Method and apparatus for culturing microalgae

Abstract

The present invention provides a method and apparatus for culturing microalgae that can cultivate microalgae with high efficiency. [Solution] A culture medium is stored on a porous resin sheet 10 that is waterproof and breathable, and microalgae 65 are added to the culture medium. The added adhesive microalgae 65 adhere to the upper surface of the resin sheet 10, which corresponds to the bottom surface of the culture medium. The microalgae 65 adhering to the upper surface of the resin sheet 10 are efficiently supplied with carbon dioxide from the atmosphere present on the lower side of the resin sheet 10 through the fine pores of the resin sheet 10, and are also sufficiently supplied with water and nutrients from the culture medium. When light is irradiated from the light irradiation unit 50 in this state, photosynthesis of the microalgae 65 is promoted, and the microalgae 65 can be cultured with high efficiency.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for culturing microalgae such as green algae, cyanobacteria, and diatoms.

Background Art

[0002] Microalgae are those that are difficult to identify with the naked eye among algae, excluding large algae such as kelp and kombu, and are so-called phytoplankton. Microalgae are expected to be utilized in a wide range of fields such as biofuels, aquaculture feed, and food.

[0003] The need for technologies to culture microalgae, which are expected to have diverse applications, with high efficiency is increasing. For example, various culturing technologies such as those presented in Patent Documents 1 and 2 are being explored, but they have not yet reached full social implementation. As a relatively common culturing technology that has advanced in practical use, there is a method of culturing by suspending microalgae in a culture solution (suspension culture). Suspension culture includes an open type called the open pond method using an artificial pond of the culture solution and a closed type such as the glass tube type.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Microalgae are broadly classified into two types: planktonic algae that drift in or near the water surface, and adhesive (or benthic) algae that grow attached to the seabed or lakebed. While the planktonic cultivation method described above is suitable for cultivating planktonic microalgae, applying it to adhesive microalgae presents a problem: the algae adhere to the glass tube walls and other materials that need to transmit light, reducing cultivation efficiency. As for cultivation techniques for adhesive microalgae, coating culture, in which algae are applied to a carrier such as porous ceramics placed at the boundary between the gas phase and the culture medium, has been investigated at the laboratory level, but highly efficient cultivation techniques have not yet been put into practical use.

[0006] This invention has been made in view of the above problems, and aims to provide a method and apparatus for culturing microalgae that can cultivate microalgae with high efficiency. [Means for solving the problem]

[0007] To solve the above problems, a first aspect of this invention provides a method for culturing microalgae, comprising a storage step of storing a culture solution on a waterproof and breathable resin sheet, an introduction step of introducing microalgae into the culture solution, and an irradiation step of irradiating the microalgae with light, wherein the lower surface of the resin sheet is exposed to the atmosphere.

[0008] Furthermore, the second embodiment is a method for culturing microalgae according to the first embodiment, wherein in the irradiation step, light is irradiated onto the microalgae from an artificial light source.

[0009] Furthermore, the third embodiment further comprises a step of supplying carbon dioxide to the lower surface of the resin sheet in the method for culturing microalgae according to the first embodiment.

[0010] Furthermore, the fourth embodiment is a method for culturing microalgae according to the first embodiment, wherein the resin sheet is a porous fluororesin sheet.

[0011] Furthermore, the fifth embodiment is a method for culturing microalgae according to any of the first to fourth embodiments, wherein the microalgae are adhesive microalgae.

[0012] Furthermore, a sixth embodiment is a microalgae cultivation apparatus comprising a waterproof and breathable resin sheet and a support member for supporting the resin sheet, wherein the lower surface of the resin sheet is exposed to the atmosphere and light is irradiated onto the microalgae introduced into the culture medium stored on the resin sheet.

[0013] Furthermore, the seventh embodiment is a microalgae cultivation apparatus according to the sixth embodiment, further comprising an artificial light source for irradiating the microalgae with light.

[0014] Furthermore, the eighth embodiment is a microalgae cultivation apparatus according to the sixth embodiment, further comprising a gas supply unit that supplies carbon dioxide to the lower surface of the resin sheet.

