METHOD FOR PRODUCTION OF AN ENZYME GRANULATE

Abstract: Cellulose fibres or artificial fibres, binder, an enzyme as a solution or a suspension, filler and liquid granulating aid are introduced into a granulator, the oversized particles are moderately ground, recirculation is performed, and if necessary a drying is performed. The physical strength of the granulate is improved, and it is easy to obtain the granulate in a narrow particle size distribution.

Description: This invention relates to a method for production of an enzyme granulate. The method according to the invention is a further development of the method described in Example XVII or colomn 3, lines 28-30 in US 4,106,991. This method is especially advantageous, because it opens op the possibility of using a liquid enzyme preparation, e.g. an ultrafiltrate, which can be added directly to the granulating drum, without the necessity of having to isolate the enzyme from the fermentation broth as part of a solid composition. Even if the known method for production of granulates possesses many advantageous characteristics the obtainable narrowness of particle size distribution, the obtainable physical strength of the granulate, and the obtainable maximum enzymatic activity of the granulate is open to improvement. Thus the process according to the invention for production of an enzyme granulate comprises the introduction into a granulator of from 1.5 to 40% by weight of cellulose fibres or artificial fibres, from 0 to 15% of a binder, enzyme in the form of solution or suspension of the enzyme and filler in an amount which generates the intended enzyme activity in the finished granulate, a fluid granulating agent consisting of a waxy substance and/or water, in an amount in the range of from 0 to 40% by weight, all percentages referring to the total amount of dry substances, the sequence of the introduction of the different material being arbitrary, except that at least the major part of the granulating agent is introduced after at least a substantial part of the dry substances is introduced in the granulator, whereafter the part of the granulate with particle sizes outside the wanted interval is recirculated with no crushing of the undersized particles and with crushing of the oversized particles in such manner that the overall recycle particle size distribution, depicted as a cumulative particle size distribution, is of the same general shape as the particle size distribution of the granulate, depicted similarly, but displaced to the left, whereafter the granulate if necessary is dried. Usually and preferably the enzyme in the form of a solution or suspension of the enzyme is a concentrated aqueous solution or suspension of the enzyme derived from the fermentation broth. However, in special cases, where it is desired to avoid water, the water can be eliminated, e.g. by vacuum evaporation, and substituted by a waxy substance of the same kind as that which is used as a fluid granulating agent. Reference is made to figures 1 and 2 in order to show what is meant by the expression "the same general shape". The prior art process comprises a recirculation of the nature described on column 6, lines 1-5 in US 4,106,991. When it is indicated that about 20% of the oversized and undersized granules are recirculated, any skilled worker in the art should understand, that both the oversized and the undersized granulates are crushed to a fine powder before recirculation. The recirculation according to the invention, however, differs radically from this conventional recirculation, both in regard to the oversized particels and in regard to the undersized particles. According to the invention the oversized particles are crushed only to a certain degree, as explained previously in this specification, whereas they are crushed to a fine powder (below around 100 µm) according to the prior art method, and the undersized particles are not crushed at all according to the invention, whereas they are crushed to a fine powder (below around 100 µm) according to