Method for manufacturing artificial pond for cultivating halophilic microalgae and artificial pond

Abstract

The problem of the present invention is to provide a method for manufacturing an artificial pond, an artificial pond manufactured by the manufacturing method, a halophilic microalgae production method utilizing the artificial pond, and a method for producing useful organic substances therefrom, the artificial pond manufacturing method being capable of manufacturing an artificial pond suitable for culturing halophilic microalgae without using petroleum products, artificial products, solidification agents, and the like and achieving cost reduction, ease of manufacture, and large-scale cultivation without causing pollution. The problem has been solved by: a method for manufacturing an artificial pond for culturing halophilic microalgae and for storing at least the halophilic microalgae and seawater or artificial seawater, wherein a water impermeable structure is provided on the side face and / or bottom face of the artificial pond by pressing a particle group containing bentonite powder; an artificial pond manufactured by using said manufacturing method, wherein the water impermeable structure is formed on the side face and / or bottom face in a state where the water impermeable structure has absorbed water; a halophilic microalgae production method for culturing halophilic microalgae in the artificial pond; and a method for producing useful organic substances, wherein the useful organic substances are obtained from the produced halophilic microalgae.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an artificial pond for culturing halophilic microalgae. More specifically, the present invention relates to a method for manufacturing an artificial pond for culturing halophilic microalgae, in which a water-impermeable structure is provided on the bottom surface and side surfaces of the artificial pond using a mixed particle group having a specific composition, an artificial pond manufactured by the manufacturing method, and a method for producing halophilic microalgae cultured in the artificial pond.

Background Art

[0002] Although it is required to meet a large part of the energy demand with renewable energy such as solar energy and wind energy, renewable energy has a low energy density, and a rapid conversion from fossil energy has a high hurdle. Therefore, in order to lower the hurdle by fuel oil production using microalgae, the idea of "fuel oil production using microalgae" has been proposed (for example, Patent Documents 1 and 2). However, in view of the current situation, many problems including culturing methods, enjoying scale merits, and costs have not been solved regarding practical application.

[0003] In addition, it has also been proposed to obtain useful organic substances from cultured and grown microalgae, and specific studies have been made on various useful substances such as sugars, polypeptides, and vitamins (for example, Patent Documents 3 and 4). Patent Document 3 describes a method for producing a polysaccharide by culturing halophilic cyanobacteria at a high salt concentration until the stationary phase and then culturing at a low salt concentration for several hours to several days, and separating and purifying the polysaccharide. Patent Document 4 describes a method for solvent-extracting β-carotene from an aqueous algal biomass suspension. However, many problems including culturing methods, enjoying scale merits, and cost problems have not been solved.

[0004] On the other hand, a waterproof sheet using bentonite is known. Patent Document 5 describes a waterproof sheet in which granular micropieces of clay such as bentonite are adhered to a sheet of high-density polyethylene or the like with an adhesive such as polyisobutylene or butyl acrylate. Patent Document 6 describes a waterproof sheet formed by applying a bentonite elastomer obtained by kneading bentonite with water to the back surface of a "sheet material such as a vinyl chloride sheet" to which a fiber aggregate is fixed.

[0005] However, these are sheets used for waterproofing in the field of civil engineering, and the materials of these sheets used in large quantities are petroleum-derived polymers, which deviate from the idea of meeting energy demand with renewable energy.

[0006] As a technique that uses bentonite but does not use it in the form of a sheet, Patent Document 7 describes a "method for forming a water stop film in a concave surface of an excavation pond" in which a mixture obtained by adding an inorganic substance such as bentonite to an emulsion of synthetic rubber or synthetic resin is permeated to a predetermined depth into the concave surface of the excavation pond.

[0007] Patent Document 8 describes a waterproofing method in a ground waterproofing method in which a solidifying material such as cement and bentonite are sprayed on the ground almost simultaneously, and then the target soil of the ground, bentonite, and the solidifying material are mixed to form a waterproof layer. Patent Document 9 describes an artificial greening method in which a mixed soil layer of bentonite and in-situ generated soil is provided on the inner surface of a recess of an artificial waterway, a crushed stone layer is provided thereon, and a waterproof mortar is provided on the crushed stone layer.

[0008] However, these technologies are technologies used for "waterproofing in the field of civil engineering", and are not inventions that are aware of being particularly suitable for culturing halophilic microalgae. In addition, they involve adding an emulsion of synthetic rubber or synthetic resin, adding a solidifying agent such as cement, further providing a crushed stone layer thereon, or providing a waterproof mortar.

[0009] Whether it is "fuel oil production by microalgae" or "production of useful organic substances using microalgae", cost reduction is essential for practical application. In particular, in order to achieve cost reduction by taking advantage of scale merits, it is extremely important to use an extremely large artificial pond as a culture tank. However, there was no artificial pond suitable for culturing halophilic microalgae.

[0010] Regarding "obtaining fuel oil contained in microalgae" as an alternative to petroleum and natural gas, for example, large-scale culturing of microalgae has not been suitably achieved; the amount of energy required for consumption is large; etc. It is still not sufficient in terms of cost and efficiency, and further improvement is required. Also, regarding "obtaining useful organic substances from microalgae", further improvement is required in terms of cost (efficiency), etc., such as elimination of contamination by synthetic substances, heavy metals, trace harmful elements, etc.; large-scale culturing of microalgae.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention has been made in view of the above background art, and its problem is to solve the above problems, without using petroleum-derived products such as synthetic polymers, artificial products such as solidifying agents and flocculants, and solidifying agents such as mortar, cement, and silica, and to provide a method for manufacturing an artificial pond for culturing halophilic microalgae without various contaminations therefrom.

[0013] Also, to provide a method for manufacturing an artificial pond for culturing halophilic microalgae that satisfies performance such as cost reduction, ease of manufacture, large-scale culturing (enjoying scale merits), and no hindrance to the culturing of halophilic microalgae.

Means for Solving the Problems

[0014] As a result of intensive studies to solve the above problems, the present inventor has found that a structure (layer) obtained by pressurizing a particle group containing bentonite powder becomes suitable as the side surface and / or bottom surface of an artificial pond for culturing halophilic microalgae due to subsequent swelling by water absorption, salt precipitation, etc., and can be made inexpensively and easily, and has thus completed the present invention.

[0015] That is, the present invention is for culturing halophilic microalgae, and is a method for manufacturing an artificial pond for containing at least the halophilic microalgae and seawater or artificial seawater, characterized in that a water-impermeable structure is provided by pressurizing a particle group containing bentonite powder on the side surface and / or bottom surface of the artificial pond.

[0016] Also, the present invention is for culturing halophilic microalgae, and is a method for manufacturing an artificial pond for containing at least the halophilic microalgae and seawater or artificial seawater, and provides the above method for manufacturing an artificial pond, wherein a water-impermeable structure is provided by pressurizing a mixed particle group containing bentonite powder and sand on the side surface and / or bottom surface of the artificial pond.

[0017] Further, the present invention provides a method for manufacturing an artificial pond, which comprises manufacturing an artificial pond at a place that is originally sandy soil, adding bentonite from the outside to the sand constituting the sandy soil and mixing them to obtain the mixed particle group, and pressing the mixed particle group to provide a water-impermeable structure.

[0018] Further, the present invention provides the method for manufacturing an artificial pond, wherein the seawater is deep ocean water.

