Methods of drying biological products.

A method of making particles containing a biologically produced substance in a polymeric material matrix

Biologically produced substances are usually obtained initially in dilute aqueous solutions. For example, natural products can be extracted from plants by squeezing or solution extraction to form an aqueous solution containing the natural product, and the fermented products are prepared in the fermentation broth by fermentation. Examples are macromolecular agents such as xanthan and other microbial polysaccharides, enzymes, spores, fungal mycelium, bacteria and cellular materials.

The fermentation broth can be concentrated to a broth concentrate by conventional methods such as filtration (e.g. centrifugation) and / or ultrafiltration and can be assisted, for example, by flocculation. However, the concentrate still contains a fairly large amount of water. It is therefore necessary to evaporate it. Likewise, evaporation of plant extracts is essential.

Many biologically produced substances are sensitive to damage when exposed to heat, so it is necessary to try to avoid overheating even on a microscopic scale during drying.

It is often desirable, or in some cases necessary, to obtain the dried, biologically produced material in particulate form containing the substance enclosed in a polymeric material that is either in a shell around the biological substance or as a matrix into which the biological substance is distributed. For example, one widely used method for drying fermentation broths is spray drying, but spray drying has the difficulty of generating a lot of dust and dusting the product can cause serious problems. The process must therefore be carried out under closely controlled conditions and the agglomeration of the product is

II is generally necessary, for example by spray-drying with a binder or by adding a binder to the dried product. Dusting is a problem even then and dry drying can damage the fermentation product. For example, enzyme activity can be significantly reduced in spray drying an enzyme-containing broth or concentrate.

Attempts to combine encapsulation with drying of the enzyme solution have been made. Thus, in JP 75-22 506, a polysaccharide or polyacrylamide polymer is added to the enzyme solution before spray-drying, in DE 2 435 008 an enzyme-based

EP 0 128 661 and 0 180 366 describe drying methods for polysaccharides in which the fermentation concentrate is emulsified in a water-immiscible liquid and then either distilled azeotropically to form a concentrated dispersion or spray-dried. However, these methods do not provide the desired polymer matrix.

A process by which this is possible is described in EP 0 284 367, but requires the formation of a polymer matrix from the monomer by polymerization in the presence of a microbial polysaccharide, which has certain disadvantages. Other methods are known in which a biological agent is introduced into a monomer mixture which is polymerized to form a polymer matrix. For example, in Chemical Abstractis, 85 147053J, the enzyme can be encapsulated in particles formed by a crosslinked acrylamide / acrylic acid copolymer after first mixing with the monomer prior to suspension polymerization. However, some biological agents slow polymerization. The sensitivity of others decreases when they come into contact with monomers or other components present during the polymerization process. In particular, the polymerization is generally exothermic and many of the active ingredients are sensitive to the high temperatures that develop in the polymer matrix during polymerization. For example, the active ingredient may be deactivated or may evaporate from the polymerization solution. In that case, it is generally necessary not to expose the enzymes to the temperatures prevailing in conventional bead polymerization or other exothermic polymerization processes.

Methods have been proposed to minimize the disadvantages of exothermic polymerization (see, e.g., EP 239,633 and Chemical Abstracts Vol. 95,81582c). However, all of these methods pose serious practical problems. It is also known to use a polymerization mixture consisting of a monomer and a difunctional low molecular weight crosslinking polymer (U.S. Patent 4,177,056), but even in this process the active ingredient is subjected to monomer and exotherm.

In WO 83/03102 the active substance is either mixed with monomers which are then polymerized (causing the above disadvantages) or mixed preformed into a polymer solution which is dispersed in an anhydrous medium and gelled in that medium by, for example, cooling, crosslinking, neutralization and subsequent heating. reaction. All of these methods are quite difficult to perform successfully and it is particularly difficult to obtain particles with sufficient physical strength. The method may be suitable for the preparation of laboratory reagents, but is not suitable for large-scale commercial production.

