US 3746621 A
Description (OCR text may contain errors)
July 17, 1973 ASAJII KONDQ ETAL 3,746,621
PREPARATION OF ENZYME-CONTAINING Mxcnocmsum;
Filed June 24, 1969 United States Patent 3,746,621 PREPARATION OF ENZYME-CONTAINING MICROCAPSULE Asaji Kondo, Masao Kitajima, and Shizuo Miyano, Asakishi, Japan, assignors to Fuji Photo Film Co., Ltd., Kanagawa, Japan Filed June 24, 1969, Ser. No. 836,066 Claims priority, application Japan, June 25, 1968, 43/ 44,099 Int. Cl. C07g 7/02 US. Cl. 195-63 11 Claims ABSTRACT OF THE DISCLOSURE A method for making enzyme-containing microcapsules and the resulting product including forming a dispersion of an enzyme, a binder, a solvent for the binder, and a swellable solid which is insoluble in said solvent, and spray drying the dispersion at a temperature below that which the enzyme undergoes denaturation.
BACKGROUND OF THE INVENTION (1) Field of the invention (2) Description of the prior art There are a variety of commercially available enzymes, such as protease, lipase, carbohydrease and the like, that act on high molecular weight substrates, also enzymes, such as peroxidase, hydrase, amidase and the like, that act on low molecular weight substrates are available. These enzymes, and others are generally commercially available in the form of a dried powder. They are prepared, usually, from aqueous solutions of crude enzymes by addition of acetone, alcohols or the like as a precipitant.
The powdery enzymes, in most cases, are fairly quickly deactivated by the presence of moisture or contact by other substances. For instance, powdered lipase, when mixed with a detergent for cleaning use, often loses its activity due to the influence of the coexisting detergent. Furthermore, certain powdered enzymes agglomerate through absorption of moisture in air or partially agglomerate when put in water to form aqueous solutions. This makes it difficult to rapidly prepare an aqueous solution of the enzyme.
The enzyme-containing microcapsules of the present invention overcome such drawbacks immediately. That is to say, by micro-encapsulation, the enzyme is protected from moisture in the air as well as from contact with other substances, and the microcapsules do not agglomerate in air since they are in the form of spherical solid particles. When put in water, the microcapsule is expanded and broken down by the action of the swellable particles, contained therein, to form an aqueous enzyme solution without agglomeration.
BRIEF DESCRIPTION OF THE INVENTION In general, the enzyme-containing capsules of the present invention are produced by forming a dispersion of an enzyme, a binder material, a solvent for said binder,
and swellable particles which are insoluble in the solvent.
The binder may be either Water or organic compound soluble.
In one embodiment of the present invention the enzyme is dissolved or dispersed in a solution of the binder and solvent. The swellable particles are then dispersed in the mixture and the resulting dispersion is dried. However, when the enzyme and/or the swellable agent are hard to dissolve or disperse in the binder solution, they may be dispersed in a solvent prior to mixing in the binder solution. The solvent utilized under these circumstances may be the same or different from the binder solvent but must be one which will not deleteriously aifect the resulting dispersion and drying steps.
The microcapsules that are the product of the present invention vary in size according to the scale and type of spraying apparatus utilized. In general, the product size varies from a few to several thousand microns. The present invention, however, preferably contemplates atomizing so as to obtain particles of from about 10 to 2000 microns.
In the accompanying drawing, the figure is a diagrammatic cross-sectional view of an enzyme-containing microcapsule in accordance with the present invention, wherein tightly packed particles 1 of powdered enzyme and swellable particles 2 are enclosed by a binder substance 3.
As a binder solution used in the practice of the present invention, there are included solutions of methanol, acetone, or like organic solvents, of a waterand organic solvent-soluble material, such as ethylene-maleic anhyhydride copolymers, vinyl methyl ether-maleic anhydride copolymers or the like. Also, aqueous solutions of a water-soluble material, such as gelatin casein, dextrin, dextran, gum arabic, cellulose derivatives, polyvinyl alcohol (PVA), agar-agar, sodium alginate or the like, may be utilized. The conncentration of the solution may be varied from about 0.1% to about 20%, preferably 1 to 20% by weight depending on the viscosity. However, in order to attain quick breakdown in water, the binder termined by experimentation. Of course, the binder should should be used in as small an amount as possible, as debe such that it is unaffected by the enzyme incorporated therein. The binders which are preferred in the practice of the present invention, must keep the enzyme active, and include those which exhibit excellent affinity for water, and dissolve in organic solvents having low boiling points. Exemplary of such binders are vinyl methyl ethermaleic acid or anhydride copolymers (PVM/MA) gum arabic and dextrin.
The swellable particles are finely divided solids that do not react with the binder, do not deactivate the enzyme, are insoluble in the solvent for the binder, and undergo such physical changes as solution, swelling and breakdown upon contact with water. Examples are silica, clay, starch, powdered dextran, gelatin, cured gelatin, casein, and the like. Among these, silica and starch are easily obtainable and function well in the present invention. The swellable powder is preferably present in an amount of from 0.5 to 30 times the amount of binder present by weight.
Methanolacetone PVM/MA PVA Starch S102 For spray drying there may be employed any of the commercially available spray dryers, for example, both centrifugal atomizer-type and spray nozzle-type dryers may be used. Since most enzymes undergo denaturation at temperatures above 60 C. the drying is advantageously carried out at room temperature or at a somewhat elevated temperature at which the inside of the capsule is maintained at a temperature that does not cause denaturation of enzyme. Exemplary drying temperatures are: organic solvent, inlet 80 C., outlet 60 C., and water, inlet 150 C., outlet 100 C.
