Patent Publication Number: US-2023159884-A1

Title: Culture device and culture method

Description:
TECHNICAL FIELD 
     The present invention relates to a culture device and a culture method for culturing microalgae in a culture solution. 
     BACKGROUND ART 
     Microalgae are cultured by supplying light and carbon dioxide gas to the microalgae in a culture solution to thereby carry out photosynthesis. In order to efficiently culture the microalgae, it is essential to supply the light and the carbon dioxide evenly to the entirety of the microalgae in the culture solution to thereby promote photosynthesis. 
     Thus, for example, as disclosed in JP 2019-068773 A, a culture device is known in which microalgae are cultured while a culture solution is circulated inside a culturing tank. Such a culture device is equipped with a culturing tank for storing the culture solution, a main supply pipe arranged along a longitudinal direction of the culturing tank, and a water pump for delivering and circulating the culture solution inside the culture tank to the interior of the main supply pipe. A plurality of through holes are formed on a wall surface of the main supply pipe at a predetermined interval in an axial direction of the main supply pipe. Therefore, when the culture solution is delivered by the water pump to the interior of the main supply pipe, due to the culture solution flowing out from the through holes, a flow of the culture solution is formed which is capable of allowing the microalgae to circulate in the interior of the culturing tank. 
     SUMMARY OF THE INVENTION 
     However, in the aforementioned culture device, since it is necessary to drive the water pump in order to cause the culture solution to circulate, a concern arises in that energy consumption when culturing the microalgae may increase. In particular, for a case in which production of biofuels or the like is carried out using the cultured microalgae, from the standpoint of reducing production costs and realizing carbon neutrality, it is necessary to reduce the introduction energy as much as possible. 
     The present invention has been devised in order to solve the aforementioned problems, and has the object of providing a culture device and a culture method which are capable of satisfactorily culturing microalgae with a simple configuration while suppressing an increase in energy consumption. 
     One aspect of the present invention is characterized by a culture device that cultures microalgae in a culture solution, the culture device comprising a main body portion including an accommodation unit which is configured to accommodate the culture solution and the microalgae, and to which a gas is supplied, a joint member that is formed by joining together inner wall surfaces of the accommodation unit and extends in a direction in which the gas is supplied, a guide unit and a circulation unit that are disposed in an interior of the accommodation unit, are adjacent to each other with the joint member being interposed therebetween, and lie respectively along a direction in which the joint member extends, and a gas supply port configured to enable the gas to be supplied to the guide unit, wherein the gas is supplied to the guide unit from a lower side to an upper side when the main body portion is installed at an installation location, the guide unit and the circulation unit communicate with each other via a guide unit inlet port provided on an upstream side in the direction in which the gas is supplied, and a guide unit outlet port provided on a downstream side in the direction in which the gas is supplied, and when the gas flows through the guide unit, a culture solution flow is generated in which the culture solution inside the circulation unit flows into the guide unit from the guide unit inlet port, and the culture solution inside the guide unit flows out from the guide unit outlet port into the circulation unit. 
     Another aspect of the present invention is characterized by a culture method for culturing microalgae using the above-described culture device, the culture method comprising an installation step of installing, in the water storage unit in which the stored water is stored, the main body portion prior to the culture solution being accommodated in the accommodation unit, and an accommodation step of accommodating the culture solution in the accommodation unit, in a state in which the main body portion is installed in the water storage unit. 
     In such a culture device, a gas such as carbon dioxide which is required for culturing the microalgae is supplied from the gas supply port and made to flow through the guide unit, whereby the culture solution flow is capable of being generated inside the accommodation unit. Since the microalgae can be allowed to circulate due to the culture solution flow, gas and light can be effectively supplied to the entirety of the microalgae inside the accommodation unit, and photosynthesis can be promoted. 
     In addition, in the culture device, by joining the inner wall surfaces of the main body portion and thereby forming the joint member, it is possible to easily provide a configuration such as the guide unit and the circulation unit in order to generate the culture solution flow. Further, in the culture device, for example, it is not necessary to provide and drive a special configuration such as a water pump or the like in order to generate the culture solution flow. 
     From the above, according to the present invention, it is possible to satisfactorily culture the microalgae with a simple configuration while suppressing an increase in energy consumption. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic cross-sectional view of a main body portion of a culture device according to an embodiment of the present invention; 
         FIG.  2    is a cross-sectional view taken along line II-II of  FIG.  1   ; 
         FIG.  3    is a schematic perspective view of a water storage tank of the culture device according to the embodiment of the present invention; 
         FIG.  4 A  and  FIG.  4 B  are explanatory diagrams for describing an installation step of a culture method according to an embodiment of the present invention in which the culture device shown in  FIG.  1    and  FIG.  3    is used; 
         FIG.  5 A  and  FIG.  5 B  are explanatory diagrams for describing an accommodation step of the culture method shown in  FIG.  4 A  and  FIG.  4 B ; 
         FIG.  6    is a schematic cross-sectional view of a main body portion according to an exemplary modification; 
         FIG.  7    is a cross-sectional view taken along line VII-VII of  FIG.  6   ; 
         FIG.  8    is a schematic cross-sectional view of a main body portion according to another exemplary modification; and 
         FIG.  9    is a cross-sectional view taken along line IX-IX of  FIG.  8   . 
