Calcium carbonate particle, method for producing the same, and filler using the same

Abstract

To provide calcium carbonate particles having a high aspect ratio using lactic acid bacteria, a method for producing the same, and an application of the same.SOLUTION: Calcium carbonate particles of the present invention contain lactobacilli and calcium carbonate covering the same. The method for producing the calcium carbonate particles of the present invention includes: preparing a dispersion in which lactobacilli are dispersed in water; mixing the dispersion, methanol, and carbonate so that the volume ratio of methanol to the dispersion is greater than 0.5 and less than 2; preparing a mixed solution; adding a calcium salt to the mixed solution to prepare a reaction solution; and holding the reaction solution in a temperature range of 45°C or higher and less than 70°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to calcium carbonate particles, a method for producing the same, and a filler using the same. [Background technology]

[0002] Calcium carbonate is known as a filler that is mixed into structural materials such as plastics to reinforce them and improve their heat resistance. It is also used as a calcium fortifier, antacid, and abrasive. Such calcium carbonate is generally produced by blowing CO2 gas into a suspension of limestone powder to dissolve it, and controlling the concentration, pH, ion species, and holding temperature, but a manufacturing process that is less environmentally hazardous, cheaper, and easier to mass-produce is desired. The calcium carbonate obtained in this way is in the form of spherical particles.

[0003] In recent years, materials using biological materials as templates have been developed (see, for example, Non-Patent Document 1 and Patent Document 1). Non-Patent Document 1 reports hollow zinc oxide particles using lactic acid bacteria. Patent Document 1 relates to hollow particles formed by precipitating or coating a metal compound on the surface of a particulate biomaterial, characterized in that the hollow particles have a porous membrane structure of the metal compound and retain the outer shell shape of the biomaterial. Here, the particulate biomaterial is yeast, starch, chlorella (algae), lactic acid bacteria, spores, or pollen. However, none of these documents discloses calcium carbonate particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-326557 A [Non-patent literature]

[0005] [Non-Patent Document 1] H. Zhou et al., Microporous and Mesoporous Materials, 100, 2007, 322-327 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, an object of the present invention is to provide calcium carbonate particles having a high aspect ratio produced by using lactic acid bacteria, a production method thereof, and a filler using the same. [Means for solving the problem]

[0007] The calcium carbonate particles according to the present invention contain lactobacillus bacteria and a calcium carbonate layer covering the lactobacillus bacteria, thereby solving the above-mentioned problems. The calcium carbonate layer may be made of calcium carbonate having an aragonite crystal structure. The average aspect ratio may be in the range of 5 to 50. The average aspect ratio may be in the range of 10 to 30. The average thickness of the calcium carbonate layer may be in the range of 200 nm to 1500 nm. The average minor axis length may be in the range of 0.5 μm or more and 2 μm or less, and the average major axis length may be in the range of 5 μm or more and 50 μm or less. The method for producing the above-mentioned calcium carbonate particles according to the present invention comprises preparing a culture solution containing Lactobacillus, diluting the culture solution with a dispersion medium to prepare a dispersion, mixing the dispersion, methanol, and a carbonate salt so that the volume ratio of the methanol to the dispersion solution is 0.5 to 2, to prepare a mixed solution, adding a calcium salt to the mixed solution to prepare a reaction solution, and maintaining the reaction solution at a temperature range of 45°C to less than 70°C, thereby solving the above-mentioned problem. The optical density OD600 of the culture may be in the range of 0.05 to 1. The optical density OD600 may be in the range of 0.05 to 0.7. In preparing the dispersion liquid, a volume ratio of the dispersion medium to the culture solution may be 2 or more and 10 or less. The volume ratio of the water to the culture medium may be 3 or more and 7 or less. In preparing the mixed liquid, a volume ratio of the methanol to the dispersion may be 0.75 or more and 1.25 or less. The carbonate may be at least one selected from the group consisting of an alkali metal carbonate and an alkaline earth metal carbonate. The calcium salt may be at least one selected from the group consisting of calcium halides, calcium nitrate, calcium sulfate, calcium acetate, and calcium phosphate. The reaction liquid may be held at a temperature in the range of 50°C or higher and 60°C or lower. The filler according to the present invention contains the above calcium carbonate particles, thereby solving the above problems. Effect of the Invention

