Lysine particles having core-shell structure

Abstract

The invention relates to a lysine particle with a core-shell structure and a preparation method thereof. The lysine particle with the core-shell structure comprises a core containing lysine; and a shell provided on the surface of the core and comprising lysine hydrate. According to the present application, since the lysine hydrate shell is provided on the surface of the lysine particles and the lysine hydrate shell has low hygroscopicity, deliquescence or caking of the lysine particles due to moisture can be reduced.

Description

Technical Field

[0001] The present disclosure relates to lysine particles having a core - shell structure (which can reduce water adsorption and deliquescence). Background Art

[0002] In conventional lysine production methods, when the addition amount of anions (such as hydrochloric acid and sulfuric acid) is low, water absorption, deliquescence, and caking of particles occur, which makes transportation and marketing difficult and reduces marketability. This phenomenon occurs because when the number of anion molecules is insufficient relative to lysine molecules, the ratio of cationic lysine molecules to neutral lysine molecules increases, and cationic lysine molecules have relatively strong hydrophilicity.

[0003] In this case, when the addition amounts of hydrochloric acid and sulfuric acid are increased, water absorption, deliquescence, and caking can be alleviated or prevented. However, hydrochloric acid and sulfuric acid have no nutritional value as feed, and if applied in excess, they may have a negative impact on animal health. In addition, when additional hydrochloric acid or sulfuric acid is added, there is a disadvantage that the material cost of the product increases as much as the cost of the added chemicals. In addition, when producing hydrochloric acid or sulfuric acid, various environmental pollutants may be generated, which may be problematic.

[0004] In one example, lysine powder products are produced in the form of lysine hydrochloride by adding hydrochloric acid in an equimolar ratio to lysine, followed by a crystallization process. In lysine hydrochloride crystals, the lysine content is theoretically 80% (but considering the quality standard of the lysine hydrochloride content usually sold is 98% or higher), and the actual lysine content is about 79%. In another example, lysine particles containing sulfuric acid are mainly produced. However, since there are fewer anions of sulfate ions relative to chloride ions under the same mass, the content of the lysine particle product is lower than that of the lysine powder product. Commercially available lysine particles are in the form of lysine sulfate with a lysine content of 56 to 64%. If the product is produced by increasing the content by reducing the ratio of sulfuric acid, the marketability will decrease due to water absorption, deliquescence, and caking.

[0005] [Prior Art Documents]

[0006] [Patent Documents]

[0007] (Patent Document 1) US11104925 B2 Summary of the Invention

[0008] [Technical Problem]

[0009] An object of the present disclosure is to provide lysine particles having a core - shell structure, in which lysine hydrate is provided on the surface, thereby significantly reducing water absorption, deliquescence, and caking.

[0010] [Technical Solution]

[0011] The present disclosure relates to lysine particles having a core-shell structure, which have a shell containing lysine hydrate and form a hydrate shell on the surface of the lysine core. Since the lysine hydrate shell has low hygroscopicity, water absorption of the final product lysine particles and thus deliquescence and caking can be significantly reduced.

[0012] Figure 1 is a cross-sectional view of lysine particles according to the present disclosure.

[0013] The lysine particles according to the present disclosure are provided in a core-shell structure, which includes a lysine core containing lysine; and a lysine hydrate shell containing lysine hydrate provided on the surface of the core.

[0014] The lysine particles contain L-lysine and are provided in the form of particles. A "particle" is a macroscopic particle, which is a larger-sized permanent aggregate composed of small particles (such as powder), and can be particles with an average particle diameter of 50 μm to 5 mm, 75 μm to 4 mm, or 100 μm to 3 mm.

[0015] The lysine particles are shown as spherical in the drawings, but this is only an exemplary shape for ease of explanation. As described above, the particles are aggregates composed of small particles and can have various shapes. For example, the particles can have various shapes such as irregular shapes, tetrahedrons, hexahedrons, etc.

[0016] The lysine particles contain a lysine core and a lysine hydrate shell.

[0017] The lysine core can be a region containing lysine and containing no or substantially no lysine hydrate. Substantially not containing lysine hydrate means that the content of lysine hydrate is negligible and there will be no effect of reducing water absorption due to lysine hydrate.

[0018] The lysine core can be provided in the central part of the lysine particles. However, providing the lysine core in the central part does not necessarily mean that the center of the lysine particles coincides with the lysine core. For example, when the lysine particles are irregular in shape, it is difficult to find where the center of the lysine particles is. Therefore, providing the lysine core in the central part of the lysine particles may mean providing the lysine core in the remaining region of the lysine particles except for the lysine hydrate shell part.

[0019] The lysine hydrate shell is provided on the surface of the lysine core.

