“Fungal mat coating method and bio-based composite materials obtained therefrom”

DESCRIPTION

Technical Field

The present application relates to a new family of bio-based composite materials, and the method for manufacturing thereof. More in particular, the invention relates to the method for the coating of fungal mats derived from living fungal paste or slurry by using a bio-based polymer composition, and to the products obtained therefrom, in particular for application in the soft goods market, as for example leather, leather like, fabrics, upholstery and textile-like products.

Background art

The textile industry is one of the most polluting industries in the world and has a substantial impact on the environment.

In recent years, a great deal of attention has been focused on the development of new sustainable and compostable textile materials obtained by the use of environmentally friendly, non-pollutant processes.

More specifically, in the field of animal derived products, alternatives to the use of animal skin are a growing trend in several markets due to the increase of awareness towards environmental impact and animal welfare. The production of animal leather raises ethical issues and has a negative impact on the environment due to the use of substantial amounts of natural resources as well as toxic chemicals used for the processing of the skins. Different strategies have been proposed in order to produce animal-free and sustainable leather-like materials. For example, products have been obtained from waste materials deriving from apple juice production, pineapple or fungi.

Fungi, in particular, are one of the most abundant and fastest growing living organisms on the planet.

Fungal mycelium is the vegetative structure of the fungi and consists of a network of fine filaments, called hyphae. Hyphae are formed by cells that grow as tubular, elongated structures with a diameter of 2-10 pm and form a tight network of interlocking filaments. The cells are surrounded by the cell wall, which can make up type glucans, chitin and other structural proteins. Due to the high amounts of chitin in the cell walls and its similarities to cellulose in terms of structure, it has been suggested that fungal mycelium could find industrial application as an alternative to wood pulp in the paper, biomedical and textile fields.

Fungal flexible materials (FFMs) normally consist of mats of pure fungal mycelium that are used for soft good manufacturing, being a circular and low-impact solution with natural colors and malleable surfaces ranging from soft and velvety to cork-like, resembling suede, felt or rubber to the touch. However, the materials do not meet the mechanical performance needed for industrial application exhibiting low tear resistance and high abrasion susceptibility. FFMs production, indeed, is a new branch in the fungal biotechnology scene with less than 15 years in the business and yet in its very infancy, consequently such research activities are far from providing ready-to-scale results. Therefore, companies trying to provide functional solutions are implementing more traditional approaches in order to improve the physical and mechanical characteristics of leather-like FFMs, mostly directly imported from the classic leather and textile manufacturing industries.

Such methods range from simple techniques applied during the cultivation phase such as embedding reinforcement fibers (e.g. polyester, polyamide, nylon, viscose, cotton, silk, wool, cellulose, etc) within the growing fungal matrix of hyphae to form a more homogenous and resistant fungal composite as reported in W02020006133A1 , or surface homogenization methods such as mechanical abrasion and pressure that smooth and enhance the microstructure of the mycelium as described in W02020018963A1 , or more advanced chemical treatments including deacetylation and crosslinking of the chitin and chitosan fractions naturally present in fungal materials with added chitin nanowhiskers via genipin, so the chitin nanowhiskers get impregnated and crosslinked within the mycelial matrix improving overall mechanical resistance, a fairly promising method as disclosed in WO201 9178406A1.

On the other hand, use of more traditional organic solvents such as alcohol and acetic acid, and treatment with salts (calcium chloride), phenols, polyphenols, tannins, waxes, plasticizers (glycerine, sorbitols, etc.) and/or dyes has been suggested by WO2018183735A1. This patent application simply describes a mycological biopolymer which can replace textiles, leather, and leather-like materials made of, for example polyurethane, silicone, and poly vinyl acetate. There is neither disclosure nor suggestion to coat the mycological biopolymer with a single bio-based polyurethane layer obtained by spray coating a bio-based polyurethane composition.

Similarly, EP2554559 discloses the use of bio-based polyurethane resin to prepare artificial or synthetic leather, without any disclosure or suggestion to use a polyurethane resin to coat artificial or synthetic leather The Applicant has already faced the problem and filed an international patent application PCT/IB2019/060466 describing and claiming a method to produce a fungal mat of increased homogeneity compared to the fungal mats previously described and with multiple advantages in terms of logistics, costs (both capital and operational) and contamination risks. Such a fungal mat is composed of pure fungal biomass or mycelium, different from a composite, and free of embedded fibers and discrete lignocellulosic particles. In short, a flexible, tough, homogeneous and aesthetically pleasant fungal flexible material that could be used as an alternative to soft goods materials.

