comprise bacterial cellulose at a concentration of 1-10% w / w, 2-10% w / w, 3-10% w / w, 4-10% w / w, 5-10% w / w, 6-10% w / w, 7-10% w / w, 1-9% w / w, 1-8% w / w, 1-7% w / w, 1-6% w / w, 2-6% w / w, 3-6% w / w, 3-5% w / w, or 3.5-4.5% w / w. In certain embodiments, the cellulose slurry comprises bacterial cellulose at a concentration of about 4% w / w.

[0084] The quaternary ammonium hydroxide can be present in the aqueous solution at a concentration of 1-60% w / w, 5-60% w / w, 10-60% w / w, 15-60% w / w, 20-60% w / w, 25-60% w / w, 30-60% w / w, 30-55% w / w, 30-50% w / w, 30-45% w / w, 30-40% w / w, 35-40% w / w, 35-60% w / w, 40-60% w / w, 45-60% w / w, 50-60% w / w, 55-60% w / w, or 40-55% w / w. In certain embodiments, the quaternary ammonium hydroxide is present in the aqueous solution at a concentration of about 40% w / w or about 55% w / w.

[0085] Urea can optionally be present in the aqueous solution at a concentration of 0.1-1% w / w, 0.1-0.9% w / w, 0.1-0.8% w / w, 0.1-0.7% w / w, 0.1-0.6% w / w, 0.1-0.5% w / w, 0.1-0.4% w / w, 0.1-0.3% w / w, or 0.15-0.25% w / w. In certain embodiments, urea is present in the aqueous solution at a concentration of about 0.2% w / w.

[0086] The metal complex may be present in the aqueous solution at a concentration of 0.1-2 M, 0.5-2 M, 0.5-1.5 M, 0.6-1.4 M, 0.7-1.3 M, 0.8-1.2 M, or 0.9-1.1 M. In certain embodiments, the metal complex is present in the aqueous solution at a concentration of about 1M.

[0087] One of ordinary skill in the art can readily determine conditions that result in dissolution of at least a portion of the bacterial cellulose powder. Methods such as stirring, sonication, and / or heating can be used to help dissolve the bacterial cellulose powder.

[0088] In certain embodiments, the conditions that cause at least a portion of the bacterial cellulose powder to dissolve include maintaining an aqueous solution comprising quaternary ammonium hydroxide and optionally urea at 25-60°C, 25-55°C, 30-55°C, 30-50°C, or 35-45°C.

[0089] The aqueous solution comprising quaternary ammonium hydroxide and optional urea can be maintained at the required temperature or temperature range for dissolving, until substantially all bacterial cellulose powders are dissolved in the aqueous solution, or until the bacterial cellulose powder in the aqueous solution has reached saturation. If the bacterial cellulose in the aqueous solution reaches saturation, a portion of quaternary ammonium hydroxide and / or water can be added extra. In certain embodiments, the aqueous solution comprising quaternary ammonium hydroxide and optional urea is maintained at the required temperature or temperature range for dissolving for 5 minutes to 24 hours, 30 minutes to 24 hours, 1-24 hours, 2-24 hours, 3-24 hours, 4-24 hours, 5-24 hours, 6-24 hours, 7-24 hours, 8-24 hours, 9-24 hours, 10-24 hours, 12-24 hours, 14-24 hours, 16-24 hours, 18-24 hours, 20-24 hours, 22-24 hours, 6-18 hours, 8-16 hours or 10-14 hours. In certain embodiments, the aqueous solution comprising the quaternary ammonium hydroxide and optionally urea is maintained at the temperature or temperature range required for dissolution for about 12 hours.

[0090] In certain embodiments, the conditions that cause at least a portion of the bacterial cellulose powder to dissolve include maintaining the aqueous solution comprising the metal complex at 50-100°C, 60-100°C, 70-100°C, 70-90°C, 75-90°C, or 80-90°C.

