JP6945852B2 - Culture container for photosynthetic microorganisms - Google Patents

Description

The present invention relates to a culture vessel, and more particularly to a culture vessel suitable for culturing photosynthetic microorganisms.

In recent years, expectations have been gathered for biomass production using photosynthetic microorganisms such as microalgae and cyanobacteria, and there is a strong demand for industrialization of photosynthetic microorganism culture using a photobioreactor.

Here, what is expected is a closed-type photobioreactor that is resistant to pollution (for example, Patent Document 1), but since photosynthetic microorganisms produce oxygen by photosynthesis, the closed-type photobioreactor is expected. As the microorganisms grow, the dissolved oxygen concentration in the culture solution rises, and if left untreated, photosynthesis is inhibited and the microorganisms die.

Therefore, in the conventional closed optical bioreactor, the culture solution had to be aerated frequently in order to remove the dissolved oxygen, and the cost of this aeration is one of the causes that reduce the profitability of the business. It was one.

Japanese Unexamined Patent Publication No. 2016-220697

The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide a culture vessel for photosynthetic microorganisms capable of suppressing an increase in the concentration of dissolved oxygen while reducing aeration costs.

As a result of diligent studies on a culture vessel for photosynthetic microorganisms capable of suppressing an increase in the concentration of dissolved oxygen while reducing the aeration cost, the present inventor came up with the following configuration and arrived at the present invention.

That is, according to the present invention, it is a thin bag-shaped container having a first surface and a second surface facing each other, the first surface uniformly having light transmission, and the second surface. Provided is a culture vessel for photosynthetic microorganisms, characterized in that the surface is a porous sheet having uniformly light reflectivity and uniformly gas permeability.

As described above, according to the present invention, there is provided a culture vessel for photosynthetic microorganisms capable of suppressing an increase in the concentration of dissolved oxygen while reducing aeration costs.

The schematic diagram which shows the culture container for a photosynthetic microorganism of 1st Embodiment. The schematic diagram which shows the modification of the culture container for a photosynthetic microorganism of 1st Embodiment. The schematic diagram which shows the culture container for a photosynthetic microorganism of 2nd Embodiment. The schematic diagram which shows the experimental apparatus. A graph showing the experimental results.

Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings, but the present invention is not limited to the embodiments shown in the drawings. In each of the figures referred to below, the same reference numerals are used for common elements, and the description thereof will be omitted as appropriate.

(First Embodiment)
FIG. 1 is a schematic view showing a state in which a culture solution is sealed in a culture container 10 for a photosynthetic microorganism according to the first embodiment of the present invention, FIG. 1 (a) shows the front surface, and FIG. 1 (b) shows the rear surface. 1 (c) shows a side cross section.

As shown in FIG. 1, the culture container 10 for photosynthetic microorganisms (hereinafter referred to as culture container 10) of the present embodiment is a rectangular thin bag-shaped container, and has an envelope-shaped container shape. The culture vessel 10 of the present embodiment has two flexible surfaces 12 and 14 facing each other, the surface 12 has uniform light transmission, and the surface 14 has uniform gas permeability. Have.

In this embodiment, the surface 12 is made of a light transmissive sheet material. Here, examples of the light-transmitting sheet material include a colorless and transparent sheet material formed of a synthetic resin such as polyethylene, polypropylene, polycarbonate, and polyethylene terephthalate.

On the other hand, the surface 14 is made of a waterproof gas permeable sheet material. Here, waterproof as the gas permeable sheet material, polyethylene, polypropylene, polycarbonate, porous sheet and which is formed in such a synthetic resin as polyethylene terephthalate, a gas permeable high nonporous sheet formed of such silicon cone In addition, a composite material in which these gas permeable sheets are reinforced with a breathable sheet can be mentioned. The pore size of the above-mentioned porous sheet is preferably in the range of 0.02 μm to 0.3 μm. Further, examples of the breathable sheet for reinforcement include non-woven fabrics and woven fabrics made of synthetic resin.

In addition, in the present embodiment, the facing surfaces 12, 14 are line segments 16a, 16b, 16c having a length less than the width of the container extending in the width direction of the container with either the left or right side end of the container as an end. In this way, a flow path meandering in the width direction of the container is formed.