Considering its biodegradable nature, and despite all the listed benefits and the overall superior quality of the fungal mats obtained thereby, in its raw form these fungal mats are still characterized by a relatively poor flexibility and are still subjected to tearing and abrasion when used on its own on a daily basis, especially when applied as footwear, upholstery, interior design elements, or luggage, and thus, a proper coating becomes necessary to protect the material and boost its physical and mechanical properties to provide a durable and truly functional product. Such a coating application is a common treatment in the traditional leather industry used to enhance and functionalize animal hides, which are also extremely weak and brittle in their natural raw state. Indeed, for the manufacture of animal leathers many other chemical and mechanical treatments are required to improve the performance of the raw skins. Normally, a vast variety of coating products or mixtures are sprayed on them, such as dyes, resins, oils, paraffins, glues, and multiple polymers of petrochemical origin. Composite materials obtained by post-treatment methods such as backing the dry mycelium mats with one layer of porous material, such as a fabric of natural origin (hemp, cotton or linen) or a synthetic or natural polymer (polyhydroxyalkanoates (PHA), polyglycolic acid (PGA), poly-e-caprolactone (PCL), polylactic acid (PLA), cellulose acetate, chitin/chitosan, corn zein and/or starch) are also disclosed in international patent application PCT/IB2019/060466.

W02020087033 discloses an abrasion resistant finish for a fungal material, the finishing comprising an optimum quantity biodegradable polylactic acid plastic (PEA) dispersed in water to produce a PEA mixture. The finish fortifies the hyphal structure as the water evaporates and creates a PEA coating on the fungal material with improved abrasion resistance and water resistance. Optionally, at least one surfactant layer, including at least one of polyurethane binder, isopropyl alcohol and 2-butoxy ethanol, and other additional layers that contain color pigment, other acrylics, silicones, resins or polyurethanes or the like, are added to the PLA coated fungal material with a three-part leather spray coating process to improve the effectiveness of the abrasion resistant finish.

PolyVinyl Chloride (PVC), Polyethylene (PE), Polypropylene (PP), Polystyrene (PS) and Polyurethanes (PU) are petrochemical polymers commonly used in the production of heavy duty leather coatings and textile products per se. Notwithstanding their considerable contribution to human wellness and development, most of these compounds are considered harmful for the environment and non-recyclable in the practice, therefore accumulating and polluting landfills and water streams worldwide. Between all of these, at least polyurethanes are considered a digestible material to a variety of microbes, specially fungi, whose enzymes play a crucial role in the biodegradation of this and other polymeric materials.

Exploding the advantageous characteristics of PU-based materials and the theoretical and promising possibility of full biodegradation in the short term, in recent years researchers started to develop the so called bio-polyurethanes (Bio-PUs), which are PU formulations containing from 20% to 90% bio-based ingredients or renewable carbon fractions, mostly comprising polyols and fillers from vegetal biomass, and thus boosting its biodegradability while reducing the manufacturing carbon print. Bio-polyurethanes have found a wide range of applications in rigid insulations, paints, coatings, adhesives, foams, elastic fibers, flooring, textiles and footwear.

However, in the applicant's knowledge, there are no specific descriptions of coating methods, especially wet-end, of mycelium flexible mats. More specifically, no literature can be found regarding the application of PU or bio-PU coating products to fungal biomaterials.

On the contrary, the above mentioned W02020018963A1 specifically discloses several drawbacks not yet addressed in applying polyurethane to mycelium material, such as the difficulty in making typical common coatings such as polyurethanes and acrylics to adhere to the mycelium, which would also requires additional cost and processing while simultaneously detracting from the natural quality of the mycelium material and eliminating its biodegradability. So, W0202001 8963A1 neither discloses nor suggests to coat a mycelium material with a single bio-based polyurethane layer obtained by spray coating a bio-based polyurethane composition, but rather it points out the difficulties of making such a process.

Further, one of the main factors limiting the industrial uptake of mycelium mats is the poor mechanical and superficial properties, and the attempts of coating application performed up to now resulted in poor results, due to the adhesion limitations generated by the morphology and chemistry of the substrate.

Therefore there is a need for a tailored coating processing that results in high quality mycelium mats in terms of high resistance, flexibility and sustainability.

