JP4222495B2 - Carbon dioxide recycling system in closed system under microgravity - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carbon dioxide recycling system (carbon dioxide recycling apparatus) in a closed system in outer space or microgravity.
[0002]
[Prior art]
As the concept of space base construction is becoming reality, the need for long-term stay of humans or mammals in outer space is expected to increase in the future. For this purpose, a virtually unlimited supply of oxygen in a closed system is required. However, at present, no effective means has been developed, and development of a means for solving this is eagerly desired.
[0003]
Meanwhile, the present inventors have previously reported that Euglena, a kind of photosynthetic algae, can produce a large amount of algal bodies by inducing chlorophyll biosynthesis in the presence of high concentration of carbon dioxide (Aiga , Y. et al., “Growth of photosynthetic algae, Euglena, with light emitting diodes” CELSS J.9, 7-12, 1997, Nagahisa Nakano et al., “High CO of Euglena Gracilis₂Adaptation to conditions and its mechanism "CELSS J.,7, 15-18, 1995). Furthermore, the present inventors have also reported that Euglena cells contain extremely high nutrients such as proteins as revealed by amino acid analysis and rat breeding tests (Nagahisa Nakano et al., “Protist, Euglena gracilis Z is a closed ecosystem. It functions as the only source of nutrition in CELSS J.,8, 7-12, 1996). These characteristics of Euglena are very important not only in terms of providing human food in outer space or in a closed system under microgravity, but also in terms of developing a photobioreactor that converts carbon dioxide to oxygen The present inventors have come to pay attention.
[0004]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a carbon dioxide recycling system for converting carbon dioxide generated by a human or mammal into oxygen in a closed system in outer space or under microgravity.
[0005]
[Means for Solving the Problems]
The present inventors have advanced research to develop a recycling system that converts carbon dioxide into oxygen as a means for supplying oxygen in space or in a closed system under microgravity. First, the present inventors have conducted their own research (Nagahisa Nakano et al., CELSS,7, 15-18 (1995), Ichiro Aga et al., CELSS, 9, 7-12 (1997)). Euglena is easy to culture (1), especially under acidic conditions, (2) High photosynthetic capacity per unit volume (about 0.6 mol CO₂/ Hour ・ m^Three), (3) High utilization efficiency of light energy (80% or more), (4) Resistance to high-concentration carbon dioxide (40% CO₂/ Supply air, maximum growth is 5-15% CO₂Carbon dioxide using photosynthetic algae, paying attention to the fact that the protein contained in (5) and (5) is extremely good as a human food. Started building a recycling system. For this purpose, carbon dioxide produced by consumption of oxygen by mammals is supplied to the photosynthetic algae culture tank, and dissolved oxygen produced by the algae is separated from the algae culture solution under microgravity and supplied to the mammal breeding room. Requires construction. The inventors of the present invention have made extensive studies, and as a constituent element, a gas-liquid separation membrane capable of efficiently separating dissolved oxygen from a culture solution under microgravity and efficiently dissolving carbon dioxide in an algae culture solution. We were able to build a gas exchange device. Furthermore, as a result of studying the culture conditions of algae, etc., as a result of using a gas circulation line including the gas exchange device installed between the algae culture tank and the mammal breeding room in a closed system under microgravity, oxygen can be obtained. Supplying carbon dioxide that is consumed and produced by mammals to photosynthetic algae, and supplying mammals with dissolved oxygen that is consumed and produced by photosynthetic algae. The present invention has been completed by successfully constructing a carbon dioxide recycling system capable of maintaining the supplied oxygen level in a steady state for a long period of time.
