GB2249315A - A process for producing an aqueous solution of sodium hyaluronate - Google Patents
A process for producing an aqueous solution of sodium hyaluronate Download PDFInfo
- Publication number
- GB2249315A GB2249315A GB9122504A GB9122504A GB2249315A GB 2249315 A GB2249315 A GB 2249315A GB 9122504 A GB9122504 A GB 9122504A GB 9122504 A GB9122504 A GB 9122504A GB 2249315 A GB2249315 A GB 2249315A
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- Prior art keywords
- sodium hyaluronate
- solution
- ultrafiltration
- treated
- active carbon
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
- C08B37/0063—Glycosaminoglycans or mucopolysaccharides, e.g. keratan sulfate; Derivatives thereof, e.g. fucoidan
- C08B37/0072—Hyaluronic acid, i.e. HA or hyaluronan; Derivatives thereof, e.g. crosslinked hyaluronic acid (hylan) or hyaluronates
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P19/00—Preparation of compounds containing saccharide radicals
- C12P19/26—Preparation of nitrogen-containing carbohydrates
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- General Chemical & Material Sciences (AREA)
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- Polymers & Plastics (AREA)
- Preparation Of Compounds By Using Micro-Organisms (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
A process for producing an aqueous solution of sodium hyaluronate having high purity, which process comprises treating a fermentation broth of hyaluronic acid with active carbon in the presence of sodium chloride, optionally after having treated the broth by ultrafiltration, and then treating the active carbon-treated broth by ultrafiltration.
Description
1 2249315 A PROCESS FOR PRODUCING AN AQUEOUS SOTiUTION OF SODIUM
HYAWRONATE The present invention relates to a process for producing an aqueous solution of sodium hyaluronate having high purity from a fermentation broth of hyaluronic acid.
Hyaluronic acid is found as a constituent ingredient in connective tissues, vitreous humor, umbilical cords, cartilage, skinst rooster combs and the like, and it plays an important role in a living body. Sodium hyaluronate is a high-molecular substance. As its solution has high viscosity, elasticity and water-holding property, it is widely used in cosmetic materials. It is also used in medicines for ophthalmopathy, wounds and arthropathy. Sodium hyaluronate used for the above purposes is required to have high molecular weight and high purity. 20 Sodium hyaluronate is industrially produced by extracting from rooster combs, or by incubating microorganism having the ability to produce hyaluronic acid in a culture medium (a fermentation method). Hitherto, an aqueous solution of highly pure sodium hyaluronate has been produced by a process comprising treating a solution containing hyaluronic acid, which is obtained by extraction or fermentation, with a quaternary ammonium salt to obtain a precipitate, redissolving the precipitate in water, treating the solution with protease and with active carbon, adding alcohol to the treated solution to precipitate sodium hyaluronate, separating the precipitate from the alcohol solution, drying the precipitate to obtain a sodium hyaluronate powder, and redissolving the powder in water.
In such a process, it needs troublesome methods after 1 2 a culture medium is purified, a precipitating agent such as ethanol is added to the purified solution to precipitate sodium hyaluronate powder, and the powder is redissolved in water to obtain an aqueous solution of highly pure sodium hyaluronate.
An aqueous solution of highly pure sodium hyaluronate is not produced without precipitation process from a fermentation broth of hyaluronic acid by conventional methods.
An object of the present invention is to provide a process for directly producing an aqueous solution of highly pure sodium hyaluronate from a fermentation broth without using the above mentioned troublesome methods.
The present invention is characterized in that a fermentation broth of hyaluronic acid is treated with active carbont the treated solution is filtered. and the filtrate is treated by ultrafiltration to obtain an aqueous solution of highly pure sodium hyaluronate which can be used in cosmetic materials.
The term of %ighly pure" in the present invention has the following meaning. The purity of sodium hyaluronate is at least 85% by weight of freeze-dried material which is obtained by freeze-drying an aqueous solution of sodium hyaluronate, the evaporation residue of the solution is 100 to 130% by weight of sodium hyaluronate and protein in the solution is less than 0.1% by weight of sodium hyaluronate.
Sodium hyaluronate used in the present invention can be obtained from a culture medium in which a microorganism having the ability to produce hyaluronic acid is incubated in that culture medium. In the present invention, microorganisms which have the ability to produce hyaluronic acid can be used$ for example, Genus Strepto- coccus is preferred. Streptococcus pyogenesi Streptococ- 1 1 3 cus equi, Streptococcus equisimilisr Streptococcus dysgalactial and Streptococcus zooepidemicus are exemplified.