Moreover, many of the coatings currently used by the traditional leather industry present serious limitations and drawbacks in terms of environmental-friendliness and overall sustainability, hence there is yet the need for improved bio-PU formulations that can be digested more efficiently by microbes once the life cycle of the material or product is due, implying a neutral or negative carbon footprint, and leaving behind nothing but nurturing elements for the soil and the biosphere. Finally, there is a need for a new method that provides fungal mats with improved mechanical and aesthetical properties.

Summary of the invention

The Applicant has found a new method for use in coating bio-fabricated soft materials, especially materials of fungal origin, more preferably mycelium mats. In particular, the method comprises the application of a multiple-component coating composition onto a surface of a fungal mat with the aim of improving the tear and tensile strength, the flexibility and the resistance to abrasion of the fungal mat.

The present invention describes a coating method, preferably based on spray coating and using a bio-based coating formulation, able to overcome current limitations in fungal flexible materials and to drastically improve their mechanical and physical properties.

Accordingly, a first aspect of the present invention relates to a method for preparing a flexible composite material comprising the steps of: 1) providing a coating composition comprising a bio-based polymer having a viscosity of 50 to 2,500 centipoise;

2) providing a flexible fungal material having a front (aerial) side and a back (grain) side, wherein the aerial side is capable of absorbing the coating composition; 3) applying the coating composition onto the front (aerial) side of the flexible fungal material to provide a wet coating layer; and 4) drying the wet coating layer to provide a flexible composite material comprising a dried coated layer onto a flexible fungal material, wherein said dried coated layer has a weight of from 0.05 to 3.00 % by weight, based on the weight of the uncoated flexible fungal material, and wherein said bio-based polymer is a bio-based polyurethane.

A second aspect of the present invention relates to a flexible composite material substantially consisting of:

(a) a flexible fungal material comprising at least of 90 wt%, preferably at least 95 wt%, and more preferably at least 98 wt% of pure fungal biomass, based on the total weight of the flexible fungal material, and

(b) a dried coated layer comprising a bio-based polymer, wherein said dried coated layer has a weight of from 0.05 to 3.00 % by weight, based on the weight of the uncoated flexible fungal material. A third aspect of the present invention relates to a finished product comprising at least one component realized with the flexible composite material according to the second aspect of the present invention.

Description of the Figures Figure 1 shows the harvesting of the fungal mat obtained in Example 2.

Figure 2 shows the PU-coated fungal mat obtained in Example 3.

Definitions

The term “soft good” as used herein refers to any product made of, or comprising, a soft flexible material such as textiles and/or leather. These include apparel, cloth, garment, footwear, headwear, sportswear, backpacks and luggage, bedding, linens, consumer electronic accessories, coverings for furniture or automotive etc.

The term “lignocellulosic material” as used herein refers to a material that contains as main components cellulose, hemicellulose and lignin, and, optionally, smaller amounts of pectin, proteins and ash. The relative content of each of these constituents varies depending on the origin of the lignocellulose material.

The term “mat” or “fungal mat”, as used herein, refers to a sheet of material formed by interwoven or interconnected fungal hyphae forming a continuous and flat surface. Preferably, said sheet of material exclusively consists of fungal mycelium. The term “mycelium” as used herein refers to the vegetative body of a filamentous fungus made of a mass of branching filaments, called hyphae.

The term “filamentous fungus” as used herein refers to any member of the group of eukaryotic organisms including ascomycete and basidiomycete fungi that form filamentous structures known as hyphae. Flyphae are multicellular structures that are tubular, elongated and thread-like (filamentous), which may contain more than one nucleus per cell and that grow by branching and extending at their tips.

The term “solid nutritive medium” as used herein refers to a solid substrate that provides both support and nutrients for the growth of fungal mycelia.

The term “pure culture” as used herein refers to an axenic culture in which only one strain or clone is present, in the absence of other organisms or types.

The term “flat container” as used herein is a container comprising a flat base surface enclosed by sides.

The terms “living fungal slurry”, “living slurry”, “mycelial slurry”, “fungal slurry” or eventually just “slurry” as used herein, refer to a viscous fine blend or dispersion of substrate particles, fluids (i.e. liquid or/and gas) and living fungal hyphae.

The terms “blending” or “blending step” as used herein refer to the process of obtaining a living fungal slurry starting from a pre-colonized solid substrate and water by mechanical means suitable to achieve the above-mentioned living fungal slurry.

The wording "consisting essentially of" excludes additional limitations that would materially affect the basic and novel characteristic(s) of the claimed invention. More in particular, in the context of the present invention such a wording excludes the presence of additional layers that would materially affect the basic and novel characteristic(s) of the claimed invention.