     
    
    
     DESCRIPTION OF THE INVENTION 
     A preferred embodiment concerning a culture device and a culture method according to the present invention will be presented and described in detail below with reference to the accompanying drawings. Moreover, in the drawings described below, constituent elements having the same or similar functions and effects are designated by the same reference numerals, and repeated description thereof may be omitted. 
     A culture device  10  according to the present embodiment shown in  FIGS.  1  to  3    cultures microalgae by supplying light and a gas such as a carbon dioxide gas or a carbon dioxide-containing gas to microalgae (not shown) in a culture solution containing water, so that the microalgae proliferate while carrying out photosynthesis. Although the microalgae that are capable of being cultured by the culture device  10  are not particularly limited, for example, in the case of producing a biofuel such as ethanol using the cultured microalgae, microalgae which are classified as Chlorophyceae (e.g.,  Chlamydomonas, chlorella ), Prasinophytes, Cryptophytes, and Cyanobacteria (e.g.,  Spirulina ) are preferred. In addition to water, the culture solution may contain nutrients and the like necessary for culturing the microalgae. The gas preferably contains a carbon dioxide gas discharged from a factory or the like. 
     As an environment that can be irradiated with light having a wavelength (for example, 400 to 700 nm) required for growth of the microalgae, for example, the culture device  10  is installed outdoors where it can be irradiated with sunlight. Moreover, the culture device  10  may be installed in a room or the like where it can be irradiated with sunlight or artificial light. Further, the culture device  10  includes a main body portion  12  as shown in  FIG.  1    and  FIG.  2   , and a water storage tank  14  as shown in  FIG.  3   . The main body portion  12  is formed, for example, from a material that is flexible and transmits light, such as linear low density polyethylene (LLDPE). It should be noted that the term “material that transmits light” implies that such a material can transmit light having a wavelength required for growth of the microalgae. In the present embodiment, the main body portion  12  is formed in a hollow shape (a bag shape) by superimposing two sheets made up from the aforementioned material; however, the present invention is not particularly limited to this feature. 
     In the embodiment shown in  FIG.  1    and  FIG.  2   , the main body portion  12  includes, one each respectively, of an accommodation unit  16 , a joint member  18 , a guide unit  20 , a circulation unit  22 , a facing portion  24 , a gas supply port  26 , a culture solution supply port  28 , a gas discharge port  30 , and a collection port  32 . 
     The accommodation unit  16  is disposed in the interior of the hollow shaped main body portion  12 , and the culture solution and the microalgae are accommodated as contents M therein. Further, the gas is supplied to the accommodation unit  16  via the gas supply port  26  which is connected to a non-illustrated gas supply mechanism. According to the present embodiment, the accommodation unit  16  is surrounded by an enclosure  34  which is formed by joining together the inner wall surfaces of the main body portion  12  by means of welding or the like, along an outer peripheral edge portion of the main body portion  12 . In other words, the culture device  10  is a so-called closed system in which the microalgae are cultured in the culture solution that is accommodated in the interior of the sealed accommodation unit  16 . 
     Further, as will be described later, when the main body portion  12  is installed in a water storage unit  36  (an installation location) of the water storage tank  14  shown in  FIG.  5 A  and  FIG.  5 B , the gas is supplied to the interior of the accommodation unit  16  from a lower side (the side of the arrow X1) toward an upper side (the side of the arrow X2) in the vertical direction. Each of the main body portion  12  and the accommodation unit  16  is formed in a rectangular shape, with the direction in which the gas is supplied (the vertical direction) being the long side and the horizontal direction being the short side as viewed from the front. 
     The joint member  18  is formed by joining together the inner wall surfaces of the accommodation unit  16  (the main body portion  12 ) by welding or the like, and extends in the direction (the vertical direction, the direction of the arrows X1 and X2) in which the gas is supplied. The length of the joint member  18  in the direction in which the joint member extends is set to be shorter than the length of the accommodation unit  16  in the vertical direction. One end part  18   a  and another end part  18   b  of the joint member  18  in the direction in which the joint member extends are each formed in an arcuate shape. 
     In the interior of the accommodation unit  16 , the guide unit  20  and the circulation unit  22  are adjacent to each other with the joint member  18  being interposed therebetween, and are arranged respectively along the direction in which the joint member  18  extends. In other words, the guide unit  20  and the circulation unit  22  are adjacent to each other with the joint member  18  being interposed in a short-side direction (the direction of the arrows Y1 and Y2) of the accommodation unit  16 . When the contents M are accommodated in the accommodation unit  16 , as shown in  FIG.  2   , each of the guide unit  20  and the circulation unit  22  has a substantially cylindrical shape as viewed in the vertical direction. According to the present embodiment, the respective inner diameters of the guide unit  20  and the circulation unit  22  as viewed in the vertical direction are substantially the same; however, the present invention is not particularly limited to this feature. 
