WO2014136574A1

WO2014136574A1 - Method for concentrating microalga culture fluid and apparatus therefor

Info

Publication number: WO2014136574A1
Application number: PCT/JP2014/053868
Authority: WO
Inventors: 橋本　和仁; 龍平中村; 英史大岡; 巌上田; 整松田
Original assignee: 国立大学法人東京大学; Ｊｘ日鉱日石エネルギー株式会社
Priority date: 2013-03-04
Filing date: 2014-02-19
Publication date: 2014-09-12
Also published as: TW201526790A; JP2014168409A; JP6183825B2

Abstract

This apparatus (20) for concentrating a microalga culture fluid has: a separation tank (21) for holding a microalga culture fluid which contains a microalga; a light irradiation unit (22) for irradiating the microalga culture fluid held in the separation tank (21) with a ray of light having a wavelength capable of attracting the microalga; and a take-out pipe (24) for taking out a concentrated culture fluid, namely, a microalga-rich part which is a part of the resulting microalga culture fluid and which has a microalga concentration enhanced by light irradiation. Thus, the present invention makes it possible to concentrate a microalgae culture fluid which contains a microalga at a low cost and with high efficiency, thereby enabling effective utilization of the microalga and culture fluid recovered after separation subsequent to the concentration.

Description

Method and apparatus for concentrating microalgae culture solution

The present invention relates to a method and apparatus for concentrating a microalgae culture solution containing microalgae.

In order to reduce the concentration of CO ₂ , one of the greenhouse gases and the cause of global warming, a technology for culturing microalgae and immobilizing CO ₂ by photosynthesis using these microalgae is known. It has been.

In addition to being able to be used as a dietary supplement and supplement material, microalgae can be used as a biofuel material because it produces oil and fat when growing by immobilizing CO ₂ by photosynthesis. , Attention is growing. In order to use such microalgae, it is necessary to separate and extract the microalgae from the microalgae culture solution containing the microalgae after culturing the microalgae.

Conventionally, as a method for separating microalgae from a microalgae culture solution, for example, a method of separating by forming a floc of microalgae by sedimentation by adding a flocculant and a method of performing centrifugation using a centrifuge are known. It has been.

Further, as another method for separating microalgae (algae) from the microalgae culture solution, there is a method described in JP-A-7-289240 (Patent Document 1). This publication states that “in the light irradiation tank 16 provided with the light source 18, the algal culture solution is irradiated with light having a light intensity stronger than the optimal light intensity for the growth of the algae, thereby improving the sedimentation properties of the alga bodies. Is separated from the culture medium ”(see summary).

JP 7-289240 A

However, the sedimentation separation method using a flocculant not only increases the running cost, but the recovered microalgae may not be used as they are because the flocculant is mixed in the collected microalgae, and The culture solution cannot be reused as a culture medium because the flocculant remains, and processing costs are also required when it is discharged. Further, in the centrifugal separation method, a great amount of energy is consumed for the operation of the centrifugal separator.

In addition, the method described in Patent Document 1 is a method for improving the separation property of microalgae by irradiating the algae culture solution with strong light, and has to rely on the natural sedimentation action, and is not necessarily efficient. May not be able to be separated. Moreover, since the algae culture solution is irradiated with intense light, energy consumption increases and there is a possibility of adversely affecting the microalgae.

The present invention has been made in view of such circumstances, and can be used to concentrate a microalgae culture solution containing microalgae efficiently at a low cost. It is an object of the present invention to provide a method and apparatus for concentrating a microalgae culture solution that enables effective use of the solution.

In order to achieve the above object, a method for concentrating a microalgae culture solution according to the present invention includes a light irradiation step of irradiating a microalgae culture solution containing microalgae with light having a wavelength that attracts the microalgae, An extraction step of extracting a portion of the microalgae culture solution in which the concentration of the microalgae is increased by light irradiation.

The light having a wavelength that the microalgae repels is simultaneously with the irradiation with the light having a wavelength that attracts the microalgae, or before or after the irradiation with the light having a wavelength that attracts the microalgae. It is preferable to irradiate from the side opposite to the side irradiated with light having a wavelength that attracts microalgae.
Moreover, in the said light irradiation process, it is preferable that the light of the wavelength which attracts the said micro algae is irradiated to this micro algae culture solution from the lower side of a micro algae culture solution.
Moreover, it is preferable that the said micro algae produce | generates fats and carbohydrates by photosynthesis, and accumulate | stores in a cell.
The microalgae is preferably Euglena.
The light having a wavelength that attracts the microalgae is preferably light containing a wavelength component in the range of 500 nm to 550 nm.

Further, the method for concentrating a microalgae culture solution according to the present invention includes a light irradiation step of irradiating a microalgae culture solution containing microalgae with light having a wavelength that the microalgae avoids, and the microalgae culture solution. And taking out a portion where the concentration of the microalgae is increased by the light irradiation.

The apparatus for concentrating a microalgae culture solution according to the present invention attracts the microalgae to a storage unit that stores a microalgae culture solution containing microalgae, and the microalgae culture solution that is stored in the storage unit. And an attracting wavelength light irradiating unit for irradiating light having a wavelength to be extracted, and an extraction unit for extracting a portion of the microalgae culture solution in which the concentration of the microalgae has increased due to light irradiation.
Further, the microalgae culture solution stored in the storage unit is irradiated with light having a wavelength that the microalgae repels, and the side of the microalgae culture solution that is irradiated with light having a wavelength that induces the microalgae. It is preferable to further have a repelling wavelength light irradiating part for irradiating from.