[0006]
  That is, the gist of the present invention is (1) a light irradiation device for supplying energy to photosynthetic algae.HaveAlgal culture tank for culturing algae in algae culture solutionWhen,Mammal breeding room for raising mammalsAnd a liquid feed line for deriving the algae culture solution from the algae culture tank and returning it to the algae culture tank; and deriving the gas from the mammal breeding room and returning it to the mammal breeding room again without direct contact with the algae culture solutionGas circulation lineWhen,Includes gas-liquid separation membrane that allows gas to pass but not waterOnly oxygen and carbon dioxide are exchanged between the liquid feed line and the gas circulation line through a gas-liquid separation membrane.Gas exchange deviceAndThe gas exchange device, A non-selective gas-liquid separation membrane module that does not greatly change its permeation rate depending on the type of gas, and CO that can preferentially pass carbon dioxide among gases ₂ A selective gas-liquid separation membrane module,Carbon dioxide in the gas circulation lineAlgae in the liquid feed lineDissolve in the culture medium,AndIn the liquid feed lineBy taking dissolved oxygen in the algae culture into the gas circulation line,This is a gas exchange between oxygen generated by algae in an algae culture tank and carbon dioxide generated by a mammal in a mammal breeding room, and the amount of oxygen generated in the algae culture tank and the amount of carbon dioxide generated in a mammal breeding room are balanced. A carbon dioxide recycling system in a closed system under microgravity to maintain a balance between the amount of oxygen supplied to the mammalian breeding room and the amount of carbon dioxide supplied to the algae culture tank, (2) The photosynthetic algae are cyanobacteria, prokaryotic green algae, red algae, gray algae, crypto algae, dinoflagellates, golden algae, diatoms, brown algae, yellow green algae, hapto algae, rafido algae (green cyanobacterium), As described in (1) above, which is selected from the group consisting of chloracarnion algae, Euglena algae (Euglena algae), platino algae, green algae and axle algae (3) The system according to (1), wherein the photosynthetic algae are Euglena algae, (4) the system according to (1), wherein the photosynthetic algae are Chlorella algae, and (5) the photosynthetic algae is Chlamydomonas The system according to (1) above, which is a genus algae,(6The gas circulation line further includes a filter for removing foreign substances between the mammal breeding room and the gas exchange device.5) Any of the systems described in (7(1) to (1), wherein the blower pump is a pressure pump.6) Any of the systems described in (8(1) The light irradiation device of the algae culture tank uses sunlight as a light source, and at least a part of the algae culture device has a wall surface made of a material that transmits sunlight. ~ (7) Any of the systems described in (9(1) The light irradiation device of the algae culture tank uses an artificial light source, and the artificial light source is housed in a container made of a light-transmitting material. ~ (8) Any of the systems described in (10(1) to (1), wherein a temperature control device is further installed in the algal culture tank.9) Any of the systems described in (11(1) to (1) above, further comprising a carbon dioxide concentrator capable of preferentially introducing carbon dioxide in the mammal breeding room into the gas circulation line between the mammal breeding room and the gas exchange device.10) AnyAbout the system.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
Carbon dioxide (CO) in a closed system under microgravity of the present invention₂The recycling system includes an algae culture tank for culturing algae and a mammal breeding room for raising mammals including humans, and the algae culture tank is a light irradiation device for supplying energy to photosynthetic algae. And a water flow generator for circulating the culture fluid. If necessary, a temperature control device for adjusting the culture temperature can be installed. The algae culture tank and the mammal breeding room are connected by a gas circulation line so that the dissolved oxygen in the culture solution in the algae culture tank and the gas in the mammal breeding room can be exchanged. This gas circulation line includes a gas exchange device including a gas-liquid separation membrane that allows gas to pass but not water, and a blower pump for circulating the gas in the line. This gas exchange device dissolves carbon dioxide in the gas circulation line in the algae culture solution, and takes in dissolved oxygen in the culture solution in the algae culture solution into the gas circulation line, so that the algae are contained in the algae culture tank. Gas exchange is performed between the generated oxygen and the carbon dioxide that is generated in the mammal breeding room and enters the gas circulation line. By using such a carbon dioxide recycling system of the present invention, dissolved oxygen in the culture solution in which algae are generated in the algae culture tank is efficiently taken into the gas circulation line by the gas exchange device and then supplied to the mammal breeding room. The On the other hand, carbon dioxide generated by mammals in the mammal breeding room enters the gas circulation line and is efficiently dissolved in the algae culture solution by the gas exchange device. Therefore, by adjusting the oxygen generation amount in the algal culture tank and the carbon dioxide generation amount in the mammal breeding room using the system of the present invention, the mammals in the mammal breeding room can be adjusted even in a closed system under microgravity. By culturing algae in an algae culture tank while breeding, it is possible to maintain a balance between the amount of oxygen supplied to the mammal breeding room and the amount of carbon dioxide supplied to the algae culture tank.