     As shown in  FIG.  1   , the guide unit  20  and the circulation unit  22  communicate with each other via a guide unit inlet port  38  provided on an upstream side (the side of the arrow X1) in the direction in which the gas is supplied, and a guide unit outlet port  40  provided on a downstream side (the side of the arrow X2) in the direction in which the gas is supplied. Hereinafter, the upstream side in the direction in which the gas is supplied may also be simply referred to as an “upstream side”, and the downstream side in the direction in which the gas is supplied may also be simply referred to as a “downstream side”. In the present embodiment, the upstream side is a lower side in the vertical direction. Further, the downstream side is an upper side in the vertical direction. 
     As noted previously, by the length of the joint member  18  in the direction of extension thereof being shorter than the length of the accommodation unit  16  in the vertical direction, the guide unit inlet port  38  is disposed between the one end part  18   a  (the end part on the side of the arrow X1) of the joint member  18  in the direction of extension thereof, and the enclosure  34 . Further, the guide unit outlet port  40  is disposed between the other end part  18   b  (the end part on the side of the arrow X2) of the joint member  18  in the direction of extension thereof, and the enclosure  34 . 
     The facing portion  24  is formed by joining together the inner wall surfaces of the main body portion  12  by welding or the like, and faces toward the guide unit  20  at a location above the other end part  18   b  of the joint member  18 . The facing portion  24  extends along a direction (the direction of the arrows Y1 and Y2 in the present embodiment) that intersects with the direction in which the gas is supplied. Both ends of the facing portion  24  in the direction of extension thereof are preferably formed in an arcuate shape. 
     The gas supply port  26  is disposed below the guide unit  20 , and is capable of supplying the gas from the gas supply mechanism toward the guide unit  20 . In this manner, by supplying the gas via the gas supply port  26 , the gas can be made to flow through the guide unit  20  in the direction (the vertical direction) in which the gas is supplied. When the gas flows through the guide unit  20  in this manner, a culture solution flow F 1  is generated in which the culture solution (the contents M) inside the circulation unit  22  flows into the guide unit  20  from the guide unit inlet port  38 , and the culture solution inside the guide unit  20  flows out from the guide unit outlet port  40  into the circulation unit  22 . 
     The culture solution supply port  28  is disposed, for example, on an upper end side of the main body portion  12 . Further, the culture solution supply port  28  is connected to a non-illustrated culture solution supply mechanism, and is capable of supplying the culture solution to the interior of the accommodation unit  16 . Moreover, the microalgae may be supplied together with the culture solution to the interior of the accommodation unit  16  via the culture solution supply port  28 . 
     The gas discharge port  30  is disposed on the upper end side of the main body portion  12 , and is capable of discharging the gas in the interior of the accommodation unit  16 . As gases that exist in the interior of the accommodation unit  16 , there may be cited a residual gas that has not been consumed by photosynthesis of the microalgae, oxygen gas that is generated by photosynthesis, and the like, from among the gases supplied from the gas supply port  26 . 
     The collection port  32  is disposed, for example, on a lower end side of the main body portion  12 , and is capable of collecting the contents M in the accommodation unit  16 . The culture solution supply port  28  and the collection port  32  are provided so as to be capable of opening and closing, and can be closed except when the culture solution is supplied to and discharged from the accommodation unit  16 . 
     Above the accommodation unit  16  in the main body portion  12 , a fixing member  42  that is isolated from the interior of the accommodation unit  16  is provided. The fixing member  42  is provided with through holes  44  through which non-illustrated support members or the like are inserted when the main body portion  12  is installed in the water storage unit  36  of the water storage tank  14  as shown in  FIG.  5 A  and  FIG.  5 B . 
     Similar to the main body portion  12 , the water storage tank  14  shown in  FIG.  3    is formed, for example, from a material that is flexible and transmits light, such as linear low density polyethylene (LLDPE). Moreover, the water storage tank  14  may be formed from a material that transmits light, such as acrylic resin, polycarbonate resin, or glass. The water storage tank  14  includes the water storage unit  36  in which stored water W is stored. The stored water W is a liquid that transmits light, such as water. The water storage unit  36  is set to be larger than the external dimensions of the main body portion  12 , and as shown in  FIG.  5 A  and  FIG.  5 B , the main body portion  12  is capable of being installed in the interior of the water storage unit  36 . Moreover, although the water storage tank  14  having a casing shape is shown in  FIGS.  3  to  5 B , the water storage tank  14  may have various shapes in which the water storage unit  36  can be formed, and may have a bag shape, for example. 
