JP2010148433A - Method for fixing carbon dioxide gas and system thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for fixing carbon dioxide gas in the air with which a culture is performed even using a high-concentration carbon dioxide gas, a culture solution in which carbon dioxide gas is dissolved is approximately uniformly introduced into a culture tank and dissolved carbon dioxide gas concentration in the culture tank is simply controlled and a system therefor. <P>SOLUTION: The system for fixing a carbon dioxide gas includes a carbon dioxide gas source for supplying at least a carbon dioxide gas, a culture system containing at least a culture solution for culturing a chloroplast-containing protozoan or native vegetation, a system for preparing a culture solution of dissolved carbon dioxide gas from a gas containing at least a carbon dioxide gas supplied from the carbon dioxide gas source and the culture solution, at least one carbon dioxide gas liquid-communicating tube for communicating the carbon dioxide gas source to the system for preparing the culture solution of dissolved carbon dioxide gas, and at least two culture solution communicating tubes for liquid-communicating the culture system to the system for preparing the culture solution of dissolved carbon dioxide gas. The method for fixing a carbon dioxide gas makes good use of the system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and system for fixing and removing unnecessary carbon dioxide contained in the atmosphere.

  A global problem due to an increase in the concentration of carbon dioxide in the atmosphere has become a social issue. Various methods have been proposed as means for solving this global problem, and among these, a method of fixing carbon dioxide with protozoa and algae belonging to Euglena has attracted attention (Patent Document 1, Patent Document 2).

  In general, in photosynthesis by chlorophyll in cells of protozoa belonging to Euglena and algae inhabiting freshwater and seawater (hereinafter collectively referred to as “protoplasts and plants with chloroplasts”), the higher the carbon dioxide concentration, the higher It can be expected that the photosynthesis speed will increase.

  In addition, it is preferable to increase the population density of protoplasts and plants with chloroplasts in order to save equipment space, so that carbon dioxide gas is supplied evenly to individual chloroplasts and plants and plants that have a high population density. In addition, it is necessary to increase the dissolved concentration of carbon dioxide in the culture solution.

  However, in the method using a protozoan belonging to Euglena, when the carbon dioxide concentration in the gas aerated in the culture solution increases, the carbon dioxide assimilation protein in the cells of the protozoa is altered and the aerated carbon dioxide gas It is said that there is a problem that the protozoan is killed when the concentration of is over about 50% (Non-patent Document 1).

  In Non-Patent Document 1, as shown in the figure below, the carbon dioxide concentration in the gas aerated in the culture solution peaks at 15 to 20%, and the growth rate of Euglena decreases as the concentration increases. The unique property of Euglena is disclosed that when it reaches 80%, it will die.

出典：非特許文献１

Source: Non-Patent Document 1

  In order to confirm this characteristic, the present inventors conducted a supplementary test under the experimental conditions as described in Comparative Example 1 described below. As a result, a gas having a carbon dioxide concentration of almost 100% was contained in the Euglena culture solution. When aeration was performed directly, it was confirmed that most Euglena was killed and that cell fragments after the death were scattered in the culture solution (see FIG. 8).

  On the other hand, in the case where carbon dioxide is fixed by algae that inhabit freshwater or seawater, carbon dioxide is generally aerated in the culture solution. In this case, in the gas aerated in the culture solution Patent Document 2 points out a problem that when the concentration of carbon dioxide gas increases, bicarbonate ions and carbonate ions are generated in the culture solution, and as a result, the pH of the culture solution decreases and the algae die.

  In order to solve this problem, Patent Document 2 discloses that a pH adjusting means is provided for controlling the culture medium to be alkaline by electrolysis, but the system operation is complicated. There is a problem to say. For example, even if an aqueous solution containing an electrolyte is electrolyzed to maintain alkalinity, the region where alkalinity can be maintained is only around the cathode, and metal ions in the electrolyte are deposited on the anode, and an acidic region around it. In addition, since the diffusion rate of molecules and ions in the aqueous solution is extremely slow, it is possible to maintain a uniform pH of the aqueous solution in the tank when the tank containing the algae is enlarged. There were problems such as difficulties.

  Further, even the novel microalgae with low pH tolerance disclosed in Patent Document 3 has the same problem as in Euglena as described in Non-Patent Document 1, that is, in the gas aerated in the culture solution. It is disclosed that the carbon dioxide concentration peaks at a certain value, and the growth rate decreases as the concentration increases, and conversely dies (see the figure below). However, Patent Document 2 recognizes such a problem. And no solution is taught.