[0091] The aqueous solution comprising the metal complex can be maintained at the dissolution temperature or temperature range required for dissolving, until substantially all bacterial cellulose powders are dissolved in the aqueous solution, or until the bacterial cellulose powder in the aqueous solution has reached saturation. If the bacterial cellulose in the aqueous solution reaches saturation, a portion of metal complex and / or water can be added additionally. In certain embodiments, the aqueous solution comprising the metal complex can be maintained at the temperature or temperature range required for dissolving for 5 minutes to 5 hours, 30 minutes to 5 hours, 1 hour to 5 hours, 1 hour to 4 hours, 1 hour to 3 hours or 1 hour to 2 hours. In certain embodiments, the aqueous solution comprising the metal complex can be maintained at the temperature or temperature range required for dissolving for approximately 90 minutes.

[0092] In certain embodiments, dissolution of bacterial cellulose powder can be achieved using the methods described herein, for example in TBAH, 40%-55% aqueous solution or TBAH / urea water solvent system at room temperature to 40°C with gentle stirring for 8-24 hours; or in an aqueous solution containing a metal complex at 75-90°C after 1-2 hours of dissolution time.

[0093] In certain embodiments, when at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, or all of the bacterial cellulose powder in contact with the aqueous solution has dissolved, substantially all of the bacterial cellulose powder has dissolved in the aqueous solution. Any undissolved bacterial cellulose powder may optionally be removed from the aqueous solution using any method such as filtration, centrifugation, and decantation.

[0094] At least one filter may optionally be used to remove any undissolved cellulose powder from the cellulose slurry. In certain embodiments, the cellulose slurry is filtered using one or more filters having a pore size of 5-500 μm. The filtration of the cellulose slurry may be improved by filtering the cellulose slurry sequentially with progressively finer filters. This reduces the likelihood that the filter will become clogged with particles and / or clumps larger than the filter pore size. Thus, in certain embodiments, the cellulose slurry is filtered through 1, 2, 3, 4, 5, 6 or more filters having a pore size of 5-500 μm. The cellulose slurry is filtered through 1, 2, 3, 4, 5, 6 or more filters having a pore size of 5-

[0095] In some embodiments, the cellulose slurry is filtered using filters with pore sizes of 20 μm, 50-100 μm, 100-300 μm and 300-500 μm. In some embodiments, the cellulose slurry is filtered using filters with pore sizes of 500 μm, 300 μm, 100 μm, 50 μm,

[0096] The cellulose slurry is filtered through 20 μm and 5 μm filters, which results in a solution containing particles having at least one dimension smaller than 5 μm.

[0097] The optionally filtered cellulose slurry may then be degassed by a centrifuge. In certain embodiments, the optionally filtered cellulose slurry is centrifuged at 3,000 rpm to 8,000 rpm for 5-30 minutes. Degassing is performed until substantially all of the gas is removed from the optionally filtered cellulose slurry, or until no further gas is discharged.

[0098] The prepared cellulose slurry is loaded into the extruder while the slurry is temperature controlled throughout the spinning process. The extrusion rate of the slurry through the spinneret can be controlled by a gear pump. The spinneret can be configured horizontally and immersed in a coagulation bath. The formation of cellulose fibers is carried out at room temperature in the primary drawing bath (coagulation) and the secondary drawing bath (stretching). 0.25M-1.0M sulfuric acid and sodium sulfate (molar ratio of 1:1 or 1:1.1) are used as coagulants in the primary drawing bath and the secondary drawing bath. The regenerated fibers are then washed with water at 60-80°C in a washing bath. The fibers are collected and dried at 40-70°C for 4-8 hours.

[0099] The structure and properties of the fiber can be adjusted by the residence time of the fiber in the coagulation bath. Therefore, the rotation speed of the gear pump, the take-up speed of the primary drawing bath and the secondary drawing bath can be calculated according to the following equation:

[0100]

[0101] v1=v0×σ1

[0102] v2=v1×σ2

[0103] in:

[0104] ω: Gear pump rotation speed

[0105] n: the number of holes on the spinneret

[0106] r: Radius of the hole on the spinneret

[0107] C: Flow rate per revolution

[0108] v1: The speed of the primary drawing bath

[0109] v2: The speed of the secondary drawing bath

[0110] σ1: Primary drawing ratio

[0111] σ2: Secondary drawing ratio

[0112] The step of extruding the cellulose slurry in a coagulation bath may include passing the cellulose slurry through a spinneret into the coagulation bath. In certain embodiments, the coagulation bath includes wet drawing in a primary drawing bath (coagulation) and an optional secondary drawing bath (drawing).

