Dehydration method of microbial cellulose

Abstract

The invention relates to a method for dehydrating microbial cellulose. The method comprises the following steps: contacting a wet microbial cellulose material with a hydrophilic polymer solution; maintaining the contact between the wet microbial cellulosic material and the hydrophilic polymer solution for a treatment period of time to remove at least a portion of the water from the wet microbial cellulosic material; and removing the dehydrated microbial cellulose from the hydrophilic polymer solution. The invention further relates to a dehydrated microbial cellulose material comprising: from 25 to 95% by dry weight of microbial cellulose; and 5-75% by dry weight of a hydrophilic polymer.

Description

Technical Field

[0001] This invention relates to a method for dehydrating microbial cellulose. More specifically, the method of this invention produces dehydrated microbial cellulose with improved water absorption and retention capacity. Furthermore, this invention also relates to a dehydrated microbial cellulose material.

[0002] This invention also relates to a method for preparing a plant growth medium. More specifically, this invention provides a method for preparing a plant growth medium by dehydrating microbial cellulose. Furthermore, this invention also relates to a plant growth medium. Background Technology

[0003] The following discussion of the background art is intended only to facilitate understanding of the invention. This discussion does not constitute an assumption or admission that any material mentioned was, or was, part of common general knowledge at the priority date of this application.

[0004] Microbial cellulose, also known as bacterial cellulose, is a natural cellulose synthesized by bacteria. Microbial cellulose is produced in the form of fine protofibrils, typically 20-100 nm in diameter. These fine protofibrils interweave to form a dense three-dimensional matrix. Microbial cellulose has high water-holding capacity due to its strong hydrophilicity and high surface area to mass ratio. Wet microbial cellulose in its original state contains approximately 99% water. The resulting wet microbial cellulose forms a gel-like biofilm.

[0005] The original microbial cellulose biofilm can be dried by evaporating moisture from the cellulose matrix. However, it has been found that drying the material leads to irreversible internal hydrogen bonds. This process is also known as "keratinization." Without being bound by theory, it is understandable that water bridges the microbial cellulose fibers with hydrogen bonds, keeping the fibers separate. Dehydration caused by evaporative water loss removes these bridges, leading to the aggregation and accumulation of the microbial cellulose fibers. Keratinization of microbial cellulose significantly reduces its water absorption and retention capacity. Depending on temperature and conditions, the dried material cannot be rehydrated in water by more than 1–10 times its weight. To maintain the original water-holding properties of microbial cellulose, raw microbial cellulose must be kept moist, which increases the complexity of storing and transporting microbial cellulose materials.

[0006] One useful application of microbial cellulose is as a plant growth medium. This is primarily due to the material's high water absorption and retention capacity. However, the loss of water absorption and retention capacity after drying means that microbial cellulose must be kept moist to fully utilize these properties. This increases the cost of transporting and storing the product. Although dried microbial cellulose can still be rehydrated and used as a plant growth medium, the drying process reduces the water absorption and retention capacity of the rehydrated material, affecting its performance as a plant growth medium.

[0007] In this specification, unless the context otherwise requires, the word “comprise” or variations such as “comprises” or “comprising” will be understood to imply the inclusion of one or a set of specified integers, but not to exclude any other integers or groups of integers.

[0008] The invention described herein may include one or more numerical ranges (e.g., dimensions, displacements, and field strengths). A range of values ​​will be understood to include all values ​​within that range, including the value defining the range and values ​​adjacent to the range that result in the same or substantially the same result as the value directly adjacent to the value defining the boundary of the range. Invention Overview

[0010] According to a first aspect of the present invention, a method for dehydrating microbial cellulose is provided, the method comprising: Contact the wet microbial cellulose material with a hydrophilic polymer solution; The contact between the wet microbial cellulose and the hydrophilic polymer solution is maintained for a treatment period to remove at least some of the water from the wet microbial cellulose; and Dehydrated microbial cellulose is extracted from a hydrophilic polymer solution.

[0011] The inventors of this invention have determined that contact between wet microbial cellulose and a hydrophilic polymer solution will result in the removal of at least a portion of the water from the wet microbial cellulose and its replacement by the hydrophilic polymer.

[0012] In one embodiment of the invention, the method further includes the step of: Dehydrated microbial cellulose is dried to produce dried microbial cellulose material.

[0013] The inventors of this invention have discovered that dried microbial cellulose material can be produced by removing residual water from dehydrated microbial cellulose using conventional methods. It has been found that removing at least some of the water from microbial cellulose using a hydrophilic polymer solution improves the water absorption and retention capacity of the dried microbial cellulose. It is not intended to be theoretically restrictive, but it will be understood that the incorporation of the hydrophilic polymer will at least partially maintain the structure of the microbial cellulose during the subsequent drying process, thereby improving the water absorption and retention capacity of the dried material.

[0014] In one form of the invention, the microbial cellulose material is produced by any suitable bacterial species known in the art, for example, *Dystrophus occulta*. Sarcina sp. ), Agrobacterium ( Agrobacterium sp. ), Bacillus colomaformis ( Komagataeibacter sp ) and Acetic Acid Bacillus ( Acetobacter sp ).

[0015] Throughout this specification, unless otherwise required herein, the term "wet microbial cellulose" or variations thereof shall be understood to refer to microbial cellulose material having a moisture content of at least 90% by weight. Preferably, the wet microbial cellulose has a moisture content of at least 95% by weight. More preferably, the wet microbial cellulose has not been previously dried.

[0016] Throughout this specification, unless otherwise required, the term "dehydrated microbial cellulose" or variations thereof shall be understood to mean wet microbial cellulose from which at least 50% by weight of the initial moisture content has been removed. Initial moisture content is the moisture content of the wet microbial cellulose before treatment.

[0017] The method according to any of the preceding claims, wherein the moisture content of the dehydrated microbial material is 50% or less of the moisture content of the wet microbial cellulose.