[0015] Furthermore, the ninth embodiment is a microalgae cultivation apparatus according to the sixth embodiment, wherein the resin sheet is a porous fluororesin sheet.

[0016] Furthermore, the tenth embodiment is a microalgae cultivation apparatus according to any of the sixth to ninth embodiments, wherein the microalgae are adhesive microalgae. [Effects of the Invention]

[0017] According to the microalgae cultivation method of the first to fifth embodiments, light is irradiated onto microalgae placed in a culture medium stored on a waterproof and breathable resin sheet, and since the lower surface of the resin sheet is exposed to the atmosphere, the microalgae are irradiated with light while being sufficiently supplied with carbon dioxide and nutrients from the atmosphere, thereby promoting photosynthesis of the microalgae and enabling the cultivation of microalgae with high efficiency.

[0018] In particular, according to the third embodiment of the method for culturing microalgae, carbon dioxide is supplied to the underside of the resin sheet, allowing for more efficient cultivation of microalgae.

[0019] According to the microalgae culturing apparatus according to the 6th to 10th aspects, light is irradiated on the microalgae introduced into the culture solution stored on the resin sheet having waterproofness and air permeability, and the lower surface of the resin sheet is exposed to the atmosphere. Therefore, the microalgae are irradiated with light in a state where carbon dioxide and nutrients in the atmosphere are sufficiently supplied, so that the photosynthesis of the microalgae is promoted and the microalgae can be cultured with high efficiency.

[0020] In particular, according to the microalgae culturing apparatus according to the 8th aspect, since it further includes a gas supply unit for supplying carbon dioxide to the lower surface of the resin sheet, the microalgae can be cultured with higher efficiency.

Brief Description of Drawings

[0021] [Figure 1] FIG. 1 is a flowchart showing the procedure of the microalgae culturing method according to the present invention. [Figure 2] FIG. 2 is a diagram showing the main configuration of the microalgae culturing apparatus according to the present invention. [Figure 3] FIG. 3 is a diagram showing a state where the culture solution is stored on the resin sheet. [Figure 4] FIG. 4 is a diagram conceptually showing the introduction of the microalgae strain into the culture solution. [Figure 5] FIG. 5 is a diagram conceptually showing light irradiation on the microalgae. [Figure 6] FIG. 6 is an enlarged view of the vicinity of the resin sheet during light irradiation. [Figure 7] FIG. 7 is a diagram showing the increase amount of the microalgae. [Figure 8] FIG. 8 is a diagram showing the main configuration of the culturing apparatus of the second embodiment. [Figure 9] FIG. 9 is a diagram showing the main configuration of the culturing apparatus of the third embodiment. [Figure 10] FIG. 10 is a diagram showing the main configuration of the culturing apparatus of the fourth embodiment.

Modes for Carrying Out the Invention

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following, expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) shall, unless otherwise specified, not only strictly represent the positional relationship but also represent a state in which there is a relative displacement in terms of angle or distance within a tolerance or a range in which a similar level of function can be obtained. Similarly, expressions indicating equality (e.g., "identical," "equal," "homogeneous," etc.) shall, unless otherwise specified, not only represent a state in which there is a quantitatively strictly equal state but also represent a state in which there is a difference in which a tolerance or a similar level of function can be obtained. Furthermore, expressions indicating shape (e.g., "circular," "square," "cylindrical," etc.) shall, unless otherwise specified, not only strictly represent the geometrically precise shape but also represent a shape within a range in which a similar level of effect can be obtained, and may have, for example, irregularities or chamfers. Additionally, expressions such as "equipped," "possessing," "containing," "having," etc., for a component are not exclusive expressions that exclude the existence of other components. Furthermore, the expression "at least one of A, B, and C" includes "A only," "B only," "C only," "any two of A, B, and C," and "all of A, B, and C."

[0023] <First Embodiment> Figure 1 is a flowchart showing the procedure for culturing microalgae according to the present invention. First, a waterproof and breathable resin sheet is installed (step S1). Figure 2 is a diagram showing the main components of the microalgae cultivation apparatus according to the present invention. The cultivation apparatus 1 comprises a resin sheet 10, a support part 20, and a light irradiation part 50 as its main elements.