     The culture device  10  is basically configured in the manner described above. Next, a description will be given with reference to  FIGS.  1  to  5 B  concerning a culture method according to the present embodiment in which the culture device  10  is used. In such a culture method, first, as shown in  FIG.  3   , the stored water W is stored in the water storage unit  36  of the water storage tank  14 . Then, as shown in  FIG.  4 A  and  FIG.  4 B , an installation step is performed in which the main body portion  12 , prior to the contents M being accommodated in the accommodation unit  16 , is installed in the interior of the water storage unit  36 . Next, as shown in  FIG.  5 A  and  FIG.  5 B , in a state in which the main body portion  12  is installed in the water storage unit  36 , an accommodation step is performed in which the contents M are accommodated in the accommodation unit  16  from the culture solution supply mechanism via the culture solution supply port  28 . 
     Next, a gas supplying step is performed in which the gas from the gas supply mechanism is supplied to the guide unit  20  of the accommodation unit  16  via the gas supply port  26 . As a result, the culture solution flow F 1  can be generated inside the accommodation unit  16 , whereby the gas can be supplied to the entirety of the microalgae while allowing the microalgae to circulate. Further, since each of the water storage tank  14 , the stored water W, and the main body portion  12  transmits light, it is possible for the microalgae inside the accommodation unit  16  to be irradiated with light from various directions. As a result, inside the accommodation unit  16 , the microalgae proliferate while carrying out photosynthesis. 
     After the microalgae have been sufficiently proliferated inside the accommodation unit  16  by culturing the microalgae in the manner mentioned above, a collection step is performed in which the contents M are collected from the interior of the accommodation unit  16  via the collection port  32 . By separating the contents M into the microalgae and the culture solution, the microalgae can be obtained. 
     From the above, in the culture device  10  according to the present embodiment and the culture method according to the present embodiment in which the culture device  10  is used, the gas which is required for culturing the microalgae is supplied from the gas supply port  26  and is made to flow through the guide unit  20 , whereby the culture solution flow F 1  can be generated inside the accommodation unit  16 . Since the microalgae can be allowed to circulate due to the culture solution flow F 1 , gas and light can be effectively supplied to the entirety of the microalgae inside the accommodation unit  16 , and photosynthesis can be promoted. 
     In addition, in the culture device  10 , by means of a simple configuration in which the joint member  18  is formed by joining together the inner wall surfaces of the main body portion  12 , it is possible to provide the guide unit  20 , the circulation unit  22 , or the like, and generate the culture solution flow F 1 . Further, in the culture device  10 , for example, it is not necessary to provide and drive a special configuration such as a water pump in order to generate the culture solution flow F 1 . 
     Therefore, according to the culture device  10  and the culture method, it is possible to satisfactorily culture the microalgae with a simple configuration while suppressing an increase in energy consumption. 
     In the culture device  10  according to the above-described embodiment, the one end part  18   a  and the other end part  18   b  of the joint member  18  in the direction of extension thereof have an arcuate shape. Further, both ends of the facing portion  24  also have an arcuate shape. In the case of such features, since it is possible to prevent the corners where concentration of stress is likely to occur from being formed at the joint member  18  and the facing portion  24 , damage to the main body portion  12  due to hydraulic pressure of the culture solution or the like can be suppressed, and the durability of the culture device  10  can be increased. Moreover, the shape of the end parts of the joint member  18  and the facing portion  24  is not necessarily limited to an arcuate shape. 
     In the culture device  10  according to the above-described embodiment, the main body portion  12  is supplied with the gas from the lower side toward the upper side when the main body portion  12  is installed in the water storage unit  36  (the installation location) of the water storage tank  14 . In this case, due to the buoyancy of the gas bubbles within the culture solution, the gas can be raised from the lower side toward the upper side of the guide unit  20 . Therefore, the gas can be satisfactorily made to flow through the interior of the guide unit  20  without increasing the gas supply pressure, and the culture solution flow F 1  can be satisfactorily generated. Consequently, it is possible to reduce the energy consumption when culturing the microalgae. 
     The direction in which the gas is supplied is not limited to being from the lower side toward the upper side in the vertical direction, and for example, may be an inclined direction with respect to the vertical direction. Further, the direction in which the joint member  18  extends can also be set in accordance with the direction in which the gas is supplied. 
     The culture device  10  according to the above-described embodiment is provided with the water storage tank  14  including the water storage unit  36  in which the stored water W is stored, the main body portion  12  being capable of being installed in the water storage unit  36 . In this case, due to the stored water W, it becomes easy to maintain the temperature of the culture solution inside the accommodation unit  16  at a temperature that is suitable for culturing the microalgae. Therefore, it is possible to more satisfactorily culture the microalgae. It should be noted that the culture device  10  need not necessarily be equipped with the water storage tank  14 . 
