Algae state determination device, algae culture device, and algae state determination method

Abstract

The present invention provides an algae state determination device that can determine the state of algae and is easily maintained. An algae state determination device (8) comprises a first light source (81) that emits light at a container that holds a culture liquid that includes algae from outside the container, a first light reception unit (83) that is provided outside the container and receives light that has been emitted from the first light source and transmitted by the container, and a determination unit (853) that determines the state of the algae on the basis of the amount of light received by the first light reception unit.

Description

Algae condition determination device, algae cultivation device, and algae condition determination method

[0001] The present invention relates to an algae state determination device that determines the state of algae in a culture solution, an algae culture device that includes the algae state determination device, and an algae state determination method.

[0002] Patent Document 1 discloses a seedling algae cultivation device. The cultivation device includes a seedling algae cultivation bag into which seedling algae and a seedling algae cultivation solution are poured, and a concentration measuring device for measuring the concentration of seedling algae in the seedling algae cultivation bag. The concentration measuring device is provided inside the seedling algae cultivation bag.

[0003] Japanese Patent Application Publication No. 2023-133030

[0004] In the cultivation device disclosed in Patent Document 1, the concentration measuring device is provided inside the seedling algae cultivation bag, which causes problems such as the concentration measuring device coming into contact with the seedling algae cultivation solution and becoming dirty, making maintenance of the concentration measuring device complicated. One aspect of the present invention aims to provide an algae state determination device that is easy to maintain and can determine the state of algae.

[0005] In order to solve the above problems, one embodiment of the algae state determination device of the present invention comprises: a first light source that irradiates light in a predetermined first direction from outside a container formed of a light-transmitting material for storing a culture solution containing algae; a first light receiving unit that receives light irradiated from the first light source and transmitted through the container and is provided outside the container; and a determination unit that determines the state of the algae based on the amount of light received by the first light receiving unit.

[0006] Furthermore, one aspect of the present invention provides an algae state determination method for determining the state of algae contained in a culture solution stored in a container formed of a light-transmitting material, and includes an irradiation step of irradiating light onto the container from outside the container in a predetermined first direction, a light receiving step of receiving the light irradiated by the irradiation step and transmitted through the container by a light receiving unit provided outside the container, and a determination step of determining the state of the algae based on the amount of light received by the light receiving step.

[0007] According to one aspect of the present invention, it is possible to realize an algae state determination device that is easy to maintain and is capable of determining the state of algae.

[0008] 1 is a cross-sectional view showing an example of the configuration of an algae culture device according to embodiment 1 of the present invention. FIG. 2 is a view of the portion surrounded by dotted line A1 in the algae culture device shown in FIG. 1 as viewed from the positive direction of the Z axis. FIG. 3 is a block diagram showing an example of the configuration of the main parts of an algae state determination device according to embodiment 1 of the present invention. FIG. 4 is a cross-sectional view showing the cross-sectional configuration of a first light source, a second light source, a first light receiving unit, and a second light receiving unit provided in the algae state determination device according to embodiment 1 of the present invention. FIG. 5 is a flowchart showing an example of an algae state determination method executed by the algae state determination device according to embodiment 1 of the present invention. FIG. 6 is a block diagram showing an example of the configuration of the main parts of an algae state determination device according to embodiment 2 of the present invention. FIG. 7 is a graph showing an example of fluctuations over time in the amount of light received by the second light receiving unit and the concentration of algae. FIG. 8 is a graph showing an example of fluctuations over time in the second attenuation amount and the concentration of algae. FIG. 9 is a graph showing the transition of illuminance transmitted through algae bodies in a culture test. FIG. 10 is a graph showing the correlation between the attenuation amount of light received by the first light receiving unit in a culture test and the OD value sampled in the culture test.

[0009] [First Embodiment] Hereinafter, one embodiment of the present invention will be described in detail.