In JP-A 61-254 244, an enzyme and a water-soluble polymer are dispersed in a hydrocarbon liquid and

II then acetone is added. Although the use of a culture medium is mentioned, it is clear that the purpose is to precipitate the polymer around the enzyme and not to form a matrix into which the enzyme would be distributed, and a previously dried enzyme can be used for this purpose. If the polymer shell is damaged, the entire enzyme core is exposed to the environment. Our aim is to distribute the enzyme throughout the polymer matrix, thus avoiding that hazard.

JP-A 63-105 098 discloses rather large (e.g. 150-800 μm) microcapsules suitable for use in liquid or gel detergents, and one method mentioned, but without examples, involves dispersing an enzyme, a polyhydroxy compound and an aqueous phase containing polyvinyl alcohol. in a hydrophobic solvent and then removing the water by heating or depressurizing.

GB 1 353 317 describes various methods for forming a precipitated complex from an enzyme and an anionic polymer and in Example 2 this is accomplished by adding a specific polymer solution to the concentrated culture filtrate and subsequent acid addition to form a precipitate which is then filtered and washed with acetone.

If a method of recovering a dry biological material distributed in a polymer matrix is ​​to be commercially viable, it must be possible to perform it on a reproducible scale on a large commercial scale, but none of the methods described in the literature allow this possibility.

The invention produces particles containing a biologically produced substance distributed in a matrix of polymeric material.

More specifically, the invention relates to a process for preparing particles containing a biologically produced substance in a polymeric material matrix, the polymeric material being mixed with an aqueous solution containing the biologically produced substance as a fermentation broth or plant extract to form an aqueous polymeric phase substantially uniformly distributed. , that simultaneously or thereafter, the aqueous polymer phase containing the biological agent is dispersed in a water-immiscible liquid in the presence of a dispersion stabilizer to form a substantially stable dispersion, and the dispersion is azeotropically distilled to form substantially dry particles, each of which consists of a polymeric material matrix.

A major advantage of the process of the invention is that it provides the desired polymer particles in one step, starting from the aqueous fermentation broth or aqueous plant extract in which the biological agent is first produced. Thus, in the invention, it is not necessary to extract the biological substance from its original solution and dry it, e.g. by spray-drying, before incorporating it into the polymer, but instead the process according to the invention is a simultaneous recovery and encapsulation process. Thus, the method avoids, for example, the difficulties of spray-drying and subsequent agglomeration or encapsulation.

It avoids exposure of the fermentation product to exotherm, initiator and other conditions associated with the polymerization mixtures. Drying can be performed under closely controlled conditions, avoiding overheating at both the macro and micro levels. Because the heating can be closely controlled, it is possible to minimize the risk of deactivation of the biological agent and thus it is possible to produce particles with satisfactory biological activity, often significantly higher than what is conveniently achieved by known recovery methods.

Essential! the size of the dry particles is determined by the size of the aqueous phase particles dispersed in the immiscible liquid. It is often desirable for the dry particles to be in the form of beads having a size of at least 30, often at least 100, for example up to 500 or 1 mm, even 2 mm or more. When the particles are of substantially this size, the particles are separated from the water-immiscible liquid by filtration, centrifugation or other conventional separation methods, and after separation they can be further dried. Further drying can take place by solvent exchange, although preferably with warm air, for example on a fluidized bed.

The beads should be dried sufficiently so that they are not sticky and are usually dried to or below the ambient moisture content.

A particular advantage of the invention is that it is possible to easily produce beads of regular shape and with little variation in size. This is possible only because the drying takes place by azeotropic distillation and because the active ingredient and the polymer are first dispersed in a water-immiscible liquid.

Although the production of such beads is often advantageous, another advantage of the method is that it is also possible to produce much smaller dry particles. The particles can thus be smaller than 30, usually for example less than 10 and often less than 3. When separating such particles from a water-immiscible liquid, dusting problems are possible and the particles are preferably left as a stable dispersion in the water-immiscible liquid. It is not necessary to dry them to humidity, but their moisture content can be left, for example, 25% of the polymer. Preferably, however, they are dried to air humidity or drier, e.g. to less than 10% moisture based on the polymer.