ADVANTAGE OF THE INVENTION According to this invention, the micro algae which can concentrate the micro algae culture solution containing a micro algae efficiently at low cost, and enable the effective utilization of the micro algae and culture solution which are concentrated and collect | recovered after isolation | separation A method and apparatus for concentrating a culture solution can be provided.

1 is a schematic configuration diagram of a microalgae separation and recovery system to which a microalgae culture broth concentration apparatus according to an embodiment of the present invention is applied. It is a flowchart which shows the procedure of the isolation | separation collection method of a micro algae. It is a typical top view for demonstrating the light irradiation method in the experiment of the phototaxis of the micro algae in a two-dimensional plate. It is a graph which shows the experimental result of the phototaxis of the micro algae in the plate at the time of using the light of a wavelength of 530 nm. It is a graph which shows the relationship between the wavelength of the irradiated light, and a cell existence rate maximum value. It is a typical top view for demonstrating the mode of light irradiation in the experiment of the phototaxis of the micro algae in a two-dimensional petri dish. It is a schematic diagram for demonstrating the liquid sampling from a vial bottle. It is a graph which shows the light absorbency of each sample arranged in the order of sampling at the time of conducting experiment using green light (light with a wavelength of 530 nm). It is a graph which shows the light absorbency of each sample arranged in the order of sampling at the time of conducting experiment without light. It is a graph which shows the experimental result of the phototaxis of the micro algae in a three-dimensional vial. It is a graph which shows the light absorbency of each sample arranged in the order of sampling at the time of performing experiment which irradiated green light (light with a wavelength of 530 nm) toward the bottom part of a measuring cylinder with a large capacity | capacitance from the lower side.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings shown below, the size and shape of the members may be schematically represented by being modified or exaggerated for convenience of explanation.

FIG. 1 is a schematic configuration diagram of a microalgae separation and recovery system 100 to which a microalgae culture solution concentrating device 20 according to an embodiment of the present invention is applied.
As shown in FIG. 1, a microalgae separation and recovery system 100 includes a culture tank 10, a microalgae culture liquid concentrator (hereinafter also simply referred to as “concentrator”) 20, a separated water recovery tank 30, and a centrifuge 40. The dryer 50 and the alga body collection tank 60 are mainly provided.

The culture tank 10 is a tank for cultivating microalgae and contains a microalgae culture solution containing microalgae in a culture solution (medium). A pipe line 11 extending from the inside of the culture tank 10 is connected to the concentrating device 20, and a first control valve 71 and a first pump 81 are installed in the pipe line 11.

Examples of microalgae that can be used in the present invention include Euglena. Euglena is a group of flagellates, including Euglena, which is famous as a motile algae. Most Euglena has a chloroplast and photosynthetizes for an autotrophic life, but some are predatory and some are absorptive.
Euglena is a genus classified into both zoology and botany.
In zoology, there are Euglenida in the eyes belonging to Protozoa's Mastigophorea and Phytomastigophorea, which are three sub-Euglenoidina, Peranemoidina It consists of Petalomonadoidina.
Euglenoidina includes Euglena, Trachelemonas, Strombonas, Phacus, Lepocinelis, Astasia and Colacium as genera.
In botany, Euglenophyta is the Euglenophyta, followed by Euglenophyceae and Euglenales, and the genera included in this eye is similar to that of the Euglena and the animal taxonomy. is there.
In addition to this, one or two species from cyanobacteria, green algae and treboxya, plastino algae (green algae), primordial red algae, diatoms, round stone algae, dinoflagellate algae, golden spot algae, etc. The above can be selected and used.

Examples of cyanobacteria include Chroococcacae, Stigonematacae, Mastigocladacae, and Oscillatroriacae. In addition, Synechococcus such as Synechococcus lividus and Synechococcus elongatus; Synechocystis such as Synechocystis minervae; Mastigocladus such as Mastigocladus laminosus; Phormidium such as Phormidium laminosus; , Fisherella and the like.
Furthermore, Anabanena variabilis belonging to the genus Anabaena ATCC 29413, Cyanothece sp. Belonging to the genus Cyanothece sp. ATCC 51142, Synechococcus sp. PCC 7942 belonging to the genus Synechococcus and Anastis Anacystis nidulans belonging to the genus (Anacystis), thermophilic cyanobacteria and the like can be used.

Examples of green algae and treboxya include aerial algae such as chlorella (including phylogenetically separated parachlorella), Chlamydomonas, Donariella, Senedesmus, Botryococcus, Sticococcus, Nannochloris, and Desmodemus Can do. Specifically, the basic properties such as Chlorella および vulgaris and Chlorella saccharophila (Chlorella), Dunaliella salina, Dunaliella tertiolecta, and photosynthesis are the same, but are classified as treboxya algae by molecular phylogenetic analysis. Parachlorella kessleri (Chlorella kessleri). In addition, Chlamydomonas reinhardtii, Chlamydomonas moewusii, Chlamydomonas eugametos, Chlamydomonas eugametos, Chlamydomonas doms・ Obricks (Senedesmus obliquus), Stichococcus ampliformis belonging to the genus Stichococcus, Nannochloris bacillaris belonging to the genus Nannochloris, and desmodes mus Desmodesmus subspicatus belonging to the genus can be mentioned.

In addition, examples of the plasino algae (green algae) include tetracermis, and examples of the primordial red algae include cyanidiozone, cyanidium, gardi area, porphyridium, and the like.
The microalgae that can be used in the present invention can be any oils and carbohydrates that can be produced by photosynthesis and accumulated in cells, and any carbohydrate that accumulates in cells can be oiled. Anything can be used and is not limited to those described above.

