Capsule drying method

Abstract

The present invention relates to a method for drying capsules having a shell formed from a gel wrap based on biopolymers, and to a method for rehydration of these capsules. The invention also relates to dehydrated capsules obtained by this drying process and to rehydrated capsules obtained by a rehydration process.

Description

[0001] The present invention relates to a method for drying capsules having a shell formed by a biopolymer-based gelatin coating and to a method for rehydrating these capsules. The invention also relates to dehydrated capsules obtained by the drying method and to rehydrated capsules obtained by the rehydration method.

[0002] Formulations in capsule form are widely used in various technical fields as they offer many advantages. Capsules in a dry state are easier to store and transport, especially by reducing the volume and weight of the capsules, and can also improve the stability of the product during storage.

[0003] Here, the present invention relates to a capsule drying method

[0004] Wherein, the capsule comprises a shell and a core,

[0005] The invention is characterized in that the core of the capsule is aqueous, or is an oil-in-water emulsion, or is an oil-in-water emulsion.

[0006] wherein the shell is a gel wrap based on at least one biopolymer;

[0007] Characterized in that the thickness of the shell is at least 10 μm;

[0008] Characterized in that the drying method comprises fluidized bed drying and / or freeze drying steps.

[0009] The present invention also relates to a dehydrated capsule obtained by the drying method of the present invention.

[0010] In the second stage, if the capsules are more effective in a hydrated form, they may be rehydrated, preferably prior to use.

[0011] Therefore, the present invention also relates to a method for rehydrating dehydrated capsules, comprising suspending the dehydrated capsules in an aqueous medium.

[0012] Finally, the present invention relates to rehydrated capsules obtained by the rehydration method according to the present invention.

[0013] Detailed description of the invention

[0014] capsule

[0015] "Capsule" herein refers to a capsule comprising at least one core and one shell. Preferably, such capsule has a liquid core, which is encapsulated by a nearly solid gel wrapping. Such capsules are used in many technical fields. The shell comprises one or more concentric or non-concentric compartments. Preferably, the capsule according to the present invention comprises only one core wrapped by a shell. Preferably, the average diameter of the capsule according to the present invention in hydrated form is less than 10 mm.

[0016] Thus, these capsules are very different from spherules, as spherules are primarily composed of a solid or gel matrix containing multiple small inclusions.

[0017] The use of capsules rather than pellets also allows for a larger volume of core to be accommodated.

[0018] According to a preferred embodiment of the present invention, the ratio of the core volume of the capsule to the total volume of the capsule is greater than 20%. Therefore, for a given volume of the shell, these capsules can protect a large volume of the core, thereby possibly protecting the active agent.

[0019] Preferably, the core / shell volume ratio of the capsules before drying is between 0.2 and 3, more preferably between 0.5 and 2.

[0020] Capsules are well known to those skilled in the art and can be made by different techniques and with different shell compositions.

[0021] Typically, the capsules used in the present invention are produced according to the manufacturing method described in French Patent No. 2939012.

[0022] As described below, the capsules of the present invention may be in dehydrated form. However, when they are in hydrated form, for example suspended in an aqueous solution, the average diameter of the capsules of the present invention is between 50 and 4000 μm, preferably between 100 and 2000 μm, more specifically between 200 and 1000 μm, advantageously between 200 and 600 μm. This average diameter can be measured by various techniques well known to those skilled in the art, such as particle size determination based on laser diffraction, sieve separation or optical microscopy imaging.

[0023] In one embodiment, the capsule of the present invention further comprises an intermediate layer between the core and the shell. Preferably, the intermediate layer is composed of at least one biopolymer in the form of a solution or a hydrogel.

[0024] core

[0025] The core of the capsule of the present invention may be aqueous, or in the form of an oil-in-water (O / W) or water-in-oil (O / W) emulsion. In one embodiment of the present invention, the core is an oil-in-water microemulsion.

[0026] Preferably, the core of the capsule of the present invention is a liquid core. Preferably, the viscosity of the core is less than 2000 mPa.s.

[0027] "Aqueous core" refers to a core that is predominantly based on an aqueous phase.

[0028] In this case, if the capsule core is in the form of an oil-in-water (O / W) or water-in-oil (W / O) emulsion, an oil or oil mixture may be used, preferably oils of vegetable, mineral or synthetic origin or mixtures thereof. "Oil" refers to a fatty substance that is liquid at ambient temperature (25° C.) and atmospheric pressure.

[0029] shell

[0030] Preferably, the capsule of the present invention comprises at least one core, which is enclosed by a nearly solid gelatinous covering (referred to as a "shell").

