WO2024251766A1

WO2024251766A1 - Microbial cellulose-based paper

Info

Publication number: WO2024251766A1
Application number: PCT/EP2024/065391
Authority: WO
Inventors: Patrycja KUCHARCZYK; Adam Aleksander KORCZAK
Original assignee: Treeless Pack GmbH
Current assignee: Treeless Pack GmbH
Priority date: 2023-06-07
Filing date: 2024-06-05
Publication date: 2024-12-12
Anticipated expiration: 2025-12-07

Abstract

The present invention relates to the field of paper and paper production and relates to paper based on microbial cellulose having properties similar to paper made from vegetal cellulose. It also relates to a process for producing such paper. The paper of the invention can advantageously be used in the same way as paper based on vegetal cellulose, in particular as a packaging material or as a writing/printing support.

Description

Title of Invention: Microbial cellulose-based paper

Technical Field

[0001] The present invention relates to the field of paper and paper production and relates to paper based on microbial cellulose having properties similar to paper made from vegetal cellulose. It also relates to a process for producing such paper. The paper of the invention can advantageously be used in the same way as paper based on vegetal cellulose, in particular as a packaging material or as a writing/printing support.

Background Art

[0002] Paper, paper derivatives and cardboard are widely used for a variety of purposes, namely as packaging materials or for writing or printing. Paper is usually produced from vegetal cellulose, mainly sourced from wood. However, intensive use of wood is a significant ecological threat, as the reduction of the earth surface covered with wood is likely to contribute to global warming. It would therefore be advantageous to develop alternatives to paper based on vegetal cellulose.

[0003] It is known from the prior art to produce cellulose from microbial culture. Microbial cellulose is however mostly disclosed for use in the manufacture of films that can serve as alternatives to plastic. Such films have properties very different from those of paper.

[0004] Only few documents have disclosed paper alternatives based on microbial cellulose. For example, US6329192B1 discloses reticulated cellulose produced by microorganism, which can form a paper-like sheet. The advantageous properties of the obtained cellulose in view of paper manufacturing are conferred by the specific reticulation generated by culturing the bacteria under agitated conditions.

[0005] CN112522345A discloses a process for producing a cellulose membrane that can be used in the paper, textile, cosmetic or medical field. This document however does not address the question of adjusting the properties of the membrane in view of paper making. [0006] CN111471199A discloses a food packaging film made of microbial cellulose produced in agitated cultures and having a tensile strength higher than conventional packaging paper.

[0007] There is a need to adjust the properties of microbial cellulose to match those of paper made of vegetal cellulose. It is further desired to obtain such properties while keeping the manufacturing process simple and while limiting energy consumption to the maximum.

Summary of Invention

[0008] In a first aspect, the present invention relates to microbial cellulose-based paper comprising microbial cellulose and an inorganic filler in a dry weight ratio of 5:1 to 1 :13.

[0009] In a particular aspect, the microbial cellulose-based paper is in the form of flat sheets of paper and the microbial cellulose to inorganic filler dry weight ratio is of 3:1 to 1 :3, preferably of 2:1 to 1 :2.

[0010] In another particular aspect, the microbial cellulose-based paper is in the form of a molded paper material and the microbial cellulose to inorganic filler dry weight ratio is of 1 :2 to 1 :12.

[0011] In a second aspect, the present invention relates to a process for producing microbial cellulose-based paper comprising the steps of: a) Providing wet microbial cellulose, wherein such wet microbial cellulose is either sourced in wet form or is obtained by blending microbial cellulose in dry form with water until a homogeneous mixture is obtained; b) Adding an inorganic filler to the wet microbial cellulose provided in step a) in an amount such that the microbial cellulose to inorganic filler are present in a dry weight ratio of 5:1 to 1 :13 and blend until a homogeneous mixture is obtained; and c) Shaping and drying the mixture obtained in the end of step b) to obtain paper.

[0012] In a third aspect, the present invention relates to a microbial cellulose-based paper obtained or obtainable by the process of the invention.

[0013] In a fourth aspect, the present invention provides a packaging material comprising or consisting of a microbial cellulose-based paper of the invention. [0014] In a fifth aspect, the present invention relates to the use of a microbial cellulose-based paper of the present invention as a packaging material.

Brief description of the Figures

[0015] [Fig. 1] provides a schematic representation of the general process according to the invention.

[0016] [Fig. 2] shows a flat sheet of microbial cellulose-based paper of the invention (A) and a folded packaging material obtained from such flat sheet of microbial cellulose-based paper (B) as obtained in Example 1.5.

[0017] [Fig. 3] shows a packaging material molded from a wetted flat sheet of microbial cellulose-based paper of the invention, as obtained in Example 1.7.

[0018] [Fig. 4] shows a molded microbial cellulose-based paper packaging material according to the invention, as obtained in Example 1.8.

Detailed Description

Microbial cellulose-based paper

[0019] The microbial cellulose-based paper of the present invention comprises microbial cellulose and an inorganic filler. For the sake of the present invention, the term "paper" designates herein paper, as well as paper derivatives, such as cardboard.

[0020] Microbial cellulose is characterized by cellulose fibers that are shorter than fibres of vegetal cellulose. Microbial cellulose is preferably in the form of nanofibers, preferably having a diameter in the range of 20 to 100 nanometers. Microbial cellulose nano-fibers have different properties compared to vegetal cellulose fibers. As a consequence, materials, such as paper, based on microbial cellulose have to be specifically formulated to achieve properties close to those of materials based on vegetal cellulose. In particular, the amounts of filler need to be adjusted, in order to obtain a given paper quality. For the same paper quality, amounts of filler differ depending on the type of cellulose used (microbial or vegetal). Therefore, the know-how developed in the traditional paper industry based on vegetal cellulose cannot simply be applied as such to produce paper from microbial cellulose.