[0010] <Configuration of Algae Cultivation Apparatus 1> Figure 1 is a cross-sectional view showing an example of the configuration of an algae cultivation apparatus 1 according to a first embodiment of the present invention. In Figure 1, the extension direction of the sunlit area 7 in the container 6 is the X-axis direction, the direction perpendicular to the ground on which the algae cultivation apparatus 1 is installed is the Z-axis direction, and the direction perpendicular to both the X-axis direction and the Z-axis direction is the Y-axis direction. The X-axis and Z-axis directions are also perpendicular to each other. The algae cultivation apparatus 1 is an apparatus that is installed outdoors and cultivates algae using a container 6. As shown in Figure 1, the algae cultivation apparatus 1 includes a container 2, a control panel 3, a tank 4, a pump 5, the container 6, and an algae state determination device 8.

[0011] The container 2 is a storage unit that houses a control panel 3, a tank 4, and a pump 5. The control panel 3 controls each part of the algae culture device 1. The tank 4 is a storage unit that stores the culture solution. The tank 4 is supported by a support part 41.

[0012] The pump 5 is a circulation unit that circulates the culture solution inside the container 6. By circulating the culture solution inside the container 6 with the pump 5, it is possible to reduce the settling of algae contained in the culture solution inside the container 6.

[0013] The container 6 is made of a light-transmitting material and stores a culture solution containing algae. The container 6 is a closed container in which the interior of the container 6 is sealed so that the culture solution inside the container 6 is not exposed to the air outside the container 6. Note that the container 6 is not limited to a closed container, and may be, for example, an open container in which the culture solution stored in the container 6 is exposed to the air outside the container 6.

[0014] The container 6 includes a sunshine area 7 and pipes P1, P2, and P3. The sunshine area 7 is an area that is irradiated by sunlight LS. The configuration of the sunshine area 7 will be described later. Pipe P1 connects the tank 4 and the pump 5. Pipe P2 connects the pump 5 and the sunshine area 7. Pipe P3 connects the sunshine area 7 and the tank 4.

[0015] The algae state determination device 8 determines the state of the algae in the vessel 6. As shown in Figure 1, the algae state determination device 8 is preferably located in a portion of the pipe P3 that is inside the container 2. The configuration of the algae state determination device 8 will be described later.

[0016] <Configuration of Sunshine Area 7> Figure 2 is a view of the area surrounded by dotted line A1 in the algae culture device 1 shown in Figure 1, viewed from the positive direction of the Z axis. As shown in Figure 2, the sunshine area 7 is tubular and U-shaped, and has extensions 71, 72 and a connection part 73. The sunshine area 7 extends in the X axis direction while being supported by a support part 75. This allows sunlight LS to be efficiently irradiated onto the algae inside the sunshine area 7. Note that the sunshine area 7 is not limited to being tubular and U-shaped, and may be, for example, a rectangular parallelepiped shape.

[0017] The extension portion 71 is tubular, and the negative side of the X-axis of the extension portion 71 is connected to the pipe P2, and the positive side of the X-axis of the extension portion 71 is connected to the connection portion 73. The connection portion 73 connects the extension portion 71 and the extension portion 72, thereby forming a U-shape in the sunlit area 7. The culture solution flows inside the connection portion 73.

[0018] The extension portion 72 is tubular, and the negative side of the X-axis of the extension portion 72 is connected to the pipe P3, and the positive side of the X-axis of the extension portion 72 is connected to the connection portion 73. The extension portions 71 and 72 are arranged side by side in the Y-axis direction. As shown by the arrows in Figure 2, the culture solution flows from the inside of the pipe P2 to the inside of the extension portion 71, and then from the inside of the extension portion 71 to the inside of the extension portion 72 via the inside of the connection portion 73. The culture solution also flows from the inside of the extension portion 72 to the inside of the pipe P3.

[0019] <Configuration of the Algae State Determination Device 8> Figure 3 is a block diagram showing an example of the configuration of the main parts of the algae state determination device 8 according to embodiment 1 of the present invention. As shown in Figure 3, the algae state determination device 8 includes a first light source 81, a second light source 82, a first light receiving unit 83, a second light receiving unit 84, a control unit 85, and a memory unit 86.