For example, when Euglena is used as the microalgae, the culture solution is a culture solution to which nutrient salts such as a nitrogen source, a phosphorus source, and a mineral are added, for example, a modified Cramer-Myers medium ((NH ₄ ) ₂ HPO ₄ 1.0 g / L, KH ₂ PO ₄ 1.0 g / L, MgSO ₄ · 7H ₂ O 0.2 g / L, CaCl ₂ · 2H ₂ O 0.02 g / L, Fe ₂ (SO ₄ ) ₃ · 7H ₂ O 3 mg / L , MnCl ₂ · 4H ₂ O 1.8 mg / L, CoSO ₄ · 7H ₂ O 1.5 mg / L, ZnSO ₄ · 7H ₂ O 0.4 mg / L, Na ₂ MoO ₄ · 2H ₂ O 0.2 mg / L CuSO ₄ .5H ₂ O 0.02 mg / L, thiamine hydrochloride (vitamin B ₁ ) 0.1 mg / L, cyanocobalamin (vitamin B ₁₂ ) 0.0005 mg / L, (pH 3.5)) . Note that (NH ₄ ) ₂ HPO ₄ can be converted to (NH ₄ ) ₂ SO ₄ or NH ₃ aq.
Needless to say, the culture solution is not limited to a medium suitable for the microalgae to be cultured.

The concentration device 20 has a separation tank (accommodating unit) 21 that accommodates a microalgae culture solution containing microalgae sent from the culture tank 10, and a wavelength that attracts the microalgae to the microalgae culture solution that is accommodated in the separation tank 21. An attracting wavelength light irradiating unit 22 that irradiates the light, a repelling wavelength light irradiating unit 23 that irradiates the microalgae culture solution accommodated in the separation tank 21 with a wavelength at which the microalgae repels, and a fine in the separation tank 21. It has an extraction tube (extraction unit) 24 for extracting the concentrated culture solution, which is a portion of the algae culture solution in which the concentration of microalgae has increased due to light irradiation. In the present invention, light irradiation means at least one of light irradiation by the attracting wavelength light irradiation unit 22 and light irradiation by the repelling wavelength light irradiation unit 23.

At least the bottom wall 211 of the separation tank 21 is formed of a transparent member that can transmit light emitted from the attracting wavelength light irradiation unit 22. The separation tank 21 is made of, for example, resin, glass or the like. However, the separation tank 21 may be formed of an opaque member such as a metal other than the bottom wall formed of a transparent member. The shape and size of the separation tank 21 are not particularly limited and can be set as appropriate. For example, a transparent member may be fitted into a part of the bottom wall 211.

The attracting wavelength light irradiation unit 22 is disposed below the separation tank 21. The attracting wavelength light irradiation unit 22 irradiates the microalgae culture solution with light having a wavelength that attracts microalgae from the lower side of the microalgae culture solution accommodated in the separation tank 21. The attracting wavelength light irradiation unit 22 is installed on a support member 25 fixed to the separation tank 21. However, the induction wavelength light irradiation unit 22 may be installed through the bottom wall 211 of the separation tank 21 so that the light emitting part at the tip of the induction wavelength light irradiation unit 22 faces the separation tank 21. Furthermore, a member that emits light on the inner surface of the bottom wall 211 of the separation tank 21 may be laid as the attracting wavelength light irradiation unit 22.

As light having a wavelength that attracts microalgae, light containing a wavelength component in the range of 500 nm to 550 nm, preferably monochromatic light (green light) of 530 nm is used. The light source of the attracting wavelength light irradiation unit 22 is not particularly limited. For example, one or more light sources such as an LED illumination device, a xenon lamp, and an organic EL illumination device are used, and a filter, A wavelength adjusting member such as a spectroscope may be used. Moreover, it is also possible to utilize sunlight using a wavelength adjusting member.

The repelling wavelength light irradiation unit 23 is disposed on the opposite side of the attracting wavelength light irradiation unit 22, that is, above the liquid surface of the microalgae culture solution, with the microalgae culture solution accommodated in the separation tank 21 interposed therebetween. . The repelling wavelength light irradiation unit 23 irradiates the microalgae culture solution with light having a wavelength that the microalgae repels from above the microalgae culture solution accommodated in the separation tank 21. The repelling wavelength light irradiation unit 23 is installed on a support member 26 fixed to the separation tank 21.

As the light having a wavelength that the microalgae avoids, light having a wavelength component in the range of 400 nm to 450 nm is preferable, and monochromatic light having a wavelength of 400 nm is more preferable. The light source of the repelling wavelength light irradiation unit 23 is not particularly limited. For example, one or more light sources such as an LED lighting device and a xenon (Xe) lamp are used, and wavelength adjusting members such as a filter and a spectroscope are used. Can be used. Moreover, it is also possible to utilize sunlight using a wavelength adjusting member.

The extraction pipe 24 is connected to the bottom wall 211 of the separation tank 21. An extraction pipe 24 extending from the bottom wall 211 of the separation tank 21 is connected to the centrifuge 40, and a second control valve 72 and a second pump 82 are installed in the extraction pipe 24.

