particle

Abstract

To provide a particle that is an autonomic submersible particle capable of causing a large movement behavior in a direction intersecting with a vertical direction when floating up and sinking down in the vertical direction between a liquid level and a liquid bottom in an aqueous medium.SOLUTION: A particle floats up and sinks down in an aqueous medium, and includes microorganism that generates gas and / or an aqueous medium-insoluble liquid by organic activity, a material that generates gas and / or an aqueous medium-insoluble liquid by assimilation of the microorganism, and cellulose nanofiber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to particles that autonomously float and sink in an aqueous medium. [Background technology]

[0002] In recent years, pollutant removers capable of adsorbing and removing environmental pollutants have been used for the purpose of environmental purification (e.g., water purification), and the use of particles that autonomously float and sink in an aqueous medium (hereinafter also referred to as "autonomous floating-sinking particles") as such pollutant removers has been considered.

[0003] For example, Patent Document 1 discloses, as autonomous floating / sinking particles, autonomous floating / sinking gel beads containing microorganisms that generate gas through biological activity and assimilated substances for the microorganisms. When the gel beads of Patent Document 1 are administered into an aqueous medium, they initially sink to the bottom of the liquid, but after a while, the gas and / or aqueous-medium-insoluble liquid generated by the biological activity of the microorganisms in the gel beads acts as a float, causing the gel beads to rise to the aqueous medium-air interface (hereinafter also referred to as the "liquid surface"). Meanwhile, since the liquid pressure near the liquid surface is smaller than that at the liquid bottom, the gas and / or aqueous-medium-insoluble liquid in the gel beads is released outside the gel beads as the gel beads rise to the liquid surface. As a result, the gel beads that have lost their float sink again due to their own weight. The gel beads repeat the above-mentioned floating and sinking in the aqueous medium, and after the nutrient substances are consumed by the assimilation of the microorganisms and their specific gravity becomes smaller than that of the aqueous medium, they rise to the liquid surface and are then collected. Furthermore, Patent Document 1 discloses gel beads containing an adsorbent and a method for purifying pollutants using the gel beads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-137442 A Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, studies are being made to improve the efficiency of environmental purification by making the movement of autonomous floating-sinking particles in an aqueous medium more complex. Specifically, attempts are being made to produce autonomous floating-sinking particles that not only repeat vertical floating and sinking between the liquid surface and the liquid bottom in an aqueous medium (hereinafter also referred to as "up-down movement"), but also move in a direction intersecting the vertical direction when floating and sinking between the liquid surface and the liquid bottom in an aqueous medium (hereinafter also referred to as "left-right movement"). The inventors prepared and examined the autonomous floating-sinking particles described in Patent Document 1 and found that, although they observed floating-sinking (up-and-down movement) behavior in the vertical direction between the liquid surface and the liquid bottom in an aqueous medium, they hardly observed movement behavior in a direction intersecting the vertical direction (side-to-side movement). Therefore, an object of the present invention is to provide an autonomous floating / sinking particle which, when floating and sinking in the vertical direction between the liquid surface and the liquid bottom in an aqueous medium, can exhibit large movement behavior in a direction intersecting the vertical direction. [Means for solving the problem]

[0006] The present inventors have found that the above problems can be solved by the following configuration.

[0007] [1] Particles that float and sink autonomously in an aqueous medium, A microorganism that produces gas and / or an aqueous medium-insoluble liquid through biological activity; A substance that is assimilated by the microorganism to produce a gas and / or an aqueous medium-insoluble liquid; A particle comprising: cellulose nanofibers. [2] The particle according to [1], further comprising a binder polymer. [3] The particles according to [2], wherein the binder polymer is at least one selected from the group consisting of gel-like substances and polymeric compounds. [4] The particles according to any one of [1] to [3], wherein the content of the cellulose nanofibers is 0.5 to 8 mass % based on the total mass of the particles excluding the solvent. [5] The particles according to any one of [1] to [4], wherein the mass content ratio of the microorganism to the cellulose nanofiber is 0.4 to 10. Effect of the Invention

[0008] According to the present invention, it is possible to provide autonomous floating / sinking particles which, when floating and sinking in the vertical direction between the liquid surface and the liquid bottom in an aqueous medium, can exhibit large movement behavior in the direction intersecting the vertical direction. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram for explaining the behavior of the particles of the present invention in an aqueous medium. [Diagram 2] FIG. 1 is a schematic diagram for explaining the behavior of particles in an aqueous medium according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0011] In addition, in this specification, unless otherwise specified, each component may be used alone or in combination of two or more substances corresponding to each component. Here, when two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.