[0020] According to Equation 1, the following lysine granules may have a hydration rate of 11% to 23%, specifically, 12% to 23%, 13% to 23%, 13% to 21%, 14% to 23%, 15% to 23%, 15% to 21%, 16% to 23%, 16% to 21%, 18% to 23%, 18% to 21%, or 19% to 21%.

[0021] [Equation 1]

[0022]

[0023] In Equation 1 above, W1 represents the lysine content (wt%) in the granules after lysine granule hydration, and W0 represents the lysine content (wt%) in the granules before lysine granule hydration.

[0024] Based on the total weight of the lysine granules, the water content in the lysine granules can range from 10 wt% to 35 wt%, 12 wt% to 28 wt%, 12 wt% to 25 wt%, 13 wt% to 22 wt%, 14 wt% to 22 wt%, 14 wt% to 21 wt%, 16 wt% to 22 wt%, or 18 wt% to 22 wt%.

[0025] Based on the weight of lysine, the water content in the lysine granules can range from 14 wt% to 35 wt%, 14 wt% to 30 wt%, 14 wt% to 29 wt%, 15 wt% to 29 wt%, 16 wt% to 27 wt%, 18 wt% to 27 wt%, 20 wt% to 27 wt%, or 22 wt% to 27 wt%.

[0026] A lysine hydrate shell is provided to surround the lysine core inside, thereby protecting the lysine core from external influences. That is to say, the lysine hydrate shell is provided on the surface of the lysine core so that the lysine core is not exposed to the outside. Therefore, even if the lysine granules are exposed to a high-humidity environment, the low hygroscopic lysine hydrate shell can protect the high hygroscopic lysine core.

[0027] The lysine hydrate shell contains lysine hydrate. Lysine hydrate can be a molecule in which one or more equivalents of water molecules can bind to one equivalent of L-lysine molecule. In some cases, lysine hydrate can be a molecule in which two or more equivalents of water molecules bind to one equivalent of L-lysine molecule. L-lysine is a polar molecule in which positive and negative charges coexist within the molecule and has a high affinity for water molecules. Therefore, generally speaking, lysine can absorb water molecules present in the atmosphere. However, when lysine simply absorbs water molecules present in the air, lysine monohydrate is formed, in which one equivalent of water molecule binds to one equivalent of L-lysine molecule, rather than an excess of water molecules binding to the L-lysine molecule. In the case of lysine monohydrate, it is still possible that lysine monohydrate can bind to water molecules, which may lead to additional water absorption, resulting in deliquescence and caking of lysine particles. In contrast, lysine hydrate bound with two or more equivalents of water molecules can maintain its shape without absorbing additional water in the atmosphere. Therefore, the lysine core inside the lysine particles can be protected by providing lysine hydrate bound with two or more equivalents of water molecules in the lysine hydrate shell.

[0028] The above-mentioned lysine hydrate contained in the lysine hydrate shell has a high degree of crystallinity, so it is impossible to form bridges between lysine molecules. Therefore, solidification and caking caused by bridging between lysine molecules can be prevented.

[0029] Based on the total weight of the lysine particles, the content of lysine in the lysine particles can be 64 wt% to 86 wt%. In some cases, based on the total weight of the lysine particles, the lysine content in the lysine particles can be in the range of 64 wt% to 80 wt%, 64 wt% to 75 wt%, 64 wt% to 70 wt%, 70 wt% to 86 wt%, 75 wt% to 86 wt%, 80 wt% to 86 wt%, 70 wt% to 80 wt% or 75 wt% to 80 wt%. When the lysine content in the lysine particles is higher than the specific amount described above, the content of lysine hydrate provided in the lysine hydrate shell may be sufficient, and the lysine hydrate is provided in a form in which two or more water molecules are bound, so the lysine hydrate shell can have an excellent core protection effect. Therefore, according to the present disclosure, in order to increase the lysine content in lysine particles for commercial use and prevent water absorption, deliquescence and caking, the lysine content can be adjusted to the above range.

[0030] The lysine particles can be provided in the form of free base.

[0031] Lysine granules can be provided without lysine hydrochloride or lysine sulfate. Usually, hydrochloric acid and / or sulfuric acid are added during the production process of lysine granules so that lysine hydrochloride or lysine sulfate can be included in the lysine granules. However, in this case, there is a problem of a decrease in the lysine content in the lysine granules. Considering that the quality standard for the lysine hydrochloride content is 98% or higher, the actual lysine content is about 79%. In another example, lysine granules are mainly produced with sulfuric acid contained therein. However, since there are fewer anions of sulfate ions relative to chloride ions under the same mass, the content of the lysine granule product is lower than that of the lysine powder product. The commercially available lysine granules usually sold are in the form of lysine sulfate with a lysine content of 56 to 64%. In contrast, according to the present disclosure, when a lysine hydrate shell containing lysine hydrate is provided only on the surface without including lysine hydrochloride and lysine sulfate in the lysine granules, the lysine content in the lysine granules can be increased while preventing deliquescence and caking due to water absorption.

