JP2020174579A - Microalga culture method and microalga culture device - Google Patents

Abstract

To maintain the culture environment of microalga in a sound state.SOLUTION: The microalga culture method includes a step (S12) of detecting nitrate respiration of microalga in a culture tank that stores culture medium containing microalga, and a step (S14) of promoting the flow of the culture medium of the culture tank on the basis of the detection of nitrate respiration of microalga.SELECTED DRAWING: Figure 4

Description

The present invention relates to a microalgae culturing method and a microalgae culturing apparatus.

For example, in Patent Document 1, when a toxic chemical substance flows into a sewage treatment process, the first effect of the toxic substance is inhibition of respiration of nitrifying bacteria, but ammonia-oxidizing bacteria and nitrite related to the nitrifying process. The purpose is to solve the problem of poor detection sensitivity of harmful substances because it is not known which of the oxidizing bacteria is being inhibited. Therefore, Patent Document 1 uses a membrane, carrier, or microbial sensor on which purely cultured ammonia-oxidizing bacteria are immobilized, and a membrane, carrier, or microbial sensor on which purely cultured nitrite-oxidizing bacteria are immobilized. The nitrification inhibitor is detected by measuring the dissolved oxygen concentration or the nitrite nitrogen concentration before and after the passage.

Japanese Unexamined Patent Publication No. 2000-206087

By the way, in recent years, there are many expectations for microalgae such as diatoms in various fields such as food and energy for utilizing their high growth characteristics and useful substances that can be extracted from cells.

Microalgae require nitrogen, phosphorus, and trace components for growth. Nitrogen is used for the synthesis of proteins and deoxyribonucleic acids (DNA), which are the basis of microalgae activity, so care must be taken not to be deficient in the growth of microalgae. Some microalgae performing photosynthesis, have the ability to fix atmospheric nitrogen, in the majority of microalgae, nitrogen NO ₃ in culture ^- is supplied in the form of such. It has been confirmed that some microalgae have the property of accumulating NO ₃ ⁻ in the body and using it for respiration when photosynthesis is not possible in dark places. This is nitric acid respiration performed by bacteria and the like, and is a type of anaerobic respiration that consumes nitric acid oxygen and uses it for respiration. Nitric acid respiration is a reaction that changes NO ₃ ⁻ to NO ₂ ⁻ , and if this NO ₂ ⁻ accumulates in the microbial environment for some reason, the function of the microorganism is impaired. For example, in wastewater treatment equipment (activated sludge), the performance of wastewater treatment deteriorates.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide a microalgae culturing method and a microalgae culturing apparatus capable of maintaining a healthy state for culturing microalgae.

In order to achieve the above-mentioned object, the microalgae culture method according to one aspect of the present invention includes a step of detecting nitrate respiration of the microalgae in a culture tank containing a culture solution containing the microalgae and a step of detecting the nitrate respiration of the microalgae. It comprises a step of promoting the flow of the culture solution in the culture tank based on the detection of nitrate respiration.

In the microalgae culture method according to one aspect of the present invention, it is preferable to measure the nitrite ion concentration of the culture solution in the step of detecting nitrate respiration of the microalgae.

In the microalgae culture method according to one aspect of the present invention, it is preferable to measure the oxidation-reduction potential of the culture solution in the step of detecting nitrate respiration of the microalgae.

In the microalgae culture method according to one aspect of the present invention, it is preferable that the step of promoting the flow of the culture solution is to promote the flow of the culture solution with a stirring blade.

In the microalgae culture method according to one aspect of the present invention, it is preferable that the step of promoting the flow of the culture solution is to promote the flow of the culture solution by means of bubbles.

In order to achieve the above object, the microalgae culture apparatus according to one aspect of the present invention includes a culture tank containing a culture solution containing microalgae, a detection means for detecting nitrate respiration of the microalgae, and the culture. It includes a promoting means for promoting the flow of the liquid and a control unit for controlling the promoting means based on the detection result of the detecting means.

In the microalgae culture apparatus according to one aspect of the present invention, the detection means is a nitrite ion measuring unit for measuring the nitrite ion concentration of the culture solution, and the control unit measures with the nitrite ion measuring unit. It is preferable to control the promotion means based on the results obtained.

In the microalgae culture apparatus according to one aspect of the present invention, the detection means is an oxidation-reduction potential measuring unit that measures the redox potential of the culture solution, and the control unit is measured by the redox potential measuring unit. It is preferable to control the promotion means based on the result.

In the microalgae culture apparatus according to one aspect of the present invention, the promoting means is a blade stirrer having a stirring blade arranged in the culture solution and a stirring driving unit for driving the stirring blade. It is preferable that the control unit controls the stirring drive unit of the blade stirring device based on the detection result of the detecting means.

In the microalgae culture apparatus according to one aspect of the present invention, the promoting means includes a bubble generating portion arranged in the culture solution to generate bubbles, an air supply portion for supplying air to the bubble generating portion, and the like. It is preferable that the control unit controls the air supply unit of the bubble agitator based on the detection result of the detection means.

According to the present invention, by promoting the flow of the culture solution in the culture tank based on the detection of nitrate respiration of microalgae, it accumulates and precipitates at the bottom of the culture tank and becomes anaerobic, and nitrate respiration is performed. Fine algae flow with the culture medium. This returns the microalgae to a healthy state of photosynthesis and oxygen respiration. As a result, according to the present invention, the culture environment for microalgae can be maintained in a healthy state.