[0012] [particle] The particles of the present invention are Particles that autonomously float and sink in an aqueous medium, A microorganism (hereinafter also abbreviated as "microorganism") that produces gas and / or aqueous medium insoluble liquid through biological activity; A substance that is assimilated by the microorganism to produce a gas and / or an aqueous medium-insoluble liquid (hereinafter also referred to as "assimilable substance"); and cellulose nanofiber (CNF).

[0013] The present inventors have now demonstrated that the problems of the invention can be solved by using particles having the above structure. In the following, the presumed mechanism of action of the particles will first be explained.

[0014] The particles are particles that can autonomously float and sink in an aqueous medium without requiring external assistance such as stirring (autonomous floating-sinking particles).

[0015] The particles contain microorganisms that generate gas and / or aqueous medium-insoluble liquid through biological activity, a substance that is assimilated by the microorganisms, and cellulose nanofibers. Note that the particles often also contain a matrix component (e.g., a binder polymer). When particles are administered into an aqueous medium having a lower specific gravity than the particles, they will initially sink, but after a while, gas and / or aqueous-medium-insoluble liquid will be generated inside the particles due to the process of biological activity of the microorganisms (for example, when the microorganism is a yeast fungus and the nutrient is a sugar such as glucose, carbon dioxide will be generated as a gas), and this gas and / or aqueous-medium-insoluble liquid will act as a float, causing the particles to rise to the aqueous medium-air interface (liquid surface). Since the liquid pressure is lower near the liquid surface compared to the bottom of the liquid, the volume of the gas and / or aqueous-medium-insoluble liquid generated within the particles will gradually increase due to the decrease in liquid pressure associated with the rise, and some of it will be released from the particles and adhere to the particles. It is believed that the gas and / or aqueous-medium-insoluble liquid attached to the particles acts as a float. When the particles rise to the liquid surface, the gas and / or aqueous-medium-insoluble liquid within the particle, as well as the gas and / or aqueous-medium-insoluble liquid attached to the particle, are released from the particle. As a result, the particle that has lost its floating ability settles again due to its own weight. The particle repeats a vertical floating-sinking (up-and-down movement) behavior between the liquid surface and the liquid bottom in the aqueous medium, and after the assimilated substances are consumed by the microorganisms and the specific gravity of the particle becomes smaller than that of the aqueous medium, the particle floats to the liquid surface. The present inventors' recent investigations have revealed that the above-mentioned particles containing cellulose nanofibers, when they float and sink (up and down movement) in the vertical direction between the liquid surface and the liquid bottom in the above-mentioned aqueous medium, also exhibit large movement (side-to-side movement) in a direction intersecting the above-mentioned vertical direction. In other words, the above-mentioned particles repeat the vertical floating and sinking (up and down movement) behavior between the liquid surface and the liquid bottom in the aqueous medium while exhibiting side-to-side shaking. Fig. 1 is a schematic diagram for explaining the behavior of the above-mentioned particles in an aqueous medium. As shown in Fig. 1, a particle 1 repeatedly rises and sinks in a vertical direction L (direction of the arrow) between the liquid surface 5a and the liquid bottom 5b of an aqueous medium 5, but by swaying from side to side when rising and sinking, the particle traces a non-linear trajectory T1 between the liquid surface 5a and the liquid bottom 5b. In contrast, in the case of particles of the prior art, as shown in Fig. 2, when a particle 11 repeatedly rises and sinks in the vertical direction L (direction of the arrow) between the liquid surface 5a and the liquid bottom 5b of an aqueous medium 5, the particle traces a trajectory T1 that is approximately parallel to the vertical direction L without swaying side to side. 11 As a result of the above, for example, when the particles are applied to a pollutant removing agent for purifying a solution containing a component to be removed, it is presumed that the migration distance in an aqueous medium is increased and the purification efficiency is improved.