The swellable powder utilized in the present invention is necessary in order to allow the capsule to dissolve quickly. When gelatin is utilized as the swellable material, it is usually dispersed into a PVM/MA-acetone solution. However, when dextrin is used as a binder, an aqueous solution is formed, but when used as the swellable agent, the dextrin is dispersed in an organic solvent, Also, since casein is an alkali soluble, it may be used as a binder in weak alkali solutions, but in other cases operates as the swellable powder.
EXAMPLE I A binder solution prepared by dissolving 20 g. of an ethylene-maleic anhydride copolymer in 100 m1. of a 1:1 mixture of methanol and acetone was mixed with a liquid dispersion prepared by dispersing 100 g. of powdered lipase and 80 g. of powdered dextran in '800 ml. of acetone to form a spraying liquid dispersion. The dispersion was sprayed through a nozzle having a diameter of 1.3 mm. under a pressure of 1 kg./cm. gauge into a dryer chamber of a diameter of 1 m. and a depth of 2 m. while passing therethrough 1.3 cubic meters per minute of hot air. The air temperature at inlet was 70 C. and at outlet was 40 C. Thus, there was obtained 130 g. of lipase-containing capsules of particle sizes of from 20 microns to 100 microns. The lipase-containing capsule exhibited a rate of solution substantially equal to that of the powdered lipase before encapsulization. The capsule was stored in mixture with a commercially available granulated detergent for 3 months without any decrease in the activity of lipase being observed.
EXAMPLE II The procedure of Example I was used but the milk coagulating enzyme rennet was used in place of lipase. The rennet-containing capsule thus obtained quickly dissolved in water or milk without any agglomeration.
EXAMPLE III An aqueous binder solution prepared by dissolving 20 g. of dextrin in 300 ml. of water was mixed with a liquid dispersion prepared by dispersing 200 g. of fine silica and 20 g. of lipase in 350 ml. of acetone. The liquid dispersion, thus formed, was subjected to microencapsulation by means of a Minor Unit Spray Dryer. The dryer was operated at a speed of 20,000 r.p.m., a
temperature, at inlet of C., temperature, at outlet, of 60 C., and with an air stream of 1 cubic meter per minute. The dropping rate of the dispersion was 500 ml./ hr. Thus, there were obtained 100 g. of lipase-containing capsules having particle sizes of from 20 microns to 50 microns.
' 1. An enzyme-containing microcapsule comprising an enzyme and particles of a finely divided swellable solid encapsulated in a binder substance, which is unafiected by the enzyme said swellable solid being inert with respect to the binder substance, and said swellable solid being present in an amount of from 0.5 to 30 times the amount of binder present by weight.
2. The enzyme-containing microcapsule of claim 1, wherein said binder is a member selected from the group consisting of ethylene-maleic anhydride copolymers, vinylmethyl ether maleic anhydride copolymers, gelatin, casein, dextrin, dextran, gum arabic, cellulose derivatives, polyvinyl alcohol, agar-agar, and sodium alginate.
3. The enzyme-containing microcapsule of claim 1, wherein said swellable solid is a member selected from the group consisting of silica, clay, starch, powdered dextran, gelatin, cured gelatin and casein.
4. A method of producing enzyme-containing microcapsules comprising forming a liquid dispersion of an enzyme, a binder, a solvent for said binder, and a finely divided swellable solid, inert with respect to said binder, which is insoluble in said solvent, and spray drying said dispersion at a temperature below that which the enzyme undergoes denaturation, said binder being present in an amount of from 0.1 to 20.0% by weight based on the dispersion, said binder being unaffected by the enzyme.
5. The method of claim 4, wherein said binder is a member selected from the group consisting of ethylenemaleic anhydride copolymers, vinylmethyl ether maleic anhydride copolymers, gelatin, casein, dextrin, dextran, gum arabic, cellulose derivatives, polyvinyl alcohol, agaragar, and sodium alginate.
6. The method of claim 4, wherein said swellable solid is a member selected from the group consisting of silica, clay, starch, powdered dextran, gelatin, cured gelatin, and casein.
7. The method of claim 4, wherein said binder is present in an amount of from 1.0 to 20.0% by weight.
8. The method of claim 4, wherein said swellable solid is present in an amount of from 0.5 to 30 times the amount of binder present by weight.
9. The method of claim 4, wherein said dispersion is formed by dissolving or dispersing said enzyme in a solution of said binder and said solvent, and dispersing therein particles of said swellable solid.
10. The method of claim 4, wherein said enzyme is dissolved in a portion of said solvent prior to being dispersed or dissolved in a solution of said binder and solvent.
11. The method of claim 4, wherein said enzyme and said swellable solid are dissolved in a solvent therefor prior to forming the dispersion with a solution of said binder and solvent.
References Cited UNITED STATES PATENTS 2,642,376 6/195'3 Gale et al. -63 3,091,567 5/1963 Wurzburg et a1. 424-35 3,181,998 5/1965 Kanig 195--63 X 3,455,838 7/1969 Marotta et a1 252-316 A. LOUIS MONACE'LL, Primary Examiner D. M. NA'FF, Assistant Examiner US. Cl. X.R. 195-68