Microalgae culture device, culture system, and culture method

Abstract

To provide a microalgae culture device, culture system, and culture method that can mass-produce high-value microalgae while preserving the environment.SOLUTION: Provided is a microalgae culture device 1 comprising a culture tank 2, a support 3, and a power source 4. The culture tank 2 comprises a culture portion 21 that is below a water surface 60 and has a width in the surface direction of the water surface 60, and a gas storage portion 22. The power source 4 oscillates to configure: a first state in which a tip portion 21a of the culture portion 21, which is farther from the gas storage portion 22, is at the lowest position within the range of oscillation; and a second state in which the tip portion 21a of the culture portion 21 is at the highest position within the range of oscillation. The transition from the first state to the second state moves the gas in the gas storage portion 22 into the culture portion 21, and the transition from the second state to the first state moves the gas in the culture portion 21 into the gas storage portion 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a culture device, a culture system, and a culture method for microalgae. [Background technology]

[0002] Conventionally, microalgae are cultured in a culture tank that contains microalgae, a culture solution, and a gas containing carbon dioxide. To prevent contamination of the microalgae, it is preferable to culture the microalgae in a closed system. In this case, dissolved oxygen accumulates in the culture tank over time due to photosynthesis of the microalgae, inhibiting the growth of the microalgae and decreasing the concentration of dissolved carbon dioxide, thereby decreasing the culture efficiency. Therefore, in order to efficiently and continuously culture the microalgae, it is necessary to remove the dissolved oxygen by some means and supply dissolved carbon dioxide.

[0003] For example, Patent Document 1 proposes a method for cultivating microalgae using a horizontal closed growth vessel, which is capable of stirring the liquid medium and removing oxygen.

[0004] In recent years, the rapid growth of the aquaculture industry has led to the problem that a large amount of sludge and wastewater is being discharged into the natural world, destroying the ecosystem. Therefore, there is a strong desire to build a recycling system that actively recovers nutrients from the sludge and wastewater produced by aquaculture and mass-produces valuable microalgae, thereby achieving both economic incentives and environmental conservation. Since most aquaculture sites are located in tropical developing countries, when considering mass production of microalgae, facilities are required to realize the temperature and light environment suitable for cultivation, but the reality is that these developing countries do not have the capacity to make capital investments. Therefore, there is a need to develop a cultivation device and method that allows mass cultivation of microalgae with reduced capital investment, even in tropical regions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6741284 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a microalgae culture device, culture system, and culture method that can culture valuable microalgae while simultaneously mass-producing them and protecting the environment. More specifically, the present invention aims to provide a microalgae culture device, culture system, and culture method that can culture microalgae while stirring the culture solution in a culture tank by rocking a culture tank floating on the water surface and intermittently supplying gas (carbon dioxide) to the culture solution. [Means for solving the problem]

[0007] This invention is a microalgae culture device comprising: a culture tank that contains microalgae to be cultured, a culture solution, and a gas used for culture; a support that supports the culture tank so that it can be oscillated while at least a portion of the culture tank is located below the water surface; and a power source that oscillates the culture tank, wherein the culture tank comprises a culture section that has a portion below the water surface and has a width in the surface direction of the water surface and contains the microalgae and the culture solution, and a gas storage section that is connected to the culture section and contains the gas, and the power source oscillates the culture tank to form a first state in which a tip of the culture section farthest from the gas storage section is at the lowest position within the oscillation range, and a second state in which the tip of the culture section is at the highest position within the oscillation range, and in the process of transitioning from the first state to the second state, the gas in the gas storage section moves into the culture section, and in the process of transitioning from the second state to the first state, the gas that has moved into the culture section moves into the gas storage section, thereby stirring the culture solution. The culture tank may be rocked at predetermined time intervals. With this configuration, the gas (carbon dioxide) used in the culture is moved from inside the gas storage unit to inside the culture unit by the rocking of the culture tank. As a result, the microalgae culture device can not only agitate the culture solution and microalgae by rocking, but also culture the microalgae while intermittently feeding gas (carbon dioxide) into the culture solution by moving the gas into the culture solution, thereby promoting the growth of the microalgae.

[0008] As an aspect of the present invention, the gas storage section can include an outside air intake hole for taking in gas from outside the device, and a gas exhaust hole for exhausting gas to the outside of the device. This allows carbon dioxide to be consumed through photosynthesis by the microalgae, gas rich in oxygen to be discharged, and outside air rich in carbon dioxide to be taken in.

[0009] In addition, as an aspect of the present invention, a gas transfer path is provided that connects the culture section with the gas storage section, and during the process of transitioning from the first state to the second state, the gas in the gas storage section moves through the gas transfer path into the culture section. This configuration allows the gas to be efficiently transferred from the gas storage section to the culture section.

[0010] In the present invention, the gas transfer path can be configured so that it is connected to the gas storage portion at a height above the water surface in either state. This configuration allows the gas to be efficiently transferred from the gas storage section to the culture section.

[0011] Furthermore, in the present invention, the power source controls the oscillation of the culture tank between a first state and a second state, and can create a stationary state between the first state and the second state in which the culture tank is stationary and the culture section is kept in an approximately horizontal state. With this configuration, it is possible to appropriately switch between a static state that promotes the cultivation of microalgae and an oscillating state that agitates the microalgae and culture solution and supplies carbon dioxide to the microalgae, enabling efficient cultivation of the microalgae without killing them.

[0012] The present invention also relates to a microalgae culture system comprising a microalgae culture device, a control means for controlling a power source, and a power supply means for supplying electric power to the power source. With this configuration, gas moves between the upper end and the tip through the gas movement path due to the rocking of the culture tank, and the rocking reliably mixes the culture solution and microalgae, resulting in a microalgae culture system that can supply gas (carbon dioxide) to the culture solution and microalgae.

[0013] Furthermore, in the present invention, a microalgae culture system can be formed by connecting a plurality of microalgae culture devices. This configuration makes it possible to utilize a large area such as the ocean while actively recovering nutrients from large amounts of sludge and wastewater present in the sea or on the seabed, and mass-producing valuable microalgae.