[0016] [Particle shape] The shape of the particles is not particularly limited, and examples thereof include spherical, plate-like, needle-like, etc. Note that the term "spherical" as used herein includes not only a perfect sphere, but also spheroids, ovals, and other shapes. The average particle size of the particles is not particularly limited, but is preferably 1 cm or less, more preferably 0.6 cm or less, even more preferably 0.1 cm or less, particularly preferably 500 μm or less, and most preferably 200 μm or less. The lower limit is, for example, 50 μm or more. The average particle size is a value obtained by measuring the major axis of 10 or more particles and calculating the arithmetic average.

[0017] [Microorganisms] The particles include microorganisms that produce gas and / or liquid that is insoluble in aqueous media through biological activity. The biological activity of microorganisms is not particularly limited, and examples thereof include metabolism, decomposition, and photosynthesis by microorganisms. The type of gas generated by the biological activity of microorganisms is not particularly limited, and examples thereof include carbon dioxide, oxygen, hydrogen, nitrogen, methane, etc. The type of aqueous medium-insoluble liquid generated by the biological activity of microorganisms is not particularly limited, and examples thereof include hydrocarbon compounds, etc.

[0018] The microorganism is not particularly limited, but examples thereof include yeast, enterobacteria, lactic acid bacteria, aerobic spore-forming bacteria, anaerobic bacteria, mold (for example, Aspergillus oryzae), algae, and plankton. Among the above microorganisms, yeast, enterobacteria, and lactic acid bacteria can mainly produce carbon dioxide through fermentation. Additionally, some aerobic spore-forming bacteria and anaerobic bacteria can produce primarily carbon dioxide and / or hydrogen through fermentation. Koji mold can decompose starch (starch can be a nutrient or a weighting material, as described below) through saccharification to produce carbon dioxide.

[0019] Algae can produce oxygen through photosynthesis or respiration, and one type of algae, Cyanobacteria, in particular, can also produce hydrogen. In addition, algae belonging to the genus Aurantiochytrium produce a hydrocarbon compound (squalene, which is equivalent to terpenoid oil) as an insoluble liquid in aqueous media. HD-1 strain (Oleomonas sagaranensis) also produces petroleum as an insoluble liquid in aqueous media under anaerobic conditions.

[0020] Plankton can produce carbon dioxide through photosynthesis or feeding. Among these, microorganisms belonging to the genus Saccharomyces are preferred. Microorganisms belonging to the genus Saccharomyces include Saccharomyces bayanus, Saccharomyces boulardii, Saccharomyces bulderi, Saccharomyces cariocanus, Saccharomyces cariocus, Saccharomyces cerevisiae, Saccharomyces chevalieri, Saccharomyces dairenensis, Saccharomyces ellipsoideus, Saccharomyces florentinus, Saccharomyces kluyveri, Saccharomyces martiniae, Saccharomyces monacensis, Saccharomyces norbensis, Saccharomyces paradoxus, Saccharomyces pastorianus, Saccharomyces spencerorum, Saccharomyces turicensis, Saccharomyces unisporus, Saccharomyces uvarum, or Saccharomyces zonatus is more preferred. Saccharomyces cerevisiae is more preferred since it is relatively easy to obtain and has a higher carbon dioxide production capacity.

[0021] The above microorganisms may be used alone or in combination of two or more kinds. The content of the microorganisms in the above particles (the total amount when multiple types of microorganisms are contained) is not particularly limited, but is preferably 1 to 20 mass %, more preferably 1 to 10 mass %, based on the total mass of the particles excluding the solvent. In this specification, the term "total mass of particles excluding solvent" means the total content of components other than the solvent when the particles contain a solvent, and means the total mass of the particles when the particles do not contain a solvent.

[0022] [Assimilated substances] The particles contain a substance that is assimilated by the microorganism to produce a gas and / or an aqueous medium-insoluble liquid, i.e., the particles contain an assimilated substance that produces a gas and / or an aqueous medium-insoluble liquid as a result of being assimilated by the microorganism. The assimilated substance is appropriately selected depending on the type of microorganism. The microorganism produces gas through assimilation. When the microorganism is a yeast fungus, the assimilated substance can be, for example, a sugar such as glucose, or a mixture of starch, which is a raw material for the sugars such as glucose, and an enzyme that breaks down starch to produce the sugars. When the microorganism is a lactic acid bacterium, examples of the assimilated substances include glucose and starch. When the microorganism is koji mold, examples of the assimilated substances include solid organic matter such as starch and cellulose. When the microorganism is a mold, the mold is preferably supported on a solid organic matter. When the microorganism is an alga, examples of the assimilated substances include organic acids, alcohols, vitamins, and nutrients. When the microorganism is plankton, examples of the assimilated substances include phytoplankton and nutrients.

