Algae cultivation system and algae cultivation method using the same

Abstract

To provide an algae cultivation system that can efficiently cultivate algae in various seaweed beds, whether in the ocean, on land, or in laboratories, and to provide a method for cultivating algae using the system.SOLUTION: The algae cultivation system of the present invention comprises: a culture area; immobilization means immersed in the culture area and capable of immobilizing algae; and fine bubble supply means immersed in the culture area. The fine bubble supply means generates fine bubbles containing 2.1 vol.% or more of carbon dioxide. According to the present invention, by increasing the carbon dioxide concentration in the culture area, algae can be cultivated efficiently. Furthermore, by monitoring the carbon dioxide concentration in the culture area, it is possible to control the carbon dioxide concentration in the culture area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an algae cultivation system and a method for cultivating algae using the same. [Background technology]

[0002] Algae can be cultivated in a wide range of water bodies, including the ocean, and are attracting attention as plants that can absorb CO2 and become carbon neutral, leading to the solution of the global warming problem. Among these, large algae such as Akamoku (Sargassum horneri (Turner) C. Agardh) are particularly excellent at fixing CO2, and are also useful biomass in themselves.

[0003] Typical uses of macroalgae include food ingredients, fertilizers, and cosmetic ingredients, and in recent years they have also attracted attention as a raw material for producing bioethanol.

[0004] Traditionally, most algae cultivation has been carried out in marine seaweed beds. However, due to the expansion of uses and demand as mentioned above, algae are now grown (cultured) from their juvenile stage in land-based seaweed farms in addition to marine seaweed beds.

[0005] Given this background, there is a need for technological development that can realize more efficient algae cultivation. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to solve the above-mentioned problems, and its purpose is to provide an algae cultivation system that can efficiently cultivate algae in various seaweed beds such as those in the ocean, on land, and in laboratories, and a method for cultivating algae using the same. [Means for solving the problem]

[0007] The present invention provides an algae cultivation system, comprising: A culture water area; an algae fixing means immersed in the culture water area; a fine bubble supply means immersed in the culture water area; Equipped with In this algae cultivation system, the fine bubble supplying means generates fine bubbles containing 2.1% by volume or more of carbon dioxide gas.

[0008] In one embodiment, the fine bubble supplying means intermittently supplies the fine bubbles to the culture water area.

[0009] In one embodiment, the fine bubbles are composed of artificial air containing 2.1% by volume or more and 100% by volume or less of carbon dioxide gas.

[0010] In one embodiment, the cultivation area is an open water area.

[0011] In one embodiment, the cultivation body is a closed body of water.

[0012] In one embodiment, the algae cultivation system of the present invention further comprises a detector for monitoring the carbon dioxide concentration contained in the cultivation water area.

[0013] In one embodiment, the detector and the fine bubble supply means are electrically connected via a computer, and the computer generates fine bubbles from the fine bubble supply means in accordance with the carbon dioxide concentration detected by the detector.

[0014] The present invention also provides a method for culturing algae, comprising the steps of: A step of fixing algae to a fixing means constituting the algae culture system; generating fine bubbles from a fine bubble supply means in the culture water area; The method includes:

[0015] In one embodiment, the method further comprises the step of monitoring the carbon dioxide concentration in the culture water area and stopping the generation of fine bubbles from the fine bubble supply means when the carbon dioxide concentration exceeds a threshold value. [Effects of the Invention]