[0031] Preferably, the shell of the capsule of the present invention is mainly composed of a biopolymer with gelling properties, which accounts for a large proportion of the shell and is hereinafter referred to as the "main biopolymer". For example, the biopolymer with gelling properties can be alginate, gellan gum, xanthan gum, pectin, chitosan, agar or carrageenan.

[0032] Preferably, the material constituting the shell is biodegradable and bio-based. Preferably, the shell is semi-permeable to low molecular weight gases and molecules.

[0033] The gel forming the shell may be formed using physical or chemical processes, ie by coacervation or polymerization.

[0034] The gelation of these biopolymers can be achieved by temperature changes (gellan gum), pH changes (chitosan, pectin), or ionic changes (alginate, carrageenan).

[0035] Preferably, the shell of the capsule of the present invention is mainly composed of a biopolymer that obtains gel properties through ionic or temperature changes.

[0036] Preferably, the shell of the capsule of the present invention is mainly composed of alginate.

[0037] The shell may also include one or more biopolymers in addition to the primary biopolymer, such as starch (in various forms, such as amylose, pregelatinized starch), potato protein, or another biopolymer having gelling properties in addition to the primary biopolymer, such as alginate, gellan gum, xanthan gum, pectin, chitosan, agar, or carrageenan.

[0038] Preferably, the shell of the capsule of the present invention comprises a gel containing water, one or more biopolymers having gelling properties, and a surfactant which may result from the method of its manufacture.

[0039] Preferably, the shell of the capsule of the present invention comprises a gel comprising water and alkaline alginate and possibly a surfactant resulting from the method of its manufacture.

[0040] Preferably, the alkaline alginate is sodium alginate or potassium alginate. Alginates are produced by brown algae, the latter being known as Laminaria japonica, the English term "sea weed". The α-L-guluronic acid content of such alginates is advantageously greater than about 50%, preferably greater than 55% or even greater than 60%.

[0041] Advantageously, the surfactant is an anionic surfactant, a nonionic surfactant, a cationic surfactant or a mixture thereof.The molecular weight of the surfactant is between 150 g / mol and 10,000 g / mol, advantageously between 250 g / mol and 1500 g / mol.

[0042] In the case where the surfactant is an anionic surfactant, for example, it is selected from alkyl sulfates, alkyl sulfonates, alkyl aryl sulfonates, alkyl phosphates, dialkyl sulfosuccinates, alkaline earth salts of saturated or unsaturated fatty acids. Advantageously, these surfactants have at least one hydrophobic hydrocarbon chain with a carbon number greater than 5 or even 10 and at least one anionic hydrophilic group, such as sulfate, sulfonate or carboxylate connected to one end of the hydrophobic chain. In the case where the surfactant is a cationic surfactant, for example, it is selected from alkyl pyridine or alkyl ammonium halide salts, such as n-ethyl dodecyl ammonium chloride or ammonium bromide or hexadecyl ammonium chloride and ammonium bromide (CTAB). Advantageously, these surfactants have at least one hydrophobic hydrocarbon chain with a carbon number greater than 5 or even 10 and at least one cationic hydrophilic group, such as quaternary ammonium cations. In the case where the surfactant is a nonionic surfactant, for example, it is selected from polyoxyethylene and / or polyoxypropylene derivatives of fatty alcohols, fatty acids or alkylphenols, arylphenols, or selected from alkyl glucoside, polysorbate and coconut amide.

[0043] In one embodiment, the surfactant is sodium lauryl sulfate (SLS, also known as sodium cocoyl sulfate) and / or polyoxyethylene sorbitan monoester (polysorbate 80).

[0044] Preferably, the surfactant is polyoxyethylene sorbitan monoester (polysorbate 80).

[0045] In one embodiment, the mass content of the surfactant in the shell is greater than 0.001%, advantageously greater than 0.1%. Advantageously, the mass concentration of the surfactant is about 0.03%.

[0046] The shell may also contain other compounds to enhance its resistance to drying. Among these compounds, for example, biochar may be present. Preferably, the biochar is present in the shell at a volume fraction of 0.1% to 20%, advantageously at a volume fraction of 0.5% to 15%, preferably at a volume fraction of 1% to 10%.

[0047] If the capsule has an oily core, the shell may contain a sedimentation agent, i.e. an inert agent, preferably of a mineral nature, capable of making the capsule heavier. In fact, for capsules with an oily core, when they are placed in an aqueous liquid, they tend to rise to the surface, so a sedimentation agent is added to the shell to make it heavier, preferably so that the capsule is suspended in the aqueous liquid. For example, the sedimentation agent according to the invention may be chosen from talc and / or silica. In this case, the sedimentation agent is present in the shell in a volume fraction of 1% to 30%, advantageously in a volume fraction of 5% to 20%. However, a person skilled in the art will be able to estimate the amount of sedimentation agent required to achieve the desired effect, according to the density of the capsule and the liquid in which it is placed.

