A process for colouring a bacterial cellulose networks

Abstract

A process for colouring a bacterial cellulose network (BC) in a bacterial cellulose pellicle with a pigment composition, said process comprising the steps of adjusting the pH of the pellicle while impregnating the pellicle with said pigment composition, wherein the pigment composition comprises at least a first pigment.

Description

[0001] F07358 31.10.2025

[0002] 1

[0003] TITLE

[0004] A PROCESS FOR COLOURING A BACTERIAL CELLULOSE NETWORKS

[0005] TECHNICAL FIELD

[0006] The present invention relates to a process for colouring a bacterial cellulose network (BC) as well as a coloured fabric comprising such a coloured bacterial cellulose (BC) network.

[0007] PRIOR ART

[0008] It is known that bacteria of certain species can produce cellulose. When cultured, the bacteria can produce a so-called pellicle of cellulose, which is a thick mat of gelatinous consistency and essentially consists of wet bacterial cellulose, which pellicle can be dewatered and dried to provide a fabric-like sheet that may be used in the production of clothes or upholstery as a substitute for leather or textile, for example.

[0009] Generally, leather and textiles are provided in different colors, and if a bacterial cellulose- based substitute is to be accepted by designers, it is necessary to provide the bacterial cellulose-based substitutes for textile and / or leather in a wide variety of colors too. This may be done by essentially coating the sheets of bacterial cellulose with coatings, where a dye or a pigment is mixed with a binder polymer, applied to the sheet of bacterial cellulose and cured. This, however, may not be desirable in cases where the sheet of bacterial cellulose should emulate the look and feel of a colored textile, in which the pigment or dye is not applied as a coating but where the pigment or dye is anchored in the bulk of the yarn. An example in denim cloth, where the indigo particles are precipitated from soaking solution of leuco-indigo into the interstices of the spun yarn via redox reaction.

[0010] Bacterial cellulose forms a tight network of interwoven cellulose filaments which are hard to color, especially when using pigment compositions. In order to efficiently color bacterial cellulose, the particle size of the pigment particle must in general be adjusted to the pore F07358 31.10.2025

[0011] 2 size of the bacterial cellulose network, something that is obtainable for specialty fine pigments, which are exceptionally cost-intensive because of the precisely controlled milling process needed to arrive at such small pigment particles. In the other hand, using coarser (and less expensive) pigments, on the other hand, does not provide an acceptable color effect because a very small fraction of the pigment is retained in the bacterial cellulose network.

[0012] Bacterial cellulose is generally obtained by culturing suitable bacteria, which will form a network of bacterial cellulose filaments known as a pellicle. However, even within a certain species of bacteria, different strains respond even to small changes in culturing conditions such as temperature, agitation, oxygen and nutrient concentration in the culture medium, as well as population density, and concurrently, the density and meshing between cellulose filaments in the pellicle is affected. This further complicates the task of reliably coloring different batches of pellicles using standard pigments and / or processes.

[0013] There exists therefore a need to provide a process by which bacterial cellulose to be used as a color fabric can be efficiently dyed, especially when using standard pigment particles and which can reliably applied to bacterial celluloses obtained via different culturing conditions or from different strains of bacteria.

[0014] SUMMARY OF THE INVENTION

[0015] The present invention therefore provides a process by which bacterial cellulose for use as fabric can be efficiently dyed, especially when using pigment particles whose size is larger than the pore size of native cellulose networks. Furthermore, the process according to the invention, in some embodiments, further allows to reveal at least a part of the macrostructure of the bacterial cellulose, i.e. the grain of the pellicle.

[0016] It is thus a first object of the present invention to provide a process for coloring a bacterial cellulose network (BC), preferably a bacterial cellulose network (BC) for use in a colored textile or leather fabric, comprising coloring a bacterial cellulose network (BC) in a bacterial cellulose pellicle with a pigment composition, said process comprising the steps of adjusting the pH of the pellicle to a pH, and impregnating the pellicle with said pigment composition, wherein the pigment composition comprises at least a first pigment having preferably a particle size of between 20 and 250 pm, preferably between 20 and 150 pm, more F07358 31.10.2025

[0017] 3 preferably between 50 and 150 pm.

[0018] The applicants have found that when the pH within pellicle is adjusted towards basic values, the impregnation of the pellicle is facilitated because the bacterial cellulose network (BC) is loosened in a way that presumably enlarges the interstices or pores. Alternatively, applicants have found that when the pH within pellicle is adjusted towards acidic values, the impregnation of the pellicle is facilitated for small pigments. This in turn allows larger pigments to penetrate more efficiently into the bulk of the bacterial cellulose network (BC) and results in more vivid colors.

