Laminate for algae culture, algae culture sheet, method for recovering culture layer, and method for producing laminate for algae culture

Abstract

The present disclosure provides a laminate for algae culture to be used for culturing algae, comprising a base material and an adhesive layer containing an adhesive that is arranged on at least one surface of the base material.

Description

A laminate for algal culture, an algal culture sheet, a method for recovering the culture layer, and a method for producing an algal culture laminate.

[0001] This disclosure relates to a laminate for algal culture, an algal culture sheet, a method for recovering the culture layer, and a method for producing a laminate for algal culture.

[0002] Algae are widely cultivated for the production of supplements, cosmetics, aquatic feed ingredients, and oils suitable for biofuels. Algae are broadly classified into microalgae and macroalgae. Examples of microalgae include Chlorella, Spirulina, and Euglena. Examples of macroalgae include wakame and kelp.

[0003] Traditionally, liquid culture has been known as a method for culturing algae, but there is a need to improve the cultivation efficiency and reduce costs in the cultivation process, as well as reduce costs and energy in the post-processing steps of collecting and concentrating the cultured algae. The effectiveness of solid-phase surface culture has been reported to address these problems. Solid-phase surface culture is a method in which algae are attached to the surface of a support material such as a cloth or paper sheet and cultured.

[0004] Patent Document 1 discloses an algae culture sheet comprising a base layer and a culture layer laminated on the base layer and configured for culturing algae. According to this algae culture sheet, the culture layer is laminated on the base layer, and compared to the case where the algae culture sheet is composed of the culture layer alone, the strength of the algae culture sheet is higher, thus improving the handling of the algae culture sheet.

[0005] Japanese Patent Publication No. 2023-128646

[0006] The use of the aforementioned support sheets is expected to reduce costs and energy consumption in the cultivation and post-processing stages. However, conventional support sheets have poor algal adhesion during the seeding and early stages of cultivation, which can reduce cultivation efficiency. Therefore, there is room for improvement in algal retention. Furthermore, a method for recovering the algae after cultivation has not yet been established.

[0007] This disclosure has been made in view of the above circumstances, and its main purpose is to provide a laminate for algae cultivation that has excellent algae retention properties and allows for easy collection of cultured algae.

[0008] One embodiment of the present disclosure provides an algal culture laminate for use in cultivating algae, comprising a substrate and an adhesive layer containing an adhesive disposed on at least one surface of the substrate.

[0009] One embodiment of the present disclosure provides an algae culture sheet comprising the above-described algae culture laminate and a culture layer disposed on the adhesive layer side of the algae culture laminate and containing cultured algae.

[0010] Another embodiment of this disclosure provides a method for recovering a culture layer, which involves peeling the adhesive layer and the culture layer from the substrate of the algae culture sheet described above.

[0011] Another embodiment of the present disclosure provides a method for producing the above-described algal culture laminate, wherein the adhesive layer is formed by a coating method or a transfer method.

[0012] Another embodiment of the present disclosure provides a method for producing the above-described algal culture laminate, wherein the charge-retaining layer is formed by a coating method or a transfer method.

[0013] This disclosure provides a laminate for algae cultivation that offers excellent algae retention and allows for easy harvesting of cultured algae.

[0014] This is a schematic cross-sectional view showing an example of a laminate for algae cultivation in this disclosure. This is a schematic plan view and schematic cross-sectional view showing an example of a laminate for algae cultivation in this disclosure. This is a schematic plan view and schematic cross-sectional view showing an example of a laminate for algae cultivation in this disclosure. This is a schematic plan view and schematic cross-sectional view showing an example of a laminate for algae cultivation in this disclosure. This is a schematic plan view and schematic cross-sectional view showing an example of a laminate for algae cultivation in this disclosure. This is a schematic cross-sectional view showing an example of a laminate for algae cultivation in this disclosure. This is a schematic cross-sectional view showing an example of an algae cultivation sheet in this disclosure. This is a schematic cross-sectional view illustrating a cultivation method using the laminate for algae cultivation in this disclosure. This is a schematic diagram illustrating the installation configuration of the laminate for algae cultivation in this disclosure. This is a schematic cross-sectional view of the process of recovering the culture layer from the algae culture sheet in this disclosure. This is a schematic diagram of a cultivation apparatus for manufacturing the algae culture sheet and recovering the culture layer in this disclosure.

[0015] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, the drawings may be schematically represented in terms of width, thickness, shape, etc. of each part compared to the actual form in order to make the explanation clearer, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0016] In this specification, when describing a configuration in which one member is placed on top of another member, unless otherwise specified, the terms "on top" or "below" include both cases: one in which the other member is placed directly above or below the other member so as to be in contact with it, and another in which the other member is placed above or below the other member via yet another member. Similarly, when describing a configuration in this specification in which one member is placed on the surface of another member, unless otherwise specified, the terms "on the surface" or "on the surface" include both cases: one in which the other member is placed directly above or below the other member so as to be in contact with it, and another in which the other member is placed above or below the other member via yet another member.

[0017] The following describes in detail the algal culture laminate, algal culture sheet, method for recovering the culture layer, and method for manufacturing the algal culture laminate as described in this disclosure.

[0018] A. Stacked Algae Culture Structure Figures 1(a) and 1(b) are schematic cross-sectional views showing an example of a stacked algae culture structure in this disclosure. As shown in Figures 1(a) and 1(b), the stacked algae culture structure 10 in this disclosure comprises a base material 1 and an adhesive layer 2 disposed on at least one surface of the base material 1. As shown in Figure 1(a), the adhesive layer 2 may be disposed on one surface 1a of the base material 1, or as shown in Figure 1(b), it may be disposed on both surfaces 1a and 1b of the base material 1.

[0019] The algal culture laminate in this disclosure is used for cultivating algae. That is, it is an algal culture laminate used to manufacture an algal culture sheet having a culture layer containing cultured algae. Figures 8(a) and 8(b) are schematic cross-sectional views of an algal culture sheet manufactured using the algal culture laminate 10 shown in Figures 1(a) and 1(b), respectively. As shown in Figures 8(a) and 8(b), the algal culture sheet 20 has an algal culture laminate 10 and a culture layer 4 containing cultured algae, which is arranged on the adhesive layer 2 side of the algal culture laminate 10. Note that, as shown in Figure 8(b), when the adhesive layer 2 is arranged on both sides 1a and 1b of the substrate 1, the adhesive layer 2 side of the algal culture laminate 10 refers to both sides 10a and 10b of the algal culture laminate 10.

[0020] The algal culture laminate in this disclosure has an adhesive layer on at least one side of the substrate, so that the adhesive force of the adhesive layer provides good retention of algae during the seeding and early stages of the culture process. Therefore, it is possible to suppress the flow of seed algae sown in the seed algae process and algae cultured in the early stages of the culture process, thereby improving culture efficiency. For example, even when culturing with the algal culture laminate suspended or tilted, the outflow of algae can be suppressed. After the early stages of the culture process, algae form aggregates with the mucus they produce, so the retention of algae during the seeding and early stages of the culture process is important for improving culture efficiency. Cell culture has four phases: the induction phase, the logarithmic growth phase, the stationary phase, and the death phase. In this specification, the early stages of the culture process refer to the induction phase and the logarithmic growth phase.

[0021] Furthermore, as the algal culture progresses, the adhesive layer in this disclosure reaches an equilibrium state in terms of its water content, becoming a self-supporting membrane with a certain degree of membrane strength. In addition, the adhesive force of the adhesive layer decreases as the adhesive is physically washed away or consumed as a carbon source during the culture process. Therefore, by providing a starting point for delamination between the adhesive layer and the substrate and pulling, it becomes easy to detach the culture layer from the substrate together with the adhesive layer without tearing the membrane (adhesive layer) itself.

[0022] The following describes the various components of the algal culture laminate in this disclosure.

[0023] 1. Substrate The algal culture laminate in this disclosure has a substrate. The algal culture laminate in this disclosure has improved strength due to the presence of the substrate. For example, it becomes possible to transport the algal culture laminate using a roll-to-roll method. That is, it becomes possible to perform algal culture while transporting the algal culture laminate using a roll-to-roll method. As a result, the productivity of algal culture using the algal culture laminate can be increased.