[0048] The capsule shell has a thickness of at least 10 μm. In fact, the inventors have shown that a shell of this thickness makes the capsules more resistant to drying. If the shell membrane is very thin, the capsules will be very fragile and will not be able to withstand the shear forces / mechanical stresses applied by, for example, operators when handling the capsules, or the stirring conditions of the capsules during physicochemical processing, and will be very likely to break.

[0049] However, a film that is too thick will result in a loss of advantage.

[0050] In particular, the capsule shell is therefore between 10 μm and 1200 μm, advantageously between 20 μm and 800 μm, more particularly between 20 μm and 400 μm.

[0051] In particular, relative to the diameter of the capsule, the thickness of the capsule shell is preferably between 0.1% and 30%, advantageously between 1% and 20%, more particularly between 10% and 20% of the capsule diameter.

[0052] Drying method

[0053] The present invention relates to a capsule drying method

[0054] Wherein, the capsule comprises a shell and a core,

[0055] The invention is characterized in that the core of the capsule is aqueous, or is an oil-in-water emulsion, or is an oil-in-water emulsion.

[0056] wherein the shell is a gel wrap based on at least one biopolymer;

[0057] Characterized in that the drying method comprises fluidized bed drying and / or freeze drying steps.

[0058] "Fluidized bed drying" refers to the process of bringing rising gas into contact with the particle layer (capsules in this case), and the airflow generated by the gas flow makes the capsules lighter. The capsule layer thus behaves like a fluid. This technique can increase the contact area between the gas and the capsules to facilitate drying. The fluidized bed drying of the present invention can be carried out on a simple fluidized bed, a vibrating fluidized bed or a fluidized bed with a built-in exchanger.

[0059] Preferably, the capsules of the present invention are coated with an anti-caking agent prior to fluid bed drying.

[0060] "Anti-caking agents" refer to agents that limit or prevent capsule aggregation or caking. Anti-caking agents are well known to those skilled in the art and include calcium carbonate, tricalcium phosphate, calcium silicate, magnesium silicate, calcium stearate, magnesium stearate, magnesium carbonate, magnesium oxide, silicon dioxide, sodium aluminosilicate, sodium ferrocyanide, potassium ferrocyanide, and mixtures thereof.

[0061] Preferably, the anti-caking agent is calcium carbonate.

[0062] The "coating" here means coating a layer of powder on the surface of the capsule.

[0063] "Freeze drying" refers to dehydration by removing water by sublimation. Preferably, the capsules are immersed in a bath of the auxiliary agent and then frozen at at least -80°C before freeze drying.

[0064] "Adjuvant" refers to an additional compound that is not biologically active itself and is intended to facilitate the operation of the capsule or to limit the degradation of the capsule.

[0065] For example, the auxiliary agent may be a cryoprotectant. Cryoprotectants that can be used in the present invention are glycerol, poly-L-lysine, lactose, trehalose, inulin, glutamic acid, sodium ascorbate, magnesium sulfate, sodium bicarbonate, sucrose, maltodextrin, milk powder and mixtures thereof.

[0066] In a preferred embodiment, the capsule is immersed in an additive bath containing sucrose, more preferably, the sucrose concentration is between 50 and 500 g / L.

[0067] In a preferred embodiment, the capsule is immersed in an additive bath containing maltodextrin, more preferably, the concentration of maltodextrin is between 50 and 500 g / L.

[0068] In a preferred embodiment, the capsule is immersed in an additive bath containing milk powder, more preferably, the concentration of milk powder is between 20 and 150 g / L.

[0069] The freezing step is performed at -80°C until the core of the capsule becomes solid. Preferably, the capsule is frozen at -80°C for at least 6 hours, more preferably, for at least 12 hours.

[0070] The drying process of the present invention can obtain capsules in a dehydrated form.

[0071] Preferably, the drying process can reduce the moisture weight of the capsules by at least 70%, advantageously by at least 80%, more particularly by at least 90%.

[0072] Preferably, the dehydration is localized and the moisture content of the resulting capsules is less than 10%, as measured by a moisture analyzer after dehydration.

[0073] The present invention also relates to a dehydrated capsule obtained by any one of the dehydration methods described in the present invention.

[0074] Preferably, the moisture content of the obtained capsules is less than 10% (by weight), measured by a moisture analyzer after dehydration.