Detailed description of the invention

The present invention relates to a method for preparing a flexible composite material comprising the steps of:

1 ) providing a coating composition comprising a bio-based polymer having a viscosity of 50 to 2,500 centipoise;

2) providing a flexible fungal material having a front (aerial) side and a back (grain) side, wherein the aerial side is capable of absorbing the coating composition;

3) applying the coating composition onto the front (aerial) side of the flexible fungal material to provide a wet coating layer; and

4) drying the wet coating layer to provide a flexible composite material comprising a dried coated layer onto a flexible fungal material, wherein said dried coated layer has a weight of from 0.05 to 3.00 % by weight, based on the weight of the uncoated flexible fungal material, and wherein said bio-based polymer is a bio-based polyurethane.

In a preferred embodiment, the coating composition comprises a bio-based polymer dissolved or dispersed in a carrier.

The carrier is preferably selected from the group consisting of water, organic solvents, and mixture thereof.

The organic solvent can be selected from the group consisting of alcohol such as ethanol, di acetone alcohol, isopropanol or n-butanol; ketones, such as acetone, ethers, such as dimethyl ether, diethyl ether; alkanes such as pentane, cyclopentane, hexane, toluene, heptane or cyclohexane; cyclic ethers such as tetrahydrofuran; glycol ethers, such as ethylene glycol monobutyl ether acetate; phenylated solvents such as xylene; esters of acetic acid such as butyl acetate, methyl acetate, pentyl acetate, propyl acetate or ethyl acetate; and a mixtures thereof.

The coating composition preferably comprises a carrier in an amount ranging from 10% to 90% by weight, more preferably from 20 to 80 wt% based on the total weight of the coating composition.

Preferably, the coating composition has a viscosity of from 100 to 2,000 centipoise, more preferably from 200 to 1 ,500 centipoise, and most preferably from 300 to 1 ,000 centipoise.

The bio-based polyurethane is a polyurethane obtained by a method including a step of reacting a polyol and a polyisocyanate compound, wherein at least one of polyol and polyisocyanate compound is derived from biomass resources, i.e., is a bio-based ingredient.

Preferably, the bio-based polyurethane has a bio-based ingredient content ranging from 20 to 90 wt% based on the total weight of the bio-based polyurethane. Biomass resources include those in which solar light energy is converted in a form of starch, sugar, cellulose, or the like due to photosynthesis of plants and stored; animal bodies growing by eating vegetable bodies; products prepared by processing vegetable bodies or animal bodies; and the like. Vegetable resources are more preferable as the biomass resources. Examples of the vegetable resources include wood, rice straw, chaff, rice bran, old rice, corn, sugar cane, cassava, sago palm, bean curd, corn cob, tapioca, bagasse, vegetable oil dregs, potato, soba, soybean, fats and oils, wastepaper, papermaking residue, aquatic residue, livestock excrement, sewage sludge, food waste, and the like.

Useful examples of bio-based polyurethane and production methods thereof are known in the art, as described, for example in WO2018220983A1 and EP2554559. A large number of vegetable oil derivatives based on castor, soybean, sunflower, olive, peanut, canola, corn, and safflower oils, among others, are used as naturally obtained bioresources to produce a wide variety of bio-based polyurethanes with diDerent structures and chemical compositions.

Biomass resources can also include fungi. Advantageously, the bio-based content as fungal-based ingredient could be ranging from 1 to 30% by weight based on the total weight of the bio-based polyurethane. Fungal based ingredients are preferably selected from the group consisting of fungal polyols, or fillers like chitin and/or glucan.

According to a further embodiment, the coating composition can further comprise crosslinking agents and additives selected from the group consisting of suspending or dispersing agents, surfactants, antifoaming agents, anti-gelling agents, anti oxidation agents, thickening agents, moisturizers, stabilizers, handle modifiers, plasticizers, flame retardants, pigments, fillers, glittering agents, and fragrances. Advantageously, the flexible fungal material is obtained according to a method as described in PCT/IB2019/060466 comprising the steps of: a) inoculating and growing a filamentous fungal species onto a solid nutritive medium comprising a lignocellulosic material, thereby obtaining a solid nutritive medium colonized by said fungal species; b) mixing said colonized nutritive medium with water or with an aqueous solution and blending at high speed to obtain a homogeneous living fungal slurry; c) pouring the living fungal slurry into a flat container; d) incubating the living fungal slurry until a continuous fungal mat of the desired thickness and density is formed on the top surface of the living fungal slurry; e) harvesting the fungal mat thus obtained; and, optionally f) washing the harvested fungal mat. Any species of filamentous fungi may be used in the method of the invention. However, particularly preferred are the fungal species belonging to the basidiomycota divisions. Preferably, said fungal species is selected from Ganoderma, Trametes, Fomes, Fomitopsis, Phellinus, Perenniporia, Pycnoporus, Tyromyces, Macrohyporia, Bjerkandera, Cerrena and Schizophyllum. The use of other species belonging to the genera Fusarium, Rhizopus, Aspergillus, Myxotrichum and Trichoderma is also feasible under the method described herein. Particularly preferred species of fungi due to the features of the final mat obtained are Ganoderma spp., Fomes spp., Pycnoporus spp. and Perenniporia spp. According to a preferred embodiment, in step a) a pure culture of a filamentous fungus is inoculated. Alternatively, a combination of different species or strains of fungi can be used.