The separation tank 21 is connected to a first separated water recovery pipe 28 for collecting a culture solution that is a portion other than the concentrated culture solution of the microalga culture solution after the light irradiation as separated water. Here, the first separation water recovery pipe 28 extends through the side wall 27 of the separation tank 21 into the separation tank 21, and the end of the first separation water recovery pipe 28 in the separation tank 21 has a water A separation water recovery port portion having a structure floating on the surface is provided. A drainage nozzle configured to be positioned below the water surface is provided in the separation water recovery port portion. The piping part in the separation tank 21 of the first separated water recovery pipe 28 has a flexible structure having mobility in the separation tank 21, for example, a flexible hose and a plurality of tubes of different diameters are nested. Those that move flexibly as the water level rises and lowers, such as a stretchable tubular structure connected in a formula, are preferred. According to such a configuration, even if the water decreases as the separated water is collected and the water level falls, the separated water can be collected continuously. In FIG. 1, a state in which the drainage nozzle descends as the water level of the separated water descends is indicated by a downward white arrow. However, the configuration of the end of the first separated water recovery pipe 28 on the separation tank 21 side is not limited to the above-described configuration. For example, the first separated water recovery pipe 28 has a plurality of branched pipes, and a separation water recovery port portion is provided at an end of each branch pipe located in the separation tank 21, and the water surface is A structure in which the separation water recovery port portion is switched as it descends may be used. An end of the first separated water recovery pipe 28 extending from the separation tank 21 on the side opposite to the separation tank 21 is opened toward the separated water collection tank 30, and the first separated water collection pipe 28 includes a first A third control valve 73 and a third pump 83 are installed.

The centrifuge 40 centrifuges microalgae from the concentrated culture solution via the extraction tube 24. Examples of the centrifuge 40 include, but are not limited to, a separation plate type centrifuge, a cylindrical centrifuge, and the like. However, the centrifuge 40 can be omitted when a concentrated culture solution having a predetermined concentration or more is obtained by the concentrator 20, for example.

The centrifuge 40 includes a first transfer path 41 for transferring the microalgae centrifuged from the concentrated culture solution, and a second separation for recovering the separated water after the microalgae are centrifuged from the concentrated culture solution. A water recovery pipe 42 is connected. A first transfer path 41 extending from the centrifuge 40 is connected to the dryer 50. The end of the second separated water recovery pipe 42 extending from the centrifuge 40 opens toward the separated water recovery tank 30. The separated water recovery tank 30 is a tank that collects and stores the culture solution after separating the microalgae from the microalgae culture solution stored in the separation tank 21 as separated water. The separated water collected in the separated water collection tank 30 can be returned to the culture tank 10 and reused.

The dryer 50 dries microalgae containing moisture. Examples of the dryer 50 include dryers using waste heat from facilities such as factories, but are not limited thereto, and commercially available hot air dryers, spray dryers, slurry dryers, freeze dryers, etc. Furthermore, drying by sun drying is also possible.

A second transfer path 51 for transferring dried microalgae is connected to the dryer 50, and the end of the second transfer path 51 extending from the dryer 50 is in the alga body collection tank 60. It is arranged to face. The algal body collection tank 60 is a tank that collects and stores the microalgae (algae) separated from the microalgae culture solution stored in the separation tank 21.

Next, the operation of the microalgae separation and recovery system 100 configured as described above will be described with reference to FIG. 2 in addition to FIG.
FIG. 2 is a flowchart showing the procedure of the microalgae separation and recovery method.

As shown in FIG. 2, first, microalgae are cultured in a culture solution (medium) in a culture tank 10 (step S10). The culture of microalgae in this step S10 can also be performed in the air atmosphere, but in order to increase the amount of oil and fat and carbohydrate produced by photosynthesis, carbon dioxide gas is actively supplied to the culture solution. It is preferable to carry out at a dissolved carbon dioxide concentration higher than air aeration.

Then, the microalga culture solution containing the microalgae in the culture tank 10 opens the first control valve 71 and operates the first pump 81, thereby separating the concentrator 20 from the culture tank 10 via the pipe line 11. It is sent into the tank 21.

Subsequently, the microalgae culture solution is concentrated by the concentration device 20 (step S20). In step S <b> 20, the attracting wavelength light irradiation unit 22 irradiates the microalgae culture solution with light having a wavelength that attracts microalgae from the lower side of the microalgae culture solution accommodated in the separation tank 21. Further, the repellent wavelength light irradiation unit 23 irradiates the microalgae culture solution with light having a wavelength that the microalgae repels from above the microalgae culture solution accommodated in the separation tank 21. Therefore, the microalgae in the microalgae culture solution are collected in the lower part of the separation tank 21 due to the phototaxis of the microalgae that the microalgae move by the light of a specific wavelength. Thereby, the concentrated culture solution which is a part where the density | concentration of the micro algae became high is formed in the micro algae culture solution in the separation tank 21. FIG.

Then, the concentrated culture solution formed in the separation tank 21 is taken out from the lower part in the separation tank 21 through the extraction pipe 24 by opening the second control valve 72 and operating the second pump 82, and then centrifuged. Sent to machine 40.

The concentrated culture solution in the separation tank 21 is taken out after being left for a predetermined time in a state in which the microalgae culture solution is irradiated with light by the attracting wavelength light irradiation unit 22 and the repelling wavelength light irradiation unit 23, for example. Is called. However, light irradiation may be performed while the concentrated culture solution is being taken out via the take-out tube 24. In this way, it is possible to take out a concentrated culture solution having a higher concentration.

On the other hand, the culture solution which is a part other than the concentrated culture solution in the microalga culture solution in the separation tank 21 serves as the separation water, and the third control valve 73 is opened and the third pump 83 is operated. It is sent from the inside through the first separated water collection pipe 28 and collected in the separated water collection tank 30 (step S30). At this time, it is sequentially recovered from the upper layer of the culture solution in the separation tank 21 through the drain nozzle of the collection port provided at the end of the first separation water recovery pipe 28 on the separation tank 21 side, as shown in FIG. As indicated by the white arrow, as the liquid level in the separation tank 21 is lowered, the drain nozzle is also lowered to continuously collect the separated water.

