Mycelium Structure

Abstract

A mycelium structure according to the present disclosure includes: a mycelium material including a base portion having hyphae and a polylactic acid permeation layer in which a polylactic acid is permeated into the hyphae; and a polylactic acid coating layer provided on a surface of the polylactic acid permeation layer and thicker than the polylactic acid permeation layer. A thickness of the polylactic acid coating layer is preferably 5.0 m or more and 100.0 m or less. A thickness of the polylactic acid permeation layer is preferably more than 0.0 m and 30.0 m or less. The polylactic acid is preferably a biodegradable polylactic acid. The mycelium material preferably further includes a fiber.

Claims

1. A mycelium structure comprising: a mycelium material including a base portion having hyphae and a polylactic acid permeation layer in which a polylactic acid is permeated into the hyphae; and a polylactic acid coating layer provided on a surface of the polylactic acid permeation layer and thicker than the polylactic acid permeation layer.

2. The mycelium structure according to claim 1, wherein a thickness of the polylactic acid coating layer is 5.0 m or more and 100.0 m or less.

3. The mycelium structure according to claim 1, wherein a thickness of the polylactic acid permeation layer is more than 0.0 m and 30.0 m or less.

4. The mycelium structure according to claim 1, wherein the polylactic acid is a biodegradable polylactic acid.

5. The mycelium structure according to claim 1, wherein the mycelium material further includes a fiber.

6. The mycelium structure according to claim 1, wherein the mycelium material contains at least one of glycerin and oil.

7. The mycelium structure according to claim 1, wherein in a stress-strain curve indicating a relationship between a stress (MPa) applied by a tensile test and a strain (%) at that time, a maximum strain in an elastic region is 4.0% or more and 40.0% or less.

8. The mycelium structure according to claim 1, wherein the mycelium material contains a mycelium formed of the hyphae connected in a three-dimensional shape.

9. The mycelium structure according to claim 1, wherein the mycelium material contains defibrated hyphae.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic longitudinal cross-sectional view of a mycelium structure according to an embodiment.

[0009] FIG. 2 is a process diagram showing a configuration of a method for producing a mycelium structure according to the embodiment.

[0010] FIG. 3 is Table 1 showing configurations of mycelium structures and evaluation results of the mycelium structures in Examples and Comparative Examples.

DESCRIPTION OF EMBODIMENTS

[0011] Hereinafter, a mycelium structure according to the present disclosure will be described in detail based on preferred embodiments shown in the accompanying drawings.

1 Mycelium Structure

[0012] First, the mycelium structure according to an embodiment will be described.

[0013] FIG. 1 is a schematic longitudinal cross-sectional view of the mycelium structure according to the embodiment.

[0014] As shown in FIG. 1, a mycelium structure 100 includes: a mycelium material 10 including a base portion 11 having hyphae and a polylactic acid permeation layer 12 in which a polylactic acid is permeated into the hyphae; and a polylactic acid coating layer 20 provided on a surface of the polylactic acid permeation layer 12 and thicker than the polylactic acid permeation layer 12.

[0015] According to such a configuration, the mycelium structure 100 having abrasion resistance, water resistance, and excellent flexibility is obtained.

[0016] More specifically, the abrasion resistance and water resistance of the mycelium structure 100 can be improved by the polylactic acid permeation layer 12 into which the polylactic acid permeates and the polylactic acid coating layer 20 provided on the surface of the polylactic acid permeation layer 12. Since the polylactic acid coating layer 20 is thicker than the polylactic acid permeation layer 12, the flexibility of the mycelium structure 100 can be improved.

1-1 Mycelium Material

[0017] The mycelium material 10 includes the base portion 11 and the polylactic acid permeation layer 12. In the mycelium material 10, a portion in which the later-described polylactic acid does not permeate is the base portion 11, and a portion in which the polylactic acid permeates is the polylactic acid permeation layer 12.

1-1-1 Components Contained in Mycelium Material

[0018] The mycelium material 10 contains at least mushroom hyphae.

