JP2018093766A - Method for producing desalted and dried product of microalga belonging to genus aurantiochytrium cultured in culture liquid containing salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a desalted and dried product of microalga belonging to a heterotrophic alga of the genus Aurantiochytrium cultured in a salt-containing culture liquid for the purpose of using the microalga and oils and fats thereof that include useful components as additives, etc., in food and feed by dehydrating and desalting the microalga and culture liquid without extracting and separating the oils and fats that include useful components such as ω-3 fatty acids produced by the microalga.SOLUTION: The production method includes diluting with water the culture medium containing salt and the micro alga belonging to the genus Aurantiochytrium containing oils and fats that include useful components such as ω-3 fatty acids to lower the salt concentration and adding a flocculant, etc., after aggregating and flocking the microalga, dehydration and desalting are carried out, and retained moisture is removed by a drier, to give a desalted dried product.SELECTED DRAWING: Figure 1

Description

  The present invention does not separate fats and oils containing useful components such as polyunsaturated fatty acids such as ω-3 fatty acids produced by microalgae belonging to the genus Aurantiochytrium cultivated in a culture medium containing salt from the microalgae. The present invention relates to a method for producing a desalted and dried product of algae that is intended to be diluted, diluted with dewatered water, dehydrated and desalted, and dried for use in food or feed additives.

Non-Patent Document 1 discloses a heterotrophic microalga, Aulanthiochytrium, which has a high growth rate and produces fats and oils containing useful components such as highly unsaturated fatty acids such as docosahexaenoic acid (DHA). Strains have been reported. Useful ingredients such as DHA as highly unsaturated fatty acids have been reported to be effective in preventing and improving cardiovascular diseases, Alzheimer's disease, depression, etc., and improving health, and are expected to be developed as high-value-added products. Yes.
Patent Document 1 discloses a strain of the genus Aurantiochytrium that has a high growth rate and produces a high concentration of the useful component squalene. Squalene obtained by hydrogenating squalene is expected to expand its use as an additive and stabilizer in cosmetics and pharmaceuticals, and is a squalene of the genus Auranthiochytrium that can produce squalene in a high yield and in a short period of time. Usefulness in production is increasing.

  As described above, non-patent document 1 and patent document 1 produce useful components such as omega-3 fatty acids including docosahexaenoic acid (DHA) at high concentrations in auranthiochytrium strains at a high growth rate. It has been reported that it can be used for various research and development related to the production of oils and fats by culturing microalgae, and for the effective use of bioalgae, foods, cosmetics, pharmaceuticals, feeds, fertilizers, etc. Various research and development related to the use of fats and oils produced by culturing have been conducted.

Patent Document 2 shows a dry alga body and oil production method from a specific strain (JPCC DA0580 strain) of a microalga belonging to the genus Navikura cultivated in a salt-containing culture solution. JPCC DA0580 strain disclosed in Patent Document 2 grows in a culture solution based on seawater and does not grow in fresh water.
In Patent Document 2, a cultured alga body is recovered from a culture solution by a separation / recovery method such as centrifugation or filtration to recover a dried alga body that can be directly used as an oil extraction raw material or as a fuel. A method for removing water from microalgae has been used. In addition, in the production of oil in Patent Document 2, the cultured algal bodies are concentrated and recovered from the culture solution by a separation and recovery method such as centrifugation and filtration, and the recovered algal bodies are organically treated in an undried state or a dried state. A method of recovering oil by extraction using a solvent is used.
Furthermore, in Patent Document 2, it is possible to increase production of oil by further culturing with another culture solution having a reduced concentration of nutrients after culturing microalgae in a culture solution that does not restrict nutrition. Is disclosed.
Therefore, Patent Document 2 discloses a form in which the oil content produced by the microalgae is utilized while being retained in the microalgae, and a form in which the oil content is utilized in a form separated from the microalgae.

Patent Document 3 shows a method for extracting and separating fats and oils from heterotrophic microalgae cultured in a culture solution containing salt. That is, Patent Document 3 shows a form in which fats and oils are utilized in a form separated from microalgae.
Patent Document 4 shows a production system in the case where an extraction residue after extraction of oils and fats produced by microalgae belonging to the genus Euglena is used as an additive for food, feed or fertilizer, and oils and fats are extracted and separated from microalgae. And utilizing the algae residue of the extraction residue.