（出典：特許文献３）

(Source: Patent Document 3)

  Assuming that the causes of the problems inherent in the prior art as described above are considered without restricting the technical scope of the present invention, the following is assumed. That is, when a gas containing carbon dioxide gas is passed through the culture solution, the porous material is formed so that the gas containing the carbon dioxide gas is as small as possible in order to increase the contact area between the gas and the culture solution. Although it is common to ventilate the culture solution through ceramics or hollow fibers, the pressure in the bubbles that appear in the culture solution must exceed atmospheric pressure regardless of the means of ventilation. . In such a case, according to the well-known Henry's law, the carbon dioxide gas in the bubble is very close to the interface between the bubble and the liquid compared to a place far away from the bubble and under atmospheric pressure. Are expected to dissolve more. As is well known, when carbon dioxide gas is dissolved in a liquid, the pH of the liquid is lowered, and in extreme cases, it may be assumed that the acidity becomes strong acid such as 1 or 2. For example, Patent Document 3 discloses that pH is lowered to about 4 when a gas having a partial pressure of carbon dioxide of 20% is blown into a seawater-based culture solution having a strong buffering action. Then, it is assumed that the cell membrane of each chlorophyll-carrying native plant and animal that existed near the interface by chance is dissolved by a strong acid. It is assumed that such a phenomenon appears remarkably in a chloroplast-bearing native plant or animal whose size is much smaller than the size of bubbles of carbon dioxide-containing gas generated in the culture solution by aeration.

  However, in the conventional techniques represented by Patent Document 1 to Patent Document 3 relating to carbon dioxide fixing methods utilizing protozoa and microalgae that perform photosynthesis while floating in water, the above problems have been recognized at all. There wasn't.

  Therefore, as a result of intensive research aimed at providing a carbon dioxide fixing method capable of fixing carbon dioxide simply and efficiently and further effectively utilizing the fixed organic matter, surprisingly, the inventors have Carbon dioxide dissolves at a substantially saturated concentration (under atmospheric pressure) as long as the gas is not directly vented into the culture solution, or unless the aerated carbon dioxide-containing gas bubbles and Euglena are in direct contact with each other. It was found for the first time that Euglena was not killed and its photosynthetic function was not impaired at all even in the case of the prepared culture solution. The present inventors have developed a simple carbon dioxide fixation method and a system thereof that do not require adjustment of the pH of a culture solution while using protoplasts and plants that possess chloroplasts.

JP 2002-262858 A JP 2008-22740 A JP-A-7-51051 Nakano Nagahisa et al., CELSS Journal, 10 (21), 12-23, 1995 Meteorological Research Institute Technical Report, No. 41, 2000, p. 6

  That is, the present invention uses a gas-liquid mixing apparatus (gas-liquid mixing apparatus disclosed in International Application No. PCT / JP2007 / 066197) invented by the same inventors as the present invention, and carbon dioxide gas is substantially reduced under atmospheric pressure. Separately prepare a high-concentration carbon dioxide-dissolved culture solution containing nanometer-sized bubbles in which carbon dioxide is enclosed in a solution that dissolves at a saturated concentration (hereinafter “dissolved”), and use this culture solution as a protozoan or freshwater belonging to Euglena And a carbon dioxide fixing method and a system thereof for supplying a culture tank for algae (especially floating microalgae) inhabiting in seawater.

  The protozoa belonging to Euglena which can be preferably used in the present invention include known Euglena gracilis strains, Euglena gracilis Krebs strains, Euglena gracilis var bacillaris strains, etc. These mutation types and genetic recombination types are available, but are not limited to these.

  In addition, the algae that can be suitably used in the present invention include known brown algae such as kelp, wakame, hijiki and mozuku, red algae such as Asakusa Nori and Tengusa, and green algae such as Aoko and Aonori. Primarily underwater plants such as chlorella and spirulina are known, but are not limited to these as long as the cells contain chloroplasts.

  The culture medium used in the present invention may be photoautotrophic, photoheterotrophic, or heterotrophic. However, from the intent of the present invention to fix carbon dioxide, other than carbon from carbon gas. It is preferable to use a photoautotrophic type that does not contain a carbon source.

Specific examples of the culture solution having a carbon source include a Cramer-Myers type culture solution (Arch. Microbiol., 17 , 384-402 (1952)) and a Hutner type culture solution (Methods). Enzymol., 23 , 143-162 (1971)), Koren-Hutner type culture solution (J. Protozool., 14 , Suppl. 17 (1967)) and the like can be suitably used. . In addition, it is a matter of course that these various culture solutions diluted with natural water, tap water, seawater, or the like, or seawater or fresh water containing nutrient salts can be suitably used.

  There are various methods for dissolving carbon dioxide in the culture solution, such as a normal aeration method using an air diffuser or the like, and a method using ultrasonic waves. Carbon dioxide dissolved or dissolved in the culture solution is dissipated into the atmosphere. From the viewpoint of reducing the speed of the process as much as possible, a gas-liquid mixing method separately developed by the present inventors is preferably used.

  As the nitrogen source, known organic nitrogen sources, known inorganic nitrogen sources such as ammonium nitrate, ammonium sulfate, dibasic ammonium phosphate, ammonium hydrogen carbonate, amino acids such as glutamic acid, aspartic acid, arginine or peptone, yeast extract, corn A steebriker can be used.