[0032] Next, Figure 2 is a flowchart showing a method for producing lysine granules according to the present disclosure.

[0033] Referring to Figure 2 , the method according to the present disclosure includes a first step (S100) of producing lysine in the form of granules; and a second step (S200) of exposing the lysine in the form of granules to a thermo-hygrostat (also referred to as a "thermo-hygrostat") to provide a shell containing lysine hydrate on the surface of the granular lysine, thereby producing lysine granules having a core-shell structure.

[0034] The specific embodiments of the lysine granules having a core-shell structure prepared by the production method according to the present disclosure are the same as those discussed above. Therefore, hereinafter, the features of the production method will be discussed to avoid duplication of content.

[0035] To carry out the method for preparing lysine according to the present disclosure, the first step (S100) of producing lysine in the form of granules is carried out.

[0036] In the first step (S100), granular lysine can be prepared by purchasing commercially available granular lysine. However, in some cases, granular L-lysine can be prepared by preparing a fermentation broth containing L-lysine and then drying the fermentation broth.

[0037] In this case, as used herein, "fermentation product" may refer to a product obtained by the enzymatic or metabolic decomposition of organic matter using microorganisms. For example, the fermentation product may include the culture itself obtained by culturing microorganisms in a culture medium, or a concentrate, dried product, or lyophilized product of the culture obtained by removing the strains therefrom. Further, in this case, the fermentation broth may include the entire fermentation product containing amino acids, or may be a fermentation broth from which impurities have been removed from the fermentation product containing amino acids.

[0038] The "L-lysine producing strain" used in the culturing step includes all wild-type microorganisms, or naturally or artificially genetically modified microorganisms, and may be a microorganism in which a specific mechanism is weakened or enhanced due to the insertion of foreign genes, or the enhancement or inactivation of endogenous gene activity, etc., and may be a microorganism having a gene modification to produce a desired protein or amino acid.

[0039] The strain for producing L-lysine of the present disclosure may be a microorganism that naturally has the ability to produce L-lysine, or a microorganism in which the ability to produce L-lysine has been imparted to a parent strain that does not have the ability to produce L-lysine, but is not limited thereto. Specifically, as used herein, a microorganism for producing L-lysine or a desired product, or a microorganism having the ability to produce L-lysine or a desired product may be a microorganism in which some genes in the biosynthetic pathway of the desired protein or desired product are enhanced or weakened, or some genes in the degradation pathway of the desired protein or desired product are enhanced or weakened. The "enhancement" or "increase" in the ability of the microorganism of the present disclosure to produce L-lysine may mean that the ability of the microorganism of the present disclosure to produce L-lysine is enhanced as compared with the ability of a microorganism, parent strain, or unmodified microorganism different from the microorganism of the present disclosure to produce L-lysine. In one example, as compared with the ability of other microorganisms to produce L-lysine, the ability of the microorganism of the present disclosure to produce L-lysine may be enhanced by about 1% or more, 10% or more, 100% or more, 200% or more, 500% or more, 1000% or more, 1100% or more, 1200% or more, 1300% or more, or about 1.01-fold or more, 2-fold or more, 5-fold or more, 10-fold or more, 11-fold or more, 12-fold or more, or 13-fold or more, but is not limited thereto. As used herein, the term "about" refers to a range including all values of ±0.5, ±0.4, ±0.3, ±0.2, ±0.1, etc., and includes all values equivalent to or within the approximate range immediately following the term "about", but is not limited thereto.

[0040] The above-mentioned microorganisms used in the culturing step may be at least one selected from the group consisting of: Candida famata as yeast, Eremothecium ashbyii and Ashbya gossypii as ascomycetes, Bacillus subtilis as bacteria, and microorganisms belonging to the genus Corynebacterium.

[0041] When the microorganism used in the culturing step is a microorganism belonging to the genus Corynebacterium, the microorganism may specifically be Corynebacterium glutamicum, Corynebacterium crudilactis, Corynebacterium deserti, Corynebacterium efficiens, Corynebacterium callunae, Corynebacterium stationis, Corynebacterium singulare, Corynebacterium halotolerans, Corynebacterium striatum, Corynebacterium ammoniagenes, Corynebacterium pollutisoli, Corynebacterium imitans, Corynebacterium testudinoris, Corynebacterium crenatum or Corynebacterium flavescens, more specifically, Corynebacterium glutamicum, but not limited thereto.

[0042] Microorganisms of the genus Corynebacterium, especially Corynebacterium glutamicum, are gram-positive microorganisms widely used in the production of L-amino acids and other beneficial substances. To produce L-amino acids and other beneficial substances, various studies have been conducted to develop microorganisms for efficient production and technologies for the fermentation process. For example, targeted specific methods (such as methods for increasing the gene expression of enzymes involved in L-lysine biosynthesis, etc.) or methods for removing genes unnecessary for biosynthesis have been widely used. In the present disclosure, strains of the genus Corynebacterium can be used to prepare a fermentation broth containing amino acids.