[0024] (1) The permeable substrate is preferably permeable to water. This is because the permeable substrate allows for a uniform supply of culture medium from the substrate to each region of the surface on the adhesive layer side of the algae culture laminate. In this specification, "permeable to water" means that the water absorption time measured in accordance with the drop method specified in JIS L 1907 (2010) is, for example, 300 seconds or less. Specifically, one drop of water is dropped onto the surface of the substrate from a height of 10 cm, and the water absorption time (seconds) from when the water droplet reaches the surface of the substrate until the specular reflection of the water droplet disappears is measured five times, and the average value is calculated. The water absorption time of the substrate is preferably 100 seconds or less, and more preferably 60 seconds or less. The shorter the time, the faster the water absorption and the better the permeability. On the other hand, the water absorption time of the substrate is, for example, 1 second or more. The measurement conditions are a temperature of 23 ± 2°C and a relative humidity of 50 ± 5%.

[0025] (2) Shape: In terms of having the above-mentioned water permeability, the base material is preferably a porous base material. The porous base material contains a plurality of voids inside. These voids are usually preferably in communication in the thickness direction.

[0026] The pore size of the voids in the porous substrate is not particularly limited, but is preferably 1000 μm or less, more preferably 100 μm or less, and especially preferably 10 μm or less. If the pore size is too large, when the adhesive layer is formed in a pattern, algae, especially microalgae, may enter the voids of the substrate, making recovery difficult. On the other hand, the pore size is preferably 0.01 μm or more, more preferably 0.1 μm or more, and especially preferably 1 μm or more. When the pore size is within the above range, water permeability is improved. In this specification, the "pore size" of the voids in the porous material is the average value of the minimum pore size of 10 pores observed when a 1000x electron microscope (SEM) image is obtained from a cross-section obtained by cutting the porous material along a direction perpendicular to the thickness direction.

[0027] The porosity of the porous substrate is not particularly limited, but is preferably 10% or more, and more preferably 20% or more. A porosity within this range improves water permeability. On the other hand, the porosity of the porous substrate is preferably 70% or less, and more preferably 50% or less. If the porosity is too high, when the adhesive layer is formed in a pattern, algae, especially microalgae, may enter the voids of the substrate, making recovery difficult.

[0028] In this disclosure, porosity refers to the proportion of voids in a porous substrate and can be calculated as follows: Pv (%) = {(Va - Vt) / Va} × 100 (1) Pv (%): Porosity of the porous substrate (volume %) Va: Apparent volume of the porous substrate Vt: Theoretical volume of the porous substrate Here, Va can be calculated from the length, width, and thickness of the porous substrate, and Vt can be calculated from the weight of the porous substrate, the weight ratio of the constituent materials, and the true specific gravity of each constituent material.

[0029] As the porous substrate, sheet-like materials such as paper, nonwoven fabric, woven fabric, and foamed sheets can be used.

[0030] Examples of paper include coated paper and uncoated paper. Examples of paper materials include natural pulp such as wood pulp and non-wood pulp, and artificial pulp such as synthetic fiber pulp.

[0031] The fibers constituting the nonwoven or woven fabric can include fibers made from various resin materials such as polyethylene, polypropylene, polymethacrylate, polymethyl methacrylate, polymethyl acrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, and nylon; fibers such as rayon, cotton, and wool; and inorganic fibers such as glass fibers, alumina fibers, carbon fibers, and ceramic fibers. The fibers may also be made from plant-derived biomass materials. Examples of biomass material fibers include plant fibers such as sugarcane and corn, and polylactic acid fibers.

[0032] Examples of materials for foamed sheets include various resin materials similar to those mentioned above.

[0033] Other examples of base materials include perforated metal, which has multiple through-holes formed in a metal sheet, and mesh (wire mesh) made by weaving together many metal wires. Examples of metals that make up the metal sheet and wire mesh include various metals such as copper, stainless steel, aluminum, brass, iron, titanium, and platinum, as well as alloys of these metals. Furthermore, the metal sheet and wire mesh may be plated with various metals such as zinc plating and chromium plating on their surfaces.

[0034] The base material is preferably a hydrophilic material. In particular, when the pore size or porosity of the porous base material is smaller than the above range, using a hydrophilic material as the base material improves water permeability. Hydrophilic polymers can be used as hydrophilic materials. A hydrophilic polymer refers to a polymer that contains a carbon component and has hydrophilic functional groups in the main chain or side chains of the polymer. Hydrophilic polymers are preferably water-soluble polymers containing carbon-oxygen bonds that are water-soluble or water-swellable. Specific examples of hydrophilic polymers include hydrogel polymers such as polyalkylene glycol, polyvinylpyrrolidone, polypropylene glycol, polyvinyl alcohol, polyethyleneimine, polyallylamine, polyvinylamine, polyvinyl acetate, polyacrylic acid, poly(meth)acrylamide, and poly-N-isopropylacrylamide, as well as copolymers of these with other monomers and graft polymers.

[0035] The substrate material may be a hydrophobic material. Examples of substrates containing hydrophobic materials include acrylic resin, epoxy resin, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, polytetrafluoroethylene, and polydimethylsiloxane. When the substrate contains a hydrophobic material, it is preferable that the surface of the substrate is treated to exhibit hydrophilicity. That is, it is preferable that the substrate has a surface treatment layer on the surface facing the adhesive layer. Examples of such treatments include corona treatment and plasma treatment.

[0036] (3) The thickness of the base material is, for example, 0.001 mm or more, preferably 0.01 mm or more. By setting the thickness of the base material within the above range, the strength of the laminated body for algae culture is improved. The thickness of the base material is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 1 mm or less. By setting the thickness of the base material within the above range, a decrease in water permeability can be suppressed.

[0037] (4) The base material may also serve as a charge holding layer. That is, the surface of the base material may be positively or negatively charged in water. For example, by using a polymer type charge control agent described later as the material constituting the porous base material, or by performing a treatment of introducing a functional group that is positively charged in water described later into the porous base material, the surface of the base material can be positively or negatively charged.

[0038] 2. Adhesive layer The laminated body for algae culture in the present disclosure has an adhesive layer disposed on at least one surface of the base material. By having the adhesive layer, the laminated body for algae culture in the present disclosure has good retention of algae in the seeding step and the initial stage of the culture step due to the adhesive force of the adhesive layer. Furthermore, the adhesive layer in the present disclosure becomes a self-supporting film with a certain film strength when the water content rate of the film itself reaches an equilibrium state over time during the culture of algae. Therefore, by providing a peeling trigger between the adhesive layer and the base material and pulling, it becomes easy to peel the culture layer from the base material together with the adhesive layer without breaking the film (adhesive layer) itself starting from that point.

[0039] As shown in FIG. 1(a), the adhesive layer 2 may be disposed on one surface 1a of the base material 1, or as shown in FIG. 1(b), it may be disposed on both surfaces 1a and 1b of the base material 1.

[0040] (1) Adhesive force The tack force on the surface of the adhesive layer is preferably, for example, 2 or more in ball number (the size of the ball [inch]: 1 / 16) at a slope of 20 degrees by the "Inclined Ball Tack Measurement Method" described in JIS Z 0237 (2022).

[0041] As a method for measuring tack (adhesive force), the "Inclined Ball Tack Measurement Method" described in JIS Z 0237 (2022) is used. First, on the top of a triangular device equipped with an inclined plate with an inclination angle of 20 degrees, among 31 types of steel balls with a size of "ball designation" from 1 / 16 to 1 in JIS B 1501 (2009) and made of two types of high-carbon chromium bearing steel materials specified in JIS G 4805 (2019), excluding 5 / 64, 7 / 64, 9 / 64, 15 / 64, and 17 / 64, are placed. The steel balls roll on the running path (100 mm) and stop on the adhesive surface (100 mm) of the test piece following the running path. The numerical value 32 times the "ball designation" is called the "ball number", and the test result is represented by the maximum ball number that stopped. The measurement environment is an environment with a temperature of 23 ± 2°C and a relative humidity of 50 ± 5%. This method is also called the J. Dow method and is widely popular in Japan.

[0042] (2) Materials The adhesive layer in the present disclosure is roughly classified into an embodiment containing seaweed seeds (First Embodiment) and an embodiment not containing seaweed seeds (Second Embodiment).