[0024] The resin sheet 10 is, for example, a porous PTFE (polytetrafluoroethylene) film. PTFE is a type of fluororesin. Because the resin sheet 10 is porous, it is breathable. Also, because the resin sheet 10 is made of PTFE, it is waterproof. Although the resin sheet 10 has many pores, these pores are extremely fine, so surface tension prevents moisture from leaking out. In other words, the resin sheet 10 has both breathability and waterproofing properties. The thickness of the resin sheet 10 is, for example, 0.2 mm. The shape and size (area) of the resin sheet 10 can be appropriately determined according to the shape and size of the culture device 1, and in this embodiment, it is, for example, circular.

[0025] The support section 20 comprises an upper block 21 and a lower block 22. The upper block 21 has a substantially cylindrical shape with, for example, an open upper and lower end. The material of the upper block 21 can be any material that is water-resistant, and can be metal, ceramics, resin, etc. as appropriate. The inner diameter of the substantially cylindrical upper block 21 is smaller than the diameter of the resin sheet 10. Note that the shape of the upper block 21 is not limited to a substantially cylindrical shape, and can be any cylindrical shape appropriate to the shape of the resin sheet 10, for example, it may be a polygonal cylindrical shape such as a square or hexagon.

[0026] The lower block 22 is, for example, a ring-shaped plate member. The material of the lower block 22 can also be made of an appropriate material. The inner diameter of the ring-shaped lower block 22 is about the same as the inner diameter of the upper block 21 and smaller than the diameter of the resin sheet 10. The shape of the lower block 22 is not limited to a ring shape, and can be an appropriate ring shape depending on the shape of the resin sheet 10, for example, it may be a polygonal ring such as a square or hexagon. It is preferable that the shape of the upper block 21 and the shape of the lower block 22 are consistent.

[0027] The upper block 21 and the lower block 22 are connected by bolts 25. The upper block 21 and the lower block 22 are fastened together by bolts 25 at multiple points (for example, four points) along the circumferential direction of their peripheral edges. The bolts 25 also adjust the distance between the upper block 21 and the lower block 22. That is, rotating the bolts 25 in the forward direction narrows the distance between the upper block 21 and the lower block 22, and rotating them in the reverse direction widens the distance between the upper block 21 and the lower block 22.

[0028] With the resin sheet 10 spread horizontally, an O-ring 31 is sandwiched between the upper block 21 and the upper peripheral edge of the resin sheet 10, and an O-ring 32 is sandwiched between the lower block 22 and the lower peripheral edge of the resin sheet 10. In this state, by narrowing the gap between the upper block 21 and the lower block 22 with multiple bolts 25, the peripheral edges of the resin sheet 10 are pressed from above and below by the O-rings 31 and 32, and the resin sheet 10 is fixed in place. In other words, the resin sheet 10 is stretched by the support part 20. The lower surface of the resin sheet 10 stretched by the support part 20 is exposed to the atmosphere.

[0029] As shown in Figure 2, in the first embodiment, a light irradiation unit 50 is provided above the resin sheet 10 stretched by the support unit 20. The light irradiation unit 50 includes, for example, a plurality of white LED (Light-Emitting Diode) lamps 51. Furthermore, if the area of ​​the resin sheet 10 is considerably large, a perforated metal may be provided to support the resin sheet 10 from below. In addition, the culture apparatus 1 may be provided with a temperature control mechanism to maintain the temperature of the culture medium at a constant temperature.

[0030] Next, the culture solution is stored on the stretched resin sheet 10 (step S2). Figure 3 shows the state in which the culture solution has been stored on the resin sheet 10. The culture solution is a liquid containing nutrients necessary for the growth of microalgae at an appropriate concentration. As the culture solution, it is possible to select an appropriate one depending on the type of microalgae to be cultivated. For example, if the target of cultivation is freshwater microalgae, the culture solution is made by dissolving nutrients such as potassium nitrate and calcium nitrate in fresh water. Alternatively, if the target of cultivation is marine microalgae, the culture solution is made by dissolving nutrients such as sodium nitrate in artificial seawater.