[0019] Further embodiments of the invention are laid down in the dependent claims.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

[0022] Fig. 1 shows a cellulose layer coloured with a mixture of white and blue pigment, where the blue pigment is the smaller (D50= 7 pm and D98= 10 pm) and the white pigment is the larger pigment (D50= 50 pm and D90=100 pm). The cellulose layer is coloured 100), when the pH in the pellicle is about 3, the thus coloured bacterial cellulose network (BC) has a pale blue colour.

[0023] Fig. 2 shows a cellulose layer coloured with a mixture of white and blue pigment, where the blue pigment is the smaller (D50= 7 pm and D98= 10 pm) and the white pigment is the larger pigment (D50= 50 pm and D90=100 pm). The cellulose layer is coloured (111) when the pH in the pellicle is about 7, the blue colour displayed in the thus coloured bacterial cellulose network (BC) a less pale and more intense in blue colour.

[0024] Fig. 3 shows a cellulose layer coloured with a mixture of white and blue pigment, where the blue pigment is the smaller (D50= 7 pm and D98= 10 pm) and the white pigment is the larger pigment (D50= 50 pm and D90=100 pm). The cellulose layer is coloured (112) when the pH in the pellicle is about 10, the colour displayed in the thus coloured bacterial cellulose network (BC) is intense F07358 31.10.2025

[0025] 4 blue. As can be seen, when impregnation is carried out at basic pH, the homogenous structure of the bacterial cellulose network is revealed when using different pigments of different sizes and colours, giving the cellulose layer an individual appearance beyond the mere colouring.

[0026] Fig. 4 shows a cross-section view of three coloured bacterial cellulose network (BC) samples placed side-to-side and treated with a mixture of two pigments, blue (approx, particles size of 5pm) and white (approx, particle size of 50pm), at different pH values; at pH=3, the outer sublayers (300) (302) show a pale blue colour, and the inner sublayer (301) shows a more saturated blue colour; at, the outer sublayers (303) (305) show a pale blue colour; at pH 10 the outer sublayers (306) (308) show a pale blue colour, and the inner sublayer (307) shows an even more saturated blue colour.

[0027] DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] It is thus a first object of the present invention to provide a process for colouring a bacterial cellulose network (BC) in a bacterial cellulose pellicle using a pigment composition, said process comprising the steps of adjusting the pH of the pellicle to a pH while impregnating the pellicle with said pigment composition at the adjusted pH, wherein the pigment composition comprises at least a first pigment preferably having a particle size of between 20 and 250 pm, preferably between 20 and 150 pm, more preferably between 20 and 50 pm.

[0029] It is understood that in principle, any microorganism capable of producing cellulose networks may be used to provide the pellicle. Nonetheless, some microorganisms are particularly suited for the production of bacterial cellulose networks such as bacteria from the genera Gluconacetobacter, Novacetimonas hansenii, Aerobacter, Rhizobium, Komagataeibacter rhaeticus Sarcina, Azotobacter, Agrobacterium, Pseudomonas, and Alcaligenes.

[0030] In order to obtain a pellicle using the microorganisms capable of producing cellulose networks, the microorganisms are grown in a liquid culture medium, which may be obtained by comminuting the agricultural and / or industrial waste and / or post-consumer waste in the presence of water to produce an aqueous slurry comprising particles of said waste, which after autoclaving may be used as-is, or which may be filtered to provide a culture medium F07358 31.10.2025

[0031] 5 that is free of solid waste particles. Accordingly, the culture medium is preferably a aqueous liquid culture medium, which may or may not comprise solid particles of agricultural and / or industrial waste and / or post-consumer waste. The liquid culture medium preferably comprises a carbon source, which may be in the form of a hexose such as glucose or a tertiary alcohol such as glycol, or a mixture of both in an amount of 1 to 20% (w / v); a nitrogen source, which may be in the form of a ammonia salt in an amount of 0.2 to 1% (w / v); a buffer such as acetic buffer in an a mount of 1 to 3% (w / v). Thus, the pellicle is grown in a liquid culture medium, and consequently is wet and has a gelatinous consistency. It is understood that except where stated otherwise, the term "pellicle" is to be understood as a bacterial cellulose networks in a wet state, preferably having a water content of more than 50% by weight.