[0020] Fig. 4 is a cross-sectional view showing the cross-sectional configuration of the first light source 81, the second light source 82, the first light receiving unit 83, and the second light receiving unit 84 provided in the algae state determination device 8. The cross-section shown in Fig. 4 is a cross-section of a portion of the pipe P3 included in the container 6 that is surrounded by the first light source 81, the second light source 82, the first light receiving unit 83, and the second light receiving unit 84, cut along a plane perpendicular to the X-axis direction. This portion is the portion of the pipe P3 that extends in the X-axis direction.

[0021] The first light source 81 irradiates the container 6 with light L1 in a vertical direction from outside the container 6. In the example shown in FIG. 1 , the vertical direction is the same as the Z-axis direction. However, the "vertical direction" in which the first light source 81 irradiates light L1 may be any direction that can be considered to be substantially vertical, and may be tilted, for example, within a range of 5° with respect to the true vertical direction. The first light receiving unit 83 receives light L3 irradiated from the first light source 81 and transmitted through the container 6. The first light receiving unit 83 is provided outside the container 6.

[0022] The second light source 82 irradiates light L2 horizontally onto the container 6 from outside the container 6. In the example shown in FIG. 1 , the direction in which the second light source 82 irradiates light L2 is the same as the Y-axis direction. However, the "horizontal direction" in which the second light source 82 irradiates light L2 may be any direction that can be considered to be substantially horizontal, and may be tilted, for example, within a range of 5° with respect to the true horizontal direction. The second light receiving unit 84 receives light L4 irradiated from the second light source 82 and transmitted through the container 6. The second light receiving unit 84 is provided outside the container 6.

[0023] The first light source 81 and the second light source 82 may be, for example, white light-emitting diodes (LEDs). The first light-receiving unit 83 and the second light-receiving unit 84 may be, for example, an illuminance meter.

[0024] The control unit 85 controls the operation of the algae state determination device 8. As shown in Figure 3, the control unit 85 includes an irradiation unit 851, an acquisition unit 852, and a determination unit 853.

[0025] The irradiation unit 851 irradiates the container 6 with light L1 in a vertical direction from outside the container 6 using the first light source 81. The irradiation unit 851 also irradiates the container 6 with light L2 in a horizontal direction from outside the container 6 using the second light source 82.

[0026] The acquisition unit 852 acquires a signal output from the first light receiving unit 83 and indicating the amount of light L3 received by the first light receiving unit 83. The acquisition unit 852 also acquires a signal output from the second light receiving unit 84 and indicating the amount of light L4 received by the second light receiving unit 84.

[0027] The determination unit 853 determines the state of the algae based on the amount of light received by the first light receiving unit 83 and the second light receiving unit 84. In particular, the determination unit 853 determines whether or not precipitation has occurred in the algae. Specific details of the determination made by the determination unit 853 will be described later.

[0028] The memory unit 86 is a storage device that stores information necessary for control by the control unit 85. The memory unit 86 stores, for example, the amount of light received by each of the first light receiving unit 83 and the second light receiving unit 84 at each time. However, the memory unit 86 is not essential to the algae state determination device 8. If the algae state determination device 8 does not include the memory unit 86, the algae state determination device 8 may be communicably connected to an external storage device that stores information necessary for control by the control unit 85.

[0029] The algae state determination device 8 may further include an alarm device (not shown) that notifies the determination result by the determination unit 853. The alarm device may be, for example, a display device that outputs an image showing the determination result, or a speaker that outputs a sound showing the determination result. Alternatively, the algae state determination device 8 may be communicably connected to an external alarm device that notifies the determination result by the determination unit 853.

[0030] The positional relationship between the first light source 81 and the first light receiving unit 83 may be reversed from that shown in Fig. 4. Furthermore, the positional relationship between the second light source 82 and the second light receiving unit 84 may be reversed from that shown in Fig. 4. Furthermore, at least one of the control unit 85 and the storage unit 86 may be located on the control panel 3 or in the vicinity thereof.