According to a preferred embodiment, said solid nutritive medium of step a) consists of at least 90%, preferably 95%, more preferably 98%, even more preferably 100% of its total weight of lignocellulosic material. The lignocellulosic material may also be chemically treated in order to improve its texture, pH and nutritional properties by, for example, adding calcium sulfate, calcium carbonate or other similar mineral amendments or admixed with seeds, seed flour or starch powder.

Accordingly, in an alternative preferred embodiment, said solid nutritive medium comprises as the main component, preferably consists of lignocellulose material admixed with seeds, seeds flour, starch powder, and/or minerals. Preferably, said solid nutritive medium of step a) consists for at least 90%, preferably 95%, more preferably 98%, even more preferably 100% of its total weight of lignocellulosic material admixed with seeds, seed flour, starch powder, and/or minerals. Preferably, said seeds are whole seeds selected from millet, rye, sorghum, rice, wheat, corn whole seeds. Preferably said seed flour is obtained from millet, rye, sorghum, wheat, rice, corn whole seeds. Preferably, said minerals are selected from calcium sulfate and calcium carbonate.

Preferably, the lignocellulosic material for use in the method of the invention is selected from agroindustry lignocellulosic biomass, consisting for example of agricultural crop residues, energy or purpose crops, non-agricultural by products from forestry, paper industry, food and biofuel production, or a combination thereof. The solid nutritive medium is selected according to metabolic needs of the specific fungus used. For example, basidiomycete species belonging to the order polyporales will require a higher content of lignocellulosic materials such as found in wood and straw, while other fungi belonging to other divisions, could require the presence of a percentage of readily available carbohydrates, such as those found in wheat bran and flour.

In step b), said colonized solid nutritive medium is mixed with water or an aqueous solution, preferably sterile or sanitized, and then blended to obtain a homogeneous, viscous and living fungal slurry with physical properties that are in between those of a liquid and a solid resulting similar to a gel state. Preferably, the colonized medium and water or aqueous solution are mixed in a ratio of between 0.5 and 3 g, more preferably 2 g, of colonized medium per 10 ml of water.

The mixture is blended in a high speed mechanical blender, suitable to the amount of material processed, for at least 30 seconds, preferably at least three minutes, and more preferably at least five minutes, until obtaining a living fungal slurry. According to a preferred embodiment, the mixture is blended in a high speed mechanical blender at a speed of at least 10,000 rpm, preferably at least 15,000 rpm, and more preferably at least 20,000 rpm. Preferably, the mixture is blended in a high speed mechanical blender at a speed of no more than 80,000 rpm, preferably no more than 70,000 rpm, and more preferably no more than 60,000 rpm. In a particular embodiment, the mixture is blended in a high speed mechanical blender at a speed of from 30,000 to 50,000 rpm.

Preferably, the living fungal slurry obtained in step b) has a viscosity of from 1 ,000 to 40,000 cps, preferably from 4,000 to 30,000 cps, and more preferably of from 10,000 to 20,000 cps.

In step c), the living fungal slurry is poured into a flat container of the desired form and size. Preferably, the living fungal slurry is added in an amount that completely covers the inner flat base surface of the container. Preferably, the layer of living fungal slurry covering the inner flat base surface of the container has a thickness of from 0.2 to 5 cm, preferably from 0.5 to 1.5 cm to avoid compaction and thus the anaerobic suffocation of the hyphae.