[0023] The above nutrient substances may be used alone or in combination of two or more kinds. The content of nutrient substances in the above particles (the total amount of nutrient substances when multiple types of nutrient substances are contained) is not particularly limited, but is preferably 1 to 80 mass %, more preferably 5 to 65 mass %, and even more preferably 5 to 60 mass %, relative to the total mass of the particles excluding the solvent. The microorganisms in the particles can also utilize substances present in the external environment as nutrient substances, and therefore the particles may be configured to contain a minimum amount of nutrient substances.

[0024] [Cellulose nanofiber] The particles include cellulose nanofibers. Cellulose nanofibers can be obtained, for example, by defibrating raw pulp. Examples of raw pulp for cellulose nanofiber include wood pulp made from broadleaf and coniferous trees; non-wood pulp made from straw, bagasse, cotton, hemp, and bast fibers; and deionized paper pulp (DIP) made from recycled waste paper and broke paper. The raw material pulp constituting the cellulose nanofibers may be one type alone or two or more types in combination.

[0025] Methods for defibrating cellulose nanofibers include physical treatments in which the raw pulp is defibrated using a defibrating device such as a high-pressure homogenizer, and chemical treatments in which the raw pulp is defibrated by hydrolysis using an enzyme (e.g., cellulase, etc.) or an acid and / or an oxidation reaction using an oxidizing agent. When defibrating cellulose nanofibers using the above-mentioned physical treatments, it is also preferable to carry out the above-mentioned chemical treatments prior to defibrating the cellulose nanofibers.

[0026] The average fiber diameter of the cellulose nanofibers (average diameter of single fibers) is not particularly limited, but is preferably, for example, 10 to 500 nm, more preferably 15 to 450 nm, and even more preferably 20 to 400 nm. The average fiber diameter of the cellulose nanofibers can be appropriately adjusted, for example, by the type of raw pulp and the defibration method.

[0027] The average fiber length (single fiber length) of the cellulose nanofibers is not particularly limited, but is, for example, preferably from 0.3 to 2000 μm, more preferably from 0.4 to 200 μm, and even more preferably from 0.5 to 20 μm.

[0028] The cellulose nanofibers may be used alone or in combination of two or more types. The content of cellulose nanofibers in the above particles (the total amount when multiple types of cellulose nanofibers are included) is not particularly limited, but in terms of better effects of the present invention, it is preferably 0.1 to 10 mass%, more preferably 0.5 to 8 mass%, and even more preferably 0.5 to 5 mass%, relative to the total mass of the particles excluding the solvent. Furthermore, in the above particles, the mass content ratio of microorganisms to cellulose nanofibers (microorganism content / cellulose nanofiber content) is not particularly limited, but in terms of superior effects of the present invention, it is preferably 0.1 to 30, more preferably 0.1 to 25, and even more preferably 0.4 to 10. In addition, in the above particles, the mass content ratio of the matrix component to the cellulose nanofiber (matrix component content / cellulose nanofiber content) is not particularly limited, but in terms of superior effects of the present invention, it is preferably 10 to 60, more preferably 15 to 50, and even more preferably 15 to 45.

[0029] [Matrix components] The particles may include a matrix component. The matrix component is not particularly limited as long as it is a component capable of holding the microorganisms and the nutrient substances, and examples thereof include binder polymers. Examples of the binder polymer include gel-like substances and polymeric compounds, etc. The polymeric compounds mentioned here do not include gel-like substances. The form of the gel-like material is preferably a physical gel or a chemical gel. Here, the term "physical gel" refers to a gel formed by crosslinking polymers through hydrogen bonds, ionic bonds, chelate formation, etc., while the term "chemical gel" refers to a gel formed by crosslinking polymers through covalent bonds. The binder polymer is preferably hydrophilic.