[0014] The present invention also provides a method for culturing microalgae using a microalgae culture device, the method comprising: a culture tank containing microalgae to be cultured, a culture solution, and a gas used for culturing; a support for supporting the culture tank so that the culture tank can be oscillated with at least a portion of the culture tank positioned below the water surface; and a power source for oscillating the culture tank, the culture tank comprising a culture section having a portion below the water surface, having an area in a planar direction of the water surface, and containing the microalgae and the culture solution; and a gas storage section communicating with the culture section at a portion of an upper position via a gas transfer path and containing the gas, the method comprising the steps of: The present invention relates to a method for cultivating microalgae, in which the culture tank is rocked by a power source to form a first state in which the tip of the culture unit farthest from the gas storage unit is at the lowest position within the range of rocking, and a second state in which the tip of the culture unit is at the highest position within the range of rocking, and in the process of transitioning from the first state to the second state, gas in the gas storage unit moves through the gas transfer path into the culture unit, and in the process of transitioning from the second state to the first state, the gas that has moved into the culture unit moves back into the gas storage unit, thereby stirring the culture solution. The rocking of the culture tank moves the gas (carbon dioxide) used in the culture from the gas storage section to the culture section through the gas transfer path. This allows the microalgae culture device to not only agitate the culture solution and microalgae by rocking, but also to culture microalgae while intermittently feeding gas (carbon dioxide) into the culture solution by transferring the gas into the culture solution, thereby promoting the growth of the microalgae. Effect of the Invention

[0015] The present invention makes it possible to provide a microalgae culture device, culture system, and culture method that enable mass production of valuable microalgae while simultaneously protecting the environment. [Brief description of the drawings]

[0016] [Figure 1] Diagram of the microalgae culture system. [Diagram 2] FIG. 1 is a diagram showing the configuration of a microalgae culture device. [Diagram 3] FIG. 2 is a perspective view of a microalgae culture device. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6a] FIG. 2 is a longitudinal cross-sectional view showing a culture tank and a culture medium in a stationary state. [Figure 6b] FIG. 2 is a longitudinal sectional view showing the culture tank and the culture medium during shaking. [Figure 6c] FIG. 4 is a longitudinal cross-sectional view of the culture tank and the culture medium in a state where the angle change in one direction due to rocking is maximum (second state). [Figure 6d] FIG. 2 is a longitudinal cross-sectional view of the culture tank and the culture medium in a state where the angle change to the other side due to rocking is maximum (first state). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing the configuration of a microalgae culture system 10 having a plurality of microalgae culture units 1, and FIG. 2 is a plan view showing the configuration of a single microalgae culture unit 1 and a power source 4. As shown in FIG.

[0018] 1, a microalgae culture system 10 includes a plurality of microalgae culture units 1, a power source 4, wires 5 connecting each microalgae culture unit 1 to the power source 4, a power supply device 12 that supplies power to the power source 4, a control device 11 (control means) that controls the power source 4 and the power supply device 12, a water tank 6 in which each microalgae culture unit 1 is disposed near the water surface, and a support exterior 13 that is disposed so as to surround each microalgae culture unit 1 and supports a rotation shaft 35 (described later) of each frame 3. Note that, as shown in FIG. 2, one microalgae culture device 100 is configured by one microalgae culture unit 1, the power source 4, and wires 5 connecting each microalgae culture unit 1 to the power source 4.

[0019] The power supply device 12 (see FIG. 1) functions as a power supply means for supplying power to the power source 4 (the motor 41 in this embodiment). The power supply device 12 may be, for example, a photovoltaic power generation device having a solar panel. Also, without providing the power supply device 12, power may be provided to the power source 4 using an industrial power source or a general power source supplied from a power plant or the like.

[0020] The control device 11 is a computer terminal equipped with, for example, a control unit configured with a CPU, a ROM, a RAM, etc., and performing various calculations and control operations, a storage unit configured with a hard disk, a flash memory, etc., and allowing reading and writing of information, a communication unit configured with a LAN board, a WiFi unit, etc., and connected to the Internet by wire or wirelessly, and transmitting and receiving data, an input unit configured with a touch panel, a keyboard, a mouse, a push button, or a combination of these, and receiving input by touch operation, and a display unit configured with a liquid crystal display, an organic EL display, etc., and displaying images such as characters and figures. The control device 11, the power supply device 12, and the power source 4 are connected by wire or wirelessly. The power supply device 12 and the power source 4 are controlled by the control device 11 in terms of the output of power and the rotation speed of the motor 41. That is, the control device 11 functions as a control means for controlling the power source 4 and the power supply device 12. Furthermore, the control device 11 receives settings from the outside for periodic driving of the power source 4 (oscillation of the microalgae culture unit 1) at a certain time interval, such as "drive the motor 41 for five minutes once an hour," and controls the power supply device 12 and the power source 4. The control device 11 may be configured by other control devices such as a microcomputer or a tablet terminal.

[0021] The support exterior 13 (see FIG. 1) is disposed so as to surround each culture tank 2 and each frame 3, and supports the rotation shaft 35 (see FIG. 2) of each frame 3 (the culture tank 2 and the frame 3 will be described later). The support exterior 13 in this embodiment is formed by a plurality of frame connectors 131 and a support exterior framework 132 that connects the frame connectors 131. The framework connectors 131 are buoyant bodies (floats), and at least two or more are provided, one or more of which are fixed to the water tank 6, so that the movement of each culture tank 2, each frame 3, the power source 4, and the support exterior 13 is restricted. The framework connectors 131 may be, for example, columns fixed to the bottom surface of the water tank 6 like columns. The method of fixing to the water tank 6 may be, for example, fixing by anchors. The support exterior framework 132 has a longitudinal shape that linearly connects adjacent framework connectors 131 among the multiple framework connectors 131, and the rotation shaft 35 (see FIG. 2) is connected near the middle of the framework connectors 131. In this embodiment, a total of 15 framework connectors 131 are provided in 3 columns and 5 rows, and the power source 4 is provided in the center column at a position closest to the control device 11. The eight culture tanks 2 and frames 3 are each disposed at a position surrounded by the framework connectors 131 and the support exterior framework 132. The support exterior 13 supports the wires 5 that connect each frame 3 and the power source 4 so that they can be moved by rollers 5a in the pulling direction and the loosening direction (the payout / retraction direction).

[0022] As shown in Fig. 2, the power source 4 provides power for rocking the culture tank 2. In this embodiment, the power source 4 is composed of a motor 41 and a winch 42 that rotates by being driven by the motor 41. One end of a wire 5 is connected to each of the winches 42. The rotation direction of the winch 42 is the horizontal direction with the width direction as an axis.