The incubation step d) is carried out maintaining the container horizontally, in static and aerobic conditions at constant temperature. Preferably, the container is covered with a lid featuring a system that allows a controlled gas exchange between the inner volume of the container and the external environment. Depending on the fungal species and the desired growing conditions, a constant CO2 concentration, preferably between 2000 - 2500 ppm, is maintained by monitoring the CO2 concentration in the incubation enclosures by means of electronic sensors. Incubation is carried out until a continuous mycelial mat of the desired density and thickness is formed on top of the slurry. Preferably, this requires that incubation is carried out for a period between 8 and 20 days, more preferably between 10 and 18 days, even more preferably of 15 days. Longer incubation times produce, in general, thicker and more resistant mats.

Once the mat has reached the desired thickness and density, it is harvested as shown in Figure 1 . Advantageously, the desired thickness is ranging from 0.1 to 6.0 mm, preferably from 0.2 to 5.0 mm, and more preferably from 0.3 to 4.0 mm. Particularly, the desired density is ranging from 0.1 to 2.0 g/cm ³ , preferably from 0.3 to 1 .7 g/cm ³ , and more preferably from 0.5 to 1 .4 g/cm ³ . Preferably, the fungal mat of step e) is harvested by separating it from the digested effluents laying underneath. More preferably, harvesting is carried out by peeling the fungal mat out of the container leaving behind the effluents or undigested fraction of the slurry.

Preferably, the flexible fungal material has a tensile strength ranging from 0.5 to 5.0 MPa, measured according with ISO 3376:2011 method.

Further details can be found in international patent application PCT/IB2019/060466, the disclosure of which is incorporated herein in its entirety.

The flexible fungal material harvested in step e) shows a front side and a back side. The front side, also called aerial side, is the side contacting the atmosphere during incubation step d). The back side, also called grain side, is the side contacting the slurry during incubation step d).

The flexible fungal material comprises at least 90 wt%, preferably at least 95 wt%, and more preferably at least 98 wt% of pure fungal biomass, based on the total weight of the flexible fungal material. Advantageously, the flexible fungal material comprises 100 wt% of pure fungal biomass, based on the total weight of the flexible fungal material, i.e., it is totally composed of pure fungal biomass.

According to a preferred embodiment, the flexible fungal material may be pressed before the step (3) of applying the coating composition to facilitate a homogeneous coating layer formation.

The optional pressing step can be performed in a mechanical or hydraulic press at a pressure between 1 .2 bar and 8 bar, more preferable between 2.0 bar and 5.0 bar. Advantageously, the pressing step can be conducted at a temperature ranging from 20° and 80°C, preferably from 40° and 60°C.

The coating step (3) may be performed with several techniques known in the art, such as air spray coating, knife coating, curtain coating, dip coating and the like. Preferably, the coating step (3) is performed either by bar spraying or bar coating, preferably by bar spraying using any type of spray gun or a spraying machine known to be suitable by the one skilled in the art.

Typically such a system comprises at least one air distribution channel for the atomizing air, at least one air channel for the fan air, at least a fluid spray nozzle, and at least one channel for the reagents. The coating composition, containing the carrier and the coating forming formulation, is sprayed through the nozzle, using the Venturi effect generated in the spraying machine.

The advantage of spray coating is the capability of efficiently depositing an amount of coating ranging from 5 to 70 g/m ² , preferably from 10 to 50 g/m ² .

A further advantage of spray coating is the capability of homogeneously filling the porosity of the materials surface.

In an embodiment, the coating composition is applied onto the mycelium surface during the incubation step d) described above.

In another embodiment, the coating composition is applied onto the mycelium surface after the harvesting step e) described above.

In a further embodiment, the coating composition is applied onto the mycelium surface in two or more consecutive steps. Typically, a base and a top coat differing in its composition and properties, are synergistically applied. The base coat is a PU used as adhesive, namely a PU coating that is directly sprayed on the raw surface of the FFM in order to assure the adhesion between the FFM and the next coating layer, such as a top coat or other coating layers. Common features of the PU base coat are the ability to penetrate the substrate or FFM, high elongation and flexibility. Such PU base coats are usually made from polyether or polyester polyols and polyisocyanates as well as solvent or water.

The top coat has higher performances in comparison to the base coat because they are made from polycarbonate or polyester/polycarbonate blend polyols and aliphatic polyisocyanate. Prior to the use, a crosslinking agent is added in a top coat formulation, that is to give to the dried PU a branched micro structure. The final crosslinked top coat will exhibit higher mechanical properties, resistance to solvent, scratch, UV-light and weatherability.

To avoid pinholes, foam formation or orange peel effect, or to improve slipperiness of the top coat, processing aids (e.g. levelling agent, duller, hand-modifier, anti foaming agent) are mixed with the coating composition prior to application.