[0043] (a) First Embodiment The adhesive layer in this embodiment contains an adhesive and seaweed seeds. Since the adhesive layer contains seaweed seeds, algae can be grown from the seaweed seeds contained in the adhesive layer, so the seeding process can be omitted.

[0044] (i) The adhesive layer has an adhesive, for example. As the adhesive, an adhesive derived from natural ingredients is preferred because it has low toxicity to algae. Examples of adhesives derived from natural ingredients include potato starch, tapioca flour, tremel gum (also known as white fungus extract), agar, seaweed cellulose (also known as cellulose), brown algae extract (also known as brown algae mucilage), pectin, guar gum, guar gum enzyme hydrolysate, carob bean gum (also known as locust bean gum), gluten, konjac extract (also known as glucomannan), sweet potato cellulose (also known as cellulose), soybean polysaccharides (also known as soybean hemicellulose), nata de coco (also known as brewed cellulose, fermented cellulose, cellulose), mannan, alginic acid, sodium alginate, calcium alginate, ammonium alginate, potassium alginate, okra, gelatin, rennet casein, and propylene alginate. Examples include glycoglycol esters, gluten hydrolysates, acetylated adipate cross-linked starch, acetylated oxidized starch, acetylated phosphorylated cross-linked starch, sodium octenyl succinate starch, starch acetate, oxidized starch, sodium starch glucose, hydroxypropyl phosphate cross-linked starch, hydroxypropyl starch, phosphate cross-linked starch, phosphorylated starch, gum arabic, carrageenan (also known as processed Eukema algae, purified carrageenan, Eukema algae powder), methylcellulose, sodium carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC), microfibrous cellulose, sodium polyacrylate, tara gum, xanthan gum, curdlan, and dextran. These adhesives may be used individually or in combination of two or more. Furthermore, it is preferable that the adhesive is a nutrient that can be used by algae as a carbon source.

[0045] In this disclosure, gelatin, tara gum, alginate-based compounds, and xanthan gum are preferred because they easily provide the aforementioned adhesive strength.

[0046] (ii) Seed algae The adhesive layer in this embodiment contains seed algae. That is, seed algae are seeded in the adhesive layer. In this specification, seed algae refers to microalgae or macroalgae used at the start of cultivation, and refers to microalgae or macroalgae that serve as the basis for culturing microalgae or macroalgae in the cultivation process.

[0047] If the algae are microalgae, the cell density in the adhesive layer composition is, for example, 1 × 10⁻⁶. １５ [cells / mL] or less, 1 × 10 １２ It is preferable that the cell density is [cells / mL] or less. If the cell density in the adhesive layer composition is too high, the amount of light supplied to each algal cell will decrease, slowing down growth. On the other hand, the cell density in the adhesive layer composition is, for example, 1 [cells / mL] or more, and 1 × 10⁻⁶ ３ [cells / mL] or higher is preferred, 1 × 10 ５ [cells / mL] is more preferable. At the start of culture, as long as there is at least one cell in the culture area, proliferation is possible if given enough time, so there are no particular restrictions. However, if the cell density in the adhesive layer composition is too low, it will take time to obtain the predetermined amount of culture layer, reducing productivity. Assuming that the cell size is 1 μm and the thickness of the thickening agent layer is also 1 μm, [cells / mL] is pseudo-[cells / mL]. ２ This becomes equivalent to the number of cells per unit area of ​​the adhesive layer.

[0048] A sticky layer containing algae is obtained by applying a sticky layer composition, which is made by mixing a cell suspension (a suspension containing algae and culture medium) and a thickening agent solution containing an adhesive in any ratio, onto a substrate. The cell density in the sticky layer composition is calculated by determining the number of cells (cells / mL) in the cell suspension and the solid content ratio of the adhesive component in the thickening agent solution. The number of cells in the cell suspension (algae suspension) may be directly counted. Alternatively, if a calibration curve (conversion table) for the turbidity of the cell suspension and the number of cells (cells / mL) is available, it can be simply determined from the turbidity measurement. Turbidity measurement is performed using a spectrophotometer to determine the transmittance of the cell suspension at wavelengths of 300 to 750 nm. The specific wavelength is selected according to the type of algae. The solid content ratio of the thickening agent is calculated using the following formula: (weight of thickening agent component) / {(weight of thickening agent component) + (weight of culture medium or water without cells)}

[0049] (iii) The adhesive layer may also function as a charge-holding layer as described later. In this case, the adhesive layer may have a charge control agent or a polymer-type charge control agent as described later. Furthermore, if the adhesive layer has self-supporting properties, the adhesive layer may function as a substrate.

[0050] (iv) Formation Method The adhesive layer of the first embodiment can be formed by, for example, applying a first adhesive layer composition, which is obtained by mixing a suspension containing algal cells as seed algae with an adhesive, onto a substrate and drying as necessary. In other words, the adhesive layer of the first embodiment can be obtained by a coating method. Examples of coating methods include gravure printing, die coating, and silk screen printing.

[0051] The adhesive content in the first adhesive layer composition is, for example, 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1.0% by mass or more. By having an adhesive content in the first adhesive layer composition within the above range, an adhesive layer of sufficient thickness can be obtained after coating, and sufficient adhesion to algae can be obtained. The adhesive content in the first adhesive layer composition is, for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less. If the adhesive content in the first adhesive layer composition is higher than the above range, the viscosity will increase, making it difficult to coat the first adhesive layer composition uniformly.

[0052] (b) Second embodiment The adhesive layer in this embodiment includes an adhesive. The type of adhesive is the same as the type of adhesive in the composition for the first adhesive layer.

[0053] The adhesive layer of the second embodiment can be formed, for example, by applying a second adhesive layer composition containing an adhesive and a culture medium onto a substrate. That is, the adhesive layer of the second embodiment can be obtained by a coating method. Examples of coating methods include gravure printing and die coating. The content of the adhesive in the second adhesive layer composition is the same as the content of the adhesive in the first adhesive layer composition.

[0054] (3) When there is no charge-holding layer between the substrate and the adhesive layer, the thickness of the adhesive layer is, for example, 0.1 μm or more, preferably 1 μm or more, and more preferably 5 μm or more. By setting the thickness of the adhesive layer within the above range, sufficient adhesive force to algae can be obtained. The thickness of the adhesive layer is, for example, preferably 10 mm or less, more preferably 1 mm or less, and even more preferably 0.1 mm or less. By setting the thickness of the adhesive layer within the above range, when the culture layer is recovered together with the adhesive layer after the culture process, the proportion of the adhesive layer in the recovered amount decreases, making it possible to obtain relatively high-purity algae while increasing the recovery efficiency.

[0055] When a charge-retaining layer, described later, is present between the substrate and the adhesive layer, a thinner adhesive layer is preferable. In this case, the thickness of the adhesive layer is preferably 10 mm or less, more preferably 1 mm or less, and even more preferably 0.1 mm or less. By setting the thickness of the adhesive layer within the above range, a decrease in the electrostatic adsorption force of algae by the charge-retaining layer can be suppressed. On the other hand, when a charge-retaining layer, described later, is present between the substrate and the adhesive layer, the thickness of the adhesive layer is, for example, 0.1 μm or more, preferably 1 μm or more, and more preferably 5 μm or more. By setting the thickness of the adhesive layer within the above range, sufficient adhesive strength can be obtained.

[0056] (4) The water-permeable adhesive layer is preferably water-permeable. The adhesive layer composed of the adhesive described above is usually water-permeable. The water absorption time of the adhesive layer is, for example, 300 seconds or less, preferably 100 seconds or less, and more preferably 60 seconds or less. The shorter the time, the faster the water absorption and the better the water permeability. On the other hand, the water absorption time of the adhesive layer is, for example, 1 second or more. The measurement conditions are a temperature of 23±2℃ and a relative humidity of 50±5%.

[0057] (5) As shown in Figures 1(a) and 1(b), the adhesive layer may be placed over the entire surface of at least one side of the substrate. When the adhesive layer is placed over the entire surface, the growth of algae tends to be more uniform in the planar direction of the algae culture laminate. However, if the surface of the substrate has an uneven shape, it may be difficult to form the adhesive layer by coating. In such cases, the adhesive layer can be formed on the uneven substrate by transfer using a transfer sheet having a release film and a transfer layer containing the adhesive layer. That is, the adhesive layer (the adhesive layer of the first and second embodiments) may be formed by a transfer method.