[0008] The calcium carbonate particles according to the present invention contain lactobacillus bacteria and a calcium carbonate layer covering the lactobacillus bacteria. The use of lactobacillus bacteria results in a rod-like shape, making it possible to provide calcium carbonate particles with a high aspect ratio. In addition, the use of lactobacillus bacteria as the core allows for weight reduction while maintaining the properties of calcium carbonate. Such calcium carbonate particles are used as a filler for various structural materials.

[0009] The method for producing calcium carbonate particles according to the present invention includes the steps of preparing a culture solution containing lactobacillus bacteria, diluting the culture solution with a dispersion medium to prepare a dispersion solution, mixing the dispersion solution, methanol, and a carbonate salt so that the volume ratio of methanol to the dispersion solution is 0.5 to 2 to prepare a mixture solution, adding a calcium salt to the mixture solution to prepare a reaction solution, and holding the reaction solution at a temperature range of 45°C to 70°C. According to the present invention, the above-mentioned calcium carbonate particles can be obtained by preparing a reaction solution at a specific mixing ratio using lactobacillus bacteria, such as yogurt, as a solvent and methanol, and holding the reaction solution at a specific temperature. The method of the present invention does not require special techniques or equipment, so it not only enables low costs, but also has low environmental impact and is advantageous for mass production. [Brief description of the drawings]

[0010] [Figure 1] Schematic diagram showing calcium carbonate particles of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing another calcium carbonate particle of the present invention. [Diagram 3] Flowchart showing the steps for producing calcium carbonate particles of the present invention [Figure 4] Optical microscope image of lactic acid bacteria in culture medium [Diagram 5] FIG. 1 shows an optical microscope photograph of a sample of Example 1. [Figure 6] FIG. 1 shows an optical microscope photograph of a sample of Example 2. [Figure 7] FIG. 1 shows an optical microscope photograph of a sample of Example 3. [Figure 8] FIG. 1 shows an optical microscope photograph of a sample of Example 4. [Figure 9] FIG. 1 shows an optical microscope photograph of a sample of Example 5. [Figure 10] FIG. 1 shows an optical microscope photograph of a sample of Example 6. [Figure 11] FIG. 1 shows an optical microscope photograph of a sample of Example 7. [Figure 12] FIG. 1 shows an optical microscope photograph of a sample of Example 8. [Figure 13] FIG. 1 shows the Raman spectrum of the sample in Example 1. [Figure 14] FIG. 1 shows an optical microscope photograph and a Raman spectrum of a sample of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are given like reference numerals and their description will be omitted. The calcium carbonate particles and the method for producing the same according to the present invention will be described.

[0012] FIG. 1 is a schematic diagram showing calcium carbonate particles of the present invention. FIG. 2 is a schematic diagram showing another calcium carbonate particle of the present invention.

[0013] The calcium carbonate particle 100 of the present invention includes lactobacillus 110 and a calcium carbonate layer 120 made of calcium carbonate that covers the lactobacillus 110. Since the calcium carbonate particle 100 of the present invention has the lactobacillus 110 as a core, it has a rod-like shape and a high aspect ratio. In addition, since the calcium carbonate particle 100 has the lactobacillus 110 as a core, it is possible to reduce the weight while maintaining the characteristics of the calcium carbonate layer 120.