[0019] Further, the present invention provides an artificial pond for culturing halophilic microalgae, which is manufactured by using the method for manufacturing an artificial pond as described above, and into which at least the halophilic microalgae and seawater or artificial seawater are put. The present invention provides an artificial pond, characterized in that the water-impermeable structure is formed in a state of absorbing water on the side surface and / or the bottom surface.

[0020] Further, the present invention provides a method for producing halophilic microalgae, which comprises putting halophilic microalgae, seawater or artificial seawater into the artificial pond as described above and culturing the halophilic microalgae.

[0021] Further, the present invention provides a method for manufacturing a useful organic substance, which comprises obtaining a useful organic substance from "halophilic microalgae produced by using the method for producing halophilic microalgae as described above".

Advantages of the Invention

[0022] According to the present invention, the above problems can be solved, and an artificial pond for culturing halophilic microalgae can be manufactured at low cost without fear of pollution by de-oiling. It does not rely on "synthetic polymers or synthetic polymer laminates" such as vinyl sheets and bentonite sheets; it does not rely on synthetic chemicals such as solidifying agents and flocculants; nor does it rely on artificial solidifying agents such as mortar, cement, concrete, and silica. Therefore, there is no concern about various types of pollution from them. According to the present invention, since artificial ponds can be manufactured using safe natural substances that are ubiquitously present on Earth, there is no risk of organic pollution or heavy metal pollution.

[0023] Also, if petroleum-derived products such as (synthetic) polymer (sheets) and (organic) flocculants are used, the purpose of obtaining fuel oil and useful organic substances through de-oiling will be negated. According to the present invention, artificial ponds can be manufactured entirely through "de-oiling", and fuel oil and useful organic substances can be obtained from halophilic microalgae through "de-oiling", thus fulfilling such a purpose.

[0024] When attempting to cultivate and grow halophilic microalgae to obtain fuel oil and useful substances from them, cost reduction becomes an extremely significant issue. According to the present invention, there are effects such as the ease of manufacturing artificial ponds, the low cost of materials for artificial ponds, the ease of large-scale cultivation of halophilic microalgae, the ability to enjoy the scale merit due to such large-scale cultivation, and the possibility of cost reduction thereby. In particular, simply by applying pressure to a particle group containing bentonite powder, preferably by applying pressure to a mixed particle group obtained by mixing bentonite powder and sand, and further with the presence and assistance of (sea) water, a perfect water-impermeable structure can be formed extremely easily.

[0025] According to the present invention, since bentonite is abundant on Earth, for example, if an artificial pond is manufactured at a place where bentonite can be mined, further cost reduction is possible. Conversely, if a sandy area is used as the installation location and bentonite is added to the sand in the sandy area to manufacture an artificial pond, further cost reduction is possible. In the present invention, it is preferable to culture halophilic microalgae in "seawater, deep seawater, or artificial seawater whose components are adjusted, etc.". In this case, the installation location of the artificial pond is preferably near the sea. Since the area near the sea is often sandy, cost reduction can be further achieved through a synergistic effect.

[0026] The growth property of halophilic microalgae is unexpectedly higher when the water-impermeable structure is composed of "a mixed particle group containing sand and bentonite" than when it is composed of "only sand". Also, the growth property depends on the type of bentonite. Therefore, by using a type of bentonite suitable for "the halophilic microalgae to be cultured", an artificial pond with even better growth property can be manufactured.

[0027] When manufacturing an artificial pond in the desert, the sand of the desert can be used as the sand of the water-impermeable structure. However, when the sand contains a large amount of silica sand (SiO2), the introduced seawater will permeate underground and it is difficult to store. In that case, if bentonite is mixed with the desert sand, an artificial pond with low water permeability can be manufactured.

[0028] With various contaminations, the culture of halophilic microalgae will be hindered. However, according to the present invention, the basic performance as the above-mentioned pond is achieved, and all natural products are used while avoiding the use of non-natural products. Therefore, an artificial pond suitable for culturing halophilic microalgae can be provided. Also, when producing halophilic microalgae in an artificial pond filled with seawater or artificial seawater, there is no contamination (pollution by other organisms) by "organisms that cannot survive (cannot grow) when salts at seawater concentration or higher are dissolved". From that point of view, it is preferably to culture halophilic microalgae in an artificial pond in the first place. Among them, the artificial pond in the present invention that does not use non-natural products has less pollution by either other organisms or non-natural products, and thus is more suitable for culturing halophilic microalgae.

[0029] According to the present invention, as specifically described in the examples, cost reduction and environmental conservation are achieved. Therefore, large-scale cultivation of microalgae becomes feasible, enabling the acquisition of non-petroleum energy and low-cost useful organic substances. That is, regarding the acquisition of fuel oil contained in microalgae, it is sufficient in terms of cost, efficiency, etc. Also, regarding the acquisition of useful organic substances from microalgae, it is sufficient from aspects such as the required energy consumption, the recovery rate of microalgae, cost, and efficiency.

[0030] To obtain useful organic substances and oils (fuels) from halophilic microalgae in a profitable manner, a production scale of a certain level or more is required. However, according to the present invention, from the viewpoints of cost reduction, increased acquisition efficiency of the target substance, and almost no environmental load, etc., it can suitably respond to large-scale production (matched to large-scale production).

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0032] The present invention will be described below. However, the present invention is not limited to the following specific forms and can be arbitrarily modified within the scope of the technical idea.

[0033] The method for manufacturing an artificial pond of the present invention is for culturing halophilic microalgae, and is a method for manufacturing an artificial pond for containing at least the halophilic microalgae and seawater or artificial seawater. A water-impermeable structure is provided by pressing a particle group containing bentonite powder on the side surface and / or bottom surface of the artificial pond.

[0034] <Particle group> In the present invention, a water-impermeable structure is provided on the side surface and / or bottom surface of the artificial pond by at least a particle group containing bentonite powder. <<Bentonite>> Here, "bentonite" is a general term for clays mainly composed of montmorillonite, and mainly consists of layered silicate minerals (mainly containing aluminum phyllosilicate). As cations, in addition to aluminum (Al), there are those containing sodium (Na), calcium (Ca), potassium (K), magnesium (Mg), etc. There are many types depending on these cation species. Many are formed by the alteration of volcanic ash by water. It may be acidic clay showing acidity or those showing neutral to alkaline. As the interlayer cation of montmorillonite, there are Na + , Ca 2+ , K + , Mg 2+ etc. Among bentonites, there are those containing a large amount of any of them. As the bentonite used in the present invention, it may be sodium bentonite containing a large amount of Na + and having high swelling power, or calcium bentonite containing a large amount of Ca 2+ and having low swelling power.

[0035] The bentonite used in the present invention is excellent in terms of the ease of manufacturing an artificial pond when mixed with sand, the performance of the obtained artificial pond, etc. Also, since the growth of halophilic microalgae depends on the type of bentonite, a suitable one (excellent in growth) for the halophilic microalgae to be cultured is selected. The bentonite used in the present invention is determined to be suitable mainly taking into account the above two points (properties and manufacturability of the artificial pond and growth of algae) based on suitable chemical composition (composition formula), swelling power, pH, particle size, structural viscosity (thixotropy), bulk density (apparent specific gravity), dispersibility in water (dispersion stability), etc.