International Publication No. 2012/077779 International Publication No. 2010/116611 JP 2014-140308 A JP 2014-14284 A

Marine and Biology, Biology and Industrial Application of Labyrinthula, 222, vol. 38, no.1, 2016 (issue date: February 15, 2016), Biological Research Institute

Dry products containing dried alga bodies of microalgae are useful ingredients such as docosahexaenoic acid (DHA) and squalene produced by microalgae as additives such as biofuels, foods, cosmetics, pharmaceuticals, feeds, fertilizers, etc. When it is effectively used as a material for extracting useful components, it is a preferred form from the viewpoint of storage stability and handling properties.
When using dried dried microalgae containing useful components as various additives as they are, extraction and separation of useful components such as oils from algal bodies as disclosed in Patent Documents 2 to 4 is unnecessary. Therefore, it is possible to reduce the manufacturing cost. Moreover, it is possible to prevent the loss of useful components in the extraction of useful components from alga bodies, and to increase the recovery rate of useful components.
On the other hand, in the culture of microalgae, the culture conditions differ according to the habitat environment such as fresh water, brackish water, seawater, etc., and in the production of dried microalgae, the dry conditions according to the culture conditions based on the microalgae habitat environment Setting is required.

When a certain amount of salt is required for high growth rate and high concentration production of useful components, such as the microalgae of the genus Aurantiochytrium, it is difficult to produce dry products from algal cells grown in the culture medium. Salt manipulation is required. In particular, when directly using dried microalgae as additives for food, cosmetics, pharmaceuticals, feed, fertilizers, etc., in addition to ensuring the content of the desired useful ingredients, salt content and unnecessary It is important that the content of these components is reduced.
In the production of a dried product of microalgae that can be cultured in fresh water such as chlorella or a low salinity culture solution, desalting is not necessary in the production of the dried product.
On the other hand, in the case of microalgae cultured in a high salinity culture solution such as Spirulina or Aulanthiochytrium microalgae, desalination treatment is indispensable for expanding the use of the dried product.
Spirulina has a length of alga bodies (single cells) of 300 to 500 μm, can be easily dehydrated by filtration, and can be desalted by dehydration treatment such as filtration.

On the other hand, the microalgae belonging to the genus Aurantiochytrium, which is the subject of the present invention, have a small particle size of several μm to several tens of μm in cultured algal bodies (single cells). When the algal body concentration (dry mass) is increased to 35 g / L to 150 g / L, it is difficult to concentrate and dehydrate from the culture solution, and desalting is also difficult. The chloride ion concentration in the dried algae obtained by evaporating water in this state is 3 to 15% by mass, which is not suitable for uses such as food and feed.
It should be noted that diluting the culture solution of algal cells with water has the potential to kill or collapse algal cells due to changes in osmotic pressure, and is not generally performed.

  An object of the present invention is to dehydrate and desalinate microalgae belonging to the genus Aurantiochytrium that are cultivated in a culture solution containing salt and produce fats and oils containing useful components such as DHA and squalene, without extracting and separating the fats and oils. And providing a method for producing desalted and dried algal bodies that are dried and include dried alga bodies and used for additives such as foods and feeds.

A method for producing a desalted and dried product of microalgae belonging to the genus Aulanthiochytrium that produced an oil and fat containing ω-3 fatty acids according to the present invention capable of achieving the above-mentioned object,
A culture solution containing cultured algae containing a cultured alga of microalga belonging to the genus Aurantiochytrium that produced oils and fats containing ω-3 fatty acids obtained by culturing in a culture solution containing salt A dilution step for obtaining a diluted culture solution by diluting a chloride ion concentration to 6 g / L or less and 1 g / L or more with dilution water without separating the contained fat and oil out of the cultured alga body;
An agglomeration desalting step in which the cultured algal bodies contained in the diluted culture medium are aggregated and flocked by adding a flocculant, and dehydrated and desalted to obtain aggregates containing the cultured algal bodies;
A method for producing a desalted and dried product of microalgae belonging to the genus Aurantiochytrium, comprising a drying step of drying the agglomerates.

  According to the present invention, fine oils containing fats and oils can be obtained without extracting and separating fats and oils containing useful components such as docosahexaenoic acid (DHA) produced by microalgae belonging to the genus Aurantiochytrium cultivated in a culture medium containing salt. Algae can be dehydrated and desalted as it is, and dried to economically produce powdered desalted and dried products such as foods and feed additives.

It is explanatory drawing which shows the structure of the manufacturing method of the desalted dry algal body product which concerns on one Embodiment of this invention. It is explanatory drawing which shows the structure of the manufacturing method of the desalted dry algal body product which concerns on other embodiment of this invention.