[0014] Another calcium carbonate particle 200 of the present invention is similar to the calcium carbonate particle 100 of Fig. 1, except that the lactobacillus bacteria 110 are connected in the longitudinal direction to form a core. The calcium carbonate particle 200 has a larger aspect ratio than the calcium carbonate particle 100. Note that, although Fig. 2 shows four lactobacillus bacteria 110 connected in a row, the number of lactobacillus bacteria 110 connected in a row is not limited thereto, and two, three, or more lactobacillus bacteria 110 may be connected in a row.

[0015] Next, each component will be described in detail. The lactobacillus 110 is not limited, but may be, for example, lactobacillus of the genus Lactobacilus or lactobacillus of the genus Bifidobacterium. The lactobacillus 110 is preferably lactobacillus of the genus Lactobacillus because of the ease of availability of yogurt and the like.

[0016] Examples of Lactobacillus lactic acid bacteria include, but are not limited to, Lactobacillus plantarum, Lactobacillus gasseri, Lactobacillus kefir, Lactobacillus brevis, Lactobacillus fructivorans, Lactobacillus acetotolerans, Lactobacillus acidophilus, Lactobacillus butinelli, Lactobacillus casei, Lactobacillus delbreckii subsp. delbreckii, and Lactobacillus delbreckii subsp. bulgaricus.

[0017] Examples of Bifidobacterium lactobacilli include, but are not limited to, Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium brebu, Bifidobacterium anguata, Bifidobacterium animalis, Bifidobacterium asteroides, and Bifidobacterium baum.

[0018] The calcium carbonate layer 120 covering the lactobacillus 110 functions as a shell, and is preferably made of calcium carbonate having an aragonite crystal structure. This allows the calcium carbonate particles 100 to grow anisotropically with respect to the lactobacillus 110 core, and stabilizes them. From this, if a rod-shaped product is confirmed under an optical microscope, it may be determined that the calcium carbonate layer 120 has an aragonite crystal structure. In detail, if the peaks indicating the aragonite crystal structure in the Raman spectroscopy spectrum (1085, 705, and 701 cm -1 ) is detected, it can be determined that the material has an aragonite crystal structure.

[0019] The average minor axis length (W) (referred to as the average minor axis length) of the calcium carbonate particles 100 and 200 of the present invention, which have lactobacillus bacteria 110 as their core, is in the range of 0.5 μm to 2 μm, and the average major axis length (L) (referred to as the average major axis length) is in the range of 5 μm to 50 μm. The average minor axis length is preferably in the range of 0.5 μm to 1.5 μm, and the average major axis length is in the range of 15 μm to 30 μm. In the present specification, the average minor axis length and the average major axis length are values ​​calculated by image analysis using ImageJ (ver. 1.54d; open source, public domain image processing software) for 100 calcium carbonate particles.

[0020] The calcium carbonate particles 100 and 200 of the present invention have a large aspect ratio, but preferably the average aspect ratio is 5 or more and 50 or less. This makes them suitable for use as a filler. According to the production method described below, it is possible to provide calcium carbonate particles 100 and 200 having an average aspect ratio of, for example, 10 or more and 30 or less, and further 15 or more and 25 or less. The average aspect ratio is represented by the ratio of the average major axis length to the average minor axis length of the calcium carbonate particles 100 and 200.

[0021] In the calcium carbonate particles 100, 200 of the present invention, the average thickness of the calcium carbonate layer 120 covering the lactobacillus 110 satisfies the range of 200 nm or more and 1500 nm or less. Within this range, the properties of calcium carbonate (e.g., white color, strength, heat insulation, fire resistance, etc., described below) can be utilized. The average thickness of the calcium carbonate layer 120 is preferably in the range of 500 nm or more and 1000 nm or less. In this specification, the average thickness is the average value of thicknesses at any 20 points of the calcium carbonate layer 120 observed in an optical microscope photograph.

