SE545610C2

SE545610C2 - Algae ink

Info

Publication number: SE545610C2
Application number: SE2130284A
Authority: SE
Inventors: Ida Näslund; Niklas Strömberg; Susanne Ekendahl
Original assignee: Mounid Ab
Priority date: 2021-10-22
Filing date: 2021-10-22
Publication date: 2023-11-14
Also published as: SE2130284A1

Abstract

An algae ink comprising a binder agent for binding a colourant to a substrate, wherein the binder agent is decoloured spherical microalgae; and, a liquid carrier medium, in which the binder agent is suspended. The decoloured spherical microalgae binder agent may comprise the colourant.

Description

Technical field The present invention relates to an algae ink for printing, comprising decoloured spherical microalgae as a binder agent.

Background Printing is a common method for reproducing text and images using a wide variety of ink types. Digital printing has been popuiarized for its speed, cost-effectiveness and great flexibility compared to its predecessors -for example screen printing. However, a problem in digital printing inks is the inclusion of various toxic chemicals in form of additives and film forming polymers.

The most commonly used inks in printing today are water-based dye or dye/pigment inks. Commonly water-based dye/pigment inks used in printing comprise at least a dye/pigment, water, alcohol and a film forming polymer (such as latex and acrylate) acting as a binder agent. These water-based inks also contain various additives such as UV-protectants, preservatives, and thickening agents. These eventually and inevitably leak out and harm the environment, or humans.

As opposed to paints, inks must have relatively low viscosity to enable printing. An ink may be referred to as a colourant, or colouring agent.

The dye or dye/pigments of the inks may for example be inorganic compounds such as chromium hydroxide, v-iron oxide, and cobalt titanate as shown in the water-based ink of EP3144356 (Panasonic Intellectual Property Management Co Ltd). However, using such compounds may for example mean using a conflict mineral. EP3144356 further discloses film forming agents such as acrylic particles. However, the film forming polymers, acting as binder agent, constituting an integral ingredient of the ink, are not biodegradable and therefore contribute to the spreading of microplastics.Furthermore, alternatives of organic solvent based inks and curable resin inks are available on the market. Such inks contain organic solvents, for example toluene or dimethyl formamide, and can be harmful to humans and the environment. lf the ink contains a curing agent this might mean that unreacted species can remain post-curing and said unreacted species may react with and harm humans, animals and the environment.

Algae has been known as a colourant, ink, paint, or thickening agent.

For example, screen printing with algae biomass has previously been disclosed. Such a technique uses the natural dye/pigment within the algae biomass to apply a coloured surface, in the form of a paste, to a material. However, the technique is limited to painting or printing the colour of the algae. The algae biomass is simply applied to a surface and the available colours depend on the native colour of the algae.

WO 2020/097402 (Living lnk Technologies, LLC) describes a pigment produced from microbial biomass. ln WO2020/097402 the microbial biomass may be treated such that the natural pigment within the biomass is removed, the treated biomass is thereafter processed to form a black dye/pigment from the biomass which can be used as a dark colourant.

Clearly, there is a need in the printing industry for a biodegradable, more environmentally friendly ink in various colours that still retains its properties over time and remains safe for living bodies.

Summary Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above-mentioned problems by providing an algae ink comprising a binder agent for binding a colourant to a substrate, wherein the binder agent is decoloured (dye- or dye/pigment-extracted) spherical microalgae; and, a liquid medium, in which the binder agent is suspended. 3 A method of providing an algae ink is also provided.

A method for printing a substrate is provided.

Brief description of appended drawinqs Fig. 1 shows the algae ink when printed on a wallpaper substrate, and Fig. 2 shows the algae ink when printed on a textile substrate.

Fig. 3a shows a schematic drawing of decoloured Chlorella vulgaris algae and fig. 3b shows a schematic drawing of a colourant arranged in the decoloured Chlorella vulgaris algae of fig. 3a.

Fig. 4a shows a 400x magnification microscopy image of decoloured Chlorella vulgaris algae and fig. 4b shows a 400x magnification microscopy image of a colourant arranged in the decoloured Chlorella vulgaris algae of fig. 4a.

Fig. 5a. Schematic illustration of a binder agent being a microalgae, the microalgae containing its natural dye/pigment.