  Inorganic salts added to the culture solution include known potassium, magnesium, calcium, iron, manganese, cobalt, zinc, sodium, copper, nickel and the like.

It is preferable to add and cultivate known micronutrients such as vitamin B ₁ and vitamin B ₁₂ as micronutrients, but other micronutrients may be added as necessary.

As the carbon source, carbon obtained from carbon dioxide is sufficient, but if necessary, known carbon sources such as glucose, starch hydrolyzate, molasses hydrolyzate, glutamic acid, acetic acid, ethanol, mevalonic acid, lanosterol, ergo Sterol, farnesol, geraniol, various fatty acids (C _{3 to} C ₁₈ ) and various fatty alcohols (C _{3 to} C ₁₈ ) may be added.

  Specifically, the characteristic of the method of fixing carbon dioxide gas to the above chloroplast-bearing native plants and animals is that the culture solution is taken out from these culture tanks, and a gas-liquid mixing device developed by the present inventors is added to the taken out culture solution. A carbon dioxide-dissolved culture solution prepared by dissolving carbon dioxide gas is prepared, and the prepared carbon dioxide-dissolved culture solution is circulated to a culture tank of a chloroplast-bearing native plant or animal.

  The carbon dioxide-dissolved culture solution suitably used in the present invention is composed of a liquid portion in which carbon dioxide gas is dissolved therein and a bubble portion in which carbon dioxide gas or a gas containing carbon dioxide gas is enclosed in a gaseous state. However, the presence of this bubble portion is not always essential. When this bubble part exists, the size of the bubble is the length of the chloroplast-carrying native plant and animal to be cultured (for example, in the case of Euglena, the length is 30 to 50 μm; Smaller than 100 nm, preferably less than 100 nm, more preferably about 2 to 20 nm of individual nanobubbles (bubbles having a diameter of nanometer size). . Such nanometer-sized bubbles are hereinafter referred to as nanobubbles, and the nanobubbles filled with carbon dioxide are hereinafter referred to as carbon dioxide-filled nanobubbles.

  In the case of carbon dioxide-filled nanobubbles preferably used in the present invention, the internal pressure of the nanobubbles does not exceed the liquid pressure applied in a solution containing atmospheric pressure and nanobubbles. In the culture solution containing, the dissipation of carbon dioxide-filled nanobubbles from the solution is extremely slow even when left at normal temperature and pressure. This is particularly noticeable when the particle size is about 2 to 20 nm. Therefore, even if carbon dioxide dissolved in the solution around the carbon dioxide-enclosed nanobubbles is consumed by Euglena or floating algae and the pH of the surrounding solution rises, it is included in the carbon dioxide-enclosed nanobubbles. As the carbon dioxide gas is expected to be balanced by Henry's law, the reduced amount of carbon dioxide gas is expected to be dissolved in the surrounding solution. Expected to be less.

  If the size of bubbles containing carbon dioxide exceeds about 50 nm, the rate of bubble dissipation from the solution increases, which is not preferable. However, in the present invention, a culture solution containing such large-sized carbon dioxide-containing bubbles is used. Is not to be excluded. Further, if carbon dioxide is dissolved in a predetermined concentration in the culture solution, the carbon dioxide-filled nanobubbles may not be present in the culture solution at all.

  The culture may be stationary culture as long as it is in an environment in which the carbon dioxide-dissolved culture solution is circulated, but in order to perform efficient culture, it is preferably performed while flowing, shaking or stirring. A known method can be suitably used for this flow and stirring, but when returning the circulated carbon dioxide-dissolved culture liquid to the culture tank, it is also possible to utilize the stirring effect by pressing it into the culture tank from a small nozzle. it can. Moreover, it can also press-fit through the plate etc. which were equipped with many small nozzles substantially uniformly so that a carbon dioxide-dissolved culture solution may be supplied uniformly in a culture tank.

  Cultivation of chloroplast-bearing native plants and animals may be performed under conditions of room temperature to 30 ° C., but is most preferably performed at 28 to 30 ° C. The pH of the culture solution varies depending on the composition of the culture solution, the concentration of carbon dioxide to be dissolved, and the injection amount of the carbon dioxide-dissolved culture solution. In the case of Euglena, for example, if the pH is 2.8 to 6.0 It is said that it can be cultured and exhibits particularly good growth at pH 3-5. When Euglena is used in the fixing method according to the present invention, Euglena grows even under acidic conditions in which the pH of the carbon dioxide-dissolved culture solution is 2.8, so there is no need to adjust the pH of the culture solution. However, adjusting the pH of the culture solution with alkali as desired is not completely excluded.

（出典：非特許文献２） Here, if the characteristics of Euglena are considered without restricting the technical scope of the present invention, the following is assumed. That is, as is well known, carbon dioxide is present in the solution so that there is an equilibrium between CO ₂ * (aq), HCO ₃ ⁻ and CO ₃ ^2−, and their ratio varies depending on the pH of the solution. (See the figure below).