[0023] One end of the wire 5 is connected to the power source 4, and the other end is connected to the frame 3, and both ends are pulled in the respective extension directions. The wire 5 is made of a material that is strong enough not to break due to the rocking of the culture tank 2 and does not stretch. To ensure such strength, the wire 5 can be made of, for example, metal or fiber. In this embodiment, one end of the wire 5 is connected to the winch 42, and the other end is fastened and connected to the power source connection framework 34 of the frame 3 of each microalgae culture unit 1 arranged in a horizontal straight line. Therefore, when the motor 41 rotates forward and backward to drive, the connection point of the winch 42 and the wire 5 rotates forward and backward around the horizontal direction, and the wire 5 reciprocates (pulls and releases), so that all the microalgae culture units 1 connected to the wire 5 rock around the rotation shaft 35.

[0024] The water tank 6 (see FIG. 2) has a box-like shape with an open top, and contains water to a sufficient depth inside. Each culture tank 2 (culture section 21) and each frame 3 (lower surface framework 31) are arranged near the water surface 60 of the water tank 6, so that the culture section 21 is approximately parallel to the water surface 60, and the whole or part of the culture section 21 is submerged in water. That is, the culture tank 2 and the frame 3 are arranged so that at least a part of the culture section 21 of the culture tank 2 is always below the water surface 60 (underwater) unless there is a change in the height of the water surface 60 due to waves or the like. In particular, in a stationary state (normal state where the culture section 21 is not rocked) in which the culture section 21 is approximately horizontal, the whole bottom surface of the culture section 21 is arranged so that it is below the water surface 60 (in contact with water). This provides a temperature stabilizing effect due to the temperature of the water in the water tank 6, and can suppress temperature changes of the culture solution 24 (culture medium) in the culture section 21 due to direct sunlight, outside air temperature, etc.

[0025] During the shaking of the culture tank 2, the gas storage unit connection valve 231 is always arranged to be above the water surface 60 (above the water) and above the upper surface of the culture solution 24, in other words, the connection part between the gas transfer path 230 and the internal space of the gas storage unit 22 is always arranged to be above the water surface 60 (above the water) and above the upper surface of the culture solution 24. This allows the gas transfer path 230 to efficiently transfer gas from the gas storage unit 22 to the culture unit 21, and prevents the culture solution 24 from flowing from the gas storage unit 22 to the culture unit 21 through the gas transfer path 230 and being unable to transfer the gas. The water tank 6 and the water or seawater therein have a depth sufficient to allow the frame 3 to rotate about the rotation shaft 35, and preferably have a sufficient amount of water to minimize temperature changes in the water due to sunlight and outside air temperature.

[0026] Alternatively, the culture tanks 2 and frames 3 may be disposed near the water surface 60 of a lake, a pond, or the sea without providing the water tank 6. As shown in FIG. 2, both axial ends of the rotation shaft 35 of the frame 3 may be connected to the inner surface of the water tank 6.

[0027] Figure 3 is an oblique view of the culture tank 2, frame 3, and wire 5 provided in the microalgae culture unit 1, Figure 4 is an oblique view of the culture tank 2 provided in the microalgae culture unit 1, and Figure 5 is a longitudinal cross-sectional view showing the culture tank 2 cut longitudinally at the positions of the outside air intake hole 222, the gas exhaust hole 223, and the culture medium supply and outlet port 224. In this specification, the vertical direction in Figure 3 (front / depth direction in Figure 2) refers to the vertical direction of the microalgae culture unit 1 and the microalgae culture system 10, the left / right direction in Figure 2 refers to the longitudinal direction of the microalgae culture unit 1, and the direction on a plane that is the same or parallel to the longitudinal direction and perpendicular to the longitudinal direction (the vertical direction in Figure 2) refers to the width direction of the microalgae culture unit 1.

[0028] As shown in FIG. 3, the culture tank 2 contains microalgae to be cultured and a culture solution 24, and is supported by a frame 3 (support).

[0029] The culture tank 2 is formed of a culture section 21 extending in the horizontal direction, a gas storage section 22 connected to the upper surface of the horizontal end of the culture section 21 and disposed above, and a gas transfer pipe 23 connecting the internal space 21d of the culture section 21 and the internal space 22d of the gas storage section 22. The gas storage section 22 may be configured to extend upward from a portion of the culture section 21. The culture tank 2 contains microalgae, a culture solution 24, and a gas containing carbon dioxide. The microalgae are contained in a state of being suspended in the culture solution 24.

[0030] The culture section 21 is formed by two rectangular flat sheets closed on three sides with no gaps, and a culture section opening 211 is provided on the remaining side. The culture section 21 is divided into three equal parts in the width direction (direction perpendicular to the longitudinal direction) by two partition parts 21b that are long in the longitudinal direction from the culture section opening 211 to the opposite tip part 21a, and three internal spaces 21d are provided. As a result, the culture section 21 is formed in the shape of three hollow bags. The culture section 21 is formed so that the width and longitudinal lengths are longer than the length in the thickness direction (vertical direction). The number of internal spaces 21d is not limited to three, and can be two or more. By providing a plurality of internal spaces 21d in this way, the microalgae are less likely to be biased to one side than when they are cultured in one wide internal space.

[0031] In this embodiment, the culture section 21 is formed by thermally welding three peripheries and two partitions 21b with the upper sheet and the lower sheet overlapping each other. In other words, the culture section 21 is configured by connecting three identical plastic bags in the width direction, which form the internal space 21d of the culture section 21. As a result, the culture section 21 has three internal spaces 21d. The three internal spaces 21d are each formed such that the length in the longitudinal direction is longer than the length in the width direction. Specifically, the width direction length may be 50 mm to 1000 mm, preferably 100 mm to 900 mm, and preferably 200 mm to 600 mm. The length in the longitudinal direction of the three internal spaces 21d may be 300 mm to 2000 mm, preferably 500 mm to 1500 mm, and preferably 800 mm to 1200 mm.

[0032] The culture unit 21 is provided with a culture unit connection valve 232 on the upper surface on the culture unit opening 211 side from the center in the longitudinal direction corresponding to each internal space 21d. One end of the gas transfer pipe 23 is connected to the culture unit connection valve 232. The culture unit connection valve 232 is attached in a sealed state to the culture unit 21 so that gas or liquid does not enter the internal space 21d from the outside. Therefore, external water (water in the water tank 6, rainwater, etc.) and outside air do not enter the culture unit 21 and the gas transfer pipe 23 through the culture unit connection valve 232.

[0033] The culture section 21 is made of sheet-like plastic (flexible soft resin) that is hard enough to naturally deform under gravity when part of it is supported from below. The culture section 21 in this embodiment is made of polyethylene, and more specifically, is formed of a three-layer film in which thin-film polyethylene, ethylene vinyl alcohol, and polyethylene are layered in this order. This allows the culture section 21 to function as a thin plastic bag.

