V-shaped culture vessel

Abstract

In order to culture algae while suppressing the amount of energy that is input, the present invention provides a culture vessel for culturing algae, the culture vessel being characterized by having a structure in which the vertical cross section of the culture vessel is V-shaped and the horizontal cross section of the culture vessel is rectangular.

Description

V-shaped culture tank

[0001] The present invention relates to an algae culture tank, a culture device using the culture tank, and a method for culturing algae using the culture device.

[0002] Reusing carbon dioxide is becoming an urgent issue in building a sustainable human society. Fossil fuel reserves are limited, so it is also extremely important to build a new social system that relies on solar energy. Algae cultivation is expected to be a sustainable energy and food production technology using solar energy. However, there is a problem in that the amount of energy input for cultivation is too large compared to the amount of energy obtained from algae.

[0003] In algae cultivation, energy is generally consumed for 1) adjusting and managing the culture medium, 2) temperature control, 3) agitation, 4) aeration, 5) monitoring, 6) culture medium recovery, and 7) light. Of these, agitation and temperature control require large amounts of energy depending on the amount of culture medium, and since light is directly related to algae growth, the amount of energy used is directly linked to the yield.

[0004] Currently, mass cultivation of algae is primarily carried out in ponds (Non-Patent Document 1). Agitation in ponds is achieved using water pumps or water wheels, and the energy consumed during this process depends on the amount of culture solution (area x water depth). While there are ponds that do not require agitation, their cultivation efficiency is generally poor. The light source for ponds is sunlight, and the amount of light distributed to each alga depends on the pond's area / water depth. Based on this relationship, the only way to cultivate large quantities of algae is to increase the pond's area or water depth. However, both increase energy consumption, and increasing the water depth reduces the amount of light distributed to the point where it equals the yield. The relationship between the area, water depth, and each parameter is theoretical, and while some efficiency improvements are possible, fundamental changes are impossible as long as the pond is used.

[0005] Armin Hallmann, Current Biotechnology, 2015, 4, 389-415

[0006] As described above, algae cultivation is expected to be a sustainable energy and food production technology, but the large amount of energy input is a problem. The present invention was made against this background, and aims to provide a means for cultivating algae while reducing the amount of energy input.

[0007] As a result of extensive research to solve the above problems, the present inventors discovered that by culturing algae in a V-shaped culture tank, efficient culture is possible without agitation using a water pump or water wheel, and that algae can be cultured at a higher density than in a normal culture tank. Based on this finding, the present invention has been completed. Specifically, the present invention provides the following (1) to (5).

[0008] (1) A culture tank used for culturing algae, characterized in that the vertical cross section of the culture tank is V-shaped and the horizontal cross section of the culture tank is rectangular.

[0009] (2) The culture tank according to (1), wherein the V-shaped angle is 60 to 150 degrees.

[0010] (3) A culture apparatus comprising: the culture tank according to (1) or (2); a bubble-generating member installed at the bottom of the culture tank; a gas supply pipe communicating with the bubble-generating member; and a gas supply source communicating with the gas supply pipe.

[0011] (4) A method for cultivating algae, comprising cultivating algae using the culture device according to (3).

[0012] (5) The method for culturing algae according to (4), wherein the algae belong to the genus Nannochloropsis.

[0013] This specification includes part or all of the contents as disclosed in the specification and / or drawings of Japanese Patent Application No. 2024-117896, which is a priority document of the present application.

[0014] The present invention provides a novel algae culture tank. Use of the culture tank of the present invention enables efficient culture without the need for agitation using a water pump or water wheel, thereby reducing the amount of energy required for culture. Furthermore, use of the culture tank of the present invention enables algae to be cultured at higher densities than conventional culture tanks. Furthermore, by making the culture tank V-shaped, the volume relative to the surface area is reduced compared to conventional culture tanks (pond-type), and the amount of light distributed to each alga can also be increased.

[0015] Schematic top view (a), schematic front view (b), and schematic side view (c) of the fermenter of the present invention. Schematic diagram of the V-shaped fermenter used in the examples. Numbers in the figure represent dimensions (mm). Schematic diagram of the conventional fermenter used in the examples. Numbers in the figure represent dimensions (mm). Graph showing the transition of cell number when using each fermenter test machine. Graph showing the amount of power consumption when using each fermenter test machine.

[0016] The present invention will be described in detail below. The culture tank of the present invention is a culture tank used for culturing algae, and is characterized by having a structure in which the vertical cross section of the culture tank is V-shaped and the horizontal cross section of the culture tank is rectangular.