[0008]
In the system of the present invention, as described in the above description of the gas exchange device, a gas-liquid separation membrane for separating dissolved oxygen generated in the algal culture solution from the culture solution is an essential component of the gas exchange device. It is installed as. The reason is that it is very easy to separate dissolved oxygen in the culture solution from the culture solution in the presence of gravity, but it is very difficult to do under microgravity. Under microgravity where there is no difference in specific gravity between gas and liquid, it is not easy to separate oxygen generated in the culture solution from the culture solution. As a result of intensive studies, the present inventors discovered that dissolved oxygen in a culture solution can be efficiently separated using a gas-liquid separation membrane, and the essential components of the system of the present invention It is a thing. That is, this gas exchange device makes contact between the gas circulation line leading to the mammal breeding room and the algal culture solution in this device through the gas-liquid separation membrane, and during this time, dissolved oxygen is transferred from the algal culture solution to the gas circulation line. At the same time, it works to dissolve carbon dioxide in the algae culture solution from the gas circulation line. By using this gas exchange device, dissolved oxygen in the culture solution in which algae are generated in the algae culture tank is efficiently sent to the mammal breeding room through the gas circulation line, and carbon dioxide generated by the mammals in the mammal breeding room. Will be efficiently sent to the algae culture through the gas circulation line. This device, for example, circulates the algae culture solution in a cylinder made of a gas-liquid separation membrane, collects oxygen that has passed through the membrane and moved out of the cylinder, and circulates outside the cylinder of the gas-liquid separation membrane A device in which carbon dioxide in the gas to be dissolved is dissolved in the cylinder, that is, in the algae culture solution. The gas-liquid separation membrane preferably has a large surface area in contact with the algal culture solution as much as possible. For example, a cylinder made of a meandering gas-liquid separation membrane can be exemplified. As the gas-liquid separation membrane used in this apparatus, a non-selective porous membrane (manufactured by Mitsubishi Rayon Co., Ltd., manufactured by Daicel Chemical Co., Ltd.) can be advantageously used. The membrane is not particularly limited as long as it is a membrane that does not allow liquid to pass through and is stable for a long period of time even when contacted with an algae culture solution.
[0009]
  The gas exchange device in the system of the present invention further includes CO.₂A selective gas-liquid separation membrane can be installed behind or in front of the non-selective gas-liquid separation membrane or alternately. CO₂The selective gas-liquid separation membrane is a membrane that preferentially permeates carbon dioxide with different permeation rates of oxygen and carbon dioxide. CO₂When a selective gas-liquid separation membrane is installed behind the above-mentioned non-selective gas-liquid separation membrane, the algae culture solution first contacts the non-selective gas-liquid separation membrane to transfer oxygen in the culture solution to the gas circulation line. Release, then CO₂Carbon dioxide can be efficiently received from the gas circulation line in contact with the selective gas-liquid separation membrane. When installed in the front, the algae culture solution is CO₂The carbon dioxide is efficiently received from the gas circulation line in contact with the selective gas-liquid separation membrane, and then oxygen is released to the gas circulation line in contact with the non-selective gas-liquid separation membrane. Such CO₂As a selective gas-liquid separation membrane (a membrane for carbon dioxide / oxygen separation), for example, a TPX membrane (Mitsubishi Rayon Co., Ltd.) or a large cell chemical company O₂/ CO₂It is preferable to use a membrane such as a separation membrane. A lightweight and efficient device is particularly useful for the present invention.preferable. Also,In order to prevent clogging of the gas-liquid separation membrane, it is preferable to provide a filter for removing foreign substances between the gas exchange device and the mammal breeding room.