Fig. 5b. Schematic illustration of a binder agent being a decoloured microalgae, into which microalgae a dye/pigment has been inserted.

Detailed Description The present invention is based on the realization that spherical microalgae can function as binder agent. Decoloured spherical microalgae forms a binder agent for attaching ink of various colours to a substrate. Further, it has been shown that by inserting a colourant into decoloured spherical microalgae, algae ink of various colours can be obtained. This removes the need for environmentally harmful components such as cobalt hydroxide (dye/pigment) and acrylate particles (binder agent), thereby alleviating the problems associated with the prior art.A binder agent refers to a Substance that binds colourant to substrate structures and provides the ink with its adhesion, surface tension, integrity, and durability. The binder agent aids in the film formation when the ink has been applied to a substrate. The binder agent helps form a molecular network and enables crosslinks of physisorptive and/or chemisorptive character. lt has surprisingly been identified that decoloured spherical microalgae can act as a binder agent.

The algae ink comprises a binder agent being decoloured (dye or dye/pigment-extracted) spherical microalgae. The natural colour of the spherical microalgae is removed chemically or physically, as is described below, forming a decoloured spherical microalgae binder agent. The binder agent can thereafter be embedded with a colourant to obtain an algae ink of a specific desired colour.

The decoloured spherical microalgae are advantageously spherical microalgae with intact cell wall/membranes. That is, the cell membranes of the decoloured spherical microalgae have not been destroyed via the removal of the dye and/or dye/pigment. Such a process maintains the natural binder properties of the spherical microalgae. The decoloured spherical microalgae may be described as being substantially whole, as the cell wall/membrane is intact.

An advantage of microalgae as a binder agent and/or a colourant source for an ink is that they can be grown locally in aqueous reservoirs and therefore avoids the need of extensive transportation or competition with cultivatable land. Microalgae have a high photosynthetic efficiency meaning that even during the production of microalgae an environmentally friendly effect is present due to its contribution in fighting the greenhouse effect. Also, by using microalgae as binder agent the risk of microplastics leaking into nature is avoided. Furthermore, using biologically derived components, such as microalgae, algae-derived dye/pigment, microbial enzyme-derived dye/pigment, bacteria-derived dye/pigment, plant-based waste-derived dye/pigment, plant-based indigo, or turmeric, allows for an end-product beingnon-toxic and safe. The inventive algae ink may be, because of its components, completely biodegradable. Thus, when printing biodegradable substrates with the inventive algae ink a completely biodegradable product is produced. The algae ink is in particular suitable for printing via a nozzle- based printing technique.

The algae ink may comprise a total amount of 3-60 wt % of spherical microalgae, such as 3-50 wt % of spherical microalgae, such as 5-40 wt % of spherical microalgae, preferably 5-30 wt % of spherical microalgae, more preferably 5-20 wt % of spherical microalgae, most preferably 5-10 wt % of spherical microalgae.

The algae ink may be biodegradable. The algae ink may therefore be capable of breakdown by microorganisms within a time-period of 10 years, such as within 5 years, preferably within 2 years, more preferably within 1 year, most preferably within 6 months.

The colourant i.e., dye or dye/piment, may be biodegradable. The colourant may be capable of breakdown by microorganisms within a time- period of 10 years, such as within 5 years, such as within 2 years, more preferably within 1 year, most preferably within 6 months. Both, or either of, the algae ink or the colourant may be biodegradable via breakdown by naturally occurring organisms. The algae ink and/or the colourant may be biodegradable via specific organisms such that non-intentional biodegradation is avoided.

The term “microalgae” refers to algae, which are unicellular micro- organisms, living in saline, brackish or freshwater, having a size in the micrometre range, or slightly below. The microalgae of the present invention may have a diameter in the range of 0.1-100 um. ln the present disclosure, the term microalgae refers also to cyanobacteria, which although technically a bacteria have commonly been called algae. The microalgae of the present invention are preferably denatured microalgae or denatured cyanobacteria.

The microalgae may be selected from the group of photosynthetic protistswithin the taxonomic Kingdom Protista. The microalgae are preferably dried microalgae.