1-1-1-1 Mushroom Hyphae

[0019] The mushroom hyphae have a fibrous structure constituting a mycelium of mushroom. A type of the mushroom is not particularly limited, and examples thereof include Agaricus arvensis, Agrocybe brasiliensis, Amylomyces rouxii, species of Amylomyces, Armillaria mellea, Aspergillus nidulans, Aspergillus niger, Aspergillus oryzae, Ceriporia lacerata, Coprinus comatus, Fibroporia vaillantii, Fistulina hepatica, Flammulina velutipes, Fomitopsis officinalis, Ganoderma sessile, Ganoderma tsugae, Ganoderma lucidum, Hericium erinaceus, Hypholoma capnoides, Hypholoma sublaterium, Inonotus obliquus, Lactarius chrysorrheus, Macrolepiota procera, Morchella angusticeps, Myceliophthora thermophila, Neurospora crassa, Penicillium camembertii, Penicillium chrysogenum, Penicillium rubens, Phycomyces blakesleeanus, Pleurotus djamor, Pleurotus ostreatus, Polyporus squamosus, Psathyrella aquatica, Rhizopus microspores, Rhizopus oryzae, Schizophyllum commune, Streptomyces venezuelae, Stropharia rugosoannulata, Thielavia terrestris, Ustilago maydis, Shiitake mushroom (Lentinula genus), Meripilus giganteus (Meripilus genus), Grifola frondosa (Grifola genus), Leucopaxillus giganteus (Leucopaxillus genus), polyporaceae (Fomitopsis genus), and Tricholoma matsutake (Tricholoma genus).

[0020] The mycelium is an aggregation of multiple mushroom hyphae. In the present disclosure, the term "mycelium" refers not only to a mycelium formed by growth of mushroom hyphae, but also to artificial aggregations of mushroom hyphae. In the following description, the mushroom hyphae are also simply referred to as "hyphae".

[0021] The average diameter of the hyphae is preferably set to be smaller than the average diameter of fibers (fibers other than hyphae) described later. Accordingly, a smooth texture derived from the hyphae is easily imparted to the mycelium structure 100.

[0022] The average diameter of the hyphae is not particularly limited, and is preferably 0.1 m or more and 10.0 m or less, and more preferably 0.3 m or more and 5.0 m or less. When the average diameter of the hyphae is within the above range, the texture of mycelium structure 100 can be particularly enhanced.

[0023] The average diameter of the hyphae is measured as follows.

[0024] First, the mycelium structure 100 is magnified and observed so that 100 or more hyphae are contained in one image, and an image is acquired. Next, 10 or more hyphal images are randomly selected, and the width of a hyphal image is measured. Then, an average value of measured values is taken as the average diameter of the hyphae. The average diameter of fibers (fibers other than hyphae) described later is also measured in the same manner.

[0025] An average length of the hyphae is not particularly limited, and is preferably 0.001 mm or more and 3.0 mm or less, more preferably 0.010 mm or more and 2.0 mm or less, and still more preferably 0.050 mm or more and 1.0 mm or less. When the average length of the hyphae is within the above range, for example, when the mycelium structure 100 is formed into a sheet shape, the hyphae are oriented along a surface of the mycelium structure 100 and the hyphae are moderately entangled with each other. Accordingly, the texture of the mycelium structure 100 can be particularly enhanced.

[0026] The average length of the hyphae is measured as follows.

[0027] First, the mycelium structure 100 is magnified and observed so that 100 or more hyphae are contained in one image, and an image is acquired. Next, 10 or more hyphal images are randomly selected, and the maximum possible length in the hyphal image is measured. Then, an average value of measured values is taken as the average length of the hyphae. An average length of fibers (fibers other than hyphae) described later is also measured in the same manner.

[0028] The hyphae preferably contain chitin. The chitin is contained as a component of a cell wall constituting the hyphae. The chitin is a high-molecular polysaccharide having N-acetylglucosamine in which an acetamide group is added to glucose as a structural unit. Since the chitin has a hydroxyl group, when a crosslinking agent described later is used for imparting strength, the hyphae are easily crosslinked by the crosslinking agent. Accordingly, it is possible to further improve the abrasion resistance and water resistance of the mycelium structure 100.