[0016] According to the present invention, algae can be efficiently cultivated by increasing the carbon dioxide concentration in the culture water area. Furthermore, by monitoring the carbon dioxide concentration in the culture water area, it is possible to control the carbon dioxide concentration in the culture water area. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of an algae cultivation system of the present invention, in which the cultivation water area is a closed water area. [Figure 2] FIG. 1 is a schematic diagram showing another example of the algae cultivation system of the present invention, in which the cultivation water area is a closed water area. [Figure 3] FIG. 2 is a schematic diagram showing another example of the algae cultivation system of the present invention, in which the cultivation water area is a closed water area. [Figure 4] FIG. 10 is a schematic diagram showing yet another example of the algae cultivation system of the present invention, in which the cultivation water area is an open water area. [Figure 5] FIG. 10 is a schematic diagram showing yet another example of the algae cultivation system of the present invention, in which the cultivation water area is an open water area. [Figure 6] 1 is a photograph showing juveniles of Sargassum horneri (cultured for 11 days) on a polystyrene block, which were cultured and grown using the algae culture system of the present invention in Example 1. [Figure 7] (a) is a photograph showing Sargassum serrata fixed onto a twisted string on the 0th day of cultivation (at the start of cultivation) using the algae cultivation system of Example 2, (b) is a photograph showing Sargassum serrata fixed onto a twisted string on the 15th day of cultivation, and (c) is a photograph showing Sargassum serrata fixed onto a twisted string on the 27th day of cultivation. [Figure 8](a) is a photograph showing Sargassum serrata fixed onto a twisted string on the 0th day of cultivation (at the start of cultivation) using the algae cultivation system of Comparative Example 1, (b) is a photograph showing Sargassum serrata fixed onto a twisted string on the 15th day of cultivation, and (c) is a photograph showing Sargassum serrata fixed onto a twisted string on the 27th day of cultivation. [Figure 9] 1 is a graph showing the mass change (relative value) versus the culture period (days) for Sargassum horneri cultured in Example 3 and Sargassum horneri cultured in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Algae cultivation system) The algae cultivation system of the present invention will now be described with reference to the accompanying drawings, in which like reference numerals are used throughout the following drawings to designate components that are similar to those shown in the other drawings.

[0019] FIG. 1 is a schematic diagram showing an example of the algae culture system of the present invention.

[0020] The algae cultivation system 100 shown in FIG. 1 comprises a cultivation water area 110, an algae fixing means 120, and a fine bubble supplying means .

[0021] The culture water area 110 shown in FIG. 1 is a so-called closed water area formed by containing a culture solution in a culture tank 112.

[0022] The culture medium contains water (e.g., natural or artificially produced, including seawater, brackish water, and freshwater) and, if necessary, various components (e.g., nutrient enrichment components, iron components, trace metal components, pH buffer components, and inorganic salts, and combinations thereof).

[0023] Examples of nutritional enrichment components include sodium nitrate, Na2-glycerophosphate, and combinations thereof. An example of an iron component is chelated iron (Fe(EDTA)). Trace metal components include potassium iodide, boric acid, iron chloride, manganese chloride, zinc chloride, and cobalt chloride, and combinations thereof. An example of a pH buffer component is trishydroxymethylaminomethane (Tris). Examples of inorganic salts include sodium chloride, magnesium chloride, calcium chloride, anhydrous sodium sulfate, potassium chloride, sodium bicarbonate, potassium bromide, borax, anhydrous strontium chloride, sodium fluoride, lithium chloride, potassium iodide, manganese chloride, cobalt chloride, aluminum chloride, ferric chloride, sodium tungstate, and ammonium molybdate, and combinations thereof. The amount (concentration) of each component contained in the culture medium is not particularly limited and can be appropriately selected by those skilled in the art.

[0024] The culture tank 112 is, for example, any tank or container that can be used for land-based aquaculture or laboratory use, and its material, etc. is not particularly limited. The culture tank 112 is made of a material and has a shape that can supply the light necessary for algae photosynthesis, and has, for example, a shape that is open at the top.

[0025] The size of the culture tank 112 is not necessarily limited, but may contain, for example, 20 liters to 1,000,000 liters of solution, preferably 100 liters to 10,000 liters. Alternatively, the culture tank 112 may be a large water tank, for example, a 50,000 kiloliter tank. In such a case, a plurality of fine bubble supply means 130 and detector 240, which will be described later, may be installed in the culture tank 112.

[0026] In the algae cultivation system 100 of the present invention, the algae fixing means 120 is immersed in the cultivation water area 110 and is disposed on the bottom surface 125 of the cultivation tank 112. The algae fixing means 120 is used to fix the algae 126 in a predetermined position within the cultivation water area 110.

[0027] The algae fixing means 120 has the form of a block and is made of a material with a specific gravity greater than that of the culture solution contained in the culture water area 110. This is to ensure that the algae 126 remains on the bottom surface 125 that has been placed in advance during growth, and does not easily float up or move within the culture water area 110.