[0075] In dehydrated form, the average diameter of the capsules tends to decrease. Preferably, the average diameter of the capsules of the present invention in dehydrated form is from 10 μm to 4 mm.

[0076] Rehydration method

[0077] The present invention relates to a method for rehydrating a dehydrated capsule. Preferably, for the dehydrated capsule of the present invention, the method comprises suspending the dehydrated capsule in an aqueous medium.

[0078] Preferably, the aqueous medium is mainly composed of water, preferably purified water, such as ultrapure water. The aqueous medium can be physiological water, ie, purified water containing 0.9% (w / v) sodium chloride.

[0079] Specifically, the aqueous medium may be water to which a surfactant, such as Tween, is added.

[0080] Therefore, in one embodiment of the present invention, if the dehydrated capsules do not contain organisms or microorganisms, the rehydration method comprises suspending the dehydrated capsules in ultrapure water.

[0081] In another embodiment of the present invention, if the dehydrated capsules contain bacteria and / or viruses, the rehydration method comprises suspending the dehydrated capsules in physiological water.

[0082] In another embodiment of the present invention, if the dehydrated capsules contain fungi or spores, the rehydration method comprises suspending the dehydrated capsules in an aqueous medium to which a surfactant is added, preferably physiological water to which Tween is added.

[0083] Preferably, the dehydrated capsules are suspended in the aqueous medium for at least 30 minutes, preferably 30 minutes to 1 hour. Preferably, the dehydrated capsules are suspended at ambient temperature, ie between 10° C. and 25° C. Preferably, the suspension is facilitated by stirring.

[0084] The present invention also relates to a rehydrated capsule obtained by the rehydration method of the present invention.

[0085] In the specification and the following examples, unless otherwise indicated, percentages are percentages by weight, and numerical ranges are expressed in the format of "between ... and ...", "... to ..." or "greater than ..." (limits indicated).

[0086] Throughout the application, unless otherwise specified, "comprising a" or "including a" means "comprising at least one" or "including at least one".

[0087] The following examples present the field of the invention in an illustrative and non-limiting manner.

[0088] Embodiment 1: Freeze drying of capsules and their rehydration testing

[0089] Two alginate capsule prototypes were tested, in which the biochar contained in the capsule core was used as a probe to estimate and / or quantify the amount of degraded capsules and / or the amount of probe lost during freeze-drying and rehydration.

[0090] The first prototype (Prototype 1) contained biochar only in the capsule core. The second prototype contained biochar in both the core and the shell. The biochar incorporated into the capsule shell had the effect of hardening the shell.

[0091] The alginate capsule prototypes were formed under the following production conditions:

[0092] The nozzle diameter was 200 μm. The total flow rate of the core and shell fluids (ie, Qtot) was 450 ml / h, the flow rate ratio between the core and shell fluids (ie, Rq) was 0.8, and the film thickness was at least 30 μm.

[0093] The capsules are made by soaking in a calcium chloride bath. A sample of the calcium chloride bath is taken to determine the amount of biochar present in the bath. This is the proportion of biochar that has not been encapsulated (encapsulation is slightly less than 100%). The capsules are then collected and washed with water to remove the biochar deposited on the surface of the capsules.

[0094] Wet capsule samples were taken to determine the amount of biochar contained in the capsules. To do this, the capsules were soaked in a PBS / EDTA solution to dissolve the alginate shell and release the contents. The addition of PBS helped maintain physiological conditions, including ionic strength and solution pH.

[0095] The remaining capsules were then soaked in an additive bath (SM sucrose, ie, a bath containing 300 g / L sucrose) and frozen at -80°C.

[0096] The capsules were then freeze-dried. After freeze-drying, they were suspended in an ultrapure aqueous solution, washed to release in the continuous phase, and the amount of biochar produced by rupturing the capsules during the freezing / freeze-drying stage was determined. After the washing step, samples were taken to determine the amount of biochar the capsules contained.

[0097] The columns marked "Hydrated capsules" and "Dehydrated capsules" include OD (optical density) measurements and estimates of the amount of biochar recovered after dissolution of the capsules. This dissolution is achieved by dissolving the alginate hydrogel that constitutes the capsule shell. For this purpose, a PBS / EDTA solution (phosphate / ethylenediaminetetraacetic acid buffer) is used, and the contents of the capsules are released in the continuous phase. In fact, EDTA has a chelating effect on the calcium ions present in the shell.

[0098] Columns called "calcium bath" and "wash buffer" include the amount of probe lost in these baths or buffers.