(Source: Non-Patent Document 2)

  On the other hand, in order for protoplasts and plants possessing chloroplasts to perform carbon assimilation with chloroplasts in cells, carbon dioxide must be once taken into the cells from the outside through the cell membrane. In that case, the carbonic acid dehydrogenase on the outer surface of the cell membrane converts the surrounding hydrogen carbonate ions into carbon dioxide and then incorporates them into the cell (bicarbonate ion utilization type), without having such an enzyme There are some that are taken into the cell in the state of carbon dioxide from the surrounding (non-bicarbonate ion utilization type) (generally, a pore that can pass through a biological cell membrane if it is a nonpolar molecule such as carbon dioxide) Is known to be). Here, for example, in the case of Euglena, it is said that a high growth rate is exhibited when the pH is around 4 to 5. Therefore, in view of the above equilibrium diagram, Euglena may be a non-bicarbonate ion type. is expected. In particular, in the case of Euglena, it is expected that the presence of carbon dioxide-filled nanobubbles in the culture solution is preferable in terms of the growth environment.

  In order to fix carbon dioxide efficiently, it is preferable to always carry out the culture under light irradiation. However, in order to economically treat a large amount of carbon dioxide, a culture tank is placed outdoors and the natural state (daytime sunlight Irradiation and no irradiation at night) may be performed.

  According to the present invention, not only the carbon dioxide gas is efficiently fixed by utilizing known functions by floating algae such as protozoa and chlorella belonging to Euglena, but also the fixed organic matter as a nutrient source and a useful fatty acid. It can be used as a raw material.

  In order to separate protozoa belonging to Euglena and floating algae such as chlorella from the culture solution, ordinary solid-liquid separation methods such as precipitation, filtration or centrifugation may be used. Since microbial cells of protozoa belonging to Euglena and floating type algae such as chlorella are relatively large, they can be easily recovered by ordinary methods.

  Protozoa belonging to the isolated Euglena and floating algae such as chlorella should be dried by usual methods such as freeze drying, heat drying, sun drying, etc., and used as feed for livestock, fish, juveniles, etc. Can do. Moreover, paramylon, trehalose, highly unsaturated fatty acid, wax ester, and vitamins can be obtained by separation of cell components, and can be used in a high degree according to their characteristics.

  The carbon dioxide fixing method according to the present invention is particularly suitable for removing carbon dioxide released by the use of fossil fuels such as carbon dioxide contained in the exhaust gas of thermal power generation and carbon dioxide released during the purification of natural gas. Useful. For example, the exhaust gas of thermal power generation contains 9% carbon dioxide, but the carbon dioxide in this exhaust gas is concentrated by an appropriate method, and a culture tank for protozoa belonging to Euglena and floating algae such as chlorella The release of carbon dioxide into the atmosphere can be greatly reduced by fixing it as a useful organic substance.

  According to the method of the present invention, compared to a method in which carbon dioxide gas (or a gas containing carbon dioxide gas) is directly vented to the culture tank, culture can be performed even when high concentration carbon dioxide gas is used, and carbon dioxide gas is dissolved. It is possible to introduce the culture solution almost uniformly into the culture tank, and furthermore, by providing a system that can easily control the dissolved concentration of carbon dioxide in the culture tank, it is possible to efficiently and efficiently assimilate and fix carbon dioxide. Is possible. Furthermore, the organic substance obtained by fixing the carbon dioxide gas according to the present invention is useful for various applications.

  Next, an embodiment of the carbon dioxide fixing system according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a conceptual diagram of a carbon dioxide fixing system of this embodiment. As shown in the figure, the carbon dioxide fixing system of the present embodiment includes a carbon dioxide source 100, a carbon dioxide-dissolved culture medium preparation system 200, and a culture system 300 for floating algae such as protozoa and chlorella belonging to Euglena. It has.

  Carbon dioxide dissolved in the culture solution is supplied from the carbon dioxide source 100 to the culture solution preparation system 200 through the communication pipe 400. In this case, the carbon dioxide gas supplied may or may not be pressurized to atmospheric pressure or higher. It should be noted that when exhaust gas from a thermal power plant or the like is used as a carbon dioxide gas source, it is not a matter of course that it is necessary to remove NOx and SOx contained in the exhaust gas by a known method.

  When culturing floating algae such as protozoa and chlorella belonging to Euglena in the culture system by light-independent nutrients, carbon dioxide in the culture is consumed with growth, and the dissolved concentration of carbon dioxide decreases. The culture solution in which the dissolved concentration of carbon dioxide gas is reduced is supplied to the culture solution preparation system 200 through a culture solution communication pipe 500 that fluidly connects the culture system 300 and the culture solution preparation system 200.

  A culture solution having a reduced dissolved concentration of carbon dioxide gas supplied to the culture solution preparation system 200 through the culture solution communication pipe 500 is a Venturi tube installed in the magnetic field in the culture solution preparation system 200 as described in detail below. The gas is mixed with the carbon dioxide supplied from the carbon dioxide source 100 through the communication pipe 400 using the gas.