[0021] The microbial cellulose can be any cellulose from microbial origin. In a particular aspect, the microbial cellulose is bacterial cellulose, i.e. cellulose produced by the culture of at least one bacterial strain. Methods for producing such microbial or bacterial cellulose are known to the person skilled in the art.

[0022] In a preferred aspect, the at least one bacterial strain is selected from at least one Acetobacter strain, at least one Gluconobacter strain, at least one Komagataeibacter strain, at least one Rhizobium strain, at least one Sarcina strain, at least one Agrobacterium strain, at least one Pseudomonas strain, at least one Achrombacter strain, at least one Alcaligenes strain, at least one Aerobacter strain, at least one Azotobacter strain and combinations thereof. Preferably the at least one bacterial strain is of a species selected from Acetobacter aceti, susp. xylinum, Acetobacter pasteurianus, Gluconobacter xylinus, Gluconobacter oxydans, Gluconobacter europaeus, Gluconobacter intermedius, Gluconobacter hansenii, Komagataeibacter xylinus, Komogataeibacter rhaeticus or mixtures thereof.

Preferably, the at least one bacterial strain is selected from a genus selected from at least one Acetobacter strain, at least one Gluconobacter strain, at least one Komagataeibacter strain and combinations thereof. More preferably, the bacterial cellulose is produced by a culture of a mixture of strains comprising at least one Acetobacter strain, at least one Gluconobacter strain and at least one Komagataeibacter strain, as described above.

[0023] In a preferred aspect, the microbial cellulose is produced by a stationary (i.e. non-agitated) fermentation process. Microbial cellulose obtained from a stationary culture is characterized by less cross-linked cellulose fibres, compared to cellulose obtained from an agitated culture. Such structure of the fibres is particularly adapted to the present invention, and in particular to the specific amounts of fillers recited therein.

[0024] Microbial cellulose is advantageous over cellulose obtained from vegetal sources, because its production does not require cutting trees, which are known to have beneficial effects on climate. Furthermore, the production of microbial cellulose requires about 30 to about 500 times less land surface than production of vegetal cellulose.

[0025] Microbial cellulose is further characterized by all the beneficial properties of vegetal cellulose. Importantly, microbial cellulose can be recycled in usual paper recycling facilities, in the same way as any paper based on vegetal cellulose. [0026] The inorganic filler can be any particulate inorganic water-insoluble substance that can be used as a filler in the paper industry. In a preferred aspect, the filler is at least one mineral substance selected from the group consisting of water-insoluble metal oxides, metal hydroxides, metal sulfates, metal carbonates, metal silicates and combinations thereof, such as aluminium silicates, aluminium oxides, aluminium hydroxydes, magnesium oxides, magnesium carbonate (magnesite), titanium oxides, barium sulfate (baryte), calcium carbonate, calcium silicate (wollastonite), and combinations thereof.

[0027] In a preferred aspect, the mineral substance is an aluminium silicate, optionally hydrated and optionally comprising one or more additional metal cation(s), such as for example Na⁺, K⁺, Ca²⁺, Mg²⁺. Preferably the aluminium silicate is a silicate of an aluminium oxide or a silicate of an aluminium carbonate. In a preferred aspect, the aluminium silicate is a kaolinite clay, a pyrophyllite clay, mica or bentonite, preferably a kaolinite clay, a pyrophyllite clay or mica, more preferably a kaolinite clay or a pyrophyllite clay.

[0028] In a specific aspect, the inorganic mineral substance is a salt selected from CaCOs, CaSiOs, AICO3'2SiO2, Al2O3'2SiO2, Al2O3'4SiO2, TiO2, MgCOs, Mg3Si40io(OH)2, CaSCU, BaSCU, and mixtures thereof, wherein such salts can optionally be in hydrated form. CaCOs is preferably provided in the form of ground limestone, ground chalk and/or precipitated calcium carbonate (PCC). AICO3'2SiO2 and Al2O3'2SiO2 are preferably provided in the form of a kaolinite clay or precipitated aluminium silicate. A^Os ^SiCh is preferably provided in the form of pyrophyllite clay. TiCh can be provided in the rutile or in the anatase form.

Mg3Si4O (OH)2 is preferably provided in the form of talc. CaSO4'2H2O is preferably provided in the form of gypsum. In a preferred aspect, the inorganic substance is selected from the group consisting of AICO3'2SiO2, Al2O3'2SiO2 or a mixture thereof, optionally in hydrated form, more preferably AICO3'2SiO2'2H2O, and/or Al2O3'2SiO2'2H2O (hydrous kaolinite).

[0029] In a preferred aspect, the inorganic filler particles are characterized by a mean particle size of 0.1 to 10pm, preferably 0.1 to 5 pm, more preferably 0.1 to 4 pm, the mean particle size being defined as the mean equivalent diameter, by weight, as measured by light scattering. [0030] The microbial cellulose and the inorganic filler are preferably present in a cellulose to inorganic filler dry weight ratio of 5: 1 to 1 : 13. Such dry weight ratio confers to the paper improved mechanical properties. Such properties can be adapted to the desired application by adjusting the cellulose to inorganic filler dry weight ratio. In particular, the flexibility of the paper is increased with low amounts of filler, while high amounts of filler are advantageous for the material to keep it shape, for example after molding. The optimal amount of filler shall be fine-tuned to balance these two opposite properties.

