Cationized yeast

Abstract

To provide a novel biological material having desired performance.SOLUTION: A cationized yeast has a cationic group on its surface, the surface having a zeta potential of 0 mV or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to cationized yeast. [Background technology]

[0002] Many of the functional materials used in the environmental field are chemically synthesized, but the use of biological materials is being considered. Patent Document 1 (JP 2017-222790 A) describes a technology relating to biological materials. This document describes a hexavalent chromium reducing agent containing a culture solution containing a bacterial flora including yeast, lactic acid bacteria, and Bacillus subtilis var. natto, and an aqueous sugar solution (Claim 1), and states that this hexavalent chromium reducing agent can provide a hexavalent chromium reducing agent that enables reduction treatment of hexavalent chromium-contaminated materials without the need for neutralization treatment, even when the hexavalent chromium-contaminated materials are strongly acidic or strongly alkaline (Paragraph 0013). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-222790 Summary of the Invention [Problem to be solved by the invention]

[0004] While biological materials have advantages such as a smaller environmental impact than chemically synthesized materials, there is still room for improvement in terms of performance.

[0005] Therefore, the present invention provides a novel biomaterial having desired properties. [Means for solving the problem]

[0006] The present inventors have conducted extensive research into the possibility of obtaining new functional materials suitable for the environmental field, etc., by treating microorganisms themselves as materials. As a result, they have discovered that useful functional materials can be obtained by using yeast as the microorganism and cationizing its surface, which has led to the completion of the present invention.

[0007] According to the present invention, the following cationized yeast and metal adsorbent are provided. [1] A cationized yeast having cationic groups on its surface, the zeta potential of which is 0 mV or higher. [2] The cationized yeast according to [1], wherein the cationic group is a quaternary ammonium group. [3] The cationized yeast according to [1] or [2], having a group represented by the following general formula (1) on the surface thereof: TIFF0007762943000001.tif27153 (In the above general formula (1), R 1 is an alkanediyl group having 1 to 5 carbon atoms, and R 2 ~R 4 are each independently a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms. [4] The cationized yeast according to any one of [1] to [3], wherein the cationic group is bound to a cell wall component of the yeast. [5] The cationized yeast according to [4], wherein the cell wall component is a polysaccharide. [6] The cationized yeast according to [5], wherein the cationic group is bound to the polysaccharide via an ether bond. [7] The cationized yeast according to any one of [1] to [6], wherein the yeast is Saccharomyces cerevisiae. [8] A metal adsorbent comprising the cationized yeast according to any one of [1] to [7]. [Effects of the Invention]

[0008] The present invention can provide novel biomaterials with desired properties. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the results of measuring the zeta potential of cationized yeast in an example. [Figure 2] FIG. 1 is a diagram showing the measurement results of the selenium adsorption rate of cationized yeast in an example. [Figure 3] FIG. 1 is a diagram showing the results of measuring the zeta potential of cationized yeast in an example. [Figure 4] FIG. 1 is a diagram showing the measurement results of the selenium adsorption rate of cationized yeast in an example. [Figure 5] FIG. 1 is a diagram showing the results of measuring the zeta potential of cationized yeast in an example. [Figure 6] FIG. 1 is a diagram showing the measurement results of the selenium adsorption rate of cationized yeast in an example. [Figure 7] FIG. 1 shows the results of an experiment on flocculation of cationized yeast in an example. [Figure 8] FIG. 1 shows the results of an experiment on flocculation of cationized yeast in an example. [Figure 9] FIG. 1 shows the results of an experiment on flocculation of cationized yeast in an example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the composition may contain each component either alone or in combination of two or more. In this specification, the symbol "to" indicating a numerical range means "greater than or equal to" or "less than or equal to," and both of the numerical values ​​at both ends are included.

[0011] (cationized yeast) In this embodiment, the cationized yeast has cationic groups on its surface, and the zeta potential of the surface is 0 mV or higher.