The drying step (4) provides the evaporation of the carrier and the formation of the dried coated layer. Each wet coating layer is dried at least up to non-tackiness.

The carrier can be evaporated at a temperature ranging from 20°C to 250°C, more preferably between 50°C and 150°C. Within such range, the carrier can be evaporated at a constant temperature or by varying the temperature over time. Advantageously, the dried coated layer has a final coating weight ranging from 1 to 40 g/m ² , preferably from 5 to 30 g/m ² , and more preferably from 10 to 20 g/m ² .

The present invention further relates to a flexible composite material substantially consisting of:

(a) a flexible fungal material comprising at least of 90 wt%, preferably at least 95 wt%, and more preferably at least 98 wt% of pure fungal biomass, based on the total weight of the flexible fungal material, and

(b) a dried coated layer comprising a bio-based polymer, wherein said dried coated layer has a weight of from 0.05 to 3.00 wt% based on the weight of the uncoated flexible fungal material.

The dried coated layer comprising a bio-based polymer is preferably obtained according to step (3) and (4) of the method of the present invention as described above.

In a first preferred embodiment, the flexible composite material has a tensile strength ranging from 8.0 to 50.0 Mpa, measured according with ISO 3376:2011 method.

In a second preferred embodiment, the flexible composite material has a flex resistance ranging from 1 ,000 to 50,000 cycles, measured according with ISO 5402 method in dry conditions.

In a third preferred embodiment, the flexible composite material has a resistance to abrasion ranging from 1 ,000 to 60,000 cycles, measured according with ISO 17076 method in dry conditions.

The flexible fungal material is obtained according to a method as described in PCT/IB2019/060466 and above.

The dried coated layer has a thickness of from 0.001 to 2.000 mm. The dried coated layer can be a thin layer having a thickness lower than 0.500 mm, preferably ranging from 0.0100 to 0.200 mm, or a thick layer having a thickness higher than 0.500 mm, preferably ranging from 0.700 and 2.000 mm, more preferably from 1 .000 to 1 .500 mm.

A third aspect of the present invention relates to a finished product comprising at least one component realized with the flexible composite material according to the second aspect of the present invention. In a preferred embodiment, the finished product is an article of (i) apparel, such as, for example dress, suit, jacket, overcoat; (ii) apparel accessories, such as, for example hat, belt, wallet; (iii) footwear, such as, for example men and women shoes, sneakers, sandals, loafers; (iv) upholstery; (v) luggage, such as, for example suitcase, briefcase, backpack, handbag; or (vi) furniture, such as, for example sofa, armchair, chair, pouffe, deckchair.

The present invention shall be further illustrated hereinbelow by means of a certain number of preparative examples, which are given for purely indicative purposes and without any limitation of the scope of the invention as defined in the appended claims.

EXAMPLES

Example 1

Preparation of top coating composition comprising a bio-based waterborne polymer The reaction was performed in a 250 mL round-bottom, four-necked flask with a mechanical stirrer. First, a mixture of a bio-based polycarbonate polyol, dimethylol propionic acid and bio based chain extenders was added to the flask, followed by water removal at 100°C. The reaction mixture was then cooled and subsequently N-methyl-2-pyrrolidone was added. Afterwards, bio-based isocyanate and organic solvent were added to the mixture and then heated at 80°C for 4 h. Following the previous steps, water was added to the mixture under vigorous stirring (about 2000 rpm) for 10 min. Finally, the organic solvent was removed from the dispersion under reduced pressure at 45 °C, resulting in a bio-based waterborne polyurethane (bio-WPU) emulsion with a solid content of about 13 wt%.

Example 2 Preparation of flexible fungal material

A flexible fungal material has been prepared according to Example 1 of the previous international patent application PCT/IB2019/060466.

A pure culture of the fungus Ganoderma lucidum preserved in a Potato Dextrose Agar (PDA) slant tube was plated on several Malt Extract Agar (MEA) Petri dishes and these were incubated for 5 days at 28°C to create a working stock that could be preserved for at least one week under refrigeration.

