JP6880571B2 - Recovery method and recovery device for microorganisms in aqueous solution using magnetic particles - Google Patents

Description

The present invention relates to a method for recovering microorganisms in an aqueous solution and an apparatus used for the method.

The production of liquid fuels, health foods, pharmaceuticals, cosmetics or animal feeds using biomass is an indispensable technology for sustainable economic development. For example, microalgae, which are a type of microorganism that produces hydrocarbons by photosynthesis, are highly expected due to their high potential production capacity, and various studies have been conducted to produce biomass such as hydrocarbon compounds by culturing microalgae. It has already been done.

For the production of biomass using microalgae, there is a problem that an efficient method for culturing microalgae, a method for recovering microalgae, and a method for extracting biomass such as oil have not been developed, and the cost is high. is there. One of the biggest causes is the lack of an efficient method for recovering microalgae.

Specifically, since microalgae usually grow while floating in a liquid, in order to utilize the microalgae as biomass, it is necessary to recover microalgae having a very dilute concentration from a large amount of liquid. .. In addition, although light energy is required for the growth of microalgae, the concentration of microalgae present in the liquid cannot be excessively increased in order to secure sufficient light irradiation.

As a result, it was necessary to filter a large amount of water in order to recover the microalgae floating in the liquid. In addition, the size of microalgae was generally small, and filtration was not easy. As a study of a recovery method for solving such a problem, a method using a precipitant, a method using a centrifuge, a method of using microalgae as food for a larger organism, and then recovering the large organism, etc. Has been tried, but neither method has led to a fundamental solution.

In addition, due to the eutrophication caused by the supply and accumulation of nutrients in the water area due to domestic wastewater, abnormal growth of algae such as blue-green algae occurs in closed water areas such as lakes and marshes. Such overgrowth of algae impedes the use of the water environment as a place for tap water intake, fisheries, agriculture or tourism. Therefore, a purification technique for efficiently recovering abnormally grown microalgae is required.

So far, a magnetic separation method has been developed in which a non-magnetic substance such as microalgae in water is magnetized to form a magnetic floc, and then the microalgae are separated and recovered from the water by a magnetic separation device (a magnetic separation method). Non-Patent Document 1). This magnetic separation method has advantages such as high-speed separation processing is possible by using a high magnetic field, the device is compact, and no chemical agent is required for physical processing.

Tsuneo Watanabe, "Aiming to Create New Magnetic Separation Engineering", Separation Technology, Vol. 32, No. 5, pp. 274-279 (2002)

However, in the technique of Non-Patent Document 1, it takes time and labor in the process of imparting magnetism to a non-magnetic substance and forming magnetic flocs, and further, the ease of forming magnetite and magnetic flocs is a problem of algae. There is a problem that it is difficult to put it into practical use because the recovery rate changes depending on the type of microalgae, which differs depending on the morphology.

Therefore, an object of the present invention is to provide a method and an apparatus for efficiently recovering microorganisms such as microalgae from an aqueous solution at low cost.

As a result of diligent studies in order to achieve the above object, the present inventor has found a method for recovering microorganisms in an aqueous solution in a uniform system in a short time. That is, the present invention is achieved by the following configuration.

[1] A method for recovering microorganisms in an aqueous solution, which comprises the following steps (1) and (2).
(1) Step of preparing magnetic particles containing microorganisms by adsorption or uptake in an aqueous solution containing microorganisms (2) Step of magnetically separating or filtering the magnetic particles prepared in step (1) [2] In the step (1) The method according to [1], wherein a water-soluble iron salt is added to a microorganism-containing aqueous solution to prepare magnetic particles containing the microorganism.
[3] The method according to [1] or [2], wherein in the step (1), an alkali is added to the aqueous solution containing microorganisms to neutralize the mixture.
[4] The method according to [2] or [3], wherein the water-soluble iron salt is iron chloride, iron sulfate or iron nitrate.
[5] The method according to [4], wherein the water-soluble iron salt is a mixture of ferrous chloride and ferric chloride.
[6] The method according to any one of [1] to [5], wherein in the step (2), a polymer flocculant is added to the microorganism-containing aqueous solution to filter or magnetically separate the magnetic fine particles. Method.
[7] The microorganism produces one or more substances selected from polyunsaturated fatty acids, natural pigments, vitamins, amino acids, minerals, alcohols, hydrogens, sugars, lipids, proteins, fatty acids, organic acids and hydrocarbons. The method according to any one of [1] to [6], which is a microfatty acid.
[8] The microalgae are hydrocarbon-producing microalgae, and the microalgae are at least one alga selected from Aurantiochytrium, Botryococcus braunii, Pseudocorycystis ellipsoidia, and sixolium. The method according to [7], which is a mutant strain or a genetically modified strain of these algae.
[9] Of [1] to [8], the tank is provided with a tank for preparing magnetic particles containing microorganisms, and the tank is provided with a function for automatically filtering or magnetically separating the magnetic particles. A recovery device for recovering microorganisms in the microorganism-containing aqueous solution according to any one.