[0043] After preparing the fermentation broth, steps of separating L-lysine from the fermentation broth and granulating the separated L-lysine can be additionally performed.

[0044] For example, the prepared fermentation broth can be concentrated, and the wet crystals of L-lysine produced during the concentration can be separated. In this method, by removing water from the fermentation broth, L-lysine can precipitate in crystal form. The concentration can be carried out in various ways. Concentration can be performed using a conventional concentrator (e.g., paddle dryer, slurry dryer, vacuum concentrator, forced circulation concentrator, thin film concentrator, or rotary concentrator, etc.) according to the appropriate selection of those skilled in the art.

[0045] In addition, a solid-liquid separator (such as a vacuum membrane filtration device, pressure membrane filtration device, centrifugal separator, etc.) can be used to separate the wet crystals of L-lysine precipitated by concentration from the mother liquor, but it is not limited thereto.

[0046] The mother liquor remaining after separating the wet crystals of L-lysine can be reused for concentration. Therefore, L-lysine that does not form wet crystals or L-lysine that precipitates as crystals of a specific size or smaller (which is not separated in the separation step of the wet crystals of L-lysine and remains in the mother liquor) can be recycled. In addition, after recycling the mother liquor, if necessary, an additional process (such as heating the fermentation broth) can be performed to dissolve the L-lysine precipitated in the form of fine crystals back into the fermentation broth.

[0047] Subsequently, the step of preparing L-lysine mixed granules can be performed by mixing the separated wet crystals of L-lysine with seed crystals. The seed crystals (which are also called crystal seeds or inoculum) used in the above step can refer to materials used as catalysts for liquid crystallization or granulation. Specifically, the seed crystals in the present disclosure can refer to crystals of L-amino acids, such as crystals of L-lysine of the same type as the L-lysine contained in the fermentation concentrate to be granulated, but it is not limited thereto. When the seed crystals and the fermentation broth meet, the solid components present in the fermentation broth combine with the seed crystals to form aggregates, thereby forming granules. The average particle size of the seed crystals used in this step can be 150 to 300 μm. Specifically, seed crystals with an average particle size of 150 to 250 μm, 200 to 300 μm, or 200 to 250 μm can be used, but it is not limited thereto. The particle size of the seed crystals used may ultimately affect the productivity of granule preparation according to the present disclosure, so it can be appropriately selected by those skilled in the art considering the required moisture content, etc.

[0048] In the above steps, a hybrid granulation mechanism can be used to prepare L-lysine hybrid granules. The granules can be obtained by a hybrid granulator, that is, seeds are injected into the hybrid granulator at a constant rate through a feeder while supplying pre-obtained wet amino acid crystals. In this text, a "granule" is a macroscopic granule, which is a larger-sized permanent aggregate composed of small granules (such as powders), and can be granules with an average particle diameter of 50 μm to 5 mm, 75 μm to 4 mm, or 100 μm to 3 mm.

[0049] In addition, in the step of preparing lysine in particulate form, removal of the strain, desalting, and concentration of the fermentation broth can be carried out. Removal of the strain can be carried out by various methods (such as filtration, centrifugation, etc.). In addition, in the step of preparing lysine in particulate form, a desalting process can be carried out. The desalting process can be carried out to remove ionic impurities other than the fermentation product to be produced. The desalting process can be carried out by various methods (such as ion exchange resins, continuous chromatography, etc.). The concentration process can increase the concentration of the fermentation product in the process liquid and enable the fermentation product to be more easily obtained in the subsequent drying process. The concentration process is not limited and various methods (such as a rotary concentrator, etc.) can be used. The above order of filtration, decolorization, strain removal, and desalting can be changed as needed. Filtration, decolorization, and desalting can be carried out after strain removal, or strain removal can be carried out after filtration, decolorization, and desalting.

[0050] Subsequently, a second step (S200) is carried out, that is, lysine in particulate form is exposed to a constant temperature and humidity device to provide a shell containing lysine hydrate on the surface of the particulate lysine.

[0051] The second step (S200) is a step of providing a lysine hydrate shell by forming lysine hydrate on the surface of the prepared particulate lysine.

[0052] In particular, as described above, L-lysine has excellent affinity for water molecules because it contains polar functional groups in its molecule. Therefore, even when exposed to a general atmospheric environment, L-lysine can react with water molecules in the air and turn into L-lysine hydrate. However, in this case, mainly L-lysine monohydrate is formed. L-lysine monohydrate can be further hydrated, so it has a poor water absorption prevention effect. Therefore, even if L-lysine monohydrate is provided on the surface of L-lysine granules, the water absorption prevention effect to be achieved by the present disclosure may not be obtained.