[0034] Gas storage section 22 is a hollow box or oblong shape with an open bottom. The entire bottom surface is open to form gas storage section opening 221. Gas storage section opening 221 is shaped such that the entire bottom surface is open, and the bottom surface of one side surface on the culture section 21 side is open.

[0035] Gas accommodating section 22 has an outside air intake hole 222, a gas exhaust hole 223, and a culture solution supply / outlet port 224 formed on the upper surface. Gas accommodating section 22 also has a partition 225 therein that divides at least the lower part of internal space 22d into a plurality of parts in the width direction. Gas accommodating section 22 has a gas accommodating section connection valve 231 provided on the upper side (upper peripheral surface) of the gas accommodating section 22 on the culture section 21 side in the longitudinal direction of the culture section 21.

[0036] The outside air intake hole 222 and the gas exhaust hole 223 are each provided with a filter that covers the entire hole and allows gas to pass but does not allow liquid and aerosols in the atmosphere to pass through. The culture contaminants referred to here are substances that interfere with the culture of microalgae when mixed into the culture solution 24, such as aerosols in the atmosphere. This filter allows gas to pass through but does not allow liquid and solids to pass through. The outside air intake hole 222 and the gas exhaust hole 223 are not limited to being provided on the top surface of the gas storage section 22, but may be provided near the top end of the circumferential surface or in any other suitable position that does not contact the culture solution 24 in the gas storage section 22 even when it is rocked.

[0037] The partitions 225 are two plate-like members provided inside the gas storage section 22, and are formed of the same material as the exterior of the gas storage section 22. The two partitions 225 divide the gas storage section 22 into three equal parts in the width direction. The two partitions 225 are arranged so that the three internal spaces 21d of the culture section 21 and the three internal spaces 22d of the gas storage section 22 separated by the partitions 225 correspond to each other and communicate with each other. The partitions 225 do not completely separate the internal spaces 22d of the gas storage section 22, and have gaps 225a (see FIG. 5) at the top so that the three internal spaces 22d are connected near the outside air intake hole 222 and the gas exhaust hole 223. This allows gas to move between the three internal spaces 22d through the gaps 225a. Therefore, due to the presence of the gap 225a, the outside air intake hole 222 and the gas exhaust hole 223 allow the intake and exhaust of gas to all three internal spaces 22d.

[0038] The gas storage unit connection valve 231 is disposed above the upper surface of the culture solution 24 in the gas storage unit 22, and one end of the gas transfer tube 23 is connected to the gas storage unit connection valve 23. The gas storage unit connection valve 231 is attached in a sealed state to the culture unit 21 so that gas or liquid does not enter the internal space 21d from the outside. Therefore, external water (water in the water tank 6, rainwater, etc.) and outside air do not pass through the gas storage unit connection valve 231 and enter the gas storage unit 22 and the gas transfer tube 23. The gas storage unit connection valve 231 may be provided with a valve that restricts the direction of gas movement. In detail, the gas storage section connection valve 231 may be provided with a valve configured to allow gas in the gas storage section 22 (internal space 22d) to move into the gas transfer tube 23 (gas transfer path 230), but conversely not allow gas in the gas transfer tube 23 (gas transfer path 230) to move into the gas storage section 22 (internal space 22d).

[0039] The gas storage section 22 is made of weather-resistant hard plastic such as acrylic resin. The gas storage section 22 can be made of an appropriate material such as plastic (rigid hard resin) that is hard enough not to deform due to gravity even when supported from below, or sheet-like plastic (flexible soft resin) that is hard enough to naturally deform due to gravity when part of it is supported from below.

[0040] The culture section 21 and the gas storage section 22 thus configured are connected so that their insides communicate with each other. More specifically, the dimensions (inner diameter) around the culture section opening 211 of the culture section 21 are formed to be the same dimensions (same as the outer size in the circumferential direction) as the bottom surface of the gas storage section 22 so that the culture section 21 can be connected to the gas storage section 22 without any gaps, and the lower part of the gas storage section 22 is inserted into the culture section opening 211 and connected without any gaps, and fixed by a fixing band 212. In this embodiment, a plastic band is used as the fixing band 212. As a fixing method, a band such as a plastic band or a rubber band may be used, or the fixing may be bonded with an adhesive, so long as the culture solution 24 contained therein does not leak out or is not released due to the impact of the shaking. In addition, it is preferable to fix the entire circumference of the culture section opening 211 in the culture section 21 to the gas storage section 22 with tape or by bonding, so that the culture solution 24 and the microalgae contained therein do not leak out.

[0041] The gas transfer pipe 23 is a hose-like pipe curved from a cylindrical shape, and has a hollow gas transfer path 230 (see FIG. 6a) inside. One end of the gas transfer pipe 23 is connected to the gas storage part connection valve 231 on the upper side surface of the gas storage part 22 so as to be approximately horizontal, and the other end is connected to the culture part connection valve 232 on the upper surface of the culture part 21 so as to be approximately vertical. Three gas transfer pipes 23 are provided so as to connect three internal spaces 22d of the gas storage part 22 to three internal spaces 21d of the corresponding culture part 21 by the gas transfer path 230. Therefore, the gas transfer pipe 23 (gas transfer path 230) allows the transfer of gas from the gas storage part 22 to the culture part 21 outside the communicating part of the gas storage part 22 and the culture part 21. The gas transfer pipe 23 is preferably formed of a flexible material. In this embodiment, the gas transfer tube 23 is made of plastic (flexible resin) that is hard enough to be deformed by a light force, such as that of a human hand.

[0042] In this embodiment, the gas transfer path 230 is cylindrical, but may have any shape as long as the gas can move. However, it is preferable that the gas transfer path 230 is formed in a shape and a thickness (inner diameter) that is not hindered from moving by clogging the culture solution 24 and the microalgae contained in the culture solution 24 that have entered the gas transfer path 230 due to the rocking of the microalgae culture unit 1. The thickness (inner diameter) of such a gas transfer path 230 can be 2 mm to 50 mm, preferably 5 mm to 30 mm, and preferably 10 mm to 20 mm. In this embodiment, the thickness (inner diameter) of the gas transfer path 230 is 10 mm.

[0043] The frame 3 (support) is made of hard plastic (rigid plastic) that is hard enough not to be deformed by light force such as that of a human hand. The frame 3 in this embodiment is made of polyvinyl chloride, which has sufficient strength and durability.