the prior art method. Most surprisingly, this changed recirculation scheme exerts a strong influence on the characteristics of the enzyme granulates, as the enzyme granulate produced by means of the method according to the invention both possesses a much narrower particle size distribution and a much better physical strength. Also, it has been found that the particle size distribution can be controlled much easier by means of the method according to the invention. The recirculation indicated above refers primarily to the particles with "wrong" particle size. However, also particles with "right" particle size may be recirculated, if appropriate. The method according to the invention can be performed both batchwise and continuously. The cellulose in fibrous form can be sawdust, pure fibrous cellulose, cotton, or other forms of pure or impure fibrous cellulose. Several brands of cellulose in fibrous form are on the market, e.g. CEPO and ARBOCEL. In a publication from Svenska Tramjolsfabrikerna AB, "Cepo Cellulose Powder" it is stated that for Cepo S/20 cellulose the approximate maximum fibre length is 500 µ, the approximate average fibre length is 160 µ, the approximate maximum fibre width is 50 µ and the approximate average fibre width is 30 µ. Also it is stated that CEPO SS/200 cellulose has an approximate maximum fibre length of 150 µ, an approximate average fibre length of 50 µ, an approximate maximum fibre width of 45 µ and an approximate average fibre width of 25 µ. Cellulose fibres with these dimensions are very well suited for the purpose of the inven-tion. Typical artificial fibres are made of polyethylene, polypropylene, polyester, especially Nylon, polyvinylformal, and poly(meth)acrylic compounds. The binders used in the process according to the invention are the binders conventionally used in the field of granulation with a high melting point or with no melting point at all and of a non waxy nature, e.g. polyvinyl pyrrolidone, dextrins, polyvinylalcohol, and cellulose derivatives, including for example hydroxypropyl cellulose, methyl cellulose or CMC. The binders can be added in the solid state or in liquid form, as appropriate to the binder. A granulate cannot be formed on the basis of cellulose, enzyme filler and a binder, as above defined, without the use of a granulating agent, as defined below. All enzymes can be granulated by means of the process according to the present invention. Preferably, proteinases, amylases, lipases and cellulases are granulated according to the invention. Specific examples are ALCALASE® (a Bacillus licheniformis proteinase), ESPERASE® and SAVINASE® (microbial alcaline proteinases produced according to the British Pat. No. 1,243,784) and TERMAMYL® (a Bacillus licheniformis amylase). The enzyme is introduced into the granulator as a solution, for example a concentrated enzyme solution prepared by ultrafiltration, reverse osmosis or evaporation. The filler is used only for the purpose of adjusting to the intended enzyme activity in the finished granulate. Since the enzyme introduced into the granulator already contains diluent impurities which are considered as fillers additional filler is not always needed to standardize the enzymatic activity of the granulate. If a filler is used, it is usually organic or inorganic salts, which may be soluble or insoluble in water, e.g. Na₂SO₄, NaCl, CaCO₃, or minerals, silicates, e.g. kaolin or bentonite, but other indifferent fillers which do not interfere with the granulating process and later use of the product can be used. The granulating agent is water and/or a waxy substance. The granulating agent is always used as a liquid phase in the granulation process; the waxy substance if present therefore is either dissolved or dispersed in the water or melted. By a waxy substance is understood a substance which possesses all of the following characteristics: (1) the melting point is between 30° and 100°C, preferably between 40° and 80°C, (2) the substance is of a tough and not brittle nature, and (3) the substance