[0028] Materials that can be used to form the algae fixing means 120 include, but are not limited to, metal (e.g., corrosion-resistant stainless steel), resin (e.g., polystyrene), concrete, brick, and combinations thereof. Concrete and / or brick are preferred because they are less susceptible to corrosion by seawater, etc.

[0029] The algae fixing means 120 is provided with, for example, holes of a predetermined size (not shown), and juvenile algae (microalgae) can be grown in these holes. Note that Fig. 1 shows a state in which one algae 126 has grown and grown on one algae fixing means 120, but the present invention is not limited to this. For example, multiple algae 126 may grow on one algae fixing means 120.

[0030] Furthermore, the algae fixing means 120 shown in FIG. 1 are preferably arranged on the bottom surface 125 of the culture tank 112 at predetermined intervals to prevent uneven concentration of the algae 126.

[0031] In the algae culture system 100 shown in Figure 1, the algae fixation means 120 can be manually moved while the algae 126 are growing. For example, when the algae culture system 100 shown in Figure 1 is used to grow the algae 126 using multiple algae fixation means 120, even if differences in the growth state of the algae 126 occur due to reasons such as incident light or uneven distribution of fine bubbles 132 (described below), a person skilled in the art can appropriately change the position of the algae fixation means 120. This makes it possible to freely change the position of the algae 126 growing in the culture water area 110, even after the algae 126 have grown on the algae fixation means 120.

[0032] In the present invention, when a plurality of algae fixing means 120 are used, the algae 126 fixed to each algae fixing means 120 may be the same or different from each other.

[0033] The algae 126 may grow in freshwater, brackish water, or seawater. The culture solution constituting the culture water area 110 can be selected according to the type of algae 126 being grown. In the present invention, the algae 126 is preferably a macroalgae that can grow in seawater because it allows for larger-scale cultivation and a wide variety of types. Such macroalgae also have the advantage of a high CO2 fixation rate.

[0034] Examples of the algae 126 belonging to the macroalgae include those belonging to the green algae, brown algae, and red algae.

[0035] Furthermore, examples of algae 126 belonging to macroalgae include, but are not limited to, Sargassum horneri (Turner) C., Ecklonia cava ssp. kurome, and Eisenia bicyclis (Kjellman) Setchell, as well as combinations thereof.

[0036] In the algae cultivation system 100 of the present invention, the fine bubble supply means 130 is immersed in the cultivation water area 110 and can supply gas components composed of fine bubbles 132 into the cultivation water area 110. The fine bubble supply means 130 is connected to a separate water circulation mechanism (not shown) and allows the culture solution in the cultivation water area 110 to pass through it.

[0037] The term "fine bubbles" as used herein refers to bubbles with a diameter of less than 100 μm, and includes both microbubbles (diameters of 1 μm or more and less than 100 μm) and ultrafine bubbles (diameters of less than 1 μm). Depending on their diameter, fine bubbles can rise very slowly in water and shrink and disappear as they dissolve, while others maintain their shape for weeks to months without rising or dissolving unless stimulated. In the present invention, fine bubbles include both of these.

[0038] The diameter of the fine bubbles 132 that can be supplied from the fine bubble supply means 130 is not particularly limited, but is preferably 0.1 μm to 100 μm, and more preferably 0.1 μm to 30 μm. If the diameter of the fine bubbles supplied from the fine bubble supply means 130 is less than 0.1 μm, a complex device may be required to form finer bubbles. If the diameter of the fine bubbles supplied from the fine bubble supply means 130 is more than 30 μm, the bubbles will quickly rise to the surface or shrink, and will only remain in the culture water area 110 for a short time, making it difficult to supply the fine bubbles effectively to the algae 126.

[0039] In the present invention, the fine bubble supply means 130 generates fine bubbles 132 containing carbon dioxide at a concentration of 2.1% by volume or more (i.e., 2.1% by volume or more and 100% by volume or less), preferably 2.5% by volume or more and 99% by volume or less, and more preferably 4% by volume or more and 10% by volume or less. If the concentration of carbon dioxide contained in the fine bubbles generated from the fine bubble supply means 130 falls below 2.1% by volume, the concentration of dissolved carbon dioxide tends to decrease, making it impossible to supply a high concentration of carbon dioxide to the algae 126, and it may become difficult to promote effective growth of the algae 126.