[0030] Examples of the above-mentioned gel-like substances (physical gels, chemical gels) include gels of gel precursor components selected from the group consisting of fatty acids, natural oil-based fatty acids, 12-hydroxystearic acid, β-lactoglobulin, hyaluronic acid, alginic acid, chitosan, carboxymethylcellulose, polylactic acid, and polyethylene glycol; ionic liquid / polydimethylsiloxane (IL / PDMS) gels; silica gels; silicone gels; gels of gel precursor components selected from the group consisting of polymethacrylic acid, polyhydroxyethyl methacrylate, polyacrylamide, poly(N-isopropylacrylamide), polyvinyl methyl ether, polyrotaxane, and gelatin; and the like.

[0031] The method for gelling the above-mentioned gel precursor components can be appropriately selected depending on each gel precursor component used. For example, gelation of alginic acid can be carried out by mixing an aqueous solution in which alginic acid and / or an alginate is dissolved with a metal salt. The metal species of the metal salt used for gelation is not particularly limited, but is preferably, for example, calcium, iron, manganese, or zinc, more preferably calcium or iron, and even more preferably calcium.

[0032] Examples of the polymer compound include highly water-absorbent resins and ion-exchange resins. The highly water-absorbent resin may be a resin containing repeating units derived from hydrophilic monomers such as N,N-dimethylacrylamide and N-vinylpyrrolidone. The ion exchange resin includes resins containing repeating units derived from styrene or divinylbenzene.

[0033] The polymer binder is preferably a material that easily releases gas produced by the microorganisms or aqueous medium-insoluble liquid to the outside of the polymer binder, and is more preferably a gel-like material.

[0034] The matrix components may be used alone or in combination of two or more.

[0035] 〔solvent〕 When the particles contain a matrix component, the particles preferably further contain a solvent. The solvent includes water and organic solvents, with water being preferred. Water has the functions of being used for the biological activities of microorganisms, dissolving gases generated by microorganisms and discharging the gas outside the matrix component, and also transporting substances (including nutrient substances) taken into the matrix component from the outside world while retaining nutrient substances within the matrix component.

[0036] The content of the solvent in the particles (the total amount when multiple types of solvents are contained) is not particularly limited, but is preferably 0.01 to 10% by mass based on the total mass of the matrix components.

[0037] [Other ingredients] <Weights and floats> The particles may further comprise other ingredients, such as weighting materials and flotation materials. The weighting material refers to a component that serves as a weight immediately after the particles are administered to an aqueous medium and that can be dissolved in the aqueous medium while the particles are repeatedly floating and sinking, or a component that serves as a weight immediately after the particles are administered to an aqueous medium and that can be assimilated by microorganisms. Weighting materials include, for example, calcium carbonate, magnesium carbonate, glucose, starch, glycerol, and maltose. The floating agent is a component that can act as a float during the floating / sinking process of the particles in the solution, and an example of this is sodium bicarbonate.

[0038] <Other ingredients not listed above> The particles may further include components other than the weighting material and the floating material. Components other than the weight material and the floating material can be set appropriately depending on the application, and examples include adsorbents, feed, pharmaceuticals, ion exchangers, luminescent materials, magnetic materials, organisms, cells, and measuring elements (sensors).

[0039] [Method of producing particles] The method for producing the particles is not particularly limited. Hereinafter, the method for producing particles will be described by taking an example of a method for producing particles containing alginate gel as a matrix component. First, a composition is prepared that contains microorganisms, nutrient substances, cellulose nanofibers, gel precursors such as alginic acid and alginates, a solvent, and other components that are added as needed. Next, a solution containing a solvent and a metal salt (e.g., calcium chloride) capable of generating metal ions capable of gelling alginic acid and alginates is dropped into this composition using a pipette. As a result, gelation of alginic acid and alginates occurs, and gel-like particles containing microorganisms, nutrient substances, and cellulose nanofibers are obtained. In preparing a composition containing microorganisms, nutrient substances, cellulose nanofibers, gel precursors such as alginic acid and alginates, a solvent, and other components that are added as needed, it is preferable that the cellulose nanofibers are prepared in advance as a dispersion in an aqueous medium (preferably water). In other words, the composition is preferably prepared by mixing the dispersion with a composition containing microorganisms, nutrient substances, gel precursors such as alginic acid and alginates, a solvent, and other components that are added as needed. The dispersion liquid may also contain other components, such as components that can be used as nutrient substances in the particles, and preferably sugars (e.g., glucose). In terms of achieving superior effects of the present invention, it is preferable to prepare the dispersion by mixing a dispersion obtained by defibrating a composition containing raw pulp, a nutrient substance, and an aqueous medium with a high-pressure homogenizer with a composition containing microorganisms, a gel precursor such as alginic acid and an alginate salt, a solvent, a nutrient substance, and other components which are optionally added.