possesses substantial plasticity at room temperature. Both water and waxy substance are granulating agents, i.e. they are both active during the formation of the granules, the waxy substance stays as a constituent in the finished granules, whereas the majority of the water is removed during the drying. Thus in order to refer all amounts to the finished, dry granules all percentages are calculated on the basis of total dry substances, which means that water, one of the granulating agents, is not added to the other constituents when calculating the percentage of water, whereas the waxy substance, the other granulating agent, has to be added to the other dry constituents when calculating the percentage of waxy substance. Examples of waxy substances are polyglycols, fatty alcohols, ethoxylated fatty alcohols, higher fatty acids, mono-, di- and triglycerolesters of higher fatty acids, e.g. glycerol monostearate, alkylarylethoxylates, and coconut monoethanolamide. If a high amount of waxy substance is used, relatively little water should be added, and vice versa. Thus the granulating agent can be either water alone, waxy substance alone or a mixture of water and waxy substance. In case a mixture of water and waxy substance is used, the water and the waxy substance can be added in any sequence, e.g. first the water and then the waxy substance, or first the waxy substance and then the water or a solution or suspension of the waxy substance in the water. Also, in case a mixture of water and waxy substance is used, the waxy substance can be soluble or insoluble (but dispersable) in water. If no water is used in the granulating agent, and the solution or suspension of enzyme is on a non-aqueous basis, usually no drying is needed. In this case the granulating agent is a melted waxy material, and only cooling is needed to solidify the particles. In most cases, however, some drying is performed, and the drying is usually carried out as a fluid bed drying whereby small amounts of dust and small granules are blown away from the surface of the granules. However, any kind of drying can be used. In the instance where no water is used as a granulating agent, and the solution or suspension of enzyme is on a non-aqueous basis, a flow conditioner or anticaking agent may be added to the granulate either before or after the cooling step, e.g. fumed silica, for instance the commercial products AEROSIL or CAB-O-SIL. The relative amount of fluid enzyme and fluid granulating agent is decisive for the particle sizes of the finished enzyme granulate: the higher the relative amount of fluid is, the bigger the particle sizes will be. The higher the relative amount of added cellulose is, the more fluid can be absorbed. The skilled worker will know when to dry during the process and to what extent. The granulator can be any of the known types of mixing granulators, drum granulators, pan granulators or modifications of these. If a mixing granulator is used, for example a mixing drum from the German Company Gebr. Lödige Maschinen G.m.b.H, 479 Paderborn, Elsenerstrasse 7-9, DT, it is preferred that small rotating knives are mounted in the granulator in order to compact the granules. Furthermore, facultative additives as coloring agents, pigments, disintegrants, or enzyme stabilizers, e.g. antioxidants, may be added. An especially important facultative additive is a water absorbant agent, e.g. Bentonite or diatomaceous earth, which opens up the possibility for the addition of more enzyme solution, and thus the obtainment of a product with a higher specific activity. In a preferred embodiment of the method according to the invention the cellulose fibres or the artificial fibres have an average fibre length of 50-2000 µm, preferably 100-1000 µm, and an average fibre width of 20-50 µm, preferably 25-50 µm. Hereby a satisfactory mechanical strength is obtained. In a preferred embodiment of the method according to the invention the amount of cellulose fibres or artificial fibres is between 4 and 20% by weight, based on the dry