FIG. 1 is a graph showing the relationship between the number of culture days and the cell concentration in relation to the microalgae culture method according to the embodiment of the present invention. FIG. 2 is a graph showing the relationship between the number of culture days and the nitrite concentration in relation to the microalgae culture method according to the embodiment of the present invention. FIG. 3 is a schematic configuration diagram showing a microalgae culture apparatus according to the first embodiment of the present invention. FIG. 4 is a flowchart showing a microalgae culture method according to the first embodiment of the present invention. FIG. 5 is a schematic configuration diagram showing a microalgae culture apparatus according to the second embodiment of the present invention. FIG. 6 is a flowchart showing a microalgae culturing method according to the second embodiment of the present invention. FIG. 7 is a schematic configuration diagram showing a microalgae culture apparatus according to the third embodiment of the present invention. FIG. 8 is a flowchart showing the microalgae culture method according to the third embodiment of the present invention. FIG. 9 is a schematic configuration diagram showing a microalgae culture apparatus according to the fourth embodiment of the present invention. FIG. 10 is a flowchart showing the microalgae culture method according to the fourth embodiment of the present invention.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components in the following embodiments include those that can be easily replaced by those skilled in the art, or those that are substantially the same.

FIG. 1 is a graph showing the relationship between the number of culture days and the cell concentration of the microalgae culture method according to the present embodiment. FIG. 2 is a graph showing the relationship between the number of culture days and the nitrite concentration related to the microalgae culture method according to the present embodiment.

In FIGS. 1 and 2, two types of culture devices containing a culture solution containing diatoms in a culture tank were prepared and cultured. The culture device is a large-scale light irradiation type culture device that is an improved beer tank. One of the culture devices is culture A (●) in which, for example, stirring is performed so that diatom accumulation does not occur at the bottom of the culture tank, and the other of the culture devices is culture B in which measures against diatom accumulation are not taken. (○).

In culture B (○), when measures are not taken to prevent the accumulation of diatoms at the bottom of the culture tank, as shown in FIG. 2, when the nitrite concentration becomes high, the cell concentration of diatoms is shown in FIG. Is declining rapidly. In culture B (◯), the increase in nitrite concentration and the decrease in diatom cell concentration are synchronized.

On the other hand, in culture A (●), measures are taken to prevent the accumulation of diatoms at the bottom of the culture tank and the like, and as shown in FIG. 2, the nitrite concentration does not increase. In culture A (●), the cell concentration of diatoms is increased as shown in FIG.

As described above, in the situation where diatoms are accumulated at the bottom of the culture tank or the like, the cell concentration of diatoms in the culture solution is lowered. The diatoms that have accumulated at the bottom of the culture tank are not dead, but in a densely precipitated state, they become anaerobic due to the inability to use light energy, and the nitrite concentration is rising, so nitric acid. It is thought that he is breathing.

In this way, in the culture of microalgae, the nitrite concentration and the cell concentration of the microalgae are closely related, and in order to cultivate the microalgae in a healthy state, it is necessary to create a culture environment that does not breathe nitric acid. There is.

[Embodiment 1]
FIG. 3 is a schematic configuration diagram showing the microalgae culture apparatus according to the first embodiment. FIG. 4 is a flowchart showing the microalgae culture method according to the first embodiment.

As shown in FIG. 3, the microalgae culture device 11 of the first embodiment includes a culture tank 2, a blade stirring device 3, a nitrite ion measuring unit 4, and a control unit 5.

The culture tank 2 contains a culture solution 10 containing microalgae (for example, diatoms that are microalgae (microalgae having a silicon shell such as keet cellos)). The culture tank 2 is for performing raceway culture, and has a track-shaped peripheral circuit 2A. In the culture tank 2, for example, the height of the culture medium 10 which is a medium may be, for example, 20 cm to 30 cm, the upper part may be opened and the inside may be open to the atmosphere, or the upper part may be closed by a lid member. It may be in a sealed state. However, when the upper part is closed with a lid member, the lid member is formed of a material that transmits light having a wavelength at which microalgae photosynthesize. Therefore, sunlight is supplied to the culture solution 10 in the culture tank 2. The culture tank 2 is not limited to the lid member, and the side surface portion may be formed of a material that transmits light in order to facilitate the intake of sunlight. Further, the culture tank 2 may be formed of a material whose bottom surface reflects light. Although not explicitly shown in the drawing, the culture tank 2 may be provided with a light source device that is artificial lighting that irradiates the culture solution 10 contained in the culture tank 2 with light.

Although not clearly shown in the figure, the culture tank 2 is a gas supply unit that supplies air to a microalgae supply unit that supplies microalgae, a culture solution supply unit that supplies a culture solution, and a culture solution 10 that contains microalgae. It may be provided with a part. In addition, the culture tank 2 also includes a level meter for measuring the liquid level of the culture solution 10, a temperature control unit for adjusting the temperature of the culture solution 10, a recovery unit for the culture solution 10, and cleaning of the culture tank 2. A discharge unit or the like that sometimes discharges the culture solution 10 may be provided.

The blade stirrer 3 stirs the culture solution 10 in the peripheral circuit 2A of the culture tank 2. The blade stirring device 3 includes a stirring blade 3A and a stirring driving unit 3B. The stirring blade 3A is rotatably provided in the peripheral circuit 2A of the culture tank 2. The stirring drive unit 3B drives the stirring blade 3A, and has, for example, a motor that rotates the stirring blade 3A. By stirring the culture solution 10 with the blade stirrer 3, the culture solution 10 containing microalgae is circulated in the peripheral circuit 2A of the culture tank 2 as shown by the arrow in FIG.

The nitrite ion measuring unit 4 measures the nitrite ion concentration of the culture solution 10. For example, a nitrite ion meter is applied to the nitrite ion measuring unit 4.