[0040] Fine bubbles with such a carbon dioxide concentration are made from, for example, artificially produced air (artificial air). For example, as shown in Fig. 1, fine bubbles 132 are prepared by mixing a predetermined concentration of carbon dioxide gas in a cylinder 134 with separately introduced air in a mixer 135 to prepare artificial air, and the artificial air is supplied to fine bubble supply means 130 through pipe 138 by adjusting valve 136.

[0041] Any fine bubble generator known in the art can be used for the fine bubble supply means 130. Examples of fine bubble generators include those that break down bubbles through a sudden pressure change in the gas-liquid flow path (e.g., Venturi or ejector fine bubble generators), those that break down bubbles through a high-speed liquid swirling flow (e.g., loop flow or swirling flow liquid fine bubble generators), those that miniaturize bubbles by passing them through micropores (e.g., micropore fine bubble generators), and those that precipitate bubbles by a sudden decompression of a pressurized gas-saturated solution (e.g., pressure-dissolved substrate precipitation fine bubble generators). In the present invention, the fine bubble supply means 130 is preferably a Venturi fine bubble generator, an ejector fine bubble generator, or a loop flow fine bubble generator, because their simple structure allows for easy maintenance and allows them to be installed in conjunction with offshore power generation facilities.

[0042] For example, a Venturi-type fine bubble generator introduces a liquid (culture medium) from an intake port into a first lumen that rapidly narrows in diameter and adjusts it to high pressure, then passes it through a second lumen located downstream that is designed to maintain approximately the same diameter under low pressure, while a gas (e.g., carbon dioxide or artificial air containing carbon dioxide) is sucked in and introduced from a separate tube. Then, pressure is applied again to the liquid and gas in a third lumen located further downstream that gradually widens in diameter, generating fine bubbles that can be discharged from an exhaust port.

[0043] The structure of such a Venturi-type fine bubble generator is also known, and commercially available Venturi-type fine bubble generators can be used in the present invention as they are. Furthermore, those skilled in the art can easily use such Venturi-type fine bubble generators to generate fine bubbles of a desired diameter in a given liquid.

[0044] In the algae cultivation system 100 of the present invention, the fine bubble supply means 130 does not have to be continuously operated to generate the fine bubbles 132. In other words, the fine bubble supply means 130 may be set to supply the fine bubbles 132 to the cultivation water area 110 intermittently.

[0045] As described above, the fine bubbles 132 can exist in the liquid (the culture solution constituting the culture water area 110) for a predetermined period of time. Therefore, even if the fine bubbles 132 are not continuously supplied from the fine bubble supply means 130, the supply can be stopped as long as the carbon dioxide concentration in the culture water area 110 is within a predetermined concentration range. As a result, the energy costs associated with the continuous operation of the fine bubble supply means 130 can be reduced.

[0046] 1, one fine bubble supply means 130 is disposed in the culture water area 110, but this is not limiting. In the present invention, multiple fine bubble supply means 130 may be disposed in the culture water area 110. When multiple fine bubble supply means 130 are disposed in the culture water area 110, it is preferable that the fine bubble supply means 130 are disposed at predetermined intervals from each other so that the fine bubbles 132 can be present in a more uniform state in the culture water area 110.

[0047] The algae cultivation system 100 of the present invention can efficiently supply a predetermined concentration of carbon dioxide gas to the cultivation water area 110 in the form of fine bubbles 132. This increases the carbon dioxide gas concentration in the cultivation water area 110, creating an environment more suitable for the growth of the algae 126. As a result, the algae 126 can be grown more efficiently in the cultivation water area 110.

[0048] FIG. 2 is a schematic diagram of another example of the algae culture system of the present invention.

[0049] The algae cultivation system 200 shown in FIG. 2 includes a detector 240 immersed in the cultivation water body 110, which is a closed water body.