[0031] <Determination by Determination Unit 853> The determination by the determination unit 853 will be described below. The determination unit 853 uses the amount of light received by each of the first light receiving unit 83 and the second light receiving unit 84 at a first point in time. The determination unit 853 also uses the amount of light received by each of the first light receiving unit 83 and the second light receiving unit 84 at a second point in time. The first point in time may be, for example, the point in time when the algae culture device 1 starts culturing algae. The second point in time is a point in time later than the first point in time. Specifically, the second point in time may be the point in time when the determination unit 853 determines the state of the algae.

[0032] The amount of attenuation of the amount of light received by the first light receiving unit 83 at a second time point relative to the amount of light received by the first light receiving unit 83 at a first time point is defined as a first attenuation amount. Also, the amount of attenuation of the amount of light received by the second light receiving unit 84 at a second time point relative to the amount of light received by the second light receiving unit 84 at the first time point is defined as a second attenuation amount. The determination unit 853 calculates the first attenuation amount D1 using the following formula (1), and calculates the second attenuation amount D2 using the following formula (2): D1=-log １０ (I12 / I11)...(1) D2=-log １０ (I22 / I21) (2) In equation (1), I11 is the amount of light received by the first light receiving unit 83 at a first time point, and I12 is the amount of light received by the first light receiving unit 83 at a second time point. In equation (2), I21 is the amount of light received by the second light receiving unit 84 at the first time point, and I22 is the amount of light received by the second light receiving unit 84 at the second time point.

[0033] Algae settling occurs on the vertically lower side of the container 6. Therefore, when algae settling occurs, light L1 emitted from the first light source 81 passes through the settled part of the algae and is attenuated more than when no algae settling occurs, becoming light L3 received by the first light receiving unit 83. On the other hand, even when algae settling occurs, light L2 emitted from the second light source 82 does not pass through the settled part of the algae, but passes through the part where the algae are floating above the settled part, becoming light L4 received by the second light receiving unit 84. Therefore, when algae settling occurs, the first attenuation amount is greater than the second attenuation amount.

[0034] The determination unit 853 determines that precipitation has occurred in the algae when the first attenuation is greater than the second attenuation. At this time, the determination unit 853 may take into consideration measurement errors of the first light receiving unit 83 and the second light receiving unit 84, and determine that precipitation has occurred in the algae when the difference obtained by subtracting the second attenuation from the first attenuation is equal to or greater than a predetermined threshold. Alternatively, the determination unit 853 may calculate the ratio of the second attenuation to the first attenuation, and determine that precipitation has occurred in the algae when the ratio is equal to or greater than a predetermined threshold.

[0035] <Algae State Determination Method> Figure 5 is a flowchart showing an example of an algae state determination method executed by the algae state determination device 8. In the algae state determination method, first, the irradiation unit 851 irradiates the container 6 with light in a vertical direction from outside the container 6 (S1, irradiation step). At this time, the irradiation unit 851 also irradiates the container 6 with light in a horizontal direction from outside the container 6.

[0036] The acquisition unit 852 receives light that has been irradiated in the irradiation step and transmitted through the container 6 using the first light receiving unit 83 and the second light receiving unit 84 (S2, light receiving step). Specifically, the acquisition unit 852 receives light that has been irradiated vertically onto the container 6 using the first light receiving unit 83, and receives light that has been irradiated horizontally onto the container 6 using the second light receiving unit 84. The acquisition unit 852 acquires a signal indicating the amount of light received by the first light receiving unit 83 and the second light receiving unit 84. Thereafter, the determination unit 853 determines the state of the algae based on the amount of light received in the light receiving step (S3, determination step).

[0037] <Effects> As described above, the algae state determination device 8 can determine the state of algae based on the amount of light received by the first light receiving unit and the amount of light received by the second light receiving unit. Here, the first light source 81, the second light source 82, the first light receiving unit 83, and the second light receiving unit 84 do not come into contact with the culture solution and are not contaminated by the culture solution. Therefore, it is possible to realize an algae state determination device that is easy to maintain and is capable of determining the state of algae.

[0038] Furthermore, the above-described formulas (1) and (2) are used to calculate the amount of attenuation of the light received by each of the first light receiving unit 83 and the second light receiving unit 84 at the second time point, based on the amount of light received by each of the first light receiving unit 83 and the second light receiving unit 84 at the first time point. Therefore, the determination unit 853 can determine whether or not precipitation has occurred in the algae without being affected by differences in the transmittance of the material forming the container 6 or by dirt on the container 6.