One important feature is that the biological agent is not only protected by encapsulation in a polymer shell (which is susceptible to damage) but instead is protected by partitioning into a polymer matrix. In order to form a continuous matrix and to provide strength to the particles, the release properties and other properties of the polymer must be used sufficiently. In general, this means that the amount of polymer must be at least 0.5 times the amount of active ingredient (based on dry weight). Preferably there is an excess of polymer, for example at least twice the amount of active ingredient, and preferably the excess is large, for example at least 7 times. The use of a 7-fold (or greater) excess of polymer means that the biological agent is effectively protected from the environment and even when the particles are damaged, the amount of active ingredient that may be exposed to or enter the environment is very low. In general, the amount of polymer is at least 10 times and usually at least 15 times the amount of active ingredient (based on dry weight). It is usually not necessary to use more than 50-fold amounts, and often 15 to 30-fold amounts are suitable, although amounts of up to 100-fold or greater may be used.

Small amounts of filler or other additives may be added to the matrix. In general, the polymeric material contains at least 50% by weight, more preferably at least 75% by weight, most preferably at least 90% by weight of a solid composition consisting of a matrix, an active ingredient distributed therein and other inert material.

The biologically produced substance to be encapsulated by the method of the invention may be a plant extract, for example natural oil or other essence or flavoring, pressed or extracted from a plant or part thereof, or it may be a fermentation product such as an enzyme, fungus, spore, bacterium or cell. a metabolite, for example an antibiotic. When it is a plant extract, the aqueous medium is usually a dilute aqueous solution of natural oil or other essence.

When it is a fermentation product, which is preferred, it may initially be introduced as a fermentation broth, which may be the fermentation broth itself or a filtrate or concentrate obtained therefrom. For example, when the biologically produced substance is a soluble component, such as an enzyme, the broth is often first filtered to remove insoluble cellular material. Conventional concentration and filtration methods, such as flocculation and ultrafiltration, are suitable for concentrating or filtering the broth prior to use in the invention.

The invention is particularly valuable when the active ingredient is one which would be disturbed or damaged by the monomer used to make the polymer or which tends to be inactivated (either by evaporation or loss of sensitivity) upon exposure to exothermic polymerization. The invention is therefore particularly valuable when the active ingredient is a sensitive substance which easily loses its sensitivity.

A particularly preferred type of active ingredient is an enzyme. Preferably, the enzyme is a protease, in particular a basic protease of the type used in washing powders and other detergents, but other suitable enzymes are used. purposes are amylases and lipases.

Of course, if the enzyme is to be included in a solid detergent, the particles of the invention are in the form of beads. If it is to be included in a liquid96036 detergent, it is usually a product in the form of dispersion particles in an anhydrous liquid.

Another preferred type of active ingredient 5 is an agriculturally or medically useful microbial product, such as an antibiotic for human and / or veterinary use, a bio-insecticide, a bio-herbicide or a biofertilizer.

An example is Bacillus Thuringiensis, an insect10 venom. In this and many other microbial products, cells can be encapsulated either dead or alive because the toxic protein in the cell is needed and not the living cell itself. In some cases, however, it is desirable for the cell in the polymer matrix to be viable so that it can be metabolized and replicated as soon as it is released from the matrix, e.g., on a leaf surface, in soil, or at some point in the digestive tract.

Other suitable biological agents include bacteria or enzymes derived from bacteria that are suitable for use in the production of silage or compost to promote the processes necessary for the fermentation of silage or compost. Other suitable biological agents include enzymes or whole cells that can be used to break down fats, cellulose, or proteins, or to remove nitrates or heavy metals from wastewater or, for example, from water treated for drinking water use.