[0040] [Particle Uses] <Autonomous floating and sinking behavior> When the particles are added to an aqueous medium, they autonomously repeat floating and sinking (floating and sinking). During this floating and sinking behavior, the particles not only float and sink vertically between the liquid surface and the liquid bottom (up-and-down movement), but also move significantly in a direction intersecting the vertical direction (side-to-side movement).

[0041] The aqueous medium is not particularly limited, and examples thereof include water, an aqueous solution containing a solute, an aqueous dispersion containing a dispersoid, and an aqueous dispersion containing a solute and a dispersoid. The specific gravity of the aqueous medium is smaller than that of the particles. The specific gravity of the aqueous medium can be appropriately determined in consideration of the type and content of the microorganisms in the particles, the period of autonomous floating and sinking, etc. The specific gravity of the aqueous medium is preferably 0.55 times or more, more preferably 0.65 times or more, even more preferably 0.75 times or more, particularly preferably 0.80 times or more, preferably 0.95 times or less, more preferably 0.94 times or less, even more preferably 0.93 times or less, and particularly preferably 0.91 times or less, relative to the specific gravity of the particles.

[0042] From the viewpoint of suppressing biological activity of microorganisms, the above particles are preferably stored by refrigeration, freezing, or freeze-drying until they are added to an aqueous medium.

[0043] The particles can be separated and recovered from the aqueous medium after the autonomous floating and sinking in the aqueous medium has ended or during this process.

[0044] The use of the particles is not particularly limited, but for example, they can be used in the purification treatment of a solution containing a component to be removed. When the particles are used for purification treatment of a solution containing a component to be removed, it is preferable that the particles further contain a component capable of physically or chemically removing the component to be removed (for example, a component capable of adsorbing and removing the component to be removed (specifically, an adsorbent and an ion exchanger, etc.). Prussian blue is known as an adsorbent capable of adsorbing cesium). The particles can remove the component to be removed from the aqueous medium while autonomously floating and sinking in the aqueous medium.

[0045] The particles can also be used as a material for supplying feed, medicines, etc. to fish. When the particles are used as a material for supplying feed, medicines, etc. to fish, the particles preferably further contain feed and / or medicines for fish. The particles can be ingested by fish in an aqueous medium while autonomously floating and sinking in the aqueous medium, thereby supplying feed and / or medicines to the fish.

[0046] The particles can also be used as lighting devices or toys. When the particles are applied as a lighting device or a toy, the particles preferably further contain a light-emitting material and / or a magnetic material. The particles can be used as a lighting device or a toy that emits light or gathers at a predetermined location by a chemical reaction and / or a stimulus from the outside world while autonomously floating and sinking in an aqueous medium supplied to an aquarium.

[0047] Additionally, by incorporating sensors into the particles, the particles may be used as devices or terminals capable of recording physical or chemical changes in the aqueous medium. EXAMPLES

[0048] The present invention will be described in more detail below based on examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0049] [Preparation of cellulose nanofiber (CNF)-containing dispersion] A CNF-containing dispersion was prepared by the following procedure. (1) Pure water, CNF (product name "Decolorized Bamboo Pulp", Earth Recycle Co., Ltd.), and glucose (product name "D(+)-Glucose Wako Grade 1", Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed in a mass ratio of 65 / 5 / 30 and stirred at 8000 RPM for 15 minutes using an Ace Homogenizer AM-9 manufactured by Nippon Seiki Seisakusho Co., Ltd. (2) The stirred liquid obtained in step (1) was dispersed using an ultra-high pressure homogenizer NAGS20 manufactured by Tokoh Co., Ltd. under conditions of a pressure of 200 MPa and a number of passes of 5 passes to obtain a CNF-containing dispersion (CNF dispersion containing 30% glucose by mass). The obtained CNF-containing dispersion was used for producing autonomous floating / sinking particles 1 to 3 (Examples 1 to 3) described below.