In the present invention, by preparing magnetic particles in a microorganism-containing aqueous solution, it is possible to produce magnetic particles in which microorganisms are incorporated quickly and efficiently in a uniform system. By filtering or magnetically separating the microorganism-containing magnetic particles thus obtained, the microorganisms can be easily and efficiently separated and recovered from the aqueous solution.

FIG. 1 is a diagram showing a sample before recovery. (Before collection) FIG. 2 is a diagram showing a sample after recovery. (Comparative Example 1) FIG. 3 is a diagram showing a sample after recovery. (Example 1)

The method for recovering microorganisms in an aqueous solution of the present invention is a method for recovering microorganisms in an aqueous solution, which comprises the following steps (1) and (2).
(1) Step of preparing magnetic particles containing microorganisms by adsorption or uptake in a microorganism-containing aqueous solution (2) Step of magnetically separating or filtering the magnetic particles prepared in step (1) Hereinafter, each step will be described.

Process (1)
Step (1) is a step of preparing magnetic particles containing microorganisms by adsorption or uptake in a microorganism-containing aqueous solution. As used herein, the term "magnetic particles containing microorganisms" refers to magnetic particles that have adsorbed or incorporated microorganisms. Microorganisms include microalgae that produce one or more substances selected from polyunsaturated fatty acids, natural pigments, vitamins, amino acids, minerals, alcohols, hydrogen, sugars, lipids, proteins, fatty acids, organic acids and hydrocarbons. , Bacteria or fungi are more preferred, and microalgae producing the substance are even more preferred.

Specifically, as microorganisms, for example, microalgae having the ability to produce astaxanthin, which is a kind of pigment of a natural product [for example, Haematococcus plvialis, Chlorella zofigensis, Chlorella zofigensis, Chlorella zofigensis (for example, Chlorellaccum sp.), Phaffia rhodozima, Monorapidium sp., Etc.], DHA (docosahexaenoic acid) or EPA (eicosapentaenoic acid), which is a kind of highly unsaturated fatty acids. Microalgae [eg, Pinguichrysis sp., Pavlova sp., Haematococcus tricornutum, Nanochloropsis oceanic (Nannochlorpsis sp.), Nanochloropsis, etc. Microalgae to be produced [for example, Astaxanthinum sp., Botryococcus branii, Chlorella sp. ), Isochrysis sp., Nannochloris sp., Nannochloropsis sp., Neochloris oleoabundans, Nitchia spidans, Nitchia sp. -Triconutum (Phaeodactylum tricornutum), genus Astaxanthin (Schizochytrium sp.), Tetraselmis sucica, Pseudocholyssis ssice, siropsis Preferably, the microalgae are astaxanthin, botriococcus brownii, At least one microalgae selected from Pseudocolycystis ellipsoidia and xyzolium, or mutants or genetically modified strains of these microalgae.

Examples of the microorganism-containing aqueous solution include water samples existing in the environment such as river water, lake water, well water, raw tap water, groundwater, sewage, wastewater and park water, and culture solutions of microalgae, bacteria or fungi. Can be mentioned. If necessary, the aqueous solution containing the water-soluble substance may be subjected to pretreatment such as oil-water separation, filtration or pH adjustment.

In the present invention, by preparing magnetic particles in a microorganism-containing aqueous solution, any preparation can be made as long as the magnetic particles containing microorganisms can be prepared by adsorbing or incorporating the microorganisms into the magnetic particles in the process of preparing the magnetic particles. It may be a method.

As a method for preparing magnetic particles containing microorganisms, for example, magnetic particles containing microorganisms can be prepared in the aqueous solution by adding a water-soluble iron salt. In the process of preparing the magnetic particles, it is presumed that the water-soluble iron salt reacts with the microorganisms to obtain magnetic particles containing the microorganisms, and the microorganisms become very large through the preparation process. Efficiently and in a short time, it is adsorbed or incorporated into magnetic particles.

As the water-soluble iron salt, iron chloride, iron sulfate or iron nitrate can be used. As the water-soluble iron salt, a mixture of each divalent and trivalent water-soluble iron salt is preferable, and a mixture of ferrous chloride and ferric chloride is particularly preferable. The amount of the water-soluble iron salt added to the microbial-containing aqueous solution is preferably twice the amount of ferric chloride, more preferably 1.23 times the amount of ferric chloride.