[0036] The type of bentonite powder used in the present invention is not particularly limited. That is, as long as it is bentonite, there are no particular limitations on aspects such as the production area, chemical composition (cation species, etc.), ratio of main components, crystal structure (degree of crystallinity), average particle size, particle size distribution, acidity / alkalinity, etc. Low swelling power bentonite with a swelling power of 13 mL / 2 g or less, medium swelling power bentonite with a swelling power of 13 - 18 mL / 2 g, and high swelling power bentonite with a swelling power of 18 mL / 2 g or more are all preferably used. "Swelling power" is defined as the volume (mL) of water absorbed by 2 g of bentonite.

[0037] It may be artificially modified or unmodified and mined from nature. From the perspective of cost reduction, those mined from nature itself or those with only grinding applied to them are more preferable than artificially modified ones. Also, the production area is not particularly limited, such as North America, Central America, South America, Europe, China, Japan, India, Africa, etc., and bentonite from any production area can be used.

[0038] The upper limit of the volume average particle size is preferably the particle size generally referred to as "clay". Specifically, 5 μm or less is preferable, 4 μm or less is more preferable, 3 μm or less is still more preferable, and 2 μm or less is particularly preferable.

[0039] When the upper limit of the volume average particle diameter is as described above or less, there are effects such as an easy effect of volume expansion due to swelling by water. Further, when using the "particle group containing bentonite powder" as the "mixed particle group containing bentonite powder and sand" described later, since the bentonite powder is sufficiently fine, it easily enters the gaps between the sands, and the water impermeability is improved.

[0040] The bentonite used is preferably one whose swelling ratio becomes 5 times or more and 16 times or less, particularly preferably expands 7 times or more and 13 times or less, when it comes into contact with seawater. If it is such a bentonite, the swelling efficiency in the water-impermeable structure is good due to the introduction of seawater or the like, which is preferable from the viewpoints of water impermeability, workability, etc. For example, when a water-impermeable structure is provided by adjusting the bentonite to be 10% by mass with respect to the total mass of the bentonite powder and sand, the volume or thickness of the water-impermeable structure becomes approximately twice in calculation due to the introduction of seawater or the like. Even if the thickness of the water-impermeable structure does not increase due to bentonite and (artificial) seawater, when sand is used in combination, the bentonite (particles) swells and enters between the coarse sand particles, improving the water impermeability.

[0041] Commercially available products can also be preferably used. Examples of such commercially available products include the TB series such as Hota; TB-250, TB-S, TB-200, etc.; the TS series such as TS-01, etc.; Akagi; Asama; Haruna; the clay series such as Neoclay, Superclay, etc. manufactured by Tachibana Material Co., Ltd.; etc. Further, examples include the Kunigel (registered trademark) series such as Kunigel V1, Kunigel V2, Kunigel GS, etc. manufactured by Kunimine Industries Co., Ltd.; etc.

[0042] <Mixed particle group> In the present invention, it is preferable to use a "mixed particle group containing bentonite powder and sand" as the "particle group containing bentonite powder" from the viewpoint of cost reduction and the like. That is, the present invention is for culturing halophilic microalgae, and is a method for manufacturing an artificial pond for containing at least the halophilic microalgae and seawater or artificial seawater, and a water-impermeable structure is provided by pressing a mixed particle group containing bentonite powder and sand on the side surface and / or bottom surface of the artificial pond. The present invention is also a method for manufacturing the artificial pond as described above.

[0043] <<Sand>> In the present invention, it is preferable to provide a water-impermeable structure on the side surface and / or bottom surface of the artificial pond by a mixed particle group containing at least bentonite powder and sand. Here, "sand" refers to among the crushed materials, those having an average particle size of 2 mm (2000 μm) to 1 / 16 mm (62.5 μm). Very coarse sand (2 mm to 1 mm), coarse sand (1 mm to 1 / 2 mm (1000 μm to 500 μm), medium sand (1 / 2 mm to 1 / 4 mm (500 μm to 250 μm), fine sand (1 / 4 mm to 1 / 8 mm (250 μm to 125 μm), and very fine sand (1 / 8 mm to 1 / 16 mm (125 μm to 62.5 μm) may be used. Among them, particularly preferably, fine sand (1 / 4 mm to 1 / 8 mm (250 μm to 125 μm) and / or very fine sand (1 / 8 mm to 1 / 16 mm (125 μm to 62.5 μm) are used. Here, "and" also means a mixture of fine sand and very fine sand.

[0044] It may be obtained by artificially crushing rocks or the like so as to conform to the above definition. However, in order to reduce the material cost, it is preferable to use natural sand as it is. In addition, it is preferable to use the sand that originally exists at the manufacturing site of the artificial pond in order to further reduce the cost. That is, the present invention is also a method for manufacturing the artificial pond as described above, in which an artificial pond is manufactured at a place that is originally a sandy area, bentonite is added from the outside and mixed with the sand constituting the sandy area to obtain the above mixed particle group, and the mixed particle group is pressed to provide a water-impermeable structure.

[0045] In the present invention, it is preferable to use seawater, deep ocean water, or those obtained by artificially adjusting their salinity as a medium (culture solution). For obtaining them, a location close to the sea or a salt lake is preferred. Therefore, in such a location, since the ground is often sandy, the use of the sand from the sandy ground can further reduce costs due to a synergistic effect.

[0046] According to the method for manufacturing an artificial pond of the present invention, by using halophilic microalgae for the production of fuel oil and useful organic substances, a great synergistic effect can be obtained also with respect to the availability of seawater and deep ocean water used as a medium (culture solution) and sand used as a material for the water-impermeable structure.

[0047] <<Content ratio of bentonite and sand>> When using a mixed particle group of bentonite powder and sand, the mass of the bentonite powder in the above mixed particle group is not particularly limited. However, with respect to the total mass of the bentonite powder and sand in the above mixed particle group, the lower limit of the content of the bentonite powder is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, particularly preferably 6% by mass or more, and most preferably 8% by mass or more. Also, with respect to the above total mass, the upper limit of the content of the bentonite powder is preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 40% by mass or less, particularly preferably 18% by mass or less, and most preferably 15% by mass or less.

[0048] If the mass (content ratio of bentonite powder) of the bentonite powder in the above mixed particle group is too small, the water impermeability of the obtained water-impermeable structure may be poor, or sufficient volume expansion may not be expected due to water absorption. On the other hand, if the value is too large, since bentonite is more expensive than sand, the mixed particle group (as a manufacturing material) may become expensive, or the viscosity of the mixed particle group may be too high and the energy required for stirring may become excessive.

[0049] <<Other particles (powder)>> In the particle group in the present invention, in addition to the bentonite powder and the sand described above, "other particles (powder)" having a smaller particle size than sand, such as those generally referred to as soil, mud, clay, etc., may be contained. The "other particles (powder)" may be used preferably at 20% by mass or less, more preferably at 10% by mass or less, and still more preferably at 5% by mass or less based on the entire particle group. However, it is most preferable not to use the "other particles (powder)" substantially.

[0050] <Method for manufacturing artificial pond and artificial pond to be manufactured> In the manufacturing method of the present invention, it is characterized in that a water-impermeable structure is provided by pressing a mixed particle group on the side surface and / or bottom surface of the artificial pond. Here, the location serving as the basis for the manufacture of the "artificial pond" may be any of a simple flat ground in nature, a place that remains almost as it is in nature or a place that has been specially processed, modified, repaired, partitioned, reinforced, etc., or a place that has been artificially made or a place that has been artificially made and then specially processed, modified, repaired, partitioned, reinforced, etc.