[0050] The detector 240 is a device capable of monitoring the carbon dioxide concentration in the culture water area 110, and examples thereof include a gas sensor such as a carbon dioxide sensor, a pH sensor, and a pH electrode. The detector 240 is electrically connected to a computer 250 located outside the culture water area 110, and can directly or indirectly measure the carbon dioxide concentration in the culture water area 110. Note that in the present invention, the detector 240 may monitor the total carbon concentration in the culture water area 110 instead of the carbon dioxide concentration in the culture water area 110.

[0051] In the algae cultivation system 200 shown in Figure 2, the computer 250 is also electrically connected to a valve 236 located midway through a pipe 238 provided in the fine bubble supply means 130. For example, when the valve 236 is closed, the valve 236 is opened based on a signal from the computer 250, and a predetermined concentration of carbon dioxide gas in a cylinder 134 is mixed with separately introduced air in a mixer 135 to prepare artificial air, which is then supplied to the fine bubble supply means 130 through the pipe 238 by adjusting the valve 136. Thereafter, when the detector 240 detects that the carbon dioxide gas concentration in the cultivation water area 110 exceeds a preset threshold, the valve 236 is closed via the computer 250, and the supply of carbon dioxide gas (or artificial air containing carbon dioxide gas) from the pipe 238 to the fine bubble supply means 130 is stopped. As a result, the generation of fine bubbles 132 discharged from the fine bubble supply means 130 toward the cultivation water area 110 also stops.

[0052] FIG. 3 is a schematic diagram of another example of the algae culture system of the present invention.

[0053] In the algae cultivation system 300 shown in FIG. 3, an algae fixing means 320 is immersed in the cultivation water area 110, which is a closed water area, and is disposed at a distance from the bottom surface 125 of the cultivation tank 112 via two support stands 322, 324.

[0054] In the algae cultivation system 100 of the present invention, the algae fixing means 320 is a twisted string (e.g., rope). A plurality of algae 126 are fixed to the algae fixing means 320. The twisted string is generally used in algae cultivation, and is used, for example, by wrapping a seed thread on which algae larvae (microalgae bodies) have grown around it, or by sandwiching algae larvae between the twists of the twisted string itself.

[0055] The algae fixing means 320 may be fixed at both ends to, for example, two supports 322, 324 arranged on the bottom surface 125. Alternatively, the algae fixing means 320 may be fixed at both ends to ropes that are respectively suspended from two floats that float on the water (not shown).

[0056] The length of the algae fixing means 320 in the form of a twisted string shown in Figure 3 is not particularly limited, as it varies depending on factors such as the size of the culture tank 112. A specific length of the algae fixing means 320 in the form of a twisted string is, for example, 0.5 m to 100 m, and preferably 5 m to 30 m.

[0057] In the present invention, a plurality of algae 126 are fixed to one algae fixing means 320. To enable more uniform cultivation, it is preferable that the distance between one fixed algae 126 and its adjacent algae 126 is approximately constant. The type of algae 126 fixed to one algae fixing means 320 is not particularly limited. One type of algae 126 may be fixed to one algae fixing means 320, or two or more types of algae 126 may be mixed and fixed to one algae fixing means 320.

[0058] FIG. 4 is a schematic diagram showing yet another example of the algae cultivation system of the present invention.

[0059] 4, an algae culture system 400 is immersed in an open water culture area 410. This algae culture system 400 is similar to that shown in FIG.

[0060] As used herein, the term "open water" includes oceans, lakes (natural or artificial), and refers to water bodies in an environment that is not surrounded by a culture tank 112, such as that shown in Figure 1. The algae culture system of the present invention can also function effectively in such open waters.

[0061] 4, in order to prevent the fine bubbles 132 generated from the fine bubble supply means 130 from dispersing over time in the culture water area 410 and decreasing the carbon dioxide concentration around the algae 126, the fine bubble supply means 130 is preferably placed near the algae fixing means 320 or the algae 126. Furthermore, the detector 240 that measures the carbon dioxide concentration in the culture water area 410 is preferably placed near the algae fixing means 320 or the algae 126 in order to more accurately detect the carbon dioxide concentration around the algae 126.