[0032] The process of coloring according to the present invention is suitable for and in particular is designed for bacterial cellulose networks. Bacterial cellulose networks differ from cellulose materials produced by plants in that the cellulose is not associated with other lignocellulosic materials such as lignin or hemicellulose. The individual chains of cellulose are directly secreted into the extracellular space of the culturing medium in which the bacteria are cultured and spontaneously aggregate into cellulose filaments and networks of cellulose filament on account of the interaction between the different filaments. Thus, a bacterial cellulose pellicle is formed, which generally comprises the network of bacterial cellulose filaments and the bacteria secreting the bacterial cellulose filaments, together with organic residuals emanating from the aqueous culturing medium.

[0033] Thus, within the bacterial cellulose pellicle, the bacterial cellulose network (BC) can be isolated to form a planar material that can be used in the manufacture of textiles or leather materials. The ability to color the bacterial cellulose network allows to use the material with more freedom and to provide a material that is not just an ersatz for textile and leather but to a material in its own right.

[0034] In the process of colouring according to the present invention, a pigment composition is used to impregnate the pellicle with said pigment composition. Pigments are solid particles of coloured material, which are deposited onto and / or into a material to be coloured. To this effect, the particles of the pigment composition are generally suspended in an aqueous colouring liquid, and then brought into contact with the material to be coloured, so that the material to be coloured soaks up and entraps at east a fraction of the particles of the pigment composition. Therefore, in a preferred embodiment, the pigment F07358 31.10.2025

[0035] 6 composition is preferably suspended in a colouring liquid, preferably in an aqueous colouring liquid. In accordance with the process of colouring according to the present invention, the colouring liquid may be adjusted in terms of its pH so that it may be used to adjust the pH in the pellicle at the time of impregnating the pellicle with said pigment composition. In a more preferred embodiment, the colouring liquid, in addition to the suspended colouring composition, may further comprise a buffering composition that is suited to maintain a given pH in the pellicle at the time the pellicle is impregnated with the pigment composition.

[0036] In the process of colouring according to the present invention, the bacterial cellulose pellicle may be pre-treated prior to the step of impregnating the bacterial cellulose pellicle with the pigment composition. The native bacterial cellulose pellicle may in cases include the cellulose-producing bacteria as well as organic residuals from the culturing medium, which is why the native bacterial cellulose pellicle may be bleached using a bleaching composition prior to, or at the same time as, impregnating the pellicle with a pigment composition. Suitable bleaching compositions may be based on chlorine-based bleaching agents, hydrogen peroxide or alkaline or earth alkaline metal hydroxides such as for example potassium or sodium hydroxide. Thus, in a preferred embodiment of the present invention the process of colouring includes a step of bleaching the bacterial cellulose pellicle, prior to or at the same time as impregnating the bacterial cellulose pellicle with the colouring composition.

[0037] It is understood that the step of impregnating the pellicle with said pigment composition may be carried using different approaches. For instance, impregnating the pellicle with said pigment composition may be achieved by soaking pellicle in a colouring liquid comprising at least the suspension of the pigment composition for a predetermined time, either at rest or while agitating the pellicle, the colouring liquid, or both.

[0038] In a preferred embodiment of the present invention, the process further comprises the steps of adjusting the temperature of the pellicle to a temperature of between 20 and 95°C, preferably between 30 and 80°C, more preferably between 45 and 75°C, during the impregnation of the pellicle. This can facilitate the colouring process and reduce the time needed to arrive at a given colouring result.

[0039] In a preferred embodiment of the present invention, impregnating said pellicle with said pigment material may be achieved by contacting said pellicle with the pigment F07358 31.10.2025

[0040] 7 composition under pressure, such as for example applying pressure via rolls or platen of a press, or by contacting the pellicle with the pigment composition in a pressured container, preferably under agitation.

[0041] In a preferred embodiment of the present invention, impregnating said pellicle with said pigment material may be achieved while adjusting the temperature of the pellicle, in addition to the pH, to a temperature of between 20 and 95°C, preferably between 30 and 80°C, more preferably between 45 and 75°C.

[0042] In the process of colouring according to the present invention, the step of adjusting the pH of the pellicle to a pH that is predetermined may be achieved via the use of an acid compound, a basic compound, or a buffer composition maintains an acidic or basic environment in the pellicle.

[0043] Exemplary acid compounds may be chosen from inorganic or organic acids such as phosphoric acid, nitic acid, sulphuric acid or hydrochloric acid, for example. Organic acids may be chosen from acetic acid or formic acid, for example.