The control unit 5 is, for example, a computer, and is realized by an arithmetic processing unit including a microprocessor such as a CPU (Central Processing Unit), which is not specified in the figure. The control unit 5 controls the stirring drive unit 3B of the blade stirring device 3.

The control by the control unit 5, that is, the microalgae culture method will be described.

As shown in FIG. 4, the control unit 5 operates the stirring drive unit 3B of the blade stirring device 3 at a low speed (step S11). By operating the stirring drive unit 3B at a low speed, the control unit 5 rotates the stirring blade 3A at a low speed to stir the culture solution 10 contained in the culture tank 2 and causes the peripheral circuit 2A to rotate at a low flow velocity. The low flow rate is a speed at which the microalgae contained in the culture solution 10 can orbit around the circuit 2A together with the culture solution 10 without stagnation. For example, 0.3 m / sec is preferable, and the power consumption of the stirring drive unit 3B is preferable. It is a speed that suppresses.

The control unit 5 continuously or periodically acquires the nitrite ion concentration from the nitrite ion measurement unit 4, and whether the nitrite ion concentration is equal to or higher than the upper limit value during the low-speed operation (step S11) of the stirring drive unit 3B. Is determined (step S12). The upper limit of the nitrite ion concentration is preset in the control unit 5. The upper limit of the nitrite ion concentration is, for example, 2 mg / L or more, and when it is 2 mg / L or more, it is a numerical value obtained by an experiment that nitric acid respiration occurs and the cell concentration of microalgae decreases. ..

Then, in step S12, when the nitrite ion concentration is equal to or higher than the upper limit value (step S12: Yes), the control unit 5 operates the stirring drive unit 3B of the blade stirring device 3 at high speed (step S13). By operating the stirring drive unit 3B at high speed, the control unit 5 rotates the stirring blade 3A at high speed to stir the culture solution 10 contained in the culture tank 2 and causes the peripheral circuit 2A to rotate at a high flow velocity. The high flow velocity is a speed at which when the microalgae contained in the culture solution 10 are accumulated in the bottom of the culture tank 2 or the like, the accumulation can be peeled off and orbited in the peripheral circuit 2A together with the culture solution 10, for example, 1.0 m. / Sec is preferable. Therefore, by the high-speed operation of the stirring drive unit 3B, the microalgae accumulated in the bottom of the culture tank 2 and the like are peeled off from the bottom and the like, and the microalgae are circulated in the peripheral circuit 2A together with the culture solution 10. In step S12, when the nitrite ion concentration is not equal to or higher than the upper limit value (step S12: No), the control unit 5 continues the low-speed operation of the stirring drive unit 3B of the blade stirring device 3 (step S11).

When the microalgae accumulated in the bottom of the culture tank 2 or the like orbit around the circuit 2A together with the culture solution 10, the anaerobic state of the microalgae is eliminated from the viewpoint of the experiments of FIGS. 1 and 2, and the culture environment of the microalgae is eliminated. Because it becomes healthy, it stops breathing nitrate, and the cell concentration of microalgae increases as the number of nitrite ions decreases.

The control unit 5 continuously or periodically acquires the nitrite ion concentration from the nitrite ion measurement unit 4, and whether the nitrite ion concentration is below the lower limit value during high-speed operation (step S13) of the stirring drive unit 3B. Is determined (step S14). The lower limit of the nitrite ion concentration is preset in the control unit 5. The lower limit of the nitrite ion concentration is, for example, 1.5 mg / L or less, and when it is 1.5 mg / L or less, the situation where nitrate respiration occurs is eliminated and the cell concentration of microalgae increases. It is the obtained numerical value.

Then, in step S14, when the nitrite ion concentration is equal to or lower than the lower limit value (step S14: Yes), the control unit 5 operates the stirring drive unit 3B of the blade stirring device 3 at a low speed (step S15). That is, the control unit 5 operates the stirring drive unit 3B at a low speed to circulate the culture solution 10 in the peripheral circuit 2A at a low flow velocity (for example, 0.3 m / sec). After step S15, this control is terminated, and this control is performed again from step S11. In step S14, when the nitrite ion concentration is not equal to or lower than the lower limit value (step S14: No), the control unit 5 continues the high-speed operation of the stirring drive unit 3B of the blade stirring device 3 (step S13).

In the above-mentioned microalgae culturing method, the control unit 5 automatically controls the blade stirring device 3 in the microalgae culturing device 11, but when the control unit 5 is not used, that is, the blade stirring device 3 is manually operated. Steps S11 to S15 are similarly performed even in the microalgae culture method in which the above is operated.

As described above, the microalgae culturing method of the first embodiment is based on the step of detecting the nitrate respiration of the microalgae in the culture tank 2 containing the culture solution 10 containing the microalgae and the detection of the nitrate respiration of the microalgae. The step of promoting the flow of the culture solution 10 in the tank 2 is included.

Specifically, in the microalgae culture method of Embodiment 1, the step of detecting nitrate respiration of microalgae measures the nitrite ion concentration of the culture solution 10. Further, in the step of promoting the flow of the culture solution 10, the flow of the culture solution 10 is promoted by the stirring blade 3A.

The microalgae culture device 11 of the first embodiment includes a culture tank 2 containing a culture solution 10 containing microalgae, a detection means for detecting nitrate respiration of the microalgae, and a promotion means for promoting the flow of the culture solution 10. It includes a control unit 5 that controls the promotion means based on the detection result of the detection means.