A culture medium used in the present invention can be a conventional culture medium which is used for incuba- tion of a hyaluronic acid producing microorganisms. As an example, a culture medium containing 2.0 to 3.0% of dextrose, 0.5% of yeast extract, 0.3% of potassium dihydrogen phosphate, 0.2% of dipotassium-phosphate, 0. 01% of sodium thiosulfate, 0.01% of magnesium sulfate 7H20, 0.002% of sodium sulfite, 0.001% of cobalt chloride, 0.001% of manganese chloride and 0.5% of an antifoamer can be used at pH 6.0 to 8.5 (in the solution, % means g/dl). The incubation is conducted by-shaking or aerating under aerobic conditions. The incubation temperature is 25 to 400C and preferably 30 to 35C. The pH value is controlled at 6.5 to 8.0 and preferably 7.0, after 1 to 3 days of the usual incubation periods, hyaluronic acid is accumulated in the culture medium. The culture medium is a mixture of culture residue ingredients, high-molecular ingredients, low-molecular ingredients, coloring matters, microorganisms and hyaluronic acid.
High-molecular ingredients excepting hyaluronic acid, coloring matters and a part of low-molecular ingredients are removed by active carbon adsorption. In particular, it is essential that protein of high-molecular ingredi- ents, by which an allergy reaction is caused, is thor oughly removed, The culture medium is treated with active carbon, and the active carbon and the microorganisms are removed by filtration.
The present inventors investigated conditions for adsorbing and removing the high-molecular ingredients, particularly protein by using active carbon. As a result, they found that the greater part of the protein could be adsorbed and removed by treating with active carbon in the presence of at least 0.2M of sodium chloride. The 4 relation between the concentration of sodium chloride in the treatment with active carbon and the protein content of the obtained sodium hyaluronate is shown in Table 1. Table 1 Concentration of sodium chloride in active carbon treatment (M) Protein content per sodium hyaluronate ( % by weight) 0 0.93 0.01 0.67 0.05 0.32 0.1 0.16 0.2 0.09 0.3 0.05 0.4 0.04 As shown in Table 1, it is necessary to treat with active carbon in the presence of at least 0.2Mi preferably 0.3 to 0.4M of sodium chloride. The filtrate which has been treated with active carbon can be subjected to ultrafiltration to remove the residual low molecular ingredients which are derived from the culture medium or produced in the fermentation process and sodium chloride which is added in the active carbon treatment.
Hyaluronic acid in the fermentation broth has commonly a molecular weight of at least 7 to 8 hundred thousands. On the other handi dextrose and mineral salts which are used as fermentation raw materials and a salt of organic acids which Is produced in the fermentation period have commonly a molecular weight of less than 5 thousands.
Accordingly. when the ultrafiltration treatment is conducted with an ultrafiltration membrane which is able 11 to cut compounds having a molecular weight of 6000 to 50000 or lessg the above mentioned low molecular ingredients can be removed. However, since low molecular ingredients cannot be removed satisfactorily by only one pass ultrafiltration operation, it is necessary to repeat the ultrafiltration operation by adding purified water intermittently or continuously. With the low molecular ingredients and sodium chloride are removed, the electric conductivity of the filtrate is lowered. Accordingly, the purification progress is judged by determination of the electric conductivity, For example, purified water is added to a filtrate obtained by active carbon treatment of the fermentation broth of hyaluronic acid. The mixture is subjected to ultrafiltration with Minitan (cut-off molecular weight: 30000) manufactured by Nihon Millipore Co. Ltd, and the relationships among the electric conductivity of the mixture, the purity of sodium hyaluronate and the amount of evaporated residue are shown in Table 2. The value of the electric conductivity changes with the concentration of sodium hyaluronate, so that the former is shown in a case of 0.2% by weight (at 250C) of the latter.
Table 2
Electric Purity 1 Evaporated conductivity residue2 (ms/cm) by weight) (% by weight) 20.0 6.0 17.5 5.8 17.8 6.6 3.6 36.7 3.2 0.50 79.8 1.50 0.37 89.1 1.25 0.20 91.3 1.11 6 1 Purity of sodium hyaluronate per freeze-dried material of sodium hyaluronate solution 2 Value calculated in terms of 1 % of sodium hyaluronate As a resulty to prepare a highly pure sodium hyaluronate solution# it is necessary to treat the solution by ultrafiltration until the value of the electric conductivity lowers to less than 0.4 mS/cm.