[0039] Furthermore, in the algae culture device 1, if the determination unit 853 determines that precipitation has occurred in the algae, the rotation speed of the pump 5 may be increased to agitate the culture solution and eliminate the precipitation. In other words, except when the determination unit 853 determines that precipitation has occurred in the algae, the rotation speed of the pump 5 may be decreased. This makes it possible to suppress precipitation of the algae while reducing stress on the algae and the temperature rise of the culture solution, and also reducing the load on the pump 5.

[0040] <Modification 1> The irradiation unit 851 may turn on / off both the first light source 81 and the second light source 82 at each of the first and second points in time. Furthermore, the acquisition unit 852 may acquire the following (i) to (iv) at each of the first and second points in time.

[0041] (i) A signal indicating the output of the first light receiving unit 83 when the first light source 81 is ON. (ii) A signal indicating the output of the first light receiving unit 83 when the first light source 81 is OFF. (iii) A signal indicating the output of the second light receiving unit 84 when the second light source 82 is ON. (iv) A signal indicating the output of the second light receiving unit 84 when the second light source 82 is OFF. In this case, in order to calculate the first attenuation amount D1 and the second attenuation amount D2, the judgment unit 853 may set I11, I12, I21, and I22 to the following values ​​in the above-mentioned equations (1) and (2), respectively. I11: The difference between the amount of light received by the first light receiving unit 83 at a first point in time, obtained by subtracting the amount of light when the first light source 81 is OFF from the amount of light when the first light source 81 is ON. I12: The difference between the amount of light received by the first light receiving unit 83 at a second point in time, obtained by subtracting the amount of light when the first light source 81 is OFF from the amount of light when the first light source 81 is ON. I21: The difference between the amount of light received by the second light receiving unit 84 at a first point in time, obtained by subtracting the amount of light when the second light source 82 is OFF from the amount of light when the second light source 82 is ON. I22: The difference between the amount of light received by the second light receiving unit 84 at a second point in time, obtained by subtracting the amount of light when the second light source 82 is OFF from the amount of light when the second light source 82 is ON. When I11, I12, I21, and I22 are set to these values, the net amount of transmitted light can be measured while reducing the influence of noise caused by external light other than the first light source 81 or the second light source 82. Therefore, the determination unit 853 can determine with higher accuracy whether precipitation has occurred in the algae.

[0042] <Modification 2> The algae state determination device 8 does not necessarily have to include the second light source 82 and the second light receiving unit 84. In other words, the determination unit 853 may determine the state of the algae based only on the amount of light received by the first light receiving unit 83.

[0043] In this case, the memory unit 86 may store a variation pattern of the first attenuation amount over time. The determination unit 853 can determine whether or not precipitation has occurred in the algae by comparing the first attenuation amount with the variation pattern when no precipitation has occurred in the algae.

[0044] As described above, the determination unit 853 of this modified example can determine whether precipitation has occurred in the algae based solely on the amount of light received by the first light receiving unit 83. Even in this case, the first light source 81 and the first light receiving unit 83 do not come into contact with the culture solution and are not contaminated by the culture solution. Therefore, an algae state determination device that is easy to maintain and capable of determining the state of the algae can be realized. However, if the algae state determination device 8 includes the second light source 82 and the second light receiving unit 84, it can more accurately determine whether precipitation has occurred in the algae.

[0045] [Embodiment 2] Another embodiment of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0046] 6 is a block diagram showing an example of the main components of an algae state determination device 8A according to embodiment 2 of the present invention. As shown in Fig. 6, the algae state determination device 8A differs from the algae state determination device 8 in that it includes a control unit 85A instead of the control unit 85. In addition to the components of the control unit 85, the control unit 85A further includes a concentration derivation unit 854.

[0047] The concentration deriving unit 854 derives the concentration of algae in the culture solution based on the second attenuation amount. Specifically, the determining unit 853 calculates the second attenuation amount using the above-mentioned formula (2). Furthermore, the concentration deriving unit 854 derives the concentration of algae using a calibration curve that shows the correlation between the second attenuation amount and the algae concentration. Specific details of the concentration deriving unit 854 will be described later.