[0031] With the resin sheet 10 stretched over the support section 20, the culture medium is poured into the inside of the upper block 21, thereby accumulating on the resin sheet 10. As shown in Figure 3, the culture medium is stored in the space enclosed by the upper side of the resin sheet 10 and the inner wall of the upper block 21. The gap between the upper block 21 and the resin sheet 10 is sealed by an O-ring 31, preventing the culture medium from leaking out through that gap. Furthermore, although the resin sheet 10 is porous, it is waterproof, so the stored culture medium does not leak out through the resin sheet 10 downwards. In other words, because the holes in the resin sheet 10 are extremely fine, surface tension prevents the culture medium from leaking out through those holes.

[0032] Next, the microalgae strain 60 is added to the culture medium stored on the resin sheet 10 (step S3). Figure 4 is a conceptual diagram showing the addition of the microalgae strain 60 to the culture medium. Examples of microalgae to be cultured include green algae, cyanobacteria, diatoms, or dinoflagellates. In the first embodiment, the microalgae strain 60 added to the culture medium is an adhesive microalga.

[0033] Most of the attached microalgae introduced into the culture medium adhere to the upper surface of the resin sheet 10, which is the bottom of the culture pond. After introducing the microalgae strain 60 into the culture medium, light irradiation from the light irradiation unit 50 is performed (step S4). Figure 5 is a conceptual diagram showing the light irradiation of the microalgae. Figure 6 is a magnified view of the vicinity of the resin sheet 10 during light irradiation.

[0034] Due to their ecological characteristics, the adhesive microalgae 65 inhabit the upper surface of the resin sheet 10, which corresponds to the bottom surface of the culture medium. Because the resin sheet 10 is porous, it is permeable, and as shown in Figure 6, atmospheric carbon dioxide (CO2) present on the underside of the resin sheet 10 is supplied to the microalgae 65 attached to the upper surface through the fine pores perforated in the resin sheet 10. In addition, the microalgae 65 attached to the upper surface of the resin sheet 10 are in direct contact with the culture medium stored on the resin sheet 10, and are supplied with sufficient moisture and nutrients from the culture medium. Furthermore, the microalgae 65 attached to the upper surface of the resin sheet 10 are irradiated with white light similar to natural light (sunlight) from the white LED lamp 51 of the light irradiation unit 50.

[0035] When microalgae 65 are exposed to light and supplied with water and carbon dioxide, photosynthesis proceeds. As photosynthesis progresses in an environment where nutrients are supplied from the culture medium, the microalgae 65 proliferate and are cultured.

[0036] For the light irradiation in step S4, for example, a white LED lamp 51 is turned on for 10 hours a day, followed by 14 hours of inactivity, and this irradiation pattern is repeated for several days to several tens of days. In other words, an irradiation pattern similar to that of sunlight is repeated. It has been found that repeatedly turning the white LED lamp 51 on and off, similar to sunlight, increases the cultivation efficiency of microalgae 65, rather than keeping the white LED lamp 51 continuously on.

[0037] Furthermore, when culturing the microalgae 65 by light irradiation in step S4, the culture medium may be maintained at a constant temperature (e.g., 21°C) suitable for culturing the microalgae 65 using a temperature control mechanism (not shown). This is expected to stabilize the growth rate of the microalgae 65.

[0038] By repeatedly turning the white LED lamp 51 on and off, the cultivation of microalgae 65 progresses on the upper surface of the resin sheet 10. Figure 7 shows the verification results of culturing microalgae 65 using the method described above. Figure 7 is a diagram showing the increase in microalgae 65. The circles and solid lines in Figure 7 show the results of culturing microalgae 65 using the method of this embodiment with the resin sheet 10 (hereinafter referred to as "aeration membrane culture"). On the other hand, the triangles and dotted lines in Figure 7 show the results of cultivation by simply adding the microalgae strain 60 to the culture medium and irradiating it with light without using the resin sheet 10 (hereinafter referred to as "existing culture") as a comparative example. The horizontal axis of Figure 7 shows the number of days elapsed since adding the microalgae strain 60 to the culture medium and starting light irradiation (i.e., since starting cultivation). The vertical axis of Figure 7 shows the daily increase in microalgae 65 per unit area. Furthermore, all other conditions (e.g., culture medium composition, light irradiation time, temperature, etc.) are the same for both the aerated membrane culture and the existing culture, except for the presence or absence of the resin sheet 10.