[0018] In one form of the invention, wet microbial cellulose is provided as a microbial cellulose biofilm or a fragment thereof. Throughout this specification, unless otherwise required herein, the term "microbial cellulose biofilm" or variations thereof will be understood to refer to microbial cellulose material produced by static fermentation. Those skilled in the art will recognize that statically fermented microbial cellulose is produced by bacteria as a three-dimensional matrix of microbial cellulose protocellulose. This matrix forms a dense biofilm with a gel-like membrane morphology. It will be understood that the term "microbial cellulose biofilm" does not include microbial cellulose material produced by stirred fermentation. Preferably, the microbial cellulose material is not homogenized or pulped prior to treatment using the method of the present invention.

[0019] In one embodiment of the invention, the wet microbial cellulose film is cut into fragments before being processed using the method of the invention. Preferably, the minimum size of the wet microbial cellulose film fragments is 1 cm. 3 .

[0020] In one embodiment of the invention, the wet microbial cellulose material contains less than 5% by weight of microbial cellulose. Preferably, the wet microbial cellulose material contains 0.5-1.0% by weight of microbial cellulose.

[0021] Preferably, the hydrophilic polymer solution comprises one or more polysaccharides. More preferably, the polysaccharide is selected from one or more of guar gum, gum arabic, I-carrageenan, carboxymethyl cellulose (CMC), and alginate. Even more preferably, the hydrophilic polymer solution is a CMC solution. The carboxymethyl cellulose used is preferably an alkali metal salt of carboxymethyl cellulose, such as a sodium, potassium, or ammonium salt of CMC. Unless otherwise specified, CMC in this specification refers to the sodium salt of CMC.

[0022] Preferably, the concentration of the hydrophilic polymer solution is less than 20%. More preferably, the concentration of the hydrophilic polymer solution is less than 10%. In one embodiment of the invention, the concentration of the hydrophilic polymer solution is 2-10%. In an alternative embodiment of the invention, the concentration of the hydrophilic polymer solution is 2-6%. In an alternative embodiment of the invention, the concentration of the hydrophilic polymer solution is 1-3%.

[0023] In one embodiment of the invention, the ratio of the hydrophilic polymer solution to the wet microbial cellulose is at least 0.5:1. In another embodiment of the invention, the ratio of the hydrophilic polymer solution to the wet microbial cellulose is at least 1:1. In yet another embodiment of the invention, the ratio of the hydrophilic polymer solution to the wet microbial cellulose is at least 2:1.

[0024] Preferably, the wet microbial cellulose material is immersed in a hydrophilic polymer solution.

[0025] In one embodiment of the invention, the processing time is at least 6 hours. Preferably, the processing time is at least 12 hours. More preferably, the processing time is at least 24 hours. Even more preferably, the processing time is at least 48 hours.

[0026] In one embodiment of the invention, the contact between the wet microbial cellulose material and the hydrophilic polymer solution is carried out at ambient temperature.

[0027] In an alternative embodiment of the invention, the contact between the wet microbial cellulose material and the hydrophilic polymer solution is carried out at an elevated temperature. In one embodiment of the invention, the temperature is 50-100°C. In another embodiment of the invention, the temperature is 50-70°C. In one embodiment of the invention, the elevated temperature is maintained throughout the treatment period. In an alternative embodiment of the invention, the elevated temperature is maintained for at least a portion of the treatment period.

[0028] In one embodiment of the invention, the weight of the dehydrated microbial cellulose is less than 40% of the weight of the wet microbial cellulose material. Preferably, the weight of the dehydrated microbial cellulose is 5-20% of the weight of the wet microbial cellulose material.

[0029] In one form of the invention, the dehydrated microbial cellulose is contacted with a further hydrophilic polymer material to remove additional water.

[0030] In one embodiment of the invention, the drying of dehydrated microbial cellulose is carried out at ambient temperature. In an alternative embodiment of the invention, the drying of dehydrated microbial cellulose is carried out at elevated temperature.

[0031] In one embodiment of the invention, dried microbial cellulose is subjected to size reduction processing.

[0032] According to a second aspect of the present invention, a dehydrated microbial cellulose material produced by the method of the first aspect of the present invention is provided.

[0033] According to a third aspect of the present invention, a dehydrated microbial cellulose material is provided, the dehydrated microbial cellulose material comprising: On a dry weight basis, it contains 25-95% microbial cellulose; and 5-75% hydrophilic polymers by dry weight.

[0034] Preferably, the hydrophilic polymer comprises one or more polysaccharides. More preferably, the polysaccharide is selected from one or more of guar gum, gum arabic, I-carrageenan, carboxymethyl cellulose (CMC), and alginate. Still preferably, the hydrophilic polymer is CMC.

[0035] Preferably, the hydrophilic polymer content is 5-60% on a dry weight basis.

[0036] According to a fourth aspect of the present invention, a method for drying microbial cellulose is provided, the method comprising: Contact the wet microbial cellulose material with a hydrophilic polymer solution; The contact between the wet microbial cellulose material and the hydrophilic polymer solution is maintained for a treatment period to remove at least some of the water from the wet microbial cellulose material. Dehydrated microbial cellulose was removed from a hydrophilic polymer solution; and Dry microbial cellulose is dried to produce dried microbial cellulose material.

[0037] According to a fifth aspect of the present invention, a dried microbial cellulose material produced by the method of the fourth aspect of the present invention is provided.

[0038] According to a sixth aspect of the present invention, a method for producing a plant growth medium is provided, the method comprising: Contact the wet microbial cellulose material with a hydrophilic polymer; The contact between the microbial cellulose material and the hydrophilic polymer solution is maintained for a treatment period to remove at least some of the water from the wet microbial cellulose material; and Dehydrated microbial cellulose is extracted from a hydrophilic polymer solution to obtain a plant growth medium.

[0039] Throughout this instruction manual, unless otherwise required, the term "plant growth medium" or variations thereof will be understood to refer to a medium that can be used as an alternative to soil as a support for plant growth. Such a medium provides substances in which seeds can germinate and provides support for plant roots. It will be understood that the resulting plant growth medium will require the addition of water for the plants to grow.