1-1-1-2 Fiber Other Than Hyphae

[0029] The mycelium material 10 may include a fiber other than hyphae (hereinafter, simply referred to as "fiber"). Accordingly, the abrasion resistance and water resistance of the mycelium structure 100 can be further enhanced.

[0030] The fiber is not particularly limited, and a wide range of fiber materials can be used. Examples of the fibers include natural fibers such as animal fibers and plant fibers, and chemical fibers such as organic fibers, inorganic fibers, and organic-inorganic composite fibers. Specific examples thereof include cellulose, silk, wool, cotton, hemp, kenaf, flax, ramie, jute, Manila hemp, sisal, a coniferous tree, and a broad leaf tree. These may be used alone or may be appropriately mixed and used. These may be used as regenerated fibers subjected to purification or the like.

[0031] As a raw material for the fiber, for example, waste paper or an old cloth may be used, and at least one of the above-described fibers can be used. The fibers may be subjected to various surface treatments. A material for the fiber may be a pure substance or a material containing a plurality of components such as impurities, additives, and other components.

[0032] Among them, fibers containing cellulose are more preferable. The cellulose contains a large number of hydroxyl groups in its molecular structure. Therefore, when a crosslinking agent to be described later is used, a reaction with the crosslinking agent easily occurs, and the abrasion resistance and water resistance of the mycelium structure 100 are easily improved.

[0033] The average diameter of the fibers is not particularly limited, and is preferably larger than the average diameter of hyphae. Specifically, the average diameter of the fibers is preferably 1.0 m or more and 100.0 m or less, and more preferably 3.0 m or more and 50.0 m or less. When the average diameter of the fibers is within the above range, the abrasion resistance of the mycelium structure 100 can be particularly enhanced.

[0034] An average length of the fibers is not particularly limited, and is preferably 0.001 mm or more and 5.0 mm or less, more preferably 0.002 mm or more and 3.0 mm or less, and further preferably 0.003 mm or more and 2.0 mm or less. When the average length of the fibers is within the range, for example, the fibers are oriented along the surface of the mycelium structure 100, and the fibers are moderately entangled with each other. Accordingly, the abrasion resistance of the mycelium structure 100 can be particularly enhanced.

1-1-1-3 Starch

[0035] The mycelium material 10 may contain starch. For example, the hyphae can be covered with starch by immersing the mycelium in a starch solution and then evaporating moisture. Accordingly, the abrasion resistance of the mycelium structure 100 can be further improved.

[0036] The starch is a molecule obtained by polymerizing a plurality of -glucose molecules through glycosidic bonds. The starch may be a linear molecule or may contain a branch. As the starch, it is possible to use, for example, starch derived from various plants. More specifically, it is possible to use, for example, a material derived from cereals such as corn, wheat, and rice, beans such as broad beans, mung beans, and adzuki beans, tubers such as potato, sweet potato, and tapioca, wild plants such as bracken and kudzu, and palm trees such as sago palm.

[0037] The starch may be modified starch. Examples of the modified starch include acetylated adipic acid crosslinked starch, acetylated starch, oxidized starch, sodium octenyl succinate, hydroxypropyl starch, hydroxypropylated phosphate crosslinked starch, phosphorylated starch, phosphate-esterified phosphate crosslinked starch, urea phosphate-esterified starch, sodium starch glycolate, and high amylose corn starch. The starch may be modified starch. Examples of the modified starch include those obtained by processing or modifying starch, and specific examples thereof include dextrin.

1-1-1-4 Plasticizer

[0038] The mycelium material 10 may contain a plasticizer. Examples of the plasticizer include sugar alcohols, oils, adipic acid ester-based plasticizers, phthalic acid ester-based plasticizers, trimellitate-based plasticizers, polyester-based plasticizers, (meth)acrylic acid ester polymers, ethylene copolymer elastomers, chlorinated polyethylene (CPE), (meth)acrylic resins (PMMA), polystyrene resins (PS), polyvinyl acetate resins (PVAc), acrylonitrile-butadiene rubber (NBR), and styrene-butadiene rubber (SBR).

[0039] Examples of the sugar alcohol include maltitol, lactitol, tetritol, pentitol, hexitol, erythritol, sorbitol, xylitol, mannitol, and glycerin.