[0010]
The gas circulation line in the system of the present invention includes the gas exchange device described above and connects the gas exchange device, the mammal breeding room and the algal culture tank with a pipe as necessary, and further applies pressure to the circulated gas. One or more pumps are provided as needed. The material of the pipe is not particularly limited, but a lightweight, strong and non-corrosive Teflon resin or silicon tube is preferable.
[0011]
The gas circulation line in the system of the present invention is connected to a mammal breeding room to preferentially pass carbon dioxide in the mammal breeding room to reduce the carbon dioxide concentration in the mammal breeding room, and at the same time, carbon dioxide in the gas circulation line. A carbon dioxide concentrator that works to increase the concentration can be installed. This apparatus is, for example, the above TPX membrane (Mitsubishi Rayon Co., Ltd.)₂/ CO₂CO such as separation membrane₂The selective gas-liquid separation membrane can be constituted by using it in multiple stages.
[0012]
The algae culture tank in the system of the present invention is equipped with a water flow generator. This is for sufficient mixing in the culture medium even in outer space or in microgravity. The homogenization of the culture solution is essential for optimizing the growth rate of algae by increasing the utilization efficiency of light and other nutrients such as carbon dioxide and energy source by algae. It is also useful for improving the dispersion of dissolved oxygen generated by algae and increasing the efficiency of taking up dissolved oxygen by the gas exchange device. Such a water flow generation device is not particularly limited as long as it is a device that can be normally used for water flow generation, such as a water flow pump or a propeller. Needless to say, an energy efficient device is preferable.
[0013]
The algae culture tank in the system of the present invention requires equipment for supplying light as an energy source for photosynthetic algae. This can be done by making a part of the wall of the algae culture tank with a light transmissive material, such as glass or light transmissive resin, so that sunlight can be used. It can also be achieved by mounting an artificial light source such as a light-emitting diode in a container made of a light-transmitting material as described above. Examples of such light sources include red LEDs (SLA-577JT3F, Rohm, Kyoto) and blue LEDs (Nichia Chemical Industries, Tokushima).
Furthermore, since the growth of the algae varies depending on the wavelength of the light to be applied, it is preferable to use a light source that emits light that is favorable for the growth of the algae and thus for the efficiency of oxygen generation by the algae. As such a light source, in the case of Euglena, for example, the red LED (wavelength 660 nm) or the common use (for example, 1: 1) of the red LED (wavelength 650 nm) and the blue LED (450 nm) is exemplified (Ichiro Aga et al. CELSS, 9, 7-12 (1997)).
[0014]
If necessary, a temperature control device may be attached to the algal culture tank in the system of the present invention. This is because it is necessary to suppress the temperature rise in the culture tank due to the culture of algae, control the temperature to be optimal for the growth of algae, and maximize the supply amount of oxygen. The temperature control device is not particularly limited as long as it is a device usually used in a microorganism culture tank. For example, a cool unit, a thermostat, etc. can be illustrated. In addition, although the suitable temperature of culture | cultivation of algae is 10-33 degreeC in the case of many algae containing Euglena, it is preferable to culture | cultivate at a higher temperature in the case of a thermophilic algae.
[0015]
The mammal breeding room in the system of the present invention refers to a closed space where a human lives when the mammal is a human, and refers to a closed space for raising a mammal when the mammal is an animal other than a human. Of course, the temperature and humidity are controlled and designed to be suitable for long-term survival. In order to monitor the concentration of carbon dioxide, a carbon dioxide concentration measuring device is preferably provided.