[0040] Microbial cellulose is known to be suitable as a plant growth medium due to its high water absorption and retention capacity. However, drying microbial cellulose using conventional evaporation drying techniques significantly reduces its water absorption and retention capacity. The dehydration method of this invention has been found to produce dehydrated microbial cellulose materials with increased water absorption and retention capacity. This increased water absorption and retention capacity is beneficial for the material's use as a plant growth medium, as it increases the volume of water available to the plant.

[0041] In one embodiment of the invention, the method further includes the step of: Dehydrated microbial cellulose is dried to obtain a dry plant growth medium.

[0042] The inventors have discovered that removing at least a portion of the water from wet microbial cellulose using a hydrophilic polymer solution will allow for the production of a dry material with improved water absorption and retention capacity by removing the remaining water from dehydrated microbial cellulose using conventional drying methods.

[0043] In one form of the invention, the plant growth medium is subjected to a size reduction process. In another form of the invention, the dried plant growth medium is subjected to a size reduction process. Although it is possible for seeds to germinate on untreated, moist microbial cellulose, the inventors have determined that after germination, roots cannot penetrate into the dense network of protocellulose. Therefore, roots cannot utilize the water held within the microbial cellulose structure. The inventors have discovered that reducing the particle size of microbial cellulose allows plant roots to penetrate while maintaining the water-holding capacity required for the suitability of the plant growth medium. Advantageously, unlike the dense network of untreated microbial cellulose, the roots of plant seeds can penetrate the size-reduced material and obtain the structural support for a normally developing root system. Furthermore, it has been found that particle size reduction also increases the rate of water absorption. In one form of the invention, the size reduction process reduces the particle size of the dried plant growth medium to less than 1000 μm with a D90. In another form of the invention, the size reduction process reduces the particle size of the dried plant growth medium to less than 500 μm with a D90. In one form of the invention, the size reduction process reduces the particle size of the dried plant growth medium to a D10 greater than 50 μm.

[0044] Preferably, the dimensional reduction process is a mechanical dimensional reduction process.

[0045] In one embodiment of the invention, the method further includes contacting the plant growth medium with water. Preferably, the mixture of plant growth medium and water is stirred.

[0046] According to a seventh aspect of the present invention, a plant growth medium produced by the method of the fourth aspect of the present invention is provided.

[0047] According to an eighth aspect of the present invention, a plant growth medium is provided, the plant growth medium comprising: On a dry weight basis, 25-75% microbial cellulose; and 25-75% hydrophilic polymer by dry weight.

[0048] Preferably, the hydrophilic polymer content is 30-60% on a dry weight basis.

[0049] Preferably, the hydrophilic polymer is selected from one or more polysaccharides. More preferably, the polysaccharide is selected from one or more of guar gum, gum arabic, I-carrageenan, carboxymethyl cellulose (CMC), and alginate. Even more preferably, the hydrophilic polymer is CMC. Brief description of the attached diagram

[0051] Further features of the invention are described more fully in the following description of several non-limiting embodiments. This description is for illustrative purposes only and should not be construed as limiting the scope of the broad overview, disclosure, or description of the invention listed above. The description will be taken with reference to the accompanying drawings, in which: Figure 1 The graph shows the decrease in biofilm thickness during contact with the hydrophilic polymer solution; and Figure 2 This demonstrates the water-holding capacity of dried materials with different particle sizes.

[0052] Description of the implementation plan

[0053] This invention relates to a method for dehydrating microbial cellulose. The method of this invention involves contacting wet microbial cellulose with a hydrophilic polymer solution to reduce the water content of the wet microbial cellulose.

[0054] The dehydrated microbial cellulose was then removed from the hydrophilic polymer solution.

[0055] It has been found that the method of the present invention improves the water absorption and retention capacity of dehydrated products compared to conventional drying methods. It has also been found that the method of the present invention reduces the energy required to remove water from wet microbial cellulose material. In some embodiments, the dehydrated material is subjected to a drying step to remove residual water and produce dry microbial cellulose material.

[0056] Microbial cellulose

[0057] The method of this invention aims to remove water from wet microbial cellulose. Throughout this specification, unless otherwise required, the term "microbial cellulose" refers to cellulose produced by bacteria.

[0058] Microbial cellulose used in the method of the present invention can be produced by various methods known in the art.

[0059] In a preferred embodiment of the invention, the microbial cellulose is produced by bacteria of the genus *Acetobacter*. *Acetobacter* bacteria can be readily identified by those skilled in the art by colony growth on a culture medium containing approximately 7% ethanol and sufficient calcium carbonate to make it partially transparent. When the *Acetobacter* colonies form sufficient acetic acid from the ethanol, the calcium carbonate surrounding the colonies dissolves, forming a very distinct transparent area.

[0060] During static fermentation, microbial cellulose forms a sheet-like biofilm on the surface of the culture medium. As growth continues, the thickness of the initial microbial cellulose biofilm increases. Once the desired thickness is reached, the wet cellulose material is collected. Collecting the wet microbial cellulose material involves removing the microbial cellulose biofilm from the culture medium. In one embodiment, the thickness of the microbial cellulose is 0.5-5 cm. In another embodiment, the thickness of the microbial cellulose is 0.5-4 cm. In another embodiment, the thickness of the microbial cellulose is 0.5-3 cm. In another embodiment, the thickness of the microbial cellulose is 0.5-2 cm. In another embodiment, the thickness of the microbial cellulose is 0.5-1 cm.

[0061] In some embodiments, the wet microbial cellulose is washed before contact with the hydrophilic polymer solution. Washing preferably involves heating in water at a temperature between 60°C and 100°C. The wet microbial cellulose may be washed several times.

[0062] In some embodiments, the wet microbial cellulose is purified before contact with a hydrophilic polymer solution. The purification step preferably includes contacting the wet microbial cellulose with a detergent.

[0063] The wet microbial cellulose should not have been dried before it comes into contact with the hydrophilic polymer solution.