The polymer should be film-forming in the sense that the polymer residue forms a uniform matrix after most or all of the water has been removed by azeotropic evaporation.

The polymer is preferably soluble in an aqueous solution containing the biologically produced substance and may be introduced into the aqueous liquid either as a preformed aqueous solution or in any other suitable form. The polymer may be a natural polymer or modified

II polymer such as starch or cellulose (e.g. carboxymethylcellulose) or rubber. Preferably, it is a synthetic polymer consisting of an ethylenically unsaturated water-porous monomer or monomer mixture, the monomer being either ionic or uncharged.

Suitable anionic monomers include ethylenically unsaturated carboxylic acid or sulfonic acid monomers, most preferably monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, (meth) allylsulfonate, vinylsulfonyl acid and 2-vinylsulfonic acid and 2-acylosulfonic acid. Acrylic or methacrylic acid is preferred.

Suitable cationic monomers include dialkylaminoalkyl (meth) acrylamides and preferably acrylates, usually in the form of acid addition or quaternary ammonium salts. Particularly preferred are monomers such as diethylaminoethyl (meth) acrylate.

Suitable uncharged monomers of this type include (meth) acrylamide and hydroxy-lower alkyl (meth) acrylates. The anionic or cationic monomers may be either the free acid or the free base if they are sufficiently soluble in this form (e.g. acrylic acid), but more usually the anionic monomer is in the form of an alkali metal or ammonium salt and the cationic monomer is an acid addition or quaternary ammonium salt.

The preferred polymer is usually based on 0-50% acrylamide and 50-100% acrylic acid or a soluble salt thereof.

The soluble polymer may be prepared by any conventional polymerization method, such as, for example, reverse phase suspension polymerization, solution polymerization, reverse phase bead polymerization, or gel polymerization. Alternatively, the polymer may be a copolymer of a soluble and an insoluble monomer (e.g. methacrylic acid and ethyl acrylate) and can be prepared by oil-in-water emulsion polymerization followed by the addition of sodium hydroxide or other base to convert the copolymer to a soluble form.

Instead of being introduced in a soluble form, the polymer may be insoluble in water but soluble in a base and may be introduced as a water-in-oil emulsion prepared by emulsion polymerization from an ethylenically unsaturated monomer or a monomer mixture insoluble in the aqueous phase of the polymerization mixture. In general, the monomer is a mixture of an anionic solubilizing monomer (typically an anionic monomer as described above) and an ethylenically unsaturated uncharged monomer, the entire mixture being insoluble at the pH of the emulsion. Emulsion polymerization can take place at a pH below 7, but if the polymer is then subjected to more basic conditions, it becomes Porous (or highly swellable). Suitable uncharged water-soluble monomers are alkyl (meth) acrylates, styrene, acrylonitrile, vinyl chloride, vinyl acetate or vinyl butyl ether. Ethyl acrylate is preferred, with the polymer preferably comprising 10 to 70% methacrylic acid or other anionic monomer, 10 to 70% ethyl acrylate or other insoluble monomer, and 0 to 70% acrylamide or other soluble uncharged monomer.

This type of emulsion polymerization is particularly useful when the polymer matrix is ​​not desired to release substantially no biological agent in any environment (e.g., neutral or acidic), but is desired to be rapid in a basic environment.

Controlled release of a biological agent can also be obtained by initially introducing the polymer from an ethylenically unsaturated carboxylic acid monomer, such as a salt of a polymer derived from (methacrylic acid monomer and a volatile amine (e.g., ammonia).) The salt is water soluble but less ammonia or other volatile amine. In addition, at least the outer shell of the particles, possibly substantially the entire polymer matrix, should be less hydrophilic and water-soluble than when the carboxyl groups are in base or amine salt form. Therefore, the particle has a relatively low permeability to ambient moisture, but when exposed to a slightly alkaline (e.g., typically present in the wash liquor) aqueous solution, the polymer dissolves sufficiently to allow rapid release of the entrapped enzyme or other biological agent. Therefore, the polymer is preferably based on 0-50% acrylamide and 50-100% acrylic acid or preferably methacrylic acid. Products of this type are described in more detail in our FI patent application 89 39 58 filed on the same day.