[0016]
The oxygen consumption of human (60 kg) is said to be about 250 ml / min at rest and about 2500 ml / min at maximum, and in mammals, mouse (35 g) is about 1 ml / min, pig (250 kg) is about 540 ml / min, And it is said that bovine (500 kg) is about 1040 ml / min (Rikagaku Dictionary (1998 edition)). On the other hand, the amount of carbon dioxide excreted per person is considered to be about 0.65 mol / hour at rest and usually about 1 mol / hour. In order to consume 1 mol of carbon dioxide in photosynthesis and generate equimolar oxygen, 9 mol of photons in the photosynthesis effective wavelength region (400 to 700 nm) are required. The total amount of solar radiation received by a plane facing the sun outside the Earth's atmosphere is 1.38 kW / m²Assuming that about 45% of this solar energy is available for photosynthesis, 1 m²About 10 moles of photons per hour per hour are falling outside the atmosphere of the earth (1 W / m as a relational expression between radiant flux density and photon flux density in the photosynthesis effective wavelength region in sunlight.²= 4.57 μmol photon / m²/ S). Therefore, assuming that all photons in the effective wavelength range for photosynthesis given to the culture vessel are used for photosynthesis, the photoreceptive surface of the culture vessel should always be placed at the position facing the sun on an orbiting satellite. If possible, about 1m of the light receiving surface²It is theoretically possible to convert carbon dioxide excreted by one person into oxygen using algae.
[0017]
The photosynthetic algae used in the present invention include cyanobacteria, prokaryotic green algae, red algae, gray algae, crypto algae, dinoflagellates, golden algae, diatoms, brown algae, yellow green algae, hapto algae, rafido algae (green whip) Algae), chloracranion algae, Euglena algae (Euglena algae), platino algae, green algae, axle algae, etc., and any of these can be used to achieve the object of the present invention. This is because all of these algae can consume carbon dioxide and perform photosynthesis to generate oxygen. Among them, algae having high photosynthetic ability, for example, Euglena genus algae, specifically, Euglena gracillis Z ATCC 12716, Euglena gracillis Z ATCC 12894, Euglena gracilis bal bacilaris ( Euglena gracillis var. Bacillaris) ATCC 10616, Euglena gracillis var. Preferred are Chlamydomonas algae, specifically Chlamydomonas reinhardtii ATCC 18798 and the like.
[0018]
Hereinafter, Euglena algae will be taken as an example of photosynthetic algae, and the culture conditions will be described. In addition, about other algae, the well-known conditions normally employ | adopted when carrying out photosynthesis using carbon dioxide as a carbon source can be used.
Euglena seed culture in an appropriate medium (cell density: 1-2 × 10⁶Cells / ml) is inoculated 10-25% (v / v), irradiated with light as an energy source, and cultured with stirring. In the presence of gravity, normally sterile air (about 0.5 to 2 times the volume of the medium per minute) is blown. As a result, carbon dioxide is dissolved in the culture solution. Under microgravity, carbon dioxide in the air is introduced into the culture solution using a gas-liquid separation membrane device.
As a suitable medium, for example, Kramer-Myers medium (1.0 g of (NH_Four)₂HPO_Four1.0g KH₂PO_Four0.2 g MgSO_Four・ 7H₂O, 0.02 g CaCl₂・ 2H₂O, 0.8 g citric acid, 3 mg Fe₂(SO_Four)_Three1.8 mg MnCl₂・ 4H₂O, 1.5 mg CoSO_Four・ 7H₂O, 0.4 mg ZnSO_Four・ 7H₂O, 0.2 mg Na₂MoO_Four・ 2H₂O, 0.02 mg CuSO_Four・ 5H₂O, 0.1 mg thiamine hydrochloride, and 0.0005 mg cyanocobalamin with a pH of 3.5 to 6.8, preferably 5.5) can also be conveniently used in the present invention.
[0019]
The culture temperature is 20 to 28 ° C, preferably 25 to 27 ° C.