[0044] The frame 3 is a rectangular frame when viewed from above, and is formed into an L-shape when viewed from the rear (from the back to the front in Figure 3) by connecting one side of the frame to the other so that the whole is arranged at a right angle, with a bottom framework 31 which is slightly larger than the culture tank 2 (culture section 21) and a side framework 32 which is slightly larger than the culture tank 2 when viewed from the left side (the direction when looking at the gas storage section 22 from the culture section 21).

[0045] The lower surface framework 31 has two rod-shaped lower surface inner frameworks 310 that are long in the longitudinal direction (left and right direction in FIG. 3) of the culture section 21 on the same plane as the outer frame. A rod-shaped intermediate framework 33 that is long in the vertical direction is provided on the upper surface of the outer frame of the lower surface framework 31 at the longitudinal center position, and the upper ends of the intermediate frameworks 33 are connected to each other by a rod-shaped power source connection framework 34 that is long in the width direction. The vertical height of the intermediate framework 33 is configured to be slightly higher than the vertical height of the side framework 32. The intermediate framework 33 and the side framework 32 are connected by two rod-shaped connection frameworks 37 that are long in the longitudinal direction. In addition, the two intermediate frameworks 33 have a rod-shaped rotation axis 35 that is long (in the width direction) parallel to the power source connection framework 34.

[0046] The rotation shaft 35 is disposed below the center of the height of the intermediate framework 33, and more preferably below the lower ¼ of the height of the intermediate framework 33. This positions the rotation shaft 35 above and close to the culture unit 21, increasing the rocking angle of the culture unit 21. In other words, the further upward the rotation shaft 35 is from the culture unit 21, the greater the rocking motion of the culture unit 21 in the longitudinal direction, and the shorter the rocking distance of the tip 21a in the vertical direction. However, by bringing the rotation shaft 35 as close as possible to the culture unit 21, the rocking distance of the tip 21a of the culture unit 21 in the vertical direction is increased.

[0047] Moreover, the intermediate framework 33, the power source connection framework 34, and the rotating shaft 35 are provided on the side framework 32 side from the center in the longitudinal direction (left and right direction in FIG. 3) of the bottom framework 31. In this embodiment, they are provided at a position about 1 / 3 of the way toward the side framework 32 side in the longitudinal direction of the bottom framework 31. By providing the rotating shaft 35 closer to the side framework 32 side from the center of the bottom framework 31 in this way, i.e., closer to the gas storage section 22 side from the longitudinal center of the culture section 21, the distance over which the tip portion 21a of the culture section 21 moves up and down due to rocking becomes longer, and the culture section 21 rocks more greatly even with the same rocking angle.

[0048] The side frame 32 is a rectangular frame when viewed from the left side (the direction when gas storage section 22 is viewed from culture section 21), and a rod-shaped side inner frame 321 that is long in the width direction is provided at the vertical middle position. The rod-shaped material that is a component of the frame 3 may be any suitable rod-shaped material, such as a cylindrical, square tube, columnar, or rectangular prism.

[0049] The culture tank 2 is fixed to the frame 3. In this embodiment, the bottom framework 31 and the culture section 21 are fixed, and the side framework 32 and the gas storage section 22 are fixed. In this embodiment, the bottom framework 31 and the culture section 21 are fixed by wire, and the side framework 32 and the gas storage section 22 are fixed by a plastic band. In more detail, an eyelet 21h is formed in the end 21c (see FIG. 4), which is the adhesive edge portion (glue portion) of the plastic bag forming the culture section 21, and a wire is passed through this eyelet 21h and fastened to the bottom framework 31.

[0050] The fixing bands 212 are arranged so as to wrap the side framework 32 and the gas storage unit 22 together in the horizontal direction at two locations, top and bottom. The lower one of the two fixing bands 212 is the same as the fixing band 212 that fixes the culture unit 21 and the gas storage unit 22. This lower fixing band 212 is wrapped around two times, fixing the culture unit 21 and the gas storage unit 22 in the first turn, and fixing the culture tank 2 and the frame 3 in the second turn.

[0051] One end of a wire 5, the other end of which is connected to a power source 4, is connected to the power source connection framework 34 (see FIG. 3). Note that a wire, the other end of which is connected to the upper surface of the culture section 21, may also be connected to the power source connection framework 34.

[0052] Both ends of the rotating shaft 35 are rotatably supported by bearings 61 (see FIG. 2) provided in the water tank 6, and sliding movement in the horizontal and vertical directions is restricted. The rotating shaft 35 is also formed to rotate integrally with the frame 3 including the intermediate framework 33. Therefore, the frame 3 and the culture tank 2 are restricted from sliding movement in the horizontal and vertical directions, and rotate (swing) about the rotating shaft 35.

[0053] Next, the operation of the microalgae culture system 10 in which the culture tank 2 is rocked will be described. Figure 6a is a vertical cross-sectional view showing the culture tank 2 and culture solution 24 in a stationary state in the microalgae culture device 100 of Figure 2, Figure 6b is a vertical cross-sectional view showing the culture tank 2 and culture solution 24 during rocking, Figure 6c is a vertical cross-sectional view of the culture tank 2 and culture solution 24 in a state where the angle change due to rocking is at its maximum (second state), and Figure 6d is a vertical cross-sectional view of the culture tank 2 and culture solution 24 in a state where the angle change towards the other side due to rocking is at its maximum (first state).

[0054] As shown in Fig. 6a, in a stationary state, the culture tank 2 has the culture section 21 fixed at an angle parallel to the horizontal direction by the frame 3 and the wire 5. The wire 5 is pulled from both ends in the direction of its extension by the winch 42 and the frame 3, and the wire 5, winch 42, frame 3, and culture tank 2 are in a stationary state with the pulling forces balanced. At this time, the culture solution 24 fills the internal space 21d of the culture unit 21 in the horizontal state, and no gas is present in the internal space 21d of the culture unit 21, or gas is present in a very small area of ​​10% or less. That is, the culture unit 21 corresponds to the portion of the internal space 21d filled with the culture solution 24 when the culture tank 2 is in a stationary state. The upper part of the internal space 22d of the gas storage unit 22 (the internal space of the upper end 25 of the culture tank 2) is occupied by a gas containing carbon dioxide. That is, the gas storage unit 22 corresponds to the portion of the internal space 22d on the upper surface side of the culture solution 24 that is filled with gas (carbon dioxide) when the culture tank 2 is in a stationary state. 6a shows a stationary state in which the culture tank 2 is stationary and culture is promoted, and the culture section 21 is kept approximately horizontal. "Approximately horizontal" means that the surface direction in which the culture section 21 spreads (a plane perpendicular to the thickness direction, which is the height) is within a range of ±10 degrees from the horizontal.