weight of the granulate. Below 4% by weight of fibres the fibre effect is somewhat impaired, and above 20% by weight of fibres production tends to be somewhat cumbersome and the price of the product increases somewhat. In a preferred embodiment of the method according to the invention the enzyme is a protease, an amylase, a lipase, a cellulase, or an oxidase. These are the most common enzymes in granulate form for industrial purposes. In a preferred embodiment of the method according to the invention the filler consists of or comprises inorganic salts. Hereby a relatively cheap granulate is obtained. In a preferred embodiment of the method according to the invention between 10 and 90% of the granulate is recirculated. At a recirculation below 10% it is difficult to obtain a satisfactory strength, and at a recirculation above 90% the process gets uneconomic due to loss of activity. In a preferred embodiment of the method according to the invention the granulation is performed at a temperature between 20 and 70°C. At a temperature below 20°C cooling will be necessary, and at a temperature above 70°C the stability of the enzyme will decrease. The invention will be illustrated by the following examples. The activity units used in the examples are defined as follows. enzyme activity unit Definition indicated in proteolytic KNPU AF 220/1-GB amylolytic KNU(T) AF 214/1 GB lipolytic LU AF 95/4-GB cellulolytic CMCU AF 187/3-GB On request these AF publications can be obtained from NOVO INDUSTRI A/S, Novo Allé, 2880 Bagsvaerd, Denmark. EXAMPLE 1 9.0 kg of a recycled granulate produced according to this example, and consisting of 1.5 kg of unground fines (< 300 µm) and 7.5 kg of product fraction (300-710 µm) is introduced into a Lödige mixer FM 50 with 12.5 kg of fibrous cellulose, Arbocel BC 200 0.4 kg of TiO₂, and 7.0 kg of ground Na₂SO₄ The mixed dry components are sprayed with 4.8 kg of fluid Savinase concentrate (25 KNPU/g), produced by ultrafiltration and evaporation. The viscosity of the concentrate at 18°C is 80 cP, measured with a Brookfield RVT viscosimeter, spindle 1, 50 rpm. During and after the spraying the moist mixture is exposed to a compacting and granulating influence from the multiple set of knives, as described in Example 1 of US patent No. 4,106,991. When the granulation is finished, the granulate is dried on a fluid bed, and the part thereof defined as product fraction (in this case 300-710 µm) is separated for quality testing. The undersize fraction, which is not treated, and the oversize fraction, which is crushed to a particle size distribution, depicted as a cumulative particle size distribution, which is of the same general shape as the particle size distribution of the product fraction, but displaced to the left, in a similar way as shown in fig. 1 and 2, are recirculated. EXAMPLE 2 This example is a comparison example corresponding to the US 4,106,991 prior art. 3.0 kg of fibrous cellulose, Arbocel BC 200 0.8 kg of TiO₂, and 14.8 kg of ground Na₂SO₄ is mixed in a Lödige mixer FM 50, and is sprayed with 6.3 kg of a Savinase ultrafiltrate, concentrated by evaporation, with an activity of 25 KNPU/g, followed by a granulation treatment, as described in Example 1. Subsequently the granulate is dried on a fluid bed. The following grain size distributions were obtained for the granulates obtained from Examples 1 and 2: Particle size distribution: Example 1 Example 2 > 1000 µm 2% 9% > 850 - 4% 16% > 710 - 15% 29% > 600 - 31% 45% > 500 - 53% 60% > 420 - 66% 73% > 355 - 79% 86% < 300 - 10% 8% < 250 - 4% 3% Mean diameter 510 µm 560 µm 300-710 µm fraction 81% 68% The above particle size distribution and the above mean diameter as well as all other particle size distributions and mean diameters indicated in this specification with claims is on a weight basis. The amount of dust and the physical strength are measured according to two different methods: A. Elutriation dust method, as described in NOVO publication AF 129/3-GB, available on request from NOVO INDUSTRI A/S. B. Novo