The choice of molecular weight of the polymer takes into account the required concentrations and solution viscosities, and in particular the strength of the gel for the final beads. If the molecular weight of the solution polymer is too high, it can be difficult to form a stable dispersion of aqueous polymer particles containing a commercially useful concentration of the active ingredient, so for many polymers the molecular weight should be less than 1 million, often less than 500,000. If the molecular weight is too low, the final gel strength may be insufficient, even if the surfaces of the beads are crosslinked. In some cases, the molecular weight may be as low as, for example, 4,000 or even 2,000. A range of 5,000 to 300,000 is often appropriate.

The polymers used in the invention may be inactive, i.e. polymers which cannot undergo any significant chain elongation, although crosslinking via side groups may be possible, as such crosslinking does not normally cause any significant exotherm or other conditions potentially damaging the active ingredient. It is also possible to use a polymer which undergoes chain elongation by addition polymerization during the process, provided that it does not involve harmful amounts of initiator, exotherm or other conditions which could damage the active ingredient. This possibility can be minimized by ensuring that the reactive polymer already has the correct chain length, for example a chain of at least 50 and usually at least 100 carbons. Depending on the degree of unsubstitution of the reactive polymer, the final polymer may be linear or crosslinked, and when crosslinked, the polymer matrix should be swellable rather than soluble. Preferred reactive polymers are described in EP 0 328 321.

The polymer may be crosslinked before or after or preferably during azeotropic distillation. For example, it is known that many polymers, especially those containing anionic groups, can crosslink when exposed to polyvalent metal compounds, so the addition of such components to an aqueous or non-aqueous liquid of the polymer, or both, can result in crosslinking. If the polyvalent metal compound is primarily soluble in an anhydrous liquid (e.g., aluminum isopropoxide or other polyvalent metal alkoxide), then the crosslinking is primarily concentrated on the surface of the particles. If the crosslinking agent is primarily soluble in the aqueous polymer solution, crosslinking can occur substantially uniformly throughout the particles. Crosslinking agents such as glutaraldehyde can be used for suitable polymers.

By appropriately selecting the type and amount of crosslinking, it is possible to control the physical properties of the particles. For example, it is possible to control the release of the active ingredient from the particles and / or to adjust the gel strength of the particles and / or to increase the hardness or reduce the surface tack. Also, if crosslinking is concentrated on the surface of the particles, the resulting particles tend to dissolve more rapidly in water.

Instead of achieving crosslinking during the process of the invention, it is also possible (especially when the polymer is originally prepared as an oil-in-water emulsion) to use a polymer that is originally crosslinked. In general, however, the polymer is linear and prepared substantially without crosslinking monomer or other crosslinking agent.

The polymer may act as a controlled release at, for example, the pH conditions described above, or may be merely a relatively inert material that binds the biological agent to the desired dust-free particles and allows release at the appropriate time, or may provide useful properties in an environment where the biologically active agent is to be used. . Especially when the biological agent is an enzyme to be added to the detergent, it is particularly desirable that the polymer of the polymer matrix be useful as a detergent component, for example as a detergent builder or detergent settling agent. Suitable polymers include carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl alcohol, and anionic synthetic polymers, for example, polymers of ethylene and (meth) acrylic acid and other polymers, preferably having a molecular weight of 4 to 300,000. with. Preferably, the polymer is sodium polyacrylate, but arylamide copolymers and, for example, allyl sulfonate or 2-acrylamidomethylpropane sulfonate homopolymers may be used. Copolymers of maleic anhydride with, for example, acrylic acid are also suitable.