In the optical bioretractor using the culture vessel 10 of the present embodiment, the culture vessel 10 containing the culture solution of a photosynthetic microorganism (hereinafter, may be referred to as a microorganism) is suspended from the support column 18 from the light-transmitting surface 12. Place the light source in an appropriate position so that the light is incident. At the time of culturing, it is preferable to equalize the density of nutrients and microorganisms by connecting both ends of the meandering flow path formed in the container with a pump and circulating the culture solution.

Microorganisms in the culture solution photosynthesize using light from a light source that reaches through the light-transmitting surface 12 and carbon dioxide (CO ₂ ) dissolved in the culture solution to generate oxygen (O ₂ ). Proliferate while producing. Here, when the dissolved oxygen concentration of the culture solution exceeds the threshold value with the growth of microorganisms, photosynthesis is inhibited, but in the present embodiment, when an oxygen concentration gradient occurs with the gas permeable surface 14 as a boundary. Then, since the dissolved oxygen (O ₂ ) in the culture solution permeates the surface 14 and is released into the atmosphere, the increase in the concentration of the dissolved oxygen is automatically suppressed.

Carbon dioxide dissolved in the culture solution is consumed as the microorganisms grow, but in the present embodiment, when a carbon dioxide concentration gradient is generated with the gas permeable surface 14 as a boundary, the carbon dioxide is in the atmosphere. Carbon dioxide (CO ₂ ) permeates the surface 14 and dissolves in the culture solution, and is used for photosynthesis. In addition, if necessary, additional means for supplying carbon dioxide directly to the culture solution may be provided.

In addition, it has been reported in previous studies that the shorter the length of the optical path of light passing through the culture container, the higher the area yield. The culture container 10 of the present embodiment is configured as a thin bag container. Therefore, the length OP of the optical path of the light passing through the container is inevitably shortened, so that a high area yield can be expected. In this regard, in the present embodiment, the thickness of the culture vessel 10 in the state of being filled with the culture solution, the average value of the length OP of the optical path of the light passing through the vessel is preferably 20 mm or less, more preferably 13 mm. Design as follows.

In addition, in the present embodiment, the surface 14 is preferably configured to have uniform light reflectivity. When the surface 14 has light reflectivity, the light transmitted through the surface 12 is reflected on the surface 14, so that the microorganisms in the culture solution perform photosynthesis using both the direct light from the light source and the reflected light. As a result, the utilization efficiency of light energy is improved. Here, when the surface 14 is the above-mentioned porous sheet, the porous sheet generally has a high light reflectance, so that the automatic suppression of the dissolved oxygen concentration and the improvement of the light energy utilization efficiency can be realized at the same time. Become.

As described above, in the optical bioretractor using the culture vessel 10 of the present embodiment, excess dissolved oxygen in the culture solution is automatically released to the outside of the system through the gas permeable surface 14. Therefore, it is not necessary to continuously aerate in order to remove the dissolved oxygen, and the cost is reduced accordingly. However, this embodiment does not exclude the intermittent aeration for the purpose of preventing the sedimentation and adhesion of microorganisms. In addition, since the culture vessel 10 of the present embodiment can be formed of an inexpensive synthetic resin sheet, it can be supplied as a disposable product due to a low price.

In this embodiment, the following modifications are possible.

FIG. 2A is a schematic view showing a modified example of the culture vessel 10 described above. In the modified example shown in FIG. 2A, the gas permeable surface 14 of the culture vessel 10 is covered with the gas permeable surface 15 (sheet material formed of the gas permeable synthetic resin), and the surface is covered. A gas flow path V in contact with the surface 14 is formed by joining the two so as to form a gap between the surface 14 and the surface 15. In an optical bioreactor using this modification, if the combustion gas discharged from an arbitrary combustion system is configured to be introduced into the gas flow path V, dissolved oxygen can be removed and carbon dioxide emissions can be reduced at the same time. Will be done.

In this modified example, in addition to the mode in which the culture container 10 is suspended from the support column 18 as shown in FIG. 2 (a), the culture container 10 is placed with the surface 15 facing down as shown in FIG. 2 (b). It can also be left on the water. In this case, the culture solution in the culture vessel 10 can be cooled with water, and the culture solution can be kept at an appropriate temperature by appropriately adjusting the water temperature.