In view of the above-described background art and problems, the present inventors have a productization strategy that does not require an extraction / separation step, that is, a use in which microalgae containing oil and fat without extraction / separation is dehydrated, desalted and dried for commercialization. Research and development of development and manufacturing methods have been promoted.
For the purpose of application development, the alga contained in the product does not deteriorate the product quality, the produced fat contains a large amount of useful components with high added value such as omega-3 fatty acids, and impurities that are not suitable for the application In the production of dry products of microalgae belonging to the genus Aurantiochytrium, new knowledge has been obtained that desalting is one of the technically important matters. It was. Furthermore, as described above, the particle size of microalgae belonging to the genus Aurantiochytrium is as small as several μm to several tens of μm, and it is difficult to perform dehydration and desalting only by a separation operation such as filtration. Therefore, as a result of intensive studies to establish a desalination technique in the production of dry products of microalgae belonging to the genus Aurantiochytrium, the present inventors have generally performed treatment of cultured microalgae. Even if the culture solution containing no salt is diluted with water, it can be effectively desalted without affecting the cell morphology of microalgae belonging to the genus Aurantiochytrium, and with water. In addition to the above dilution, a new finding was obtained that further efficiency improvement of the desalting treatment can be achieved by using a coagulation step with a coagulant.
Furthermore, the inventors conducted a verification test of application of dried microalgae belonging to the genus Aurantiochytrium according to the present invention as food to poultry, etc., and completed the present invention.

Patent Document 2 shows that after culturing that does not limit nutrients of microalgae, further culturing is performed with another culture solution in which the concentration of nutrients is reduced. Is intended to increase oil production by limiting nutrients including vitamins, etc., and does not mention the dilution of the same culture medium. The technical problem in Patent Document 2 is to provide a dried product of microalgae useful for biofuels and to provide oil extracted from microalgae, and the desalination treatment associated with the expansion of applications to foods and feeds. It does not suggest any importance.
Although there is a report that agglomeration of algae in a culture solution containing seawater is possible by adjusting the pH, it is not effective for the microalgae targeted by the present invention. Addition of a flocculant that can be achieved quickly and efficiently is suitable.

The method for producing a desalted and dried product of microalgae belonging to the genus Aulanthiochytrium that produces oils and fats containing omega-3 fatty acids according to the present invention has the following steps.
(1) A culture solution containing cultured algae containing a cultured alga of microalga belonging to the genus Aurantiochytrium that has produced fats and oils containing ω-3 fatty acid obtained by culturing in a culture solution containing salt A dilution step of obtaining a diluted culture solution by diluting a chloride ion concentration to 6 g / L or less and 1 g / L or more with diluted water without separating the fats and oils contained in the algal bodies outside the cultured algal bodies.
(2) A coagulation desalting step in which the cultured algal bodies contained in the diluted culture solution are aggregated and flocked by adding an aggregating agent, and dehydrated and desalted to obtain aggregates containing the cultured algal bodies.
(3) A drying step of drying the aggregate.

Hereinafter, embodiments of the manufacturing method according to the present invention will be described.
<Microalgae>
As the microalgae belonging to the genus Aurantiochytrium in the present invention, any microalga can be used without particular limitation as long as it can be used for the production of the intended dry product in the present invention. For example, a strain collected by a conventional method from the natural environment in which such microalgae inhabit, or a strain that can be used for the production of the dry product intended in the present invention can be selected and used from known strains. As strains of such microalgae, the SR21 strain (Accession No. FERM BP-5034) described in Japanese Patent No. 2746572, the Aurantiochytrium / tsukuba-3 strain (Accession No. FERM described in Patent No. 5842197) BP-11442) and other microalgae strains belonging to the genus Aurantiochytrium which are heterotrophic algae.
<Culture conditions>
Proliferation and culture of microalgae belonging to the genus Aurantiochytrium is carried out by seeding the microalgae strain in a culture solution appropriately adjusted with tap water and artificial seawater and culturing according to a conventional method. Any known culture solution can be used. For example, the carbon source is glucose, fructose, etc., the nitrogen source is yeast extract, corn steep liquor, sodium glutamate, ammonium sulfate, etc., and the culture solution can contain vitamins and the like as appropriate, and tap water or seawater in the culture solution Is about 50% by weight.
The culture solution in which the components have been adjusted is appropriately sterilized, and after cooling, the microalgae strain is added and shake culture or aeration and agitation culture is performed at an appropriate temperature of 10 to 30 ° C.