[0048] FIG. 7 is a graph showing an example of the variation over time in the amount of light received by the second light receiving unit 84 and the concentration of algae. In FIG. 7, the horizontal axis represents elapsed time, the vertical axis on the left represents the amount of light (illuminance [Lux]) received by the second light receiving unit 84, and the vertical axis on the right represents the optical density (OD value) of the algae. The OD value was measured using an absorptiometer. In FIG. 7, graph 701 represents the amount of light received by the second light receiving unit 84, and graph 702 represents the OD value. In the example shown in FIG. 7, the amount of light received by the second light receiving unit 84 decreased and the OD value increased over time.

[0049] Fig. 8 is a graph showing an example of fluctuations in the second attenuation and algae concentration over time. In Fig. 8, the horizontal axis represents elapsed time, the left vertical axis represents the second attenuation (transmitted light attenuation), and the right vertical axis represents the OD value. Also in Fig. 8, graph 801 represents a calibration curve for the second attenuation, and graph 802 represents a calibration curve for the OD value. Furthermore, in Fig. 8, black dots represent actual measured values ​​of the second attenuation, and white dots represent actual measured values ​​of the OD value measured by an absorptiometer.

[0050] Graph 801 is expressed by the following formula (3), and graph 802 is expressed by the following formula (4). Graph 801: y = 0.5858269x - 26344.509 (3) Graph 802: y = 0.1428156x - 6422.429 (4) In graph 801, x is the elapsed time, and y is the second attenuation amount. In graph 802, x is the elapsed time, and y is the OD value. The calibration curve shown in graph 801 is an approximate straight line obtained from the actual measured values ​​of the second attenuation amount indicated by the black dots, and the calibration curve shown in graph 802 is an approximate straight line obtained from the actual measured values ​​of the OD value indicated by the white dots. The coefficient of determination R for the correlation between x and y in graph 801 is ２ The coefficient of determination R for the correlation between x and y in graph 802 was 0.9912. ２ was 0.9907.

[0051] From this, it can be said that both the second attenuation amount and the OD value have a strong positive correlation with elapsed time. That is, it can be said that there is also a positive correlation between the second attenuation amount and the OD value. In particular, there is a strong positive correlation between the second attenuation amount and the OD value in the early stages of culture. Therefore, the concentration derivation unit 854 can derive the OD value based on graphs 801 and 802. For example, in FIG. 8 , if the value of the second attenuation amount is 2, the concentration derivation unit 854 derives the OD value of graph 802 corresponding to the elapsed time t1 at which the value of the second attenuation amount becomes 2 in graph 801 as 0.45.

[0052] [Embodiment 3] As explained in Modification 2 of Embodiment 1, the algae state determination device 8 does not have to include the second light source 82 and the second light receiving unit 84. When the algae state determination device 8 does not include the second light source 82 and the second light receiving unit 84, the first light source 81 may irradiate the container 6 with light from outside the container 6 in a predetermined first direction that is not limited to the vertical direction.

[0053] An algae culture test was conducted, and an experiment was conducted to measure the transition of the light intensity of light received by the first light receiving unit 83 using an algae state determination device 8 that did not include the second light source 82 and the second light receiving unit 84. In the example shown in embodiment 2, the diameter of the pipe P3 where the measurement was performed was 250 mm, whereas in embodiment 3, the diameter of the pipe P3 was set to 100 mm. This increased the flow rate of the culture solution, making it less likely for precipitation to occur in the pipe P3. In addition, a light-reducing plate was provided on the pipe P3 to reduce the intensity of light incident from the first light source 81. Furthermore, a light-shielding sheet was provided on the pipe P3 to block light incident from sources other than the first light source 81.

[0054] 9 is a graph showing the change in illuminance transmitted through the algae during the culture test. In Fig. 9, the horizontal axis represents the measurement date and time, i.e., time, and the vertical axis represents the illuminance transmitted through the algae, i.e., the amount of light received by the first light-receiving unit 83 after passing through the algae in the pipe P3.