[0051] Examples of the above-mentioned "simple flat ground in nature" include deserts, sandy beaches, fields, natural land, etc. Examples of the above-mentioned "thing that remains almost as it is in nature" include, for example, the sea, rivers, lakes, salt lakes, ponds, etc. Specific examples of the above-mentioned "artificially made thing" include, for example, artificial reservoirs, pools, tanks, dedicated culture containers, fields, aquaculture ponds, sightseeing ponds, etc. Fields such as fallow fields are particularly preferable because they have ridges and suitable depths.

[0052] Fig. 1 shows the process of manufacturing an artificial pond 10 for culturing halophilic microalgae 13, in which an unused field C is utilized, and a "mixed particle group containing bentonite powder and sand" is applied (for example, pasted) to the side surface (ridge B) and the bottom surface of the field C, and then pressed to provide a water-impermeable structure 11a, and seawater 12 (seawater, artificial seawater, deep ocean water) is put therein to form a water-impermeable structure 11b during culturing (Fig. 1), and a schematic cross-sectional view of the "manufactured artificial pond 10" (Fig. 1(c)).

[0053] Although the size is not limited to FIG. 1, FIG. 1 shows an example when an artificial pond (see FIG. 1(c)) is manufactured using a fallow field (see FIG. 1(a)) with a length of 10 m, a width of 10 m, and a ridge height (depth) of 30 cm. FIG. 1 is a schematic cross-sectional view of the water-impermeable structure 11a before filling with seawater 12 after pressurization (FIG. 1(b)) with a thickness of 5 cm, the water-impermeable structure 11b when the thickness did not increase after filling with seawater 12 (FIG. 1(c)), and when it swelled and increased in size (FIG. 1(d)), and the artificial pond 10. Note that although bentonite swells and penetrates between coarse particles, the volume and thickness of the water-impermeable structure 11a do not necessarily increase as large as in FIG. 1(d) described above.

[0054] The area of one artificial pond, in the case of being artificially created from the beginning, is preferably 1 m 2 or more and 1000 m 2 or less, more preferably 3 m 2 or more and 300 m 2 or less, and particularly preferably 10 m 2 or more and 100 m 2 or less. Also, when using something in nature, it is preferably 10 m 2 or more and 10000 m 2 or less, more preferably 30 m 2 or more and 3000 m 2 or less, and particularly preferably 100 m 2 or more and 1000 m 2 or less.

[0055] When the area of one artificial pond is equal to or greater than the above lower limit, effects such as scale merit can be obtained. On the other hand, when the area of one "artificial pond" is equal to or less than the above upper limit, there are effects such as not excessive capital investment, good workability, and not being overly wide and wasteful.

[0056] The volume of one artificial pond is preferably 1 m 3 or more, more preferably 3 m 3 or more and 10000 m3 is as follows, more preferably 10 m 3 or more and 3000 m 3 or less, particularly preferably 30 m 3 or more and 1000 m 3 or less. If the volume of one artificial pond is equal to or greater than the above lower limit or equal to or less than the above upper limit, it is desirable because it has the same effect as in the case of the above-mentioned area.

[0057] The average depth of the artificial pond is preferably 0.07 m or more and 1.5 m or less, more preferably 0.10 m or more and 1.2 m or less, and particularly preferably 0.12 m or more and 0.8 m or less. When it is within the above range, there are effects such as sunlight easily hitting the halophilic microalgae, no risk of drying up, and easy recovery of the halophilic microalgae.

[0058] <Construction method of water-impermeable structure> In the production method of the present invention, a water-impermeable structure is provided by pressing a particle group such as a mixed particle group onto the side surface and / or bottom surface of the artificial pond.

[0059] Before applying the particle group containing bentonite powder, it is also preferable to perform an operation of compacting the original ground. From the viewpoints that the "compacted part of the original ground" can also contribute to water impermeability and that the water-impermeable structure can be provided with a uniform thickness by pressing the particle group thereafter, the "compaction" can be carried out in the same manner as the pressing of the water-impermeable structure described later.

[0060] When applying a particle group such as a mixed particle group to the side surface and / or bottom surface of the artificial pond, it is preferable to use a dispersion medium to make it into a slurry state once and then put it in. It is also preferable to make a slurry by making only bentonite into a slurry state and then adding sand thereto. The dispersion medium is not limited and examples thereof include pure water and seawater. The amount of the dispersion medium is not particularly limited as long as a slurry with a suitable viscosity can be finally obtained, but it is preferably 1.5 times or more and 15 times or less, more preferably 2 times or more and 10 times or less, and particularly preferably 3 times or more and 7 times or less the mass of bentonite.

[0061] Here, the method of applying pressure is not particularly limited. It may be manually compacted with a hammer, a plate, etc., compacted with a roller, a grader, etc., or pressed by hitting with a rammer. It is also preferable to determine the pressure application method according to the size (scale) of the artificial pond. The degree of pressure application is not particularly limited, but it is preferably 15 kPa or more and 150 kPa or less.

[0062] The thickness of the water-impermeable structure after pressure application is determined in consideration of durability, manufacturing cost, etc., and is not particularly limited. However, before filling with seawater or artificial seawater, as an average value depending on the location of the artificial pond, it is preferably 0.5 cm or more and 25 cm or less, more preferably 1.0 cm or more and 20 cm or less, still more preferably 2 cm or more and 15 cm or less, and particularly preferably 3 cm or more and 8 cm or less.

[0063] The thickness of the water-impermeable structure may increase when filled with (artificial) seawater or deep ocean water, which is a culture solution. It is preferable to adjust the content ratio of bentonite powder so that the expansion rate of the thickness is in the range of 1.0 to 3.0 times in order to obtain water impermeability. More preferably, it is in the range of 1.1 to 2.6 times, and particularly preferably in the range of 1.2 to 2.2 times.

[0064] Therefore, the thickness of the water-impermeable structure is preferably set so that, in the steady state of culturing halophilic microalgae by filling with seawater or artificial seawater, the average value depending on the location of the artificial pond where the thickness has increased due to water absorption is 1.0 cm or more and 50 cm or less, more preferably 2 cm or more and 30 cm or less, and particularly preferably 3 cm or more and 15 cm or less.

[0065] After pressurization, if the thickness of the water-impermeable structure before introducing (artificial) seawater or deep ocean water is too small, or if the thickness in the steady state when culturing halophilic microalgae with them is too small, the water impermeability may be poor and water leakage may occur. Conversely, if it is too large, materials and construction may be wasted.

[0066] In the present invention, after forming a water-impermeable structure by pressurizing a particle group such as a mixed particle group, the provision of "other layers" thereon is not excluded. In the present invention, after providing a water-impermeable structure and before introducing seawater or artificial seawater, it is also preferable (see Example 9 and FIG. 2) to provide a soil layer by charging and compacting soil on the water-impermeable structure from the viewpoint that the water-impermeable structure can be physically (mechanically) protected. The soil of the soil layer is not particularly limited, but the soil originally present at the location where the artificial pond of the present invention is provided is preferable from the viewpoints of nature protection and production cost reduction. The "compaction" of the soil layer can be carried out in the same manner as the pressurization of the water-impermeable structure described later.

[0067] The above soil layer is not essential, but when the soil layer is provided, its thickness is preferably 1.0 cm or more and 60 cm or less, more preferably 2 cm or more and 50 cm or less, still more preferably 5 cm or more and 40 cm or less, and particularly preferably 10 cm or more and 30 cm or less.