[0113] The spinneret can be a single-filament spinneret or a multi-filament spinneret.

[0114] The cellulose slurry can pass through the spinneret at a flow rate of 3-12 m / min, 4-11 m / min, 4-10 m / min, 5-10 m / min, 6-10 m / min or 7-9 m / min. In certain embodiments, the cellulose slurry passes through the spinneret at a flow rate of about 8 m / min.

[0115] The primary drawing bath and the secondary drawing bath may each independently contain any solvent in which the cellulose slurry has low solubility. In certain embodiments, the primary drawing bath and the secondary drawing bath each contain an aqueous solvent containing an acid, a metal salt, or a combination thereof. In certain embodiments, the metal salt includes one or more selected from Li + 、Na + , Ca 2+ and Mg 2+ and one or more anions selected from the group consisting of halides, nitrates, phosphates, carbonates, sulfates, acetates, and the like. Exemplary metal salts include, but are not limited to, NaCl, LiCl, CaCl2, NaBr, LiBr, CaBr2, Li2SO4, Na2SO4, CaSO4, Na3PO4, Li3PO4, and NaOAc. Exemplary acids include, but are not limited to, HCl, H2SO4, and HSO4 - In certain embodiments, the primary and secondary drawing baths contain H2SO4. In certain embodiments, the primary and secondary drawing baths further contain Na2SO4.

[0116] The concentration of the metal salt or acid in the primary drawing bath and the secondary drawing bath may be in the range of 0.1-3 M, 0.1-2.5 M, 0.1-2 M, 0.1-1.5 M, 0.1-1 M, 0.1-0.5 M, 0.5-3 M, 1-3 M, 1.5-3 M, 2-3 M, 0.5-2.5 M, 0.5-2 M, 0.5-1.5 M, 0.5-1 M, 0.25-0.75 M, 0.375-0.75 M, 1-2 M or 1.5-2 M. In certain embodiments, the primary drawing bath comprises an acid having a concentration of about 0.75 M and a metal salt having a concentration of about 0.75 M to about 0.825, and the secondary drawing bath comprises an acid having a concentration of about 0.375 M and a metal salt having a concentration of about 0.375 M to about 0.412.

[0117] In the case where the primary drawing bath and / or the secondary drawing bath contain both an acid and a metal salt, the molar ratio of the acid to the metal salt may be in the range of 0.01:1-1:0.01, 1:0.1-1:5, 1:0.1-1:4, 1:0.1-1:3, 1:0.1-1:2, 1:0.5-1:2, 1:0.5-1:1.5, 1:0.75-1:1.5, 1:0.75-1:1.4, 1:0.75-1:1.3, 1:0.9-1:1.3, 1:0.9-1:1.2 or 1:1.1-1:1.2, respectively. In certain embodiments, the molar ratio of the acid to the metal salt in the primary drawing bath and / or the secondary drawing bath is about 1 to about 1.1, respectively.

[0118] In the case where the primary drawing bath and the secondary drawing bath contain an acid, the pH of the primary drawing bath and the secondary drawing bath may be independently 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0 or less. In certain embodiments, the pH of each of the primary drawing bath and the secondary drawing bath is independently -1 to 6, -1 to 5, -1 to 4, -1 to 3, -1 to 2, -1 to 1, -1 to 0, 0 to 6, 0 to 5, 0 to 4, 0 to 3, 0 to 2, 0 to 1, 0 to 0.5. In certain embodiments, the pH of the primary drawing bath is about 0.12 and the pH of the secondary drawing bath is about 0.43.

[0119] The regenerated bacterial cellulose fibers may be drawn in the primary drawing bath and the secondary drawing bath, optionally by adjusting the drawing ratio. The regenerated bacterial cellulose fibers may be drawn in the coagulation bath at a drawing ratio of 1-2%.

[0120] The step of wet-stretching the regenerated bacterial cellulose fibers in the secondary drawing bath may include stretching the regenerated bacterial cellulose fibers at a temperature of 40-60° C., 40-55° C., 40-50° C., 40-45° C. In certain embodiments, the step of wet-stretching may include stretching the filaments at about 45° C.