  The carbon dioxide-dissolved culture solution prepared so that carbon dioxide is dissolved at a predetermined concentration by the culture solution preparation system 200 passes through the carbon dioxide-dissolved culture solution communication pipe 600 that fluidly connects the culture solution preparation system 200 and the culture system 300. Supplied to the culture system 300.

  FIG. 2 is a conceptual diagram of the carbon dioxide-dissolved culture solution preparation system 200 in FIG. As shown in the figure, the culture solution preparation system 200 includes an exhaust device 210, a deaeration device 220, an ejector (or a Venturi tube) 230, a magnetism generator 240, a carbon dioxide-dissolved culture solution storage tank 250, A first pump 260 and a second pump 270 are provided and are in fluid communication with each other as shown.

  The culture solution once stored in the culture solution storage tank 250 is taken out from the culture solution storage tank 250 by the first pump 260 and is pumped through the ejector 230 provided in the magnetic generator 240.

  If the phenomenon in the ejector 230 is inferred without limiting the present invention, it will be as follows. In the process of being pumped, carbon dioxide gas (or a gas containing carbon dioxide gas) is sucked from the carbon dioxide source 100 by the aspiration action, and is passed through the ejector 230 and rapidly reduced in pressure to be sprayed or vaporized. The liquid is mixed. At this time, the carbon dioxide gas is filled around the fine droplets of the culture solution, so that the carbon dioxide gas dissolves into the individual droplets through the surface of the droplets according to Henry's law. Next, in the process in which a mixture of carbon dioxide-dissolved droplets and carbon dioxide is recombined with each other by the surface tension of the individual droplets in a magnetic field, the carbon dioxide remains as a gas and is extremely fine (on the nanometer order). Enclose in a bubble. In this way, a carbon dioxide-dissolved culture solution containing nano-sized carbon dioxide bubbles is generated in the culture solution in which carbon dioxide is dissolved.

  However, since the carbon dioxide-dissolved culture solution generated at this stage includes nano-sized carbon dioxide bubbles and huge carbon dioxide bubbles such as micron-size and millimeter-size, this is added to the deaerator 220. To remove such huge carbon dioxide bubbles.

  The carbon dioxide-dissolved culture medium from which the huge carbon dioxide bubbles have been removed in the degassing apparatus 220 is transferred again to the culture medium storage tank 250, and the characteristics of the dissolved concentration of carbon dioxide and the particle size distribution of carbon dioxide nanobubbles. The above steps are repeated until becomes a predetermined value.

  It should be noted here that, as described below, in the system of the present invention, the dissolved concentration of carbon dioxide gas automatically reaches an equilibrium after a predetermined processing time has elapsed. As long as the ratio of carbon dioxide contained in the gas to be controlled is controlled, the dissolution behavior according to the partial pressure of carbon dioxide is exhibited according to Henry's law. Is to be dissolved. Thus, the carbon dioxide-dissolved culture solution preparation system 200 does not need to be equipped with a carbon dioxide-dissolved concentration meter, and has an advantage that the system is simple.

  The dissolved concentration of carbon dioxide is, for example, the repetition time when the supply rate of the culture liquid fed through the ejector 230 is 6 liters / minute and gas of almost 100% carbon dioxide is mixed by 4 liters / minute. Reaches equilibrium in 160 to 180 minutes. FIG. 3 shows the carbon dioxide dissolved concentration (vertical axis) and treatment time (horizontal axis) when carbon dioxide is gas-liquid mixed with pure water obtained by treatment with an 18MΩ ion-exchange pure water device manufactured by Organo. ). The total amount of water at this time was 180 liters, and the carbon dioxide dissolved concentration was measured by a fixed method using sodium hydroxide.

  Moreover, the particle size obtained by measuring the size of the carbon dioxide-filled nanobubbles contained in the carbon dioxide-dissolved water reaching the equilibrium state with a dynamic light scattering particle size distribution analyzer (LB-550) manufactured by HORIBA, Ltd. The distribution result is shown in FIG. In the figure, the vertical axis represents frequency (%) and the horizontal axis represents particle diameter (nm) on a logarithmic axis. As shown in the figure, it can be understood that most of carbon dioxide-filled nanobubbles exist in a size range of 2 to 20 nm.

  One of the merits of making carbon dioxide encapsulated bubbles into such nanometer size is that the effect of buoyancy is virtually eliminated, and as a result, carbon dioxide encapsulated nanobubbles do not dissipate from the liquid, or Even if it is dissipated, it becomes a very small amount. This means that in the case of a culture solution containing carbon dioxide nanobubbles and simultaneously dissolving carbon dioxide in the liquid, the carbon dioxide dissolved in the solution is consumed by Euglena and floating algae. Even if the pH of the surrounding solution rises, it is expected that the carbon dioxide contained in the carbon dioxide-containing nanobubbles will be dissolved as much as the carbon dioxide contained in the carbon dioxide is reduced by trying to maintain equilibrium according to Henry's law. Therefore, it is expected that the variation in pH of the culture solution in which carbon dioxide gas is dissolved is also reduced.