[0031 ] Microbial cellulose to inorganic filler dry weight ratio is of 5: 1 to 1 : 13, preferably for flat sheets of paper the dry weight ratio is preferably of 3:1 to 1 :3, more preferably 2:1 to 1 :2. For molded paper packaging materials the dry weight ratio is preferably of 1 :2 to 1 : 12, more preferably of 1 :5 to 1 : 12, even more preferably 1 :6 to 1 : 12, even more preferably 1 :7 to 1 :11 , most preferably 1 :8 to 1 :10, for example, 1 :9. Such dry weight ratios are most appropriate for the manufacture of molded paper packaging materials. Such packaging materials can advantageously be shaped in any kind of form by molding, while being strong enough to keep their shape. Thus, they form reliable packaging materials for a wide variety of applications. The composition of the paper is advantageous, as it can be used even for the packaging of food products.

[0032] The terms "dry weight ratio" refer to the ratio by weight taking into account only the solids content of the different elements. Thus the filler to cellulose dry weight ratio is calculated based on the filler solid content and the cellulose solid content. Thus, as the cellulose is provided in wet form, the amount of filler to be incorporated shall be adapted to the solid content of the wet microbial cellulose. For example, when using wet microbial cellulose in the form of a paste having a microbial cellulose content of 3wt%, an amount of 15 kg of filler shall be added to achieve a 1 :5 cellulose to filler dry weight ratio when admixed with 100 kg of paste (which comprises 3 kg solid cellulose and 97kg water...

[0033] In a particular aspect, the microbial cellulose-based paper further comprises one or more additives. One example of such an additive is a resin adhesive. Such resin adhesive is advantageous in that it in special applications also by adding adhesives, e.g. resin adhesive). The resin adhesive is preferably present in an inorganic filler to adhesive weight ratio of 2.1 to 4: 1 , preferably 1 :1 to 2: 1 . The presence of the resin adhesive is advantageous in that it makes the paper more resistant to moisture because the absorption of moisture by the paper is reduced. This is in particular very useful to pack water-containing materials, such as humid food.

Process

[0034] In a second aspect, the present invention relates to a process for producing a paper from microbial cellulose comprising:

1 ) Providing wet microbial cellulose, wherein such wet microbial cellulose is either sourced in wet form or is obtained by blending microbial cellulose in dry form with water until a homogeneous mixture is obtained;

2) Adding an inorganic filler to the microbial cellulose paste provided in step a) in an amount such that the microbial cellulose to inorganic filler are present in a dry weight ratio of 5:1 to 1 :13 and blending until a homogeneous mixture is obtained;

[0035] Shaping and drying the mixture obtained in the end of step b) to obtain paper.

[0036] In the first step, wet microbial cellulose is provided. Microbial cellulose is as disclosed above in the paper section. Microbial cellulose can be purchased from suppliers. Alternatively, the microbial cellulose can advantageously be produced, optionally dried and then used in the present process, in the same facilities. The microbial cellulose production is particularly advantageous in that it uses reduced space.

[0037] Wet microbial cellulose can either be directly sourced in the form of wet microbial cellulose or, alternatively, the wet microbial cellulose can be formed in- situ at the beginning of the process by blending dry microbial cellulose with water, until a homogeneous mixture is obtained, such as to form wet microbial cellulose.

[0038] In a preferred aspect, the wet microbial cellulose is in the form of a paste. In a preferred aspect, the wet microbial cellulose, preferably the paste comprises up to 5wt% microbial cellulose, preferably up to 4wt% microbial cellulose, based on the total weight of the paste, such as 0.5 to 5wt%, preferably 1 to 4.5wt%, preferably 1 .5 to 4wt%, more preferably 2 to 4wt%, even more preferably 2.5 to 3.5wt%, most preferably 3wt% microbial cellulose, based on the total weight of the wet microbial cellulose. [0039] Sourcing the wet microbial cellulose directly is advantageous over blending dry microbial cellulose with water, as it avoids a step of drying the cellulose followed by the step of preparing the wet microbial cellulose by blending with water in the beginning of the process of the invention, thus making the overall process more efficient. This is even more true because blending dry microbial cellulose with water requires high-speed blending, whereas mild mixing is sufficient to achieve a homogeneous mixture of the wet microbial cellulose with the filler. Sourcing wet microbial cellulose directly is further advantageous over obtaining dry microbial cellulose and blending (reconstituting) with water in the beginning of the process, in that it simplifies the blending of the cellulose with the filler and the shaping step, and in that a more homogeneous paper is obtained, having improved quality.

[0040] In a particular aspect of the invention, the wet microbial cellulose is provided in step a) by producing the microbial cellulose as described below. The harvested microbial cellulose can either be fully dried, so that the said dry cellulose needs to be blended with water, or partially dried to obtain the desired microbial cellulose concentration. In the latter case, the partially dried microbial cellulose can be directly blended with the filler.

[0041] In a preferred aspect, the microbial cellulose is produced by growing at least one cellulose-producing microbial strain in a fermentation medium having an acidic pH, preferably a pH of 6 or less, comprising water and carbohydrates.

[0042] The carbohydrates in the fermentation medium are preferably present in an amount of 18 to 120g/L. the carbohydrates are preferably selected from sucrose, fructose, glucose and mixtures thereof; and

[0043] The target pH of 6 or less, preferably of 3 to 6, more preferably of 4 to 5 can be obtained by adding a weak acid into the medium. In a preferred aspect, the acid has at least one carboxylic group having a pKa below 5, preferably between 3 and 5, more preferably between 4 and 5, optionally with a base forming a buffer with the acid. In a more preferred aspect, the acid is acetic acid or citric acid, more preferably acetic acid. In a most preferred aspect, acetic acid is provided in the form of vinegar. Vinegar is advantageous in that it also comprises carbohydrates that can be used as a carbon source by the microbial strains during fermentation. Apple vinegar is particularly advantageous, because it contains particularly high amounts of sugars.