[0068] <Raw water, culture solution, seawater, deep ocean water, artificial seawater, etc. for culturing> The artificial pond produced by the production method of the present invention is for culturing halophilic microalgae, and is for containing at least the halophilic microalgae and seawater or deep ocean water. In this specification, etc., seawater and deep ocean water may be collectively abbreviated simply as "seawater". Also, those prepared artificially from the beginning or those whose components are artificially adjusted using seawater or deep ocean water as raw materials may be collectively abbreviated simply as "artificial seawater". Therefore, "artificial seawater" includes "artificial deep ocean water".

[0069] The cultivation is carried out in artificial ponds with seawater, deep ocean water, artificial seawater, etc. That is, in the method for manufacturing an artificial pond, it is particularly preferable that the seawater is deep ocean water or artificial deep ocean water for the following reasons and the like.

[0070] Seawater has an average salt concentration of about 3.5% by mass and mainly contains cations such as sodium ions, magnesium ions, potassium ions, calcium ions, etc.; anions such as chloride ions, sulfate ions, etc.

[0071] Deep ocean water has no artificial pollution, has a low temperature so there are few miscellaneous bacteria, and has no contamination of surviving phytoplankton because it is not exposed to sunlight, etc., and suitable conditions are provided for culturing halophilic microalgae. Furthermore, in addition to these, nitrogen (N) in nitrates, etc., phosphorus (P) in phosphates, etc., silicon (Si) in silicates, etc. are abundant. Also, because the salt concentration is high, it is difficult for bacteria and the like that hinder the cultivation of halophilic microalgae to survive (there are few). Therefore, deep ocean water is particularly preferable as a culture solution for culturing halophilic microalgae in the present invention.

[0072] Seawater and / or deep ocean water can increase the concentration of nitrogen (N) source and phosphorus (P) source necessary for culturing halophilic microalgae by evaporating and concentrating water using solar heat, etc. Along with (simultaneously with) the evaporation of water, the sodium chloride concentration of seawater or deep ocean water also increases (for example, up to about 15% by mass). However, many (highly) halophilic microalgae such as microalgae belonging to the genus Dunaliella can be cultured even at a high sodium chloride concentration (for example, about 15% by mass). Also from that point, it is preferable to increase the concentration of nitrogen (N) source and phosphorus (P) source using solar heat. In addition, when the sodium chloride concentration becomes high (for example, about 15% by mass), it becomes difficult for miscellaneous bacteria to propagate and contamination decreases, which is advantageous for the growth of halophilic microalgae.

[0073] Seawater, deep ocean water, and raw water for cultivation obtained by evaporating and concentrating water using solar heat or the like are inexpensive in terms of cost and have a scale merit in the present invention, and thus are particularly suitable for taking advantage of them.

[0074] The "artificial seawater" may be prepared by artificially adding all nutrients (including essential elements, etc.) and salts (including the salinity in seawater) from the beginning, or such nutrients and salts may be artificially added and blended to natural seawater or deep ocean water for preparation.

[0075] <Halophilic microalgae> Specific examples of the halophilic microalgae in the present invention include, for example, microalgae belonging to the genus Dunaliella. One or more species of halophilic microalgae can be cultured. Among the halophilic microalgae, those so-called "highly halophilic microalgae" are particularly preferred.

[0076] By culturing halophilic microalgae in (artificial) seawater, particularly in seawater with a high salinity concentration, it becomes possible to reduce the risk of contamination (such as the intrusion of miscellaneous bacteria) at low cost.

[0077] Specific examples of the feature of using "halophilic microalgae" as the object of cultivation include, for example, the following. From halophilic microalgae, useful organic substances such as carbohydrates or sugars; oligopeptides, polypeptides or proteins; vitamins or vitamin precursors; polyhydric alcohols; oils and fats; glycolipids, phospholipids or lipoproteins; or hydrocarbons can be obtained; they can also utilize carbon sources other than carbon dioxide; there are many highly halophilic algae (marine microalgae); the adaptable growth temperature range is wide; they are not affected by strong light inhibition; etc. can be mentioned. In addition, carbon dioxide in the atmosphere can be resource-utilized by halophilic microalgae.

[0078] Among them, particularly preferred halophilic microalgae include, from the above points and others, microalgae belonging to the genus Dunaliella.

[0079] Since the genus Dunaliella does not have a cell wall, oil extraction is easy. In addition, since the genus Dunaliella stores glycerin in cells for osmotic pressure adjustment, the glycerin can be recovered and effectively utilized. Since the glycerin is pure glycerin that does not contain solvents, catalysts, etc., it has high utility value for use in cosmetics, food and beverages, and as a fermentation substrate.

[0080] In addition, the genus Dunaliella does not require bubbling (aeration of carbon dioxide), and the culture cost can be suppressed. In addition, the genus Dunaliella is one of the few microalgae that can accumulate lipids while growing.

[0081] In addition, by accumulating β-carotene, it can be cultured without causing strong light inhibition. In addition, since the adaptable growth temperature range is wide, it can be cultured without artificial temperature control, so the culture cost can be significantly reduced.

[0082] Examples of microalgae belonging to the genus Dunaliella include Dunaliella salina, Dunaliella viridis, Dunaliella bioculata, Dunaliella primolecta, Dunaliella tertiolecta, Dunaliella bardawil, etc. From the points that the viable temperature range is 4 to 60 °C and it can survive and grow at both low and high temperatures, and it can withstand high temperatures under high osmotic pressure conditions, it is particularly preferable to culture Dunaliella salina. In the present invention, one or more halophilic microalgae belonging to the genus Dunaliella can also be cultured simultaneously.

[0083] <Function and Principle> The mechanism and principle by which the "water-impermeable structure in the presence of seawater" obtained by the manufacturing method of the present invention exhibits water impermeability, and the mechanism and principle by which the artificial pond obtained in the present invention has no water leakage and can be used over a long period of time are not particularly limited, but are considered as follows. However, the present invention is not limited to the range where the following mechanism and principle apply.

[0084] It is considered that each particle of bentonite powder swells due to seawater, thereby tightly closing the gaps between adjacent bentonite powders. Further, when bentonite powder and sand are used in combination, it is considered that the gaps between one sand grain and the adjacent sand grains are tightly closed by the bentonite powder swollen by seawater. And it is considered that the seawater becomes difficult to permeate due to the densification of the entire water-impermeable structure.

[0085] In addition, the culture water put into the artificial pond has higher water impermeability with seawater than with pure water. This is considered to be because salt precipitates as extremely fine particles between the particles of sand and / or bentonite, and this further tightly closes the gaps between the particles, resulting in further improved water impermeability.

[0086] <Artificial pond> The present invention is an artificial pond for culturing halophilic microalgae, which is manufactured using the above-described manufacturing method of the artificial pond, and into which at least the halophilic microalgae and seawater or artificial seawater are put, and is characterized in that the above water-impermeable structure is formed in a state of absorbing water on the side surface and / or the bottom surface.

[0087] As described above, it is considered that the water impermeability is increased due to the swelling of bentonite by the presence of seawater. However, the chemical structure of such swollen bentonite, the shape of the bentonite powder, the way the gaps between sands are filled with bentonite, the form of the water-impermeable structure (after contacting seawater), etc. cannot be directly specified by their shapes and parameters, etc., and it is impossible or practically infeasible to perform quantitative measurements for specification.

[0088] <Method for Producing Halophilic Microalgae> The present invention is also a method for producing halophilic microalgae, which comprises putting halophilic microalgae and seawater or artificial seawater into an artificial pond produced by the above method and culturing the halophilic microalgae. The production by culturing halophilic microalgae is not particularly limited, and known methods can be used. From the viewpoint of cost reduction and the like, since the present invention is preferably carried out outdoors, it is preferable to use sunlight as the light energy for growth.