[0022] The calcium carbonate particles 100 and 200 of the present invention are utilized as a filler for various construction materials by utilizing their shape. Such a filler can be added to any construction material to improve the strength of the construction material. Since the calcium carbonate particles 100 and 200 of the present invention have a white color, they may be added, for example, for the purpose of improving the whiteness of paper, etc. Since the calcium carbonate particles 100 and 200 of the present invention have heat insulating properties, they may be added, for example, for the purpose of heat insulating and fireproofing paints, fibers, construction materials, etc. The calcium carbonate particles 100 and 200 of the present invention may be added to food, medicines, and agricultural products to fortify calcium or as an abrasive.

[0023] Next, an exemplary method for producing the calcium carbonate particles of the present invention will be described. In the present invention, by using lactobacillus as a core, calcium carbonate particles having a calcium carbonate layer as a shell can be produced.

[0024] FIG. 3 is a flow chart showing the steps of producing calcium carbonate particles of the present invention.

[0025] The calcium carbonate particles of the present invention are produced by the following steps. Step S310: A culture solution containing lactobacillus is prepared. Step S320: The culture solution prepared in step S310 is diluted with a dispersion medium to prepare a dispersion solution. Step S330: The dispersion liquid prepared in step S320, methanol, and carbonate are mixed to prepare a mixed liquid, with the volume ratio of methanol to the dispersion liquid being 0.5 to 2. Step S340: A calcium salt is added to the mixture prepared in step S330 to prepare a reaction liquid. Step S350: The reaction solution prepared in step S340 is kept at a temperature in the range of 45°C or higher and lower than 70°C. The reaction solution prepared under the above-mentioned specific conditions is maintained at a specific temperature, whereby a reaction occurs to produce the calcium carbonate particles 100 and 200 of the present invention. Each step will be described in detail.

[0026] In step S310, the lactobacillus may be the above-mentioned lactobacillus of the genus Lactobacilus or lactobacillus of the genus Bifidobacterium, and commercially available yogurt may be used because of its ease of acquisition and management.

[0027] In step S310, in the present specification, the optical density of the culture solution at a wavelength of 600 nm (OD600) is used as the suspension concentration of lactobacillus in the culture solution. The optical density of the culture solution is preferably in the range of 0.05 to 1. The optical density of the culture solution is more preferably in the range of 0.05 to 0.7. If the optical density is in this range, the calcium carbonate particles of the present invention can be efficiently obtained. The optical density of the culture solution is even more preferably in the range of 0.3 to 0.7.

[0028] In step S310, the medium used for the culture is not particularly limited, and any known medium can be used. However, APT medium (7.5 g / L extract yeast, 12.5 g / L pancreatic juice digested casein, 10.0 g / L dextrose, 5.0 g / L sodium citrate, 0.001 g / L thiamine hydrochloride, 5.0 g / L sodium chloride, 5.0 g / L dipotassium phosphate, 0.14 g / L manganese chloride, 0.8 g / L magnesium sulfate, 0.04 g / L iron sulfide, 0.2 g / L polysorbate 80), commercially available MRS medium, etc. may also be used.

[0029] In step S310, the culture temperature is, for example, in the range of 37° C. to 45° C. Within this range, lactobacillus bacteria can grow.

[0030] In step S310, the culture time may typically be in the range of 10 hours to 100 hours, within which a culture solution containing a sufficient amount of lactobacillus can be obtained.

[0031] In step S320, the dispersion medium may be, for example, sterilized water, sterilized water, a buffer solution, physiological saline, or the like. The dispersion liquid is preferably prepared so that the volume ratio of the dispersion medium to the culture liquid prepared in step S310 is 2 or more and 10 or less. This allows the lactic acid bacteria to be stably dispersed. The dispersion liquid is more preferably prepared so that the volume ratio of the dispersion medium to the culture liquid prepared in step S310 is 3 or more and 7 or less. This allows the lactic acid bacteria to be stably dispersed at a sufficient concentration. The dispersion liquid is even more preferably prepared so that the volume ratio of the dispersion medium to the culture liquid prepared in step S310 is 3 or more and 5 or less.