[0040] The mycelium material 10 preferably contains at least one of glycerin and oil. Accordingly, the flexibility of the mycelium structure 100 can be further enhanced.

[0041] The glycerin is not particularly limited, and may be natural glycerin or synthetic glycerin.

[0042] The oil refers to a hydrophobic liquid, and is generally an ester of an alcohol and a fatty acid. Examples of the oil include plant-derived, animal-derived, and mineral-derived oils. Examples of the vegetable oil include castor oil, rapeseed oil, soybean oil, palm oil, linseed oil, olive oil, avocado oil, sesame oil, perilla oil, cottonseed oil, safflower oil, corn oil, rice bran oil, camellia oil, coconut oil, and peanut oil. Specific examples thereof include epoxidized vegetable oils such as epoxidized soybean oil (ESBO) and epoxidized linseed oil (ELSO).

[0043] When the mycelium contains glycerin or oil, hydrophilicity of the mycelium decreases. Therefore, it is possible to prevent permeation of the polylactic acid described later into the mycelium and to further reduce the thickness of the polylactic acid permeation layer 12. Accordingly, the flexibility of the mycelium structure 100 can be enhanced.

[0044] A content of the plasticizer in the mycelium material 10 is not particularly limited, and is preferably 10.0% by mass or less, more preferably 0.1% by mass or more and 7.0% by mass or less, and still more preferably 0.5% by mass or more and 4.0% by mass or less. Accordingly, the mycelium structure 100 having both abrasion resistance and flexibility can be obtained.

1-1-1-5 Other Components Contained in Mycelium Material

[0045] The mycelium material 10 may contain other components. Examples of the other components include a stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, a flame retardant, an antistatic agent, a colorant, and a filler.

[0046] A content of the other components in the mycelium material 10 is not particularly limited, and is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and still more preferably 5.0% by mass or less.

1-1-1-6 Others

[0047] Substances contained in the mycelium material 10 may be crosslinked with each other by a crosslinking agent. The crosslinking agent reacts with the hydroxyl groups contained in hyphae and fiber when heat is applied. Accordingly, the abrasion resistance and the water resistance of the mycelium structure 100 can be improved.

[0048] The crosslinking agent is not particularly limited as long as the crosslinking agent is an organic compound having a plurality of carboxy groups. Examples of the crosslinking agent include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; dicarboxylic acids having a hydroxyl group such as tartaric acid and malic acid; tricarboxylic acids such as citric acid and aconitic acid; and amino acids having a plurality of carboxy groups such as aspartic acid and glutamic acid. One or a mixture of two or more of these may be used.

[0049] The mycelium material 10 may be treated by an ozone treatment, a deacetylation treatment, sebacic acid, tannin, or the like to change a chemical bond of the mycelium. By these treatments, the abrasion resistance and water resistance of the mycelium structure 100 can be further improved.

[0050] Treatments for improving the abrasion resistance, the water resistance, and the flexibility of the mycelium structure 100 may be performed alone or in combination as appropriate.

1-1-2 Base Portion

[0051] The base portion 11 is a portion of the mycelium material 10 into which the later-described polylactic acid does not permeate. The base portion 11 supports the polylactic acid permeation layer 12 and the later-described polylactic acid coating layer 20.

[0052] The base portion 11 may contain components other than the components described in [1-1-1]. For example, after the mycelium structure 100 is produced, a polylactic acid or the like dropped from the polylactic acid permeation layer 12 described later may be contained.

[0053] A content of the component other than the component described in [1-1-1] in the base portion 11 is not particularly limited, and is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and still more preferably 5.0% by mass or less.

1-1-3 Polylactic Acid Permeation Layer

[0054] The polylactic acid permeation layer 12 is a portion of the mycelium material 10 in which polylactic acid permeates into hyphae. The expression "polylactic acid permeates into hyphae" refers to a state in which the polylactic acid permeates into the mycelium formed by aggregation of hyphae. The polylactic acid permeation layer 12 has a function of improving the abrasion resistance and water resistance of the mycelium structure 100. The polylactic acid permeation layer 12 is located between the base portion 11 and the later-described polylactic acid coating layer 20, and has a function of connecting the base portion 11 and the polylactic acid coating layer 20.