[0055] As shown in FIG. 6b, when the motor 41 is driven and the winch 42 rotates in either the forward or reverse direction, the wire 5 is pulled toward the frame 3 and moves. At this time, the culture tank 2 is fixed by the frame 3, and the frame 3 is rotatably fixed by the rotating shaft 35 (and the water tank 6 connected to the rotating shaft 35), and movement in the horizontal direction, width direction, and up and down direction is restricted. Therefore, the frame 3 moves as if pulling the wire 5, but since movement in the horizontal direction is restricted, it rotates around the rotating shaft 35. At this time, the volume of the culture solution 24 rises so as to narrow the gas presence region (upper space) in the internal space 22d of the gas storage section 22 as seen from the culture tank 2, and the gas that filled the upper space is discharged from the gas transfer path 230 and the gas discharge hole 223 as if it is pushed out by the water pressure of the culture solution 24. Here, since the gas discharge hole 223 is provided with a filter that allows gas to pass but does not allow liquids and solids to pass through, all of the discharged gas is not discharged to the outside from the gas discharge hole 223, and at least a part of the gas is reliably discharged from the gas transfer path 230 into the culture section 21 (internal space 21d). The gas that has passed through the gas transfer path 230 is discharged into the culture section 21 to which it is connected, passes through the culture solution 24, and remains in the internal space 21d of the tip 21a of the culture section 21 that has been raised by rotation.

[0056] As shown in FIG. 6c, when the motor 41 is further driven from FIG. 6b and the winch 42 further rotates in the same direction as FIG. 6b, the culture tank 2 and the frame 3 further rotate from the state of FIG. 6b, and the angle change in one direction becomes maximum (second state). In this second state, the culture unit 21 is inclined at a predetermined angle from the horizontal state so that the tip 21a is upward. At this time, the volume of the culture solution 24 rises so as to further narrow the gas presence region in the internal space 22d of the gas storage unit 22 as viewed from the culture tank 2, and accordingly the gas that filled the gas storage unit 22 (internal space 22d) is further pushed out into the gas transfer path 230 by the water pressure of the culture solution 24 and moves into the culture unit 21.

[0057] After that, as shown in FIG. 6d, when the motor 41 is driven in the opposite direction from the state of FIG. 6c in the direction shown in FIG. 6b and FIG. 6c, and the winch 42 rotates in the other direction (opposite direction from the one direction), the wire 5 moves as if pulled toward the winch 42, and the culture tank 2 and the frame 3 rotate in the other direction, passing the angle of the stationary state and reaching a state (first state) where the angle change to the other direction is maximum. In this first state, the culture unit 21 is inclined at a predetermined angle so that the tip 21a is downward from the horizontal state. When the culture tank 2 transitions (rotates, moves) from the second state to the first state, the gas that has stayed in the culture unit 21 passes through the gas transfer path 230 or moves along the upper surface of the culture unit 21 to the gas storage unit 22 side and stays in the gas storage unit 22 again. Also, when transitioning from the second state to the first state, a small amount of the culture liquid 24 moves in the gas transfer path 230 so as to be sucked up toward the internal space 22d of the gas storage unit 22 in a reduced pressure state. Furthermore, fresh outside air is taken into the internal space 22d of the gas storage section 22 through the outside air intake hole 222.

[0058] Thereafter, the motor 41 is repeatedly driven in one direction and the other direction, and the winch 42 is repeatedly rotated in one direction and the other direction in response to the driving of the motor 41, so that the culture tank 2 rotates (swings) by repeating the transition between the first state and the second state several times. Therefore, the first state and the second state are states in which the rotatable angle (swing range) of the culture tank 2 is maximum in each direction. In addition, in the first state, the tip 21a of the culture unit 21 is at the lowest position within the swing range, and in the second state, the tip 21a of the culture unit 21 is at the highest position within the swing range. Finally, in the middle of the transition between the first state and the second state, the culture tank 2 stops at the same position (angle) as in the stationary state, and returns to the stationary state (see FIG. 6a).

[0059] By such an operation, the culture solution 24 and the microalgae contained therein are agitated by the rocking of the culture tank 2 and the gas passing through the culture solution 24. In addition, gas is supplied to the microalgae. During a series of rocking of the culture tank 2, the upper end 25 of the gas storage section 22 and the tip 21a of the culture section 21 are always separated by the culture solution 24, and the path through which the gas moves between them is the gas transfer path 230 and near the ceiling surface of the culture section 21. Therefore, regardless of whether the culture tank 2 is in the first state or the second state, it always has a connection section 27 (the range of the dashed lines shown in Figures 6a, 6b, and 6c) where the culture solution 24 and the microalgae in the culture solution 24 are retained. The connection section 27 is located below the gas transfer path 230. In other words, the gas transfer path 230 is provided above the connection section 27.

[0060] Furthermore, by the rocking of the culture tank 2, part of the gas filling the internal space 22d of the gas storage unit 22 is discharged from the gas discharge hole 223, and fresh outside air is taken into the internal space 22d from the outside air intake hole 222. This gas exchange phenomenon occurs naturally by the rocking of the culture tank 2, so no device for gas exchange such as aeration is required. Furthermore, no adjustment tank is required for temporarily storing the microalgae and the culture solution 24 during gas exchange.

[0061] The control device 11 (see FIG. 1) alternates between a stationary state in which the motor 41 is stopped and the culture tank 2 is also stationary, and a rocking state in which the motor 41 is rotated to rock the culture tank 2 and agitate the culture solution 24 and the microalgae in the culture tank 2, at a predetermined cycle. The time for the stationary state is preferably longer than the time for the rocking state, more preferably at least twice the time for the rocking state, and even more preferably at least four times the time for the rocking state. In this way, it is possible to ensure as long a time for culture in a stationary state as possible, and to provide carbon dioxide to the microalgae by performing appropriate agitation.

[0062] With the above configuration, it is possible to provide a microalgae culture device, culture system, and culture method that enable mass production of valuable microalgae while simultaneously protecting the environment. The microalgae culture device 100 is configured such that the culture tank 2 is rocked by the power source 4 so as to form a first state in which the tip 21a of the culture unit 21 farthest from the gas storage unit 22 is at the lowest position within the rocking range, and a second state in which the tip 21a of the culture unit 21 is at the highest position within the rocking range, and in the process of transitioning from the first state to the second state, the gas in the gas storage unit 22 moves into the culture unit 21, and in the process of transitioning from the second state to the first state, the gas that has moved into the culture unit 21 moves into the gas storage unit 22. With this configuration, the rocking of the culture tank 2 causes the gas (carbon dioxide) used in the culture to move from the gas storage unit 22 into the culture unit 21, and then the operation of moving from the culture unit 21 into the gas storage unit 22 is repeated. As a result, the microalgae culture device 100 can culture the microalgae while intermittently feeding gas (carbon dioxide) into the culture solution 24 by moving the gas into the culture solution 24, in addition to agitating the culture solution 24 and the microalgae by rocking, thereby promoting the growth of the microalgae. Furthermore, the microalgae culture device 100 of the present invention is a low-carbon technology that performs biological production by absorbing carbon dioxide discharged into the environment. Therefore, it is possible to culture valuable microalgae while simultaneously mass-producing them and protecting the environment.