Healthy, vigorous and homogeneous sectors of mycelia growing on the Petri dishes were selected and, under clean airflow, transferred using a sterile scalpel to several liquid culture flasks containing Malt Yeast Extract Broth (MYEB), being incubated for 3 days in a shaking incubator at 28°C and 200 rpm. These liquid cultures were then used to inoculate pasteurized (72 C for 1.5h) 3.2kg solid substrate bags containing a 50/50 mixture of hemp shavings (800g) and soy husks (800g) with a moisture content of 50% (1600ml_ H2O). After 7 days of incubation at room temperature (about 23°C) the colonized substrates were manually separated in little chunks and mixed with water, in a proportion of 600 g of colonized substrate per 3000 ml of water, and blended by mechanical means by using a 4L sterile laboratory blender (autoclaved at 121 °C for 30 min.) to obtain a living paste or slurry containing mycelia and growth medium elements. The mycelial paste or slurry was poured flat into flat containers of 55x55cm and then incubated in static conditions at room temperature for two weeks to form a homogeneous and continuous fungal mat on the surface that was manually harvested from the spent effluent laying below.

The fungal mat obtained was moved apart from the spent paste effluent as seen in Figure 1 , manually washed with tap cold water and dried by using a heated vacuum curing table.

Example 3

Coating of the flexible fungal material obtained in Example 2.

Spray coating of the base coat was performed with Telaflex U420 from Langro with 20 wt% of dry matter. No additional levelling agent was added to the mixture. Telaflex U420 is a waterborne PU dispersion, made from the reaction between a polyol and an aliphatic isocyanate. The film formed by the coalescence of PU dispersion and evaporation of solvent is elastic and flexible, particularly suitable for an adhesive application.

Pigments were added to the base coat resin and mixed gently to prevent incorporation of air bubbles. The formulation was then strained into the cup of the gun and sprayed on the flexible fungal material obtained in Example 2. The material sprayed was then dried for 5 minutes at 120°C in a ventilated oven. The final coating weight of the base coat was 8 - 10 g/m ² .

Afterwards, a bio-WPU resin containing 13 wt% of dry matter was applied as a top coating layer. The synthesis of this bio-WPU formulation has been explained in Example 1 . This is an aliphatic PU dispersed in water. The top coating was admixed with more ingredients prior to application, specifically a hand modifier, pigments and isocyanate crosslinking agent (at 2% of the dispersion weight) were added to the bio-WPU resin. After mixing, the material was charged into the gun and then sprayed on the dry base coat. The top coating layer was then cured for 7 minutes at 120°C. The final coating weight of the top coat was 4 - 6 g/m ² . The resulting flexible composite material is shown in Figure 2.

Example 4

The tensile strength of the materials obtained in examples 2 and 3 has been measured according to the standard method UNI EN ISO 3376:2020. The results are summarized in the following Table 1.

TABLE 1

The data of Table 1 clearly demonstrated that the coated material of example 3 according to the present invention had a tensile strength almost eight times higher than the uncoated comparison material of example 2.

Example 5

Preparation of a bio-based waterborne polyurethane containing polyols of fungal origin.

The reaction was performed in a 4-necked 500mL reaction flask coupled with a mechanical stirrer, a temperature probe, an inlet for nitrogen gas and a cooling pipe. The following compounds were added to the flask; dimethylol propionic acid (DMPA), a fungal-based polyol, a plant-based polycarbonate polyol, dibutyltin dilaurate catalyst (0.01 wt% of the prepolymer), N-Methyl-2-Pyrrolidone (NMP) (4 wt% of final WPU) and dry acetone (25 wt% of prepolymer). Subsequently the compounds were mixed under continuous stirring (500-1000 rpm) at 50°±0.5°C, until total dissolution of the DMPA. The mixture was heated up to 60°±2.0°C under reflux conditions and isophorone diisocyanate (IPDI) was slowly added from a pressure-equalized funnel (Lenz®) during a period of 30 min. After adding the IPDI, the reaction mixture temperature was brought to 50°±2.0° C and stirred at 800-1200 rpm for 3h. Subsequently the mixture was cooled down to 40°C and calculated amount of neutralizer (triethylamine) was added and stirred at 1000-1500 rpm for 20 minutes until achieving a degree of neutralization of 85-90%. Afterwards, the reaction mixture was brought to 25°±2.0°C and transferred to a high-speed disc disperser at 10000-15000 rpm (PerMix®), where deionized (Dl) water containing bio-based chain extenders, was added slowly during a period of 10 min over the impeller blades. After adding Dl water, the mixture was continuously stirred at 1500rpm for 30 minutes and then poured into a 5L rotary vacuum evaporator (Rotavapor®) to remove the organic solvent under vacuum at 45°±2.0°C. Finally, the resulting bio-WPU emulsion was cooled down to 25°±2.0°C and collected in a Pyrex® beaker, having a solid content of about 16 wt%.