attrition dust method, as described in NOVO publication AF 225/1-GB, available on request from NOVO INDUSTRI A/S. It appears from the following table that the values in regard to dust and physical strength of the granulate according to Example 1 is superior to the corresponding prior art values (Example 2). Method Example 1 (invention) Example 2 (prior art) total, mg active, µg (4 KNPU/g) total, mg active, µg (4 KNPU/g A 13.2 10700 89.7 81500 B 7.2 4200 56.0 43100 activity: 7.9 KNPU/g activity: 6.9 KNPU/g EXAMPLE 3 9.5 kg of a recycled granulate produced according to this example, and consisting of 1.6 kg of unground fines (< 300 µm) and 7.9 kg of product fraction (300-710 µm) is introduced into a Lödige mixer FM 50 with 1.43 kg of fibrous cellulose, Arbocel BC 200 0.38 kg of TiO₂, and 6.36 kg of ground Na₂SO₄ The mixed dry components are sprayed with 4.7 kg of Savinase ultrafiltrate, concentrated by evaporation, with an activity of 26 KNPU/g, and wherein 200 g of a carbohydrate binder is dissolved. The moist mixture is treated, granulated and dried as indicated in Example 1. EXAMPLE 4 This example is a comparison example corresponding to the US 4,106,991 prior art. 3.0 kg of fibrous cellulose, Arbocel BC 200 0.8 kg of TiO₂, and 13.8 kg of ground Na₂SO₄ is granulated and dried as described in Example 2, but with addition of 5.7 kg of a Savinase ultrafiltrate, concentrated by evaporation, with an activity of 26 KNPU/g, and wherein 400 g of a carbohydrate binder is dissolved. The following particle size distributions were obtained for the granulates produced according to Examples 3 and 4. Particle size distribution: Example 3 Example 4 > 1000 µm 2.7% 10% > 850 - 5.7% 20% > 710 - 17% 32% > 600 - 35% 49% > 500 - 56% 64% > 425 - 68% 76% > 355 - 77% 83% < 300 - 12% 10% < 250 - 5.8% 5.6% Mean diameter 520 µm 600 µm 300-710 µm fraction 71% 58% It appears from the following table that the values in regard to dust and physical strength of the granulate according to Example 3 are superior to the corresponding prior art values (Example 4). Method Example 1 (invention) Example 2 (prior art) total, mg active, µg (4 KNPU/g) total, mg active, µg (4 KNPU/g A 9.8 4100 109.5 30100 B 9.8 3500 150.5 52400 activity: 9.4 KNPU/g activity: 7.8 KNPU/g EXAMPLE 5 13.4 kg of a recycled granulate produced according to this example, and consisting of 2.6 kg of unground fines (< 300 µm), 8.1 kg of product fraction (300-710 µm), and 2.7 kg of moderately ground oversized fraction (originally > 710 µm is introduced into a Lödige mixer FM 50 with 1.0 kg of fibrous cellulose, Arbocel BC 200 0.26 kg of TiO₂, and 4.5 kg of ground Na₂SO₄ The mixed dry components are sprayed with 4.0 kg of fluid Savinase concentrate (24 KNPU/g), produced by ultrafiltration and evaporation. The moist mixture is treated, granulated and dried as indicated in Example 1. The following grain size distribution was obtained: Particle size distribution: 3.6% > 1000 µm 6.0% > 850 - 14.0% > 710 - 28.0% > 600 - 49.0% > 500 - 67.0% > 425 - 81.0% > 355 - 6.0% < 300 - 2.3% < 250 - Mean diameter: 495 µm 300-710 µm fraction 80% The values for the amount of dust and physical strength of the 300-710 µm fraction of the granulate appear from the following table. Method total, mg active, µg (4 KNPU/g) A 1.3 650 B 3.0 2330 activity: 9.7 KNPU/g Reference is made to fig. 1. EXAMPLE 6 10.0 kg of a recycled granulate produced according to this example, and consisting of 2.0 kg of unground fines (< 300 µm), and 4.0 kg of product fraction (300-710 µm), and 4.0 kg of moderately ground oversized particles (originally > 710 µm) is introduced into a Lödige mixer FM 50 with 1.5 kg of fibrous cellulose, Arbocel BC 200 1.0 kg of Perlite BF 0.4 kg of TiO₂, and 5.46 kg of ground Na₂SO₄ The mixed, dry components are sprayed with 5.3 kg of fluid Savinase concentrate (13 KNPU/g), produced by ultrafiltration and evaporation. The moist mixture is treated, granulated and dried as indicated in Example 1. The following grain size distribution was obtained: Particle size distribution: 1.7% > 