The term “spherical microalgae” refers to microalgae with a substantially spherical shape e.g. the cell wall of each of the microalgae form a substantially spherical entity. The spherical microalgae of the invention have tough cell walls allowing for them to remain unbroken e.g., during preparation, storage and printing of the ink. Since cell walls/membranes of the spherical microalgae of the inventive ink remain unbroken the colourant can be arranged in a stable position in the spherical microalgae. Spherical microalgae provide the algae ink with good rheological properties and thus improves the printability of the algae ink.

The term “chromophore” refers to the colouring part of a dye molecule, typically ring structures with conjugated double bonds.

The term “dye” refers to the entire molecule including the chromophoric part, the chromophore, along with non-colouring parts that for example may govern the polarity of the dye and solubility in either polar and nonpolar liquids. A dye is therefore considered as soluble.

The term “dye/pigment” refers to much larger in size colouring solid particle (with chromphoric parts), typical considered as insoluble and instead dispersed in the solvent. Due to the size of the particle, it may also give light scattering effects that affects the colour.

The distinction between dyes and dye/pigments are often not precise in the literature to make and thus the term colourants are then used instead. The colourant may be a dye, a dye/pigment. The decoloured spherical microalgae may be a dye or dye/pigment extracted spherical microalgae depending on the components removed in the decolouring process and/or the type of spherical microalgae.

The term ”“colourant”” refers to a dye/pigment or dye, which may be arranged within the decoloured, dye or dye/pigment-extracted, sphericalmicroalgae. Examples of naturally occurring dyes or dye/pigments, and processes for their extraction, are further described below.

The term “algae-derived dye/pigment” refers to a dye or dye/pigment extracted from microalgae or, dye or dye/pigment extracted from cyanobacteria. The dye/pigment of the microalgae cells can for example be chlorophyll. The algae-derived dye/pigment may have been extracted from algae by e.g., freeze-thawing, cell disruption, supercritical fluid extraction, reflux extraction, Soxhlet extraction or a combination thereof.

The colourant may be introduced to a cell of a binder agent being a spherical microalga by e.g., ultrasonication, solvents, or electroporation, after which the colourant may reside in the chloroplasts and/or the cytosol of the microalgae. Consequently, the colourant may be provided within the decoloured spherical microalgae acting as binder agent.

The colourant is arranged in the spherical microalgae. Arranging a colourant inside spherical microalgae allows for inks of varying colours and hues depending on the colourant selected. The colourant may be the spherical microalgae's natural dye or dye/pigment, then extraction of all dye or dye/pigment from the spherical microalgae is subsequently followed by reintroduction of one of the dye or dye/pigments into the same spherical microalgae.

The colourant may be selected from the list comprising algae-derived dye/pigment, microbial enzyme-derived dye/pigment, bacteria-derived dye/pigment, plant-based waste-derived dye/pigment, plant-based indigo or turmeric. The colourant may be selected from the list comprising chlorophylls, carotenoids, phycobilins and phycoerythrins. The colourant may be a dye extracted from any of the above sources. Said dyes/dye/pigments are all naturally occurring and thus, biodegradable and non-toxic. Chlorophylls, carotenoids, phycobilins and phycoerythrins are extracted from microalgae, plants, fungi and/or bacteria such as cyanobacteria. As stated above, the colourant may be a dye or dye/pigment extracted from a natural source. Some colourants may be defined as dyes or dye/pigments depending on thespecific components extracted from the source of the colourant. For example, an extracted dye/pigment may comprise protein(s) in addition to the specific chromophore resulting in a substantially large colourant usually defined as a dye/pigment. lt may become soluble or insoluble, whereas a dye may be free from such protein(s) and soluble as well as significantly smaller.

The term “microbial enzyme-derived dye/pigment” refers to a dye/pigment derived from bacteria or other microorganisms integrated with specific genes for specific enzymes. Said bacteria or other microorganisms may be grown in water-based reactors without fossil fuels or toxic material.

The term “bacteria-derived dye/pigment” refers to agent dye/pigment produced by bacteria. The use of bacteria-derived dye/pigments reduces the use of toxic chemical and consumes small amounts of water.

The term “plant-based waste-derived dye/pigment” refers to a dye/pigment derived from waste biomass, such as from agricultural, household or food waste.

Each of the above sources from which the colourant may be derived may also comprise a dye which may be used as a colourant.