[0058] On the other hand, as shown in Figures 2(a), 2(b), 3(a), and 3(b), the adhesive layer 2 may be arranged on a portion of at least one surface of the substrate 1. Note that Figure 2(b) is a cross-sectional view taken along line A-A in Figure 2(a), and Figure 3(b) is a cross-sectional view taken along line A-A in Figure 3(a). That is, at least one surface of the substrate may have a portion where the adhesive layer is provided and a portion where the adhesive layer is not provided. By arranging the adhesive layer 2 on a portion of at least one surface of the substrate 1 in this way, areas where algae are easily retained and can grow easily, and areas where algae are not easily retained and cannot grow easily are created. Therefore, as shown in Figures 2(c) and 3(c), the culture layer 4 will mainly grow on the adhesive layer 2. Specifically, if the adhesive layer is the first embodiment of the adhesive layer, the culture layer will grow easily on the adhesive layer. If the adhesive layer is the second embodiment of the adhesive layer, algae will be easily seeded on the adhesive layer, and the culture layer will grow easily on the adhesive layer. When an adhesive layer is formed uniformly on the substrate, algal growth tends to be more uniform in the planar direction of the algal culture layer. As a result, light may not irradiate the culture layer near the substrate, which can reduce the growth rate. On the other hand, as shown in Figures 2(c) and 3(c), the culture layer 4 on the partially formed adhesive layer 2 is irradiated with light from the sides as well, so the growth rate does not decrease. Furthermore, because areas where algae can easily proliferate and areas where they cannot proliferate are created, in the case of algae that release valuable substances such as polysaccharides and carboxylic acids into the outside of their bodies, it may be possible to form channels for these valuable substances.

[0059] If an adhesive layer is placed on a portion of at least one surface of the substrate, the adhesive layer may be arranged in a pattern. Here, "pattern" means a design formed by regularly repeating the same shape, such as a grid, mesh, line, or dot pattern. For example, the adhesive layer 2 shown in Figures 2(a) to (c) is arranged in a dot pattern. The adhesive layer 2 shown in Figures 3(a) to (c) is arranged in a line pattern.

[0060] When the adhesive layers are arranged in a pattern, the width W21 of the adhesive layer is, for example, 0.1 μm or more, and may be 1.0 μm or more. On the other hand, the width W21 of the adhesive layer is, for example, 10 mm or less, and may be 1.0 mm or less. Also, the width W11 of the gap between adjacent adhesive layers is, for example, 0.01 μm or more, and may be 0.1 μm or more. On the other hand, the width W11 of the gap between adjacent adhesive layers is, for example, 10 mm or less, and may be 1 mm or less. The width W21 of the adhesive layer refers to the diameter if the plan view shape of the adhesive layer is circular, the major axis if it is elliptical, the length of the diagonal if it is rectangular, and the distance perpendicular to the stretching direction if it is linear, and is the average value measured at 10 locations. The width W11 of the gap between the adhesive layers refers to the shortest distance between adjacent adhesive layers, and is the average value measured at 10 locations.

[0061] In the case of a laminate for algae cultivation in which the adhesive layer is arranged in a pattern, an algae cultivation sheet is obtained in which the patterned cultivation layer is arranged at positions corresponding to the pattern of the adhesive layer.

[0062] In this disclosure, the adhesive layer is arranged in a pattern on at least one surface of the substrate, and one or more pattern layers with a different composition from the adhesive layer may be arranged in at least a portion of the area other than the area where the adhesive layer is arranged. The one or more pattern layers may include, for example, one or more patterns of a low-tack layer with lower tack strength than the adhesive layer, or a pattern of a valuable substance-adhering layer capable of absorbing or adsorbing valuable substances such as sugars and oils.

[0063] In this disclosure, as shown in Figure 4(a), the adhesive layer 2 is arranged on a portion of at least one surface of the substrate 1, and a low-tack layer 5 with a lower tack force than the adhesive layer may be arranged on at least a portion of the area other than the area where the adhesive layer 2 is arranged. The adhesive layer 2 and the low-tack layer 5 may each be arranged in a pattern. In the algae culture laminate 10 in which the adhesive layer 2 and the low-tack layer 5 are partially arranged on at least one surface of the substrate 1, as shown in Figures 4(b) and 4(c), the culture layer 4 will grow mainly on the adhesive layer 2. Since the culture layer 4 formed on the adhesive layer 2 is also irradiated with light from the side, the growth rate does not decrease. The low-tack layer is not particularly limited as long as the tack force of the surface is lower than the tack force of the surface of the adhesive layer. The tack force on the surface of the low-tack layer is less than or equal to, for example, ball number "32" (ball nominal size [inches]: 64 / 64) at a 40-degree inclination, according to the "inclined ball tack measurement method" described in JIS Z 0237 (2022).

[0064] In this case, the width W22 of the adhesive layer 2 is the same as the width W21 of the adhesive layer 2 described above. Also, the width W12 of the gap between adjacent adhesive layers is the same as the width W11 of the gap between adjacent adhesive layers described above. The width W5 of the low adhesive layer 5 may be the same as the width W12 of the gap between adjacent adhesive layers, or it may be smaller than the width W12 of the gap, but it is preferable that it be the same as the width W12 of the gap. This is because there is no risk of algae entering the gap between the low adhesive layer 5 and the adhesive layer 2, and the efficiency of algae collection is improved. Note that the width W5 of the low adhesive layer 5 and the width W12 of the gap being the same means that the difference between the width W12 and the width W5 (width W12 - width W5) is 1 μm or less.

[0065] Furthermore, in this disclosure, as shown in Figure 5(a), the adhesive layer 2 is arranged on a part of at least one surface of the substrate 1, and a valuable substance attachment layer 6, which is a layer capable of absorbing or adsorbing valuable substances V such as sugars and oils, may be arranged in at least a part of the area other than the area where the adhesive layer 2 is arranged. The adhesive layer 2 and the valuable substance attachment layer 6 may each be arranged in a pattern. In the algae cultivation laminate 10, in which the adhesive layer 2 and the valuable substance attachment layer 6 are each partially arranged on at least one surface of the substrate 1, as shown in Figures 5(b) and 5(c), valuable substances V accumulate on the valuable substance attachment layer 6, improving the recovery efficiency of valuable substances V. The valuable substance attachment layer varies depending on the type of valuable substance to be recovered, but may include, for example, synthetic resins such as polypropylene, sludge, natural materials such as cork, wool, and cellulose, and inorganic materials such as pumice and vermiculite. According to such a laminate for algae cultivation, an algae cultivation sheet can be obtained in which the valuable substance attachment layer absorbs or adsorbs valuable substances produced by algae cultivation.

[0066] In this case, the width W23 of the adhesive layer 2 is the same as the width W21 of the adhesive layer 2 described above. Also, the width W13 of the gap between adjacent adhesive layers is the same as the width W11 of the gap between adjacent adhesive layers described above. The width W6 of the valuable substance attachment layer 6 may be the same as the width W13 of the gap between adjacent adhesive layers, or it may be smaller than the width W13, but it is preferable that it be the same as the width W13. This is because there is no risk of algae entering the gap between the valuable substance attachment layer 6 and the adhesive layer 2, and the efficiency of algae recovery is improved. Note that the width W6 of the valuable substance attachment layer 6 and the width W13 of the gap are the same, which means that the difference between the width W13 and the width W6 (width W13 - width W6) is 1 μm or less.

[0067] Furthermore, in this disclosure, as shown in Figure 6(a), the adhesive layer 2A of the first embodiment (an adhesive layer containing adhesive and seed algae) is arranged on a part of at least one surface of the substrate 1, and the adhesive layers 2B of the second embodiment and the adhesive layer 2A of the second embodiment may be arranged in a pattern in at least a part of the area other than the area where the adhesive layer 2A of the first embodiment is arranged. In the algae culture laminate 10 in which the adhesive layer 2A of the first embodiment and the adhesive layer 2B of the second embodiment are partially arranged on at least one surface of the substrate 1, the seed algae are contained only in the adhesive layer 2A of the first embodiment. Therefore, if the seeding process is not performed, the culture layer 4 grows on the adhesive layer 2A of the first embodiment, as shown in Figure 6(b). The culture layer 4 formed on the adhesive layer 2A of the first embodiment is also irradiated with light from the side, so the growth rate does not decrease.