Specifically, in the microalgae culture apparatus 11 of the first embodiment, the detection means is the nitrite ion measuring unit 4 for measuring the nitrite ion concentration of the culture solution 10, and the control unit 5 is the nitrite ion measuring unit 4. Control the facilitator based on the results measured in. Further, the promoting means is a blade stirring device 3 having a stirring blade 3A arranged in the culture solution 10 and a stirring driving unit 3B for driving the stirring blade 3A, and the culture solution is inside the culture tank 2. The culture solution 10 is moved into the culture tank 2 at the place where the 10 is housed. The control unit 5 controls the stirring drive unit 3B of the blade stirring device 3 based on the detection result of the detecting means.

Therefore, according to the first embodiment, by promoting the flow of the culture solution 10 in the culture tank 2 based on the detection of nitric acid respiration of microalgae, it accumulates and precipitates at the bottom of the culture tank 2 and becomes anaerobic. The microalgae that had been breathing nitric acid flow together with the culture solution 10. This returns the microalgae to a healthy state of photosynthesis and oxygen respiration. As a result, according to the first embodiment, the culture environment of the microalgae can be maintained in a healthy state.

Further, the detection of nitric acid respiration of microalgae can be carried out by measuring the nitrite ion concentration and determining by the control unit 5 using the nitrite ion measuring unit 4.

Further, the flow of the culture solution 10 can be promoted by the stirring blade 3A or controlled by the control unit 5 using the blade stirring device 3 having the stirring blade 3A and the stirring driving unit 3B.

The nitrite ion measuring unit 4 can improve the detection accuracy of nitrate respiration of microalgae by sampling the culture solution 10 in a place where microalgae easily accumulate in the culture tank 2. Further, the culture tank 2 may be provided with a concave portion or a convex portion where microalgae are likely to accumulate, and the nitrite ion measuring unit 4 samples the culture solution 10 in the vicinity of the concave portion or the convex portion to allow nitrate respiration of the fine algae. Detection accuracy can be improved.

[Embodiment 2]
FIG. 5 is a schematic configuration diagram showing a microalgae culture apparatus according to the second embodiment. FIG. 6 is a flowchart showing the microalgae culture method according to the second embodiment.

The microalgae culturing device 12 of the second embodiment is different from the microalgae culturing device 11 of the first embodiment in that the redox potential measuring unit 6 is provided instead of the nitrite ion measuring unit 4. Other configurations are the same as those of the microalgae culture apparatus 11 of the first embodiment, and the same reference numerals are given and the description thereof will be omitted.

The redox potential measuring unit 6 measures the redox potential (ORP: Oxidation Reduction Potential). The redox potential is the potential at which electron transfer occurs when oxidation and reduction occur.

The control by the control unit 5, that is, the microalgae culture method will be described.

As shown in FIG. 6, the control unit 5 operates the stirring drive unit 3B of the blade stirring device 3 at a low speed (step S21). By operating the stirring drive unit 3B at a low speed, the control unit 5 rotates the stirring blade 3A at a low speed to stir the culture solution 10 contained in the culture tank 2 and causes the peripheral circuit 2A to have a low flow velocity (for example, 0.3 m / m /). Make it go around in sec).

The control unit 5 continuously or periodically acquires the redox potential from the redox potential measurement unit 6, and determines whether the redox potential is below the lower limit value during the low-speed operation (step S21) of the stirring drive unit 3B. (Step S22). The lower limit of the redox potential is preset in the control unit 5. The lower limit of the redox potential is, for example, −50 mV or less, and −50 mV to −200 mV, which is a numerical value obtained by an experiment in which nitric acid respiration occurs and the cell concentration of microalgae decreases.

Then, in step S22, when the redox potential is equal to or lower than the lower limit value (step S22: Yes), the control unit 5 operates the stirring drive unit 3B of the blade stirring device 3 at high speed (step S23). By operating the stirring drive unit 3B at high speed, the control unit 5 rotates the stirring blade 3A at high speed to stir the culture solution 10 contained in the culture tank 2 and causes the peripheral circuit 2A to have a high flow velocity (for example, 1.0 m / m /). Make it go around in sec). Therefore, by the high-speed operation of the stirring drive unit 3B, the microalgae accumulated in the bottom of the culture tank 2 and the like are peeled off from the bottom and the like, and the microalgae are circulated in the peripheral circuit 2A together with the culture solution 10. In step S22, when the redox potential is not equal to or lower than the lower limit value (step S22: No), the control unit 5 continues the low-speed operation of the stirring drive unit 3B of the blade stirring device 3 (step S21).

When the microalgae accumulated in the bottom of the culture tank 2 or the like orbit around the circuit 2A together with the culture solution 10, the anaerobic state of the microalgae is eliminated and the culture environment of the microalgae becomes healthy, so that nitrate is used. It stops breathing and the cell concentration of microalgae increases as the nitrite ion decreases.

The control unit 5 continuously or periodically acquires the redox potential from the redox potential measurement unit 6, and determines whether the redox potential is equal to or higher than the upper limit value during high-speed operation (step S23) of the stirring drive unit 3B. (Step S24). The upper limit of the redox potential is preset in the control unit 5. The upper limit of the redox potential is a + value, for example, when it is 200 mV or more and 200 mV or more, the situation where nitric acid respiration occurs is eliminated and the cell concentration of microalgae increases. Is.

Then, in step S24, when the redox potential is equal to or higher than the upper limit value (step S24: Yes), the control unit 5 operates the stirring drive unit 3B of the blade stirring device 3 at a low speed (step S25). That is, the control unit 5 operates the stirring drive unit 3B at a low speed to circulate the culture solution 10 in the peripheral circuit 2A at a low flow velocity (for example, 0.3 m / sec). After step S25, this control is terminated, and this control is performed again from step S21. In step S24, when the redox potential is not equal to or higher than the upper limit value (step S24: No), the control unit 5 continues the high-speed operation of the stirring drive unit 3B of the blade stirring device 3 (step S23).