In addition, it is preferable to start taking out the concentrated culture broth through the take-out pipe 24 after the operation of collecting the culture broth (separated water) in the separation tank 21 into the separated water collection tank 30 is started or completed. By doing so, it is possible to take out the separated water at the time of taking out the concentrated culture solution through the take-out tube 24, so that a concentrated culture solution having a higher concentration can be taken out.

In step S40, centrifugation by the centrifuge 40 is performed. That is, microalgae are centrifuged from the concentrated culture solution sent from the lower part in the separation tank 21. Thereby, the density | concentration of a concentrated culture solution can be made still higher. Here, since the microalgae culture solution is concentrated in advance by the concentrating device 20, less energy is consumed in the operation of the centrifuge 40. As described above, the centrifugation in step S40 can be omitted.

Then, the microalgae centrifuged from the concentrated culture solution are sent to the dryer 50 via the first transfer path 41. On the other hand, the culture solution after centrifuging microalgae from the concentrated culture solution is sent as separated water through the second separated water recovery pipe 42 and recovered in the separated water recovery tank 30 (step S30).

The separated water collected in the separated water collection tank 30 may be returned to the culture tank 10 and mixed. In this way, the separated water can be effectively reused as a culture medium. Further, the non-concentrated microalgae remaining in the separated water can be cultured again.

In step S50, drying by the dryer 50 is performed. That is, the microalgae containing moisture are dried. Thereby, the water | moisture content which becomes obstructive of the collection | recovery of fats and oils in step S70 mentioned later is removed.

Then, the dried microalgae are sent through the second transfer path 51 and are collected in the alga body collection tank 60 (step S60).

Subsequently, the oil is collected (S70). In this step S70, fats and oils are extracted and recovered from the cells of the microalgae recovered in the alga body recovery tank 60. Extraction of fats and oils from the cells of microalgae can be performed by, for example, a solvent extraction method using an organic solvent or a supercritical CO ₂ extraction method.

And, biofuels such as light oil and jet fuel can be manufactured by refining and reforming the recovered oils and fats. In addition, microalgae from which fats and oils have been extracted have protein and pigment components that are cell components remaining, and solubilize or dry organic matter as it is or biologically and / or chemically. Therefore, it can be used as a raw material for biomass such as feed, fertilizer, solid fuel, and raw materials for chemical products.

As described above, the concentration device 20 according to the present embodiment has a separation tank 21 that contains a microalgae culture solution containing microalgae, and a wavelength that attracts the microalgae to the microalgae culture solution that is contained in the separation tank 21. It has the attracting wavelength light irradiation part 22 which irradiates light, and the extraction tube 24 which takes out the concentrated culture solution which is a part where the density | concentration of the micro algae became high by light irradiation among the micro algae culture solutions. That is, the method of concentrating the microalgae culture solution performed in the concentration device 20 includes a light irradiation step of irradiating the microalgae culture solution containing microalgae with light having a wavelength that attracts microalgae, and a microalgae culture solution. And taking out a portion where the concentration of microalgae is increased by the light irradiation.

Therefore, according to the present embodiment, the microalgae in the microalgae culture solution are attracted to the side irradiated with the light of the wavelength that attracts the microalgae due to the phototaxis of the microalgae that the microalgae move by the light of the specific wavelength. To be collected. Thereby, the concentrated culture solution which is the part where the density | concentration of the micro algae became high is formed in the micro algae culture solution in the separation tank 21, and this concentrated culture solution can be taken out. In the present invention, taking out a portion having a high concentration of microalgae also includes obtaining a portion having a high concentration of microalgae by removing a portion having a low concentration of microalgae. It is a concept.
In addition, the present embodiment does not depend solely on the natural sedimentation action, and enables efficient concentration by irradiation with light of a specific wavelength, and does not adversely affect microalgae.
In addition, since the flocculant is not used, the collected microalga can be effectively used without being mixed with the flocculant, and the culture liquid (separated water) after the microalgae recovery is as follows. The flocculant does not remain and can be reused as a culture medium, and the processing becomes simple even when discharged. Furthermore, since the microalgae culture solution is concentrated in advance by the concentrating device 20, even if the centrifuge 40 is used, less energy is consumed in the operation.
That is, according to this embodiment, the microalgae culture solution containing microalgae can be efficiently concentrated at low cost, and the microalgae and culture solution collected after concentration can be effectively used. It is possible to provide a method and apparatus for concentrating a microalgae culture solution.

Further, in the present embodiment, the light having a wavelength that the microalgae avoids is emitted from the microalgae culture solution at the same time as the irradiation with the light having the wavelength that attracts the microalgae, or before or after the irradiation with the light having the wavelength that attracts the microalgae. Irradiated from the side opposite to the side irradiated with light having a wavelength that attracts microalgae. According to such a configuration, since the microalgae in the microalgae culture solution escape from the side irradiated with the light of the wavelength repelled by the microalgae, the light of the wavelength attracting the microalgae is irradiated. More microalgae in the microalgae culture are collected. On the other hand, when microalgae gather on the side irradiated with light of a wavelength that attracts microalgae, the light of the wavelength that attracts microalgae is gradually blocked by the microalgae that gathered and hardly reaches the back side. Become. For this reason, there is a possibility that the attracting action of microalgae may be reduced, but the trapping action of collecting microalgae in the microalgae culture solution can be supplemented by the repellent action of microalgae by the light of the wavelength that microalgae avoids. . Therefore, the microalgae culture solution can be concentrated more efficiently.