  The carbon dioxide-dissolved culture solution adjusted in the carbon dioxide-dissolved culture solution preparation system 200 to have a predetermined carbon dioxide-dissolved concentration is then supplied to the culture system 300 through the carbon dioxide-dissolved culture fluid communication pipe 600. .

  When the Euglena is taken as an example, the supply amount of the carbon dioxide-dissolved culture solution in the case of culturing by light-independent nutrition is said to be about 3 g to 14 g of carbon dioxide fixed as paramine in Euglena with a dry weight of 20 g. It is suitably selected according to

  In the present invention, it is based on using a carbon dioxide-dissolved culture solution in which the carbon dioxide-dissolved concentration becomes a saturated concentration at 20 ° C. atmospheric pressure. When the flow rate required for stirring floating algae is not reached, the carbon dioxide dissolved culture broth preparation system is reduced by reducing the ratio of carbon dioxide in the carbon dioxide-containing gas supplied to the carbon dioxide dissolved broth preparation system 200. The carbon dioxide concentration in the carbon dioxide-dissolved culture solution prepared by 200 can be reduced, while the supply amount can be appropriately increased so that the total amount of carbon dioxide supplied is the same.

  Further, depending on the type of microorganism to be cultured, oxygen may be required together with carbon dioxide gas. In such a case, an oxygen-dissolved culture solution preparation system having the same mechanism as the carbon dioxide-dissolved culture solution preparation system 200 is used. Further additions are possible. Further, by using a gas containing carbon dioxide and oxygen in a predetermined ratio as a carbon dioxide source, it is possible to obtain a culture solution having a dissolved concentration corresponding to each partial pressure.

  FIG. 5 is a conceptual diagram of a culture system 300 according to the present invention. As shown in the figure, the culture system 300 includes a culture increment 310, a supply culture medium dispersion means 320, a heater 360 (optional), a rotary screen 330, and a light source 340 (in the case of indoor culture). .

  The culture tank 310 may be installed outdoors or indoors. In the case of outdoors, for example, it is installed on land or at sea.

  The colony density of protoplasts and plants that possess chloroplasts such as Euglena cultured in the culture tank 310 is not particularly limited, but the protoplasts and plants that possess chloroplasts grow by consuming the supplied carbon dioxide gas, so that they were grown for a predetermined period. It is preferable to remove the cell from the culture vessel 310 later and keep it at an optimal density as appropriate.

  The carbon dioxide-dissolved culture solution prepared by the carbon dioxide-dissolved culture solution preparation system 200 is supplied to the culture tank 310 through the fluid communication pipe 600 and the supply culture solution dispersion means 320.

  Since the supply culture liquid dispersion means 320 has a very slow diffusion rate of carbon dioxide gas or hydrogen carbonate ions in the liquid, carbon dioxide gas is supplied to the microorganisms such as Euglena in the culture tank 310 as uniformly as possible. The effect of stirring the inside of the culture tank 310 by utilizing the turbulent flow generated when the carbon dioxide-dissolved culture solution is injected is also expected, but it is not essential in the present invention.

  The culture vessel 310 may be provided with a heater 360 around it, but this heater 360 is not essential.

  The rotary screen 330 extracts the chloroplast-bearing native plant and animal from the culture vessel 310, separates the chloroplast-bearing native plant and animal from the culture solution, and returns the separated chloroplast-bearing native plant and animal to the culture vessel 310. In this case, the medium is returned through 350 and only the culture solution is supplied to the carbon dioxide-dissolved culture solution preparation system 200 through the fluid communication pipe 500.

  When culturing indoors, the light source 340 can be preferably a light source from an illumination having a red, green, and blue LED group, or a light source from an illumination having a white LED group. Moreover, you may make it irradiate and guide outdoor sunlight in the culture tank 310 with an optical fiber. This makes it possible to culture protoplasts and plants that possess chloroplasts even indoors.

  When culturing indoors using LED, a photodetector 710 (not shown) is installed at the bottom of the culture vessel 310, and the signal from the photodetector 710 is shown in FIG. The output may be output to the control system, and the irradiation light quantity may be adjusted by the control system of FIG.

  The control system whose conceptual diagram is shown in FIG. 6 is configured to be able to control the concentration of carbon dioxide dissolved together with the amount of irradiation light using a known technique. In this case, the dissolved carbon dioxide in the culture tank 310 Based on a signal from a concentration detector 740 (not shown in FIG. 6), the electromagnetic valve indicated by reference numeral 280 in FIG. 2 can be operated (control wiring and the like are not shown). .