Further, in order to efficiently prepare the magnetic particles, it is preferable to add an alkali to the aqueous solution to neutralize the particles. The timing of adding the alkali to the aqueous solution is not limited, but it is preferably after the raw material compound for producing the magnetic particles is added to the aqueous solution. The alkali is not particularly limited as long as it assists in the formation of magnetic particles, and examples thereof include sodium hydroxide, aqueous ammonia and urea from the viewpoint of economy and handleability. The pH at which the magnetic particles are prepared is preferably 8 or more, more preferably 10 or more. Further, stirring is preferable because the time required for preparing the magnetic particles can be shortened.

Examples of the magnetic particles include magnetic particles such as magnetite, nickel oxide, ferrite, cobalt iron oxide, barium ferrite, carbon steel, tungsten steel, KS steel, rare earth cobalt magnet and hematite.

The magnetic particles are not particularly limited as long as they can be filtered or separated, but from the viewpoint of recovery efficiency, the particle size of the magnetic particles is preferably adjusted to 1 to 10 μm, more preferably 3 to 7 μm.

Process (2)
The step (2) is a step of magnetically separating or filtering the magnetic particles prepared in the step (1). The magnetic particles prepared in the step (1) can be precipitated, aggregated and separated as they are, but the magnetic particles can be quickly and efficiently recovered by filtration or magnetic separation. For magnetic separation, conventionally known methods such as permanent magnets, electromagnets, superconducting magnets or magnetic columns can be used.

Filtration of magnetic particles can be performed by a conventionally known method using a known filter such as an industrial filter paper, a membrane filter, a hollow filter, a cartridge filter, a glass filter paper or a filter plate. The pore size of the filter is not particularly limited, but is preferably 0.2 μm or more in terms of improving the filtration rate and preventing clogging. The upper limit is not particularly limited, but is preferably 1 μm or less in order to prevent recovery leakage during filtration of the generated magnetic fine particles.

Further, in order to increase the speed of magnetic separation or filtration, a polymer flocculant may be added after the preparation of the magnetic particles. The polymer flocculant is not particularly limited as long as it can aggregate the generated magnetic particles, and examples thereof include polyanionic polymer flocculants such as polyacrylic acid.

The concentration of microorganisms in the microbial-containing aqueous solution to which the method of the present invention can be applied is not particularly limited, but can be widely applied to microbial-containing aqueous solutions having a microbial concentration of 1000 ppm to 1 ppm. In the present invention, the microbial concentration (ppm) indicates the mass concentration [(mass of microorganism) / (volume of aqueous solution)].

Further, the temperature and treatment time of each of the step of preparing the magnetic particles containing microorganisms and the step of filtration or magnetic separation in the method of the present invention are not particularly limited, but the temperature is preferably 20 to 100 ° C. It is preferably 50 ° C. to 70 ° C.

Further, although it depends on the concentration of the applied microorganism-containing aqueous solution, the magnetic force of the magnet used for magnetic separation, and the performance of the filter used for filtration, the process of preparing magnetic particles can be completed within 5 minutes by applying the method of the present invention. The time can be significantly shortened, preferably about 2 to 3 minutes, as compared with the conventional method, and even when combined with the filtration or magnetic separation step, it is preferably within 20 minutes, more preferably 10 to 20 minutes. Microorganisms can be separated and recovered to some extent.

After introducing the microbial-containing aqueous solution into the magnetic particle preparation tank, the operation of setting the temperature within the above temperature range in order to generate magnetic particles may be performed before adding the metal salt and alkali, or even during the addition of the metal salt and alkali. Often, it may be after the addition of metal salts and alkalis.

The reaction solution containing the generated magnetic particles can be separated by a separation operation such as centrifugation, but by using filtration or magnetic separation, quick and efficient separation and recovery are possible. For the magnetic separation operation, a known method or apparatus for separating magnetic particles from the reaction solution by using a magnetic force such as a permanent magnet, an electromagnet, or a superconducting magnet can be used.

In addition, the recovery efficiency of microorganisms is 97 to 99.9%, and it is possible to achieve a microbial treatment efficiency superior to that of conventional treatment efficiencies. In addition, the recovered precipitate also changes depending on the concentration of microorganisms, but it is only slightly increased compared to the amount of magnetic particles using the water-soluble iron salt, and the recovery efficiency is significantly improved as compared with the conventional method. can do.

Further, according to the method of the present invention, a high-concentration aqueous solution containing microorganisms is introduced into a magnetic particle preparation tank, magnetic particles containing microorganisms are prepared according to the above method, and then the magnetic particles are automatically filtered or filtered into the tank. By providing a function for magnetic separation, magnetic particles containing microorganisms can be efficiently and automatically recovered and discarded. Further, it is preferable to design the processing apparatus so that the aqueous solution after collecting the magnetic particles can be reused in the process of preparing the magnetic particles.