[0062] In the embodiment shown in FIG. 4, the support bases 322, 324 for fixing both ends of the algae fixing means 320 may be placed directly on the bottom surface 425 of the culture water area 410 (for example, the bottom of a sea or lake).

[0063] FIG. 5 is a schematic diagram of yet another example of the algae cultivation system of the present invention.

[0064] In the algae cultivation system 500 shown in Figure 5, two algae fixing means 120, 320 are immersed in the open water cultivation water area 410. The algae fixing means 120 is the same as that shown in Figure 1. The algae fixing means 320 is the same as that shown in Figure 3.

[0065] In the algae cultivation system 500 shown in FIG. 5, by immersing these two types of algae fixing means 120, 320 in the cultivation water area 410, the growth density of the algae 126 in the height (depth) direction of the cultivation water area 410 can be increased.

[0066] 5, in order to prevent the fine bubbles 132 generated from the fine bubble supply means 130 from dispersing over time in the culture water area 410 and decreasing the carbon dioxide concentration around the algae 126, the fine bubble supply means 130 is preferably placed near the algae fixation means 120, 320 or the algae 126 growing on each algae fixation means 120, 320. Furthermore, the detector 240 that measures the carbon dioxide concentration in the culture water area 410 is preferably placed near the algae fixation means 120, 320 or the algae 126 growing on each algae fixation means 120, 320 in order to more accurately detect the carbon dioxide concentration around the algae 126.

[0067] In the embodiment shown in Figure 5, the algae fixing means 120, which has the form of a block, and the support bases 322, 324 that fix both ends of the algae fixing means 320 may both be placed directly on the bottom surface 425 (e.g., the bottom of a sea or lake) in the culture water area 410.

[0068] The algae cultivation system of the present invention uses a fine bubble supply means immersed in the cultivation water area to supply carbon dioxide to the culture solution in the cultivation water area at a higher concentration than in a general cultivation water area (which has not undergone any particular treatment), thereby creating an aquatic environment more suitable for algae growth.

[0069] Furthermore, because the algae cultivation system of the present invention can supply carbon dioxide gas contained in fine bubbles to the cultivation water area, carbon dioxide gas can be present in the cultivation water area for a longer period of time than when carbon dioxide gas is supplied through conventional bubbling. As a result, the total amount of carbon dioxide gas required for algae cultivation can be reduced, i.e., it is possible to prevent unnecessary CO2 supply and its release back into the atmosphere, and it is also possible to reduce the amount of energy required for its supply. [Example]

[0070] The present invention will be described in detail below with reference to examples, although the present invention is not limited to these examples.

[0071] (Example 1: Cultivation using larvae of Akamoku) The following macroalgae were cultured using the algae culture system 100 shown in FIG.

[0072] 20 L of artificial seawater (Marine Art SF-1, manufactured by Osaka Yaken Co., Ltd.) was placed in a resin culture tank with internal dimensions of 38 cm length x 26 cm width x 24 cm depth, and a PESI-enriched seawater medium solution (pH 7.8) prepared using the components shown in Table 1 below was added to a concentration of 2 to 10 mL per 1 L of artificial seawater to prepare a culture medium.

[0073] [Table 1]

[0074] During the test period, one-third of the volume of this culture medium was replaced every 10 days.

[0075] Meanwhile, juvenile cups (approximately 200 μm in size) of Akamoku (Sargassum horneri (Turner) C.) (provided by the Kyoto Prefectural Agriculture, Forestry and Fisheries Technology Center, Marine Research Center, Miyazu City) were inoculated onto 15 mm square polystyrene blocks (hereafter referred to as PS blocks), and 60 of these PS blocks were placed at the bottom of the above-mentioned culture tank (in artificial seawater). Culture was continued with only the artificial seawater replaced every 6 to 17 days or with only air supplied until the juveniles grew to a size of a few centimeters.

[0076] Figure 6 shows a photograph of Akamoku juveniles that had grown on the PS blocks on the 11th day of cultivation. As shown in Figure 6, it was confirmed that on the 11th day of cultivation, Akamoku juveniles had grown to a size of 15 mm on the PS blocks.