[0032] In step S330, the mixture is mixed so that the volume ratio of methanol to the dispersion medium is 0.5 or more and 2 or less. By satisfying this range, the lactobacillus can be dispersed in the mixture. More preferably, the volume ratio of methanol to the dispersion medium is mixed so that it is 0.75 or more and 1.25 or less. By satisfying this range, the lactobacillus can be well dispersed in the mixture, and the coating of calcium carbonate as a shell can be promoted in step S350 described later. Depending on the dispersion state, the lactobacillus can be continuous in the longitudinal direction, which can promote the production of calcium carbonate particles 200 shown in FIG. 2.

[0033] In step S330, the carbonate is not particularly limited as long as it reacts with a calcium salt described below to produce calcium carbonate, but may be, for example, at least one water-soluble carbonate selected from the group consisting of alkali metal carbonates such as lithium carbonate and sodium carbonate, and alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate.

[0034] In step S340, the calcium salt is not particularly limited as long as it reacts with the above-mentioned carbonate to produce calcium carbonate, but may be, for example, at least one water-soluble calcium salt selected from the group consisting of calcium halides such as calcium chloride and calcium bromide, calcium nitrate, calcium sulfate, calcium acetate, and calcium phosphate.

[0035] In step S340, the calcium salt may be added in the same molar ratio as the carbonate added in step S330. The reaction solution is prepared in this manner, and in order to promote the reaction, the temperature is preferably maintained in a range of 45° C. or more and less than 70° C. in step S350. Within this range, the carbonate and the calcium salt react with each other to produce calcium carbonate having an aragonite crystal structure. More preferably, the temperature is preferably maintained in a range of 50° C. or more and 60° C. or less. This allows the carbonate and the calcium salt to react efficiently, promoting the production of calcium carbonate having an aragonite crystal structure.

[0036] In step S350, the reaction solution is preferably held without stirring, which allows lactobacilli, rather than lactococci, to be preferentially cored and efficiently coated with calcium carbonate.

[0037] In step S350, the retention time is not particularly limited, but may be, for example, 5 minutes or more and 60 minutes or less. If the retention time is within this range, a reaction will occur.

[0038] As described above, according to the method of the present invention, it is possible to provide calcium carbonate particles having a large aspect ratio, which have lactobacillus as a core and calcium carbonate as a shell, at a mild temperature by using lactobacillus as typified by yogurt, which is free from restrictions on management and handling, and therefore is industrially advantageous.

[0039] Note that, following step S350, separation and purification may be performed by a known method. For example, since lactococci and lactobacilli have different specific gravities, lactococci are removed by centrifugation utilizing the difference in specific gravities. Furthermore, since unreacted lactobacilli are lysed by an alkaline solution containing sodium hydroxide (NaOH) and sodium dodecyl sulfate (SDS), an anionic surfactant, these alkaline solutions are added and separated by centrifugation.

[0040] The calcium carbonate particles of the present invention may be calcined to burn off the lactobacillus bacteria to form hollow calcium carbonate particles. The calcination temperature is not particularly limited as long as the lactobacillus bacteria can be thermally decomposed and burned, and may be, for example, at a temperature in the range of 500° C. to 1200° C. for 30 minutes to 10 hours.

[0041] Alternatively, the calcium carbonate particles of the present invention may be treated with an alkali to lyse the lactobacillus bacteria, thereby forming hollow calcium carbonate particles. In this case, sodium hydroxide, potassium hydroxide, etc. can be used for the alkali treatment.

[0042] The hollow calcium carbonate particles can be used as capsules for drug delivery, and can also be used as the above-mentioned filler. In particular, since they are hollow, they can be further lightened, and their low thermal conductivity can improve their heat insulation.

[0043] The present invention will now be described in detail with reference to specific examples, but it should be noted that the present invention is not limited to these examples. EXAMPLES

[0044] [Example 1] In Example 1, calcium carbonate particles were produced using the production process shown in FIG.