The colourant may be a dye. A dye refers to a colourant which is soluble in a liquid carrier medium, a dye/pigment is generally non-soluble. Whether a colourant is a dye or a dye/pigment depends on the source of the colourant and specific process steps in the extraction of the colourant from the source. Both dyes and dye/pigments are suitable for incorporation into or at the spherical microalgae binder agent.

The binder agent is a decoloured i.e., dye or dye/pigment-extracted spherical microalgae. Herein, it is meant that the natural dye or dye/pigment of the spherical microalgae has been removed by e.g., freeze thawing, bleaching, supercritical fluid extraction, reflux extraction, Soxhlet extraction, electroporation, ultrasonication or a combination thereof. Consequently, the spherical microalgae may be deprived of their natural dye or dye/pigment,which allows for the insertion of a different dye/pigment into the dye/pigment- extracted spherical microalgae.

The algae ink comprises a liquid carrier medium. The binder agent is suspended within the liquid carrier medium. Generally, the liquid carrier medium is generally an aqueous, and/or an alcohol-based solution. The use of an aqueous or alcohol-based liquid medium into which the binder agent is suspended is preferred over other solutions such as e.g., toluene or dimethyl formamide as it is more environmentally friendly and/or less harmful to humans.

The algae ink may comprise 0.1-30 wt % of the colourant, 5-30 wt % of the binder agent and 40-97 wt % of the liquid carrier medium, and optionally up to 25 wt % of additives.

The term “additive” refers to any added substance suitable for ink compositions. The additive may be added to enhance or add new properties. The additive may be a surfactant, a pH adjuster, an UV absorber, an UV scattering agent, an antimicrobial agent, an antifungal agent, a deoxidizing agent, an antioxidant agent, an antifading agent, an antifoaming agent, a fragrance, a solvent other than an alcohol or water, a preservative, a rheology-modifier and/or an additional binder agent such as melamine.

The algae ink may comprise 3-30 wt % of microalgae and 45-97 wt % of liquid carrier medium, and optionally up to 25 wt % of an additive. The algae ink may comprise for example 5-10% wt % of microalgae, 50-70 wt % water, 10-30 wt % alcohol, and optionally up to 10 wt % of additives. ln some examples the algae ink comprises 5-10% wt % of microalgae, 50-70 wt % water, 10-30 wt % alcohol, and optionally up to 5 wt % of additives. These components and the relations therebetween are optimized to provide an improved algae ink.

To achieve a coloured ink, the algae ink comprises a colourant, preferably in an amount of 0.1-10 wt %. The colourant is present within the decoloured spherical microalgae being the binding agent. lt may have been provided via e.g., ultrasonication, or electroporation, after which the colourant may reside in the membranes, chloroplasts and/or the cytosol of the microalgae acting as binder agent.

At least 90 wt % of a total amount of spherical microalgae in the ink may have a diameter of 0.5-10 pm, such as of 1-8 pm, such as of 1 .5-7 pm, as determined by a variety of techniques, such as optical measurements using optical microscopes. The diameter of the microalgae may also be determined with a filtering process. The diameter of the microalgae influences the surface morphology and the aesthetic perception of the printed substrate.

The binder agent may be selected from the list comprising Chlorella vulgaris, Haematococcus pluvialis and Dunaliella. The cell shapes, that is, substantially spherical and the cell sizes of these microalgae lend themselves for algae ink applications. Chlorella vulgaris are spherical in shape and without flagella making them especially suitable as binder agent.

The carrier media may be an alcohol, such as an alcohol selected from the group comprising methanol, ethanol, propanol, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, butylene glycol, isopropanol, and hexanediol. The choice of alcohol in the algae ink affects the drying time of the algae ink and co-acts as carrier media with the water. Using alcohol (and/or water) as the carrier media instead of other organic solvents is advantageous since the spreading of toxic organic solvents such as toluene, dimethyl formamide (DMF) and dichloro methane (DCM) can be avoided.

A method of providing an algae ink, such as for printing of a substrate comprises: Providing spherical microalgae. The spherical microalgae may be one or several of the microalgae disclosed above, such as Chlorella vulgaris.

Extracting the naturally occurring, native, colourant from the spherical microalgae, thus forming a decoloured, dye or dye/pigment-extracted, spherical microalgae binder agent.