Moreover, in this embodiment, the light of the wavelength which attracts a micro algae is irradiated to this micro algae culture solution from the lower side of a micro algae culture solution. According to such a configuration, in addition to the action of collecting microalgae by light irradiation, a natural sedimentation action is also exhibited. Thereby, the micro algae in a micro algae culture solution can be collected more efficiently in the lower part in the separation tank 21. Further, since the separated water can be collected from the upper side in the separation tank 21, the separated water can be efficiently collected without drawing the concentrated culture solution as much as possible.

Moreover, what produces | generates fats and carbohydrates by photosynthesis and accumulate | stores in a cell as a micro algae can be used. Such microalgae can be used as a material such as a nutritional supplement or a biofuel material.
Further, for example, Euglena can be used as the microalgae. Euglena has a high ability to immobilize CO ₂ by photosynthesis, and at the same time has abundant nutrients, so it is highly useful as a nutritional supplement, etc. In addition, oil refined from fats and oils extracted from cells is light. Therefore, it has the advantage of being suitable for jet fuel.

In this embodiment, light having a wavelength component in the range of 500 nm to 550 nm, more preferably 530 nm monochromatic light (green light) is used as the light having a wavelength that attracts microalgae. According to such a structure, since the attracting action of the microalgae by the light of the wavelength attracting the microalgae is larger, the microalgae culture solution can be concentrated more efficiently.

As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to the structure described in above-described embodiment, The combination thru | or selecting suitably the structure described in embodiment is included. The configuration can be changed as appropriate without departing from the spirit of the invention. Further, a part of the configuration of the above-described embodiment can be added, deleted, or replaced.

For example, in the above-described embodiment, the concentration device 20 includes both the attracting wavelength light irradiation unit 22 and the repelling wavelength light irradiation unit 23, but either the attraction wavelength light irradiation unit 22 or the repelling wavelength light irradiation unit 23 is used. It is also possible to be configured so that one is provided. Even in this case, a predetermined effect can be expected because, for example, the collection action of collecting the microalgae in the microalgae culture solution can be exhibited in the lower part of the separation tank 21.

Further, in the above-described embodiment, it is assumed that light having a wavelength that repels microalgae is irradiated simultaneously with irradiation of light having a wavelength that attracts microalgae, but the present invention is limited to this. is not. For example, it may be configured to irradiate light having a wavelength that the microalgae avoid before or after irradiation with light having a wavelength that attracts the microalgae.
Further, regarding the start timing of light irradiation, in the above-described embodiment, it is assumed that light irradiation by the attracting wavelength light irradiation unit 22 and light irradiation by the repelling wavelength light irradiation unit 23 are started simultaneously. The present invention is not limited to this. For example, light irradiation by the repelling wavelength light irradiation unit 23 may be started after the light irradiation by the attracting wavelength light irradiation unit 22 is started, or vice versa. Furthermore, the light irradiation by the attracting wavelength light irradiation unit 22 and the light irradiation by the repelling wavelength light irradiation unit 23 may be performed alternately.

In the above-described embodiment, light having a wavelength that attracts microalgae is irradiated to the microalgae culture solution from below the microalgae culture solution, but the present invention is not limited to this. What is necessary is just to comprise so that the light of the wavelength which attracts a micro algae may be irradiated from either one of the circumference | surroundings (upper / lower / left / right front / rear) of the micro algae culture solution accommodated in the separation tank 21. Since the microalgae inside are collected on either one of the surroundings (up, down, left and right, back and forth), a concentrated culture solution can be formed and taken out.

In addition, a concentration sensor such as a spectrophotometer is attached to the separation tank 21 of the concentrator 20 to measure the concentration of microalgae in the portion of the microalgae culture solution where the concentration of microalgae has increased due to light irradiation. It is also possible to configure as described above. If the concentration sensor detects a concentration equal to or higher than a predetermined value, the concentrated algae culture solution can be concentrated more efficiently if the concentrated culture solution is taken out.

[Experimental example]
Next, the effect of the present invention will be described using the following experimental example. However, the technical scope of the present invention is not limited by the following experimental examples.

<Experiment 1> Experiment on the phototaxis of microalgae in a two-dimensional plate (experimental method)
(1) Preconditions Experiments on the phototaxis of microalgae in a two-dimensional (horizontal plane) plate were carried out in a shield box covered with aluminum foil and without a light source other than the Xe lamp.
(2) Microalgae Euglena was used as a microalgae.
(3) Culture conditions CM (Cramer-Myers) medium was used for the culture solution. During the culture, light from a fluorescent lamp was irradiated. The CO ₂ concentration was 5% (in air). The temperature was 32 ° C. Moreover, it stirred with the stirring bar.
(4) Experimental plate preparation procedure (a) A solution (solution A) prepared by removing the vitamins from the CM medium to a double concentration was prepared.
(B) A 2 g / L bactagar solution (solution B) was prepared.
(C) Solution A and solution B were each autoclaved. The reason why the solution A and the solution B were separately subjected to autoclaving is that bactagar, a kind of sugar, is decomposed when heated under acidic conditions.
(D) While hot, Solution A and Solution B were mixed at a ratio of 1: 1.
(E) The mixed solution was thinly poured on a plate for a plate reader in a clean bench and allowed to cool at room temperature.
(F) The agar medium solidified in the plate was stored refrigerated.