[0045] A culture solution (suspension) containing lactic acid bacteria was prepared (step S310 in Figure 3). Bulgaria yogurt manufactured by Meiji Dairies was diluted 1 / 10 with sterilized water, and 100 μL of the diluted solution was added to 10 mL of Becton Dickinson APT broth liquid medium and cultured at 37°C for 2 days. The culture solution thus obtained was observed under an optical microscope (Nikon Solutions, FN-1). The results are shown in Figure 4.

[0046] FIG. 4 shows an optical microscope image of lactic acid bacteria in a culture medium.

[0047] 4, it was found that rod-shaped lactobacilli and coccoid lactobacilli were present in the culture solution. The lactobacilli were Lactobacillus ruderbreckii subsp. bulgaricus, which belong to the genus Lactobacillus, and the lactococci were Streptococcus thermophilus, which belong to the genus Thermophilus.

[0048] The average length of the minor axis of the lactobacilli was 500 nm, the average length of the major axis was 10 μm, and the average aspect ratio was 20. The average length and average aspect ratio were calculated for 100 lactobacilli by image analysis using ImageJ (ver. 1.54d; an open source, public domain image processing software).

[0049] The above culture solution was centrifuged and washed with water and ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and the optical density (OD600) at a wavelength of 600 nm was adjusted to 0.5 using a spectrophotometer (manufactured by Thermo Scientific, GENESYS 10S UV-Vis). The culture solution was diluted with a dispersion medium to prepare a dispersion solution (step S320 in FIG. 3). Specifically, this culture solution (100 μL) was redispersed in sterilized water (400 μL) as a dispersion medium to obtain a dispersion solution (500 μL).

[0050] This dispersion liquid, methanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 500 μL), and an aqueous sodium carbonate solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 1M, 10 μL) were mixed in the ratios shown in Table 1 to prepare a mixed liquid (step S330 in FIG. 3). At this time, the volume ratio of methanol (500 μL) to the dispersion liquid (500 μL) was 1.0. Next, an aqueous calcium chloride solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 1M, 10 μL) was added to the obtained mixed liquid to prepare a reaction liquid (step S340 in FIG. 3). The reaction liquid was kept in a water bath at 60° C. for 15 minutes without stirring (step S350 in FIG. 3). As a result, a white cotton-like precipitate was confirmed. The precipitate was filtered, washed, and dried in air at 60° C. for 24 hours. The powder sample obtained in this manner is referred to as the sample of Example 1.

[0051] The sample of Example 1 was white. The sample of Example 1 was observed with an optical microscope. The sample of Example 1 was subjected to Raman spectroscopy (visible-near infrared RAMANPlus, manufactured by Nanophoton Corporation) to identify the substance. These results are shown in Figures 5, 13, and 14.

[0052] [Example 2 to Example 8] In Examples 2 to 8, the culture medium (OD(600)=0.5, 100 μL) prepared in Example 1 was used to prepare reaction solutions in the proportions shown in Table 1 in the same manner as in Example 1, and the reaction was carried out under the retention conditions shown in Table 1. The samples thus obtained are referred to as samples of Examples 2 to 8, respectively. The samples of Examples 2 to 8 were observed under an optical microscope in the same manner as in Example 1. The results are shown in Figures 6 to 12.

[0053] For simplicity, the synthesis conditions for the samples of Examples 1 to 8 are summarized in Table 1, and the results are summarized and explained.

[0054] [Table 1]

[0055] FIG. 5 shows an optical microscope photograph of the sample of Example 1. FIG. 6 shows an optical microscope photograph of the sample of Example 2. FIG. 7 shows an optical microscope photograph of the sample of Example 3. FIG. 8 is a diagram showing an optical microscope photograph of the sample of Example 4. FIG. 9 is a diagram showing an optical microscope photograph of the sample of Example 5. FIG. 10 is a diagram showing an optical microscope photograph of the sample of Example 6. FIG. 11 is a diagram showing an optical microscope photograph of the sample of Example 7. FIG. 12 is a diagram showing an optical microscope photograph of the sample of Example 8.