[0039] As shown in Figure 7, eight days after the start of cultivation, the increase in microalgae 65 in the aerated membrane culture was significantly greater than the increase in the existing culture. Furthermore, even after 16 days, the increase in microalgae 65 in the aerated membrane culture was greater than that in the existing culture, and the difference widened further. On the other hand, after 21 days, the increase in microalgae 65 in the existing culture was greater than that in the aerated membrane culture, reversing the relationship between the two.

[0040] As shown in Figure 7, the verification results indicate that microalgae 65 tend to proliferate in a much shorter period in aeration membrane culture compared to the existing culture. The fact that the increase in the existing culture was greater than that of the aeration membrane culture 21 days after the start of cultivation suggests that at this point, the growth peak of microalgae 65 in the aeration membrane culture had already been passed and the increase had decreased. In other words, it is presumed that in aeration membrane culture, microalgae 65 proliferates rapidly from the beginning of cultivation, reaches its growth peak in a relatively short period of time, and then the increase begins to decrease. Therefore, it is recognized that microalgae 65 can be cultured efficiently in a short period of time in aeration membrane culture.

[0041] In the first embodiment, a culture medium is stored on a porous resin sheet 10 that is waterproof and breathable, and attached microalgae 65 are placed in the culture medium and irradiated with light from a light irradiation unit 50. The attached microalgae 65 adhere to the upper surface of the resin sheet 10, which corresponds to the bottom surface of the culture medium. The microalgae 65 attached to the upper surface of the resin sheet 10 are efficiently supplied with carbon dioxide from the atmosphere present on the lower side of the resin sheet 10 through the fine pores of the resin sheet 10, and are also sufficiently supplied with water and nutrients from the culture medium. When light is irradiated from the light irradiation unit 50 in this state, photosynthesis of the microalgae 65 is promoted, and the microalgae 65 can be cultured with high efficiency.

[0042] <Second Embodiment> Next, a second embodiment of the present invention will be described. In the first embodiment, the light irradiation unit 50 was provided above the resin sheet 10, but in the second embodiment, the light irradiation unit 50 is provided below the resin sheet 10.

[0043] Figure 8 shows the main components of the culture apparatus 2 of the second embodiment. In Figure 8, the same reference numerals are used for elements that are the same as in the first embodiment. In the second embodiment, a light irradiation unit 50 is provided below the resin sheet 10 stretched by the support unit 20. In addition to being waterproof and breathable, the resin sheet 10 of the second embodiment is light-transmitting. That is, the resin sheet 10 is transparent to light emitted from the white LED lamp 51. The remaining components of the second embodiment, except for the placement of the light irradiation unit 50, are the same as in the first embodiment.

[0044] In the second embodiment as well, a culture medium is stored on a porous resin sheet 10 that is waterproof and breathable, and light is irradiated from a light irradiation unit 50 onto adhesive microalgae 65 that have been introduced into the culture medium. The adhesive microalgae 65 adhere to the upper surface of the resin sheet 10, which corresponds to the bottom surface of the culture medium. The microalgae 65 adhering to the upper surface of the resin sheet 10 are efficiently supplied with carbon dioxide from the atmosphere present on the lower side of the resin sheet 10 through the fine pores of the resin sheet 10, and are also sufficiently supplied with water and nutrients from the culture medium.

[0045] Furthermore, in the second embodiment, the light irradiation unit 50 irradiates light from below the resin sheet 10. The light emitted upward from the white LED lamp 51 of the light irradiation unit 50 passes through the resin sheet 10 and irradiates the microalgae 65. The microalgae 65 are attached to the upper surface of the resin sheet 10. Therefore, in the second embodiment, the light emitted from the white LED lamp 51 passes through the resin sheet 10 and immediately irradiates the microalgae 65. In other words, in the first embodiment, the light emitted from the upper white LED lamp 51 passed through the liquid layer of the culture medium and irradiated the microalgae 65, whereas in the second embodiment, the light emitted from the lower white LED lamp 51 passes through the resin sheet 10 and irradiates the microalgae 65 without passing through the culture medium. Therefore, if the thickness of the resin sheet 10 is thin and the transmittance is high, the irradiation efficiency will be higher if the light is irradiated from below the resin sheet 10 as in the second embodiment. By efficiently supplying carbon dioxide, water, and nutrients to the microalgae 65, and by efficiently irradiating them with light, photosynthesis of the microalgae 65 is promoted, allowing for more efficient cultivation of the microalgae 65.