[0089] Seawater or the like (culture solution (liquid of the medium)) of halophilic microalgae is adjusted to a suitable composition in terms of contained elements and others according to the type of halophilic microalgae to be produced. The culture temperature and culture time are preferably appropriately adjusted according to the type of halophilic microalgae to be produced so that the productivity and the performance of the produced product are suitable. In order to increase the production amount and reduce the fixed cost, continuous culture is also preferable, and terrace field type continuous culture is also preferable.

[0090] The produced halophilic microalgae are recovered by a known method. The method of this recovery is not particularly limited, and examples include filtration; evaporation to dryness of water by heating, reduced pressure, air drying, etc.; centrifugation; a method of sedimentation using a flocculant or an electrode; a method of sedimentation by blocking gases such as oxygen, nitrogen, and carbon dioxide; a method of sedimentation by changing the surrounding conditions; etc. These are used singly or in combination of two or more.

[0091] <Method for Producing Useful Organic Substances> The present invention is also a method for producing useful organic substances, which is characterized by obtaining useful organic substances from halophilic microalgae produced by using the above-mentioned "method for producing halophilic microalgae". As the method for obtaining the above useful organic substances, known methods may be used, and examples include separation by squeezing, fractional distillation, various extraction methods, etc.; utilization of the residue after separation; separation after reaction; etc.

[0092] The above useful organic substances are not particularly limited as long as they are obtained from the produced halophilic microalgae, but are preferably carbohydrates or sugars; oligopeptides, polypeptides or proteins; vitamins or vitamin precursors; polyhydric alcohols; oils and fats; glycolipids, phospholipids or lipoproteins; or hydrocarbons.

[0093] Oligopeptides such as glutathione; carotenoids such as β-carotene; polyhydric alcohols such as glycerin; oils and fats such as glycerin fatty acid esters; etc. are particularly preferred examples, but are not limited thereto.

[0094] β-Carotene has a high antioxidant effect and can be used, for example, in pharmaceuticals, foods, food additives, supplements, etc. Glutathione has a high antioxidant effect and can be used, for example, in pharmaceuticals, foods, supplements, fertilizers, feeds, etc. Glycerin can be suitably used, for example, as a raw material for cosmetics, pharmaceuticals, etc., as well as a fuel. Oils and fats can be used, for example, as food oils, feed oils, fuel oils, etc. Proteins can be used, for example, as feeds, fermentation raw materials, etc.

Examples

[0095] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.

[0096] Example 1 <Comparison with Other Manufacturing Methods> The manufacturing method of the artificial pond of the present invention, the manufacturing method of the artificial pond using a vinyl chloride sheet, and the manufacturing method of the artificial pond using concrete were compared.

[0097] As shown in Table 1 below, in the method for manufacturing an artificial pond using a polymer sheet such as a vinyl chloride sheet, construction and leveling for laying the sheet are required, and since the polymer sheet is expensive, the manufacturing cost is too high.

[0098] Although bentonite sheets for water shielding in the civil engineering field are known, the bentonite sheet is obtained by previously imparting bentonite to a synthetic polymer such as polyvinyl chloride. However, this uses a synthetic polymer derived from petroleum and is expensive, and also has a large environmental impact. Compared with the concrete described below, the bentonite sheet has a lower construction cost, but in terms of the environmental impact and cost of the material (about 1000 yen / m 2 ), it cannot be used cost-effectively for culturing halophilic microalgae.

[0099] In the case of using a synthetic polymer, when it is discarded or abandoned, it is necessary to remove all the polymer sheets. If not removed, the environmental impact will increase. Especially when using a vinyl chloride sheet, environmental damage will occur, and the disposal cost will be extremely high even when discarded (Table 1).

[0100] In addition, in the method for manufacturing an artificial pond using concrete, construction and leveling for placing the concrete are required, and a long construction period is necessary. When manufacturing an artificial pond with concrete, 10,000 to 30,000 yen / m 2 is required. In addition, trace components contained in concrete (including mortar, cement, etc.) may also interfere with the culture of halophilic microalgae. Moreover, when discarded or abandoned, it is necessary to remove the concrete. If left without removal, it will take an extremely long time to weather. Also, although the environmental impact by chemical substances is small, due to the large artificial pond, the structural environmental damage will be large (Table 1).

[0101] On the other hand, in the present invention, when an artificial pond is made in a sandy area from the beginning, sand can be obtained extremely easily and there is no material cost. In addition, when using seawater as the water in the artificial pond (the water for cultivation), it is preferable that the installation (manufacturing) location is near the sea. Since sea sand exists in large quantities and is almost flat (the surface is flat), there is no need to construct land, and the cost can be further reduced. Particularly, when manufacturing in the site of a paddy field or the like (which is extremely suitable in terms of depth), there is no need to construct land, so almost no construction cost is incurred.

[0102] Moreover, according to the present invention, just by applying pressure with a roller or the like, the (artificial) seawater filled after completion swells the bentonite powder to form a water-impermeable structure body, so the manufacturing cost of the artificial pond can be suppressed extremely inexpensively. Even when compared with the case of using a polymer sheet such as the above-mentioned vinyl chloride sheet, and even when compared with the case of using the above-mentioned concrete, the manufacturing cost per unit area is lower for the manufacturing method of the present invention.

[0103] In addition, the water-impermeable structure body of the artificial pond obtained by the present invention does not cause any environmental damage even if left as it is. Moreover, since it is all made of natural substances (natural sand and clay), there is no environmental load. In the case of synthetic organic polymers, it goes without saying that there is a large environmental load if left as it is, but even for inorganic substances such as cement, an artificial selection, concentration, and separation process is involved, so there may be an unnatural concentration of trace harmful components.

[0104]

Table 1

[0105] Example 2 <Preparation of a mixed particle group containing bentonite powder and sand> Bentonite powder and sand were mixed as follows to obtain a mixed particle group. Pure water was added so that the bentonite powder became 5 mass times as a whole, and it was well stirred and dispersed to prepare a "bentonite slurry". Next, the "bentonite slurry" and sand were mixed in a container so as to have the composition shown in Table 2 below, and stirred with a stainless-steel medicine spoon until uniform. In this way, the following three types of "mixed particle groups with different ratios of bentonite powder to sand" were prepared.

[0106] [Table 2]

[0107] The obtained mixed particle groups are compacted on-site with rollers or graders, but in the laboratory, the samples were placed in a dedicated compaction tool (iron mold) and struck with a 2.5 kg rammer. However, whether pressurized using the rammer or "strongly pressed by hand using a flat plate and then dried at 35 - 40 °C", the same results were obtained regarding water permeability (impermeability). That is, after separately confirming that the same results can be obtained by the method within the above "" as by the method of compacting with dedicated devices such as rammers, rollers, and graders, the following investigations were carried out using the above method.

[0108] Example 3 <Preparation of water-impermeable structure> As follows, using a large funnel, the water impermeability of the samples of the above mixed particle groups No. 11 - 13 was determined respectively.

[0109] The outlet of the large funnel was blocked with a rubber stopper, 150 g of each of the above mixed particle groups No. 11 - 13 was put in, and the surface was uniformly compacted by hand from above the mixed particle groups using a flat plate. Thereafter, it was dried in an oven (in the atmosphere) at 35 °C for 3 hours. Some cracks were observed during the process, so the cracks were filled by further compacting by hand using the above plate.