[0055] Since the polylactic acid permeates into the polylactic acid permeation layer 12, the polylactic acid permeation layer 12 has higher rigidity than the base portion 11. Therefore, in order to improve the flexibility of the mycelium structure 100, the thickness of the polylactic acid permeation layer 12 is preferably thinner. Therefore, the thickness of the polylactic acid permeation layer 12 is preferably more than 0.0 m and 30.0 m or less, more preferably 0.5 m or more and 20.0 m or less, and still more preferably 1.0 m or more and 10.0 m or less. Accordingly, it is possible to improve the abrasion resistance and water resistance of the mycelium structure 100 and provide better flexibility.

[0056] The thickness of the polylactic acid permeation layer 12 is measured from a photograph of a cross-sectional structure of the mycelium structure 100 taken with a scanning electron microscope. A thickness of each layer to be described later is also measured in the same manner.

[0057] The polylactic acid in the polylactic acid permeation layer 12 is preferably a biodegradable polylactic acid. Accordingly, an environmental load can be reduced by carbon neutrality of a raw material.

[0058] As the raw material for the biodegradable polylactic acid, for example, a raw material containing starch derived from various plants as a main raw material can be used. More specifically, starch derived from corn, sugar cane, potato, wheat, or the like can be used.

1-2 Polylactic Acid Coating Layer

[0059] The polylactic acid coating layer 20 is provided on the surface of the polylactic acid permeation layer 12 and contains at least a polylactic acid. Accordingly, the polylactic acid coating layer 20 can enhance the abrasion resistance and water resistance of the mycelium structure 100.

[0060] The thickness of the polylactic acid coating layer 20 is preferably 5.0 m or more and 100.0 m or less, more preferably 30.0 m or more and 95.0 m or less, and still more preferably 60.0 m or more and 90.0 m or less. Accordingly, the polylactic acid permeation layer 12 can further improve the abrasion resistance and the water resistance of the mycelium structure 100, and can further improve the flexibility.

[0061] The thickness of the polylactic acid coating layer 20 is greater than that of the polylactic acid permeation layer 12. Accordingly, the thickness of the polylactic acid permeation layer 12 having high rigidity is reduced, and the flexibility, abrasion resistance, and water resistance of the mycelium structure 100 can be achieved.

1-3 Use of Mycelium Structure

[0062] The mycelium structure 100 can be formed into various shapes according to, for example, its use. More specifically, for example, it can be formed into a sheet shape, a board shape, or a web shape. Specific examples of the use include paper, nonwoven fabric, wallpaper, wrapping paper, colored paper, drawing paper, recording medium, decorative sheet, fiber board, filter, liquid absorbent, sound absorber, cushioning material, and mat.

[0063] Since the mycelium structure 100 according to the embodiment is excellent in abrasion resistance, water resistance, and flexibility, the mycelium structure 100 is particularly useful as a naturally derived material such as a leather substitute material (substitute leather).

1-4 Others

[0064] In the mycelium structure 100 according to the embodiment, in a stress-strain curve indicating a relationship between a stress (MPa) applied by a tensile test and a strain (%) at that time, the maximum strain in an elastic region is preferably 4.0% or more and 40.0% or less, more preferably 5.0% or more and 30.0% or less, and still more preferably 7.0% or more and 25.0% or less. According to such a configuration, the flexibility of the mycelium structure 100 can be particularly improved.

[0065] For the tensile test, for example, Autograph AGS-5kNX (manufactured by Shimadzu Corporation) can be used.

[0066] Regarding the components described in [1-1-1], conditions may be different between the base portion 11 and the polylactic acid permeation layer 12, or may be the same.

2 Method for Producing Mycelium Structure

[0067] Next, an example of the method for producing a mycelium structure 100 described above will be described.

[0068] FIG. 2 is a process diagram showing a configuration of the method for producing a mycelium structure according to the embodiment.

[0069] The method for producing the mycelium structure 100 shown in FIG. 2 includes a mycelium preparation step S102 of preparing a mycelium, a coating step S104 of applying a polylactic acid coating agent to the mycelium, and a drying step S106 of drying the applied polylactic acid coating agent.