[0068] In this case, the width W2A of the adhesive layer 2A in the first embodiment is the same as the width W21 of the adhesive layer 2 described above. Also, the width W14 of the gap between adjacent adhesive layers 2A in the first embodiment is the same as the width W11 of the gap between adjacent adhesive layers described above. The width W2B of the adhesive layer 2B in the second embodiment may be the same as the width W14 of the gap between adjacent adhesive layers, or it may be smaller than the width W14, but it is preferable that it be the same as the width W14. This is because there is no risk of algae entering the gap between the adhesive layer 2A in the first embodiment and the adhesive layer 2B in the second embodiment, and the efficiency of algae collection is improved. Note that the width W2B of the adhesive layer 2B in the second embodiment and the width W14 of the gap are the same, which means that the difference between the width W14 and the width W2B (width W2B - width W14) is 1 μm or less.

[0069] As for the method of arranging the above-mentioned adhesive layer, low-adhesion layer, and valuable substance adhesion layer in a pattern, the adhesive layer may be formed in a pattern by adjusting the amount of adhesive layer composition applied, or the layers may be formed by applying the composition for each layer in a solid form and then shaping it.

[0070] 3. Charge-Retaining Layer As shown in Figures 7(a) and 7(b), the algae culture laminate 10 in this disclosure may have a charge-retaining layer 3 disposed between the substrate 1 and the adhesive layer 2. The charge-retaining layer is a layer whose surface is positively or negatively charged in water. The positive or negative charge is appropriately selected depending on the type of algae. Algae are generally positively or negatively charged in water. Because the charge-retaining layer has a charge opposite to that of the algae, the algae are electrostatically adsorbed to the adhesive layer. Therefore, in the seeding and culturing processes, the seeded and cultivated algae adhere due to the adhesive force of the adhesive layer and electrostatic adsorption by the charge-retaining layer, resulting in an algae culture laminate with further improved algae retention.

[0071] As shown in Figure 7(a), the charge-retaining layer 3 may be formed on the entire surface of at least one surface of the substrate 1. Alternatively, it may be formed on a portion of at least one surface of the substrate 1. In this case, as shown in Figures 7(b) and 7(c), the charge-retaining layer 3 may be arranged in a pattern. As shown in Figure 7(b), the adhesive layer 2 may be placed only on the upper surface of the charge-retaining layer 3, or as shown in Figure 7(c), the adhesive layer 2 may be arranged to cover the upper and side surfaces of the charge-retaining layer 3. By covering the upper and side surfaces of the charge-retaining layer 3, the electrostatic attraction force provided by the charge-retaining layer can be efficiently obtained.

[0072] (1) Amount of charge When the surface of the charge-holding layer opposite to the substrate side is positively charged, the zeta potential of the above surface of the charge-holding layer in water is preferably greater than 0 mV and 100 mV or less. When the surface of the charge-holding layer opposite to the substrate side is negatively charged, the zeta potential of the above surface of the charge-holding layer in water is preferably -100 mV or more and less than 0 mV. The zeta potential of the surface of the charge-holding layer is a value measured using a zeta potential meter. For example, the product name "ELSZneo" (manufactured by Otsuka Electronics Co., Ltd.) can be used as a zeta potential meter.

[0073] Furthermore, depending on the presence of various salts or metal ions in the culture medium, or the pH of the culture medium, the zeta potential of the surface of the charge-retaining layer opposite the substrate side in the culture medium may differ from the zeta potential in water.

[0074] (2) The material charge holding layer is not particularly limited, but examples include an embodiment that includes a charge control agent and a binder resin (first embodiment), an embodiment that includes a polymer-type charge control agent (second embodiment), and so on.

[0075] (a) First embodiment (a1) Charge control agent The charge-retaining layer in this embodiment includes a charge control agent. The charge control agent is composed of a compound having an electric charge. Either a charge control agent for positive charging, a charge control agent for negative charging, or both can be used as the charge control agent, but in order to increase the charging polarity of the charge-retaining layer, it is preferable to use either a charge control agent for positive charging or a charge control agent for negative charging.

[0076] Examples of charge control agents for positive charge include azine compounds, quaternary ammonium salts, nigrosine dyes, triphenylmethane compounds, aminoalkyl compounds, and phenoxyacetic acid compounds.

[0077] Examples of azine compounds include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiaidine, 1,3-thiaidine, 1,4-thiaidine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline, and the like.

[0078] Examples of quaternary ammonium salts include benzyldecylhexylmethylammonium chloride, decyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium chloride, dimethylaminopropylacrylamide methyl quaternary salt, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, and tetrabutylammonium tetrafluoroborate.

[0079] Examples of nigrosine dyes include nigrosine BK, nigrosine NB, and nigrosine Z.

[0080] Examples of aminoalkyl compounds include aminoalkylsilanes, aminoalkylphosphates, aminoalkylsulfonic acids, aminoalkylcarboxylic acids, aminoalkylamides, aminoalkylureas, aminoalkylimidazolinium, aminoalkylpyridinium, aminoalkylpiperidinium, aminoalkylmorpholinium, aminoalkylthionium, aminoalkylphosphonium, aminoalkylsulfonium, aminoalkylcarbonium, aminoalkylazonium, aminoalkyloxonium, aminoalkylselenium, aminoalkyltelurnium, aminoalkylpolonium, aminoalkylastatine, aminoalkylradon, aminoalkylfuran, aminoalkylthiophene, aminoalkylpyrrole, aminoalkylimidazole, aminoalkylpyrimidine, and aminoalkylpyridine.

[0081] Phenoxyacetic acid compounds include chlor-substituted phenoxyacetic acid, fluoro-substituted phenoxyacetic acid, cyano-substituted phenoxyacetic acid, t-octyl-substituted phenoxyacetic acid, cumyl-substituted phenoxyacetic acid, t-butyl-substituted phenoxyacetic acid, phenyl-substituted phenoxyacetic acid, methyl-substituted phenoxyacetic acid, ethyl-substituted phenoxyacetic acid, propyl-substituted phenoxyacetic acid, butyl-substituted phenoxyacetic acid, pentyl-substituted phenoxyacetic acid, hexyl-substituted phenoxyacetic acid, and heptyl-substituted phenoxyacetic acid. Examples of substituted compounds include octyl phenoxyacetate substituted compounds, nonyl phenoxyacetate substituted compounds, decyl phenoxyacetate substituted compounds, undecyl phenoxyacetate substituted compounds, dodecyl phenoxyacetate substituted compounds, tridecyl phenoxyacetate substituted compounds, tetradecyl phenoxyacetate substituted compounds, pentadecyl phenoxyacetate substituted compounds, hexadecyl phenoxyacetate substituted compounds, heptadecyl phenoxyacetate substituted compounds, octadecyl phenoxyacetate substituted compounds, nonadecyl phenoxyacetate substituted compounds, and eicosyl phenoxyacetate substituted compounds.

[0082] The charge control agent for positive charging may be any one of the above-mentioned charge control agents for positive charging, or it may be a mixture of two or more types.

[0083] Examples of charge control agents for negative charge include chromium(III) compounds, zinc compounds, aluminum compounds, salicylic acid chelate compounds, coumarin dyes, anthraquinone dyes, phthalocyanine dyes, naphthol dyes, azo gold complex dyes, and phenoxyacetic acid compounds.

[0084] Examples of azo-containing metal complex dyes include azobenzene dyes, azonaphthol dyes, azoanthraquinone dyes, azophthalocyanine dyes, azocoumarin dyes, azoanthracene dyes, azopyrene dyes, azopyridine dyes, azopyrimidine dyes, azopyrrole dyes, azothiophene dyes, azofuran dyes, azoimidazole dyes, azopyridinium dyes, azopiperidinium dyes, azomorpholinium dyes, azothionium dyes, azophosphonium dyes, azosulfonium dyes, azocarbonium dyes, azoazonium dyes, azooxonium dyes, azoselenium dyes, and azoterlunium dyes.