[0012] Here, the surface of yeast specifically refers to the region from the outermost surface of the yeast to a depth of about 100 to 200 nm (Dupres, V. et al.: ACS Nano, 4, 5498 (2010)).

[0013] The cationized yeast is, specifically, a starting yeast in which cationic groups have been introduced onto the surface. Specific examples of the starting yeast include yeasts classified into the Ascomycota or Basidiomycota phylum. Specific examples of yeasts classified in the Ascomycota include the genus Saccharomyces, such as Saccharomyces cerevisiae, Saccharomyces pastrianus, Saccharomyces bayanus, Saccharomyces carlsbergensis, Saccharomyces sake, Saccharomyces uvarum, Saccharomyces pastorianus (carlsbergenisis), Saccharomyces bayanus, and Saccharomyces awamori; Pichia species such as Pichia pastoris, Pichia angusta, Pichia finlandica, Pichia trehalophila, Pichia koclamae, Pichia membranaefaciens, and Pichia minuta; Schizosaccharomyces species such as Schizosaccharomyces pombe; Dekkera genus, such as Dekkera bruxellensis and Dekkera anomala; Kluyveromyces genus, such as Kluyveromyces lactis, Kluyveromyces marxianus, and Kluyveromyces fragilis; Aureobasidium genus, such as Aureobasidium pullulans; Zygosacoharomyces genus, such as Zygosacoharomyces rouxi; and Examples include yeasts belonging to the genus Candida, such as Candida utilis, Candida versatilis, and Candida etchellsii. Specific examples of yeasts classified into the Basidiomycota include the genus Sporobolomyces; Examples include yeasts belonging to the genus Rhodotorula, such as Rhodotorula mucilaginosa.

[0014] From the viewpoint of ease of handling, yeast used in the production of bread; fermented foods such as miso paste and soy sauce; and foods and beverages such as alcoholic beverages are preferred as the raw material yeast. From the viewpoint of availability, the starting yeast is preferably Saccharomyces cerevisiae. From the viewpoint of excellent production stability of the cationized yeast, the starting yeast is preferably a yeast selected from the group consisting of Aureobasidium pullulans, Rhodotorula mucilaginosa, and Candida utilis. The starting yeast is more preferably Saccharomyces cerevisiae. Specific examples of Saccharomyces cerevisiae strains include baker's yeast, CBS7959, CBS7960, CBS7961, CBS7962, CBS7963, CBS7964, IZ-1904, TA, BG-1, CR-1, SA-1, M-26, Y-904, PE-2, PE-5, VR-1, BR-1, BR-2, ME-2, VR-2, MA-3, MA-4, CAT-1, CB-1, NR-1, BT-1, and AL-1.

[0015] The cationic groups in the cationized yeast are formed by physically or chemically modifying the surface of the starting yeast, preferably chemically modifying the surface.

[0016] From the viewpoint of obtaining the desired surface charge characteristics more stably, the cationic group is preferably bound to a cell wall component of the yeast, more preferably to a polysaccharide in the cell wall. Specific examples of polysaccharides in the cell wall include mannans such as α-mannan, glucans such as β-glucan, and chitin. The mannans may also constitute mannoproteins. The polysaccharides in the cell wall may be surface polysaccharides or backbone polysaccharides. From the viewpoint of more stably obtaining the desired surface charge characteristics, it is preferable that cationic groups are bound to the surface polysaccharides of the cell wall. The cationic group may also be introduced into a cell.

[0017] There is no limitation on the bonding mode between the polysaccharide and the cationic group, and it may be determined, for example, depending on the type of sugar constituting the polysaccharide and the type of cationic group. From the viewpoint of introducing the cationic group into the polysaccharide more stably, the cationic group is preferably bound to the polysaccharide via an ether bond.