[0064] Contact with hydrophilic polymer solutions

[0065] Wet microbial cellulose is contacted with a hydrophilic polymer solution, and this contact is maintained for the treatment period. The contact between the microbial cellulose and the hydrophilic polymer solution removes some water from the wet microbial cellulose. It is not desirable to be bound by theory, which assumes that the hydrophilic polymer is more hydrophilic than microbial cellulose, causing water to be extracted from the wet microbial cellulose. The contact between the microbial cellulose and the hydrophilic polymer solution also allows the hydrophilic polymer to infuse into the structure of the microbial cellulose. It will be understood that when the remaining water is removed, the degree of keratinization within the structure decreases, thereby providing a dry material with higher water absorption and retention capacity.

[0066] Preferably, the wet microbial cellulose material is provided as a biofilm or fragments thereof. It should be understood that the microbial cellulose biofilm treated by the present invention can be broken down into smaller fragments before contact with the hydrophilic polymer solution. The structure of the microbial cellulose should remain unchanged in other respects. The wet microbial cellulose in contact with the hydrophilic polymer solution should not have undergone homogenization or similar pulping treatment prior to contact. As is known to those skilled in the art, homogenization of the original microbial cellulose will break down the fibrillary network and form a slurry of ground microbial cellulose. The inventors of the present invention have discovered that contact of such a slurry with the hydrophilic polymer solution makes it difficult to separate the dehydrated microbial cellulose from the aqueous phase. Furthermore, the wet microbial cellulose in contact with the hydrophilic polymer solution should not have been produced during stirred fermentation. Microbial cellulose produced by stirred fermentation has a slurry-like consistency and therefore encounters similar separation problems.

[0067] Preferably, the wet microbial cellulose is immersed in a hydrophilic polymer solution.

[0068] Preferably, the hydrophilic polymer solution comprises one or more polysaccharides. More preferably, the polysaccharide is selected from guar gum, gum arabic, I-carrageenan, carboxymethyl cellulose (CMC), and alginate. Even more preferably, the hydrophilic polymer solution is a CMC solution.

[0069] Preferably, the concentration of the hydrophilic polymer solution is less than 20%. More preferably, the concentration of the hydrophilic polymer solution is less than 10%.

[0070] The inventors have discovered that the maximum concentration of a hydrophilic polymer solution depends on its viscosity. If the viscosity is too high, the polymer solution becomes a thick gel, reducing its effectiveness and making it difficult to work. As is known to those skilled in the art, the viscosity of a hydrophilic polymer solution is a factor of polymer type, polymer concentration, and solution temperature. Polymers with higher average molecular weights exhibit higher concentrations in solution than those with lower molecular weights. Therefore, the maximum concentration of a hydrophilic polymer depends on the average molecular weight of the hydrophilic polymer solution.

[0071] As known to those skilled in the art, polymer compositions comprise polymer chains containing repeating monomer units. The degree of polymerization (DP) is the number of monomer units in a polymer molecule. The molecular weight of a particular polymer molecule is the product of the degree of polymerization and the molecular weight of the repeating unit. A polymer composition consists of many polymer molecules with different chain lengths and molecular weights. This results in polymers with different molecular weight distributions. The average molecular weight of a polymer can be described by various parameters. For the purposes of this invention, the average molecular weight of the polymer will be the weighted average molecular weight (M). w The weighted average molecular weight of polymers is well defined in the literature and can be determined by analytical methods such as gel permeation chromatography.

[0072] M of the hydrophilic polymer w In embodiments with a concentration of less than 150,000, the concentration of the hydrophilic polymer solution is preferably between 2% and 10%.

[0073] M of the hydrophilic polymer w In embodiments with a concentration between 150,000 and 500,000, the concentration of the hydrophilic polymer solution is preferably between 2% and 6%.

[0074] M of the hydrophilic polymer w In embodiments with a concentration higher than 500,000, the concentration of the hydrophilic polymer solution is preferably between 1% and 3%.

[0075] The inventors have discovered that the average molecular weight of the hydrophilic polymer solution also affects the extent to which water is removed from wet microbial cellulose and the water absorption capacity of the resulting dried material. Decreasing the average molecular weight of the hydrophilic polymer solution reduces the amount of water removed from wet microbial cellulose but increases the polymer content of the resulting dried material. Increasing the average molecular weight of the hydrophilic polymer increases the amount of water removed from wet microbial cellulose but decreases the polymer content of the resulting dried material. Therefore, the selection of hydrophilic polymers can be used to favor increased water removal, increased swelling retention, or a mixture thereof.

[0076] In one embodiment of the invention, the hydrophilic polymer solution comprises a low average molecular weight (LM) w Hydrophilic polymers and high average molecular weight (HM) w A mixture of hydrophilic polymers. The inventors have discovered that including hydrophilic polymers with different average molecular weights can increase the overall polymer content of water removal and drying products. Not wishing to be bound by theory, they will understand LM. w The smaller molecular size of hydrophilic polymers allows them to penetrate microbial cellulose matrices more effectively, which in turn reduces their dehydration effect, whereas for larger molecular sizes, HM... W The opposite is true for hydrophilic polymers.

[0077] In one embodiment, the hydrophilic polymer solution contains 1-2% HM w Hydrophilic polymers and 0.5-4% LM w Hydrophilic polymer. In one embodiment, the hydrophilic polymer solution contains 1-2% HM. w Hydrophilic polymers and 2-4% LM w Hydrophilic polymers.

[0078] In embodiments where the hydrophilic polymer solution comprises two or more hydrophilic polymers with known average molecular weights, a weighted average of each hydrophilic polymer can be used to determine the average molecular weight of the hydrophilic polymer. Similarly, the total concentration of the hydrophilic polymer solution is the total weight percentage of each respective hydrophilic polymer.

[0079] In one embodiment, the ratio of the hydrophilic polymer solution to the wet microbial cellulose is at least 0.5:1. In another embodiment, the ratio is at least 1:1. In yet another embodiment, the ratio is at least 2:1. Water removed from the wet microbial cellulose entering the hydrophilic polymer solution will dilute the hydrophilic polymer solution. As discussed above, the concentration of the hydrophilic polymer solution should be maintained above a specific concentration to ensure sufficient water removal from the wet microbial cellulose. The ratio of the hydrophilic polymer solution should be controlled to ensure that the concentration is not diluted below a minimum concentration. This ratio will be affected by the initial concentration of the hydrophilic polymer solution.