[0077] (Example 2: Cultivation using larvae of Akamoku) The following macroalgae were cultured using the algae culture system 100 shown in FIG.

[0078] 20 L of culture solution prepared in the same manner as in Example 1 was placed in a resin culture tank with internal dimensions of 38 cm length x 26 cm width x 24 cm depth, and juvenile Sargassum horneri, each measuring approximately 3 cm, was sandwiched between twisted strings at intervals of approximately 6 cm (day 0 of culture; (a) of Figure 7).

[0079] Next, a loop-flow fine bubble generator (manufactured by OK Engineering Co., Ltd.) was immersed in the culture tank and operated for 15 minutes each in the morning (8:00 AM), midday (12:00 PM), and evening (4:00 PM). Fine bubbles (diameter 35 μm or less) composed of artificial air containing 4% carbon dioxide by volume were supplied to the artificial seawater, and the cultivation of Akamoku was continued for 48 days.

[0080] During this culture period, a pH sensor (HORIBA Ltd. 96805-10D), a carbon dioxide sensor (DKK Toa ELX-008), an oxygen sensor (Tokyo Rikakikai DO-2A), and a carbonate ion-selective electrode (DKK Toa ELX-008) were installed in the culture tank to measure the pH, carbon dioxide, oxygen, and carbonate ion concentrations of the artificial seawater in the culture tank. pH was measured every morning (9:00 AM), carbon dioxide every morning (9:00 AM) and evening (4:00 PM), oxygen every morning (9:00 AM), and carbonate ion every morning (9:00 AM) and evening (4:00 PM). Note that oxygen concentration was measured only from day 19 to day 48 of culture.

[0081] The growth of Sargassum horneri in the culture tank was photographed on days 15 and 27 of cultivation. The results are shown in Figure 7(b) and (c), respectively.

[0082] Table 2 shows the average values of pH, carbon dioxide concentration, oxygen concentration, and carbonate ion concentration measured from the culture solution in the culture tank during this culture period (day 0 to day 48).

[0083] (Comparative Example 1: Cultivation using Akamoku larvae) Using the algae cultivation system of Example 1, Akamoku cultivation was carried out for 48 days in the same manner as in Example 1, except that air (without adjusting the carbon dioxide concentration) was introduced instead of artificial air containing carbon dioxide.

[0084] The growth of Sargassum horneri in the culture tank was photographed on days 0, 15, and 27 of cultivation. The results are shown in Figure 8 (a), (b), and (c), respectively.

[0085] Table 2 shows the average values of pH, carbon dioxide concentration, oxygen concentration, and carbonate ion concentration measured from the culture solution in the culture tank during this culture period (day 0 to day 48).

[0086] [Table 2]

[0087] As shown in Figure 7, the Sargassum horneri cultivated in Example 2 grew significantly from day 0 ((a) in Figure 7) to day 15 ((b) in Figure 7) and day 27 ((c) in Figure 7). In contrast, as shown in Figure 8, the Sargassum horneri cultivated in Comparative Example 1 did not show much change in growth from day 0 ((a) in Figure 8) to day 15 ((b) in Figure 8) and day 27 ((c) in Figure 8).

[0088] Furthermore, as shown in Table 2, the average carbon dioxide gas value in the culture solution contained in the culture tank of Example 2 was approximately three times higher in the aggregated results of measurements taken at 9:00 AM than in the culture solution in the culture tank of Comparative Example 1, indicating that the culture solution contained abundant carbon dioxide gas. In contrast, no significant differences were observed between the culture solutions of Example 2 and Comparative Example 1 in terms of the average pH value or the average oxygen gas concentration.

[0089] Taking these results together, it can be seen that the growth of Akamoku can be improved by increasing the carbon dioxide concentration contained in the culture solution in the culture tank using the algae culture system of the present invention (Example 2).

[0090] (Example 3: Cultivation using larvae of Akamoku) The following macroalgae were cultured using the algae culture system 100 shown in FIG.