[0044] An acidic pH of the culture medium is advantageous in that it reduces the growth of molds in the culture.

[0045] The carbon source can be provided in the form of pure carbohydrates or of a more complex matrix. Preferably, the carbon source is provided in the form of a juice or extract of a material comprising the desired carbohydrates, such as a juice or extract of a vegetal source, for example fruits, vegetables or grains. Such juice or extract can advantageously be sourced from food leftovers. In such a case, the process is particularly cost effective and environmentally friendly. The amount of carbohydrate mentioned above is the combined amount of carbohydrates from all ingredients present in the medium, including juice, vinegar and/or any other ingredient that contains such sugars, preferably sucrose, fructose and/or glucose.

[0046] In a preferred aspect, the carbon source comprises fructose, because fructose is the optimal sugar for the growth of the bacterial stain involved in microbial cellulose production.

[0047] Optionally, the fermentation medium can comprise a nitrogen source, such as a yeast extract and/or a peptone. It can also comprise salts and micronutrients. Such additional ingredients and their use are well-known to the person skilled in the art of fermentation. Using vegetal left-overs as the source of carbon is particularly advantageous, because with such carbon source it is not useful to add any such additional salt or nutrients.

[0048] In preferred aspect of the process, the fermentation medium comprises tannin. This advantageously improves the quality and performance characteristics of the microbial cellulose grown in such medium. A predetermined amount of tannin, preferably ranging from 0.1 to 2%, more preferably from 0.1 to 1 % by volume, based on the total volume of the medium, is incorporated at the initiation of the fermentation process. The addition of tannin beneficially modifies the cellulose microstructure, which enhances the tensile strength and the water resistance of the cellulose, making it more suitable for high-quality paper production.

[0049] The medium is introduced into a sterile or non-sterile open container and the temperature of the medium is adjusted to a temperature in the range of 15 to 37°C and a starter culture comprising at least one bacterial strain and optionally one or more fungal strain is added to the medium. The at least one bacterial strain is preferably at least one bacterial strain of a genus selected from Acetobacter, Gluconobacter, Komagataeibacter, Rhizobium, Sarcina, Agrobacterium, Pseudomonas, Achrombacter, Alcaligenes, Aerobacter, Azotobacter and combinations thereof and preferably of a species selected from Acetobacter aceti, susp. xylinum, Acetobacter pasteurianus, Gluconobacter xylinus, Gluconobacter oxydans, Gluconobacter europaeus, Gluconobacter intermedius, Gluconobacter hansenii, Komagataeibacter xylinus, Komogataeibacter rhaeticus. Preferably, the bacterial strain is selected from a genus selected from Acetobacter, Gluconobacter, Komagataeibacter and combinations thereof. More preferably, the starter culture comprises at least one Acetobacter strain, at least one Gluconobacter strain and at least one Komagataeibacter strain, as described above.

[0050] The fungal strain is preferably a yeast strain. Preferably the yeast strain is selected from Saccharomyces, Hanseniaspora, Brettanomyces, Zygosaccharomyces, Kloeckera and mixtures thereof. Preferably it is selected from Saccharomyces, Zygosaccharomyces and mixtures thereof. In a preferred aspect, the yeast strain is selected from Hanseniaspora uvarum, Brettanomyces bruxellensis, Zygosaccharomyces bailii, Kloeckera lindneri. The fungal strain, preferably the yeast strain, is particularly advantageous in that it works in symbiosis with the bacteria. The fungi break down disaccharides present in the culture medium into simple sugars, which can in turn be metabolized by bacteria. In return, the bacteriae modulate the pH of the environment, protecting the medium from other contaminants, to the benefit of the fungal strain.

[0051 ] One example of a starter culture suitable for the purpose of the present invention is a symbiotic culture of bacteria and yeast (SCOBY), such as used for the preparation of Kombucha. Such starter culture can for example be purchased from Stoecklin Aprovital, Basel, Switzerland.

[0052] The starter culture is preferably present in the medium in a concentration of 1 .5 to 3 wt%, preferably 1 .6 to 2.8 wt%, more preferably 1.7 to 2.6 wt%, even more preferably 1 .8 to 2.5 wt%, most preferably 1 .9 to 2.4 wt%. [0053] The present process does not require any specific device and the bacteria can be grown in any kind of open container, such as a box, for example a plastic or glass box with an opening allowing air to enter. This is advantageous as no complex production facility is required. Preferred containers for the microbial production are flat containers having a large surface and a minimum height. Indeed, in a static culture, the cellulose accumulates in the form of sheets at the surface of the growth medium. Growing the starter culture in a flat container having a large surface area allows to obtain large cellulose sheets. Reduced height of the container is also advantageous, as it makes it possible to arrange more containers vertically in a given volume of the production area.

[0054] Optionally, after addition of the starter culture, the container opening is covered with a material that that is permeable to air, in order to protect the culture from contamination while allowing air to enter the container. Such material can for example be thin fleece or lignin.

[0055] The bacteria are preferably grown at a temperature of 15 to 37°C, preferably 22-26°C, more preferably 20-26°C for 10 to 30, preferably 10 to 20, more preferably 12 to 20 days. In a preferred aspect, the culture is performed under stationary (i.e. non-agitated) conditions. Under such conditions, a cellulose layer forms at the surface of the culture medium. In a preferred aspect, the fermentation is performed under low humidity conditions, preferably under conditions of relative humidity of 30 to 65%, preferably 35-50%, more preferably 35 to 45%. Such low levels of humidity help to prevent additional contamination and mold growth of the cultures. In open cultures, high air humidity causes water to condense into the medium, making it harder to control the conditions and concentration of substrates.