[0044] Exemplary basic compounds may be chosen from inorganic or organic bases such as hydroxides of metal such as sodium or potassium hydroxide, or such as organic bases such as amines or heterocyclic compounds or ammonia. Examples are ammonia or non- nucleophilic bases.

[0045] In a preferred embodiment of the present invention, the pH is adjusted to an acidic range, preferably of between 1 and 6.5, more preferably of between 1 and 4.5, most preferably to a pH between 2.5 and 3.5. Acidifying the pellicle has the benefit of reducing the retention of larger pigments and of enhancing the retention of smaller pigments.

[0046] In a preferred embodiment of the present invention, the pH is adjusted to a basic range, preferably of between 7.5 and 14, more preferably of between 8.5 and 14, most preferably to a pH between 9 and 11 . Basifying the pellicle has the benefit of enhancing the retention of larger pigments and of reducing the retention of smaller pigments.

[0047] In an embodiment of the process of colouring according to the present invention, the pigment composition comprises at least a first pigment having a particle size of between 20 and 250 pm, preferably between 20 and 150 pm, more preferably between 20 and 50 pm. F07358 31.10.2025

[0048] 8

[0049] In the context of the present invention, the phrase "particle size of X pm" refers to a particle size distribution where at least 50%, and preferably at least 65% and more preferably at least 85% and most preferably 95% of the total number of particles have a particle size of between X / 2 pm and 2X pm, when measured via laser diffraction analysis.

[0050] In an embodiment of the process of colouring according to the present invention, the pigment composition comprises at least a first pigment having a D50-value of 50 pm or more and / or a D90-value of 100 pm or less.

[0051] In the context of the present invention, the phrase "D50-value is X pm " refers to a particle size distribution where the diameter, in micrometers, at which 50% of a sample’s mass is comprised of smaller particles than X pm.

[0052] In the context of the present invention, the phrase "D10-value is X pm " refers to a particle size distribution where the diameter, in micrometers, at which 10% of a sample’s mass is comprised of smaller particles than X pm.

[0053] The same analogous meaning applies to "D90-value is X pm". The D-value is also known as the “mass median diameter”, and said D-values and particles sizes can be determined via laser diffraction measurement, such as for example on a Horiba LA-960V2 apparatus.

[0054] In a preferred embodiment of the present invention, the pigment composition comprises at least a first pigment and a second pigment, wherein the first and second pigment have different particle sizes or D-values, and more preferably where the particle size of the second pigment corresponds at least to twice the particle size of the first pigment. For example, the particle size of the first pigment may be between 20 and 50 pm, and the particle size of the second pigment may be between 50 and 250 pm. In another embodiment, the pigment composition comprises at least a first pigment of particle size of from 20 to 250 pm and a second pigment of particle size of between 1 and 20 pm. It is understood that when the pigment composition comprises at least a first pigment and a second pigment, the first pigment and a second pigment are preferably of a different colour.

[0055] In a preferred embodiment of the present invention, the pigment composition comprises at least a first pigment and a second pigment, wherein the first and second pigment have different particle sizes or D-values, and the first pigment is present at more than 50% by F07358 31.10.2025

[0056] 9 weight or between 50 and 99 % by weight, preferably at more than 75 % by weight or between 75 and 99 % by weight, more preferably at more than 85% by weight or between 85 and 95 % by weight, and the second pigment is present at less than 50% by weight or between 1 and 50 % by weight, preferably at less than 25 % by weight or between 1 and 25 % by weight, more preferably at less than 15% by weight or between 5 and 15 % by weight, based on the total weight of the first and second pigment.

[0057] In a preferred embodiment of the present invention, the process further comprises the steps of subsequently dewatering said pellicle. Dewatering may be achieved via different methods, such as for example by mechanically dewatering the pellicle for example in a press, or such as for example by thermally dewatering the pellicle for example in a drying oven, or a combination of both mechanical and thermal dewatering. In another preferred embodiment of the present invention, the process further comprises the steps of subsequently dewatering said pellicle via freeze-drying.

[0058] In a preferred embodiment of the present invention, the pigment composition comprises at least a first pigment and a second pigment, the pigment composition comprises at least a first pigment and a second pigment, wherein the first pigment and a second pigment are of different colour, wherein one of the first and second pigments a white pigment, more preferably wherein the second pigment is a white pigment. The first pigment may thus be a non-white pigment such as for example be a blue pigment, a black pigment, a red pigment, a green pigment or a yellow pigment.