[0085] Phenoxyacetic acid compounds include methyl phenoxyacetate substituted, ethyl phenoxyacetate substituted, propyl phenoxyacetate substituted, butyl phenoxyacetate substituted, pentyl phenoxyacetate substituted, hexyl phenoxyacetate substituted, heptyl phenoxyacetate substituted, octyl phenoxyacetate substituted, nonyl phenoxyacetate substituted, decyl phenoxyacetate substituted, undecyl phenoxyacetate substituted, dodecyl phenoxyacetate substituted, tridecyl phenoxyacetate substituted, tetradecyl phenoxyacetate substituted, and phenyl phenoxyacetate substituted. Examples include phenoxyacetate substituted derivatives, hexadecyl substituted derivatives, heptadecyl substituted derivatives, octadecyl substituted derivatives, nonadecyl substituted derivatives, eicosyl substituted derivatives, henicosyl substituted derivatives, docosyl substituted derivatives, tricosyl substituted derivatives, tetracosyl substituted derivatives, pentacosyl substituted derivatives, hexacosyl substituted derivatives, heptacosyl substituted derivatives, and octacosyl substituted derivatives.

[0086] The negative charge control agent may be any one of the negative charge control agents described above, or it may be a mixture of two or more.

[0087] The charge control agent content in the charge-holding layer is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. On the other hand, the charge control agent content in the charge-holding layer is preferably 20% by mass or less, and more preferably 10% by mass or less. When the charge control agent content is within the above range, the above-mentioned charge amount is easily obtained.

[0088] (a2) Binder resin The charge-holding layer in this embodiment may have a binder resin that disperses the charge control agent. Examples of binder resins include styrene-acrylic resins, polyester resins, epoxy resins, etc.

[0089] The binder resin may contain the hydrophilic polymer described above. This is because, even if the charge-retaining layer is placed over the entire surface of at least one side of the substrate, or if the charge-retaining layer is thick, the culture medium can be uniformly supplied from the substrate to each region of the surface on the adhesive side of the algae culture laminate. The binder resin may be used alone or in combination of two or more types.

[0090] (b) Second embodiment The charge-holding layer in this embodiment has a polymer-type charge control agent that becomes positively or negatively charged in water. The polymer-type charge control agent has a functional group that becomes positively charged in water. The positive or negative charge is appropriately selected depending on the type of algae.

[0091] The functional groups that are positively charged in water are not particularly limited, and examples include amino groups, ammonium groups, pyridinium groups, imidazole groups, and guanidino groups.

[0092] Furthermore, the functional groups that become negatively charged in water are not particularly limited, and examples include carboxyl groups, sulfo groups, and phosphate groups.

[0093] The organic polymers that become positively charged in water are not particularly limited, and examples include polyamine resins, styrene-acrylic copolymer resins, and polyethyleneimines.

[0094] The organic polymers that become negatively charged in water are not particularly limited, and examples include polycarboxylic acids. Examples of polycarboxylic acids include polyacrylic acid and polymethacrylic acid.

[0095] (3) The permeable charge-holding layer is preferably permeable to water. The water absorption time of the charge-holding layer is, for example, 300 seconds or less, preferably 100 seconds or less, and more preferably 60 seconds or less. The shorter the time, the faster the water absorption and the better the water permeability. On the other hand, the water absorption time of the substrate is, for example, 1 second or more. The measurement conditions are a temperature of 23±2°C and a relative humidity of 50±5%.

[0096] One method for imparting water permeability to a charge-holding layer is to form a patterned charge-holding layer on at least one surface of the substrate. By having a pattern, the charge-holding layer becomes water-permeable even when the binder resin is not hydrophilic. Examples of charge-holding layer patterns include grid patterns, mesh patterns, linear patterns, and dot patterns.

[0097] Another method for imparting water permeability to the charge-holding layer is to use a hydrophilic polymer as the material for the charge-holding layer. By including a hydrophilic polymer in the charge-holding layer, it is possible to supply culture medium to algae even when the charge-holding layer is placed over the entire surface of at least one side of the substrate. Furthermore, when the charge-holding layer is placed over the entire surface, the algae can be grown uniformly. The hydrophilic polymer may also serve as the binder resin in the first embodiment and the polymer-type charge control agent in the second embodiment.

[0098] (4) Thickness The thickness of the charge-retaining layer is, for example, 0.01 μm or more, preferably 0.1 μm or more, and more preferably 1 μm or more. By setting the thickness of the charge-retaining layer within the above range, sufficient electrostatic adsorption force to algae can be obtained. The thickness of the charge-retaining layer is, for example, preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less. By setting the thickness of the charge-retaining layer within the above range, water absorption is not impaired, and even when the algae culture stack is arranged vertically or at an angle, the thickness of the membrane can be suppressed so that the membrane does not collapse under its own weight during cultivation.

[0099] (5) Formation Method The charge-retaining layer can be formed, for example, by applying the charge-retaining layer composition onto a substrate, or by immersing the substrate in the charge-retaining layer composition and drying as necessary. Examples of application methods include gravure printing and die coating. The charge-retaining layer composition includes, for example, the above-mentioned charge control agent and binder resin, or a polymer-type charge control agent. The charge-retaining layer composition may also contain a solvent. Water, ethanol, and isopropyl alcohol are preferred as solvents, as residual solvents are less likely to inhibit the growth of algae. Water is preferred among these.

[0100] 4. Seed algae The adhesive layer side of the algal culture laminate in this disclosure may have seed algae arranged on it. Seed algae can be attached (seed) to the adhesive layer side of the algal culture laminate by immersing the algal culture laminate in a cell suspension containing seed algae and culture medium, or by coating or spraying the cell suspension onto it. The algal culture laminate with attached seed algae (algal culture laminate with seed algae) is preferably dried as needed.

[0101] 5. Easy-to-peel layer The algal culture laminate in this disclosure may have an easy-to-peel layer between the substrate and the adhesive layer. If the algal culture laminate has a charge-retaining layer, the easy-to-peel layer may be placed between the substrate and the charge-retaining layer, or between the charge-retaining layer and the adhesive layer.

[0102] The easily peelable layer can be formed by applying a release agent. The release agent is not particularly limited, and examples of which can be used include waxes, silicone resins, fluororesins, amino alkyd resins, melamine resins, polyester resins, and acrylic resins.

[0103] 6. A protective film may be placed on the adhesive layer side of the algae culture laminate in this disclosure. Any protective film known in the field of algae culture can be used without particular limitation.

[0104] The algal culture laminate in this disclosure may be in the form of a single leaf cut to a predetermined size, or in the form of a roll formed by winding a long sheet into a roll.

[0105] The algal culture laminate described herein is used in the manufacture of algal culture sheets. The algal culture sheets will be described later.

[0106] 7. Manufacturing Method This disclosure provides a method for manufacturing the algal culture laminate described above, wherein the adhesive layer is formed by a coating method or a transfer method. The method for forming the adhesive layer by a coating method or a transfer method is described in detail in "2. Adhesive Layer", so the explanation is omitted here.

[0107] Furthermore, this disclosure provides a method for producing the above-mentioned algal culture laminate, wherein the charge-retaining layer is formed by a coating method or a transfer method. The method for forming the charge-retaining layer by a coating method or a transfer method is described in detail in "3. Charge-retaining layer (5) Formation method," so the explanation is omitted here.

[0108] B. Algae Culture Sheet The algae culture sheet in this disclosure comprises the above-described algae culture laminate and a culture layer containing cultured algae, which is disposed on the adhesive layer side of the algae culture laminate. Figure 8 is a schematic cross-sectional view showing an example of the algae culture sheet in this disclosure. Figure 8 has been described in detail in section "A. Algae Culture Laminate", so its explanation is omitted here.

[0109] 1. The adhesive layer in the algae culture sheet is preferably made of a predetermined film strength. This is because it facilitates the peeling of the culture layer from the substrate together with the adhesive layer. Specifically, the tensile strength of the adhesive layer in the algae culture sheet is preferably 0.1 kPa or higher. The tensile strength of the adhesive layer is the tensile strength measured by a method compliant with JIS K7127 (1999) when the solid content of the adhesive layer is 5.0 wt%.

[0110] Other components and characteristics of the algal culture laminate are the same as those described in "A. Algal Culture Laminate".