[0056] In a preferred aspect, the growth of the bacteria is performed in multiple containers in parallel. More preferably, the containers are arranged in the form of a vertical farm, wherein several containers are arranged on the top of each other, with space between the containers, for example on a vertical shelf. This arrangement is allowed, in particular because the growth of the bacteria does not require agitation and the containers can simply be left to stand for the whole duration of the growth. This production setup is particularly advantageous to save space and optimizes the benefit of using microbial cellulose rather than vegetal cellulose, in terms of land use reduction. [0057] After growth, cellulose is harvested, preferably by collecting the cellulose sheet at the surface of the growth medium. Preferably, the cellulose is washed, more preferably with water.

[0058] The cellulose is then dried wholly or partially, preferably it is dried by letting the cellulose to dry in air, for example by hanging the cellulose sheets in a room at low relative humidity. The lower the relative humidity in the drying place, the quicker the drying. Preferably, the cellulose is air-dried cellulose in one stable sheet, i.e. in the form of the original sheet collected from the growth medium, which is not tom or rebound.

[0059] Wet microbial cellulose can be sourced by avoiding complete drying of the cellulose at the end of the cellulose production process. In such case, only partial draying is carried out and drying is continued until a desired cellulose level is achieved. For the purpose of the present invention, the drying is preferably stopped when reaching a cellulose content of at least 0.5wt%, preferably at least 1wt%, preferably at least 1 ,5wt%, more preferably at least 2, even more preferably at least 2.5wt%, most preferably at least 3wt%, based on the total weight of the partially dried microbial cellulose.

[0060] When the microbial cellulose is provided in the form of dry microbial cellulose, the dry cellulose is blended with water. In a preferred aspect, the microbial cellulose sheets are cut into smaller pieces before being blended with water. This makes the bending process easier and makes it possible to obtain a homogeneous blend of microbial cellulose water without using high shear forces. This is advantageous in that it avoids heating the microbial cellulose and water mixture during the blending process. For the same reason, the microbial cellulose and water are preferably blended intermittently, such as to avoid excessive heating thus avoiding excessive heating.

[0061] In a particular aspect, water is added to cellulose in a cellulose-to-water weight ratio of 1 :33 to 1 :800, preferably 1 : 100 to 1 :800 (such as 1 : 100 to 1 :600, 1 : 100 to 1 :500, 1 : 100 to 1 :400 or 1 : 100 to 1 :300) preferably 1 :300 to 1 :800, more preferably 1 :200 to 1 :300, even more preferably 1 :100 to 1 :200, most preferably 1 :33 to 1 :100. [0062] Preferably, the microbial cellulose and water are blended at 17000 to 35000 rpm, preferably 25000 to 35000 rpm for 1 to 2 minutes, followed by a break. This blending process is repeated until the blend is homogeneous. Such intermittent blending is advantageous in that it avoids overheating of the microbial cellulose and therefore preserves the quality of the cellulose. Microbial cellulose for example exhibits unique rheological properties, including high viscosity and shear thinning behavior. Overheating can alter these properties, resulting in changes in viscosity and flow behavior.

[0063] In the second step of the process of the invention, an inorganic filler, optionally with one or more additive(s) such as a resin adhesive is added to the mixture of microbial cellulose and water. The microbial cellulose to inorganic filler dry weight ratio is of 5: 1 to 1 : 13. The mixture is blended such as to obtain a homogeneous mixture.

[0064] In the third step of the process of the invention, the mixture obtained in the end of the second step is shaped to form the desired paper material. The rigidity of the material can be fine-tuned by varying the thickness of the obtained material.

[0065] The composition may be formed by a traditional papermaking method, i.e. a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down. Water is removed from this mat of fibers by pressing and drying to make paper. Membranes, e.g. low porosity nylon membranes, preferably 35-80 pm, preferably 35-45 pm, are used as a sieve.

[0066] The obtained paper can then be pressed, preferably with a pressure of 1500 to 2500 kg, more preferably 1750 to 2250 kg. for example about 2000 kg, to form a flat sheet of paper that can be used for writing or as wrapping paper, for example. Such sheets of paper can then be folded as desired, or wetted and formed into any desired shape by molding.

[0067] In a particular aspect, the microbial cellulose-based paper is formed as a flat sheet optionally folded or wetted and molded and the cellulose to filler dry weight ratio is of 3:1 to 1 :3, more preferably 2:1 to 1 :2.

[0068] Alternatively, and preferably, the homogeneous mixture, optionally drained, can be molded to a desired shape instead of being pressed to a flat sheet. The thus formed material can advantageously be used as packaging material. Examples of such applications would be paper boxes for diverse uses, namely as a container for food or cosmetics products.

[0069] In a particular aspect, the composition is molded and the microbial cellulose to inorganic filler dry weight ratio is of 1 :2 to 1 : 12, preferably 1 :5 to 1 : 12, more preferably 1 :6 to 1 :12, more preferably 1 :7 to 1 :11 , even more preferably 1 :8 to 1 :10, most preferably 1 :9. Such dry weight ratios are particularly advantageous as they makes it possible to obtain a material that retains its shape in a suitable way while remaining sufficiently flexible.

[0070] The microbial cellulose-based paper obtained by the process of the present invention, and all components of such paper are as described above in the section related to the microbial cellulose-based paper itself.