[0046] <Third Embodiment> Next, a third embodiment of the present invention will be described. In the first and second embodiments, light was irradiated onto the microalgae 65 from a white LED lamp 51, i.e., an artificial light source, but in the third embodiment, sunlight is irradiated onto the microalgae 65.

[0047] Figure 9 shows the main components of the culture apparatus 3 of the third embodiment. In Figure 9, the same reference numerals are used for elements that are the same as in the first embodiment. In the third embodiment, the culture apparatus 3 does not have a lamp, which is an artificial light source. The remaining components of the third embodiment, except for the absence of a lamp, are the same as in the first embodiment.

[0048] In the third embodiment, a culture medium is stored on a porous resin sheet 10 that is waterproof and breathable, and attached microalgae 65 are placed in the culture medium and exposed to sunlight. The attached microalgae 65 adhere to the upper surface of the resin sheet 10, which corresponds to the bottom surface of the culture medium. The microalgae 65 attached to the upper surface of the resin sheet 10 are efficiently supplied with carbon dioxide from the atmosphere present on the lower side of the resin sheet 10 through the fine pores of the resin sheet 10, and are also sufficiently supplied with water and nutrients from the culture medium. When sunlight is irradiated onto the microalgae 65 in this state, photosynthesis of the microalgae 65 is promoted, and the microalgae 65 can be cultivated with high efficiency.

[0049] In the third embodiment, since sunlight is used without installing lamps in the culture device 3, the manufacturing cost of the culture device 3 itself and the running costs required for culturing the microalgae 65 can be significantly reduced compared to the first and second embodiments. In addition, the electrical energy consumed in the third embodiment can also be significantly reduced compared to the first and second embodiments. On the other hand, since sunlight is affected by weather conditions, the first and second embodiments are superior to the third embodiment in terms of cultivation stability. Furthermore, when culturing microalgae 65 on a large scale using multiple culture devices, in the first and second embodiments, the culture devices can be stacked vertically. In contrast, in the third embodiment, it is impossible to stack the culture devices in order to utilize sunlight, and the culture devices must be arranged horizontally, resulting in a larger overall installation area.

[0050] <Fourth Embodiment> Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, carbon dioxide from the atmosphere was taken in through the fine pores of the resin sheet 10, but in the fourth embodiment, carbon dioxide is intentionally supplied to the lower surface of the resin sheet 10.

[0051] Figure 10 shows the main components of the culture apparatus 4 of the fourth embodiment. In Figure 10, the same reference numerals are used for elements that are the same as in the first embodiment. In the fourth embodiment, a gas supply unit 70 is provided in the culture apparatus 4 for microalgae 65. The gas supply unit 70 includes a carbon dioxide supply source 71 and a gas nozzle 72. When the carbon dioxide supply source 71 supplies carbon dioxide, carbon dioxide is blown from the gas nozzle 72 toward the lower surface of the resin sheet 10. This makes it possible to raise the concentration of carbon dioxide on the lower surface of the resin sheet 10 to a higher level than the concentration of carbon dioxide in the atmosphere. The remaining components of the fourth embodiment, except for the provision of the gas supply unit 70, are the same as in the first embodiment.

[0052] In the fourth embodiment, a culture medium is stored on a porous resin sheet 10 that is waterproof and breathable, and light is irradiated from a light irradiation unit 50 onto adhesive microalgae 65 that have been placed in the culture medium. The adhesive microalgae 65 adhere to the upper surface of the resin sheet 10, which corresponds to the bottom surface of the culture medium. The microalgae 65 adhering to the upper surface of the resin sheet 10 are supplied with sufficient moisture and nutrients from the culture medium.