In the above-mentioned microalgae culturing method, the control unit 5 automatically controls the blade stirring device 3 in the microalgae culturing device 12, but when the control unit 5 is not used, that is, the blade stirring device 3 is manually operated. Steps S21 to S25 are similarly performed even in the microalgae culture method in which the above is operated.

As described above, the microalgae culturing method of the second embodiment is based on the step of detecting the nitrate respiration of the microalgae in the culture tank 2 containing the culture solution 10 containing the microalgae and the detection of the nitrate respiration of the microalgae. The step of promoting the flow of the culture solution 10 in the tank 2 is included.

Specifically, in the microalgae culture method of the second embodiment, the step of detecting nitric acid respiration of the microalgae measures the oxidation-reduction potential of the culture solution 10. Further, in the step of promoting the flow of the culture solution 10, the flow of the culture solution 10 is promoted by the stirring blade 3A.

The microalgae culture apparatus 12 of the second embodiment includes a culture tank 2 containing a culture solution 10 containing microalgae, a detection means for detecting nitrate respiration of the microalgae, and a promotion means for promoting the flow of the culture solution 10. It includes a control unit 5 that controls the promotion means based on the detection result of the detection means.

Specifically, in the microalgae culture apparatus 12 of the second embodiment, the detection means is the redox potential measuring unit 6 for measuring the redox potential of the culture solution 10, and the control unit 5 is the redox potential measuring unit 6. Control the facilitator based on the measured results. Further, the promoting means is a blade stirring device 3 having a stirring blade 3A arranged in the culture solution 10 and a stirring driving unit 3B for driving the stirring blade 3A, and the culture solution is inside the culture tank 2. The culture solution 10 is moved into the culture tank 2 at the place where the 10 is housed. The control unit 5 controls the stirring drive unit 3B of the blade stirring device 3 based on the detection result of the detecting means.

Therefore, according to the second embodiment, by promoting the flow of the culture solution 10 in the culture tank 2 based on the detection of nitric acid respiration of microalgae, it accumulates and precipitates in the bottom of the culture tank 2 and becomes anaerobic. The microalgae that had been breathing nitric acid flow together with the culture solution 10. This returns the microalgae to a healthy state of photosynthesis and oxygen respiration. As a result, according to the second embodiment, the culture environment of the microalgae can be maintained in a healthy state.

Further, the detection of nitric acid respiration of microalgae can be carried out by measuring the redox potential and determining by the control unit 5 using the redox potential measuring unit 6.

Further, the flow of the culture solution 10 can be promoted by the stirring blade 3A or controlled by the control unit 5 using the blade stirring device 3 having the stirring blade 3A and the stirring driving unit 3B.

The redox potential measuring unit 6 can improve the detection accuracy of nitric acid respiration of microalgae by measuring the redox potential of the culture solution 10 in a place where microalgae are likely to accumulate in the culture tank 2. Further, the culture tank 2 may be provided with a concave portion or a convex portion where microalgae are likely to accumulate, and the redox potential measuring unit 6 measures the redox potential of the culture solution 10 in the vicinity of the concave portion or the convex portion to make fine particles. The detection accuracy of nitrate respiration of algae can be improved.

[Embodiment 3]
FIG. 7 is a schematic configuration diagram showing the microalgae culture apparatus according to the third embodiment. FIG. 8 is a flowchart showing the microalgae culture method according to the third embodiment.

As shown in FIG. 7, the microalgae culture device 13 of the third embodiment includes a culture tank 21, a bubble agitator 31, a nitrite ion measurement unit 41, and a control unit 51.

The culture tank 21 contains a culture solution 10 containing microalgae (for example, diatoms (microalgae having a silicon shell such as keet cellos)). The culture tank 21 is used in a photobioreactor type culture system. The culture tank 21 may be formed in a rectangular tank shape, for example, in a state in which the upper portion is opened and the inside is open to the atmosphere, or in a state in which the upper portion is closed by a lid member and sealed. May be good. However, when the upper part is closed with a lid member, the lid member is formed of a material that transmits light having a wavelength at which microalgae photosynthesize. In addition, the culture tank 21 includes a light source device 71. The light source device 71 is artificial lighting that irradiates the inside of the culture tank 21 with light. That is, the light source device 71 irradiates the culture solution 10 contained in the culture tank 21 with light. The culture tank 21 is not limited to the lid member, and the side surface portion may be formed of a material that transmits light in order to facilitate the intake of sunlight. Further, the culture tank 21 may be formed of a material whose bottom surface reflects light.

Although not clearly shown in the figure, the culture tank 21 is a micro-algae supply unit that supplies micro-algae, a culture solution supply unit that supplies a culture solution, a level meter that measures the liquid level of the culture solution 10, and a culture solution. A temperature adjusting unit for adjusting the temperature of the culture solution 10, a collecting unit for the culture solution 10, a discharging unit for discharging the culture solution 10 when the culture tank 2 is washed, and the like may be provided.

The bubble agitator 31 agitates the culture solution 10 in the culture tank 21. The bubble agitator 31 has a bubble generating section 31A and an air supply section 31B. The bubble generating portion 31A is provided inside the culture tank 21. The bubble generating portion 31A may be provided at the bottom of the culture tank 21 or may be provided at the side portion. The bubble generating unit 31A ejects bubbles into the culture solution 10 by supplying air. The air supply unit 31B supplies air to the bubble generation unit 31A, and has, for example, a compressor. That is, the bubble agitator 31 agitates the culture solution 10 with the bubbles ejected from the bubble generation unit 31A. The bubble agitator 31 usually functions as an aeration device that aerates the microalgae contained in the culture solution 10.