1000 µm 4.5% > 850 - 18.0% > 710 - 32.0% > 600 - 49.0% > 500 - 65.0% > 425 - 77.0% > 355 - 6.0% < 300 - 1.7% < 250 - Mean diameter: 495 µm 300-710 µm fraction 76% The values for the amount of dust and physical strength of the 300-710 µm fraction of the granulate appear from the following table. Method total, mg active, µg (4 KNPU/g) A 11.2 2300 B 8.9 3900 activity: 8.3 KNPU/g Reference is made to fig. 2. EXAMPLE 7 10.0 kg of a recycled granulate produced according to this example and consisting of 2.5 kg of unground fines (< 425 µm), 5.0 kg of product fraction (425-630 µm) and 2.5 kg of moderately ground oversized fraction (originally > 630 µm) is introduced into a Lödige mixer FM 50 with 1.5 kg of fibrous cellulose, Arbocel BC 200 1.0 kg of Clarcel CBL-3 diatomaceous earth 0.4 kg of TiO₂, and 5.4 kg of ground Na₂SO₄ The mixed dry components are sprayed with 4.8 kg of a Savinase ultrafiltrate, concentrated by evaporation, with an activity of 19 KNPU/g. The moist mixture is treated, granulated and dried as indicated in Example 1. EXAMPLE 8 This example is a comparison example corresponding to the US 4,106,991 prior art. 3.0 kg of fibrous cellulose, Arbocel BC 200 0.8 kg of TiO₂, 2.0 kg of Clarcel CBL-2 diatomaceous earth, and 14.4 kg of ground Na₂SO₄ is granulated with 6.6 kg of ultrafiltered Savinase concentrate, concentrated by evaporation and with an activity of 17 KNPU/g, and dried as described in Example 2. The following particle size distributions were obtained for the granulates obtained from Examples 7 and 8: Particle size distribution: Example 7 Example 8 > 1000 µm 5% 18% > 850 - 11% 27% > 710 - 30% 39% > 600 - 49% 52% > 500 - 66% 66% > 425 - 77% 76% > 355 - 85% 84% < 300 - 6.0% 8% < 250 - 2.2% 3.5% Mean diameter 590 µm 610 µm It appears from the following table that the values in regard to dust and physical strength of the granulate according to Example 7 are superior to the corresponding prior art values (Example 8). Method Example 7 (invention) Example 8 (prior art) total, mg active, µg (4 KNPU/g) total, mg active, µg (4 KNPU/g A 2.0 1090 95.6 25200 B 1.3 650 28.6 11600 activity: 8.2 KNPU/g activity: 5.2 KNPU/g EXAMPLE 9 10.0 kg of a recycled granulate produced according to this example, and consisting of 1.0 kg of unground fines (< 300 µm) and 9.0 kg of product fraction (300-900 µm) is introduced into a Lödige mixer FM 50 with 1.5 kg of fibrous cellulose, Arbocel BC 200 1.0 kg of Perlite BF 0.4 kg of TiO₂, and 4.7 kg of ground Na₂SO₄ The mixed dry components are sprayed with 5.5 kg of a Humicola insolens cellulase ultrafiltrate, concentrated by evaporation, with an activity of 4630 CMCU/g and a viscosity of 117 cP at 19.5°C, and to which 0.5 kg of carbohydrate binder is admixed. The starting material for the fluid cellulase concentrate is produced as indicated in US patent No. 4,435,307. The moist mixture is treated, granulated and dried as indicated in Example 1. The following particle size distribution was obtained: Particle size distribution: 4.5% > 1000 µm 16% > 850 - 34% > 710 - 52% > 600 - 70% > 500 - 81% > 425 - 89% > 355 - 2.2% < 300 - 0.8% < 250 - Mean diameter: 615 µm 300-900 µm fraction 87% The values for the amount of dust and physical strength of the granulate appear from the following table. Method total, mg active, µg (2400 CMCU/g) A 10.6 1600 B 2.5 760 activity: 2600 CMCU/g EXAMPLE 10 20 kg of a recycled granulate produced according to this example, and consisting of 7 kg of unground fines (< 300 µm) and 13 kg of product fraction (300-900 µm) is introduced into a Lödige mixer FM 130 together with 3.0 kg of fibrous cellulose, Diacel 200 2.1 kg of carbohydrate binder 13.6 kg of ground Na₂SO₄ A fluid lipase concentrate with an activity of 496.000 LU/g and a viscosity of 200 cP at 21°C was produced by fermentation according to Danish patent application no. 4499/87 followed by concentration by ultrafiltration and evaporation. The mixed dry components indicated above were sprayed with 8.0 kg of the fluid lipase concentrate indicated above. The thus produced, moist