Further, in the process of the present invention.
after the solution is treated with active carbon and the active carbon is separated and removed from the solution. the ultrafiltration treatment is conducted. Otherwise,the solution can be treated by ultrafiltrationj active carbon treatment, separation and removal of the active carbon, and ultrafiltration. In this case. a liquid suited for the first ultrafiltration is a liquid obtained by filtra tion to remove microorganisms from the fermentation broth. Before the solution is treated with active carbon, the solution is treated by ultrafiltration. Accordingly, in comparison with a case in which the solution is not treated by ultrafiltration before the active carbon treatment, when the solution is treated by ultrafiltra tion before the active carbon treatmenti the same effect is obtained with a small amount of active carbon.
By using the present inventionr an aqueous solution of sodium hyaluronate having high purity can be prepared directly from a fermentation broth. Further. considering the use applicationt the solution can be finally concen trated with a filter or a concentrator by a conventional method.
By using the present inventionj an aqueous solution of sodium hyaluronate having high purity can be prepared directly from a fermentation broth without precipitation process. The method of the present invention provides a simple process without using conventional troublesome 7 methods. The cost of the process is li)wered. It becomes possible to obtain a highly pure product usable as cosmetic materialst medicinesi etc. .
The following examples illustrate the present invention more specifically, but these will not always be precise in practical applications. Example 1 300 ml of a fermentation broth bf hyaluronic acid was diluted three times with water, sodium- chloride was added to the solution to obtain a solution in concentration of 0.3M sodium chloride. 60g of active carbon (manufactured by Takeda Seiyaku Kogyo Co. Ltd, in Japan, trade name: Shirasagi A-50W, containing water of 50% by weight) was added to the solution, the solution was stirred for one hour and the active carbon was filtered off. The electric conductivity of the solution was 22.0 mS/cm. The filtrate was subjected to ultrafiltration with an ultrafiltration membrane (manufactured by Nihon Millipore Co. Ltd.# trade name: Minitan) having a cut-off molecular weight of 30000 by using purified water to obtain a treated solution having an electric conductivity of 0.24 mS/cm. The protein content of the treated solution was 0.06% by weight of sodium hyaluronate, the residue on evaporation was 115% by weight of sodium hyaluronate and the purity of sodium hyaluronate was 90.4% by weight of the freezedried material. A solution of sodium hyaluronate having high purity which was suited for cosmetics was obtained. Comparative Example 1 Using the same fermentation broth as used in Example 1, ultrafiltration was conducted except that active carbon was not added, and a filtrate having an electric conductivity of 0.30 mS/cm was obtained. The protein content of the treated solution was 2.74% by weight of sodium hyaluronate, the residue on evaporation was 125% 8 by weight of sodium hyaluronate and the purity of sodium hyaluronate was 85.5% by weight of the freeze-dried materials. Accordinglyi the removal of protein from the solution was incomplete. Comparative Example 2 Using the same fermentation broth as used in Example 1,, ultrafiltration was conducted except that sodium chloride was not added, and a filtrate having an electric conductivity of 0.20 mS/cm was obtained.
The protein content of the treated solution was 1.12% by weight of sodium hyaluronater the residue on evaporation was 120% by weight of sodium hyaluronate and the purity of sodium hyaluronate was 86. 3% by weight of the freeze-dried materials. Accordingly. the removal of protein from the solution was incomplete. Example 2 300 ml of a fermentation broth of hyaluronic acid was diluted three times with water, sodium chloride was added to the solution to obtain a solution in concentration of 0.4M sodium chloride. The electric conductivity of the solution was 28.3 mS/cm. After filtration for removing microorganisms from the solution. the filtrate was subjected to ultrafiltration with an ultrafiltration membrane having a cut-off molecular weight of 6000 (manufactured by Asahi Kasei Co. Ltd. in Japan. ultrafiltration module: SIP-1013) by using purified water to obtain a treated solution having an electric conductivity of 0.38 mS/cm. Sodium chloride was added to the treated solution to obtain a solution of 0.4M sodium chloride. 30g of active carbon (manufactured by Hutamura Kagaku Co. Ltd. in Japan# trade name: Taiko S, water content: 50% by weight) was added to the solutiont the solution was stirred for one hour and the active carbon was filtered off.
The filtrate obtained by the filtration of the active 1; Q 9 carbon was subjected to ultrafiltration with the same ultrafiltration membrane as mentioned above by adding purified water. and a filtrate having an electric conduc tivity of 0.2 mS/cm was obtained.