The nitrite ion measuring unit 41 measures the nitrite ion concentration of the culture solution 10. For example, a nitrite ion meter is applied to the nitrite ion measuring unit 41.

The control unit 51 is, for example, a computer, and although not specified in the figure, it is realized by an arithmetic processing unit including a microprocessor such as a CPU (Central Processing Unit). The control unit 51 controls the air supply unit 31B of the bubble agitator 31.

The control by the control unit 5, that is, the microalgae culture method will be described.

As shown in FIG. 8, the control unit 51 operates the air supply unit 31B of the bubble agitator 31 at a low pressure (step S31). The control unit 51 operates the air supply unit 31B at a low pressure to reduce the amount of air supplied to the bubble generation unit 31A and eject a small amount of air bubbles from the bubble generation unit 31A, and the culture solution 10 contained in the culture tank 21. Is agitated and circulated at a low flow rate. The low flow rate is a speed at which the microalgae contained in the culture solution 10 can normally circulate in the culture tank 21 together with the culture solution 10 without stagnation. For example, 0.3 m / sec is preferable, and the power consumption of the air supply unit 31B is preferable. It is a speed that suppresses.

The control unit 51 continuously or periodically acquires the nitrite ion concentration from the nitrite ion measurement unit 41, and whether the nitrite ion concentration is equal to or higher than the upper limit value during the low pressure operation (step S31) of the air supply unit 31B. Is determined (step S32). The upper limit of the nitrite ion concentration is preset in the control unit 51. The upper limit of the nitrite ion concentration is the same as that of the first embodiment, and is, for example, 2 mg / L or more.

Then, in step S32, when the nitrite ion concentration is equal to or higher than the upper limit value (step S32: Yes), the control unit 51 operates the air supply unit 31B of the bubble agitator 31 at high pressure (step S33). The control unit 51 operates the air supply unit 31B at high pressure to increase the amount of air supplied to the bubble generation unit 31A, eject a large amount of air bubbles from the bubble generation unit 31A, and the culture solution 10 contained in the culture tank 21. Is stirred and circulated at a high flow velocity. The high flow velocity is a speed at which the microalgae contained in the culture solution 10 can be exfoliated and circulated together with the culture solution 10 when they are accumulated in the bottom of the culture tank 21, for example, 1.0 m / sec is preferable. .. Therefore, by high-pressure operation of the air supply unit 31B, the microalgae accumulated in the bottom of the culture tank 21 and the like are peeled off from the bottom and the like and circulated together with the culture solution 10. In step S32, when the nitrite ion concentration is not equal to or higher than the upper limit value (step S32: No), the control unit 51 continues the low-pressure operation of the air supply unit 31B of the bubble agitator 31 (step S31).

When the microalgae accumulated in the bottom of the culture tank 21 and the like circulate together with the culture solution 10, the anaerobic state of the microalgae is eliminated and the culture environment of the microalgae becomes healthy from the viewpoint of the experiments of FIGS. 1 and 2. Therefore, nitrate respiration is stopped and the cell concentration of microalgae increases as the nitrite ion decreases.

The control unit 51 continuously or periodically acquires the nitrite ion concentration from the nitrite ion measurement unit 41, and is the nitrite ion concentration below the lower limit value during the high-pressure operation (step S33) of the air supply unit 31B? Is determined (step S34). The lower limit of the nitrite ion concentration is preset in the control unit 5. The lower limit of the nitrite ion concentration is the same as that of the first embodiment, and is, for example, 1.5 mg / L or less.

Then, in step S34, when the nitrite ion concentration is equal to or lower than the lower limit value (step S34: Yes), the control unit 51 operates the air supply unit 31B of the bubble agitator 31 at a low pressure (step S35). That is, the control unit 51 operates the air supply unit 31B at a low pressure to circulate the culture solution 10 at a low flow velocity (for example, 0.3 m / sec). After step S35, this control is terminated, and this control is performed again from step S31. In step S34, when the nitrite ion concentration is not equal to or lower than the lower limit value (step S34: No), the control unit 5 continues the high-pressure operation of the air supply unit 31B of the bubble agitator 31 (step S33).

In the above-mentioned microalgae culturing method, the control unit 51 automatically controls the bubble stirring device 31 in the microalgae culturing device 13, but when the control unit 51 is not used, that is, the blade stirring device 31 is manually operated. Steps S31 to S35 are similarly performed even in the microalgae culture method in which the above is operated.

As described above, the microalgae culturing method of the third embodiment is based on the step of detecting the nitrate respiration of the microalgae in the culture tank 21 different from the first embodiment and the culture solution of the culture tank 21 based on the detection of the nitrate respiration of the microalgae. Includes 10 steps to promote flow.

Specifically, in the microalgae culture method of Embodiment 3, the step of detecting nitrate respiration of microalgae measures the nitrite ion concentration of the culture solution 10. Further, in the step of promoting the flow of the culture solution 10, the bubble generation unit 31A promotes the flow of the culture solution 10.

The microalgae culture apparatus 13 of the third embodiment has a culture tank 21 different from that of the first embodiment, a detection means for detecting nitric acid respiration of the microalgae, a promotion means for promoting the flow of the culture solution 10, and a detection means for the detection means. A control unit 51 that controls the promotion means based on the result is provided.