[0121] By changing the conditions for preparing regenerated bacterial cellulose fibers according to the method described herein, the properties of the regenerated cellulose fibers thus prepared can be changed. In certain embodiments, the linear density of the regenerated cellulose fibers can be 2-9 dtex, 3-9 dtex, 3-8 dtex, 3-7 dtex, 3-6 dtex, 3-5 dtex, 3-9 dtex, 4-9 dtex, 5-9 dtex, 6-9 dtex or 6-8 dtex. In certain embodiments, the tenacity of the regenerated cellulose fiber at maximum load can be 0.8-2.0 cN / dtex, 0.9-2.0 cN / dtex, 1.0-2.0 cN / dtex, 1.1-2.0 cN / dtex, 1.2-2.0 cN / dtex, 1.3-2.0 cN / dtex, 1.4-2.0 cN / dtex, 1.5-2.0 cN / dtex, 1.3-1.6 cN / dtex, 1.5-1.6 cN / dtex or 1.6-2.0 cN / dtex. Example

[0122] Example 1 - Cultivation of bacterial cellulose by kombucha fermentation

[0123] Boil 3L of water and stir in 12% w / w sucrose while boiling. Add 0.6% w / w black tea leaves from a tea bag and boil the solution for 15 minutes to 1 hour. After cooling to room temperature, remove the tea bag and inoculate 33% w / w SCOBY culture in the sweet tea and pour into a previously sterilized container. Incubate at 31°C for 14 days. The newly formed daughter culture will float and form a cellulose biofilm on available surfaces.

[0124] Example 2 - Preparation of bacterial cellulose by alkali treatment

[0125] Remove the floating bacterial cellulose film from the surface of the culture medium and place it in a container. Pour 12g of sodium hydroxide dissolved in 1L of water into the container. Completely immerse the cellulose film in the solution, then heat it to 60℃ and keep it for 1h. Then wash the BC film with 60℃ water for 1h, and repeat the washing process 2-3 times until the pH value becomes 6-8. A white BC film is obtained after alkali treatment.

[0126] Example 3 - Preparation of bacterial cellulose powder

[0127] Remove the treated BC biofilm from the solution. Before placing the BC biofilm in the vacuum oven, absorb the liquid on the surface with a dry paper towel. Spread the BC biofilm flat on the tray and evenly distribute it. Dry the biofilm in a vacuum oven at 60°C for 12h. The dried cellulose is then cut into small pieces and further crushed into fine particles by two mechanical grindings. The first grinding produces particles with a diameter of <1.0mm, and the second grinding produces a powder with a diameter of <0.2mm.

[0128] Example 4 - Preparation of spinning slurry by TBAH aqueous solvent system

[0129] 4.5 g of BC powder was placed in 95.5 g of 55% TBAH aqueous solution in a reaction vessel to make the cellulose weight content reach 4.5 wt%. The mixture was mechanically stirred at 25 ° C for 12 h to dissolve the BC powder. After complete dissolution, the solution was degassed by centrifugation at 4000 rpm for 15 min. The rheological viscosity of the cellulose solution was measured to be about 50-120 Pa·s. The experimental results are shown in Table 1. Results of Example 4. According to the above experiment, all BC powder was dissolved in the solvent system to form a yellow solution.

[0130]

[0131] Table 1. Results of Example 4: Linear density and toughness at different BC wt%

[0132] Example 5 - Preparation of Spinning Slurry by TBAH / Urea Aqueous Solvent System

[0133] 0.1 g / g of urea was introduced into a 55% TBAH aqueous solution to improve the dissolution of cellulose. The mixture was stirred at room temperature for 30 min until the urea dissolved. 4.5 g of BC powder was placed in 95.5 g of TBAH / urea aqueous solution in a reaction vessel to achieve a cellulose weight content of 4.5 wt%. The mixture was mechanically stirred at 25 ° C for 12 h to dissolve the BC powder. After complete dissolution, the solution was degassed by centrifugation at 4000 rpm for 15 min. The rheological viscosity of the cellulose solution was measured to be about 50-120 Pa·s. The experimental results are shown in Table 2. The results of Example 5. According to the above experiments, all BC powders were dissolved in the solvent system and formed a yellow solution.