[0017] The angle of the V shape is not particularly limited, but is preferably 60 to 150 degrees, and more preferably 80 to 130 degrees. Note that the "V shape angle" refers to the smaller angle (an angle less than 180 degrees) between the two straight lines that make up the V shape. The aspect ratio of the rectangle is also not particularly limited, and the length and width may be equal (i.e., it may be a square).

[0018] The material of the culture tank is not particularly limited, but it must be strong enough to hold the culture tank and culture solution in a V-shape. For example, it can be made from polypropylene resin or concrete. The size of the culture tank is not particularly limited. The culture tank is made of multiple planar members. The culture tank may be made by gluing these planar members together or by integral molding.

[0019] The culture apparatus of the present invention is characterized by comprising the above-mentioned culture tank of the present invention, a bubble-generating member installed at the bottom of the culture tank, a gas supply pipe communicating with the bubble-generating member, and a gas supply source communicating with the gas supply pipe.

[0020] The bubble-generating member may be any member capable of generating bubbles in the culture solution in the culture tank. For example, as shown in the examples, an air tube with fine holes may be used, or a commercially available air stone may be used. The bubble-generating member is installed at the bottom of the culture tank, preferably at the very bottom (the lowest part of the V-shaped depression). By installing the bubble-generating member in such a position, the culture solution can be stirred vertically and horizontally, as described below.

[0021] The gas supply pipe may be any type that can supply gas from a gas supply source to the bubble generating member, for example, a commercially available air tube, etc. The gas supply source may be any type that can supply gas to the culture solution in the culture tank via the gas supply pipe, for example, a commercially available air pump, etc.

[0022] The method for cultivating algae of the present invention is characterized by cultivating algae using the above-described culture apparatus of the present invention.

[0023] The algae to be cultured are not particularly limited, but microalgae are preferred, and algae belonging to the genus Nannochloropsis are particularly preferred. The culture medium used for the culture is also not particularly limited and can be selected appropriately depending on the type of algae to be cultured. The culture is usually carried out under natural light, but may also be carried out under artificial light, or under both natural and artificial light.

[0024] An example of a culture tank of the present invention will be described below with reference to Fig. 1. Fig. 1a is a view of the culture tank from above, Fig. 1b is a view of the culture tank from the front, and Fig. 1c is a view of the culture tank from the side. Fig. 1a shows a culture tank 1 and a culture solution 5 in addition to the culture tank 1, Fig. 1b shows a bubble-generating member 2 and the culture solution 5 in addition to the culture tank 1, and Fig. 1c shows a culture tank 1 and a bubble-generating member 2, a gas supply pipe 3, a gas supply source 4, and the culture solution 5 in addition to the culture tank 1.

[0025] The vertical cross section of this fermenter is V-shaped and the horizontal cross section is rectangular, so it appears V-shaped from the front (Figure 1b) and rectangular from the top (Figure 1a). Note that the cross section of the portion of the fermenter that comes into contact with the culture medium is sufficient, and the cross section of the entire fermenter does not necessarily have to be V-shaped or rectangular. For example, in the examples, an inclined resin box is used as the fermenter, but the vertical cross section of this fermenter is not V-shaped (Figure 2). However, if we limit the cross section to the portion of the fermenter that comes into contact with the culture medium, the vertical cross section becomes V-shaped (Figure 2).

[0026] The culture tank may be provided with other components in addition to the bubble generating member 2, the gas supply pipe 3, and the gas supply source 4. For example, the culture tank may be provided with legs to stabilize it.

[0027] When culturing algae using a culture tank, a culture solution 5 is placed in the culture tank 1, and typically, a bubble-generating element 2, a gas supply pipe 3, and a gas supply source 4 are installed (Figure 1c). Gas supplied from the gas supply source 4 reaches the bubble-generating element 2 via the gas supply pipe 3. Because the bubble-generating element 2 is installed at the very bottom of the culture tank 1, the gas that reaches the bubble-generating element 2 becomes bubbles and rises from there toward the opening of the culture tank 1. This rising gas agitates the culture solution 5 and algae vertically. Furthermore, because the gas is generated only near the center of the bottom of the culture tank, the culture solution and algae around the gas-generating element at the bottom are also agitated horizontally, as they are sucked into the bubble-generating element. Furthermore, the culture solution and algae that reach the opening due to the rising gas disperse horizontally along the water surface. The algae then fall vertically due to gravity, following the V-shaped slope until they reach the bubble-generating element and are agitated again. In addition, by varying the temperature of the culture solution at the top and bottom of the culture tank, it is possible to promote thermal convection due to thermal heterogeneity, thereby strengthening horizontal agitation. This temperature difference can be created naturally by sunlight raising the water surface in the culture tank relatively high, or it can be created artificially by adjusting the temperature of the gas being generated. In either case, vertical agitation by the gas promotes thermal convection within the culture tank. As a result, the culture solution 5 and algae are agitated horizontally by gas, gravity, and thermal convection.