Specifically, in the microalgae culture apparatus 13 of the third embodiment, the detection means is the nitrite ion measuring unit 41 for measuring the nitrite ion concentration of the culture solution 10, and the control unit 51 is the nitrite ion measuring unit 41. Control the facilitator based on the results measured in. Further, the accelerating means is a bubble stirring device 31 having a bubble generating section 31A arranged in the culture solution 10 and an air supply section 31B for supplying air to the bubble generating section 31A, and the culture tank 21. The culture solution 10 is moved into the culture tank 21 at a place where the culture solution 10 is housed inside. The control unit 51 controls the air supply unit 31B of the bubble agitator 31 based on the detection result of the detection means.

Therefore, according to the third embodiment, by promoting the flow of the culture solution 10 in the culture tank 21 based on the detection of nitric acid respiration of microalgae, it accumulates and precipitates in the bottom of the culture tank 21 and becomes anaerobic. The microalgae that had been breathing nitric acid flow together with the culture solution 10. This returns the microalgae to a healthy state of photosynthesis and oxygen respiration. As a result, according to the third embodiment, the culture environment of the microalgae can be maintained in a healthy state.

Further, the detection of nitric acid respiration of microalgae can be carried out by measuring the nitrite ion concentration and determining by the control unit 51 using the nitrite ion measuring unit 41.

Further, the flow of the culture solution 10 can be promoted by the bubble generating unit 31A or by being controlled by the control unit 51 using the bubble stirring device 31 having the bubble generating unit 31A and the air supply unit 31B.

The nitrite ion measuring unit 41 can improve the detection accuracy of nitrate respiration of microalgae by sampling the culture solution 10 in a place where microalgae are likely to accumulate in the culture tank 21. Further, the culture tank 21 may be provided with a concave portion or a convex portion where microalgae are likely to accumulate, and the nitrite ion measuring unit 41 samples the culture solution 10 in the vicinity of the concave portion or the convex portion to allow nitrate respiration of the fine algae. Detection accuracy can be improved.

[Embodiment 4]
FIG. 9 is a schematic configuration diagram showing a microalgae culture apparatus according to the fourth embodiment. FIG. 10 is a flowchart showing the microalgae culture method according to the fourth embodiment.

The microalgae culturing device 14 of the fourth embodiment is different from the microalgae culturing device 13 of the third embodiment in that the redox potential measuring unit 61 is provided in place of the nitrite ion measuring unit 41. Other configurations are the same as those of the microalgae culture apparatus 13 of the third embodiment, and the same reference numerals are given and the description thereof will be omitted.

The redox potential measuring unit 61 measures the redox potential (ORP: Oxidation Reduction Potential) as in the second embodiment.

The control by the control unit 51, that is, the microalgae culture method will be described.

As shown in FIG. 9, the control unit 51 operates the air supply unit 31B of the bubble agitator 31 at a low pressure (step S41). The control unit 51 operates the air supply unit 31B at a low pressure to reduce the amount of air supplied to the bubble generation unit 31A and eject a small amount of air bubbles from the bubble generation unit 31A, and the culture solution 10 contained in the culture tank 21. Is stirred and circulated at a low flow rate (for example, 0.3 m / sec).

The control unit 51 continuously or periodically acquires the redox potential from the redox potential measuring unit 61, and determines whether the redox potential is equal to or lower than the lower limit value during the low pressure operation (step S41) of the air supply unit 31B. (Step S42). The lower limit of the redox potential is the same as that of the second embodiment, for example, −50 mV or less, and −50 mV to −200 mV.

Then, in step S42, when the redox potential is equal to or lower than the lower limit value (step S42: Yes), the control unit 51 operates the air supply unit 31B of the bubble agitator 31 at high pressure (step S43). The control unit 5 operates the air supply unit 31B at high pressure to increase the amount of air supplied to the bubble generation unit 31A, eject a large amount of air bubbles from the bubble generation unit 31A, and the culture solution 10 contained in the culture tank 21. Is agitated and circulated at a high flow velocity (for example, 1.0 m / sec). Therefore, by high-pressure operation of the air supply unit 31B, the microalgae accumulated in the bottom of the culture tank 21 and the like are peeled off from the bottom and the like and circulated together with the culture solution 10. In step S42, when the redox potential is not equal to or lower than the lower limit value (step S42: No), the control unit 51 continues the low-pressure operation of the air supply unit 31B of the bubble agitator 31 (step S41).

When the microalgae accumulated in the bottom of the culture tank 21 or the like circulate together with the culture solution 10, as described above, the anaerobic state of the microalgae is eliminated and the culture environment of the microalgae becomes healthy, so that nitrate breathing is stopped. As the number of nitrite ions decreases, the cell concentration of microalgae increases.

The control unit 51 continuously or periodically acquires the redox potential from the redox potential measuring unit 61, and determines whether the redox potential is equal to or higher than the upper limit value during the high-pressure operation (step S43) of the air supply unit 31B. (Step S44). The upper limit of the redox potential is preset in the control unit 51. The upper limit of the redox potential is a + value, for example, 200 mV or more, as in the second embodiment.

Then, in step S44, when the redox potential is equal to or higher than the upper limit value (step S44: Yes), the control unit 51 operates the air supply unit 31B of the bubble agitator 31 at a low pressure (step S45). That is, the control unit 51 operates the air supply unit 31B at a low pressure to circulate the culture solution 10 at a low flow velocity (for example, 0.3 m / sec). After step S45, this control is terminated, and this control is performed again from step S41. In step S44, when the redox potential is not equal to or higher than the upper limit value (step S44: No), the control unit 51 continues the high-pressure operation of the air supply unit 31B of the bubble agitator 31 (step S43).