The polymeric material can be mixed with a fermentation broth or other aqueous solution containing a biological agent to form an aqueous polymer phase containing both the polymer and the biological agent, and said phase can then be dispersed in a water-immiscible liquid. Alternatively, the fermentation broth or plant extract may be dispersed in a water-immiscible liquid and the polymer then added (usually as a preformed solution or emulsion) or alternatively the polymer may be dispersed and the fermentation broth or plant extract then added. In either case, the mixing must be sufficient to ensure that the aqueous particles dispersed in the water-immiscible liquid are substantially homogeneous in both polymeric and biological content.

The aqueous phase itself must be substantially stable, since if a tendency to phase separation occurs, it will interfere with the formation and maintenance of a uniform dispersion in the water-immiscible liquid. Therefore, the aqueous phase is preferably one in which the volume is stable and in which the phases do not separate. If the active ingredient is ionic, the polymer is preferably uncharged or has a mixed charge, for example when the biological substance is a slightly cationic enzyme, there is a risk that some of the anionic polymers will cause instability, in which case the aqueous phase should be stabilized. It can take place by thickening and / or adding an aqueous phase, in particular sucrose or another sugar or glycol or another low molecular weight polyhydroxy compound, e.g. propylene glycol.

The aqueous phase may also contain other additives which are optional depending on the intended use of the final product. For example, the solution may often contain inert fillers, such as clays and / or pigments or colorants.

The resulting dispersion with aqueous particles containing polymer and active ingredient must be sufficiently stable to be azeotropically distilled, and for this purpose it is generally necessary to add a polymeric dispersion stabilizer or sometimes also an emulsifying surfactant to the dispersion.

The concentration of the polymer in the polymer solution is selected according to the molecular weight of the polymer and the viscosity of the solution, but is generally in the range of 5 to 50%, typically 20 to 30%.

The particle size of the aqueous droplets and the final dry particles can be adjusted by the choice of shear force on the dispersion, the choice and amount of stabilizer, and the choice and amount of surfactant. When the final product is to be a stable dispersion in an oil or other immiscible liquid, it is preferred to use a water-in-oil emulsifier to promote the formation of small particles smaller than 10, for example less than 3. However, if beads, such as more than 30 and usually more than 70, are desired, the emulsifier may be omitted.

A polymer stabilizer is an amphipathic stabilizer formed, for example, from hydrophilic and hydrophobic acrylic acid monomers. Suitable surfactants, anhydrous liquids and polymer stabilizers, as well as suitable azeotropic distillation conditions are disclosed, for example, in EP 0 128 661 and 0 126 528. The stabilizers disclosed in GB 2 002 400, or preferably 2 001 083 or 1 482 515, are particularly preferred.

A water-immiscible liquid is anhydrous and must contain a liquid that forms an azeotropic water t

with. Often, a water-immiscible liquid is a mixture of a relatively high-boiling liquid remaining in the dispersion and a low-boiling liquid azeotropically distilling from the dispersion. The temperature at which azeotropic distillation takes place is generally below 100 ° C and can be controlled by the choice of liquid and especially by the pressure at which the distillation takes place. Generally, the distillation is carried out under reduced pressure and the active ingredient is heat-sensitive (e.g. enzyme) the vacuum is generally such that the azeotropic distillation takes place at a maximum temperature of at most 80 ° C, often below 70 ° C and most preferably below 50 ° C. For example, by using a high vacuum, it is possible to carry out azeotropic distillation at very low temperatures, for example as low as 30 ° C. Sodium sulfate or other salts may be added to lower the azeotropic distillation temperature.

The polymer should form a film at the distillation temperature and usually should form a film at 20 ° C or below.

After the water has been azeotroped sufficiently from the particles to convert to a substantially solid and non-sticky form, the particles (if large enough) can then be separated from the anhydrous liquid and further dried in a conventional manner, for example on a fluid bed.

Before or after azeotropic distillation, the particles can be surface treated to set the desired properties. For example, a polymer containing a relatively insoluble monomer as a water-soluble salt can be converted to a less soluble form (e.g., sodium methacrylate on the surface of the particles can be converted to methacrylic acid). A relatively insoluble polymer or other hydrophobic material (e.g. an oil-in-water emulsion polymer which dissolves when the particles are mixed with the wash water can be used).