[0110] As a result, three types (No.11, 12, 13) of water-impermeable structures with a thickness of 3.0 cm were obtained on the funnel. For the water-impermeable structure, almost the same consolidation property as that compacted with a rammer was obtained.

[0111] Example 4 <Examination of water impermeability 1 (using a funnel)> On the water-impermeable structure obtained in Example 3, 150 g of deep-sea water or artificial seawater (adjusted to 12% by mass of salts including sodium chloride) containing Dunaliella salina (hereinafter simply abbreviated as "culture solution") was poured.

[0112] The same mass (150 g) of the culture solution as the water-impermeable structure obtained by pressing the "mixed particle group composed of bentonite powder and sand" was put in and allowed to stand. When observed after one week, the water level of the culture solution that permeated through the water-impermeable structure decreased by only 2 mm. The permeability coefficient at this time was 3.3×10 -9 [m / s]. For all of the mixed particle groups No.11, 12, and 13 of Example 2, the same results as above were obtained.

[0113] Example 5 <Examination of water impermeability 2 (using a funnel)> The scale of Example 4 was doubled for examination. Specifically, 300 g of the "mixed particle group composed of bentonite powder and sand" was used, and 300 g of the "culture solution" was injected. After one week and two weeks had passed, when the dripping of water from under the funnel was confirmed, no water had dropped at all. Water permeation could not be confirmed. For all of the mixed particle groups No.11, 12, and 13 of Example 2, the same results as above were obtained.

[0114] Example 6 <Examination of water impermeability 3 (using a syringe)> In Example 4, instead of a large funnel, a large syringe was used. That is, the syringe was filled with the mixed particle groups No. 11, 12, and 13 of Example 2 and manually compacted. Specifically, 100 g of the mixed particle group (height 5.0 cm in the syringe) and 200 g of the same culture solution as in Example 4 (height 10.0 cm in the syringe) were set vertically, and after two weeks, leakage of water was observed from the bottom of the syringe.

[0115] As a result, the water-impermeable structure did not allow the culture solution to permeate (leak) at all. The same results as above were obtained for all of the mixed particle groups No. 11, 12, and 13 of Example 2.

[0116] Example 7 <Examination of Reduction in Salt Concentration of Culture Solution> In Example 4, instead of the culture solution containing Dunaliella salina, "deep sea water or artificial seawater (adjusted to 12% by mass of salts including sodium chloride)", "seawater (salt concentration 3.5% by mass)", and "fresh water without Dunaliella (salt concentration 0.0% by mass)" were used. Otherwise, a water-impermeable structure was prepared on the funnel in the same manner as in Example 4, and the water permeability was observed.

[0117] When observed after one week, the order of water impermeability was deep sea water or artificial seawater (12% salt), seawater (salt concentration 3.5% by mass), fresh water (salt concentration 0.0% by mass). It was found that the higher the salt concentration, the higher the water impermeability, and an excellent water-impermeable structure could be formed. It was confirmed that the high-concentration salt spread into the gaps between bentonite and sand and served as a water barrier. It was also considered that this was due to the precipitation of sodium chloride crystals microscopically.

[0118] Example 8 <Examination of Differences in Cultivatability Depending on the Presence and Type of Bentonite> The following three types of bentonite powders (20 g) were mixed with 180 g of silica sand to obtain 200 g of a mixed particle group. Also, 200 g of silica sand was prepared. (1) Bentonite·TB-S (manufactured by Tachibana Materials Co., Ltd.; swelling power 23.0 mL / 2 g (American sodium bentonite)) (2) Bentonite·TB-250 (manufactured by Tachibana Materials Co., Ltd.; swelling power 9.0 mL / 2 g (calcium bentonite from Gunma, Japan)) (3) Bentonite·Kunigel (registered trademark) V1 (manufactured by Kunimine Industries Co., Ltd.; swelling power 16 mL / 2 g (from India)) (4) Without bentonite (only silica sand)

[0119] A total of 200 g each of 3 types of mixed particle groups and sand (only silica sand) were put into a 1200 mL rectangular container, dried and molded to prepare a simulated artificial pond. To this, 900 mL of a 12 mass% salt medium (Red Sea Salt) containing Dunaliella salina was added. It was left standing, and the cell density (cells / mL ) was measured over 18 days.

[0120] The first 3 days were the induction period, and the cell density did not increase. Days 4 to 8 were the logarithmic phase, and the cell density increased logarithmically. Days 9 to 17 were the stationary phase, and the increase and decrease in cell density were small. Up to the logarithmic phase (until the 8th day), the growth in the simulated artificial pond with the lowest swelling power (2) TB-250 was active, followed by (3) Kunigel V with medium swelling power, and the slowest growth was with the high swelling power (1) TB-S.

[0121] The growth in the simulated artificial pond with only silica sand (4) without using bentonite was lower during the logarithmic phase (until the 8th day) than any of (1), (2), and (3) using bentonite. It was suggested that the artificial pond manufactured with the mixed particle group using bentonite had higher growth properties of halophilic microalgae than the artificial pond manufactured with only sand.

[0122] From the results of Examples 9 and 10 described below, faster growth was observed outdoors where the illuminance (photon density) and water temperature were high, compared to the laboratory tests.

[0123] Example 9 <Expansion test (using a particle group composed of bentonite powder)> To conduct the expansion test, two artificial ponds with dimensions of 3 m × 5 m × depth 0.2 m (20 cm), whose schematic cross-section is shown in Fig. 2, were constructed outdoors in Chiba Prefecture, Japan. They were named "Pool A" and "Pool B" (see Figs. 2 and 3).

[0124] As shown in Fig. 2, holes were dug in the soil (ground) of the farm, the soil (ground) was compacted, a particle group composed of bentonite powder was added, and pressure was applied to form a water-impermeable structure 11a as shown in Fig. 2.

[0125] As the bentonite powder, "TB-S" manufactured by Tachibana Materials Co., Ltd. was used. The used "TB-S" is a commercial product made from the raw ore of sodium (Na)-type bentonite calculated in Wyoming, USA. Its moisture content is 10 mass% or less, the particle size is such that 90% or more passes through 250 mesh, the swelling power is 23 [mL / 2 g] or more, the apparent specific gravity is 0.70 - 0.85 g / cm 3 , and it has physical properties such as a pH of 9.0 - 10.5 in 1 mass% water and absorbs 10 times the mass of water.

[0126] Furthermore, on top of that, the soil of this land was put in and compacted to provide a soil layer with a thickness of 20 cm. From the bottom, a sandwich structure of "soil (ground) / water-impermeable structure 11a / soil layer" was formed by applying pressure and compacting (see Fig. 2).

[0127] Before introducing seawater (ocean deep water in Example 9) into the above artificial pond, the thickness of the water-impermeable structure composed of bentonite powder was in the range of 0.5 - 1 cm depending on the location, and the mass per bottom area of the pond of the water-impermeable structure was in the range of 3.5 - 7.0 kg / m 2 of the range. At the stage after introducing seawater (ocean deep water in Example 9) into the above artificial pond, the thickness of the water-impermeable structure was in the range of twice the above value (see Figure 2).

[0128] <<Examination of water impermeability>> The apparent specific gravity (apparent density) of bentonite is 0.7 g / cm 3 Therefore, due to the introduction of seawater, a water-impermeable structure that was sufficiently dense was formed. The permeability coefficient was in the range of 1.3×10 -9 [m / s] to 1.7×10 -10 [m / s], demonstrating excellent water impermeability. In addition, salts mainly composed of sodium chloride (NaCl) crystallized, and there was no water leakage at all. There was no water leakage even over time during the examination (excellent water impermeability was maintained).