[0080] In one embodiment of the invention, the treatment time is at least 6 hours. In one embodiment, the treatment time is at least 12 hours. In another embodiment, the treatment time is at least 24 hours. In yet another embodiment, the treatment time is at least 48 hours. The contact between the wet microbial cellulose and the hydrophilic polymer solution must be maintained for a sufficient time to reduce the water content of the microbial cellulose and allow the hydrophilic polymer to be infused into the microbial cellulose structure. The inventors will understand that water removal is a relatively rapid process, while the infusion of CMC proceeds relatively slowly. The inventors have found that the concentration of the hydrophilic polymer in the dehydrated material affects the water absorption and retention capacity of the dried product. The treatment time should be controlled to achieve the desired hydrophilic polymer concentration. It has been found that the thickness of the wet microbial cellulose material affects the required treatment time. The inventors have found that an optimal hydrophilic polymer concentration is achieved for wet microbial cellulose material with a thickness of 0.5-1 cm using a treatment time of 24-72 hours. For thicker wet microbial cellulose material, a longer treatment time of 72-96 hours is required to achieve the optimal hydrophilic polymer concentration.

[0081] In one embodiment of the invention, the contact between the wet microbial cellulose material and the hydrophilic polymer solution is carried out at ambient temperature. In an alternative embodiment, the hydrophilic polymer solution is heated above 50°C prior to contact. The heated hydrophilic polymer solution may be cooled before contact with the wet microbial cellulose material.

[0082] In an alternative form of the invention, the contact between the wet microbial cellulose material and the hydrophilic polymer solution is carried out at an elevated temperature. In one embodiment, the temperature is 50-100°C. In another embodiment, the temperature is 50-70°C. In one form of the invention, the elevated temperature is maintained throughout the treatment period. In an alternative form of the invention, the elevated temperature is maintained for a portion of the treatment period. The inventors have discovered that contact between the wet microbial cellulose and the hydrophilic polymer solution at an elevated temperature can increase the rate of hydrophilic polymer infusion into the microbial cellulose material. This can shorten the required treatment time.

[0083] Another advantage of contacting wet microbial cellulose materials with hydrophilic polymer solutions at elevated temperatures is the prevention of bacterial and fungal growth.

[0084] Dehydrated products

[0085] After the treatment period is complete, the dehydrated microbial cellulose material is removed from the hydrophilic polymer solution, and excess solution is removed by gently wiping or scraping the surface. The remaining hydrophilic polymer solution can be used to treat more wet microbial cellulose.

[0086] Removing water from microbial cellulose results in a material of significantly less thickness. In one embodiment of the invention, the weight of the dehydrated microbial cellulose is less than 20% of the weight of the wet microbial cellulose material. Preferably, the weight of the dehydrated microbial cellulose is 5-20% of the weight of the wet microbial cellulose material. The weight of the dehydrated microbial cellulose can be used to determine whether sufficient water has been removed by the hydrophilic polymer solution. If not, the dehydrated microbial cellulose can be re-exposed to the hydrophilic polymer solution to remove further water.

[0087] Dehydrated microbial cellulose material will have a hydrophilic polymer content. The final hydrophilic polymer content will be a result of the treatment time, contact temperature, thickness of the wet microbial cellulose, concentration of the hydrophilic polymer solution, and type of hydrophilic polymer used. In one embodiment, the dehydrated microbial cellulose material has 5-75% hydrophilic polymer on a dry weight basis. It has been found that the hydrophilic polymer content affects the water absorption and retention capacity of dried microbial cellulose. It has been found that a hydrophilic polymer content of 30-60% on a dry weight basis yields dehydrated material with demonstrated improved water absorption capacity. However, a polymer content as low as 5% on a dry weight basis obtained from more efficient dehydration can still prevent keratinization and allow the material to absorb and retain sufficient water for specific applications. A hydrophilic polymer content higher than 75% on a dry weight basis becomes detrimental to water absorption and retention capacity because there is insufficient microbial cellulose in the material upon rehydration. The hydrophilic polymer content can be controlled to suit the desired purpose by selecting the polymer used and adjusting the treatment time, contact temperature, thickness of the wet microbial cellulose, and concentration of the hydrophilic polymer solution.

[0088] The method of this invention produces a dehydrated microbial cellulose product that can be rapidly rehydrated. Removing water from wet microbial cellulose reduces the weight and thickness of the cellulose material, which is considered advantageous for the transport and storage of microbial cellulose materials. The dehydration method of this invention allows water removal for transport and storage with virtually no impact on the rehydration of the dehydrated material. It is also considered useful in applications where additives (such as antibiotics, vitamins, etc.) are introduced into the microbial material. Such additives can be absorbed into the dehydrated microbial cellulose during the rehydration process. It is also anticipated that the dehydrated microbial cellulose will be able to accommodate unstable additives at the point of use, which would otherwise degrade during transport and storage.

[0089] Because the dehydration method of the present invention does not completely remove water from the wet microbial cellulose, the resulting dehydrated microbial cellulose is a hydrated material. The dehydrated microbial cellulose material is applied to applications in which a hydrated material is preferred. Such applications are thought to include cosmetic applications, such as skin treatments, and health care applications, such as wound care. Hydrated materials are also suitable for applications in which elastic materials are useful.

[0090] dry

[0091] In one embodiment of the invention, dehydrated microbial cellulose undergoes a drying step to remove residual water from the material. The inventors have discovered that at least a substantial portion of the residual water in dehydrated microbial cellulose can be removed to produce a dried material. Advantageously, it has been found that the dried material exhibits improved water absorption and retention capacity compared to dried microbial cellulose produced using only conventional drying techniques. Removing residual water from the dehydrated microbial cellulose material further reduces the weight and thickness of the microbial cellulose, thereby reducing transportation / transfer costs. The method of the present invention also prevents the need for wet microbial cellulose to be stored in a controlled environment to prevent unintentional drying. The high water absorption and retention capacity of the dried material is also considered to allow its use as a biodegradable absorbent material.