Providing a colourant to the spherical microalgae binder agent. The colourant may be described as being embedded within the cellwall/membrane/cytosol of the decoloured spherical microalgae binder agent. The colourant may be provided from a dye or dye/pigment source as described above. The colourant may itself derive from spherical microalgae, or may be derived from various other sources.

The naturally occurring dye or dye/pigment may be extracted from spherical microalgae to form the decoloured, dye/pigment-extracted, spherical algae binder agent by methods such as freeze-thawing, cell disruption, supercritical f|uid extraction, reflux extraction, Soxhlet extraction, ultrasonication, electroporation or a combination thereof.

The colourant may be introduced to microalgae cells by electroporation or other methods after which the algae-derived colourant may reside in the membranes, chloroplasts and/or the cytosol.

The binder agent thereafter comprises a colourant, the colourant in most cases not being the native colourant of the decoloured, dye or dye/pigment-extracted, spherical microalgae. ln some instances, it may be that the colourant for insertion is derived from the same type of microalgae which forms the decoloured spherical microalgae, however, according to the process the dye/pigment is still subsequently inserted to the decoloured spherical microalgae.

The binder agent comprising the colourant is suspended, or dispersed, within a liquid carrier media such as an aqueous or alcohol solution.

The colourant may be provided in 0.1-30 % by weight; the binder agent may be provided in 3-30 % by weight; the liquid carrier medium may be provided in 40-97 % by weight; and the additives are optionally provided in up to 25 % by weight.

As stated above, a method for printing of a substrate with an algae ink is provided. The method comprises: providing an algae ink as defined above; applying the ink to a substrate.The algae ink may be applied by manual application, digital printing: such as inkjet and xerography, large format printing, transfer printing, sublimation printing, gravure printing, offset lithography, forward roller coating, spin coating, flexographic printing, pad printing/tampography, spray dyeing or spray application. The algae ink may preferably be applied to the substrate by a spray nozzle. Manual application includes, but is not limited to, application using a paintbrush, airbrush, roller or spray gun. Digital printing and spray dyeing, using the algae ink allows for a fast and effective printing method that limits the waste material and optimizes the materials consumption. As stated above, the algae ink is especially suitable for nozzle based printing techniques where the algae ink is applied via a nozzle through which the algae ink is provided. The relatively low viscosities achievable with the algae ink enable such nozzle based printing techniques.

The substrate may for example be paper-based, such as cardboard, wall-paper or paper, or textile-based.

Due to the nature of the algae ink, the substrate may ideally be a biodegradable material, such as a biodegradable textile and/or fibre. The biodegradable textile may comprise fibres selected from a group comprising: cellulose fibre, cotton fibre, silk fibres, phragmite fibres, bamboo fibres, abaca fibres, flax fibres, kozo fibres, wheat fibres, sisal fibres, rice fibres, hemp fibres, rattan fibres, or linen fibres. The substrate may be a biodegradable material, such as a biodegradable cellulose-based material, such as cardboard. Using a biodegradable material allows for an end-product being completely biodegradable.

As described the algae ink may be applied by a spray dyeing device, a digital printer or 3D printer. Using these application methods allow for a fast and effective method while minimalizing waste of products. The ink is preferably applied through a nozzle, the nozzle having an aperture opening through which the algae ink is dispensed. Preferably, the aperture opening has a diameter in the range of 200-400 um, such as in the range of 250-350 um, preferably in the range of 280-320 um. The aperture of the nozzle has adiameter greater than the nominal diameter of the decoloured spherical microalgae, such that the spherical microalgae cells are not disrupted in the dispensing process.

The method forms a printed substrate with a surface roughness average in the range of 1-3 um determined using for example optical microscopy. Producing a printed substrate with a surface roughness average in the range of 1-3 um provides an aesthetic granulated silk-like structure on substrates such as textile. The resolution achieved with said method is suitable for large format prints, spraying, such as spray dyeing large surfaces, printing abstract patterns and various other objects.

Herein, the “nozzle” refers to a unit for controlling the direction and/or characteristics of a fluid flow.

Whilst digital printing has been described in detail above, the algae ink may be applied via manual techniques such as painting, for example the algae ink may be applied to a substrate via traditional brush painting, pens etc.

The algae ink has a viscosity suitable for printing through a nozzle and is therefore not a thick paste.