[0055] As shown in Figure 9, the overall trend was that the illuminance transmitted through the algae decreased as the algae grew over time. However, a temporary increase in the illuminance transmitted through the algae was observed at night. This is thought to be due to the fact that algae precipitated in the sunlit area 7 of the container 6 at night, resulting in a decrease in the algae concentration in the pipe P3.

[0056] In the culture test, in order to eliminate algae settling in the sunlit area 7, the culture solution in the sunlit area 7 was stirred by manually shaking or impacting the sunlit area 7. During stirring, the pump 5 was temporarily stopped to lower the liquid level of the culture solution in the sunlit area 7. At this time, almost no culture solution was present in the area where the first light source 81 and the first light receiving unit 83 were installed, which was located higher than the sunlit area 7. As a result, the illuminance transmitted through the algae temporarily rose to outside the range of the vertical axis in Figure 9. After stirring the sunlit area 7 to eliminate the algae settling, the pump 5 was driven again. As the algae settling was eliminated, the concentration of algae in the culture solution increased and the illuminance transmitted through the algae decreased.

[0057] As described above, even in an algae state determination device 8 that does not include a second light source 82 and a second light receiving unit 84, algae precipitation is manifested as an increase in the illuminance transmitted through the algae bodies. Therefore, the determination unit 853 can determine whether precipitation has occurred in the algae based on the illuminance transmitted through the algae bodies. Furthermore, if the determination unit 853 determines that precipitation has occurred in the algae, an operator can perform maintenance such as stirring the culture solution in the sunlit area 7. Note that stirring of the culture solution in the sunlit area 7 is not limited to the manual stirring described above, and may also be performed by repeatedly increasing and decreasing the operating frequency of the pump 5, for example.

[0058] 10 is a graph showing the correlation between the attenuation of light received by the first light-receiving unit 83 in a culture test and the OD value sampled in the culture test. In Fig. 10, the horizontal axis represents the first attenuation D1 calculated using the above formula (1), and the vertical axis represents the OD value. In Fig. 10, the black dots represent the actual measured OD value and the first attenuation D1 at the timing of measurement of the OD value, and the dashed line is an approximation line obtained from the actual measured values ​​indicated by the black dots.

[0059] The approximate line in Fig. 10 is expressed by the following formula (5): y = 0.3738x - 0.118 (5) In formula (5), y is the OD value, and x is the first attenuation amount D1. The coefficient of determination R for the correlation between x and y in the approximate line in Fig. 10 is ２ was 0.9972. From this, it can be said that the OD value has a strong positive correlation with the first attenuation amount D1.

[0060] As described above, in the culture test of embodiment 3, the diameter of the pipe P3 was smaller than that of the example shown in embodiment 2, so algae were less likely to settle in the pipe P3, and errors in the illuminance transmitted through the algae were less likely to occur. In addition, a light-shielding sheet was provided on the pipe P3 to reduce the effects of ambient light. Furthermore, a light-reducing plate was provided on the pipe P3 to adjust the intensity of the incident light from the first light source 81 to be close to the upper limit of the dynamic range of the first light-receiving unit 83. This improved the S / N ratio of the signal output from the first light-receiving unit 83, which indicates the amount of light L3 received by the first light-receiving unit 83. Due to these factors, the coefficient of determination R of the approximation line shown in FIG. 10 ２ is the coefficient of determination R of the approximation line shown in FIG. ２ It is thought to be larger than that.

[0061] [Example of implementation using software] The functions of the algae state determination device 8, 8A (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control unit 85, 85A).

[0062] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The functions described in each of the above embodiments are realized by executing the program using the control device and storage device.

[0063] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0064] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0065] [Summary] The present invention can also be expressed as follows.

[0066] The algae state determination device of aspect 1 of the present invention comprises a first light source that irradiates light in a predetermined first direction from outside a container formed of a light-transmitting material for storing a culture solution containing algae, a first light receiving unit that receives the light irradiated from the first light source and transmitted through the container and is provided outside the container, and a determination unit that determines the state of the algae based on the amount of light received by the first light receiving unit.