[0134]

[0135] Table 2. Results of Example 5: Linear density and toughness at different BC wt%

[0136] Example 6 - Preparation of spinning slurry by metal complex based solvent system

[0137] 4 g of BC powder was placed in 96 g of 1 M Cu(en)2(OH)2 solution in a reaction vessel to achieve a cellulose weight content of 4 wt%. The mixture was mechanically stirred at 80 °C for 1-2 h to dissolve the BC powder. After complete dissolution, the solution was degassed by centrifugation at 4000 rpm for 15 min. The rheological viscosity of the cellulose solution was measured to be about 50-120 Pa·s.

[0138] According to Example 6, all BC powder was dissolved in the solvent system and a viscous dark blue solution was formed.

[0139] Example 7 - Regeneration of fibers by wet spinning

[0140] The fibers were regenerated by wet spinning using a FET-200LAB wet spinning machine.

[0141] 1000 mL of the cellulose solution prepared in Examples 4-6 was extruded at room temperature using a gear pump through a porous spinneret (100 holes, capillary diameter 60 μm or 100 μm). The formation of cellulose fibers was carried out in a primary drawing bath (coagulation) and a secondary drawing bath (stretching) at room temperature. 0.75 M sulfuric acid and sodium sulfate (0.75-0.825 M) were used as coagulant drawing baths, and 0.375 M sulfuric acid and sodium sulfate (0.375-0.412 M) were used as coagulants for the secondary drawing baths. The regenerated bacterial cellulose fibers can be stretched in the primary drawing bath and the secondary drawing bath, optionally by adjusting the drawing ratio. In the coagulation bath, the regenerated bacterial cellulose fibers can be stretched at a drawing ratio of 1.7%. The regenerated fibers are then washed with 60° C. water in a washing bath. The fibers are collected and dried at 40-70° C. for 4-8 h.

[0142] Industrial Applicability

[0143] From an environmental perspective, bacterial cellulose fibers have the advantages of pure cellulose source, less land space required for production, short production cycle, less water consumption, and no use of pesticides compared to traditional regenerated cellulose fibers. In our invention, we use food or beverage waste to generate our bacterial cellulose. In the present invention, SCOBY waste from the production of kupcha is an excellent choice for our demonstration. In 2021, the global kupcha market size was USD 2.64 billion and is expected to expand at a compound annual growth rate (CAGR) of 15.6% from 2022 to 2030 as consumers are turning to health and well-being options.

[0144] In the present invention, bacterial cellulose (BC) is developed as a sustainable source for the production of regenerated cellulose fibers. The key components of the present invention are: (1) developing a solvent system that effectively dissolves bacterial cellulose; and (2) finding the optimal conditions for wet spinning of regenerated bacterial cellulose fibers.

[0145] Acronyms

[0146] BC:Bacterial cellulose

[0147] Cu(en)2(OH)2: Bis(ethylenediamine)copper(II)hydroxide

[0148] DP:Degree of polymerization

[0149] KBC: Kombucha bacterial cellulose

[0150] QAH: Quaternary ammonium hydroxide

[0151] SCOBY: Symbiotic Colony of Bacteria and Yeast

[0152] TBAH: Tetrabutylammonium hydroxide

Claims

1. A method for preparing regenerated bacterial cellulose fibers, the method comprising: contacting a bacterial cellulose powder with an aqueous solution comprising quaternary ammonium hydroxide and optionally urea under conditions that cause at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; or contacting a bacterial cellulose powder with an aqueous solution comprising a metal complex under conditions that cause at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose; and The cellulose slurry is extruded in a coagulation bath to form the regenerated bacterial cellulose fibers.

2. The method according to claim 1, wherein the bacterial cellulose powder is kupcha bacterial cellulose powder.

3. The method of claim 1, wherein the quaternary ammonium hydroxide is NR4OH, wherein R is independently for each instance an alkyl, cycloalkyl or phenyl group; and the metal complex comprises a metal selected from the group consisting of aluminum, calcium, copper, iron, nickel and zinc.

4. The method according to claim 1, wherein the quaternary ammonium hydroxide is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide; and the metal complex is bis(ethylenediamine)copper(II) hydroxide.

5. The method of claim 1, wherein the quaternary ammonium hydroxide is present in the aqueous solution at a concentration of 20-60% w / w; and the metal complex is present in the aqueous solution at a concentration of 0.5-2M.