Usually, after a lag time of about 1 day, a logarithmic growth phase is entered, and a stationary phase is entered in about 1 week to 10 days. Under this condition, when normal air is blown, about 2 × 10⁶Grow to cells / ml. When 5 to 20% carbon dioxide is mixed with air, the growth further increases, reaching about 2-3 times the number of cells each. If the percentage of carbon dioxide is increased to 45%, Euglena will not grow.
Even when a gas having a high carbon dioxide mixing ratio as described above is blown, the pH of the medium during culture is maintained between 4.5 and 6.0, and adjustment of the pH of the medium is unnecessary. This is a very advantageous property for the present invention.
[0020]
The light to irradiate may be sunlight, but Euglena grows actively even with light emitted by an artificial light source. According to our research (Ichiro Aiga et al., CELSS, 9, 7-12 (1997)), Euglena grows very well when irradiated with red LED alone or red LED and blue LED (1: 1). Show.
Vigorous growth means that much carbon dioxide is consumed and oxygen is released, which indicates that it is suitable as a culture condition for algae employed in the present invention.
[0021]
Furthermore, it is possible to make Euglena growth permanent by periodically collecting a part of the culture and supplying an equal amount of medium.
[0022]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples.
[0023]
Example 1
As a model of the closed carbon dioxide recycling system in outer space or microgravity according to the present invention, a closed carbon dioxide recycling system including a mammal breeding room and an algal culture tank shown in FIG. 2 was constructed.
[0024]
In this experiment, a circular glass culture tank (volume: 3 liters) was custom-made to transmit light and used as an algae culture tank. Six fluorescent lamps (Purook Ball, EFT25EW, manufactured by Matsushita Electric Works) were attached around the culture tank so that the light intensity could be adjusted. In order to control the temperature in the culture tank, water adjusted to 25 ° C. with a cooling device (Carry cool LP-3000CL-A, manufactured by ORION) was circulated in the lower part of the culture tank. An air pump (APN-085LV-1, manufactured by Iwaki Glass Co., Ltd.) was used to blow air in the gas circulation line. In order to release oxygen from the culture medium to the gas circulation line and to dissolve carbon dioxide from the gas circulation line to the culture liquid, a non-selective gas-liquid separation membrane module and CO₂A selective gas-liquid separation membrane module was used in combination. Non-selective gas-liquid separation membrane module and CO₂In order to circulate the culture liquid through the selective gas-liquid separation membrane module, a liquid feed line including a liquid feed pump (PST-550, manufactured by Iwaki Glass Co., Ltd.) is attached, and the liquid feed speed is 0.1 liter / min. did. Since this experiment was performed in the presence of gravity (on the ground), a stirring motor and wings were attached to the culture tank for the purpose of preventing cell precipitation.
[0025]
CO₂Mitsubishi Rayon's TPX membrane was used for the selective gas-liquid separation membrane module. This membrane is capable of carbon dioxide 1 ml / min (carbon dioxide released by one mouse 0.2-0.4m to take out²Is enough. In this experiment, one mouse is bred in a mammal breeding room.²TPX membrane is enough, but with a margin, 1.5m²A TPX membrane was used.
[0026]
Non-selective porous membrane (Mitsubishi Rayon Co., Ltd.) 1.5m is used for non-selective gas-liquid separation membrane module.²Was used to collect the abundant oxygen generated in the culture solution.
[0027]
The mammal breeding room has a size of 32 x 32 x 30 cm (volume of about 30 liters), and the air pump supplies 6 liters / minute of air to the gas circulation line at a pressure of 0.8 kg / cm.²It was blown with. The mammal breeding room and the algal culture tank are gas exchange devices (non-selective gas-liquid separation membrane module and CO₂A selective gas-liquid separation membrane module) was sandwiched and connected. One mouse (Balb / c, male, 15 weeks old, 30 g) was placed in the mammal breeding room and bred. The mammal breeding room was placed in a laboratory controlled at 25 ° C. together with an algae culture room and a gas exchange device. An air stirrer (OAFAN Model 9225, manufactured by SHICOH) was used to stir the air in the animal breeding room. CO₂A densitometer (Model TG-1300A, manufactured by Bionics Instrument) and an oximeter (Model OM-25ANL, manufactured by JIKCO) were attached.