[0129] <<Examination of growth rate>> Dunaliella salina was cultured in Pool A at the cell density shown on the 0th day of culture (left end) in Figure 3(a). Also, in Pool B, it was cultured at the cell density shown on the 0th day of culture (left end) in Figure 3(b).

[0130] The photon density [μmol / m 2 s] on the seawater surface of the artificial ponds in Pools A and B installed outdoors and the seawater temperature [°C] are shown in Table 3 below together with their measured values in the laboratory test of Example 10 described below.

[0131]

Table 3

[0132] Regarding the growth rate of Dunaliella salina, the results in Pool A are shown in Figure 3(a), and the results in Pool B are shown in Figure 3(b). The scale on the vertical axis in Figures 3(a), (b) and Figure 4, for example, "1.E+05", etc., indicates 10 5 [cells / mL], etc. The base of the logarithm on the vertical axis is "10". The vertical axis is log10 If the value is that of (cell density [cells / mL]), for example, "1.E+05" etc. described on the vertical axis is "5" etc.

[0133] As shown in FIGS. 3(a) and 3(b), in either of Pools A and B, the cell density increased 10-fold in 3 days. Even in the "artificial pond of 3 m × 5 m × depth 0.2 m (20 cm)" installed outdoors, a good growth rate was shown. It was found that the bentonite used in the study was excellent.

[0134] Furthermore, compared with the growth rate of the laboratory test of Example 10 described below, the growth rate of the scale-up test of Example 9 described above was faster. That is, in the laboratory test of Example 10, it took about 7 to 10 days for the cell density to increase 10-fold, whereas in the scale-up test of Example 9, it took about 3 to 4 days for the cell density to increase 10-fold.

[0135] Example 10 <Laboratory test conducted for comparison with the scale-up test of Example 9> On the same large funnel as in Example 3, a water-impermeable structure was prepared in the same manner as in Example 3 using a particle group composed of the bentonite powder used in Example 9. That is, a water-impermeable structure was provided in the same manner as in Example 3, except that a particle group composed of the bentonite powder used in Example 9 was used instead of the "mixed particle groups No. 11 to 13" of Example 3.

[0136] When the growth rate was determined, the results shown in the graph of FIG. 4 were obtained. It took about 7 to 10 days for the cell density to increase 10-fold. On the other hand, as described above, in the scale-up test of Example 9, it took about 3 to 4 days for the cell density to increase 10-fold.

[0137] Example 11 <Scale-up test (using a mixed particle group composed of bentonite powder and sand)> A scale-up test was conducted in the same manner as in Example 9, except that the particle group composed of the bentonite powder used in Example 9 was replaced with the No. 12 mixed particle group in Examples 2 and 3, and a water-impermeable structure with a thickness of 3.0 cm was provided.

[0138] When evaluated in the same manner as in Example 9, good results similar to those in Example 9 were obtained for both water impermeability and growth rate.

Industrial Applicability

[0139] According to the present invention, even when the material cost and the manufacturing cost are reduced and the manufacturing period is short, an artificial pond suitable for culturing halophilic microalgae can be manufactured. Further, when the artificial pond is discarded or abandoned, there is no risk of environmental destruction structurally, and since no petroleum-derived materials are used at all, it does not impose a burden on the environment. Therefore, large-scale culturing of microalgae becomes possible realistically, and it becomes possible to obtain de-petroleum energy and low-cost useful organic substances. In addition, "greening of the desert" which has not been achievable until now is realized, and it becomes a model of a sustainable society in which industrial activities can be carried out while reducing carbon dioxide. Therefore, it is widely used in, for example, the energy supply field, the chemical and pharmaceutical manufacturing fields, the civil engineering field, and the like.

Explanation of Signs

[0140] 10 Artificial pond 11a Water-impermeable structure (before introduction of seawater, etc.) 11b Water-impermeable structure (after introduction of seawater, etc., during culturing) 12 Seawater or artificial seawater 13 Halophilic microalgae A Ground B Ridge C Field

Claims

1. A method for manufacturing an artificial pond for culturing halophilic microalgae, which comprises at least the halophilic microalgae and seawater or artificial seawater, and is characterized in that a water-impermeable structure is provided by pressing a particle group containing bentonite powder on the side surface and / or bottom surface of the artificial pond. A method for manufacturing an artificial pond for culturing halophilic microalgae, which comprises at least the halophilic microalgae and seawater or artificial seawater, and is characterized in that a water-impermeable structure is provided by pressing a particle group containing bentonite powder and sand on the side surface and / or bottom surface of the artificial pond.

2. A method for manufacturing an artificial pond for culturing halophilic microalgae, which comprises at least the halophilic microalgae and seawater or artificial seawater, and is characterized in that a water-impermeable structure is provided by pressing a particle group containing bentonite powder and sand on the side surface and / or bottom surface of the artificial pond. The method for manufacturing an artificial pond according to claim 1, wherein a water-impermeable structure is provided by pressing a mixed particle group containing bentonite powder and sand on the side surface and / or bottom surface of the artificial pond.

3. The method for manufacturing an artificial pond according to claim 2, wherein the mass of the bentonite powder in the mixed particle group is 2% by mass or more and 80% by mass or less based on the total mass of the bentonite powder and sand in the mixed particle group.

4. The method for manufacturing an artificial pond according to any one of claims 1 to 3, wherein the thickness of the water-impermeable structure after pressing is 0.5 cm or more and 25 cm or less as an average value depending on the location of the artificial pond at the stage before seawater or artificial seawater is put in.

5. The method for manufacturing an artificial pond according to any one of claims 1 to 4, wherein the water-impermeable structure is provided so that the thickness of the water-impermeable structure becomes 1.0 cm or more and 50 cm or less as an average value depending on the location of the artificial pond in a steady state where seawater or artificial seawater is put in and halophilic microalgae are cultured, by absorbing water.

6. The area of the artificial pond is 10 m ２ The method for manufacturing an artificial pond according to any one of claims 1 to 5, wherein the area is 10 m or more.

7. In the case where a water-impermeable structure is provided by pressing a mixed particle group containing bentonite powder and sand, The method for manufacturing an artificial pond according to any one of claims 1 to 6, wherein an artificial pond is manufactured at a place that is originally a sandy area, the mixed particle group is obtained by adding bentonite from the outside to the sand constituting the sandy area and mixing them, and the water-impermeable structure is provided by pressing the mixed particle group.

8. The method for manufacturing an artificial pond according to any one of claims 1 to 7, wherein the seawater is deep ocean water.

9. A method for producing halophilic microalgae, characterized in that an artificial pond is manufactured using the method for manufacturing an artificial pond according to any one of claims 1 to 8, and halophilic microalgae, seawater or artificial seawater are put into the artificial pond to culture the halophilic microalgae.

10. A method for producing a useful organic substance, comprising obtaining the useful organic substance from a halophilic microalgae produced by using the method for producing a halophilic microalgae according to claim 9.

11. The method for producing a useful organic substance according to claim 10, wherein the useful organic substance is a carbohydrate or sugar; an oligopeptide, polypeptide or protein; a vitamin or vitamin precursor; a polyhydric alcohol; an oil or fat; a glycolipid, phospholipid or lipoprotein; or a hydrocarbon.

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