Packaging

[0071] The present invention also relates to a packaging material comprising or consisting of a microbial cellulose-based paper of the present invention, as described above. The microbial cellulose-based paper of the present invention can be used as a packaging material, for example as a folded or molded container, as described above.

[0072] Alternatively, the microbial cellulose-based paper of the present invention can be used as a component in a more complex packaging material comprising additional materials. For example, the microbial cellulose-based paper can be present in a laminated packaging material, in the form of a flat sheet of paper laminated with layers of metal and/or plastic. This is in particular useful for the packaging of liquid products or of products that are sensitive to light and/or oxygen and require a packaging providing particular light and oxygen barrier

[0073] Also, a packaging comprising or consisting of the microbial cellulose-based paper of the invention can be combined with another type of packaging to form a multiple layer of packaging. For example, a bag-in box packaging can be formed of a box made of the microbial cellulose-based paper of the invention, which itself contains a plastic bag or pouch.

[0074] The present invention also relates to the use of a microbial cellulose-based paper according to the present invention as a packaging material. Preferably, it relates to the use of a molded microbial cellulose-based paper material as a packaging material.

Examples

[0075] Example 1 : preparation of microbial cellulose-based paper material according to the invention

Example 1.1 - Cultivation of Acetobacter starter for production

[0076] A growth medium (Medium 1 ) was prepared having the following components, in water:

1 ) Peptone (5 g/l)

2) Yeast extract (5 g/l)

3) Na₂HPO₄ (2.7 g/l)

4) Citric acid (1 .5 g/l)

5) Glucose (20 g/l)

[0077] A second growth medium (Medium 2) was prepared from the following components:

1 ) 62.5 g of dry apple (origin: Mdhl AG) or grapes pomace

2) 800 ml of hot water (100 C).

The pomace in water was filtered to obtain fruit juice with a final sugar concentration of 10 wt%. Such juice was used as Medium 2.

[0078] Pre-cultures of the Acetobacteriacea strain Komagataeibacter xylinus (ATCC- 53524) were prepared by taking cells from -80 °C stocks and growing them in 50 ml tubes with 10 ml of medium 1 or 2 in static conditions at a temperature of 30 °C for 5 days.

Example 1 .2 -Cultivation of microorganisms (Scoby starters) for production

[0079] A cultivation medium (Medium 3) was produced having the following components:

1 ) 62.5 g of dry apple (origin Mdhl AG) or grapes pomace

2) 800 ml of hot water (100 C). The pomace in water was filtered to obtain fruit juice with a final sugar concentration of 10 wt%. Such juice was used as Medium 2.

[0080] A cultivation medium (Medium 4) was produced having the following components, in water:

1 ) Green tea (10 wt%)

2) Sucrose (10wt%)

[0081] A cultivation medium (Medium 5) was produced having the following components, in water:

1 ) Black tea (10 wt%)

2) Sucrose (10wt%)

[0082] A cultivation medium (Medium 6) was produced having the following components, in water:

1 ) Black tea (10 wt%)

2) Tanin (0.5%)

3) Sucrose (10 wt%)

[0083] A volume of 600 ml of medium (at a temperature of 25 C) and 60 g of scoby stater (which is composed of Acetobacter, Gluconobacter and Komagataeibacter and yeast (Saccharomyces and Zygosaccharomyces)', origin: Stoecklin Aprovital, Basel, Switzerland) were placed in a jar and covered with a material that allows air access but protects against additional contamination. The initial pH of the solution was about 4 to 5. After 14 days of cultivation it dropped to 3 to 3.5.

[0084] After 14 days, new starters were collected from the surface of the solution and used for further nanocellulose production procedures.

Example 1 .3 - Cultivation of biomaterial for further production processes

[0085] A medium was prepared (Medium 7), having the following components in water:

1 ) 12 wt% of any one of Medium 2 or Medium 3 or Medium 4 or Medium 5 or

Medium 6 or of a similar medium in the form of a concentrated fruit juice obtained by filtering food leftovers in water or by filtering green or black tea, and having a final sugar concentration of 10 wt%.

2) 6 wt% of apple cider vinegar.

[0086] The pH of the medium was below 5.

[0087] Boxes (ca. 0,35m x 0,35m x 0,1 m) were sterilized with boiled water and 3L of growth medium were poured into each box. An amount of 70g scoby starter or Acetobacteriacea strain Komagataeibacter xylinus (ATCC-53524) starter was added to the growth medium at a temperature of 25°C.

[0088] After 7 days, new starters were collected from the surface of the solution and used for further nanocellulose production procedures.

[0089] The boxes were then covered with thin fleece or lignin and were placed in a vertical farm at 25°C in a room with a 50% relative humidity. The culture was incubated under static conditions and let to grow for 14 days.

[0090] After this time, a sheet of biomaterial appeared on the surface of the culture, which was collected and subjected to the air-drying process.

[0091] Such dried material was subjected to a subsequent process using appropriate formulations and molding.

Example 1 .4 - Preparation of microbial cellulose in wet paste form

[0092] A medium was prepared (Medium 7), having the following components in water:

3) 12 wt% of Medium 2 or Medium 3 or Medium 4 or Medium 5 or Medium 6 or of a similar medium in the form of a concentrated fruit juice obtained by filtering food leftovers in water or by filtering green or black tea, and having a final sugar concentration of 10 wt%.

4) 6 wt% of apple cider vinegar.

[0093] The pH of the medium was below 5.

[0094] Boxes (ca. 0,35m x 0,35m x 0,1 m) were sterilized with boiled water and 3L of growth medium were poured into each box. An amount of 70g scoby starter or Acetobacteriacea strain Komagataeibacter xylinus (ATCC-53524) starter was added to the growth medium at a temperature of 25°C. [0095] After 7 days, new starters were collected from the surface of the solution and used for further nanocellulose production procedures.