[0028]
The algae culture tank (capacity: 3 liters) is charged with about 1.5 liters of seed culture (steady state cells) of Euglena gracillis Z ATCC 12716, added with Kramer-Myers medium, and the culture tank and gas The liquid feeding line including the exchange device was filled with the culture solution. The number of cells in the culture solution at this time is 7.75 × 10^FiveCells / ml.
[0029]
Experiment 1
When the gas circulation line is closed in the system of the present invention shown in FIG.
The experiment was started after confirming the closure of the system. The carbon dioxide concentration in the mammal room increases from 0.04% (400ppm) to 0.3% (3000ppm) in about 1 hour due to the carbon dioxide generated by the mouse (Figure 3). Stopped. At this time, a decrease in oxygen concentration was also observed.
[0030]
Experiment 2
In the system of the present invention shown in FIG. 2, a non-selective gas-liquid separation membrane module and CO ₂ A mammal breeding room and an algae culture tank are connected via a gas circulation line including a gas exchange device consisting of a selective gas-liquid separation membrane module, and mice are raised in the mammal breeding room. When only the medium is filled without Euglena
The experiment was started after confirming the closure of the system. The carbon dioxide concentration in the mammalian room increased sharply during the first 20 minutes due to the carbon dioxide generated by the mice, reaching 0.04% (400 ppm) to 0.135% (1350 ppm) (FIG. 4). ). Thereafter, carbon dioxide dissolves in the culture solution via the gas exchange device, so the rate of increase in the carbon dioxide concentration decreased, but continued to increase slowly, reaching 0.245% (2450 ppm) after 5 hours. Increased and mouse movement stopped.
[0031]
Experiment 3
When all the systems of the present invention shown in FIG. 2 are operated, that is, a non-selective gas-liquid separation membrane module and CO ₂ A mammal breeding room and an algae culture tank are connected via a gas circulation line including a gas exchange device consisting of a selective gas-liquid separation membrane module, and mice are raised in the mammal breeding room, while Euglena is irradiated with light in the algae culture tank. Cultivate If
The experiment was started after confirming the closure of the system. The above-mentioned Kramer-Myers medium is used as the medium for the algae culture tank, and the concentration of Euglena gratis ris ATCC 12716 is 7.55 × 10 5.^FiveCells / ml. The carbon dioxide concentration in the mammal room began to rise from 0.04% (400ppm) due to the carbon dioxide generated by the mouse, and reached 0.09% (900ppm) after 0.5 hours, but then declined. After 2.5 hours, an equilibrium value of 0.075% (750 ppm) was reached, and the equilibrium was maintained until 24 hours later (FIG. 5). In this situation, mouse movements displayed normal behavior similar to those in the atmosphere. When the light was turned off, Euglena could not perform photosynthesis, and the result was the same as that shown in FIG.
[0032]
The above experimental results indicate that a carbon dioxide recycling system using photosynthetic algae such as Euglena can be substantially constructed in a closed system under microgravity.
[0033]
【The invention's effect】
The carbon dioxide recycling system in a closed system under microgravity of the present invention recycles carbon dioxide generated by consumption of oxygen by mammals such as humans using photosynthetic algae in a closed system in outer space, etc., to oxygen again. One of the important problems for long-term survival, such as humans, will be substantially eliminated.
[Brief description of the drawings]
FIG. 1 shows a conceptual diagram of a carbon dioxide recycling system in a closed system under microgravity according to the present invention.
FIG. 2 is a conceptual diagram of a model of the system of the present invention used in the first embodiment.