     The culture method according to the above-described embodiment includes the installation step of installing, in the water storage unit  36  in which the stored water W is stored, the main body portion  12  prior to the culture solution being accommodated, and the accommodation step of accommodating the culture solution in the accommodation unit  16 , in a state in which the main body portion  12  is installed in the water storage unit  36 . In this case, the contents M (the culture solution) can be accommodated in the accommodation unit  16  in a state in which the main body portion  12  is subjected to the water pressure of the stored water W. Therefore, it is possible to prevent the main body portion  12  from becoming damaged due to the hydraulic pressure of the contents M inside the accommodation unit  16 . 
     The present invention is not particularly limited to the embodiment described above, and various modifications can be made to the invention without departing from the essence and gist thereof. 
     For example, instead of the main body portion  12  shown in  FIG.  1    and  FIG.  2   , the culture device  10  may be equipped with a main body portion  46  shown in  FIG.  6    and  FIG.  7   . The main body portion  46  shown in  FIG.  6    and  FIG.  7    mainly differs from the main body portion  12  shown in  FIG.  1    and  FIG.  2   , in that the guide unit  20  is disposed between inner side surfaces  18   c  of a pair of joint members  18  that face toward each other at an interval, and the circulation units  22  are formed respectively on the sides of outer side surfaces  18   d  of the pair of joint members  18 . 
     As shown in  FIG.  6   , in the accommodation unit  16 , the guide unit  20 , which extends in a long-side direction of the accommodation unit  16  (the direction of the arrows X1 and X2), is provided substantially in the center thereof in the short-side direction (the direction of the arrows Y1 and Y2). Along with this feature, the gas supply port  26  is provided substantially in the center in the short-side direction on the lower end side of the accommodation unit  16 . Further, the facing portion  24  is provided substantially in the center of the accommodation unit  16  in the short-side direction at a location above the other end parts  18   b  (the end part on the side of the arrow X2) of the joint members  18 . 
     The circulation units  22  that extend in the long-side direction are provided on both sides of the guide unit  20  in the short-side direction of the accommodation unit  16 . As shown in  FIG.  7   , in the main body portion  46 , when viewed in the vertical direction, the inner diameters of the circulation units  22  are substantially the same, and the inner diameter of the guide unit  20  is formed to be smaller than the inner diameters of the circulation units  22 . However, the relationship between the size of the inner diameter of the guide unit  20  and the size of the inner diameters of the circulation units  22  is not particularly limited. 
     A pair of inclined sections  50  are formed in the circulation units  22  on the side of the guide unit inlet ports  38  (the side of the arrow X1) by joining together the inner wall surfaces of the main body portion  46  by welding or the like. Each of the inclined sections  50  is inclined in a direction away from the guide unit  20  from the lower side (the side of the arrow X1) toward the upper side (the side of the arrow X2) when the main body portion  46  is installed at the installation location. According to the embodiment shown in  FIG.  6   , the lower end parts of the respective inclined sections  50  are arranged below the one end parts  18   a  of the joint members  18 . 
     In the main body portion  46 , sealing members  52  isolated from the accommodation unit  16  are formed by joining together the inner wall surfaces of the main body portion  46  by welding or the like. According to the embodiment shown in  FIG.  6   , the sealing members  52  are formed in a triangular shape surrounded by: the inclined sections  50 ; bottom side portions  54  that extend along the short-side direction of the accommodation unit  16  from lower end parts of the inclined sections  50  toward the sides away from the guide unit  20 ; and portions of the enclosure  34  that extend along the long-side direction. Since the sealing member  52  is isolated from the accommodation unit  16 , the inward flow of the contents M into the inner side of the triangular shape of the sealing member  52  is restricted. 
     Position fixing holes  56  are provided in the sealing members  52 . In the same manner as the through holes  44  provided in the fixing member  42 , the position fixing holes  56  enable support members or the like to be inserted therethrough when the main body portion  46  is installed in the water storage unit  36  of the water storage tank  14 . Moreover, the sealing members  52  may be formed in a manner so as to be isolated from the accommodation unit  16  by joining together the inner wall surfaces of the main body portion  46  by welding or the like. In other words, the sealing members  52  are not limited to being formed in a triangular shape surrounded by the inclined sections  50 , the bottom side portions  54 , and the portions of the enclosure  34 . 
     In the main body portion  46  as well, which is configured in the manner described above, by supplying the gas via the gas supply port  26 , the gas can be made to flow through the guide unit  20  in the direction (the vertical direction) in which the gas is supplied. When the gas flows through the guide unit  20 , a culture solution flow F 2  is generated in which the culture solution (the contents M) flows into the guide unit  20  via the guide unit inlet ports  38  from the circulation units  22  disposed on both sides in the short-side direction of the accommodation unit  16 , and the culture solution flows out from the guide unit  20  via the guide unit outlet port  40  into the circulation units  22  disposed on both sides in the short-side direction. 