[0096] The boxes were then covered with thin fleece or lignin and were placed in a vertical farm at 25°C in a room with a 50% relative humidity. The culture was incubated under static conditions and let to grow for 14 days.

[0097] Immediately after harvesting, the microbial cellulose sheet was treated with a 0.5% hydrogen peroxide solution for 10 minutes to bleach the cellulose, enhancing its whiteness and purity.

[0098] Following the bleaching process, the cellulose was thoroughly washed in clean water to remove any residual hydrogen peroxide and impurities, ensuring the cellulose was clean before further processing.

[0099] The washed microbial cellulose was then placed into a kitchen blender and blended at a speed suitable for achieving a homogeneous paste. Specifically, the blender was set to operate at 25000 revolutions per minute (rpm) for 30 seconds to produce a 3% cellulose paste.

Example 1.5 - Preparation of microbial cellulose-based paper material according to the invention - sheet of paper

[0100] The dry biomaterial was crushed into smaller pieces and blended (at 25,000 rpm) with water in a dry weight ratio of 1 : 100.

[0101 ] To form a flat sheet of paper, the crushed cellulose in water, clay and a resin adhesive were admixed in a cellulose to clay to adhesive weight ratio of 1 :2:2.

[0102] The final formulation was sieved into nylons with a pore size: 75 pm. This allowed for the formation of the shape and getting rid of excess water.

[0103] The resulting mass was transferred to the felt fabric to drain, then pressed using a press with a pressure of 2000 kg to form a patch.

[0104] The patch was then dried at a temperature between 160°C, such as to obtain a flat sheet of paper (see Fig. 2A).

[0105] We were able to demonstrate that this material is suitable for forming into packaging by folding (see Fig. 2B). Example 1.6 - Preparation of microbial cellulose-based paper material according to the invention from 3% microbial cellulose paste - sheet of paper

[0106] A microbial cellulose paste having a microbial cellulose content of 3wt%, based on the total weight of the paste was provided by producing microbial cellulose as described herein and retaining water to form paste having a cellulose content of 3% after harvesting the cellulose. Such microbial cellulose paste was used directly for paper formation. This preparation contains the optimal moisture level necessary for immediate processing, simplifying the production steps.

[0107] To form a flat sheet of paper, the microbial cellulose paste was combined with clay and a resin adhesive in a cellulose to clay to adhesive dry weight ratio of 1 :2:2. The mixture was thoroughly blended to ensure uniform distribution of all components and achieve the desired consistency for high-quality paper.

[0108] The mixture was then sieved through nylon membrane with a pore size of 75 pm to ensure the correct formation of the sheet while allowing for the removal of any superfluous moisture.

[0109] After sieving, the resulting mass was transferred onto felt fabric to drain any remaining excess moisture, then pressed under a pressure of 2000 kg to consolidate the material into a uniform patch.

[0110] This patch was dried at a controlled temperature of 160°C to achieve a durable and flat sheet of paper, suitable for further processing.

[0111] The final paper was tested for its suitability in packaging applications by folding into various shapes, confirming its versatility and strength.

Example 1.7 - Preparation of microbial cellulose-based paper material according to the invention - Press-forming of the humid paper sheet

[0112] A sheet of previously prepared paper described in Example 1 .5 or Example 1 .6 was wetted with water in a weight ratio of 1 : 1 .

[0113] The wet material was placed in a pre-prepared form (made of PLA, made using 3D printing technology). [0114] The form consisting of two layers creates a kind of sandwich in the desired shape.

[0115] After placing the material in the form, it was air-dried at a temperature of about 70 C. The formed packaging is represented on Fig. 3.

Example 1.8 - Preparation of microbial cellulose-based paper material according to the invention - Packaging by molded fiber technology

[0116] The dry biomaterial was crushed into smaller pieces and blended (at 25,000 rpm) with water in a weight ratio of 1 : 100 .

[0117] To form a packaging by molded fiber technology, the crushed biomaterial and clay were mixed in a cellulose to clay dry weight ratio of 1 :2. Everything was blended again at 25,000 rpm for 90 seconds.

[0118] The final formulation was sieved into nylons with a pore size: 65 pm to remove excess water. The resulting thick mass was removed from the filter and was given the desired form.

[0119] To form the final product, the mass was placed on a previously prepared mold (made of PLA using the 3D printing method).

[0120] The mass was evenly distributed over the mold surface.

[0121] It has been subjected to a slow air-drying process at a temperature between 27°C.

[0122] Drying took 32 hours. After this time, the product was completely ready. The resulting packaging material is shown on Fig. 4.

Claims

[Claim 1] A microbial cellulose-based paper comprising microbial cellulose and an inorganic filler in a dry weight ratio of 5:1 to 1 :13.

[Claim 2] A microbial cellulose-based paper according to [Claim 1], wherein the microbial cellulose-based paper is in the form of flat sheets of paper and the microbial cellulose to inorganic filler dry weight ratio is of 3:1 to 1 :3, preferably of 2:1 to 1 :2.

[Claim 3] A microbial cellulose-based paper according to [Claim 1], wherein the microbial cellulose-based paper is in the form of a molded paper material and the microbial cellulose to inorganic filler dry weight ratio is of 1 :2 to 1 :12.

[Claim 4] A microbial cellulose-based paper according to any one of [Claim 1] to [Claim 3], wherein the microbial cellulose-based paper is in the form of nanofibers.