[0018] Specific examples of the cationic group include one or more groups selected from the group consisting of a quaternary ammonium group and a tertiary amino group. From the viewpoint of excellent production stability of the cationized yeast, the cationic group is preferably a quaternary ammonium group.

[0019] Furthermore, from the viewpoint of achieving excellent production stability of the cationized yeast, the cationized yeast has a group represented by the following general formula (1) on the surface.

[0020] [ka]

[0021] (In the above general formula (1), R 1 is an alkanediyl group having 1 to 5 carbon atoms, and R 2 ~R 4 are each independently a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms.

[0022] In general formula (1), R 1 The number of carbon atoms in R is, for example, 1 or more, and for example, 5 or less, preferably 3 or less, and more preferably 2 or less. 1 The number of carbon atoms is more preferably 1. R 2 ~R 4 The carbon numbers of R are, independently of one another, for example, 1 or more and 5 or less, preferably 3 or less, and more preferably 2 or less. 2 ~R 4 The number of carbon atoms is more preferably 1.

[0023] (zeta potential) The cationized yeast in this embodiment exhibits the above-mentioned specific zeta potential. The zeta potential of the cationized yeast is 0 mV or more, preferably more than 0 mV, more preferably 10 mV or more, even more preferably 20 mV or more, and even more preferably 30 mV or more, from the viewpoint of being more suitable as a flocculant. The zeta potential of the cationized yeast is 30 mV or more, more preferably 40 mV or more, and even more preferably 50 mV or more, from the viewpoint of being more suitable as a metal adsorbent. Furthermore, from the viewpoint of making the cationized yeast more suitable as a metal adsorbent, the zeta potential of the cationized yeast is, for example, 500 mV or less, and may also be, for example, 200 mV or less or 100 mV or less.

[0024] Furthermore, the zeta potential of the raw material yeast for the cationized yeast is, from the viewpoint of obtaining a preferable metal adsorption ability, for example, -100 mV or more, preferably -60 mV or more, more preferably -40 mV or more, and is, for example, -10 mV or less, preferably -15 mV or less, more preferably -20 mV or less.

[0025] The zeta potential of the cationized yeast and the starting yeast is measured as follows: The yeast is suspended in pure water to a turbidity of 0.5 at 600 nm. 750 μL of this solution is dispensed into a cell, and the Z-potential is measured by electrophoretic light scattering using, for example, a Zetasizer Nano ZS (Malvern) cell (DTS1070 cell) at room temperature (approximately 25°C) without stirring. Before cationization, yeast exhibits a negative surface charge (approximately -30 to -15 mV), but the surface charge becomes positive after cationization.

[0026] Next, a method for producing cationized yeast will be described. In this embodiment, the method for producing cationized yeast specifically includes a step of adding a cationizing agent to yeast to introduce cationic groups onto the surface of the yeast. Hereinafter, a more detailed method for producing cationized yeast will be described, taking as an example a case where the cationic group is the group represented by the above general formula (1).

[0027] (Step 10) Sterilizing the yeast (Step 20) After step 10, a step of reacting yeast with a cationizing agent

[0028] In step 10, the yeast is sterilized, for example, by alcohol treatment, and more specifically, immobilized with alcohol. Furthermore, if the yeast is sterilized in step 20, such as when alkali treatment is performed in step 20, step 10 may be omitted. Performing step 10 before step 20 is preferable from the viewpoints of killing the yeast, destroying the yeast cell membrane to cause cationization modification inside the cells as well, increasing the modification efficiency, and improving metal adsorption ability. As the yeast, for example, the above-mentioned starting yeast can be used. More specifically, Saccharomyces cerevisiae such as baker's yeast can be used. The starting yeast can be washed with water as needed before being subjected to step 10. The alcohol in the alcohol treatment in step 10 is, for example, an alcohol having 1 to 3 carbon atoms, such as ethanol or methanol, and is preferably ethanol. The alcohol treatment can be carried out using, for example, a known cell immobilization method. From the viewpoint of improving the sterilizing effect on yeast, the alcohol concentration in step 10 is, for example, 40% or more, preferably 50% or more, more preferably 70% or more, and is, for example, 95% or less, preferably 90% or less.