  In general, the diffusion rate of gases and ions in a liquid is extremely slow. Therefore, the concentration of dissolved carbon dioxide can be accurately maintained at a desired level by directly passing carbon dioxide (or a gas containing carbon dioxide) through the culture vessel 310. In the vicinity of a bubble generated by aeration, a carbon dioxide-dissolved culture solution having a concentration equal to the partial pressure of carbon dioxide in the bubble can be obtained according to Henry's law. Since the phenomenon that the concentration does not change still occurs, it is very difficult, but in the case of the present invention, since the culture solution in which carbon dioxide gas is uniformly dissolved is introduced into the culture vessel 310, the concentration in the culture vessel 310 is dissolved. Control of the carbon dioxide concentration becomes easier.

  Although the above is the best embodiment, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and does not depart from the spirit thereof. Needless to say, various modifications are possible.

Hereinafter, the present invention will be described in more detail with reference to examples.
Euglena used : Four 15 ml culture stock solutions containing Euglena gracilis (Category No. NIES-48) were obtained from the National Institute for Environmental Studies. Hutner) 4 liters of culture medium was cultured for 7 days at each stage while increasing the volume in 3 stages. The Euglena size at this time is 30 μm to 50 μm in body length. During culture, the water temperature is maintained at 25-26 ° C. in a constant temperature water bath, irradiated with LED lamps (1700 lux or more on the surface of the Erlenmeyer flask used for the culture) for 12 hours, and then unlit for 12 hours. To prepare a Euglena culture stock solution. In both cases, air was ventilated through a suitable amount of air diffuser.

Example 1 A carbon dioxide-dissolved culture solution was prepared using the carbon dioxide-dissolved culture solution preparation system shown in FIG. The culture solution used at this time was 1.5 liters of HUT medium (but not an agar medium) at a concentration of 5% in 30 liters of pure water obtained by treatment with an 18MΩ ion exchange pure water device manufactured by Organo. In addition, it was prepared by mixing. The obtained culture solution is put into the carbon dioxide-dissolved culture solution preparation system shown in FIG. 2, and the total amount of liquid in the tank and other pipes is adjusted to a level of 30 liters. Carbon dioxide-dissolved culture solution was prepared by circulating and mixing with a magnetic action combined ejector. The carbon dioxide dissolved concentration in the carbon dioxide-dissolved culture solution thus obtained was 1670 ppm. The carbon dioxide dissolution concentration measuring device used at this time was 5000A manufactured by Shimadzu Corporation. Next, 900 ml of this carbon dioxide-dissolved culture solution was added to a glass container containing 100 ml of the above Euglena culture stock solution, and Euglena was cultured.

Comparative Example 1 1 HUT medium (excluding an agar medium) at a concentration of 5% was added to 30 liters of pure water obtained by treatment with an 18 MΩ ion exchange pure water apparatus made in the same manner as in Example 1. A culture solution that does not dissolve carbon dioxide was prepared by adding 5 liters and mixing. Euglena was cultured by adding 900 ml of this culture solution to a glass container containing 100 ml of the above Euglena culture stock solution. Next, the Euglena culture solution in the glass container is the same as the mixed carbon dioxide gas amount of Example 1 (120 liters (4 liters × 30 minutes) mixed with 30 liters of the culture solution). 1 liter of carbon dioxide gas (approximately 100% concentration) per minute was directly ventilated from the carbon dioxide cylinder through the air diffuser for 4 minutes.

Confirmation of the growth state of Euglena : A part of Euglena cultured in Example 1 and Comparative Example 1 was brought to Tokyo Industrial Technology Center Komazawa Branch, and the growth state was confirmed under a microscope. The numbers when the number in a certain small 80 frame was counted and 1000 times the number was calculated as the number in 1 ml were as follows.
Example 1: 275 × 1000 times = 275,000 (see FIG. 7)
Comparative Example 1: 8 × 1000 times = 8,000 (see FIG. 8)
In Comparative Example 1, it was confirmed that there were many debris that Euglena was thought to have broken and decomposed, and that the living Euglena hardly moved and was not healthy.

FIG. 1 is a conceptual diagram of a carbon dioxide fixing system of the present invention. FIG. 2 is a conceptual diagram of the carbon dioxide-dissolved culture medium preparation system of the present invention. FIG. 3 shows the carbon dioxide dissolved concentration (vertical axis) and treatment time (horizontal) when carbon dioxide is gas-liquid mixed with pure water obtained by treatment with an 18MΩ ion-exchange pure water apparatus manufactured by Organo using the method of the present invention. It is a graph which shows the relationship with an axis | shaft. FIG. 4 shows the size of carbon dioxide-filled nanobubbles contained in the carbon dioxide-dissolved water that has reached an equilibrium state in FIG. 3 using a dynamic light scattering particle size distribution measuring device (LB-550) manufactured by Horiba. The obtained particle size distribution results are shown. FIG. 5 is a conceptual diagram of the culture system of the present invention. FIG. 6 is a conceptual diagram of an irradiation light / carbon dioxide dissolved concentration control system that can be used in the present invention. FIG. 7 is a photomicrograph (× 1,000) showing the growth state of Euglena according to Example 1. FIG. 8 is a photomicrograph (× 1,000) showing the killed state of Euglena according to Comparative Example 1.