[0053] Therefore, in the second step (S200), the granular lysine is exposed to a constant temperature and humidity environment with specific humidity and temperature, thereby allowing a sufficient hydration reaction to occur in the surface layer of the granular lysine. Specifically, the second step (S200) can be carried out to uniformly provide lysine hydrate, where two or more equivalents of water molecules are bound to one equivalent of L-lysine molecules on the surface layer of the granular lysine.

[0054] In the second step (S200), the constant temperature and humidity environment can be realized in the form of a chamber capable of controlling temperature and humidity. However, in addition to the above, the constant temperature and humidity environment can be realized in various forms. For example, the constant temperature and humidity environment can be realized by transporting the granular lysine through a pipeline with controllable temperature and humidity.

[0055] The constant temperature and humidity environment realized in the second step (S200) can be an environment with a relative humidity of 25% to 60% at a temperature of 30°C. Additionally, if needed, the constant temperature and humidity environment can be realized by gradually increasing the humidity. In this case, as the humidity in the environment to which the granular lysine is exposed slowly increases, L-lysine can be uniformly converted into lysine hydrate, where two or more equivalents of water molecules are bound to one equivalent of L-lysine molecules. Therefore, compared with the case where lysine is immediately exposed to a high humidity environment, the lysine hydrate can be provided more uniformly over the entire surface area.

[0056] Specifically, the second step (S200) can be carried out as follows: the granular lysine is exposed to an environment with a relative humidity of 40%, and then the relative humidity is increased to 50% to 60% at a rate of 0.2% per hour. In this case, the lysine hydrate shell can be formed faster. Thus, in the second step (S200) of the present disclosure, the constant temperature and humidity environment refers to an environment in which the relative humidity and temperature can be adjusted according to the user's needs and maintained at specific values, rather than an environment in which the temperature and humidity remain unchanged and constant throughout the second step (S200).

[0057] The second step (S200) can also include drying the lysine granules after the formation of the lysine hydrate shell. The drying of the lysine granules can be carried out in various ways, such as a fluidized bed dryer, a tray, an oven, etc.

[0058] The method for preparing lysine granules described above can be carried out without adding anionic substances (such as hydrochloric acid and sulfuric acid), or the content of anionic substances can be greatly reduced. Therefore, the prepared lysine granules may not contain lysine anion salts (including lysine sulfate and lysine hydrochloride), or the content of lysine anion salts can be very low. Therefore, even if the prepared lysine granules are used as animal feed, the adverse effects on animal nutrition caused by lysine anion salts can be prevented, and the preparation process cost and environmental pollutant emissions can be reduced.

[0059] Each description and embodiment disclosed herein can be applied to other descriptions and embodiments separately. That is, all combinations of the various elements disclosed herein fall within the scope of the present disclosure. In addition, the scope of the present disclosure is not limited by the specific embodiments described below.

[0060] [Beneficial effects]

[0061] According to the present disclosure, a lysine hydrate shell is provided on the surface of the lysine core, and since the lysine hydrate shell has low hygroscopicity, deliquescence or caking of the lysine granules due to moisture can be reduced.

[0062] In addition, according to the present disclosure, granules with a high lysine content can be prepared because adverse effects caused by moisture absorption can be prevented without lysine hydrochloride or lysine sulfate or while significantly reducing their content. Brief Description of the Drawings

[0063] Figure 1 is a cross-sectional view of a lysine granule according to the present disclosure.

[0064] Figure 2 is a flowchart of a method for preparing lysine granules according to the present disclosure.

[0065] Figures 3a to 3c is an image showing the surface of lysine granules according to the humidity in a thermo-hygrostat chamber.

[0066] Figures 4a to 4c is an image showing the appearance of lysine granules according to the exposure environment in a thermo-hygrostat chamber. Detailed Description of the Embodiments

[0067] Hereinafter, the present disclosure will be described in detail through examples. However, these examples are merely preferred examples given for illustrative purposes, and thus, the scope of the present disclosure is not intended to be limited to or by these examples. Meanwhile, those skilled in the art in the technical field of the present disclosure or similar technical fields can fully understand and easily implement the technical features not described herein.

[0068] In the foregoing, lysine granules and a method for producing lysine granules according to an aspect of the present disclosure have been examined. In the following, the beneficial effects mentioned in the present disclosure will be discussed based on the experimental results of the examples and comparative examples.

[0069] Experimental Example 1. Surface analysis of lysine granules according to relative humidity

[0070] In this experimental example, by changing the relative humidity of commercially produced lysine granules in a constant temperature and humidity environment, the changes on the surface of the lysine granules were observed.