(Second Embodiment)
FIG. 3 is a schematic view showing a state in which a culture solution is sealed in a culture container 20 for photosynthetic microorganisms (hereinafter referred to as a culture container 20) according to a second embodiment of the present invention, and FIG. 3 (a) shows a side cross section. 3 (b) shows the upper surface, and FIG. 3 (c) shows an enlarged view of the side cross section.

As shown in FIGS. 3 (a) and 3 (b), the culture container 20 of the present embodiment is a container having an air mat-like shape, and has a plurality of flexible tube-like shapes arranged in parallel at predetermined intervals. The container 22 and two adjacent tubular containers 22 are connected in the longitudinal direction thereof, and are composed of a plurality of flexible tubular gas flow paths 26 arranged between the two tubular containers 22. ..

In the present embodiment, the tubular container 22 functions as a container for filling the culture solution, and the outer surface thereof is formed of the same light-transmitting sheet material as in the first embodiment, and is uniformly light-transmitting. have. On the other hand, the outer surface of the tubular gas flow path 26 is made of a gas-impermeable sheet material.

On the other hand, the vertically long boundary surface 24 connecting the tubular container 22 and the tubular gas flow path 26 is formed of the same waterproof gas permeable sheet material as in the first embodiment, and is uniformly gas permeable. have. As a result, as shown in FIG. 3C, the dissolved oxygen (O ₂ ) in the culture solution in the tubular container 22 permeates the gas-permeable interface 24 and moves toward the tubular gas flow path 26. It moves and is automatically removed, and carbon dioxide (CO ₂ ) contained in the gas flowing through the tubular gas flow path 26 permeates the boundary surface 24 and dissolves in the culture solution in the tubular container 22, and is photosynthesized. It is offered to.

In addition, in this embodiment, the interface 24 is preferably configured to have uniform light reflectivity. In this case, since a part of the light incident on the tubular container 22 is reflected on the boundary surface 24, the utilization efficiency of light energy is improved. Here, when the boundary surface 24 is the above-mentioned porous sheet, the porous sheet generally has a high light reflectance, so that the automatic suppression of the dissolved oxygen concentration and the improvement of the light energy utilization efficiency can be realized at the same time. become.

In addition, as shown in FIG. 3A, the culture vessel 20 of the present embodiment can be allowed to stand on water, and in this case, the culture solution can be kept at an appropriate temperature by adjusting the water temperature.

In addition, in an optical bioreactor using the culture vessel 20, if the combustion gas discharged from an arbitrary combustion system is configured to be introduced into the tubular gas flow path 26, dissolved oxygen can be removed and carbon dioxide emissions can be achieved. Is realized at the same time.

Although the present invention has been described above with embodiments, the present invention is not limited to the above-described embodiments, and the actions and effects of the present invention can be exhibited within the scope of other embodiments that can be conceived by those skilled in the art. As long as it works, it is included in the scope of the present invention. For example, the present invention does not preclude that the light-transmitting surfaces (surface 12, outer surface of the tubular container 22) in the above-described embodiment have gas permeability at the same time, and in the above-described embodiment. It does not exclude that the gas-transparent surfaces (surface 14, boundary surface 34) have light transmission at the same time.

Hereinafter, the culture vessel for photosynthetic microorganisms of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples described later.

A culture experiment was carried out using the experimental apparatus shown in FIG. As shown in FIG. 4, the present experimental apparatus includes a culture vessel 50 for photosynthetic microorganisms of the present invention (hereinafter referred to as a culture vessel 50), a centrifugal pump 60 for circulating the culture solution filled in the culture vessel 50, and a centrifuge pump 60. The purpose is to supply a new medium to the culture vessel 50, and to prevent the settling and sticking of microalgae with a fixed quantity liquid feed pump 70 (peristaltic pump) for collecting the culture solution overflowing from the culture vessel 50. It is configured to include an air pump 80 for performing the air exposure.

In this experiment, the air compressor 80 is driven to perform aeration once every 20 minutes (drive for 1 minute, stop for 19 minutes), and once every 20 minutes (drive for 12 seconds immediately after aeration, 19 minutes). The centrifugal pump 60 was driven at (stopped for 48 seconds) to generate circulation in the tank. At the same time, in this experiment, the quantitative liquid feed pump 70 was driven and controlled so that ^{the culture solution recovery rate was about 0.950 L d -1 and the hydraulic residence time was about 2 days.}

The culture vessel 50 of the present invention includes a porous film (3M, microporous film, thickness: 38 μm, air permeability: 210 sec / 100 cc) having excellent waterproofness and gas permeability, and a light-transmitting OPP film (Toyobo). Manufactured by P8128, single-sided heat-sealing property, thickness: 50 μm), the four sides were adhered by heat welding, and then Tetron ghost (polyester woven fabric) was applied to the porous film side to reinforce the film.