Explanation of symbols

100 Carbon dioxide source 200 Carbon dioxide dissolved culture preparation system 210 Exhaust device 230 Ejector 240 Magnetic generator 250 Tank 260 First pump 270 Second pump 300 Incubation system 310 Return pipe 320 Supply culture liquid dispersion means 330 Rotary screen 340 Discharge pipe 360 Heater 700 Control system 710 Light detector 720 Light control unit 730 Illumination device 740 Dissolved carbon dioxide concentration detector 750 Concentration control unit 760 Carbon dioxide dissolved culture medium

Claims (18)

In the method of fixing carbon dioxide using protoplasts and plants that possess chloroplasts,
A first step of extracting a part of the culture solution from the culture tank of the native plant and animal,
A second step of converting the extracted culture solution into a carbon dioxide gas high concentration dissolved culture solution;
And a third step of returning the carbon dioxide high concentration dissolved culture medium prepared in the conversion step to the culture tank. 2. The carbon dioxide fixing method according to claim 1, wherein the first to third steps are repeated intermittently or continuously. 3. The carbon dioxide gas high-concentration-dissolved culture medium is composed of a liquid portion that exists by dissolving at least carbon dioxide gas and nanobubbles that are present by enclosing at least carbon dioxide gas. The carbon dioxide fixing method according to claim 1. The carbon dioxide gas fixing method according to any one of claims 1 to 3, wherein the carbon dioxide gas concentration in the nanobubbles is more than 80% by volume and 100% by volume or less. The carbon dioxide fixing method according to any one of claims 1 to 4, wherein a particle size of the nanobubble is less than 1/100 of a length of the chloroplast-carrying native plant and animal. The carbon dioxide gas fixing method according to any one of claims 1 to 5, wherein a particle diameter of the nanobubble falls within a range of 2 nm to 20 nm. The carbon dioxide fixing method according to any one of claims 1 to 6, wherein the carbon dioxide is carbon dioxide generated by using fossil fuel.   The carbon dioxide fixing method according to any one of claims 1 to 6, wherein the carbon source during growth of the chloroplast-bearing native plant and animal in the culture solution is the carbon dioxide gas. The carbon dioxide fixation method according to any one of claims 1 to 7, further comprising a step of automatically controlling the concentration of carbon dioxide dissolved in the culture solution and / or the light intensity for photosynthesis of the native plant and animal as an option. . In a system that fixes carbon dioxide using protoplasts and plants that possess chloroplasts,
A carbon dioxide source supplying at least carbon dioxide;
A culture system having at least a culture solution for culturing a chloroplast-bearing native plant and animal,
A carbon dioxide-dissolved culture solution preparation system for preparing a carbon dioxide-dissolved culture solution from a gas containing at least carbon dioxide supplied from the carbon dioxide source and the culture solution,
The carbon dioxide source and the carbon dioxide dissolved culture preparation system are in fluid communication;
A carbon dioxide fixing system, wherein the culture system and the carbon dioxide dissolved medium preparation system are in fluid communication. Fluid communication between the culture system and the carbon dioxide-dissolved culture medium preparation system is provided by two communication pipes,
One of the two communication pipes is provided with a first pump for extracting a part of the culture solution from the culture system,
The other of the two communication pipes is provided with a second pump for returning the carbon dioxide-dissolved culture solution prepared by the carbon dioxide-dissolved culture solution preparation system to the culture system.
10. The carbon dioxide gas fixing system according to claim 9, further comprising a separating means for separating the chloroplast-bearing native plant and animal and the culture solution in the culture system between the first pump and the culture system. . The carbon dioxide gas according to any one of claims 9 to 10, further comprising, as an option, automatic control means for automatically controlling the carbon dioxide dissolved concentration in the culture solution and / or the light intensity for photosynthesis of the native plant and animal. Fixing system. The carbon dioxide fixing system according to any one of claims 9 to 11, wherein the carbon dioxide-dissolved culture medium preparation system includes an ejector disposed at least in a magnetic field. The carbon dioxide-dissolved culture solution preparation system prepares a carbon dioxide-dissolved culture solution composed of a liquid portion that is present by dissolving at least carbon dioxide and nanobubbles that are present by enclosing a gas containing at least carbon dioxide. The carbon dioxide fixing system according to claim 12, wherein 14. The carbon dioxide fixing system according to claim 13, wherein the concentration of carbon dioxide in the gas enclosed in the nanobubbles is more than 80% by volume and not more than 100% by volume. The carbon dioxide gas fixing system according to any one of claims 13 to 14, wherein a particle size of the nanobubble is less than 1/100 of a length of the chloroplast-bearing native plant and animal. The carbon dioxide gas fixing system according to any one of claims 13 to 15, wherein a particle diameter of the nanobubble falls within a range of 2 nm to 20 nm. The carbon dioxide fixing system according to any one of claims 9 to 16, wherein the carbon dioxide is carbon dioxide generated by using fossil fuel.

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