<Manufacture of dry products>
The cultured microalgal algal bodies (cultured algal bodies) are processed into the dry algal body product by the production method shown in FIG. The culture medium containing the cultured algal bodies is mixed with the dilution water without separating the fats and oils produced in the cultured algal bodies outside the cultured algal bodies to prepare a diluted culture liquid. That is, a diluted culture solution is prepared by directly mixing a culture solution containing cultured algal bodies with dilution water.
The chloride ion concentration of the culture solution before mixing with the dilution water varies depending on the culture conditions and is not particularly limited, but is preferably in the range of 6.5 to 14 g / L.
In order to save the amount of diluted water and achieve efficient dehydration and desalting, the solid content concentration in the diluted culture solution is set to 30 g / L or less, and the chloride ion concentration is set to 6 g / L or less and 1 g / L or more. A flocculant is added to the diluted culture solution thus obtained to agglomerate and floc the cultured algal bodies, and dehydrated and desalted with a general dehydrator such as a filtration or a centrifuge. The water containing salt is separated from the aggregate containing the cultured alga by the dehydration treatment, so that the cultured alga is desalted.
When considering the use of food and feed additives for the dried product according to the present invention, a flocculant for food additives such as water-soluble chitosan is preferred.
If the chloride ion concentration is higher than 6 g / L, it becomes a high salt concentration product in which the chloride ion concentration in the dry powder product with a water content of 10% by mass in the next drying step exceeds about 3% by mass. It is not preferable. Further, diluting the chloride ion concentration to be lower than 1 g / L is not economical because the amount of diluted water and drainage is large. The chloride ion concentration of the dilution water may be 200 mg / L or less of the water supply standard.

Aggregates containing cultured algal bodies obtained by the agglomeration desalting step become solids containing water of about 90% by mass or less as water content, and are supplied to the drying step as the next step. Depending on the treatment conditions in the coagulation desalting step, for example, a wet solid having a water content of about 80 to 90% by mass can be obtained by the coagulation desalting step.
In the drying process, drying apparatuses having various configurations can be used. The drying device may be a general device such as a spray dryer or a disk-type drying device. For medium and small scales, a disk-type drying apparatus is preferred which has a small amount of drying air and can easily condense and recover evaporated water.
In the case where the agglomerates as solids are made to have fluidity and are supplied to the drying device, an appropriate amount of water can be mixed with the solids to impart fluidity to the solids and then supplied to the drying device. . Furthermore, the water evaporated in the drying apparatus may be collected by a condenser, and the collected condensed water may be used for addition to a solid as necessary. Furthermore, the condensed water collected in the drying step may be reused for dilution of the culture solution containing cultured algal bodies.
The above-mentioned reuse of condensed water contributes to the reduction of dilution water and drainage.
According to the present invention, a dry powdered product containing dried microalgae having a chloride ion concentration of 0.5 to 3% by mass and a water content of about 10% by mass can be obtained.
In order to further reduce the chloride ion concentration in the dried product, the agglomerate obtained in the agglomeration desalting step is diluted again with dilution water to reduce the chloride ion concentration to less than 1 g / L, and then dehydrated and desalted again. By adding the dehydration desalting step to be performed, the chloride ion concentration of the dried algal product can be reduced to 0.6% by mass or less with a small amount of dilution water. This dehydration and desalting step may be repeated a plurality of times as necessary.