[0059] White pigment may for example be pigments based on calcium carbonate or titan dioxide. Non-white pigments such as blue pigments, black pigments, red pigments, green pigments or yellow pigments may be based on iron oxide compounds. Thus, the first pigment may be a titan dioxide or calcium carbonate and the second pigment may be iron oxide, or the first pigment may be iron oxide and a second pigment may be a titan dioxide or calcium carbonate.

[0060] It is also an object of the present invention to provide a coloured fabric, in particular a coloured textile fabric such as cloth or felt, or leather fabric, comprising a bacterial cellulose (BC) network, preferably obtained by a process according to the process described above, wherein the bacterial cellulose (BC) network is impregnated with a pigment composition. As stated throughout the application, the coloured fabric, coloured textile fabric, or coloured leather fabric, can preferably be for use in the production of clothes or upholstery as a F07358 31.10.2025

[0061] 10 substitute for leather or textile, for example, or as a material in its own right.

[0062] It is also an object of the present invention to provide a garment or a fashion accessory comprising a coloured fabric, in particular a coloured textile fabric or leather fabric, comprising a bacterial cellulose (BC) network, preferably obtained by a process according to the process described above, wherein the bacterial cellulose (BC) network is impregnated with a pigment composition. As stated throughout the application, the coloured fabric, coloured textile fabric, or coloured leather fabric, can preferably be for use in the production of garments, footwear, or fashion accessories such as handbags, wallets, watchbands, neckties, belts, hats, shawls, hair ties, umbrellas or gloves and such, as a substitute for leather or textile, for example, or as a material in its own right.

[0063] In a preferred embodiment of the present invention, the pigment wherein the pigment composition comprises at least a first pigment of particle size of between 20 and 250 pm, preferably between 20 and 150 pm, more preferably between 50 and 150 pm.

[0064] In another preferred embodiment of the present invention, the pigment composition comprises at least a first pigment and at least a second pigment, where the at least first pigment has a D50-value of 50 pm or more and / or a D90-value of 100 pm or less, and / or where the at least second pigment has a D50-value of 7 pm or more and / or a D90-value of 10 pm or less, in particular when the pH is adjusted to a basic range, preferably of between 7.5 and 14, more preferably of between 8.5 and 14.

[0065] EXPERIMENTAL DATA

[0066] To exemplify the effect of the change in pH during the process of colouring a bacterial cellulose pellicle, a bacterial cellulose pellicle whose pH was adjusted to be acidic, of a pH of about 3, was impregnated with a colouring liquid comprising a pigment composition consisting of a mixture of two pigments. One pigment was white in colour and formed by pigment particles having a particle size of less than 100 pm (D50= 50 pm and D90=100 pm), and the other pigment was blue in colour, and formed by pigment particles having a particle size of about 5 pm (D50= 7 pm and D98= 10 pm). For comparison, a bacterial cellulose pellicle whose pH was adjusted to be neutral, in the range of a pH between 6.5 and 7.5, was impregnated with a colouring liquid comprising a pigment composition F07358 31.10.2025

[0067] 11 consisting of a mixture of the same two pigments. On yet another bacterial cellulose pellicle the pH was adjusted to be basic, of a pH of about 10, and impregnated with a colouring liquid comprising a pigment composition consisting of a mixture of the same two pigments.

[0068] As can be seen from different pictures, in Fig. 1 (100), when the pH in the pellicle is about 3, the thus coloured bacterial cellulose network (BC) has a pale blue colour. Without wishing to be bound to any theory, it is believed that this is due to the retention of a higher fraction of white pigment particles and lesser retention of blue pigment particles. In Fig. 2

[0069] (111) when the pH in the pellicle is about 7, the blue colour displayed in the thus coloured bacterial cellulose network (BC) a less pale and more intense in blue colour, due to the retention of a both fractions of white pigment particles and blue pigment particles. In Fig. 3

[0070] (112) when the pH in the pellicle is about 10, the colour displayed in the thus coloured bacterial cellulose network (BC) is intense blue, due to the retention of a higher fraction of blue pigment particles and lesser retention of white pigment particles. When the mesh of bacterial cellulose network (BC) is widened by a basic pH, more blue pigment particles are thus retained more efficiently, and in this case give the bacterial cellulose network (BC) a more saturated aspect of blue colour. On the other hand, when the mesh of bacterial cellulose network (BC) is constricted by an acidic pH, the blue pigment particles are prevented from efficiently entering the mesh of the bacterial cellulose network (BC), and in this case give the bacterial cellulose network (BC) a less visible blue colour. It is thus possible to modulate the resulting colours of the bacterial cellulose network (BC) when using a same mixture of differently coloured pigments by adjusting the pH during impregnation.