[0092] Preferably, an evaporative drying method is used to dry the dehydrated microbial cellulose material. Throughout this specification, the term "evaporative drying method" will be understood to include any method that causes water to evaporate from the dehydrated wet microbial cellulose material. Suitable evaporative drying methods include air drying, conventional drying, contact drying, radiation drying including infrared radiation, dielectric drying including microwaves, high-frequency drying, freeze drying, and vacuum drying. In one embodiment, the drying of the dehydrated microbial cellulose is carried out at ambient temperature. In an alternative embodiment, the drying of the dehydrated microbial cellulose is carried out at an elevated temperature. Preferably, the drying is carried out at a temperature of at least 70°C.

[0093] Size reduction

[0094] The dehydrated material can retain its original shape. Alternatively, the dehydrated material can be dimensionally reduced. The inventors have discovered that the particle size of the dehydrated material can be freely reduced without significantly affecting its water absorption capacity. In embodiments where the method includes a drying step, the dried material can retain its original shape. Alternatively, the dried material can be dimensionally reduced. The inventors have discovered that the particle size of the dried material can be freely reduced without significantly affecting its water absorption capacity.

[0095] product

[0096] The present invention further relates to dehydrated microbial cellulose products produced using the dehydration methods discussed above.

[0097] In one embodiment, the dehydrated microbial cellulose material comprises: 25-95% microbial cellulose by dry weight; and 5-75% hydrophilic polymer by dry weight.

[0098] Preferably, the concentration of the hydrophilic polymer is 5-60% on a dry weight basis.

[0099] The present invention further relates to dried microbial cellulose products produced using the drying methods discussed above.

[0100] In one embodiment, the dried microbial cellulose material comprises: 25-95% microbial cellulose; and 5-75% hydrophilic polymer.

[0101] Preferably, the concentration of the hydrophilic polymer is 5-60%.

[0102] growth materials

[0103] The present invention further relates to a method for producing a plant growth medium, the method comprising: Wet microbial cellulose material is brought into contact with a hydrophilic polymer solution; Maintaining contact between the microbial cellulose material and the hydrophilic polymer solution for a certain treatment time; and Dehydrated microbial cellulose is removed from the solution to obtain a plant growth medium.

[0104] Microbial cellulose is known to be useful as a plant growth medium due to its high water absorption and retention capacity. However, drying microbial cellulose using conventional evaporation drying techniques significantly reduces its water absorption and retention capacity. The dehydration method of the present invention has been found to produce dehydrated microbial cellulose materials with increased water absorption and retention capacity. This increased water absorption and retention capacity is beneficial for using the material as a plant growth medium, as it increases the volume of water available to the plant.

[0105] The plant growth medium of the present invention is intended to be reconstituted with water to make it suitable for plant growth. Advantageously, the inventors have determined that the applicability of the method of the present invention allows for cost-effective dehydration and transshipment (transferring dehydrated microbial cellulose from its place of production to its place of use as a plant growth medium).

[0106] The discussion of the microbial cellulose dehydration method according to the first aspect of the present invention is also applicable to dehydration methods used to produce plant growth media.

[0107] Preferably, the hydrophilic polymer solution comprises one or more polysaccharides. More preferably, the polysaccharide is selected from guar gum, gum arabic, I-carrageenan, carboxymethyl cellulose (CMC), and alginate. Even more preferably, the hydrophilic polymer solution is a CMC solution.

[0108] In one implementation, the method further includes the step of: Dehydrated microbial cellulose is dried to produce a dry plant growth medium.

[0109] In a preferred embodiment, the dried plant growth medium is processed to reduce its size. The inventors have discovered that reducing the particle size facilitates the penetration of plant roots into the plant growth medium. Furthermore, it has been found that reducing the particle size also increases the water absorption rate.

[0110] In one implementation, the size reduction process reduces the particle size of the dried plant growth medium to less than 1000 μm with a D90.

[0111] In one embodiment, the size reduction process reduces the particle size of the dried plant growth medium to less than 500 μm with a D50. Preferably, the size reduction process reduces the particle size of the dried plant growth medium to less than 400 μm with a D50.

[0112] In one embodiment, the size reduction process reduces the particle size of the dried plant growth medium to a D10 greater than 50 μm.

[0113] As those skilled in the art will understand, particle size distribution is typically expressed using the D-value. The meanings of the respective D-values ​​are as follows: D10: 10% of the volume of particles are smaller than its size; D50: 50% of the volume of particles are smaller than their size; and D90: 90% of the volume of particles are smaller than its size.

[0114] For the purposes of this invention, the term "particle size" is defined as the external dimensions of particles determined by sieving particle size analysis according to the sieving test described in more detail herein. The particle sample is sieved as described, and the results are recorded. The results of this sieving particle size analysis adequately define the particle size for the purposes of this invention. Regarding the characteristics of the sieve used, the results of sieving separation can be described by two equivalent conventions. One approach is to describe the particle size in terms of the pore size in the sieve. For example, in principle, for the purposes of this invention, particles retained on a sieve with 500 μm pores are considered to have a particle size greater than or equal to 500 μm. Particles that pass through a sieve with 500 μm pores but are retained on a sieve with 100 μm pores are considered to have a particle size between 100 and 500 μm.

[0115] As those skilled in the art will know, for non-spherical particles, sieving tests can only determine the size of a specific dimension of a particular particle. In the case of elongated particles, the shorter dimensions of the particles can pass through the mesh openings, resulting in particles with larger cross-sections passing through the mesh. For this reason, test results are typically expressed as the volume percentage of particles that normally pass through a sieve in one dimension but remain on a sieve in a second dimension.

[0116] Preferably, the dimensional reduction process is a mechanical dimensional reduction process. As those skilled in the art know, a mechanical dimensional reduction process will destroy the material under stress applied by mechanical force. The mechanical force can be selected from one or more of tensile stress, bending stress, compressive stress, torsional stress, impact stress, and shear stress. Preferably, the mechanical force is one or more of compressive stress, impact stress, and shear stress.

[0117] The inventors have discovered that the method of mechanically reducing dimensions using a high-speed rotating blade is particularly effective. In this type of processing, it is understood that the mechanical force primarily consists of the impact force generated by the collision between the rotating blade and the microbial cellulose, and the shear force generated due to the difference in medium velocity. Those skilled in the art will understand that any device capable of applying mechanical force to the microbial cellulose is suitable. Preferably, this device is a mixer.