Specifically, for example, the reaction solution containing the generated magnetic particles is magnetically collected by a magnet installed outside the magnetic particle preparation tank, held in the preparation tank, the reaction solution is discharged, and then the magnet is removed to make the magnetism. A method of recovering particles, a method in which a magnet is placed in a preparation tank, magnetic particles are magnetically collected on the surface thereof, then separated from the reaction solution, and the magnetic particles collected are scraped off from the surface of the magnet to be recovered. Examples thereof include a method in which a reaction solution is passed through a magnetic column placed in a magnetic field, magnetic particles are magnetically collected in the magnetic column, and then the magnetic particles are removed to recover the magnetic particles.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

The concentration of Aurantiochytrium was measured at a measurement wavelength of 403 nm using a UV-1700 PharmaSpec manufactured by Shimadzu Corporation. The water used in this example is purified water having a conductivity of 14.7 MΩcm purified by the pure water production apparatus "Elix UV 35" manufactured by Millipore.

<Example 1>
In a 60 ml sample bottle, 25 ml of oranthiochitrium culture solution (concentration 0.03 wt%, pH: 9.97, obtained from Takasago Thermal Science Co., Ltd.) and ferric chloride / hexahydrate aqueous solution (concentration 17) .3 w / v%) was added in an amount of 0.312 ml, followed by addition of 0.624 ml of an aqueous ferrous chloride / tetrahydrate solution (concentration: 6.4 w / v%), and the mixture was stirred at room temperature at a rotation speed of 300 rpm for 2 minutes. did. 5.5 ml of an 8 w / v% sodium hydroxide aqueous solution was added while continuing stirring, and after the liquid temperature in the water bath reached 60 ° C., stirring was continued for 2 minutes. Then, the stirring was stopped, and Aurantiochytrium was recovered together with the generated magnetic particles with a 4000 G neodymium magnet. The supernatant after collecting the magnetic particles was collected and the transmittance was measured and found to be 100%. The transmittance before recovery was 11.0%.

<Comparative example 1>
Add 25 ml of Aurantiochytrium culture solution (concentration 0.03 wt%, pH: 9.97, obtained from Takasago Thermal Science Co., Ltd.) and 0.05 g of magnetic particles to a 60 ml three-necked flask, and rotate at room temperature. The mixture was stirred at 300 rpm for 2 minutes. Then, the stirring was stopped, and Aurantiochytrium was recovered together with the generated magnetic particles with a 4000 G neodymium magnet. As a result of collecting the supernatant after collecting the magnetic particles and measuring the transmittance, it was 60.4%. The transmittance before recovery was 11.0%.

The results of observing the sample before recovery, the sample of Comparative Example 1 after recovery, and Example 1 after recovery are shown in FIGS. 1 to 3, respectively. As shown in FIGS. 1 to 3, it was visually confirmed that Aurantiochytrium could be recovered with higher efficiency in Example 1 than in Comparative Example 1.

From the above results, it was found that according to the method of the present invention, microorganisms can be efficiently and easily recovered from the aqueous solution.

Claims (6)

( 1) A step of preparing magnetic particles containing microorganisms by adsorption or uptake in a microorganism-containing aqueous solution, and
(2) Including a step of magnetically separating or filtering the magnetic particles prepared in the above step (1).
In the step (1), a water-soluble iron salt is added to the microorganism-containing aqueous solution to prepare magnetic particles containing the microorganism, and
The water-soluble iron salt is a mixture of ferrous chloride and ferric chloride.
A method of recovering microorganisms in an aqueous solution. The method according to claim 1 , wherein in the step (1), an alkali is added to the aqueous solution containing microorganisms to neutralize the mixture. The method according to claim 1 or 2 , wherein in the step (2), a polymer flocculant is added to the microorganism-containing aqueous solution to filter or magnetically separate the magnetic particles. Microorganisms that produce one or more substances in which the microorganisms are selected from polyunsaturated fatty acids, natural pigments, vitamins, amino acids, minerals, alcohols, hydrogen, sugars, lipids, proteins, fatty acids, organic acids and hydrocarbons. The method according to any one of claims 1 to 3. The microalgae are hydrocarbon-producing microalgae, and the microalgae are at least one alga selected from Aurantiochytrium, Botryococcus braunii, Pseudocorycystis ellipsoidia and sixolium, or these algae. The method according to claim 4 , which is a mutant strain or a genetically modified strain. According to any one of claims 1 to 5 , a tank for preparing magnetic particles containing microorganisms is provided, and the tank is provided with a function for automatically filtering or magnetically separating the magnetic particles. A recovery device for recovering microorganisms in the above-mentioned microorganism-containing aqueous solution.

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