[0029] From the viewpoint of improving the processing efficiency, the processing temperature in step 10 is, for example, 0°C or higher, and preferably 2°C or higher. Furthermore, from the viewpoint of preventing the yeast from being destroyed, the processing temperature in step 10 is, for example, 85°C or lower, preferably 45°C or lower, and more preferably 10°C or lower. The treatment time in step 10 can be set, for example, depending on the treatment temperature, and is, for example, 0.1 hours or more, preferably 0.5 hours or more, more preferably 1 hour or more, and is, for example, 10 hours or less, preferably 5 hours or less, more preferably 3 hours or less.

[0030] After step 10, the yeast can be separated, for example, by centrifugation, and subjected to step 20. Alternatively, the yeast can be separated by natural sedimentation.

[0031] In step 20, for example, yeast, an alkali metal hydroxide, and a cationizing agent are mixed and reacted to introduce cationic groups onto the surface of the yeast. From the viewpoint of more stable and efficient cationization of the yeast surface, the reaction in step 20 is preferably carried out while shaking the mixed solution containing the yeast, alkali metal hydroxide, and cationizing agent. In step 20, the order of adding the components to the yeast is not limited, but for example, the cationizing agent may be added to the yeast followed by the alkali metal hydroxide. Alternatively, the cationizing agent and alkali metal hydroxide may be added in advance as aqueous solutions, for example, an aqueous cationizing agent solution and an aqueous alkali metal hydroxide solution may be added to the yeast in a predetermined order, or a mixture of the cationizing agent, alkali metal hydroxide, and water may be added to the yeast.

[0032] Specifically, the alkali metal hydroxide functions as a catalyst for the cationization reaction. Examples of alkali metal hydroxides include NaOH and KOH. The alkali metal hydroxide may be added to the yeast in the form of an aqueous solution in advance. The amount of alkali metal hydroxide added is preferably 0.05 g or more, more preferably 0.1 g or more, and even more preferably 0.2 g or more per gram of dry yeast, from the viewpoint of efficiently promoting the reaction. The amount of alkali metal hydroxide added is, for example, 1 g or less, preferably 0.5 g or less, per 1 g of dry yeast.

[0033] When the alkali metal hydroxide is added as an aqueous solution, from the viewpoint of efficiently proceeding with the reaction, the amount of water added is, for example, 10 g or less per 1 g of dry yeast, preferably 5 g or less, more preferably 3 g or less, and even more preferably 1 g or less.

[0034] A specific example of a cationizing agent is an etherifying agent that introduces a cationic group into yeast via an ether bond. More specifically, the cationizing agent is, for example, a quaternary ammonium compound having a glycidyl group in its molecular structure. Examples of such cationizing agents include compounds represented by the following general formula (2) or (3):

[0035] [ka]

[0036] [ka]

[0037] (In the above general formulas (2) and (3), R 1 ~R 4 are R in general formula (1), respectively. 1 ~R 4 and X is a halogen atom. Y in general formula (3) is a halogen atom.

[0038] In the general formula (2), X specifically represents F, Cl, Br or I, and is preferably Cl. A specific example of the compound represented by general formula (2) is glycidyltrimethylammonium chloride. Furthermore, Y in the general formula (3) is specifically F, Cl, Br or I, and preferably Cl. X and Y may be the same or different. A specific example of the compound represented by general formula (3) is (3-chloro-2-hydroxypropyl)trimethylammonium chloride.