2-1 Mycelium Preparation Step

[0070] In the mycelium preparation step S102, a mycelium containing hyphae is first prepared. The mycelium is formed, for example, by collecting a large number of hyphae and forming or paper-making the hyphae into a sheet. The mycelium may have a flat plate shape or may be formed into a predetermined shape. The hyphae may be a defibrated material of the mushroom mycelium. Accordingly, the mycelium can be formed into a desired shape regardless of the shape of mushroom mycelium before defibration. A method for imparting mechanical energy, for example, is used for defibration of mushroom mycelium. In particular, by using a defibration machine, a mushroom mycelium can be defibrated to obtain hyphae while reducing significant damage to the hyphae. A defibrating method may be a wet method, but a dry method is preferably used. The dry method refers to a method of defibrating in air such as the atmosphere, rather than in a liquid such as water. As the defibration machine, an impeller mill capable of dry defibration is preferably used.

[0071] The mycelium may be formed, for example, by mixing hyphae, starch, a plasticizer, a crosslinking agent, and a fiber, and heating the mixture. In this case, various stirrers are used for mixing. Examples of the stirrer include a mechanical stirrer, an airflow stirrer, and an ultrasonic stirrer. A timing of mixing the above components may be the same for the components or may be different for the components. For example, two or more components may be simultaneously mixed, or the components may be sequentially mixed.

[0072] As the mycelium, a mycelium subjected to a treatment for improving abrasion resistance, water resistance, and flexibility may be prepared. Examples of the treatment for improving the abrasion resistance, water resistance, and flexibility include mixing with a fiber, immersion in a starch solution, immersion in a solution containing at least one of glycerin and oil, addition of a crosslinking agent, and the ozone treatment as described above.

[0073] As the mycelium, a mycelium obtained by culture may be used. When inoculum of the hyphae is inoculated into the culture medium and cultured, a mycelium in which the grown hyphae are spread over the entire culture medium can be obtained.

[0074] The culture medium may be a solid culture medium or a liquid culture medium.

[0075] The culture medium may have a component that improves abrasion resistance, water resistance, and flexibility. Examples of the component that improves abrasion resistance, water resistance, and flexibility include starch, a plasticizer, a crosslinking agent, and a fiber, as described above. In addition to these components, the culture medium may contain a nutrient, a gelling agent, and the like necessary for growth of mushroom hyphae. Meanwhile, starch may be used as a nutrient.

[0076] In a case of a solid culture medium, it is preferable to use a culture medium formed into a sheet shape, so that secondary processing can be simplified or omitted, and a sheet-shaped mycelium can be efficiently produced. The liquid culture medium includes, for example, starch, a plasticizer, a crosslinking agent, and fibers dispersed in a dispersion medium such as water. When a liquid culture medium is used, the medium is relatively easy to manage and handle because the culture medium is liquid. In the liquid culture medium, since an operation such as stirring is possible, it is easy to make culture uniform and speed up.

[0077] Culture conditions such as a culture temperature, a culture time, and humidity are appropriately set in accordance with a type of the hyphae or the culture medium.

[0078] In the mycelium obtained by culture, hyphae are three-dimensionally connected to each other. Accordingly, it is possible to impart better flexibility to the mycelium structure 100.

[0079] The mycelium obtained by culture may be formed as necessary. Accordingly, a mycelium having a desired shape can be obtained.

2-2 Coating Step

[0080] Next, in the coating step S104, the polylactic acid coating agent is applied to one surface of the prepared mycelium so as to form a uniform film. Then, a part of the applied polylactic acid coating agent does not permeate and remains on the surface of the mycelium, and a part of the applied polylactic acid coating agent permeates into the mycelium. The polylactic acid coating agent permeates into only a part of mycelium and does not permeate into the whole mycelium. That is, there is a portion of the mycelium that is not permeated with the polylactic acid coating agent.

[0081] The polylactic acid coating agent is a liquid containing a polylactic acid. More specifically, the polylactic acid coating agent is preferably a dispersion containing a polylactic acid and water. Any additive may be added to the polylactic acid coating agent as necessary. Examples of the additive include a condensing agent, an antioxidant, a stabilizer, and a lubricant.