Experimental section Experiment 1. Alqae ink formulation and printing with alqae dve/piqment and binder from sind/e alqal source. An experiment was performed to determine that dried algae may be used as an algae ink. A single algal species which comprises a natural dye/pigment was used.

Dried Chlorella vulgaris powder (3 g), glycerol (3 g), isopropanol (3 g), detergent (0.3 g) and milli-Q water (up to 30 g) were mixed. The mixture was stirred under heating, resulting in an algae ink with algae comprising its natural dye/pigment. The ink as prepared above was then applied to a wallpaper substrate using a spray nozzle. The wallpaper is shown in Fig.

The top left dot was made by spraying one layer of ink on the wallpaper, thetop middle dot was made by spraying two layers of ink on the wallpaper, and so forth, by adding one layer of ink per dot until the bottom right dot which was made by spraying six layers of ink on the wallpaper.

The experiment confirms that algae may be suitable as an algae ink. However, the algae ink has the natural colour of the algae, and different coloured inks therefore necessitate the use of different algae, each having a different dominating colourant. Furthermore, different algae may have different binding properties. Therefore, an algae based algae ink, where the binding properties of the algae is used, in combination with different, selectable colourants has been developed.

Fig. 2 shows a textile substrate, onto which the ink as prepared above have been applied in an abstract pattern with an overprint design by a spray nozzle.

Experiment 2. Method of extractinq dve/piqment from Spirulina alqae to form a natural biodeqradable dve/piqment. ln order to extract a natural dye/pigment from algae, the following process was used to extract the dye/pigment from Spirulina algae.

A reflux extraction method where a reaction mixture comprising methanol, ethanol, ethanol 96%, ethanol 70% and Spirulina algae at a solvent-phycocyanin ratio of 100 ml/g was provided. The reaction was then stirred and heated step-wise to the boiling point of each solvent for a total duration of 16 h. By said reflux extraction method an algae-derived dye/pigment (fig. 4a) i.e., a dye/pigment extracted from Spirulina algae was obtained.

Experiment 3: Extraction of dve/piqment from a microalqae to form a decoloured spherical microalqae binder. ln order to develop a decoloured spherical microalgae binder for use in algae ink the existing dye/pigment in a spherical microalgae was removed according to the following process to form a dye/pigment-extracted spherical microalgae binder.

The dye/pigment of spherical microalgae, Chlorella vulgaris algae, was extracted from the spherical microalgae using Soxhlet extraction with 1g of dried microalgae in 250 ml 95% ethanol for 10 hours to obtain dye/pigment- extracted spherical microalgae.

Experiment 4: Generation of an alqae ink from example colourant and decoloured spherical microalqae. ln order to produce an algae ink, a commonly used colourant was subsequently provided to the decoloured spherical microalgae generated in experiment The colourant Direct Red (CAS: 2610-10-8) was provided in a high surrounding concentration to a solution comprising the decoloured spherical microalgae binder agent as prepared in experiment The Direct Red was introduced into the cells through a concentration gradient using ultrasonication for 10 min. ln detail, 0.03 g Direct Red was mixed with 3 ml MilliQ water and dried decoloured Chlorella algae. The mixture was vortexed, ultrasonicated for approx. 1 - 1.5 min, centrifuged shortly in a minicentrifuge, the supernatant was removed and the pellet resuspended in new MilliQ water. The washing procedure was repeated 7 times to provide the algae ink comprising a colourant in the decoloured spherical microalgae binder agent (fig 4b).

Experiment discussion The above experiments show that it was possible to provide a algae ink based on a colourant provided to a binder formed by decoloured sphericalmicroalgae. As compared to previous methods of using algae as a means of colouring, the new process enables the use of dye or dye/pigments extracted from various natural sources, or even synthetic sources, not only algal sources, and uses the decoloured spherical microalgae as a binder only, and not the colour source.

Fig. 4a shows a 400x magnification microscopy image of a decoloured Chlorella vulgaris algae and fig. 4b shows a 400x magnification microscopy image of a colourant arranged in the decoloured Chlorella vulgaris algae of fig. 4a. Thus, a successful decolouration and successful arrangement of colourant in the decoloured Chlorella vulgaris algae is shown.