[0118] In one embodiment of the invention, the method further includes contacting the plant growth medium with water. Preferably, the mixture of plant growth medium and water is stirred.

[0119] Example 1

[0120] A series of experiments were conducted to test the effects of hydrophilic polymer molecular weight and concentration on the dehydration of wet microbial cellulose. Fourteen (14) CMC solutions were prepared using low molecular weight CMC (90,000), medium molecular weight CMC (250,000), and high molecular weight CMC (700,000). The CMC concentration in the solutions ranged from 0.5% to 10%, depending on the molecular weight of the CMC solution. In each test, approximately 70–80 g (unmixed) of the original wet microbial cellulose film was weighed and immersed in a beaker containing 500 g of CMC solution. The film was kept in the CMC solution and left at room temperature. After 24 hours, the film was removed from the solution and excess CMC solution was scraped off. The resulting material was then dried. The results are shown in Table 1.

[0121] Table 1: Comparison of individual CMC types (at different CMC percentages)

[0122] The CMC content was calculated using a wet microbial cellulose untreated sample treated in 500g of water. The sample was then dried and weighed to determine the weight of the dried MC compared to the wet biofilm weight. This percentage was then used to calculate the dry weight of the biofilm without CMC, which could be subtracted from the dry weight to obtain the estimated CMC percentage.

[0123] Dehydration was measured by weighing the wet biofilm before treatment and then, 24 hours later, after removing excess CMC solution, taking into account the weight of the present CMC and microbial cellulose, and calculating the actual percentage of water removed.

[0124] The expansion was measured by immersing approximately 1 gram of dried material in 500 ml of water for 72 hours (constant weight was checked to ensure saturation and removal of CMC from the microbial cellulose). The expansion ratio was then calculated by dividing the wet weight of the obtained microbial cellulose by the weight of the microbial cellulose in the dried material (i.e., the total dry weight minus the weight of CMC in the material).

[0125] Table 1 illustrates the differences between CMCs with different molecular weights. Low molecular weight CMCs have the lowest dehydration effect but the highest CMC absorption / content in the resulting material. High molecular weight CMCs have the highest dehydration effect but the lowest CMC absorption / content in the resulting material. Medium molecular weight CMCs produce a similar dehydration effect to high molecular weight CMCs, but with a higher CMC absorption rate (lower than low molecular weight CMCs). Therefore, CMC types can be selected for drying alone, expansion preservation alone, or both expansion preservation and drying.

[0126] Example 2

[0127] A series of experiments were conducted to test the effects of different molecular weight combinations of hydrophilic polymers on the dehydration of wet microbial cellulose. Five (5) CMC solutions were prepared by mixing different amounts of low molecular weight CMC and high molecular weight CMC. In each test, approximately 70–80 g (unmixed) of the original wet microbial cellulose biofilm was weighed and immersed in a beaker containing 500 g of each CMC solution. The biofilm was kept in the CMC solution and placed at room temperature. After 24 hours, the biofilm was removed from the solution and excess CMC solution was scraped off. The resulting material was then dried. The results are shown in Table 2.

[0128] Table 2 - Mixed High Molecular Weight (HM) w CMC and low molecular weight (LM) w CMC

[0129] Table 2 shows that using mixtures of CMC types is beneficial for combining dehydration effects and high swelling preservation. Theoretically, high molecular weight CMCs produce a dehydration effect, while low molecular weight CMCs produce better CMC absorption / swelling preservation. The results suggest that other mixtures of hydrophilic polymers with different molecular weights may also be beneficial.

[0130] Example 3

[0131] A series of tests were conducted to determine the effect of the thickness of wet microbial cellulose on the dehydration rate of high molecular weight CMC solution. Wet microbial cellulose samples with different initial thicknesses were treated in 3% CMC solution. Each sample was a circle with a diameter of 10 cm. Figure 1 The difference in sample thickness over drying time is shown.

[0132] These results indicate that a significant portion of the water is removed after 24 hours, and a drying time of 48–72 hours is sufficient to remove most of the water. It can be noted that twice the thickness does not require twice the drying time.

[0133] Example 4

[0134] A series of tests were conducted to determine the effect of temperature on the contact between wet microbial cellulose and high molecular weight CMC solution on the dehydrated and dried microbial cellulose. The experimental results are shown in Table 3.

[0135] Table 3: Heat Treatment

[0136] Oven treatment significantly increased the rate at which microbial cellulose absorbed CMC. This is presumably partly due to the viscosity reduction caused by increased temperature. Untreated material showed significant expansion loss without the CMC drying process.

[0137] Example 5

[0138] A series of experiments were conducted to determine the effect of CMC concentration in dried microbial cellulose (MC) on seed germination. 0.5 g of dried microbial cellulose, dried CMC-treated microbial cellulose, and CMC (high molecular weight) samples were treated with 50 ml of water. The samples were placed in seed germination trays (with holes at the bottom to allow excess water to drain), treated with approximately 50 mustard seeds, and monitored for one week. The results are shown in Table 4.

[0139] Table 4: Germination results of seeds with different CMC contents

[0140] Example 6

[0141] A series of tests were conducted to determine the effect of the particle size of dried microbial cellulose on the water-holding capacity of the rehydrated material. A dried sample was prepared by contacting the wet microbial cellulose with a CMC solution containing 2.3% high molecular weight CMC and 3% low molecular weight CMC for 24 hours. The dehydrated material was removed from the solution and dried at 70°C. The dried material was mixed in a NutriBullet Rx mixer for 3 minutes. The resulting powder was sieved (following AS 1289.3.6.1), collecting particles of 106, 212, 355, 425, and 500 µm. A coconut husk fiber sample was also included for comparison.

[0142] 0.5 g of dried material for each particle size range was added to 50 ml of water and shaken for 2 minutes until gel formation and complete water integration. A coconut husk fiber sample was also included for comparison. The resulting mixture was placed on a pre-weighed tray with drainage holes and drained at room temperature and pressure. Weighing was performed at different intervals to obtain the water retention over time. Results are as follows: Figure 2 As shown.