In the above-mentioned microalgae culturing method, the control unit 51 automatically controls the bubble stirring device 31 in the microalgae culturing device 14, but when the control unit 51 is not used, that is, the blade stirring device 31 is manually operated. Steps S41 to S45 are similarly performed even in the microalgae culture method in which the above is operated.

As described above, the microalgae culturing method of the fourth embodiment is based on the step of detecting the nitrate respiration of the microalgae in the culture tank 21 different from the first embodiment and the culture solution of the culture tank 2 based on the detection of the nitrate respiration of the microalgae. Includes 10 steps to promote flow.

Specifically, in the microalgae culture method of the fourth embodiment, the step of detecting nitric acid respiration of the microalgae measures the oxidation-reduction potential of the culture solution 10. Further, in the step of promoting the flow of the culture solution 10, the bubble generation unit 31A promotes the flow of the culture solution 10.

The microalgae culture apparatus 14 of the fourth embodiment has a culture tank 21 different from that of the first embodiment, a detection means for detecting nitrate respiration of the microalgae, a promoting means for promoting the flow of the culture solution 10, and a detection means for detecting the microalgae. A control unit 51 that controls the promotion means based on the result is provided.

Specifically, in the microalgae culture apparatus 14 of the fourth embodiment, the detection means is the redox potential measuring unit 61 for measuring the redox potential of the culture solution 10, and the control unit 51 is the redox potential measuring unit 61. Control the facilitator based on the measured results. Further, the accelerating means is a bubble stirring device 31 having a bubble generating section 31A arranged in the culture solution 10 and an air supply section 31B for supplying air to the bubble generating section 31A, and the culture tank 21. The culture solution 10 is moved into the culture tank 21 at a place where the culture solution 10 is housed inside. The control unit 51 controls the air supply unit 31B of the bubble agitator 31 based on the detection result of the detection means.

Therefore, according to the fourth embodiment, by promoting the flow of the culture solution 10 in the culture tank 21 based on the detection of nitric acid respiration of microalgae, it accumulates and precipitates in the bottom of the culture tank 21 and becomes anaerobic. The microalgae that had been breathing nitric acid flow together with the culture solution 10. This returns the microalgae to a healthy state of photosynthesis and oxygen respiration. As a result, according to the fourth embodiment, the culture environment of the microalgae can be maintained in a healthy state.

Further, the detection of nitric acid respiration of microalgae can be carried out by measuring the redox potential and determining by the control unit 5 using the redox potential measuring unit 61.

Further, the flow of the culture solution 10 can be promoted by the bubble generating unit 31A or by being controlled by the control unit 51 using the bubble stirring device 31 having the bubble generating unit 31A and the air supply unit 31B.

The redox potential measuring unit 61 can improve the detection accuracy of nitric acid respiration of microalgae by measuring the redox potential of the culture solution 10 in a place where microalgae are likely to accumulate in the culture tank 21. Further, the culture tank 21 may be provided with a concave portion or a convex portion where microalgae are likely to accumulate, and the redox potential measuring unit 61 measures the redox potential of the culture solution 10 in the vicinity of the concave portion or the convex portion to make fine particles. The detection accuracy of nitrate respiration of algae can be improved.

10 Culture solution 11, 12, 13, 14 Micro-algae culture device 2,21 Culture tank 2A Circumferential circuit 3 Blade stirrer 3A Stirrer blade 3B Stirring drive unit 31 Bubble stirrer 31A Bubble generator 31B Air supply section 4,41 Nitrogen Ion measurement unit 5,51 Control unit 6,61 Oxidation-reduction potential measurement unit 71 Light source device

Claims (10)

A step of detecting nitrate respiration of the microalgae in a culture tank containing a culture solution containing microalgae, and
A step of promoting the flow of the culture solution in the culture tank based on the detection of nitrate respiration of the microalgae, and
A method for culturing microalgae, including. The microalgae culture method according to claim 1, wherein the step of detecting nitrate respiration of the microalgae is a step of measuring the nitrite ion concentration of the culture solution. The microalgae culture method according to claim 1, wherein the step of detecting nitric acid respiration of the microalgae is to measure the oxidation-reduction potential of the culture solution. The microalgae culture method according to any one of claims 1 to 3, wherein the step of promoting the flow of the culture solution is to promote the flow of the culture solution with a stirring blade. The microalgae culture method according to any one of claims 1 to 3, wherein the step of promoting the flow of the culture solution is to promote the flow of the culture solution by means of bubbles. A culture tank containing a culture solution containing microalgae and
A detection means for detecting nitric acid respiration of the microalgae and
As a means for promoting the flow of the culture solution,
A control unit that controls the promotion means based on the detection result of the detection means,
A microalgae culturing device. The detection means is a nitrite ion measuring unit that measures the nitrite ion concentration of the culture solution, and the control unit controls the promoting means based on the result measured by the nitrite ion measuring unit. The microalgae culture apparatus according to claim 6. The detection means is an oxidation-reduction potential measuring unit that measures the redox potential of the culture solution, and the control unit controls the promotion means based on the result measured by the oxidation-reduction potential measuring unit. Item 6. The microalgae culture apparatus according to Item 6. The accelerating means is a blade stirring device having a stirring blade arranged in the culture solution and a stirring driving unit for driving the stirring blade, and the control unit determines the detection result of the detection means. The microalgae culture apparatus according to any one of claims 6 to 8, which controls the stirring driving unit of the blade stirring apparatus based on the above. The promoting means is a bubble agitator having a bubble generating unit arranged in the culture solution to generate bubbles and an air supply unit for supplying air to the bubble generating unit, and the control unit is The microalgae culture apparatus according to any one of claims 6 to 8, wherein the air supply unit of the bubble agitator is controlled based on the detection result of the detection means.

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