(5) Measurement of Light Irradiation and Absorbance During Concentration FIG. 3 is a schematic plan view for explaining a light irradiation method in a microalgal phototaxis experiment in a two-dimensional plate. For the sake of clarity, as shown in FIG. 3, the direction perpendicular to the light irradiation direction (up and down direction in the plane of FIG. 3) is the X-axis direction, and the direction along the light irradiation direction (left and right in the plane of FIG. 3). Direction) is the Y-axis direction (the same applies to FIG. 4).
As shown in FIG. 3, on the agar medium 2 prepared in the plate 1, about 15 to 20 ml of a microalgae culture solution (algae suspension) containing microalgae cultured in autotroph was poured. .
Then, the monochromatic light was irradiated from the side (right side in FIG. 3) with the Xe lamp 3 at 20 mW / cm ² in the direction of arrow 4 and left for 24 hours.
Subsequently, using a plate reader (TECAN Infinite M200PRO), the absorbance at 96 locations formed by dividing the plate 1 into 8 parts in the X direction and 12 parts in the Y direction was measured. Absorbance is expressed by the logarithm of the ratio of incident light intensity to transmitted light intensity when light of a specific wavelength (here, wavelength of 680 nm due to light absorption of chlorophyll) is applied to each measurement unit, and the larger the value, the greater the value. Indicates that the concentration is high.
Such light irradiation by the Xe lamp 3 was performed using light (monochromatic light) of wavelengths of 400 nm, 500 nm, 530 nm, 550 nm, 600 nm, 640 nm, 680 nm, and 700 nm, and the absorbance was measured for each.

(6) Experimental Results FIG. 4 is a three-dimensional graph showing the experimental results of the microalgae phototaxis in the plate when light having a wavelength of 530 nm is used.
The X-axis direction and the Y-axis direction shown in FIG. 4 correspond to FIG. 3, and the XY plane formed by the plane including the X-axis and the Y-axis represents the surface of the plate 1. The Z-axis direction represents the cell presence rate (%) in each of the 96 measurement units. The cell abundance (%) indicates what percentage of the microalgae (cells) in the entire plate 1 is present in the corresponding measurement part, and the absorbance in each measurement part relative to the total absorbance of all measurement parts. Given in proportion.

As shown in FIG. 4, when light having a wavelength of 530 nm is used, almost all the microalgae are collected near the light irradiation part, while on the opposite side of the plate 1 from the light irradiation part. It can be seen that there are almost no microalgae. Thus, it can be seen that light having a wavelength of 530 nm has an extremely large attracting action for microalgae. Here, the peak P in the graph of FIG. 4 indicates the highest cell existence rate (maximum cell existence rate) among all the measurement units.

FIG. 5 is a graph showing the relationship between the wavelength of irradiated light and the maximum cell existence rate.
As shown in FIG. 5, it can be seen that light having a wavelength of 530 nm has the greatest attracting action of microalgae. Moreover, it turns out that the attracting action of micro algae is comparatively large also for the light of each wavelength of 500 nm and 550 nm.

<Experiment 2> Experiment on the phototaxis of microalgae in a two-dimensional petri dish (experiment method)
(1) Preconditions Experiments on the phototaxis of microalgae in a two-dimensional (horizontal plane) petri dish were performed in a shield box covered with aluminum foil, with no light source other than the Xe lamp.
(2) Microalgae and (3) Culture conditions are the same as in Experiment 1.
(4) Experimental Petri dish Preparation Procedure The same procedure as the experimental plate preparation procedure of Experiment 1 is used except that a sterile petri dish is used instead of the plate.
(5) Light Irradiation During Concentration FIG. 6 is a schematic plan view for explaining the state of light irradiation in a microalgal phototaxis experiment in a two-dimensional petri dish.
As shown in FIG. 6, on the agar medium 2a created in the petri dish 5, a microalgae culture solution (algae suspension) containing microalgae cultured by autotroph was poured. Then, the Xe lamp 3 from the side (left side in FIG. 6) was left for 24 hours while being irradiated with light having a wavelength of 400 nm at 20 mW / cm ² . Further, in another petri dish 5, the same light irradiation was performed using light having a wavelength of 530 nm.
(6) Experimental Results As shown in FIG. 6, it can be seen that when a light having a wavelength of 400 nm is used, microalgae escape from the vicinity of the light irradiation portion. Thus, it can be seen that light with a wavelength of 400 nm has an extremely large repellent effect on microalgae. On the other hand, when light having a wavelength of 530 nm is used, almost all the microalgae are collected in the vicinity of the light-irradiated part, and it can be seen that the attracting action of the microalgae is extremely large.

<Experiment 3> Experiment on phototaxis of microalgae in 3D vial (experimental method)
(1) Prerequisites Experiments on the phototaxis of microalgae in a three-dimensional (in space) vial are conducted in a shield box covered with aluminum foil in the case of light irradiation, and there is no light source other than the Xe lamp. Went in state.
(2) Microalgae and (3) Culture conditions are the same as in Experiment 1.
(4) Procedure for making vials for experiments 15 ml of microalga culture solution (algae suspension) containing microalga cultured in autotroph in a 20 ml vial was used (without light / green light was used) Case).
(5) Measurement of light irradiation and absorbance during concentration In the experiment without light, the entire vial was wrapped with aluminum foil and shielded from light for 24 hours. In an experiment using green light (light having a wavelength of 530 nm), the corresponding light is irradiated at 20 mW / cm ² from the light source installed on the lower side of the vial toward the bottom of the vial, and left for 24 hours. did.
FIG. 7 is a schematic diagram for explaining liquid sampling from a vial bottle.
As shown in FIG. 7, sampling was performed by moving from the upper layer of the liquid in the vial 6 in order from the upper left to the lower right of the plurality of recesses 8 formed in the microplate 7. Sampling of the liquid is performed approximately 0.5 ml each in the case of no light and in the case of using green light, and the absorbance of each sample at 680 nm (wavelength due to light absorption of chlorophyll) is measured with a plate reader (TECAN Infinite M200PRO). ).