[0091] A culture medium was prepared by placing 100 L of artificial seawater (Marine Art SF-1, manufactured by Osaka Yaken Co., Ltd.) in a resin culture tank with internal dimensions of 44 cm length x 89 cm width x 44 cm depth, and adding 2 to 10 mL of PESI-enriched seawater medium solution (pH 7.8) prepared using the ingredients shown in Table 1 above, per 1 L of artificial seawater. Note that one-third of the volume of this culture medium was replaced every 10 days during the test period.

[0092] On the other hand, three larval Akamoku plants, the initial mass of which had been measured in advance, were fixed to each twisted string, and two sets of twisted strings with the larvae fixed to them were prepared. These twisted strings were placed in the artificial seawater of the culture tank, and fine bubbles (diameter 35 μm or less) composed of artificial air containing 4% by volume of carbon dioxide were supplied to the artificial seawater, and Akamoku was continuously cultured for 60 days.

[0093] During the culture period, the mass of the larval Akamoku in each twisted string was measured at regular intervals. Furthermore, the average mass increase relative to the initial mass of each individual was calculated and plotted on a graph as the mass change (relative value). A least-squares approximation curve (y = 1.0155 + 0.05412x; R 2 = 0.98624) was obtained. The results are shown in Figure 9.

[0094] (Comparative Example 2: Cultivation using Akamoku larvae) The mass of the larval Sargassum horneri in each twisted cord was measured at predetermined intervals during the culture period in the same manner as in Example 3, except that air containing 4% by volume of carbon dioxide was supplied instead of artificial air. Furthermore, the average mass increase relative to the initial mass of each individual was calculated and plotted on a graph as the mass change (relative value). An approximate curve (y = 1.0582 + 0.044986x; R 2= 0.9907) was obtained. The results are shown in Figure 9.

[0095] As shown in Figure 9, the Akamoku of Example 3, which was supplied with fine bubbles of artificial air containing 4% by volume of carbon dioxide, grew with a larger slope than the Akamoku of Comparative Example 2, which was supplied with fine bubbles of air. Comparing the slope of the approximation curve obtained in Example 3 with the slope obtained in Comparative Example 2, there was a difference of 1.2 times (≒0.05412 / 0.044986). This shows that the Akamoku of Example 3 grew at a rate 1.2 times faster than the Akamoku of Comparative Example 2. [Explanation of symbols]

[0096] 100,200,300,400,500 Algae Cultivation System 110 Culture area (closed area) 112 Culture tank 120,320 Algae fixation means 125,425 bottom 126 Algae 130 Fine bubble supply means 132 Fine Bubbles 134 Cylinder 135 Mixer 136,236 valves 138,238 tubes 240 detector 250 computers 322,324 Support stand 410 Culture water area (open water area)

Claims

1. 1. An algae cultivation system comprising: A culture water area; an algae fixing means immersed in the culture water area; a fine bubble supply means immersed in the culture water area; Equipped with The algae cultivation system, wherein the fine bubble supplying means generates fine bubbles containing 2.1% by volume or more of carbon dioxide.

2. The algae culture system according to claim 1 , wherein the fine bubble supply means intermittently supplies the fine bubbles to the culture water area.

3. 2. The algae culture system according to claim 1, wherein the fine bubbles are composed of artificial air containing 2.1% by volume or more and 100% by volume or less of carbon dioxide.

4. The algae cultivation system of claim 1 , wherein the cultivation water area is an open water area.

5. The algae cultivation system according to claim 1 , wherein the cultivation water area is a closed water area.

6. The algae cultivation system of claim 1 , further comprising a detector for monitoring the carbon dioxide concentration contained in the cultivation water area.

7. 7. The algae culture system of claim 6, wherein the detector and the fine bubble supply means are electrically connected via a computer, and the computer generates fine bubbles from the fine bubble supply means in accordance with the carbon dioxide concentration detected by the detector.

8. A method for cultivating algae, comprising: A step of fixing algae to a fixing means constituting the algae culture system according to any one of claims 1 to 7; generating fine bubbles from a fine bubble supply means in the culture water area; A method comprising:

9. The method according to claim 8, further comprising the step of monitoring the carbon dioxide concentration in the culture water area and stopping the generation of fine bubbles from the fine bubble supply means when the carbon dioxide concentration exceeds a threshold value.

Images