     The culture method, in which the culture device  10  equipped with the main body portion  46  shown in  FIG.  6    and  FIG.  7    is used, can be carried out in a similar manner to the culture method, in which the culture device  10  equipped with the main body portion  12  shown in  FIG.  1    and  FIG.  2    is used. Accordingly, in the culture device  10  equipped with the main body portion  46  shown in  FIG.  6    and  FIG.  7    and the culture method in which the culture device  10  is used as well, it is possible to satisfactorily culture the microalgae with a simple configuration while suppressing an increase in energy consumption. 
     In addition, in the culture device  10  equipped with the main body portion  46 , by allowing the gas to flow through the guide unit  20 , the culture solution flow F 2  can be generated respectively between the guide unit  20  and the circulation units  22  on both sides thereof. Therefore, it is possible to efficiently cause the culture solution flow F 2  to be generated in the accommodation unit  16  and to cause the microalgae to be satisfactorily circulated, and hence to satisfactorily culture the microalgae. 
     In the culture device  10  according to the above-described embodiment, the inclined sections  50 , which are inclined in a direction away from the guide unit  20  from the lower side toward the upper side when the main body portion  46  is installed at the installation location, are formed in the circulation units  22  on the side of the guide unit inlet ports  38  by joining together the inner wall surfaces of the main body portion  46 . In this case, even if the microalgae settle inside the accommodation unit  16  under the action of gravity, the microalgae can be guided toward the guide unit inlet ports  38  via the inclined sections  50 . As a result, it is possible to cause the microalgae in the accommodation unit  16  to circulate more satisfactorily. It should be noted that the inclined sections  50  need not necessarily be provided in the main body portion  46 . 
     In the culture device  10  according to the above-described embodiment, the sealing members  52  isolated from the accommodation unit  16  are formed in the main body portion  46  by joining together the inner wall surfaces of the main body portion  46 , and the position fixing holes  56  used when the main body portion  46  is installed are provided on the sealing members  52 . In this case, the position fixing holes  56  can be provided in the main body portion  46  by means of a simple configuration in which the inner wall surfaces of the main body portion  46  are joined together to thereby form the sealing members  52 . By providing the position fixing holes  56  in this manner, it becomes possible to easily install the main body portion  46  at the installation location. It should be noted that the sealing members  52  and the position fixing holes  56  need not necessarily be provided in the main body portion  46 . 
     Instead of the main body portion  46  shown in  FIG.  6    and  FIG.  7   , the culture device  10  may be equipped with a main body portion  58  shown in  FIG.  8    and  FIG.  9   . The main body portion  58  shown in  FIG.  8    and  FIG.  9    mainly differs from the main body portion  46  shown in  FIG.  6    and  FIG.  7   , in that partitions  60  that extend in the direction in which the gas is supplied are included therein. 
     As shown in  FIG.  8   , the partitions  60  are formed by joining together the inner wall surfaces of the main body portion  58  by welding or the like. The length of the partitions  60  in the direction of extension thereof is set to be shorter than the length of the accommodation unit  16  in the vertical direction, and longer than the length of the joint members  18  in the direction of extension thereof. End parts  60   a  of the respective partitions  60  on the side of the arrow X2 in the direction of extension thereof are formed in an arcuate shape. The end parts  60   a  of the partitions  60  are arranged on the downstream side of the other end parts  18   b  of the joint members  18  (on the upper side, the side of the arrow X2). The inclined sections  50  are integrally provided at the ends of the respective partitions  60  on the side of the arrow X1 in the direction of extension thereof. 
     The accommodation units  16  are provided respectively on both sides of the partitions  60  of the main body portion  58  along the direction (the direction of the arrows X1 and X2) in which the partitions  60  extend. In the embodiment shown in  FIG.  8   , the main body portion  58  is provided with two partitions  60  at an interval in the direction of the arrows Y1 and Y2. Therefore, the main body portion  58  includes three accommodation units  16  that lie adjacent to each other via the partitions  60 . Each of the accommodation units  16  includes one guide unit  20 , and two circulation units  22  disposed on both sides of the guide unit  20 . 
     In other words, the main body portion  58  includes a total of three guide units  20  and six circulation units  22 . As shown in  FIG.  9   , in the main body portion  58 , when viewed in the vertical direction, the inner diameters of the guide units  20  are substantially the same, the inner diameters of the circulation units  22  are substantially the same, and the inner diameters of the guide units  20  are formed to be smaller than the inner diameters of the circulation units  22 . However, the relationship between the size of the inner diameters of the guide units  20  and the size of the inner diameters of the circulation units  22  is not particularly limited. 
     Further, the number of the partitions  60  provided in the main body portion  58  is not limited to two. For example, the main body portion  58  may have two accommodation units  16  by providing only one partition  60 , or may have four or more accommodation units  16  by providing three or more partitions  60 . Further, in the case that the main body portion  58  includes a plurality of the accommodation units  16 , instead of the direction (the vertical direction) in which the gas is supplied, a direction (the horizontal direction) perpendicular to the direction in which the gas is supplied may be set as the long-side direction of the main body portion  58 . 