[0071] Figures 3a to 3c is an image showing the surface of lysine granules according to the humidity in a constant temperature and humidity chamber.

[0072] Example 1. Preparation of 99% lysine granules (free base)

[0073] An aqueous amino acid solution is prepared by purifying a fermentation broth containing L-lysine. To prepare the fermentation broth, a Corynebacterium strain capable of producing L-lysine is precultured in 25 mL of a seed medium (pH 7.0) at 30 °C and 200 rpm for 20 hours. Based on 1 L of distilled water, the seed medium consists of: 20 g of glucose, 10 g of peptone, 5 g of yeast extract, 1.5 g of urea, 4 g of KH2PO4, 8 g of K2HPO4, 0.5 g of MgSO4·7H2O, 100 μg of biotin, 1 mg of thiamine hydrochloride, 2 mg of calcium pantothenate, and 2 mg of nicotinamide. The seed bacteria obtained by preculture are inoculated into a production medium (pH 7.0) at 4% (v / v) and cultured at 30 °C with sufficient aeration and agitation until all the added glucose is consumed, thereby obtaining the final fermentation broth. Based on 1 L of distilled water, the production medium consists of: 100 g of glucose, 40 g of (NH4)2SO4, 2.5 g of soy protein, 5 g of corn steep liquor solids, 3 g of urea, 1 g of KH2PO4, 0.5 g of MgSO4·7H2O, 100 μg of biotin, 1 mg of thiamine hydrochloride, 2 mg of calcium pantothenate, 3 mg of nicotinamide, and 30 g of CaCO3. After the culture is completed, the concentration of L-lysine in the fermentation broth is analyzed using HPLC (Waters Corporation, 2478). Microorganisms in the fermentation broth are removed using a membrane with a pore size of 0.1 μm. The fermentation broth from which microorganisms have been removed is passed through a cation exchange resin column so that L-lysine in the fermentation broth is adsorbed onto the resin column, thereby separating L-lysine from other impurities. The adsorbed L-lysine is recovered by desorbing it from the resin column using approximately 2N ammonia water, and then concentrated by heating under vacuum to prepare an aqueous L-lysine solution, and the solid matter in the aqueous solution is controlled to be about 50% during the concentration process. After the concentration step, the concentration of the aqueous L-lysine solution is 560 g / L, the pH is 10.2, the specific gravity is 1.13, and the purity is 99 wt%.

[0074] The granulation of the prepared aqueous solution is carried out as follows: The prepared aqueous solution is injected into a fluidized bed granulator at a rate of 15 mL / min, and then sprayed into the granulator at a nozzle pressure of 1.2 kg / cm 2 at 80 °C. The size of the prepared granules is selected by sieving to be about 0.425 mm to about 2.0 mm.

[0075] 99% lysine granules (free base) are shown to contain 99 wt% of lysine, 0.4 wt% of ions, 0.1 wt% of other amino acids, and 0.5 wt% of moisture.

[0076] Example 2. Preparation of 74% lysine granules (free base)

[0077] An aqueous amino acid solution is prepared by purifying a fermentation broth containing L-lysine. To prepare the fermentation broth, a Corynebacterium strain capable of producing L-lysine is precultured in 25 mL of a seed medium (pH 7.0) at 30 °C and 200 rpm for 20 hours. Based on 1 L of distilled water, the seed medium consists of: 20 g of glucose, 10 g of peptone, 5 g of yeast extract, 1.5 g of urea, 4 g of KH2PO4, 8 g of K2HPO4, 0.5 g of MgSO4·7H2O, 100 μg of biotin, 1 mg of thiamine hydrochloride, 2 mg of calcium pantothenate, and 2 mg of nicotinamide. The seed bacteria obtained by preculture are inoculated into a production medium (pH 7.0) at 4% (v / v) and cultured at 30 °C with sufficient aeration and agitation until all the added glucose is consumed, thereby obtaining the final fermentation broth. Based on 1 L of distilled water, the production medium consists of: 100 g of glucose, 40 g of (NH4)2SO4, 2.5 g of soy protein, 5 g of corn steep liquor solids, 3 g of urea, 1 g of KH2PO4, 0.5 g of MgSO4·7H2O, 100 μg of biotin, 1 mg of thiamine hydrochloride, 2 mg of calcium pantothenate, 3 mg of nicotinamide, and 30 g of CaCO3. After the cultivation is completed, the concentration of L-lysine in the fermentation broth is analyzed using HPLC (Waters Corporation, 2478). Microorganisms in the fermentation broth are removed using a membrane with a pore size of 0.1 μm. The fermentation broth from which microorganisms have been removed is concentrated by heating under vacuum to prepare an aqueous L-lysine solution, and the solid matter in the aqueous solution is controlled to be about 50% during the concentration process. After the concentration step, the concentration of the aqueous L-lysine solution is 418 g / L, the pH is 8.5, the specific gravity is 1.13, and the purity is 74 wt%.