[0099] [Table 1] Table 1: Determination of the amount of biochar in each treatment step of Prototype 1

[0100]

[0101] Therefore, proportionally, the [hydrated capsules wash buffer] portion accounted for 7% of the total biochar, while the [dehydrated capsules] portion accounted for 100-7.06=92.94%.

[0102] Therefore, for Prototype 1, the biochar lost during freeze-drying was estimated to be only 7%.

[0103] [Table 2] Table 2: Determination of the amount of biochar in each treatment step of Prototype 2

[0104]

[0105] Therefore, the biochar loss during freeze drying was estimated to be only 0.5% for Prototype 2. Therefore, if biochar was present in the capsule shell, the loss of biochar was reduced 10 times, from 7% to 0.5%.

[0106] Embodiment 2: Freeze drying of capsules containing bacteriophages and rehydration testing

[0107] Two alginate capsule prototypes were tested in which bacteriophage contained in the capsule core was used as a probe to quantify the amount of degraded capsules and / or the amount of probe lost during freeze-drying and rehydration.

[0108] The first prototype (Prototype 1) contained no biochar. The second prototype (Prototype 2) contained biochar in the shell.

[0109] The alginate capsule prototypes were formed under the following production conditions:

[0110] The total flow rate of the core and shell fluids (ie, Qtot) was 500 ml / h, and the flow rate ratio between the core and shell fluids (ie, Rq) was 0.8.

[0111] The average diameters of the two capsule prototypes were 462 μm (coefficient of variation 17%) and 542 μm (coefficient of variation 18%). The shell thickness of these prototypes was at least 30 μm.

[0112] The phage of the M13K07 strain is a lytic phage that selectively and specifically targets the bacterial pathogen, namely Escherichia coli.

[0113] [Table 3] Table 3: Phage quantity determination during capsule formation and drying

[0114]

[0115] [Table 4] Table 4: Evaluation of phage loss during capsule drying

[0116] prototype Wet capsule loss Dry capsule loss Prototype 1 1.3％ 96％ Prototype 2 <0.1％ 94％

[0117] The calculation method is as follows:

[0118]

[0119] The "calcium bath encapsulation efficiency" was calculated by measuring the amount of unencapsulated phage remaining in the bath and calculating the ratio of this to the amount of phage used during capsule formation.

[0120] [Table 5] Table 5: Phage encapsulation efficiency

[0121]

[0122] The loss of phage viability during freeze-drying was estimated to be 5%.

[0123] Embodiment 3: Fluidized bed drying test of capsules

[0124] Fluidized bed drying of alginate capsule prototypes containing bacterial strains was tested. The alginate capsule prototypes were formed under the following production conditions:

[0125] The nozzle diameter was 150 μm. The total flow rate of the core and shell fluids (ie, Qtot) was 350 ml / h, the flow rate ratio between the core and shell fluids (ie, Rq) was 1, and the film thickness was at least 20 μm.

[0126] After production and washing with physiological water, the capsules are mixed with calcium carbonate in a mass ratio of 1:1 and then dried on a fluidized bed for 30 minutes. The temperature reached inside the shell is kept below 45°C.

[0127] After drying, the capsules were washed by resuspending in physiological water to remove calcium carbonate. Capsule samples were taken to determine the bacterial concentration contained in the capsules.

[0128] The bacterial concentrations in the wet and dry products were 5.48×10 8 CFU / g and 4.11×10 5 CFU / g. The inventors observed that after drying in the fluidized bed, the bacterial concentration of the prototypes remained relatively high.

Claims

1. Capsule drying method It is characterized in that The capsule comprises a shell and a core, The invention is characterized in that the core of the capsule is aqueous, or is an oil-in-water emulsion, or is an oil-in-water emulsion. Characterized in that the shell is a gel wrap based on at least one biopolymer; Characterized in that the thickness of the shell is at least 10 μm; Characterized in that the drying method comprises fluidized bed drying and / or freeze drying steps.

2. The capsule drying method according to claim 1, characterized in that: The shell is mainly composed of alginate.

3. The drying method according to any one of claims 1 to 2, characterized in that The core / shell volume ratio of the capsules before drying was between 0.5 and 2.

4. The drying method according to any one of claims 1 to 3, characterized in that The capsules are immersed in a bath of the aid and then frozen at at least -80°C and then freeze-dried.

5. The drying method according to any one of claims 1 to 3, characterized in that Prior to fluid bed drying, the capsules of the present invention are coated with an anti-caking agent.

6. The dehydrated capsule can be obtained by the method according to any one of claims 1 to 5.

7. The method of rehydrating a dehydrated capsule according to claim 6, comprising suspending the dehydrated capsule in an aqueous medium.

8. A rehydrated capsule obtainable by the capsule rehydration method according to claim 7.

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