     The accommodation units  16  communicate with each other via upstream side communication ports  61   a  provided on the upstream side (the side of the arrow X1) and downstream side communication ports  61   b  provided on the downstream side (the side of the arrow X2) of the accommodation units  16 . According to the present embodiment, as noted previously, the upstream side communication ports  61   a  are disposed between the inclined sections  50  provided at the ends of the partitions  60  on the side of the arrow X1, and the enclosure  34 . Further, the downstream side communication ports  61   b  are provided between the end parts  60   a  of the partitions  60  on the side of the arrow X2, and the enclosure  34 . 
     As noted previously, by the length of the partitions  60  in the direction of extension thereof being longer than the length of the joint members  18  in the direction of extension thereof, the other end parts  18   b  of the joint members  18  are arranged on the upstream side of the end parts  60   a  of the partitions  60  on the side of the arrow X2 (are arranged on the side of the arrow X1). In other words, the other end parts  18   b  of the joint members  18  are arranged on the upstream side of the downstream side communication ports  61   b.    
     The guide unit  20 , which extends in the long-side direction (the direction of the arrows X1 and X2), is provided substantially in the center of each of the accommodation units  16  in the short-side direction. The gas supply port  26  is provided below the guide unit  20  of each of the accommodation units  16 . In the respective accommodation units  16 , the facing portions  24  are provided so as to face toward the guide units  20  on the downstream side of the other end parts  18   b  of the joint members  18  and on the upstream side of the downstream side communication ports  61   b.    
     Among the circulation units  22  shown in  FIG.  8   , in the circulation unit  22  (a circulation unit  22   a ) that is disposed on the end on the side of the arrow Y1 closest to the collection port  32 , a triangular sealing member  52   a  is formed by the inclined section  50 , the bottom side portion  54 , and a portion of the enclosure  34  in the same manner as the circulation units  22  shown in  FIG.  6   . 
     Among the circulation units  22  shown in  FIG.  8   , in the circulation unit  22  (a circulation units  22   b ) that is disposed on the end on the side of the arrow Y2 farthest from the collection port  32 , a quadrangular sealing member  52   b  is provided. The sealing member  52   b  is formed by the inclined section  50 , an extending portion  62  that extends downward from the lower end part of the inclined section  50 , and a corner portion of the enclosure  34 . The extending portion  62  is formed by joining together the inner wall surfaces of the main body portion  58  by welding or the like. 
     Among the circulation units  22  shown in  FIG.  8   , in the circulation units  22  (circulation units  22   c ) that lie adjacent to each other via the partitions  60 , the inclined sections  50  are provided which branch off from the partitions  60 , and extend toward the side of the guide unit inlet ports  38  of the respective accommodation units  16 . By integrally providing, between the lower ends of the inclined sections  50 , bottom side portions  64  that extend along the short-side direction, triangular sealing members  52   c  are formed. The bottom side portions  64  are formed by joining together the inner wall surfaces of the main body portion  58  by welding or the like. 
     In the main body portion  58  as well, which is configured in the manner described above, by supplying the gas respectively via the gas supply ports  26 , the gas can be made to flow through the guide units  20  in the direction (the vertical direction) in which the gas is supplied. When the gas flows through each of the guide units  20 , the culture solution flow F 2  is generated in the interior of each of the accommodation units  16 . 
     The culture method, in which the culture device  10  equipped with the main body portion  58  shown in  FIG.  8    and  FIG.  9    is used, can be carried out in a similar manner to the culture method, in which the culture device  10  equipped with the main body portion  12  shown in  FIG.  1    and  FIG.  2    is used. Accordingly, in the culture device  10  equipped with the main body portion  58  shown in  FIG.  8    and  FIG.  9    and the culture method in which the culture device  10  is used as well, it is possible to satisfactorily culture the microalgae with a simple configuration while suppressing an increase in energy consumption. 
     In addition, in the culture device  10  equipped with the main body portion  58 , by means of a simple configuration in which the partitions  60  are provided, a plurality of the accommodation units  16  can be disposed in the main body portion  58 , and the microalgae can be satisfactorily circulated in the interior of each of these accommodation units  16 . Therefore, the total amount of the microalgae that are capable of being satisfactorily cultured in the culture device  10  can be increased. 
     In the culture device  10  according to the above-described embodiment, the accommodation units  16  on both sides of the partitions  60  communicate with each other via the upstream side communication ports  61   a  provided on the upstream side, and the downstream side communication ports  61   b  provided on the downstream side in the direction in which the gas is supplied. Also in this case, it is preferable to suppress the movement of the microalgae between the plurality of accommodation units  16 , for example, by setting the size and the arrangement of the upstream side communication ports  61   a  and the downstream side communication ports  61   b . Consequently, it becomes possible to satisfactorily culture the microalgae inside each of the accommodation units  16  that are substantially independent of each other. 