[0050] [Production of Comparative Autonomous Floating-Sinking Particles R1 and 1] [Comparative Example 1: Production of Comparative Autonomous Floating-Sinking Particles R1] (1) Preparation of alginic acid solution To 50 g of a 1% by mass aqueous solution of sodium alginate (product name "Sodium Alginate 500-600 cP", Fujifilm Wako Pure Chemical Industries, Ltd.), 15 g of glucose (product name "D(+)-Glucose", Fujifilm Wako Pure Chemical Industries, Ltd.) and 2 g of dry yeast (product name "Super Camellia", Nisshin Foods Inc.) were added and stirred with a stirrer on ice for 10 minutes to obtain an aqueous solution of alginic acid. (2) Production of CNF-free alginate gel particles 5 g of 30% by mass glucose aqueous solution was added to 45 g of the alginic acid aqueous solution obtained in step (1) and stirred in ice for 10 minutes. Next, the above-mentioned stirred solution was dropped into 200 mL of 5% by mass calcium chloride aqueous solution with a pipette to produce gel particles (comparative autonomous floating-sinking particles R1) with a diameter of about 5 mm.

[0051] [Example 1: Production of autonomous floating / sinking particles 1] In the above-mentioned Comparative Example 1: Production of Comparative Autonomous Floating-Sinking Particles R1, the following procedure (3) was carried out instead of the procedure (2) to produce Autonomous Floating-Sinking Particles 1.

[0052] (3) Preparation of CNF-encapsulated alginate gel particles 5 g of the above-mentioned CNF-containing dispersion was added to 45 g of the alginic acid aqueous solution obtained in step (1) and stirred in ice for 10 minutes (the CNF content was adjusted to 0.5% by mass relative to the total mass of the liquid). Next, the above-mentioned stirred solution was dropped into 200 mL of a 5% by mass calcium chloride aqueous solution using a pipette to produce gel particles (autonomous floating-sinking particles 1) with a diameter of about 5 mm.

[0053] [Production of Comparative Autonomous Floating-Sinking Particles R2 and Autonomous Floating-Sinking Particles 2] [Comparative Example 2: Production of Comparative Autonomous Floating-Sinking Particles R2] (1) Preparation of alginic acid solution To 50 g of a 1% by mass aqueous solution of sodium alginate (product name "Sodium Alginate 500-600 cP", Fujifilm Wako Pure Chemical Industries, Ltd.), 15 g of glucose (product name "D(+)-Glucose", Fujifilm Wako Pure Chemical Industries, Ltd.) and 2 g of dry yeast (product name "Super Camellia", Nisshin Foods Inc.) were added and stirred with a stirrer on ice for 10 minutes to obtain an aqueous solution of alginic acid. (2) Production of CNF-free alginate gel particles 10 g of 30% by mass glucose aqueous solution was added to 40 g of the alginic acid aqueous solution obtained in step (1) and stirred in ice for 10 minutes. Next, the above-mentioned stirred solution was dropped into 200 mL of 5% by mass calcium chloride aqueous solution with a pipette to produce gel particles (comparative autonomous floating-sinking particles R2) with a diameter of about 5 mm.

[0054] [Example 2: Production of autonomous floating / sinking particles 2] In the above-mentioned Comparative Example 2: Production of Comparative Autonomous Floating-Sinking Particles R2, the following procedure (3) was carried out instead of the procedure (2) to produce Autonomous Floating-Sinking Particles 2.

[0055] (3) Preparation of CNF-encapsulated alginate gel particles 10 g of the above-mentioned CNF-containing dispersion was added to 40 g of the alginic acid aqueous solution obtained in step (1) and stirred in ice for 10 minutes (the CNF content was adjusted to 1.0% by mass relative to the total mass of the liquid). Next, the above-mentioned stirred solution was dropped into 200 mL of a 5% by mass calcium chloride aqueous solution using a pipette to produce gel particles (autonomous floating-sinking particles 2) with a diameter of about 5 mm.