[0078] Granulation of the prepared aqueous solution is carried out as follows: The prepared aqueous solution is injected into a fluidized bed granulator at a rate of 15 mL / min, and then sprayed into the granulator at a nozzle pressure of 1.2 kg / cm 2 at 80 °C. The size of the prepared granules is selected by sieving to be about 0.425 mm to about 2.0 mm.

[0079] 74% lysine granules (free base) are shown to contain 74 wt% of lysine, 12 wt% of ions, 0.8 wt% of other amino acids, 0.5 wt% of moisture, and about 13 wt% of other substances.

[0080] Example 3. For 99% lysine granules, the relative humidity is increased from 40% to at most 60% at a rate of 0.2% per hour

[0081] Put more than 300 g of the 99% lysine granules prepared in Example 1 into a plastic tray and place it in a thermo-hygrostat chamber at a temperature of 30 °C and a relative humidity of 40%. Thereafter, the relative humidity was increased to 60% at a rate of 0.2% per hour. Figures 3a to 3c Scanning electron micrographs of the surface of the lysine granules are shown before placing the lysine granules in the thermo-hygrostat chamber, at a relative humidity of 50% and at a relative humidity of 60%, respectively. It was confirmed that lysine hydrate crystals were coated on the entire surface of the lysine granules over time. Thereafter, drying was carried out in an oven dryer at a temperature of 70 °C for 24 hours to obtain lysine granules with lysine hydrate crystals coated on the surface.

[0082] It is shown that the surface-coated lysine granules contain 79 wt% lysine, 0.3 wt% ions, 0.1 wt% other amino acids and about 21 wt% moisture.

[0083] Example 4. For 74% lysine granules, the relative humidity was increased from 40% to at most 60% at a rate of 0.2% per hour

[0084] Put more than 300 g of the 74% lysine granules prepared in Example 2 into a plastic tray and place it in a thermo-hygrostat chamber at a temperature of 30 °C and a relative humidity of 40%. Thereafter, the relative humidity was increased to 60% at a rate of 0.2% per hour. Then, drying was carried out in an oven dryer at a temperature of 70 °C for 24 hours to obtain lysine granules with lysine hydrate crystals coated on the surface.

[0085] It is shown that the surface-coated lysine granules contain 64 wt% lysine, 10 wt% ions, 1 wt% other amino acids and about 11.4 wt% other components.

[0086] Example 5. For 99% lysine granules, the relative humidity was increased from 40% to at most 50% at a rate of 0.2% per hour

[0087] Put more than 300 g of the 99% lysine granules prepared in Example 1 into a plastic tray and place it in a thermo-hygrostat chamber at a temperature of 30 °C and a relative humidity of 40%. Thereafter, the relative humidity was increased to 50% at a rate of 0.2% per hour. Then, drying was carried out in an oven dryer at a temperature of 70 °C for 24 hours to obtain lysine granules with lysine hydrate crystals coated on the surface.

[0088] It is shown that the surface-coated lysine granules contain 86 wt% lysine, 0.4 wt% ions, 0.1 wt% other amino acids and about 14 wt% moisture.

[0089] The results of observing the surfaces of the lysine granules prepared according to Examples 3 to 5 above are asFigures 3a to 3c As shown, it was confirmed that after the prepared lysine particles were exposed to a constant temperature and humidity environment, changes occurred on the surface of the lysine particles. This indicates that lysine hydrate was provided on the surface of the lysine particles as described above.

[0090] Hereinafter, it was confirmed whether changes in physical properties (such as water absorption rate and caking rate) occurred when lysine hydrate was provided on the surface of the lysine particles as described above.

[0091] Experimental Example 2. Analysis of the content, water absorption rate, caking rate of lysine granules and the results after treatment in a constant temperature and humidity chamber and an oscillator Analysis of the results

[0092] The content, water absorption rate, caking rate of the lysine particles coated with lysine crystals on the surface obtained in Examples 3 to 5, and the results after treatment in a constant temperature and humidity chamber and an oscillator are shown in Figures 4a to 4c This disclosure aims to reduce impurities (such as anions), increase the content, and produce low-curing particles. Therefore, the water absorption rate and caking rate are used as indicators for determining curing. As the water absorption rate and caking rate increase, the hygroscopicity and curability of the product become significant, making the treatment more difficult.

[0093] In the following analysis, the water absorption rate was calculated as follows.

[0094] Water absorption rate (%) = ([mass of the sample after treatment in the constant temperature and humidity chamber] - [mass of the sample before treatment in the constant temperature and humidity chamber]) / [mass of the sample before treatment in the constant temperature and humidity chamber] × 100

[0095] In addition, for the purpose of comparison, 99% lysine particles (free base) of Example 1, 74% lysine particles (free base) of Example 2, and commercially available 79% lysine hydrochloride powder (CJ CheilJedang, Korea) and 64% lysine sulfate particles (CJ CheilJedang, Korea) were analyzed using the same method.