In this experiment, the four sides of the culture vessel 50 of the present invention were fixed to a metal flat bar, and a metal baffle plate 52 was placed on the OPP film to fix the culture medium to form a flow path for the culture solution. In this experiment, LED lighting (not shown) was placed in front of the culture vessel 50 (on the OPP film side) as a light source. In this state, the effective area of the culture container 50 (the area of the portion where the light is irradiated) is 0.165 m ^2, the volume is about 1.9 L, the average thickness is about 12 mm, a specific surface area of about 87 m ^- It was ^1.

In this experiment, as an example, microalgae (A. platensis) were cultured for 15 days using the experimental apparatus shown in FIG. 4, and the biomass (A) contained in 1 liter of the collected culture solution was collected every day. The dry weight of .platensis) was measured. In the 15-day culture period, the light source was controlled so that the average photon flux density of the light incident on the culture vessel 50 was 150 μmol m ^-2 s ^{-1 from the first day to the sixth day, and from the seventh day.} Until the 15th day, the light source was controlled so that the average photon flux density of the light incident on the culture vessel 50 was 315 μmol m ^-2 s ^-1 (about one-fifth of sunlight).

At the same time, in this experiment, as a comparative example, a polypropylene culture container having the same shape and size as the culture container 50 of the example was prepared, and on one side thereof, the above-mentioned porous film (3M, microporous film) was used. The same light reflection characteristics were imparted. In the comparative example, instead of the culture vessel 50 (gas permeable) of the example, the culture vessel of the comparative example (gas permeable) was set in the experimental apparatus shown in FIG. 4, and microalgae were set under the same conditions as in the example. (A. platensis) was cultured for 15 days, and the dry weight of the biomass (A. platensis) contained in 1 liter of the collected culture solution was measured every day.

FIG. 5 is a graph showing the time-series changes in the measured amount of biomass. As shown in FIG. 5, from the start of the culture to the 6th day, the biomass amounts of the examples and the comparative examples gradually increased in almost the same manner. After that, due to the effect of increasing the amount of light, the amount of biomass in the examples and the comparative examples increased rapidly from the 7th day to the 9th day in almost the same manner. After that, from the 10th day to the 15th day, the increase in the biomass amount of the comparative example stopped due to the inhibition of dissolved oxygen, while the biomass amount of the example continued to increase, and the amount was 1 of the comparative example at the maximum. It increased by 0.6 times. As described above, in the examples, although the aeration is performed only once every 20 minutes (1 minute), the dissolved oxygen inhibition is preferably avoided, and the conventional method requiring continuous aeration. It was shown that the aeration cost can be reduced to at least 1/20.

10 ... Culture container for photosynthetic microorganisms, 12, 14, 15 ... Surface, 16a, 16b, 16c ... Lines, 18 ... Struts, 20 ... Culture container for photosynthetic microorganisms, 22 ... Tube-shaped container, 24 ... Boundary surface, 26 ... Tubular gas flow path, 50 ... culture vessel for photosynthetic microorganisms, 52 ... baffle plate, 60 ... centrifugal pump, 70 ... fixed quantity liquid feed pump, 80 ... air compressor

Claims (4)

A thin bag-shaped container having a first surface and a second surface facing each other.
The first surface is uniformly light-transmitting, and the second surface is a porous sheet having uniformly light-reflecting property and uniformly gas-transmitting property.
Culture container for photosynthetic microorganisms. A meandering flow path is formed by joining the first surface and the second surface at a plurality of line segments extending in the width direction of the container.
The culture container for photosynthetic microorganisms according to claim 1. A gas flow path in contact with the second surface is formed.
The culture container for photosynthetic microorganisms according to claim 1 or 2. It consists of a plurality of tubing containers in parallel and a plurality of tubing gas flow paths arranged between two adjacent tubing containers.
The outer surface of the tubular container is uniformly light-transmitting, and the boundary surface connecting the tubular container and the tubular gas flow path is uniformly gas-transmitting.
Culture container for photosynthetic microorganisms.

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