[0111] 2. Culture Layer The culture layer contains algae. The algae may be either microalgae or macroalgae, but microalgae are preferred. Examples of microalgae include green algae (Chlorella, Chlamydomonas, Haematococcus, Botryococcus, and Dunaliella), treboxia algae (Parachlorella), prasinoalgae, cyanobacteria (Spirulina, Arthrostella, Synechococcus, Synechocystis, and Nostoc), haptophytes (Pleurocrysis), diatoms (Cheetoceros), true eyespot algae (Nannochloropsis), and Euglena. Examples of macroalgae include wakame and kelp. There may be one type of algae or multiple types.

[0112] For example, if the surface of the charge-holding layer is positively charged, the culture layer may contain species algae with a negative charge. Examples of species algae with a negative charge include Chlorella and cyanobacteria. Note that most microalgae are fundamentally negatively charged. On the other hand, if the surface of the charge-holding layer is negatively charged, the culture layer may contain species algae with a positive charge.

[0113] When the algae are microalgae, the culture layer is a membrane-like aggregate of microalgae formed by the microalgae themselves along with EPS (extracellular polymers: proteins, polysaccharides, etc.) and LPS (lipopolysaccharides) released outside their bodies. When the algae are macroalgae, the culture layer is an aggregate of macroalgae cells along with EPS (extracellular polymers: proteins, polysaccharides, etc.) and LPS (lipopolysaccharides) released outside their bodies. In addition, in the case of macroalgae, the above substances have a unique structure that enhances physical adhesion. In addition to these substances, similar substances may be artificially provided as a culture layer.

[0114] Many microalgae generally release polysaccharides, lipopolysaccharides, hydrocarbons, oils, etc. For example, algae that release polysaccharides include Chlorella and Botryococcus. Algae that release carboxylic acids include cyanobacteria, for example.

[0115] 3. Manufacturing Method The algae culture sheet in this disclosure can be manufactured by forming a culture layer on the adhesive layer side of the algae culture laminate described above. The first method for manufacturing an algae culture sheet is a manufacturing method using an algae culture laminate having an adhesive layer according to the first embodiment. The second method for manufacturing an algae culture sheet is a manufacturing method using an algae culture laminate having an adhesive layer according to the second embodiment.

[0116] (1) Method for manufacturing the first algae culture sheet The method for manufacturing the first algae culture sheet includes, for example, a culture step in which a culture solution is supplied to seed algae in the adhesive layer of an algae culture laminate having the adhesive layer of the first embodiment described above, while forming a culture layer. This promotes photosynthesis in each of the seed algae, causing the algae to grow and a culture layer to be formed. In the method for manufacturing the first algae culture sheet, since the adhesive layer of the first embodiment contains seed algae, the seeding step in the method for manufacturing the second algae culture sheet described later can be omitted.

[0117] (a) Culture process The culture medium (liquid medium) used in the culture process is an aqueous solution containing one or more of the following: a carbon source, nitrogen, phosphoric acid, potassium salt, calcium salt, magnesium salt, iron ions and cobalt ions, sodium salt, manganese ions, zinc ions, molybdenum ions, chelating agents, vitamins, etc. Specifically, examples include C medium, AF-6 medium, BG medium, BBM medium, MDM medium, ESM medium, etc.

[0118] As shown in Figure 9, a specific cultivation method in the cultivation process involves immersing the algae cultivation laminate 10 in a culture solution 50. This allows the substrate 1 and the adhesive layer 2 to absorb the culture solution 50, which is then supplied to each of the multiple algae species 100. Additionally, light and carbon dioxide are supplied to each of the multiple algae species from the adhesive layer 2 side of the algae cultivation laminate 10. This promotes photosynthesis in each of the multiple algae species 100, causing the algae to proliferate.

[0119] Figures 10(a) to (c) are schematic diagrams illustrating the installation configuration of the algae culture laminate when manufacturing algae culture sheets using a single-leaf method. As shown in Figure 10(a), the single-leaf type algae culture laminate 10 is installed on a horizontal shelf 71 consisting of multiple tiers. As shown in Figure 10(b), the single-leaf type algae culture laminate is installed by vertical suspension. As shown in Figure 10(c), the single-leaf type algae culture laminate is installed on a folding panel 72. In Figures 10(a) to (c), the culture solution is omitted, but the method of supplying the culture solution is not particularly limited. Furthermore, the algae culture laminate may be cultured by constantly immersing it in the culture solution, or by periodically immersing it in the culture solution.

[0120] (2) Method for producing a second algae culture sheet The method for producing a second algae culture sheet comprises a seeding step of attaching seed algae to the adhesive layer of an algae culture laminate having the adhesive layer of the second embodiment described above, and a cultivation step of forming a culture layer while supplying a culture solution.

[0121] (a) Seeding process: As a method for attaching seed algae to the adhesive layer of the algal culture laminate, the algal culture laminate can be immersed in a cell suspension containing seed algae and culture medium, or the cell suspension can be applied to the algal culture laminate by coating or spraying it. Application methods include gravure coating and die coating.

[0122] (b) Cultivation process The cultivation process is the same as the cultivation process in the first method for producing an algae culture sheet. A drying process may be included between the seeding process and the cultivation process.

[0123] (3) Other methods for manufacturing algae culture sheets may be a single-sheet method or a roll-to-roll method. After manufacturing the algae culture sheets, the culture layer is collected. In the case of the roll-to-roll method, the roll-to-roll method may be applied to each step, or each step may be carried out continuously using the roll-to-roll method.

[0124] The production of algae culture sheets and the recovery of the culture layer are carried out using a culture apparatus. The culture apparatus 80 illustrated in Figure 12 has a placement section 81 for arranging algae culture layers, a culture section 82 for performing cultivation, and a recovery section 83 for recovering the culture layer. The culture apparatus may further have a seeding section for attaching seed algae and a drying section for drying after seeding. Furthermore, it is preferable that the culture section 82 includes, for example, a light irradiation section 84, a carbon dioxide supply section 85, and a temperature control section 86. The recovery section 83 has, for example, a scraping mechanism such as a doctor blade for scraping off the culture layer and adhesive layer.

[0125] C. Method for Recovering the Culture Layer Figure 11 is a schematic cross-sectional view illustrating the method for recovering the culture layer in this disclosure. In this disclosure, as shown in Figure 11, a method for recovering the culture layer is provided, which involves peeling off the adhesive layer 2 and the culture layer 4 from the substrate 1 of the algae culture sheet 20 described above.

[0126] Algae cultured on the surface of a laminate for algae cultivation form a layered culture layer, which is harvested after a certain period of time. In this disclosure, the adhesive layer experiences a decrease in water content and improved membrane strength during the cultivation process. Furthermore, during the cultivation process, the adhesive force to the substrate decreases due to physical leakage of the adhesive or consumption as a carbon source. Therefore, it becomes possible to peel the culture layer, along with the adhesive layer, from the substrate.

[0127] Methods for separating the adhesive layer and culture layer from the substrate include, for example, partially peeling and lifting the edges of the adhesive layer and culture layer, and then physically pulling or winding them up using the edges as a starting point for peeling. Alternatively, the entire adhesive layer and culture layer may be peeled off at once. Furthermore, the adhesive layer and culture layer can be easily separated from the substrate by applying temperature, ultrasound, electricity, light, or mechanical stimulation to the algae culture sheet beforehand. Alternatively, only the upper part of the adhesive layer may be scraped off using a doctor blade.

[0128] Note that the present disclosure is not limited to the above-described embodiments. The above embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

[0129] Hereinafter, examples and comparative examples will be shown to further explain the present disclosure.

[0130] (Example) A rectangular coated paper (manufactured by Moorim Co., Ltd.) was prepared as a base material. A composition for an adhesive layer containing gelatin and a cell suspension (a suspension containing algal seeds and a culture solution) was applied onto this base material. C medium was used as the culture solution, and Chlorella was used as the algal seeds. Thereby, a laminate for algal culture was obtained. Next, a cut melamine sponge was placed diagonally in a screw bottle containing the culture solution, the laminate for algal culture was placed on the inclined surface of the melamine sponge, and culture was performed while supplying the culture solution to the laminate for algal culture through the melamine sponge, thereby manufacturing an algal culture sheet. For the images taken from the culture layer side of the algal culture sheets on the day of the start of culture, the 4th day, and the 6th day, the ratio (%) of the area occupied by algae to the adhesive layer area was calculated using the image analysis software ImageJ. The pseudo cell number (cells / m ２ ) was calculated from the formula of (area ratio (%) × unit area (m ２ [[ID=!0]] ) ÷ (25 μm ２ ) ) × 10 １０ . The results are shown in Table 1. In the above formula, since the cells of the microalgae are growing in a single layer and the average diameter of the Chlorella cells is about 5 μm, the average size in the planar direction per cell was assumed to be 25 μm ２ .