Claims

F07358 31.10.202512CLAIMS1. A process for colouring a bacterial cellulose network (BC) for use in a coloured textile or leather fabric, comprising colouring the bacterial cellulose network (BC) in a bacterial cellulose pellicle with a pigment composition, said process comprising the steps of adjusting the pH of the pellicle while impregnating the pellicle with said pigment composition, wherein the pigment composition comprises at least a first pigment, and subsequently dewatering said pellicle.

2. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to claim 1 , wherein the pH is adjusted to a basic range, preferably of between 7.5 and 14, more preferably of between 8.5 and 14.

3. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to claim 1 , wherein the pH is adjusted to an acidic range, preferably of between 1 and 6.5, more preferably of between 2 and 4.5.

4. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the pigment composition comprises at least a first pigment and a second pigment wherein the first pigment is present at more than 50% by weight or between 50 and 99 % by weight, preferably at more than 75 % by weight or between 75 and 99 % by weight, more preferably at more than 85% by weight or between 85 and 95 % by weight, and the second pigment is present at less than 50% by weight or between 1 and 50 % by weight, preferably at less than 25 % by weight or between 1 and 25 % by weight, more preferably at less than 15% by weight or between 5 and 15 % by weight, based on the total weight of the first and second pigment.F07358 31.10.2025135. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the pigment composition comprises at least a first pigment and a second pigment, wherein the first and second pigment have different particle sizes, and / or the first pigment and a second pigment are of different colour, and / or the at least first pigment having a particle size of between 20 and 250 pm, preferably between 20 and 150 pm, more preferably between 20 and 50 pm.

6. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein said pellicle is impregnated with said pigment material by contacting said pellicle with said pigment material under pressure or vacuum.

7. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein said process further comprises the steps of adjusting the temperature of the pellicle to a temperature of between 20 and 95°C, preferably between 30 and 80°C, more preferably between 45 and 75°C.

8. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the bacterial cellulose (BC) pellicle is obtained from a bacteria from the genus Gluconacetobacter, Novacetimonas, Aerobacter, Rhizobium, Komagataeibacter, Sarcina, Azotobacter, Agrobacterium, Pseudomonas, or Alcaligenes.

9. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the pigment composition comprises at least a first pigment and a second pigment, wherein the first pigment and a second pigment are of different colour, wherein one of the first and second pigments is preferably a white pigment.

10. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the pigmentF07358 31.10.202514 composition comprises at least a first pigment, where said at least first pigment has a D50-value of 50 pm or more and / or a D90-value of 100 pm or less, and preferably where the pH is adjusted to a basic range.

11. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the pigment composition comprises at least a first pigment and at least a second pigment, where the at least first pigment has a D50-value of 50 pm or more and / or a D90-value of 100 pm or less, and / or where the at least second pigment has a D50-value of 7 pm or more and / or a D90-value of 10 pm or less, and preferably where the pH is adjusted to a basic range.

12. The process for colouring a bacterial cellulose (BC) pellicle with a pigment composition according to any preceding claim, wherein the pigment composition comprises at least a first pigment and at least a second pigment, wherein the at least first pigment may be a titan dioxide or calcium carbonate and the at least second pigment may be iron oxide, or wherein the at least one first pigment may be iron oxide and the at least second pigment may be a titan dioxide or calcium carbonate.

13. A coloured textile or leather fabric comprising a bacterial cellulose (BC) network, obtained by a process according to any one of claims 1 to 12, wherein the bacterial cellulose (BC) network is impregnated with a pigment composition, wherein the pigment composition comprises at least a first pigment of particle size of between 20 and 250 pm, preferably between 20 and 150 pm, more preferably between 20 and 50 pm.

14. A coloured textile or leather fabric comprising a bacterial cellulose (BC) network, obtained by a process according to any one of claims 1 to 12, wherein the bacterial cellulose (BC) network is impregnated with a pigment composition, wherein the pigment composition comprises at least a first pigment wherein the at least first pigment has a D50-value of 50 pm or more and / or a D90-value of 100 pm or less, and preferably wherein the pigment composition further comprises at least a second pigment, wherein the at least second pigment has a D50-value of 7 pm or more and / or a D90-value of 10 pm or less.

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