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Here are some examples.

Example 1

A 25% aqueous solution of sodium polyacrylate having a molecular weight of 30,000 is formed and mixed with an appropriate amount of fermentation broth containing a basic detergent protease (or amylase or lipatase) to give a polymer: enzyme dry weight ratio of 19: 1. The solution is mixed with paraffin oil in the presence of an amphipathic polymeric stabilizer consisting of stearyl methacrylate, methyl methacrylate and methacrylic acid. The resulting dispersion is azeotroped under reduced pressure so that the maximum temperature of the dispersion does not exceed about 50 ° C. After sufficient water has been removed to allow the dispersed particles to dry to contact, they are separated from the residual liquid by filtration, after which they can be dried in a conventional manner. Their particle size is between 100 and 1000 μm.

The resulting beads do not dust, so they can be handled safely. When the washing powder containing them is mixed with water, they dissolve rapidly, releasing the enzyme into the water.

Example 2

Prepare a solution of 640 g of 25% sodium polyacrylate and 160 g of a 5% detergent protease solution concentrated in the fermentation broth (i.e. 8 g of dry enzyme and 160 g of dry polymer) and adjust its pH to 7. 1600 g of a water-insoluble aliphatic hydrocarbon liquid (Solvent 41) and 53 g of an inorganic solution of amphipathic polymer stabilizer are placed in a 3-liter resin kettle with a mechanical stirrer and a Dean & Stark apparatus connected to a condenser, and the aqueous phase is added and the mixture is stirred for 5 minutes. The contents are then heated to 45 ° C, and the solution and water are azeotroped by reducing the pressure sufficiently for distillation to occur. The amount of water removed was monitored and distillation was continued until no more water was recovered (at least 2 hours).

The contents of the flask were cooled, the beads filtered, washed with acetone and dried with hot air.

The final product had a moisture content of 12-15%, in the form of regular, almost spherical beads that were hard and free-flowing and easily soluble in cold and hot water. The size range of the beads was narrow to about 250-500 pm and the product was essentially dust free. The beads were insoluble and non-swellable in tap water, but soluble in water at pH 9.

Example 3

The procedure of Example 2 was repeated with the exception that 5% (based on dry polymer and enzyme) titanium dioxide was added to give almost white and opaque beads.

Example 4

The procedure of Example 2 was repeated with the exception that the aqueous phase was formed from 160 g dry weight sodium polyacrylate, 160 g dry weight sucrose and water to a final weight of 800 g. The active protein content of the beads was about 3% and their properties were the same as shown in Example 2. White beads were obtained when 16 g of sucrose was replaced by 16 g of titanium dioxide.

Example 5

The procedure of Example 2 was repeated with the exception that sodium polyacrylate was replaced with the same amount of ammonium polymethacrylate. In the final beads, the matrix consists of a mixture of polymethacrylic acid and ammonium methacrylate, with the bulk of the outer shell of the polymer being free acid. The moisture permeability of the beads is lower than in Example 2, but they dissolve rapidly when mixed with a weakly basic solution.

Example 6

The procedure of Example 2 was repeated with the exception that the 25% sodium polyacrylate solution was replaced with a 25% methacrylic acid / butyl acrylate copolymer emulsion at pH 4.

Pearls are essential! insoluble and non-swellable in tap water, but rapidly soluble in alkaline conditions. By appropriately selecting the proportions of methacrylic acid and butyl acrylate, it is possible to select the pH at which the release takes place.

Example 7

The procedure of Example 2 was repeated with the exception that a small amount of water-oil emulsifier (5 g of sorbitan monooleate) is added to the aqueous phase and the dispersion is formed using high shear. The azeotropic distilled product is a stable dispersion in a water-immiscible liquid and has a particle size of less than 3 μm.