[0131] (Comparative Example) Algal seeds were sown by applying a cell suspension (a suspension containing algal seeds and a culture solution) onto the base material used in the example. C medium was used as the culture solution, and Chlorella was used as the algal seeds. Thereby, a laminate for algal culture was obtained. Thereafter, culture was performed in the same manner as in the example to manufacture an algal culture sheet. The algal culture sheets on the day of the start of culture, the 4th day, the 6th day, the 8th day, and the 11th day were photographed from the culture layer side, image processing was performed in the same manner as in the example, and the pseudo cell number was calculated. The results are shown in Table 1.

[0132] Table 1 shows that the algal culture sheets produced using the algal culture laminate of the example had a higher cell count than the algal culture sheets produced using the algal culture laminate of the comparative example.

[0133]

[0134] In other words, the present disclosure provides the following inventions.

[0135] [1] A laminate for culturing algae, comprising a base material and an adhesive layer containing an adhesive disposed on at least one surface of the base material. [2] The laminate for culturing algae according to [1], wherein the adhesive layer is disposed on the entire surface of at least one surface of the base material. [3] The laminate for culturing algae according to [1] or [2], wherein the adhesive layer is arranged in a pattern on at least one surface of the base material. [4] The laminate for culturing algae according to any one of [1] to [3], wherein the adhesive layer has a ball number of 2 or more at an inclination of 20 degrees in an inclined ball tack measurement conforming to JIS Z 0237 (2022). [5] The laminate for culturing algae according to any one of [1] to [4], wherein the adhesive layer contains one or more of gelatin, tara gum, sodium alginate, and xanthan gum as the adhesive. [6] The algae culture laminate according to any one of [1] to [5], wherein the adhesive layer is arranged in a pattern on at least one surface of the substrate, and one or more pattern layers with a different composition from the adhesive layer are arranged in at least a part of the region other than the region where the adhesive layer is arranged. [7] The algae culture laminate according to [6], wherein the one or more pattern layers include a pattern of a low-tack layer with lower tack strength than the adhesive layer. [8] The algae culture laminate according to [6], wherein the one or more pattern layers include a pattern of a valuable substance attachment layer capable of absorbing or adsorbing valuable substances produced by the cultivation of the algae. [9] The algae culture laminate according to any one of [1] to [8], wherein the adhesive layer includes seed algae.

[10] The algae culture laminate according to any one of [1] to [9], further comprising a charge-retaining layer between the substrate and the adhesive layer.

[11] The algae culture laminate according to any one of [1] to

[10] , wherein the substrate includes a hydrophilic material.

[12] The substrate comprises a hydrophobic material and has a hydrophilic surface treatment layer on the surface facing the adhesive layer, as described in any of [1] to

[10] .

[13] An algae culture sheet comprising the algae culture laminate described in any of [1] to

[12] and a culture layer disposed on the surface facing the adhesive layer of the algae culture laminate and containing cultured algae.

[14] The algae culture sheet according to

[13] , wherein the laminate for algae culture has the adhesive layer arranged in a pattern on at least one surface of the substrate, and the patterned culture layer is arranged at a position corresponding to the pattern of the adhesive layer.

[15] The algae culture sheet according to

[13] , wherein the laminate for algae culture has the adhesive layer arranged in a pattern on at least one surface of the substrate, and one or more pattern layers with a different composition from the adhesive layer are arranged in at least a part of the area other than the area where the adhesive layer is arranged, and the patterned culture layer is arranged at a position corresponding to the pattern of the adhesive layer.

[16] The algae culture sheet according to

[15] , wherein the one or more pattern layers in the algae culture laminate include a pattern of a low-tack layer with lower tack strength than the adhesive layer.

[17] The algae culture sheet according to

[15] , wherein the one or more pattern layers in the algae culture laminate include a pattern of a valuable substance attachment layer capable of absorbing or adsorbing valuable substances produced by the cultivation of algae, and the valuable substance attachment layer absorbs or adsorbs the valuable substances.

[18] A method for recovering a culture layer, comprising peeling the adhesive layer and the culture layer from the substrate of an algae culture sheet according to any one of

[13] to

[17] .

[19] A method for manufacturing an algae culture laminate according to any one of [1] to

[12] , wherein the adhesive layer is formed by a coating method or a transfer method.

[20] A method for manufacturing an algae culture laminate according to

[10] , wherein the charge-retaining layer is formed by a coating method or a transfer method.

[0136] 1… Substrate 2… Adhesive layer 3… Charge retention layer 4… Culture layer 10… Algae culture laminate 20… Algae culture sheet

Claims

1. A laminate for culturing algae, comprising a base material and an adhesive layer containing an adhesive disposed on at least one surface of the base material.

2. The laminate for culturing algae according to claim 1, wherein the adhesive layer is disposed over the entire surface of at least one surface of the substrate.

3. The laminate for culturing algae according to claim 1, wherein the adhesive layer is arranged in a pattern on at least one surface of the substrate.

4. The laminate for algae cultivation according to claim 1, wherein the adhesive layer has a ball number of 2 or more at an inclination of 20 degrees in an inclined ball tack measurement conforming to JIS Z 0237 (2022).

5. The laminate for algae cultivation according to claim 1, wherein the adhesive layer comprises one or more of gelatin, tara gum, sodium alginate, and xanthan gum as the adhesive.

6. The laminate for culturing algae according to claim 1, wherein the adhesive layer is arranged in a pattern on at least one surface of the substrate, and one or more pattern layers with a different composition from the adhesive layer are arranged in at least a portion of the region other than the region where the adhesive layer is arranged.

7. The laminate for culturing algae according to claim 6, wherein one or more pattern layers include a pattern of a low-tack layer with lower tack strength than the adhesive layer.

8. The algae culture laminate according to claim 6, wherein one or more pattern layers include a pattern of a valuable substance attachment layer capable of absorbing or adsorbing valuable substances produced by the cultivation of the algae.

9. The laminate for culturing algae according to claim 1, wherein the adhesive layer contains seed algae.

10. The algae culture laminate according to claim 1, further comprising a charge-retaining layer between the substrate and the adhesive layer.

11. The laminate for culturing algae according to claim 1, wherein the substrate comprises a hydrophilic material.

12. The laminate for algae cultivation according to claim 1, wherein the substrate comprises a hydrophobic material and has a hydrophilic surface treatment layer on the surface on the adhesive layer side.

13. An algae culture sheet comprising: an algae culture laminate according to any one of claims 1 to 12; and a culture layer disposed on the adhesive layer side of the algae culture laminate and containing cultured algae.

14. The algae culture sheet according to claim 13, wherein the laminate for algae culture has the adhesive layer arranged in a pattern on at least one surface of the substrate, and the patterned culture layer is arranged at a position corresponding to the pattern of the adhesive layer.

15. The algae culture sheet according to claim 13, wherein the laminate for algae culture has the adhesive layer arranged in a pattern on at least one surface of the substrate, one or more pattern layers with a different composition from the adhesive layer arranged in at least a portion of the area other than the area where the adhesive layer is arranged, and the patterned culture layer is arranged at a position corresponding to the pattern of the adhesive layer.

16. The algae culture sheet according to claim 15, wherein one or more pattern layers in the algae culture laminate include a pattern of a low-tack layer with lower tack strength than the adhesive layer.

17. The algae culture sheet according to claim 15, wherein one or more pattern layers in the algae culture laminate include a pattern of a valuable substance attachment layer capable of absorbing or adsorbing valuable substances produced by the cultivation of the algae, and the valuable substance attachment layer absorbs or adsorbs the valuable substances.

18. A method for recovering a culture layer, comprising peeling the adhesive layer and the culture layer from the substrate of the algae culture sheet according to claim 13.

19. A method for producing a laminate for algae cultivation according to any one of claims 1 to 12, wherein the adhesive layer is formed by a coating method or a transfer method.

20. A method for producing a laminate for algae cultivation according to claim 10, wherein the charge-retaining layer is formed by a coating method or a transfer method.

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