The protein content of the treated 0.2% aqueous solution of sodium hyaluronate was 0.04% by weight of sodium hyaluronatel the residue on evaporation was 114% by weight of sodium hyaluronate and the purity of sodium hyaluronate was 92.2% by weight of the freeze-dried material. The 0.2% aqueous solution was subjected to ultrafiltration with the same ultrafiltration membrane, and a 1% aqueous solution of sodium hyaluronate was easily prepared. Comparative Example 3 Using the same fermentation broth as used in Example 2. ultrafiltration was conducted except that the second ultrafiltration treatment was stopped when the electric conductivity of the filtrate became 3.6 mS/cm. The protein content of the obtained 0.2% aqueous solution of sodium hyaluronate was 0.09% by weight of sodium hyaluronatei the residue on evaporation was as 320% by weight of sodium hyaluronate and the purity of sodium hyaluronate was 36.7% by weight of the freezedried material. Accordinglyi the residue on evaporation remained in quantity and the purity of the sodium hyaluronate obtained was low.
Claims (6)
1. A process for producing an aqueous solution of sodium hyaluronate having high purity, which process comprises treating a fermentation broth of hyaluronic acid with active carbon, optionally after having treated the broth by ultrafiltration, the active carbon-treated broth by ultrafiltration.
2. A process as claimed in claim 1, wherein the active carbon treatment is conducted using a sodium chloride concentration of 0.2 M or more.
3. A process as claimed in claim 1, wherein the ultrafiltration treatment is conducted with an ultrafiltration membrane whose cut-off molecular weight is under hundred thousand, the treated solution being dialyzed to obtain a solution having an electrical conductivity of less than 0.4 mS/cm, and the solution is then concentrated.
4. A process as claimed in claim 1, wherein the purity of sodium hyaluronate is such that it comprises at least 85% by weight of the freeze-dried material obtained by freeze-drying an aqueous solution of sodium hyaluronate, the evaporation residue of the treated solution Y -1 11 comprises 100 to 130% by weight of sodium hyaluronate and the protein in the treated solution is less than 0.1% by weight of sodium hyaluronate.
5. A process as claimed in claim 1 in which the aqueous solution of sodium hyaluronate contains 1g of sodium hyaluronate per dl of solution.
6. A process as claimed in claim 1 substantially as hereinbefore described with reference to the Examples.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2283394A JPH0630605B2 (en) | 1990-10-23 | 1990-10-23 | Method for producing sodium hyaluronate aqueous solution |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9122504D0 GB9122504D0 (en) | 1991-12-04 |
| GB2249315A true GB2249315A (en) | 1992-05-06 |
| GB2249315B GB2249315B (en) | 1993-05-26 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9122504A Expired - Fee Related GB2249315B (en) | 1990-10-23 | 1991-10-23 | A process for producing an aqueous solution of sodium hyaluronate |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH0630605B2 (en) |
| DE (1) | DE4134854A1 (en) |
| GB (1) | GB2249315B (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001087468A1 (en) * | 2000-05-18 | 2001-11-22 | Novozymes A/S | Microfiltration using activated carbon |
| US6455304B1 (en) | 1994-07-01 | 2002-09-24 | The Board Of Regents Of The University Of Oklahoma | Hyaluronate synthase gene and uses thereof |
| US6833264B1 (en) | 1997-10-31 | 2004-12-21 | The Board Of Regents Of The University Of Oklahoma | Hyaluronan synthase gene and uses therof |
| US6951743B2 (en) | 1997-10-31 | 2005-10-04 | University Of Oklahoma Board Of Regents | Hyaluronan synthase genes and expression thereof in bacillus hosts |
| US6987023B2 (en) | 1998-04-02 | 2006-01-17 | The Board Of Regents Of The University Of Oklahoma | DNA encoding hyaluronan synthase from Pasteurella multocida and methods of use |
| US7029880B2 (en) | 1997-07-23 | 2006-04-18 | The Board Of Regents Of The University Of Oklahoma | Streptococcus equisimilis hyaluronan synthase gene and expression thereof in Bacillus subtilis |
| US7091008B1 (en) | 1994-07-01 | 2006-08-15 | The Board Of Regents Of The University Of Oklahoma | Hyaluronan synthase genes and expression thereof in Bacillus hosts |