[0082] A method of applying the coating agent is not particularly limited, and for example, a bar coater, dipping, a blade, or a spray can be used.

2-3 Drying Step

[0083] In the drying step S106, the mycelium coated with the polylactic acid coating agent is dried. The drying is performed under atmospheric pressure. The drying is preferably performed at 23C (room temperature) or higher to 100C or lower. The higher the temperature during drying, the lower the flexibility of the mycelium structure 100, and thus it is preferable to dry at a low temperature as much as possible.

[0084] When moisture is evaporated in the drying step S106, a portion remaining on the surface of the mycelium that is not permeated with the polylactic acid coating agent becomes the polylactic acid coating layer 20. A portion where the polylactic acid coating agent permeates into the mycelium is the polylactic acid permeation layer 12. A portion of the mycelium into which the polylactic acid coating agent is not permeated is the base portion 11. The base portion 11 and the polylactic acid permeation layer 12 constitute the mycelium material 10.

[0085] An amount of permeation of the polylactic acid coating agent can be adjusted by changing drying conditions. That is, a ratio of a thickness of each layer in the mycelium structure 100 can be adjusted by changing the drying conditions.

[0086] For example, the shorter a time from application of the polylactic acid coating agent to start of drying, the shorter a time for the polylactic acid coating agent to permeate into the mycelium. Then, the amount of permeation into the mycelium decreases. Therefore, the polylactic acid permeation layer 12 becomes thin, and the polylactic acid coating layer 20 becomes thick.

3 Effects of Embodiment

[0087] As described above, the mycelium structure according to the embodiment includes: the mycelium material including the base portion having hyphae and the polylactic acid permeation layer in which a polylactic acid is permeated into the hyphae; and the polylactic acid coating layer provided on the surface of the polylactic acid permeation layer and thicker than the polylactic acid permeation layer.

[0088] According to such a configuration, the mycelium structure having abrasion resistance, water resistance, and excellent flexibility is obtained.

[0089] In the mycelium structure according to the embodiment, the thickness of the polylactic acid coating layer is preferably 5.0 m or more and 100.0 m or less.

[0090] According to such a configuration, the abrasion resistance and water resistance of the mycelium structure can be improved, and the flexibility can be further improved.

[0091] In the mycelium structure according to the embodiment, the thickness of the polylactic acid permeation layer is preferably more than 0.0 m and 30.0 m or less.

[0092] According to such a configuration, it is possible to improve the flexibility while improving the abrasion resistance and the water resistance of the mycelium structure.

[0093] In the mycelium structure according to the embodiment, the polylactic acid is preferably a biodegradable polylactic acid.

[0094] According to such a configuration, an environmental load can be reduced by carbon neutrality of a raw material for the mycelium structure.

[0095] In the mycelium structure according to the embodiment, the mycelium material preferably further contains a fiber.

[0096] According to such a configuration, the abrasion resistance and water resistance of the mycelium structure can be further enhanced.

[0097] In the mycelium structure according to the embodiment, the mycelium material preferably contains at least one of glycerin and oil.

[0098] According to such a configuration, the flexibility of the mycelium structure can be further enhanced.

[0099] In the mycelium structure according to the embodiment, in the stress-strain curve indicating the relationship between the stress (MPa) applied by the tensile test and the strain (%) at that time, the maximum strain in the elastic region is preferably 4.0% or more and 40.0% or less.

[0100] According to such a configuration, the flexibility of the mycelium structure can be particularly improved.

[0101] In the mycelium structure according to the embodiment, the mycelium material may include mycelium formed of hyphae connected in a three-dimensional shape.

[0102] According to such a configuration, since the hyphae are three-dimensionally connected to each other, better flexibility can be imparted to the mycelium structure.

[0103] In the mycelium structure according to the embodiment, the mycelium material may contain defibrated hyphae.

[0104] According to such a configuration, the mycelium can be formed into a desired shape regardless of the shape of mushroom mycelium before defibration.