  In order to reduce the amount of waste water and dilution water, as shown in the block diagram of the manufacturing method in FIG. 2, the residual solid content and salt content in the dewatered waste water are removed from the microfiltration membrane (MF membrane) and reverse osmosis membrane (RO membrane). It can be removed by membrane separation treatment such as treatment by collecting the desalted water having a chloride ion concentration of 200 mg / L or less, and can be reused as the dilution water. A part of the treated water obtained by the fine solid content removal film such as the MF film can be used as a cleaning liquid for back washing of the fine solid content removal film such as the MF film. The portion where the salt content by the treatment with the reverse osmosis membrane is concentrated is sent to the wastewater treatment together with the backwash wastewater of the fine solid content removal membrane such as the MF membrane.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, each measured value in the following examples is a value obtained by a conventional method.
Example 1
<Culture and harvest>
A solution containing 20 g of glucose per liter, 10 g of polypeptone, and 5 g of yeast extract is sterilized at 130 ° C. for 15 minutes, cooled to 25 ° C., mixed with filtered seawater and tap water, A pre-cultured solution containing a microalgae strain belonging to the genus Aurantiochytrium is added to a culture solution adjusted to a seawater ratio of about 50% by mass, and sterilized glucose and sodium glutamate aqueous solution at 25 ° C. for 4 days. While adding appropriately, it culture | cultivated by aeration agitation with the sterilized air.
Microalgae strains belonging to the genus Aurantiochytrium include the SR21 strain (Accession No. FERM BP-5034), the Aurantiochytrium tsukuba-3 strain (Accession No. FERM BP-11442), etc. A strain selected from strains of microalgae belonging to the genus Aurantiochytrium of the nutritional algae can be used.
The cultured broth was about 60 g of algal body concentration (dry mass) per liter, the amount of fat and oil containing DHA and the like was 20 to 30% by mass of the dry mass of algal body, and the chloride ion concentration was 9 g / L. The size of the microalgae was 5 to 40 μm, and the volume average particle size was 10.4 μm.
Since the cultured microalgae have a very fine particle size and a high microalgae concentration, the chloride ion concentration is 3.8 g / L, and the solid content concentration including the microalgae is about 25 g / L. Thus, it was difficult to dehydrate and concentrate the microalgae by filtration using the culture solution containing the microalgae to which dilution water was added. Therefore, Fuji Clean KT-250 (trade name, Fuji Engineering Co., Ltd.) is added as a flocculant for food additives, and the microalgae are agglomerated and flocked and dehydrated, desalted and concentrated by filtration (first dehydration). did.
(Dry)
The water content in the solid comprising the aggregate containing the dehydrated desalted and concentrated microalgae was 85% by mass, and the chloride ion concentration was 0.33% by mass. An appropriate amount of water was added thereto, and the microalgae (dry mass) was made into a flow state of about 50 g / L and supplied to the drying apparatus. In the stage where the condensed water evaporated by the drying apparatus and recovered by the condenser can be used, condensed water was used as water for obtaining the fluidity of the solid matter.
In the drying device, the water content was evaporated in a disk-type drying device using 0.5 MPaG of water vapor as the heat source for the microalgae to obtain a dry powder product having a water content of about 10% by mass. The chloride ion concentration in the dry powder product was about 1.9% by mass.

In order to obtain a dried product with a further reduced chloride ion concentration, the above-mentioned dehydrated and desalted / concentrated water content of 85% by mass is returned to the re-diluted solid in FIG. As shown in the route, once again diluted with diluted water to an algal mass concentration of 25 g / L and chloride ion concentration of 0.55 g / L, filtered again, dehydrated, desalted and concentrated (second dehydration), A solid substance composed of aggregates containing microalgae at a rate of 85% by mass was obtained.
The chloride ion concentration in this solid matter is 0.05% by mass, and this is added to the drying device in the same manner as described above by adding condensed water from the drying device so that the mass concentration of the algal bodies is 50 g / L. A dried powdery algal product having a water content of about 10% by mass was obtained. The chloride ion concentration in this product after repeated dilution and dehydration desalting operations was 0.28% by mass.

(Example 2)
In the same manner as in Example 1, culture, dilution / adjustment, dehydration desalting, and drying were performed to obtain a desalted and dried algal body product. The solid content of residual microalgae and the like in the dewatered wastewater separated in the dewatering process is about 3 g / L in the first and second dewatered wastewater, and the chloride ion is about 3.8 g / in the first dewatered wastewater. L, about 0.6 g / L was contained in the second dewatered waste water. As shown in FIG. 2, after removing the solid content in the wastewater with an MF membrane, it was treated with a reverse osmosis membrane to reduce the chloride ion concentration to about 150 mg / L. About 60% by mass of the second drainage was collected and reused as dilution water.

Claims (4)

A method for producing a desalted and dried product of microalgae belonging to the genus Aurantiochytrium that produced an oil containing omega-3 fatty acids,
A culture solution containing cultured algae containing a cultured alga of microalga belonging to the genus Aurantiochytrium that produced oils and fats containing ω-3 fatty acids obtained by culturing in a culture solution containing salt A dilution step for obtaining a diluted culture solution by diluting a chloride ion concentration to 6 g / L or less and 1 g / L or more with dilution water without separating the contained fat and oil out of the cultured alga body;
An agglomeration desalting step in which the cultured algal bodies contained in the diluted culture medium are aggregated and flocked by adding a flocculant, and dehydrated and desalted to obtain aggregates containing the cultured algal bodies;
A method for producing a desalted and dried product of microalgae belonging to the genus Aurantiochytrium, comprising a drying step of drying the agglomerates.   The production method according to claim 1, wherein the agglomerate is diluted again with dilution water to a chloride ion concentration of less than 1 g / L, and the agglomerate obtained by dehydration and desalting is supplied to the drying step.   The production method according to claim 1 or 2, wherein the flocculant is for food additives.   The manufacturing method of any one of Claims 1 thru | or 3 which reuses the condensed water obtained by condensing the water vapor | steam which generate | occur | produces at the said drying process as said dilution water.

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