[0039] The amount of the cationizing agent added is preferably 0.05 g or more, more preferably 0.5 g or more, and even more preferably 2 g or more per 1 g of dry yeast from the viewpoint of obtaining a favorable zeta potential. The amount of the cationizing agent added may be, for example, 10 g or less per 1 g of dry yeast. The cationizing agent may be added to the yeast as an aqueous solution having a predetermined concentration, for example, about 60 to 90%.

[0040] The reaction temperature in step 20 is preferably 10° C. or higher, more preferably 30° C. or higher, and even more preferably 45° C. or higher, from the viewpoint of obtaining a favorable zeta potential and improving metal adsorption. Furthermore, in order to prevent the yeast from being destroyed, the reaction temperature in step 20 is preferably 90°C or lower, more preferably 75°C or lower, and even more preferably 60°C or lower.

[0041] The reaction time in step 20 is preferably 1 hour or longer, more preferably 3 hours or longer, and even more preferably 8 hours or longer, from the viewpoint of obtaining a favorable zeta potential. From the viewpoint of improving the metal adsorption rate, the reaction time in step 20 is preferably 3 hours or more, more preferably 8 hours or more, and even more preferably 16 hours or more. There is no upper limit to the reaction time in step 20, but from the viewpoint of improving the production efficiency of cationized yeast, it may be, for example, 50 hours or less, preferably 40 hours or less, and more preferably 30 hours or less.

[0042] After step 20, the cationized yeast can be separated and obtained, for example, by centrifugation. The obtained cationized yeast may also be freeze-dried.

[0043] By the above procedure, the cationized yeast of this embodiment can be obtained. The cationized yeast of this embodiment has a zeta potential within a specific range, and therefore can be suitably used as a cationic functional material. For example, the cationized yeast can be suitably used as a cationic adsorbent material such as a metal adsorbent. Cationized yeast can also be used as a flocculant.

[0044] (metal adsorbent) The metal adsorbent in this embodiment includes the cationized yeast in this embodiment, and is, for example, made of the cationized yeast in this embodiment.

[0045] Specific examples of the substances to be adsorbed include anions, and more specific examples include metal compound ions such as selenium compound ions and chromium compound ions; and anions such as arsenate ions, arsenite ions, borate ions, sulfate ions, iodide ions, bromide ions, and chloride ions. Examples of selenium compound ions include hydrogen selenate ions and selenate ions. Examples of chromium compound ions include chromate ions and dichromate ions.

[0046] By using the metal adsorbent of this embodiment, it becomes possible to recover metals contained in environmental water while reducing the burden on the environment, for example.

[0047] The amount of metal adsorbent added can be set depending on the metal concentration in the metal-containing liquid, but for example, about 0.5 mg / mL of cationized yeast can be added to a metal solution containing selenium in selenic acid at a selenium concentration of 0.1 mg / mL, or about 0.02 mg / mL of cationized yeast can be added to a metal solution containing selenium in selenic acid at a selenium concentration of 0.001 mg / mL.

[0048] (flocculant) The flocculant in this embodiment includes the cationized yeast in this embodiment, and for example consists of the cationized yeast in this embodiment. Examples of applications of flocculants include sludge; microorganisms such as yeast and E. coli; and inorganic compounds such as kaolin.

[0049] The amount of flocculant to be added can be set depending on the amount of the substance to be recovered in the liquid containing the substance to be recovered, but for example, if kaolin viscosity is used to evaluate the flocculant, the amount can be approximately 0.001 g / L to 0.05 g / L for 0.5 g / L of kaolin clay.