[0056] [Production of Comparative Autonomous Floating-Sinking Particles R3 and Autonomous Floating-Sinking Particles 3] [Comparative Example 3: Production of Comparative Autonomous Floating-Sinking Particles R3] (1) Preparation of alginic acid solution To 50 g of a 1% by mass aqueous solution of sodium alginate (product name "Sodium Alginate 500-600 cP", Fujifilm Wako Pure Chemical Industries, Ltd.), 15 g of glucose (product name "D(+)-Glucose", Fujifilm Wako Pure Chemical Industries, Ltd.) and 2 g of dry yeast (product name "Super Camellia", Nisshin Foods Inc.) were added and stirred with a stirrer on ice for 10 minutes to obtain an aqueous solution of alginic acid. (2) Production of CNF-free alginate gel particles 10 g of 30% by mass glucose aqueous solution was added to 10 g of the alginic acid aqueous solution obtained in step (1) and stirred in ice for 10 minutes. Next, the above-mentioned stirred solution was dropped into 200 mL of 5% by mass calcium chloride aqueous solution with a pipette to produce gel particles (comparative autonomous floating-sinking particles R3) with a diameter of about 5 mm.

[0057] [Example 3: Production of autonomous floating / sinking particles 3] In the above-mentioned Comparative Example 3: Production of Comparative Autonomous Floating-Sinking Particles R3, the following procedure (3) was carried out instead of the procedure (2) to produce Autonomous Floating-Sinking Particles 3.

[0058] (3) Preparation of CNF-encapsulated alginate gel particles 10 g of the above-mentioned CNF-containing dispersion was added to 10 g of the alginic acid aqueous solution obtained in step (1), and the mixture was stirred in ice for 10 minutes (the CNF content was adjusted to 2.5% by mass relative to the total mass of the liquid). Next, the above-mentioned stirred solution was dropped into 200 mL of a 5% by mass calcium chloride aqueous solution using a pipette to produce gel particles (autonomous floating-sinking particles 3) with a diameter of about 5 mm.

[0059] [evaluation] The autonomous floating / sinking properties of each of the autonomous floating / sinking particles of Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated. First, a transparent container (capacity 5 to 10 L, height 1 to 2 m) was prepared, and water was poured into the container. The water temperature was adjusted to be kept at 25°C during the test period. Next, the autonomous floating / sinking particles were put into the transparent container containing water. The autonomous floating / sinking particles put into the transparent container repeatedly floated and sunk from the bottom of the water to the surface of the water. The floating / sinking behavior of the autonomous floating / sinking particles during the floating / sinking behavior from the surface of the water to the bottom of the water was visually observed and evaluated according to the following evaluation criteria.

[0060] <Evaluation criteria> "A": When the vessel rose and fell vertically from the surface to the bottom of the water, a large horizontal sway was observed in a direction perpendicular to the vertical. "B": When the specimen rose or fell vertically from the water surface to the bottom, no lateral movement was observed in a direction intersecting the vertical. The results are shown in Table 1.

[0061] [Table 1]

[0062] When the above evaluation was performed, it was observed that the autonomous floating / sinking particles of Examples 1 to 3 shook sideways in a direction intersecting the vertical direction when floating and sinking in the vertical direction from the water surface to the water bottom. The lateral swaying of the autonomous floating / sinking particles was observed immediately after the transparent container containing water was poured into the container, and at any of the following times after the pouring: 5 minutes, 1 hour, 72 hours, 4 days, and 7 days. On the other hand, in the autonomous floating / sinking particles of Comparative Examples 1 to 3, when floating and sinking in the vertical direction from the water surface to the water bottom, no lateral shaking in a direction intersecting the vertical direction was observed. [Explanation of symbols]

[0063] 1, 11 particles 5 Aqueous medium 5a Liquid level 5b liquid bottom T1, T 11 Particle trajectories L Vertical direction

Claims

1. Particles that autonomously float and sink in an aqueous medium, A microorganism that produces gas and / or an aqueous medium-insoluble liquid through biological activity; A substance that is assimilated by the microorganism to produce a gas and / or an aqueous medium-insoluble liquid; A particle comprising: cellulose nanofibers.

2. The particle of claim 1 further comprising a binder polymer.

3. The particle according to claim 2 , wherein the binder polymer is at least one selected from the group consisting of gel-like substances and polymeric compounds.

4. The particle according to any one of claims 1 to 3, wherein the content of the cellulose nanofiber is 0.5 to 8 mass% based on the total mass of the particle excluding the solvent.

5. The particle according to any one of claims 1 to 4, wherein the mass content ratio of the microorganism to the cellulose nanofiber is 0.4 to 10.

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