Fig. 5a depicts, in cross section, relevant parts of a spherical alga e.g. a Chlorella vulgaris alga comprising a cell wall 501a, a chloroplast 502a and a natural dye/pigment 503a e.g. chlorophyll and/or carotenoids. When used in algae ink the spherical microalgae is a binder agent.

Fig. 5b depicts, in cross section, relevant parts of a spherical alga, e.g. a Chlorella vulgaris alga comprising a cell wall 501 b, a chloroplast 502b and an biodegradable dye/pigment 503b, wherein the biodegradable dye/pigment 503b is located inside the chloroplast 502b of the Chlorella. Herein, the natural dye/pigment of the spherical alga has been extracted from the spherical alga and a biodegradable dye has been arranged in the spherical alga by e.g. electroporation. Expressed differently, a colourant from a different source than said microalga has been inserted into the spherical alga. lt is understood that there may be other suitable parts of the spherical alga where the dye/pigment can be arranged e.g. at or in the cytosol and/or the cell membrane (not shown).The process of providing the colourant to the decoloured spherical microalgae may be described interchangeably as embedding, introducing or inserting the colourant within the spherical microalgae.

The algae ink may comprise a decoloured spherical microalgae binder provided with a plurality of colourants, i.e., dye/pigment(s) and/or dye(s). That is, each spherical microalgae binder agent may be provided with more than one type of colourant. The algae ink may comprise additives such as flame retardants, water resistant additives, UV protectants, or additives to change the surface characteristics of the algae ink such as smoothing agents, g|ossing agents etc. The additives may be provided within the dye/pigment- extracted spherical microalgae with or without a colourant being present, or may be provided in addition to the binder agent within the carrier medium.

The person ski||ed in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Additionally, variations to the disclosed embodiments can be understood and effected by the ski||ed person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. ln the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not preclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

1. An algae ink comprising - a binder agent for binding a colourant to a substrate; and, - a liquid carrier medium, in which the binder agent is suspended, characterised in that the binder agent is decoloured spherical microalgae.

2. The algae ink according to claim 1, wherein the decoloured spherical microalgae is a dye- and/or dye/pigment-extracted spherical microalgae.

3. The algae ink according to claim 1 or 2, wherein a colourant is comprised within the binder agent.

4. The algae ink according to any of claims 1 to 3, wherein the decoloured spherical microalgae have substantially intact cell walls.

5. The algae ink according to any of claims 3 or 4, wherein the colourant comprised within the binder agent is embedded in each spherical microalgae via a non-destructive insertion process.

6. The algae ink according to any of claims 3 to 5, wherein the colourant is a biodegradable dye or dye/pigment, such as a biodegradable dye or dye/pigment selected from the list comprising algae-derived dye or dye/pigment, microbial enzyme-derived dye or dye/pigment, bacteria-derived dye or dye/pigment, plant-based waste-derived dye or dye/pigment, plant- based indigo or turmeric.

7. The algae ink according to any of claims 1 to 6, wherein at least 90 wt % of a total amount of the spherical microalgae in the algae ink has a diameter of 0.5-10 um, such as of 1-8 um, such as of 1 .5-7 um, as determined using an optical microscope.

8. The algae ink according to any of claims 1 to 7, wherein the decoloured spherical microalgae is selected from the group comprising Chlorella vulgaris, Haematococcus pluvialis and Dunaliella.

9. The algae ink according to any of claims 3 to 8, wherein the colourant is selected from the group comprising ch|orophy||s, carotenoids, phycoerythrin and phycobilins.

10. A method of providing an algae ink comprising: -providing spherical microalgae, -extracting naturally occurring dye and/or dye/pigment from the spherical microalgae to form a decoloured spherical microalgae binder agent, -subsequentiy embedding a colourant within the decoloured spherical microalgae binder agent, -suspending the microalgae binder agent comprising the embedded colourant in a liquid medium.

11. The method according to c|aim 10, wherein the natura||y occurring dye/pigment is non-destructively extracted from the spherical microalgae such that the decoloured spherical microalgae are substantially whole.

12. The method according to c|aim 10 or 11, wherein the colourant is embedded to the binder agent via ultrasonication.

13. Method for printing of a substrate comprising: - providing an algae ink as according to any of claims 1-9; - applying the algae ink to the substrate.

14. A binder agent for an ink comprising decoloured spherical microalgae.