[0063] In addition, in the stationary culture tank 2, the internal space 21d of the culture section 21 in the substantially horizontal position is filled with the culture solution 24 containing the microalgae. With this configuration, the light necessary for the photosynthesis of the microalgae can be received over a wide range, and the efficiency of the culture can be improved.

[0064] Furthermore, the culture tank 2 and the frame 3 are arranged so that at least a part of the culture section 21 of the culture tank 2 is always below the water surface 60 (underwater) unless the height of the water surface 60 changes due to waves or the like. With this configuration, even if the microalgae culture unit 1 is installed outdoors, the temperature of the culture solution 24 is buffered by the water temperature in the water tank 6, and the temperature of the culture solution 24 does not become excessively high or low due to the outside air temperature, allowing stable cultivation of microalgae. Also, it allows efficient use of places with a large area and no objects on top, such as reservoirs or on the sea.

[0065] Furthermore, the width of the entire internal space 21d of the culture unit 21 is shorter than the length in the longitudinal direction. With this configuration, when the culture tank 2 is rocked, the microalgae and culture solution 24 contained in the culture unit 21 are not significantly biased in the width direction, and can move a long distance within the culture tank 2 while being agitated by the rocking.

[0066] In addition, the culture tank 2 has an outside air intake hole 222 for taking in outside air into the internal space 22d, and a gas exhaust hole 223 for exhausting gas remaining in the internal space 22d, at the upper end 25 of the gas storage unit 22. With this configuration, the gas in the upper end 25 of the gas storage unit 22 is exhausted from the gas exhaust hole 223 as if pushed out by the movement of the culture solution 24 due to the rocking of the culture tank 2, and outside air is taken in from the outside air intake hole 222 as if inhaled. That is, gas in which carbon dioxide has been consumed by photosynthesis of the microalgae is exhausted, and outside air containing a large amount of carbon dioxide is taken in. Then, this series of gas exchanges is naturally performed by the rocking of the culture tank 2. Therefore, aeration for gas exchange and an adjustment tank for temporarily storing the microalgae and the culture solution 24 for gas exchange are not required, and the microalgae culture device 100 and the microalgae culture system 10 can be made small and inexpensive.

[0067] The culture tank 2 also includes a gas transfer path 230 that connects the culture unit 21 and the gas storage unit 22, and is configured such that, during the process in which the culture tank 2 transitions from the first state to the second state, the gas in the gas storage unit 22 moves through the gas transfer path 230 into the culture unit 21. With this configuration, the gas can be efficiently transferred from the gas storage unit 22 to the culture unit 21.

[0068] Furthermore, the gas transfer path 230 is connected to the gas accommodation section 22 at a height above the water surface via the gas accommodation section connection valve 231 regardless of whether the culture tank 2 is in the first state or the second state. With this configuration, in the internal space of the gas accommodation section 22, a gas presence region is always located at the height where the gas accommodation section connection valve 231 is located. Therefore, the gas can be efficiently transferred from the gas accommodation section 22 to the culture section 21.

[0069] In addition, the culture section 21 of the culture tank 2 is formed of a sheet-like soft resin (flexible soft resin) that is hard enough to naturally deform under gravity when a part of it is supported from below. As a result, even if the culture section 21 of the culture tank 2 is repeatedly slammed against the water surface 60 due to violent movement caused by strong winds or comes into contact with drifting objects at sea, the culture section 21 is less likely to be damaged due to the flexible deformation characteristic of soft resin, and the durability of the culture tank 2 and the microalgae culture unit 1 can be improved. In addition, if the gas storage section 22 is also formed of a flexible soft resin, the gas storage section 22 can also achieve the same effect. With this configuration, the manufacturing cost per microalgae culture unit 1 is cheaper than when hard plastic is used, and in particular, the microalgae culture system 10 and the microalgae culture device 100 having a plurality of culture tanks 2 can be manufactured inexpensively.

[0070] Furthermore, the power source 4 controls the rocking of the culture tank 2 between the first state and the second state, and creates a stationary state between the first state and the second state in which the culture tank 2 is stationary and the culture unit 21 is kept substantially horizontal. With this configuration, it is possible to efficiently culture the microalgae by appropriately switching between a stationary state that promotes the cultivation of the microalgae and a rocking state that agitates the microalgae and the culture solution 24 and supplies carbon dioxide to the microalgae.

[0071] The microalgae culture system 10 is configured by connecting a plurality of microalgae culture devices 100. This configuration makes it possible to utilize a large area, such as the ocean, while actively recovering nutrients from a large amount of sludge and wastewater present in the sea or on the seabed, and mass-producing valuable microalgae.

[0072] It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and many other embodiments can be obtained. For example, in this embodiment, the rotation shaft 35 is provided on the frame 3, and the culture tank 2 is rotated (rocked) around the rotation shaft 35, but the rotation shaft 35 may be provided somewhere other than the frame 3. In other words, as long as the culture tank 2 is configured to be rocked around the rotation shaft 35, the position of the rotation shaft 35 is not particularly limited.

[0073] The culture tank 2 of this embodiment is composed of the culture section 21 extending in the horizontal direction and the gas storage section 22 extending upward from the end of the culture section 21, and has an L-shaped or inverted L-shaped shape when viewed horizontally, but for example, the gas storage section 22 may be formed to extend upward from near the center of the culture section 21, and may have a convex shape when viewed horizontally. In this case, in addition to the first gas transfer path 230 provided to connect the upper end (upper end 25) of the gas storage section 22 and one end (tip 21a) of the culture section 21 in the horizontal direction, a second gas transfer path 230 may be provided that connects the upper end 25 of the gas storage section 22 and the culture section 21 on the side of the second tip 21a, with the other end of the culture section 21 in the horizontal direction being the second tip 21a.