[0050] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various other configurations can also be adopted. Below, examples of reference forms are added. 1. A cationized yeast having cationic groups on its surface, the zeta potential of which is 0 mV or higher. 2. The cationized yeast according to 1., wherein the cationic group is a quaternary ammonium group. 3. The cationized yeast according to 1. or 2., which has a group represented by the following general formula (1) on the surface thereof: TIFF0007762943000005.tif27153 (In the above general formula (1), R 1 is an alkanediyl group having 1 to 5 carbon atoms, and R 2 ~R 4 are each independently a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms. 4. A cationized yeast according to any one of 1. to 3., wherein the cationic group is bound to a cell wall component of the yeast. 5. The cationized yeast according to 4., wherein the cell wall component is a polysaccharide. 6. The cationized yeast according to 5., wherein the cationic group is bound to the polysaccharide via an ether bond. 7. The cationized yeast according to any one of 1. to 6., wherein the yeast is Saccharomyces cerevisiae. 8. A metal adsorbent comprising the cationized yeast described in any one of 1. to 7. [Example]

[0051] Hereinafter, the present embodiment will be specifically described with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0052] Example 1 In this example, cationized yeast was produced by varying the amount of cationizing agent added, and the selenium adsorption rate was measured.

[0053] (Method of producing cationized yeast) A few grams of dried baker's yeast (Nissin Flour Milling Co., Ltd., Super Camellia Dry Yeast) was washed five times with approximately 30-50 mL of purified water, recovered by centrifugation (approximately 2-10 minutes at 3000 × g), and freeze-dried again to obtain dried yeast. 0.2 g of dried yeast was weighed out, suspended in 70% aqueous ethanol, and allowed to stand at 4°C for 2 hours. It was then washed with purified water. After washing, 0.51, 2.84, or 7.85 mL of 80% glycidyltrimethylammonium chloride aqueous solution was added to the precipitate obtained by centrifugation (approximately 2 to 10 minutes at 3000 × g), and then 0.05 g of sodium hydroxide and 0.5 mL of pure water (sodium hydroxide aqueous solution concentration: 0.1 g / mL) were added and suspended. The resulting suspension was shaken for 20 hours at 45°C using a water bath PERSONAL-11 (TAITEC), then washed with pure water and freeze-dried. In Figures 1, 2, 7 and 8, the cationized yeasts prepared by adding 0.51, 2.84 and 7.85 mL of 80% glycidyltrimethylammonium chloride solution to the precipitate are designated as L, M and H, respectively.

[0054] (Method for measuring zeta potential) Cationized yeast was suspended in pure water to an OD600 of 0.5. 750 μL of this solution was dispensed into a cell, and the zeta potential was measured by electrophoretic light scattering using a Zetasizer Nano ZS (Malvern) DTS1070 cell at room temperature (approximately 25°C). As a control, the zeta potential of yeast before cationization was measured in the same manner, and the zeta potential of the yeast before cationization treatment was approximately -30 to -15 mV. The results of measuring the zeta potential of the cationized yeast obtained in each example are shown in FIG.

[0055] (Method for measuring selenium adsorption rate) Two mg of cationized yeast was added to 4 mL of an aqueous solution containing 100 ppm selenium in selenate ions, and the mixture was shaken at 30°C and 140 rpm for 10 minutes to allow adsorption. The mixture was then centrifuged at 3,000 × g for 10 minutes, and 1.5 mL of the resulting supernatant was further centrifuged at 17,800 × g for 5 minutes. One mL of this supernatant was diluted 10-fold to prepare a sample for ICP measurement. The selenium concentrations of these samples were measured using a Vista MPX Simultaneous ICP-OES (Varian Inc.), and the selenium adsorption rate was calculated from the luminescence intensity. The calculation was performed using the following formula: Adsorption rate (%) = {(before adsorption - after adsorption) selenium concentration} ÷ selenium concentration before adsorption As a control, the selenium adsorption rate of the yeast before cationization was measured in the same manner. The measurement results of the selenium adsorption rate for the cationized yeast obtained in each example are shown in Figure 2.

[0056] Example 2 In Example 1, cationized yeast H was prepared by adding 7.85 mL of 80% glycidyltrimethylammonium chloride solution to the precipitate. The amount of NaOH added was 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08 g, and the amount of pure water added was 3 mL in each case. The same procedures as in Example 1 were repeated to produce cationized yeast, and the zeta potential and selenium adsorption rate were measured. The measurement results of the zeta potential of the cationized yeast obtained in each example are shown in Figure 3. Furthermore, the measurement results of the selenium adsorption rate of the cationized yeast obtained in each example are shown in Figure 4.