FIG. 3 is a graph showing changes in carbon dioxide concentration in a mammal breeding room when a mouse is raised in the mammal breeding room and the gas circulation line is closed in the system of the present invention shown in FIG. 2;
4 shows a non-selective gas-liquid separation membrane module and CO in the system of the present invention shown in FIG.₂A mammal breeding room and an algal culture tank are connected via a gas circulation line including a gas exchange device consisting of a selective gas-liquid separation membrane module, and mice are raised in the mammal breeding room. It is a graph which shows the change of the carbon dioxide concentration in the mammal breeding room at the time of filling only a culture medium without including Euglena.
FIG. 5 shows a case where the system of the present invention shown in FIG. 2 is used, that is, a non-selective gas-liquid separation membrane module and a CO.₂When a mammalian breeding room and an algal culture tank are connected via a gas exchange device consisting of a selective gas-liquid separation membrane module, mice are raised in the mammalian breeding room, and Euglena is cultured while irradiating light in the algal culture tank. It is a graph which shows the change of the carbon dioxide concentration in a mammal breeding room.

Claims (11)

An algae culture tank for culturing algae in an algae culture solution having a light irradiation device for supplying energy to photosynthetic algae ;
A mammal breeding room for raising mammals ;
A liquid feed line for deriving the algae culture solution from the algae culture tank and returning it back to the algae culture tank;
A gas circulation line for deriving gas from the mammal breeding room and returning it to the mammal breeding room again without direct contact with the algae culture solution ;
Passing the gas is a gas exchange apparatus for exchanging oxygen and carbon dioxide through a gas-liquid separation film between the gas-liquid separation membrane impervious to water and unrealized the feed line and the gas circulation line,
The gas exchange device includes a non-selective gas-liquid separation membrane module that does not greatly change its permeation rate depending on the type of gas, and a CO ₂ selective gas that can preferentially pass carbon dioxide among gases. and a liquid separation membrane module, wherein the carbon dioxide in the gas circulation line dissolved in algae culture in in the liquid sending line, and dissolved oxygen the gas circulation of the algal culture in in the feed line By taking in the line, gas exchange between oxygen generated by algae in the algae culture tank and carbon dioxide generated by mammals in the mammal breeding room,
The amount of oxygen generated in the algae culture tank and the amount of carbon dioxide generated in the mammal breeding room are adjusted so as to balance, the amount of oxygen supplied to the mammal breeding room and the amount of carbon dioxide supplied to the algae culture tank. Carbon dioxide recycling system in a closed system under microgravity to maintain equilibrium.   The photosynthetic algae are cyanobacteria, prokaryotic green algae, red algae, gray algae, crypto algae, dinoflagellate algae, golden algae, diatoms, brown algae, yellow green algae, hapto algae, rafido algae (green whit algae), chloracarnion The system according to claim 1, wherein the system is selected from the group consisting of algae, Euglena algae (Euglena algae), platino algae, green algae and axle algae.   The system according to claim 1, wherein the photosynthetic algae are Euglena algae.   The system according to claim 1, wherein the photosynthetic algae is a Chlorella algae.   The system according to claim 1, wherein the photosynthetic algae is Chlamydomonas algae. The system according to any one of claims 1 to 5, wherein the gas circulation line further includes a filter for removing foreign substances between the mammal breeding room and the gas exchange device. The system according to any one of claims 1 to 6, wherein the blower pump is a pressure pump. The light irradiation device of the algae culture tank uses sunlight as a light source, and at least a part of the algae culture device has a wall surface made of a material that transmits sunlight. Item 8. The system according to any one of Items 7 . The light irradiation device of the algae culture tank uses an artificial light source, and the artificial light source is housed in a container made of a light transmissive material. Item 9. The system according to any one of Items 8 . The system according to any one of claims 1 to 9 , wherein a temperature control device is further installed in the algal culture tank. Claims 1 in which further installing the carbon dioxide concentration apparatus capable of introducing carbon dioxide of the mammal rearing chamber preferentially gas circulating line between said mammal breeding chamber and the gas exchange apparatus 10 The system according to any one of the above.

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