[0074] In addition, in the culture tank 2 of this embodiment, the culture unit 21 and the gas storage unit 22 are configured with separate members, but the culture unit 21 and the gas storage unit 22 may be integrated as one member to form the culture tank 2. In such a case, the culture unit 21 corresponds to the part in which the internal space 21d is filled with the culture liquid 24 when the culture tank 2 is in a stationary state. And, the gas storage unit 22 corresponds to the part in which the internal space 22d on the upper side of the culture liquid 24 is filled with gas (carbon dioxide) when the culture tank 2 is in a stationary state. In addition, when the culture unit 21 and the gas storage unit 22 are integrally molded, it is preferable to mold them with a soft material such as a soft resin. If the culture unit 21 and the gas storage unit 22 are integrally formed with a soft material, the microalgae culture system 10 and the microalgae culture device 100, which are provided with a plurality of culture tanks 2, can be manufactured at a lower cost.

[0075] Also, the gas transfer pipe 23 (gas transfer path 230) may not be provided. In this case, the gas storage section 22 is not provided with a gas storage section connection valve 231, and the side surface on the culture section 21 side in the longitudinal direction of the culture section 21 is a flat surface without holes. Also, the culture section 21 is not provided with a culture section connection valve 232, and the upper surface on the culture section opening 211 side is a flat surface without holes. Also, in this case, it is preferable to reduce the amount of culture solution 24 in the culture tank 2 including the culture section 21. Specifically, it is preferable that the water level of the culture solution 24 is slightly higher than the upper surface of the culture section 21 when the culture section 21 is in a substantially horizontal state, or is approximately the same as the water level 60 in FIG. 6(a).

[0076] In this case, when the culture section 21 tilts from a horizontal, stationary state (Figure 6a) to a second state (Figure 6c), the gas storage section 22 moves downward, and the culture liquid 24 moves by gravity through the connecting section 27 to the gas storage section 22, and conversely, the gas in the gas storage section 22 moves through the upper part of the connecting section 27 to the culture section 21.

[0077] Furthermore, when the culture section 21 returns from the second state (Figure 6c) to the horizontal stationary state (Figure 6a), the culture fluid 24 moves by gravity from the gas storage section 22 to the culture section 21 through the connecting section 27, and the gas in the culture section 21 moves through the top of the connecting section 27 to the gas storage section 22.

[0078] Furthermore, when the culture section 21 tilts from a horizontal, stationary state (Figure 6a) to the first state (Figure 6d), the culture section 21 drops downward, and the culture fluid 24 moves by gravity through the connecting section 27 to the culture section 21, and conversely, the gas remaining in the culture section 21 moves through the upper part of the connecting section 27 to the gas storage section 22.

[0079] In this way, even if the gas transfer path 230 is not provided, by adjusting the amount of the culture solution 24, the same effect as in the embodiment can be obtained. In addition, when the gas transfer path 230 is not provided, it is preferable to increase the inclination of the first state and the second state to increase the rocking angle, thereby making it possible to more reliably transfer the culture solution 24 and the gas between the culture section 21 and the gas storage section 22. [Industrial Applicability]

[0080] INDUSTRIAL APPLICABILITY The present invention can be used for the manufacture and sale of a culture device for housing and culturing microalgae in a culture tank, and for culturing microalgae. [Explanation of symbols]

[0081] 1. Microalgae cultivation unit 2…Culture tank 21...Cultivation Department 21a...Tip 22...Gas storage section 230...Gas transfer path 24…Culture solution 25...Top end 3. Frame 35…Rotation axis 4...Power source 5…Wire 6. Aquarium 10. Microalgae cultivation system 11...Control device 12…Power supply device 13…Support sheathing 100...Microalgae culture device

Claims

1. The present invention relates to a culture tank that contains microalgae to be cultured, a culture solution, and a gas used for culture, a support that supports the culture tank so that the culture tank can be oscillated while at least a portion of the culture tank is located under the water surface, and a power source that oscillates the culture tank. The culture tank includes a culture section that has a portion under the water surface and has an area in the surface direction of the water surface and contains the microalgae and the culture solution, and a gas storage section that communicates with the culture section and stores the gas. The power source causes a tip of the culture section farther from the gas storage section to move in the direction of the oscillation. A microalgae culture device that agitates a culture solution by rocking the culture tank to form a first state in which the tip of the culture unit is at the lowest position within a range of the oscillation and a second state in which the tip of the culture unit is at the highest position within the range of the oscillation, and in the process of transitioning from the first state to the second state, gas in the gas storage unit moves into the culture unit, and in the process of transitioning from the second state to the first state, the gas that has moved into the culture unit moves back into the gas storage unit, thereby agitating the culture solution, wherein the culture unit is formed of a flexible soft resin.

2. The microalgae culture device according to claim 1 , wherein the gas storage unit is provided with an outside air intake hole for taking in gas from outside the device and a gas exhaust hole for exhausting gas to the outside of the device.

3. A microalgae culture device as described in claim 1 or 2, comprising a gas transfer path that connects the culture section and the gas storage section, and in the process of transitioning from the first state to the second state, the gas in the gas storage section moves through the gas transfer path into the culture section.

4. The microalgae culture device according to claim 3 , wherein the gas transfer passage is connected to the gas storage section at a height above the water surface in either state.

5. The power source controls the oscillation of the culture tank between a first state and a second state, and creates a stationary state between the first state and the second state in which the culture tank is stationary and the culture section is kept in an approximately horizontal state. The microalgae culture device according to any one of claims 1 to 4.

6. A microalgae culture system comprising: the microalgae culture device according to any one of claims 1 to 5; a control means for controlling a power source; and a power supply means for supplying power to the power source.

7. The microalgae culture system according to claim 6 , wherein a plurality of microalgae culture devices are connected to each other.

8. A method for culturing microalgae using a microalgae culture device comprising: a culture tank that contains microalgae to be cultured, a culture solution, and a gas used for the culture; a support that supports the culture tank so that the culture tank can be oscillated while at least a portion of the culture tank is located under the water surface; and a power source that oscillates the culture tank, the culture tank comprising a culture section that has a portion under the water surface and has an area in a surface direction of the water surface and contains the microalgae and the culture solution; and a gas storage section that is connected to the culture section and stores the gas, A microalgae cultivation method comprising: rocking the culture tank to form a first state in which the tip of the culture section is at the lowest position within the rocking range; and a second state in which the tip of the culture section is at the highest position within the rocking range; during the process of transitioning from the first state to the second state, gas in the gas storage section moves into the culture section; and during the process of transitioning from the second state to the first state, the gas that has moved into the culture section moves back into the gas storage section, thereby stirring the culture solution; wherein the culture section is formed of a flexible soft resin.

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