[0057] Example 3 In Example 1, cationized yeast H was prepared by adding 7.85 mL of 80% glycidyltrimethylammonium chloride solution to the precipitate. The amount of NaOH added was 0.05 g in each case, and the amount of pure water added was 0.25, 0.5, 1, or 2 mL. The same procedures as in Example 1 were repeated to produce cationized yeast, and the zeta potential and selenium adsorption rate were measured. The measurement results of the zeta potential of the cationized yeast obtained in each example are shown in Figure 5. The measurement results of the selenium adsorption rate of the cationized yeast obtained in each example are shown in Figure 6.

[0058] 1 to 6, it was confirmed that the yeast could be cationized in each example, and that the obtained cationized yeast had the ability to adsorb selenate ions.

[0059] Example 4 In this example, an agglutination test was carried out using the cationized yeasts L, M and H obtained in Example 1 (FIGS. 1 and 2).

[0060] (Agglomeration experiment 1) Kaolin (MP Biomedicals, LLC, KAOLIN HYDRATED ALUMINUM SILICATE) was prepared to a turbidity of 500°C (0.5 g / L) at room temperature (approximately 25°C) and thoroughly stirred. 2 mL of the resulting kaolin suspension was added to a polystyrene test tube (12 × 75 mm). The prepared cationized yeast L, M, or H was then added to a final concentration of 0.005, 0.001, 0.0005, 0.0001, or 0% and mixed at 2000 rpm for 10 seconds using a vortex mixer. The mixture was allowed to stand for 1 minute, and the turbidity (OD600) was measured using an Ultrospec 1100 (Amersham Biosciences). Immediately afterward, the condition of the test tube was visually observed and photographed. The results are shown in Figures 7 and 8. Figure 7 shows the turbidity of the kaolin suspension after the addition of cationized yeast. Figure 8 shows the appearance of the kaolin suspension in a test tube after the addition of cationized yeast.

[0061] (Examples 5 to 8) In this example, a flocculation test was carried out using the cationized yeast obtained under the production conditions of cationized yeast H in Example 1.

[0062] (Agglomeration experiment 2) At room temperature (approximately 25°C), a cationized yeast dispersion was added to a test tube containing 1 mL of the bacterial cell suspension shown in Table 1 so that the final concentration (% weight / volume) was as shown in Figure 9, and the mixture was mixed with a vortex mixer at 900 rpm for 10 seconds. After leaving the mixture to stand for 1 minute, the aggregates were visually observed (and photographed). The results of Examples 5 to 8 are shown in Figure 9. In Figure 9, the results of Examples 6, 5, 7 and 8 are shown in order from top to bottom.

[0063] [Table 1]

Claims

1. A cationized yeast having cationic groups on its surface, the zeta potential of the surface being 0 mV or more, the cationic group is a quaternary ammonium group, A cationized yeast, wherein the cationic groups are bound to cell wall components of the yeast.

2. The cationized yeast according to claim 1 , having a group represented by the following general formula (1) on the surface: 【Chemistry 1】 (In the above general formula (1), R 1 is an alkanediyl group having 1 to 5 carbon atoms, and R 2 ~R 4 are each independently a linear or branched alkyl group having 1 to 5 carbon atoms.

3. The cationized yeast according to claim 1 or 2, wherein the cell wall component is a polysaccharide.

4. The cationized yeast according to claim 3 , wherein the cationic group is bound to the polysaccharide via an ether bond.

5. The cationized yeast according to claim 1 , wherein the yeast is Saccharomyces cerevisiae.

6. A metal adsorbent comprising the cationized yeast according to any one of claims 1 to 5.

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