[0105] Although the mycelium structure according to the present disclosure has been described based on the preferred embodiment, the present disclosure is not limited thereto. For example, the mycelium structure according to the present disclosure may be what is obtained by replacing each unit of the embodiment described above with any component having a similar function, or what is obtained by adding any constituent to the embodiment described above.

Examples

[0106] Next, specific examples of the present disclosure will be described, and the present disclosure is not limited thereto. A treatment and measurement in the following Examples were performed at room temperature (23C) for those not showing a temperature condition.

4 Production of Mycelium Structure

4-1 Example 1

[0107] First, a mycelium obtained by culture inoculum (Ganoderma lucidum) was subjected to an abrasion resistance and water resistance imparting treatment. As the abrasion resistance and water resistance imparting treatment, a treatment was performed in which the mycelium was immersed in a starch solution at room temperature for 160 minutes, then pulled up, and heated at 100C to evaporate moisture. An aqueous starch solution having a concentration of 20% by mass was used as the starch solution.

[0108] Next, a flexibility imparting treatment was performed on the mycelium after the abrasion resistance and water resistance imparting treatment. As the flexibility imparting treatment, a treatment was performed in which the mycelium was immersed in a solution containing glycerin at room temperature, glycerin was contained between hyphae, and then heated to remove moisture. A glycerin solution having a concentration of 20% by mass was used as the glycerin solution.

[0109] Next, the polylactic acid coating agent was thinly and uniformly applied from one surface to the mycelium subjected to the flexibility imparting treatment, and was allowed to permeate. A bar coater was used for coating. As the polylactic acid coating agent, a dispersion containing a polylactic acid and water was used.

[0110] Thereafter, the mycelium coated with the polylactic acid coating agent was placed in a thermostatic chamber and dried at 80C. As described above, the mycelium structure in Example 1 was obtained.

4-2 Examples 2 to 4 and Comparative Examples 1 to 3

[0111] Mycelium structures in Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 except that production conditions of the mycelium structure were changed as shown in FIG. 3 (Table 1). The abrasion resistance, water resistance, and flexibility imparting treatments to mycelium were not performed only in Example 5.

5 Evaluation of Mycelium Structure

5-1 Water Resistance and Abrasion Resistance

[0112] First, the mycelium structure was punched out to prepare a test piece. A white cotton cloth for friction was wetted with water until the cloth was wetted to about 100% by mass. Next, using a Gakushin type friction fastness tester AB-301 (manufactured by Tester Sangyo Co., Ltd.), the white cotton cloth for friction attached to a friction element was rubbed against the test piece under a load of 0.067 MPa. The number of times the test piece was rubbed until the test piece was broken was measured, and water resistance and abrasion resistance were evaluated according to the following evaluation criteria. Evaluation results are shown in Table 1.

[0113] A: The number of times of friction until the test piece is broken is 100 or more.

[0114] B: The number of times of friction until the test piece is broken is 50 or more and 100 or less.

[0115] C: The number of times of friction until the test piece is broken is 10 or more and 49 or less.

[0116] D: The number of times of friction until the test piece is broken is less than 10 times.

5-2 Flexibility

[0117] First, the mycelium structure was punched out to prepare a test piece. Next, a tensile test according to JIS P 8113: 2006 was performed on the test piece using Autograph AGS-5kNX (produced by Shimadzu Corporation). A stress-strain curve indicating a relationship between a stress (MPa) applied by the tensile test and a strain (%) at that time was created, and an elastic region was specified. The maximum strain in the elastic region was evaluated based on the following evaluation criteria, and the flexibility was evaluated. The higher a numerical value of the maximum strain in the elastic region, the better the flexibility. Evaluation results are shown in Table 1.

[0118] A: The maximum strain in the elastic region is 8.0% or more and 15.0% or less.

[0119] B: The maximum strain in the elastic region is 6.0% or more and less than 8.0%.

[0120] C: The maximum strain in the elastic region is 2.0% or more and less than 6.0%.

[0121] D: The maximum strain in the elastic region is less than 2.0%.

[0122] As is clear from Table 1, the mycelium structures in Examples had abrasion resistance and water resistance and were excellent in flexibility. In contrast, in the mycelium structures in Comparative Examples, satisfactory results were not obtained.