     In the culture device  10  according to the above-described embodiment, the other end parts  18   b  (the downstream side end parts), which are the end parts of the joint members  18  on the downstream side in the direction of extension thereof, are arranged on the upstream side of the downstream side communication ports  61   b . In addition, in the main body portion  58 , on the downstream side of the other end parts  18   b  of the joint members  18  and on the upstream side of the downstream side communication ports  61   b , the facing portions  24  that face toward the guide units  20  are formed by joining together the inner wall surfaces of the main body portion  58 . 
     In this case, the culture solution (the contents M), which flows inside the guide units  20  from the side of the guide unit inlet ports  38  toward the side of the guide unit outlet ports  40 , collides against the facing portions  24 , whereby it becomes easier for the culture solution to move toward the circulation units  22 , and the culture solution flow F 2  can be generated even more satisfactorily. Similarly, concerning the facing portion  24  shown in  FIG.  1   , the culture solution that flows inside the guide unit  20  collides against the facing portion  24 , whereby it becomes easier for the culture solution to move toward the circulation unit  22 , and the culture solution flow F 1  can be generated even more satisfactorily. Further, the culture solution (the contents M) that flows inside the guide units  20  collides against the facing portions  24 , whereby the culture solution is prevented from flowing into the adjacent accommodation units  16 , and movement of the microalgae between the plurality of accommodation units  16  is suppressed. 
     In the culture device  10  according to the above-described embodiment, the main body portion  58  is provided with one culture solution supply port  28  which is capable of supplying the culture solution to the accommodation units  16 . Even if the plurality of accommodation units  16  are provided in the main body portion  58  in the manner described above, these accommodation units  16  are capable of communicating with each other via the upstream side communication ports  61   a  and the downstream side communication ports  61   b . Therefore, it becomes possible to supply the culture solution and the microalgae to the plurality of accommodation units  16  from the one culture solution supply port  28 . In accordance with this feature, it becomes possible to easily supply the culture solution and the microalgae to the accommodation units  16 , and simplify the configuration of the culture device  10 . 
     In the culture device  10  according to the above-described embodiment, the accommodation unit  16  is surrounded by the enclosure  34  which is formed by joining together the inner wall surfaces of the main body portion  58 , the main body portion  58  is made from a material that transmits light, and the main body portion  58  is provided with one gas discharge port  30  that is capable of discharging the gas from the respective interiors of the accommodation units  16 , and one collection port  32  that is capable of collecting the culture solution and the microalgae from the respective interiors of the accommodation units  16 . 
     In this case, the so-called closed system culture device  10  can be obtained by means of a simple configuration in which the inner wall surfaces of the main body portion  58  are joined together to thereby form the enclosure  34 . Even if the culture device  10  is formed as a closed system in this manner, since the plurality of accommodation unit  16  communicate with each other via the upstream side communication ports  61   a  and the downstream side communication ports  61   b , the gas inside the accommodation units  16  can be discharged from one gas discharge port  30 . Similarly, the culture solution and the microalgae in the accommodation units  16  can be collected from one collection port  32 . Accordingly, it becomes possible to easily discharge the gas from the accommodation units  16  and collect the culture solution and the microalgae, and to simplify the configuration of the culture device  10 . 
     Moreover, according to the above-described embodiment, although the culture device  10  is provided as a closed system by forming the accommodation units  16  which are surrounded by the enclosures  34  in the main body portions  12 ,  46 , and  58 , it is possible to make the culture device  10  in the form of an open system by providing openings on the upper part of the accommodation units  16  without forming the enclosures  34 . In this case, it may be possible to discharge the gas and to collect the culture solution and the microalgae from the openings (not shown) of the accommodation units  16 . More specifically, the gas discharge port  30  and the collection port  32  need not necessarily be provided in the main body portions  12 ,  46 , and  58 . Further, for example, in the case it is possible to irradiate the microalgae with a sufficient amount of light through the openings of the accommodation units  16 , the main body portions  12 ,  46 , and  58  may be formed from a material that does not possess a light transmitting property. 
     REFERENCE SIGNS LIST 
     
         
           10  . . . culture device 
           12 ,  46 ,  58  . . . main body portion 
           14  . . . water storage tank 
           16  . . . accommodation unit 
           18  . . . joint member 
           18   c  . . . inner side surface 
           18   d  . . . outer side surface 
           20  . . . guide unit 
           22  . . . circulation unit 
           24  . . . facing portion 
           26  . . . gas supply port 
           28  . . . culture solution supply port 
           30  . . . gas discharge port 
           32  . . . collection port 
           34  . . . enclosure 
           36  . . . water storage unit 
           38  . . . guide unit inlet port 
           40  . . . guide unit outlet port 
           50  . . . inclined section 
           52 ,  52   a ,  52   b ,  52   c  . . . sealing member 
           56  . . . position fixing hole 
           60  . . . partition 
           61   a  . . . upstream side communication port 
           61   b  . . . downstream side communication port 
         F 1 , F 2  . . . culture solution flow 
         M . . . contents 
         W . . . stored water