[0096]

[0097] Figures 4a to 4c

[0098]

[0098] When producing lysine granules at a content similar to that of the lysine hydrochloride powder product (79%), the granules coated with lysine crystals prepared in Example 1 by the method proposed in the present disclosure are cured at a level similar to that of lysine hydrochloride. In addition, the lysine granules have the advantages of reducing the adverse effects on animal nutrition, lowering the material cost of the product, and reducing the emission of environmental pollutants by eliminating or reducing the use of anionic substances such as hydrochloric acid and sulfuric acid.

[0099] When producing lysine granules at a content similar to that of the lysine sulfate granules (64%), the granules coated with lysine crystals prepared in Example 2 by the method proposed in the present disclosure are less cured than the lysine sulfate granules. In addition, this has the advantage of eliminating or reducing the use of anionic substances such as hydrochloric acid and sulfuric acid, as in Example 1.

[0100] When producing lysine granules at a content slightly higher than that of the lysine hydrochloride powder product (86%), the granules coated with lysine crystals prepared in Example 3 by the method proposed in the present disclosure are cured at a level similar to that of the lysine sulfate granules. This also has the advantage of eliminating or reducing the use of anionic substances such as hydrochloric acid and sulfuric acid, as in Example 1.

[0101] [Table 1]

[0102]

[0103] As can be seen from Table 1 above, the lysine granule products of Example 1 and Example 2 without a lysine hydrate shell on the surface have a high lysine content, but it is found that the water absorption rate and caking rate are very high. Therefore, this means that in a high-humidity environment, the quality of these products will be significantly reduced.

[0104] In contrast, the lysine hydrochloride powder product and the lysine sulfate granule product have relatively low water absorption rates and caking rates, but the lysine content is reduced. In particular, in the case of the lysine hydrochloride powder product, although the lysine content is slightly excellent and the water absorption rate and caking rate are also good, it is provided in powder form with a low caking rate, making it difficult to further form granules. Compared with the granule form, the powder form has the disadvantages of being more difficult to handle and perform subsequent processing.

[0105] Therefore, it is confirmed that the lysine granules according to the present disclosure can increase the lysine content while reducing the water absorption rate and caking rate by providing a shell containing lysine hydrate. In addition, when a shell containing lysine hydrate is provided on the surface of the lysine granules, as described above, the water absorption rate is significantly reduced. Therefore, it is found that after the lysine hydrate layer (shell layer) is formed to a certain depth relative to the lysine granules, it is difficult to generate lysine hydrate inside the lysine granules anymore.

[0106] Therefore, through this experiment, it was confirmed that lysine particles with a core-shell structure can be prepared by exposing lysine particles to specific humidity and temperature conditions.

[0107] Based on the foregoing, those skilled in the art to which the present disclosure pertains will be able to understand that the present disclosure can be implemented in other specific forms without modifying the technical concept or essential features of the present disclosure. In this regard, the exemplary embodiments disclosed herein are for illustrative purposes only and should not be construed as limiting the scope of the present disclosure. On the contrary, the present disclosure is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalent embodiments, and other embodiments that may be included within the spirit and scope of the present disclosure as defined by the appended claims.

Claims

1. A lysine granule having a core-shell structure, comprising: A core containing lysine; And A shell containing lysine hydrate, the shell being provided on the surface of the core.

2. The lysine granule according to claim 1, wherein the lysine content in the lysine granule is 64 wt% to 86 wt%.

3. The lysine granule according to claim 1, wherein the lysine granule is in the form of a free base.

4. The lysine granule according to claim 1, wherein according to Equation 1 below, the hydration rate of the lysine granule is 11% to 23%: [Equation 1] Wherein in Equation 1 above, W1 represents the lysine content (wt%) in the granule after the lysine granule is hydrated, and W0 represents the lysine content (wt%) in the granule before the lysine granule is hydrated.

5. A method for producing a lysine granule, comprising: A first step of preparing lysine in particulate form; And A second step of exposing the particulate lysine to a constant temperature and humidity device to provide a shell containing lysine hydrate on the surface of the particulate lysine, thereby producing a lysine granule having a core-shell structure.

6. The method according to claim 5, wherein In the second step, the particulate lysine is exposed to an environment with a relative humidity of 25% to 60%.

7. The method according to claim 6, wherein In the second step, the particulate lysine is exposed to an environment with a relative humidity of 40%, and then the relative humidity is increased to 50% to 60% at a rate of 0.2% per hour.

8. The method according to claim 5, wherein the particulate lysine is provided by preparing a fermentation broth containing lysine and then drying the fermentation broth.

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