[0028] Because this culture tank has a V-shaped structure, the volume of the culture solution relative to the area of ​​the top surface of the culture solution is reduced to half compared to conventional rectangular culture tanks, and as a result, the amount of light distributed to each algae body is doubled.This means that it is possible to produce algae bodies at a higher density in large culture tanks where light cannot be obtained from above the culture solution.

[0029] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0030] Experimental method 1. Preparation of fermenter test equipment (a) V-shaped fermenter (1) The polypropylene resin box shown in Figure 2 was tilted 45 degrees and fixed in place. (2) A 200 mm length of air tubing with an outer diameter of 5 mm was cut out and connected to end cap (a) and L-shaped joint (b). (3) Using an insect pin, holes for bubbling were drilled at 10 mm intervals in the air tubing of (2). (4) (a) of (2) was fixed to one corner of the bottom of (1) and (b) to the other corner with adhesive. (5) An air tubing connected to an air pump (1.4 W) was connected to (b).

[0031] (a) Conventional culture tank (1) A 200 mm length of air tubing with an outer diameter of 5 mm was cut out, and an end cap (a) and an L-shaped joint (b) were connected. (2) Bubbling holes were drilled at 10 mm intervals in the air tubing using an insect pin. (3) (a) and (b) of (2) were fixed with adhesive to the corners of the bottom of the polypropylene cylindrical box shown in Figure 3. (4) An air tubing connected to an air pump (1.4 W) was connected to (b). (5) A submersible pump (3 W) was installed directly in front of the air tubing of (3).

[0032] 2. Culture medium and pre-culture (a) Add approximately 1 x 10 Nannochloropsis culture solution to 2.5 L of the medium with the composition shown in Table 1. 6 (a) The diluted Nannochloropsis culture solution was cultured indoors near a window with bubbling. (c) The room temperature was maintained at 25°C by an air conditioner, and natural light coming through the window was 500 μmol photons / m at its strongest during the day. 2The temperature was s. Bubbling was performed using an air pump (1.4W). (d) The cultured solution was used as the preculture solution for this experiment after 3 weeks of culture.

[0033] 3. Test culture and sampling (a) The culture tank shown in 1 was placed near a window in the room, and approximately 2.5 L of medium (Table 1) was poured into it so that the water depth was 100 mm. (b) The pre-culture solution shown in 2 was poured into it so that the cell concentration was 1 x 10 6 The cells were added to the cells at a concentration of 1000 cells / ml and cultured for 3 weeks. (c) The room temperature was maintained at 25°C by an air conditioner, and natural light coming through the window was 500 μmol photons / m at its strongest during the day. 2 -s. Bubbling was performed using an air pump. Conventional culture tanks were also stirred using a submersible pump. (d) Water (tap water) was added approximately every two days to prevent a decrease in liquid volume due to evaporation and an increase in salt concentration. (e) To check the growth progress, about 1 ml of culture liquid was collected on the 7th, 13th, 17th, and 20th days, and the number of cells was counted. Sampling was performed using a spatula, and the culture liquid was stirred well before collection.

[0034] Experimental Results 1. Transition of cell number Figure 4 shows the transition of cell number when using each test fermentor. As shown in the figure, the V-shaped fermentor showed almost the same cell growth as the conventional fermentor, even though the culture medium was not stirred by a submersible pump. Furthermore, while cell growth in the conventional fermentor almost stopped on the 13th day, in the V-shaped fermentor, cells continued to grow even after the 13th day.

[0035] 2. Power consumption The power consumption when using each test fermenter is shown in Figure 5. As shown in the figure, the power consumption of the V-shaped fermenter was about one-third of that of the conventional fermenter.

[0036] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

[0037] The present invention can be used in industrial fields related to algae.

[0038] DESCRIPTION OF SYMBOLS 1 Culture tank 2 Bubble generating member 3 Gas supply pipe 4 Gas supply source 5 Culture solution

Claims

1. A culture tank used for culturing algae, characterized in that the vertical cross section of the culture tank is V-shaped and the horizontal cross section of the culture tank is rectangular.

2. The culture tank according to claim 1, characterized in that the V-shaped angle is 60 to 150 degrees.

3. A culture device comprising the culture tank according to claim 1 or 2, a bubble generating member installed at the bottom of the culture tank, a gas supply pipe communicating with the bubble generating member, and a gas supply source communicating with the gas supply pipe.

4. A method for cultivating algae, comprising cultivating algae using the cultivating device according to claim 3.

5. The method for culturing algae according to claim 4, wherein the algae belong to the genus Nannochloropsis.

Images