[0056] According to FIG. 5, the sample of Example 1 was mainly a product having a rod-like shape as seen in FIG. 4 (hereinafter referred to as rod-like particles of Example 1). According to FIG. 6, the sample of Example 2 was also mainly a product having a rod-like shape (rod-like particles of Example 2), but some spherically aggregated products (spherical particles of Example 2) were also observed. According to FIG. 7, the sample of Example 3 was a product having a rod-like shape (rod-like particles of Example 3) and spherical aggregates (spherical particles of Example 3). According to FIGS. 8 to 12, the samples of Examples 4 to 8 were all spherical aggregates and did not have a rod-like shape.

[0057] From FIG. 5, the rod-shaped particles of Example 1 were confirmed to have a minor axis length of 1 μm to 2 μm and a major axis length of 5 μm to 50 μm. The average minor axis length and the average major axis length of the rod-shaped particles of Example 1 were 1 μm and 20 μm, respectively, and the average aspect ratio was 20. The average minor axis length and the average major axis length of the rod-shaped particles of Examples 2 and 3 also satisfied the ranges of 1 μm or more and 2 μm or less, and 5 μm or more and 100 μm or less, respectively, and the average aspect ratio satisfied the range of 5 or more and 50 or less. Here, too, image analysis was performed on 100 particles using ImageJ (ver. 1.54d; open source, public domain image processing software).

[0058] More noteworthy, according to Fig. 5, rod-shaped particles longer than the core lactobacillus particles shown in Fig. 4 were also obtained. This indicates that the production process of the present invention shown in Fig. 3 can produce calcium carbonate particles 100 shown in Fig. 1 and calcium carbonate particles 200 shown in Fig. 2 in which some lactobacillus bacteria form a core connected in the longitudinal direction.

[0059] FIG. 13 is a diagram showing the Raman spectrum of the sample of Example 1.

[0060] Spectrum 1 in Fig. 13 is the Raman spectrum of the lactobacillus used for the core, and spectrum 2 is the Raman spectrum of the rod-shaped particles that are the sample of Example 1. The Raman spectrum of lactobacillus has a peak at 2800 cm -1On the other hand, the Raman spectrum of the rod-shaped particles of the sample of Example 1 had a notable peak at around 2800 cm due to CH stretching derived from organic matter. -1 The peaks before and after are reduced, and the peak at 1080cm -1 Although not shown, the Raman spectrum of the rod-shaped particles had a peak at 705 cm -1 , and 701 cm -1 From this, it was found that the sample of Example 1 was mainly composed of rod-shaped particles containing lactobacillus bacteria and a calcium carbonate layer covering the lactobacillus bacteria.

[0061] From Figs. 5 to 13 above, it was shown that by mixing a dispersion liquid containing lactobacillus, methanol, and a carbonate salt so that the volume ratio of methanol to the dispersion liquid is 0.5 or more and 2 or less, as shown in Fig. 3, and adding a calcium salt to this to form a reaction liquid, and maintaining the reaction liquid at a temperature range of 45°C or more and less than 70°C, it is possible to provide rod-shaped calcium carbonate particles containing lactobacillus and a calcium carbonate layer covering the lactobacillus, as shown in Fig. 1 or 2.

[0062] FIG. 14 shows an optical microscope photograph and a Raman spectrum of the sample of Example 1.

[0063] FIG. 14 shows Raman spectroscopy spectra at various positions of rod-shaped particles and spherical particles in the sample of Example 1. The rod-shaped particles have an aragonite peak (1085 cm -1 ), and the spherical particles show a calcite peak (1086 cm -1 ) or vaterite peak (1075cm -1 and 1091 cm -1 Although not shown, the rod-shaped particles show another peak of aragonite (701 cm -1 and 705 cm -1 ) was also confirmed, and another calcite peak (713 cm) was also confirmed in the spherical particles. -1 ) and another peak of vaterite (739 cm -1 and 753 cm -1 ) was also confirmed.