[Claim 5] A microbial cellulose-based paper according to any one of [Claim 1] to [Claim 4], wherein the bacterial cellulose originates from at least one bacterial strain, preferably from at least one bacterial strain selected form the group consisting of at least one Acetobacter strain, at least one Gluconobacter strain, at least one Komagataeibacter strain, at least one Rhizobium strain, at least one Sarcina strain, at least one Agrobacterium strain, at least one Pseudomonas strain, at least one Achrombacter strain, at least one Alcaligenes strain, at least one Aerobacter strain, at least one Azotobacter strain and combinations thereof, preferably from at least one bacterial strain selected from the group consisting of at least one strain of Acetobacter aceti subsp. xylinum, at least one strain of Acetobacter pasteurianus, at least one strain of Gluconobacter xylinus, at least one strain of Gluconobacter oxydans, at least one strain of Gluconobacter europaeus, at least one strain of Gluconobacter intermedius, at least one strain of Gluconobacter hansenii, at least one strain of Komagataeibacter xylinus, at least one strain of Komogataeibacter rhaeticus and mixtures thereof, more preferably selected from the group consisting of at least one Acetobacter strain, at least one Gluconobacter strain, at least one Komagataeibacter strain and combinations thereof, such as a mixture of stains comprising at least one Acetobacter strain, at least one Gluconobacter strain and at least one Komagataeibacter strain.

[Claim 6] A microbial cellulose-based paper according to any one of [Claim 1 ] to [Claim 5], wherein the filler is a particulate inorganic water-insoluble substance, preferably a particulate inorganic water-insoluble substance comprising or consisting in at least one mineral substance selected from the group consisting of water-insoluble metal oxides, metal hydroxides, metal sulfates, metal carbonates, metal silicates and combinations thereof, such as aluminium silicates, aluminium oxides, aluminium hydroxydes, magnesium oxides, magnesium carbonate (magnesite), titanium oxides, barium sulfate (baryte), calcium carbonate, calcium silicate (wollastonite), and combinations thereof, more preferably selected from the group consisting of

- an aluminium silicate, optionally hydrated and optionally comprising one or more additional metal cation(s), such as for example Na⁺, K⁺, Ca²⁺, Mg²⁺,

- a salt selected from CaCOs, CaSiOs, AICO3'2SiO2, Al2O3'2SiO2, Al2O3'4SiO2, TiO2, MgCOs, Mg3Si4O (OH)2, CaSCU, BaSCU, wherein such salts can optionally be in hydrated form; and

- mixture thereof.

[Claim 7] A microbial cellulose-based paper according to any one of [Claim 1 ] to [Claim 6], wherein the inorganic filler particles are characterized by a mean particle size of 0.1 to 10pm, preferably 0.1 to 5 pm, more preferably 0.1 to 4 pm, the mean particle size being defined as the mean equivalent diameter, by weight, as measured by light scattering.

[Claim 8] A microbial cellulose-based paper according to any one of [Claim 1 ] to [Claim 7], further comprising one or more additive, preferably a resin adhesive.

[Claim 9] A microbial cellulose-based paper according to [Claim 8], wherein the inorganic filler to resin adhesive weight ratio is of 2.1 to 4:1 , preferably 1 :1 to

[Claim 10] A process for producing microbial cellulose-based paper according to any one of [Claim 1 ] to [Claim 9] comprising the steps of: a) providing wet microbial cellulose, wherein such wet microbial cellulose is either sourced in wet form or is obtained by blending microbial cellulose in dry form with water until a homogeneous mixture is obtained; b) adding an inorganic filler and optionally one or more additive, preferably a resin adhesive, to the wet microbial cellulose provided in step a) in an amount such that the microbial cellulose to inorganic filler are present in a dry weight ratio of 5:1 to 1 :13 and blend until a homogeneous mixture is obtained; and c) shaping and drying the mixture obtained in the end of step b) to obtain paper, preferably by pressing to form a flat sheet of paper or by molding. wherein the microbial cellulose, the organic filler, the resin adhesive and their respective ratios are as defined in any one of [Claim 1 ] to [Claim 9],

[Claim 11 ] A process according to [Claim 10], wherein the microbial cellulose is provided by

- growing at least one cellulose-producing microbial strain in a fermentation medium having an acidic pH, preferably a pH of 6 or less, comprising water, carbohydrates, optionally a nitrogen source and optionally a live yeast strain;

- harvesting the cellulose; and

- drying the harvested cellulose to a desired cellulose level.

[Claim 12] A process according to [Claim 10] or [Claim 11 ], wherein the wet microbial cellulose is provided in step a) by blending dry microbial cellulose with water in a cellulose to water weight ratio of 1 :33 to 1 :800, preferably 1 :300 to 1 :800, more preferably 1 :200 to 1 :300, even more preferably 1 :100 to 1 :200, most preferably 1 :33 to 1 : 100, at 17000 to 35000 rpm, preferably 25000 to 35000 rpm for 1 to 2 minutes, followed by a break and further blending under the same conditions until the blend is homogeneous.

[Claim 13] A process according to [Claim 10] to [Claim 12], wherein the wet microbial cellulose provided in step a) has a cellulose content of at least

0.5wt%, preferably at least 1wt%, more preferably at least 2wt%, most preferably at least 3wt%, based on the total weight of the wet microbial cellulose.

[Claim 14] A microbial cellulose-based paper obtained or obtainable by the process of any one of [Claim 10] to [Claim 12],

[Claim 15] A packaging material comprising or consisting of a microbial cellulose-based paper of any one of [Claim 1] to [Claim 9]

[Claim 16] Use of a microbial cellulose-based paper according to any one of [Claim 1] to [Claim 9] as a packaging material.