[0053] Furthermore, in the fourth embodiment, carbon dioxide is supplied from the gas supply unit 70 to the lower surface of the resin sheet 10 to increase the concentration of carbon dioxide on that lower surface. As a result, a sufficient amount of carbon dioxide can be supplied to the microalgae 65 attached to the upper surface of the resin sheet 10 through the fine pores of the resin sheet 10, compared to the first to third embodiments. By supplying the microalgae 65 with sufficient carbon dioxide, water, and nutrients, and irradiating them with light from the light irradiation unit 50, photosynthesis of the microalgae 65 is promoted, and the microalgae 65 can be cultivated with higher efficiency.

[0054] <Variation> While embodiments of the present invention have been described above, various modifications can be made to this invention without departing from its spirit. For example, in each of the above embodiments, the microalgae 65 to be cultured were adhesive, but the invention is not limited to this, and the microalgae to be cultured in the culture technology of the present invention may also be planktonic. However, adhesive microalgae 65 adhere to the upper surface of the resin sheet 10, so carbon dioxide from the atmosphere can be supplied more efficiently through the fine pores of the resin sheet 10.

[0055] Furthermore, in the first, second, and fourth embodiments, the microalgae 65 were irradiated with light from a white LED lamp 51, but this is not limited to this, and light irradiation may be performed from, for example, a fluorescent lamp.

[0056] Furthermore, the resin sheet 10 in each of the above embodiments is not limited to a porous PTFE film, but may be any other fluororesin sheet having waterproof and breathable properties. Moreover, the resin sheet 10 is not limited to a fluororesin sheet, but may be any resin film having waterproof and breathable properties, such as a polypropylene sheet.

[0057] Furthermore, in each of the above embodiments, a perforated metal is provided to support the resin sheet 10 from below. In this way, even if the area of ​​the resin sheet 10 is large, a large amount of culture medium can be stored on the resin sheet 10. [Industrial applicability]

[0058] The technology according to the present invention can be suitably applied to the cultivation of microalgae such as green algae, cyanobacteria, and diatoms, and in particular to the cultivation of attached microalgae. [Explanation of Symbols]

[0059] 1,2,3,4 Culture device 10 Resin Sheets 20 Support part 31, 32 O-rings 50 Light-irradiated section 51 White LED Lamps 65 Microalgae 70 Gas Supply Department

Claims

1. A storage step in which a culture medium is stored on a waterproof and breathable resin sheet, The process of adding microalgae to the culture medium, The process involves irradiating the microalgae with light, Equipped with, The lower surface of the aforementioned resin sheet is a method for culturing microalgae exposed to the atmosphere.

2. In the method for culturing microalgae according to claim 1, A method for culturing microalgae, wherein the irradiation step involves irradiating the microalgae with light from an artificial light source.

3. In the method for culturing microalgae according to claim 1, A method for culturing microalgae, further comprising the step of supplying carbon dioxide to the lower surface of the resin sheet.

4. In the method for culturing microalgae according to claim 1, The resin sheet is a porous fluororesin sheet. A method for culturing microalgae.

5. In a method for culturing microalgae according to any one of claims 1 to 4, The aforementioned microalgae are attached microalgae, and the method for culturing these microalgae is described.

6. A resin sheet that is waterproof and breathable, A support member that supports the aforementioned resin sheet, Equipped with, The lower surface of the aforementioned resin sheet is exposed to the atmosphere. A microalgae cultivation apparatus that irradiates light onto microalgae introduced into a culture medium stored on the aforementioned resin sheet.

7. In the microalgae culture apparatus according to claim 6, A microalgae cultivation apparatus further comprising an artificial light source for irradiating the microalgae with light.

8. In the microalgae culture apparatus according to claim 6, A microalgae cultivation apparatus further comprising a gas supply unit that supplies carbon dioxide to the lower surface of the resin sheet.

9. In the microalgae culture apparatus according to claim 6, The aforementioned resin sheet is a porous fluororesin sheet used in a microalgae cultivation device.

10. In a microalgae cultivation apparatus according to any one of claims 6 to 9, The aforementioned microalgae are attached microalgae, and the apparatus is for culturing microalgae.

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