[0064] From these, it was found that the rod-shaped particles were particles containing lactobacillus bacteria and a calcium carbonate layer having an aragonite crystal structure covering the lactobacillus bacteria. Although not shown, it was confirmed that the rod-shaped particles of Examples 2 and 3 also had a calcium carbonate layer having an aragonite crystal structure.

[0065] 14, the thickness of the calcium carbonate layer covering the surface of the rod-shaped particle of Example 1 was in the range of 250 nm to 1000 nm, and the average thickness was 500 nm. The average thickness is the average value of thicknesses at any 20 points of the calcium carbonate layer observed in the optical microscope photograph. [Industrial Applicability]

[0066] The calcium carbonate particles of the present invention can function as a filler for the purpose of reinforcing various structural materials and improving their heat resistance. The calcium carbonate particles of the present invention have a high aspect ratio, and therefore, when used in papermaking, they can make thin paper. In addition, since they contain edible lactic acid bacteria, they can also be used in foods for calcium enrichment, or in pharmaceuticals such as antacids and abrasives. Since such calcium carbonate particles use easily available lactobacillus bacteria, they can be produced at low cost and are advantageous for mass production. [Explanation of symbols]

[0067] 100, 200 Calcium carbonate particles 110 Lactobacillus 120 Calcium carbonate layer

Claims

1. Lactobacillus and, The calcium carbonate layer that coats the aforementioned lactobacilli and Calcium carbonate particles containing calcium carbonate.

2. The calcium carbonate particle according to claim 1, wherein the calcium carbonate layer is made of calcium carbonate having an aragonite crystal structure.

3. The calcium carbonate particles according to claim 1, wherein the average aspect ratio is 5 or more and 50 or less.

4. The calcium carbonate particles according to claim 3, wherein the average aspect ratio is 10 or more and 30 or less.

5. The calcium carbonate particles according to claim 1, wherein the average thickness of the calcium carbonate layer is in the range of 200 nm to 1500 nm.

6. The calcium carbonate particles according to claim 1, wherein the average short axis length is in the range of 0.5 μm to 2 μm, and the average long axis length is in the range of 5 μm to 50 μm.

7. To prepare a culture medium containing Lactobacillus, Diluting the culture medium with a dispersion medium to prepare a dispersion, The dispersion, methanol, and carbonate are mixed so that the volume ratio of methanol to the dispersion is 0.5 or more and 2 or less, to prepare a mixed solution. The calcium salt is added to the aforementioned mixture to prepare the reaction solution. The reaction solution is maintained at a temperature range of 45°C or higher and less than 70°C. A method for producing calcium carbonate particles according to any one of claims 1 to 6, comprising:

8. The method according to claim 7, wherein the optical density OD600 of the culture medium is in the range of 0.05 or more and 1 or less.

9. The method according to claim 8, wherein the optical density OD600 satisfies the range of 0.05 or more and 0.7 or less.

10. The method according to claim 7, wherein, in preparing the dispersion, the volume ratio of the dispersion medium to the culture medium is 2 or more and 10 or less.

11. The method according to claim 10, wherein the volume ratio of the dispersion medium to the culture medium is 3 or more and 7 or less.

12. The method according to claim 7, wherein, in preparing the mixed solution, the volume ratio of methanol to the dispersion is 0.75 or more and 1.25 or less.

13. The method according to claim 7, wherein the carbonate is selected from the group consisting of alkali metal carbonates and alkaline earth metal carbonates.

14. The method according to claim 7, wherein the calcium salt is selected from the group consisting of calcium halides, calcium nitrate, calcium sulfate, calcium acetate, and calcium phosphate.

15. The method according to claim 7, wherein the reaction solution is maintained in a temperature range of 50°C to 60°C.

16. A filler containing calcium carbonate particles according to any one of claims 1 to 6.

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