6. The method of claim 1, wherein the urea is present in the aqueous solution at a concentration of 0.1-0.5% w / w.

7. The method according to claim 1, wherein the coagulation bath comprises a primary drawing bath and further comprises a secondary drawing bath.

8. The method according to claim 7, wherein the primary drawing bath and the secondary drawing bath each independently have a pH of 0-1.

9. The method of claim 7, wherein the primary drawing bath and the secondary drawing bath each comprise an aqueous solution of H2SO4 and optionally Na2SO4.

10. The method according to claim 9, wherein in each of the primary drawing bath and the secondary drawing bath, the concentration of H2SO4 is independently 0.25M to 1M.

11. The method of claim 1, wherein the cellulose slurry comprises bacterial cellulose at a concentration of 2-10% w / w.

12. The method according to claim 1, further comprising: Provide symbiotic colony of bacteria and yeast (SCOBY) biofilm; contacting the SCOBY biofilm with an alkaline aqueous solution to form a treated SCOBY biofilm; optionally washing and drying the treated SCOBY pellicle; as well as The treated SCOBY biofilm is powdered to form the bacterial cellulose powder.

13. The method according to claim 1, further comprising: The regenerated bacterial cellulose fibers are washed with water, and the washed regenerated bacterial cellulose fibers are dried.

14. The method of claim 1, wherein the conditions that cause at least a portion of the bacterial cellulose powder to dissolve comprise: Maintaining the aqueous solution comprising quaternary ammonium hydroxide and optionally urea at 25-50° C. for 8-24 hours; Alternatively, the aqueous solution containing the metal complex is maintained at 75-90° C. for 1-2 hours.

15. The method according to claim 1, wherein the method comprises: contacting the bacterial cellulose powder with an aqueous solution comprising 20-60% w / w N(C1-C5)4OH and optionally 0.1-0.5% w / w urea at 25-40°C for 8-24 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose at a concentration of 4-10% w / w; or contacting a bacterial cellulose powder with an aqueous solution comprising 0.5 M to 2 M bis(ethylenediamine)copper(II) hydroxide at 75-90° C. for 1-2 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose at a concentration of 2-6% w / w; as well as The cellulose slurry is extruded in a coagulation bath including a primary drawing bath and a secondary drawing bath, wherein the primary drawing bath and the secondary drawing bath independently have a pH of 0-0.5, thereby forming the regenerated bacterial cellulose fibers.

16. The method according to claim 15, wherein the cellulose slurry comprises bacterial cellulose in a concentration of 3.5-5.5% w / w.

17. The method according to claim 15, further comprising: Provide symbiotic colony of bacteria and yeast (SCOBY) biofilm; contacting the SCOBY biofilm with an alkaline aqueous solution to form treated SCOBY particles; optionally washing and drying the treated SCOBY pellicle; as well as The treated SCOBY biofilm is powdered to form the bacterial cellulose powder.

18. The method according to claim 17, wherein the pH of the alkaline aqueous solution is 13-14.

19. The method of claim 17, wherein the alkaline aqueous solution comprises NaOH.

20. The method of claim 1, wherein the method comprises: Provide symbiotic colony of bacteria and yeast (SCOBY) biofilm; contacting the SCOBY biofilm with an alkaline aqueous solution having a pH of 13-13.5, thereby forming a treated SCOBY biofilm; optionally washing and drying the treated SCOBY film; Powdering the treated SCOBY bacterial film to form the bacterial cellulose powder; contacting the bacterial cellulose powder with an aqueous solution comprising 20-60% w / w N(C1-C5)4OH and optionally 0.1-0.5% w / w urea at 25-40°C for 8-24 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose at a concentration of 3.5-5.5% w / w; or contacting the bacterial cellulose powder with an aqueous solution comprising 0.5M to 2M bis(ethylenediamine)copper(II) hydroxide at 75-90°C for 1-2 hours, causing at least a portion of the bacterial cellulose powder to dissolve, thereby forming a cellulose slurry comprising bacterial cellulose at a concentration of 3.5-5.5% w / w; and The cellulose slurry is extruded in a coagulation bath including a primary drawing bath and a secondary drawing bath, wherein the primary drawing bath and the secondary drawing bath each contain an aqueous solution of H2SO4 and Na2SO4 with a pH of 0-0.5, thereby forming the regenerated bacterial cellulose fibers.

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