[0143] The results showed that particle size had a significant impact on water retention. Smaller particles had higher water retention than larger particles. It is also noteworthy that coconut husk fiber of the same weight as treated microbial cellulose (0.5 g) completely lost moisture within 24 hours, while the treated bio-cellulose retained more than 25% moisture after 120 hours.

[0144] Example 7

[0145] The dried microbial cellulose of the present invention was compared with other commercially available plant growth media containing coconut shell fiber. The microbial cellulose was treated with a 3% high molecular weight CMC solution at 70°C for 96 hours, and then dried at 70°C. Its particle size was then reduced and passed through a 1 mm sieve. Each coconut shell particle weighed 3.9–4.1 g (average 4 g) and had a diameter of 3 cm × a thickness of 1.2 cm upon drying (8.5 cubic centimeters per particle). The particles were broken up and crushed to allow free expansion. This test involved determining the fill size after rehydration to be 6 × 6 × 2 cm (length × width × height) or 72 cm. 3 The dry volume of each material required for the seed germination tray portion. The results are shown in Table 5.

[0146] Table 5: Comparison of CMC-MC and coconut shell to produce 72cm 3 Seed germination medium

[0147] The results showed that to achieve the same wet volume as coconut shell material, significantly less volume (87% reduction in volume) and weight (90% reduction in weight) of dried microbial cellulose is required.

[0148] Comparative example

[0149] CMC has been used in the prior art as a means of preventing keratinization during the drying of microbial cellulose pulp. This pulp comprises wet microbial cellulose that has undergone pulverization. A test was conducted to determine that contact between microbial cellulose (MC) pulp and a CMC solution would result in the removal of moisture from the pulp. 2% MC pulp was mixed with 2% high molecular weight CMC solution in a 1:1 ratio and left to stand overnight at room temperature. The CMC and MC mixture formed a homogeneous gel, and no signs of dehydration were observed. It was further noted that the material produced by treating MC pulp with a CMC solution was more difficult to dehydrate than the untreated pulp. This was demonstrated by attempting to dry CMC-treated and untreated MC pulp through a fine mesh sieve; in the fine mesh, water was more readily released from the untreated pulp.

[0150] Those skilled in the art will understand that the invention described herein is susceptible to variations and modifications beyond the specific description. This invention includes all such variations and modifications. The invention also includes all steps, features, formulations, and compounds individually or collectively mentioned or indicated in the specification, as well as any and all combinations or any two or more steps or features.

Claims

1. A method for dehydrating microbial cellulose, the method comprising: Contact the wet microbial cellulose material with a hydrophilic polymer solution; The contact between the wet microbial cellulose material and the hydrophilic polymer solution is maintained for a treatment period of time to remove at least some of the water from the wet microbial cellulose material; and Dehydrated microbial cellulose is extracted from a hydrophilic polymer solution.

2. The method of claim 1, wherein the wet microbial cellulose is provided as a microbial cellulose film or a fragment thereof.

3. The method according to claim 1 or claim 2, wherein the microbial cellulose content of the wet microbial cellulose material is less than 5% by weight.

4. The method according to any of the preceding claims, wherein the hydrophilic polymer solution comprises one or more polysaccharides.

5. The method according to claim 4, wherein the polysaccharide is selected from one or more of guar gum, gum arabic, 1-carrageenan, carboxymethyl cellulose (CMC), and alginate.

6. The method according to any of the preceding claims, wherein the hydrophilic polymer solution is a CMC solution.

7. The method according to any one of the preceding claims, wherein the concentration of the hydrophilic polymer solution is less than 20%.

8. The method according to any of the preceding claims, wherein the ratio of the hydrophilic polymer solution to the wet microbial cellulose is at least 0.5:

1.

9. The method according to any of the preceding claims, wherein the processing time is at least 6 hours.

10. The method according to any of the preceding claims, wherein the contact between the wet microbial cellulose material and the hydrophilic polymer solution is carried out at an elevated temperature.

11. The method according to any of the preceding claims, wherein the weight of the dehydrated microbial cellulose is less than 40% of the weight of the wet microbial cellulose material.

12. The method according to any one of the preceding claims, wherein the method further comprises the step of: Dehydrated microbial cellulose is dried to produce dried microbial cellulose material.

13. A dehydrated microbial cellulose material, the dehydrated microbial cellulose material comprising: Microbial cellulose, 25-95% by dry weight; and Hydrophilic polymers, 5-75% by dry weight.

14. The dehydrated microbial cellulose material of claim 13, wherein the hydrophilic polymer comprises one or more polysaccharides.

15. The dehydrated microbial cellulose material according to claim 14, wherein the polysaccharide is selected from one or more of guar gum, gum arabic, I-carrageenan, carboxymethyl cellulose (CMC) and alginate.

16. The dehydrated microbial cellulose material according to any one of claims 13 to 15, wherein the hydrophilic polymer is CMC.

17. The dehydrated microbial cellulose material according to any one of claims 13 to 16, wherein the hydrophilic polymer content is 5-60% on a dry weight basis.

18. A method for producing a plant growth medium, the method comprising: The wet microbial cellulose material is subjected to the dehydration method of any one of claims 1 to 11 to obtain a plant growth medium.

19. The method of claim 18, wherein the method further comprises the step of: Dehydrated microbial cellulose is dried to obtain a dry plant growth medium.

20. The method of claim 19, wherein the dried plant growth medium is subjected to size reduction processing.

21. The method of claim 20, wherein the size reduction process reduces the particle size of the dried plant growth medium to less than 1000 μm with a D90.

22. A plant growth medium comprising: Microbial cellulose, 25-75% by dry weight; and Hydrophilic polymers, 25-75% by dry weight.

23. The plant growth medium of claim 22, wherein the hydrophilic polymer comprises one or more polysaccharides.

24. The plant growth medium according to claim 23, wherein the polysaccharide is selected from one or more of guar gum, gum arabic, 1-carrageenan, carboxymethyl cellulose (CMC), and alginate.

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