mixture is treated, granulated and dried as described in Example 1. The following particle size distribution was obtained: 4.1% > 1180 µm 9.1% > 1000 - 18.9% > 850 - 31.7% > 710 - 43.1% > 600 - 57.3% > 500 - 67.2% > 425 - 75.6% > 355 - 88.3% > 300 - 4.6% < 250 - Mean diameter: 550 µm Product properties: Activity: 155.000 LU/g Dust properties (300-900 µm fraction): Total Active/µg of 155.000 LU/g Method: A: 15.5 mg 650 µg B: 7.1 - 1340 - EXAMPLE 11 5 kg of a Termamyl granulate produced according to this example is used as the recirculation material. These 5 kg of Termamyl granulate consist of fines (< 300 µm), product fraction (300-900 µm) and ground oversize fraction. The recirulation material is introduced into a Lödige mixer type FM 130 together with the following granulation components: 3.0 kg of cellulose fibres 0.6 kg of titanium dioxide 2.1 kg of carbohydrate binder 18.3 kg of Na₂SO₄ A fluid Termamyl concentrate with an activity of 5500 KNU(T)/g and a dry matter content of approximately 30% was produced by fermentation according to US patent no. 3,912,590 and DK patent no. 123726, followed by concentrtion by ultrafiltration and evaporation. The mixed dry components indicated above were sprayed with 6.8 kg of the fluid Termamyl concentrate indicated above. The thus produced moist mixture is treated, granulated and dried as desribed in Example 1. The following particle size distribution was obtained: 9.0% > 1200 µm 14.8% > 1000 - 22.9% > 850 - 33.0% > 710 - 43.9% > 600 - 57.3% > 500 - 67.5% > 425 - 13.9% < 300 - Activity: 133.7 KNU(T)/g Water content: 0.7% Dust measurement: Method A: total mg 9.5 1950 µg Termamyl 60 KNU(T)/g Method B: total mg 7.3 1100 µg Termamyl 60 KNU(T)/g The features disclosed in the foregoing description, in the following claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.

Claims: A process for the production of an enzyme granulate, which process comprises introduction into a granulator of from 1.5 to 40% by weight of cellulose fibres or artificial fibres, from 0 to 15% of a binder, enzyme in the form of solution or suspension of the enzyme and filler in an amount which generates the intended enzyme activity in the finished granulate, a fluid granulating agent consisting of a waxy substance and/or water, in an amount in the range of from 0 to 40% by weight, all percentages referring to the total amount of dry substances, the sequence of the introduction of the different material being arbitrary, except that at least the major part of the granulating agent is introduced after at least a substantial part of the dry substances is introduced in the granulator, whereafter the part of the granulate with particle sizes outside the wanted interval is recirculated with no crushing of the undersized particles and with crushing of the oversized particles in such manner that the overall recycle particle size distribution, depicted as a cumulative particle size distribution, is of the same general shape as the particle size distribution of the granulate, depicted similarly, but displaced to the left, whereafter the granulate if necessary is dried. Method according to Claim 1, wherein the cellulose fibres or the artificial fibres have an average fibre length of 50-2000 µm, preferably 100-1000 µm, and an average fibre width of 20-50 µm, preferably 25-40 µm. Method according to Claims 1 - 2, wherein the amount of cellulose fibres or artificial fibres is between 4 and 20% by weight, based on the dry weight of the granulate. Method according to Claims 1 - 3, wherein the enzyme is a protease, an amylase, a lipase, a cellulase, or an oxidase. Method according to Claims 1 - 4, wherein the filler consists of or comprises inorganic salts. Method according to Claims 1 - 5, wherein between 10 and 90% of the granulate is recirculated. Method according to Claims 1 - 6, wherein the granulation is performed at a temperature between 20 and 70°C

Inventors: MARKUSSEN, ERIK KJAER
Applicants: NOVO NORDISK A/S
Application year: 1988
Main classification: C11D3
IPC codes: C11D3, C12N9