[0067] The algae state determination device of aspect 2 of the present invention is, in aspect 1, further configured such that the first direction is a vertical direction, and further includes a second light source that irradiates light horizontally onto the container from outside the container, and a second light receiving unit that receives light irradiated from the second light source and transmitted through the container and is provided outside the container, and the determination unit determines the state of the algae based on the amount of light received by the second light receiving unit in addition to the amount of light received by the first light receiving unit.

[0068] In the algae state determination device of aspect 3 of the present invention, in aspect 2, the attenuation amount of the amount of light received by the first light receiving unit at a second time point later than the first time point relative to the amount of light received by the first light receiving unit at the first time point is defined as a first attenuation amount, and the attenuation amount of the amount of light received by the second light receiving unit at the second time point relative to the amount of light received by the second light receiving unit at the first time point is defined as a second attenuation amount, and the determination unit determines that sedimentation has occurred in the algae if the first attenuation amount is greater than the second attenuation amount.

[0069] The algae state determination device of aspect 4 of the present invention, in aspect 2 or 3, further includes a concentration derivation unit that defines a second attenuation amount as the attenuation amount of the light quantity received by the second light receiving unit at a second point in time later than the first point in time relative to the light quantity received by the second light receiving unit at the first point in time, and derives the concentration of the algae in the culture solution based on the second attenuation amount.

[0070] An algae state determination device according to aspect 5 of the present invention comprises the algae state determination device according to any one of aspects 1 to 4 and the container.

[0071] The algae state determination method of aspect 6 of the present invention is a method for determining the state of algae contained in a culture solution stored in a container formed of a light-transmitting material, and includes an irradiation step of irradiating light onto the container from outside the container in a predetermined first direction, a light receiving step of receiving the light irradiated by the irradiation step and transmitted through the container by a light receiving unit provided outside the container, and a determination step of determining the state of the algae based on the amount of light received by the light receiving step.

[0072] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0073] REFERENCE SIGNS LIST 1 Algae culture device 6 Container 8, 8A Algae state determination device 81 First light source 82 Second light source 83 First light receiving unit 84 Second light receiving unit 853 Determination unit 854 Concentration derivation unit

Claims

1. An algae state determination device comprising: a first light source that irradiates light in a predetermined first direction from outside a container made of a light-transmitting material for storing a culture solution containing algae; a first light receiving unit that is provided outside the container and receives the light irradiated from the first light source and transmitted through the container; and a determination unit that determines the state of the algae based on the amount of light received by the first light receiving unit.

2. The algae state determination device described in claim 1, characterized in that the first direction is a vertical direction, and the device further comprises: a second light source that irradiates light horizontally onto the container from outside the container; and a second light receiving unit that receives light irradiated from the second light source and transmitted through the container and is provided outside the container, and the determination unit determines the state of the algae based on the amount of light received by the second light receiving unit in addition to the amount of light received by the first light receiving unit.

3. The algae state determination device described in claim 2, characterized in that the first attenuation is the amount of attenuation of the amount of light received by the first light receiving unit at a second time point later than the first time point relative to the amount of light received by the first light receiving unit at the first time point, and the second attenuation is the amount of attenuation of the amount of light received by the second light receiving unit at the second time point relative to the amount of light received by the second light receiving unit at the first time point.

4. The algae state determination device described in claim 2, further comprising a concentration derivation unit that defines a second attenuation amount as the attenuation amount of the light quantity received by the second light receiving unit at a second point in time later than the first point in time relative to the light quantity received by the second light receiving unit at the first point in time, and that derives the concentration of the algae in the culture solution based on the second attenuation amount.

5. An algae culture device comprising the algae state determination device according to any one of claims 1 to 4 and the container.

6. A method for determining the state of algae contained in a culture solution stored in a container made of a light-transmitting material, comprising: an irradiation step of irradiating light onto the container from outside the container in a predetermined first direction; a light receiving step of receiving the light irradiated by the irradiation step and transmitted through the container by a light receiving unit provided outside the container; and a determination step of determining the state of the algae based on the amount of light received by the light receiving step.

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