(6) Experimental Results FIG. 8 is a graph showing the absorbance of each sample arranged in the sampling order when an experiment using green light is performed. That is, FIG. 8 shows the concentration distribution of microalgae in the liquid in the vial 6 when an experiment using green light is performed. In addition, sample No. in FIG. Indicates a sampling order number (the same applies to FIGS. 9 and 11). As shown in FIG. 8, when an experiment using green light was performed, the last four samples in the sampling order showed extremely high absorbance, and the concentrated culture was a portion where the concentration of microalgae was high. It can be seen that a liquid is formed.
FIG. 9 is a graph showing the absorbance of each sample arranged in the sampling order when an experiment without light is performed. That is, FIG. 9 shows the concentration distribution of microalgae in the liquid in the vial 6 when an experiment without light is performed. As shown in FIG. 9, when an experiment without light is performed, the absorbance of each sample is not entirely different, and it is understood that the microalgae are not concentrated.
FIG. 10 is a chart showing the experimental results of the phototaxis of microalgae in a three-dimensional vial. The absorbance (initial value) is obtained by measuring the absorbance before the treatment. Absorbance (after treatment, concentrated portion) indicates the average absorbance of a sample group (concentrated portion) having a high concentration near the end in the sampling order after treatment. In addition, the concentration part is not formed when the experiment without light is performed, but the calculation was performed assuming the same number of sample groups as the concentration part when the experiment using green light was performed. . Absorbance (after treatment, upper part) indicates the average absorbance of the sample group (upper part) other than the concentrated part after treatment. The degree of concentration (fold) is a value indicating how many times the concentration has been increased, and is obtained by dividing the absorbance (after treatment, the concentrated portion) by the absorbance (initial value). The concentrated volume ratio (%) indicates the ratio of the volume of the concentrated portion to the total volume. The collection rate (%) indicates the ratio of the number of microalgae in the above-described concentration part to the total number of microalgae. As shown in FIG. 10, when green light is used, for example, the concentration is as high as about 9 times, and it can be understood that the microalgae culture solution can be concentrated more efficiently.

<Experiment 4> Experiment on the phototaxis of microalgae in a three-dimensional measuring cylinder (experimental method)
A 200 ml measuring cylinder having a relatively large capacity was used instead of the vial, and an experiment using green light (light having a wavelength of 530 nm) was performed. Since the liquid volume as a whole is larger than in Experiment 3, the sampling interval was increased up to the last 10 ml, and 0.3 ml was sampled every 5.3 ml. Otherwise, it was according to Experiment 3.
(6) Experimental Results FIG. 11 is a graph showing the absorbance of each sample arranged in the sampling order when an experiment was performed in which green light was irradiated from below toward the bottom of a graduated cylinder having a large capacity. As shown in FIG. 11, even in the case of using a graduated cylinder with a large capacity, the sample group near the end in the sampling order shows extremely high absorbance, and the concentrated culture solution is a portion where the concentration of microalgae has increased. It can be seen that is formed. Further, a high value of about 8 times the degree of enrichment was obtained.

20 Concentrator 21 Separation tank (container)
22 Attracting wavelength light irradiation unit 23 Repelling wavelength light irradiation unit 24 Extraction pipe (extraction unit)

Claims

A light irradiation step of irradiating the microalgae culture solution containing microalgae with light having a wavelength that attracts the microalgae,
An extraction step of taking out the portion of the microalgae culture solution in which the concentration of the microalgae is increased by light irradiation;
A method for concentrating a microalgae culture solution, comprising:
At the same time as the irradiation with light having a wavelength that attracts the microalgae, or before or after the irradiation with light having a wavelength that attracts the microalgae, the light having a wavelength that the microalgae repels is the microalgae in the microalgae culture solution. The method for concentrating a microalgae culture solution according to claim 1, wherein irradiation is performed from a side opposite to the side irradiated with light having a wavelength that attracts the algae.
The fine light according to claim 1 or 2, wherein, in the light irradiation step, the light having a wavelength that attracts the microalgae is irradiated to the microalgae culture solution from below the microalgae culture solution. Concentration method of algae culture solution.
The method for concentrating a microalgae culture solution according to any one of claims 1 to 3, wherein the microalgae produce fats and carbohydrates by photosynthesis and accumulate in the cells.
5. The method for concentrating a microalgae culture solution according to any one of claims 1 to 4, wherein the microalgae is Euglena.
6. The method for concentrating a microalgae culture solution according to any one of claims 1 to 5, wherein the light having a wavelength that attracts the microalgae is light containing a wavelength component in a range of 500 nm to 550 nm.
A light irradiation step of irradiating a microalgae culture solution containing microalgae with light of a wavelength that the microalgae avoids;
An extraction step of taking out the portion of the microalgae culture solution in which the concentration of the microalgae is increased by light irradiation;
A method for concentrating a microalgae culture solution, comprising:
A storage section for storing a microalgae culture solution containing microalgae;
An attracting wavelength light irradiating unit that irradiates light of a wavelength that attracts the microalgae to the microalgae culture solution accommodated in the accommodating unit;
An extraction portion for taking out the portion of the microalgae culture solution in which the concentration of the microalgae has been increased by light irradiation;
A device for concentrating a microalgae culture solution, comprising:
Irradiating the microalgae culture solution stored in the storage unit with light having a wavelength that the microalgae repels from a side opposite to a side of the microalgae culture solution that is irradiated with light having a wavelength that induces the microalgae. The apparatus for concentrating a microalgae culture solution according to claim 8, further comprising a repelling wavelength light irradiation unit.