| US7094581B2 (en) | 1998-10-26 | 2006-08-22 | The Board Of Regents Of The University Of Oklahoma | Hyaluronan synthases and methods of making and using same |
| US7223571B2 (en) | 1998-04-02 | 2007-05-29 | The Board Of Regents Of The Universtiy Of Oklahoma | Targeted glycosaminoglycan polymers by polymer grafting and methods of making and using same |
| WO2009063291A1 (en) * | 2007-11-13 | 2009-05-22 | Bio-Technology General (Israel) Ltd. | Dilute filtration sterilization process for viscoelastic biopolymers |
| US7741091B2 (en) | 1998-04-02 | 2010-06-22 | The Board Of Regents Of The University Of Oklahoma | Methods of producing hyaluronic acid and chimeric and hybrid glycosaminoglycan polymers |
| US8367818B2 (en) | 2006-02-24 | 2013-02-05 | Q.P. Corporation | Low molecular weight hyaluronic acid and/or salt thereof, and cosmetic preparation, pharmaceutical composition, and food composition each using same |
| CN102174122B (en) * | 2005-03-22 | 2013-08-07 | 丘比株式会社 | Low molecular weight hyaluronic acid and/or salt thereof, method for producing same, and cosmetic preparation and food composition containing same |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100312638B1 (en) * | 1994-09-09 | 2001-12-28 | 손 경 식 | Method for manufacturing high purity hyaluronic acid |
| JP2006104461A (en) * | 2004-09-10 | 2006-04-20 | Seikagaku Kogyo Co Ltd | Method for removing impurity in glycosaminoglycan fraction |
| JP4679138B2 (en) * | 2004-12-24 | 2011-04-27 | 株式会社日本バリアフリー | Method for producing highly purified mucopolysaccharide |
| JPWO2007069621A1 (en) * | 2005-12-14 | 2009-05-21 | 東京化成工業株式会社 | NOVEL COMPOSITION AND METHOD FOR PRODUCING THE SAME |
| JPWO2008004530A1 (en) * | 2006-07-03 | 2009-12-03 | 協和発酵バイオ株式会社 | Hyaluronic acid or its salt powder and method for producing the same |
| JP5372397B2 (en) * | 2008-03-31 | 2013-12-18 | エムアールシーポリサッカライド株式会社 | Method for producing hyaluronic acid and salts thereof |
| KR101132114B1 (en) * | 2009-09-15 | 2012-04-05 | 일동제약주식회사 | Method of molecular weight control of hyaluronic acid |
| CN102812050B (en) * | 2010-03-17 | 2016-01-20 | 电气化学工业株式会社 | The method of purification of hyaluronic acid and/or its salt |
| JP2011195611A (en) * | 2010-03-17 | 2011-10-06 | Denki Kagaku Kogyo Kk | Purification method for hyaluronic acid and/or salt thereof |
| JP5603925B2 (en) * | 2010-03-17 | 2014-10-08 | 電気化学工業株式会社 | Method for dissolving hyaluronic acid and / or salt thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62215397A (en) * | 1986-03-17 | 1987-09-22 | Nippon Kayaku Co Ltd | Production of hyaluronic acid |
| JPS62289198A (en) * | 1986-06-09 | 1987-12-16 | Nippon Kayaku Co Ltd | Novel process of producing hyaluronic acid |
| JPS6394988A (en) * | 1986-10-08 | 1988-04-26 | Meiji Seika Kaisha Ltd | Production of hyaluronic acid |
| JPS63141594A (en) * | 1986-12-02 | 1988-06-14 | Denki Kagaku Kogyo Kk | Production of hyaluronic acid |
| JP2587680B2 (en) * | 1988-05-13 | 1997-03-05 | チッソ株式会社 | Method for producing fine powder of hyaluronic acid or sodium hyaluronate |
-
1990
- 1990-10-23 JP JP2283394A patent/JPH0630605B2/en not_active Expired - Fee Related
-
1991
- 1991-10-22 DE DE19914134854 patent/DE4134854A1/en active Granted
- 1991-10-23 GB GB9122504A patent/GB2249315B/en not_active Expired - Fee Related
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| US7109011B2 (en) | 1994-07-01 | 2006-09-19 | The Board Of Regents Of The University Of Oklahoma | Hyaluronan synthase gene and uses thereof |
| US8735102B2 (en) | 1994-07-01 | 2014-05-27 | The Board Of Regents Of The University Of Oklahoma | Hyaluronan synthase genes and expression thereof in Bacillus hosts |
| US6852514B2 (en) | 1994-07-01 | 2005-02-08 | The Board Of Regents Of The University Of Oklahoma | Hyaluronate synthase gene and uses thereof |
| US6855502B2 (en) | 1994-07-01 | 2005-02-15 | Paul H. Weigel | Hyaluronate synthase gene and uses thereof |
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| US7094581B2 (en) | 1998-10-26 | 2006-08-22 | The Board Of Regents Of The University Of Oklahoma | Hyaluronan synthases and methods of making and using same |
| US6582606B2 (en) | 2000-05-18 | 2003-06-24 | Novozymes A/S | Microfiltration using activated carbon |
| WO2001087468A1 (en) * | 2000-05-18 | 2001-11-22 | Novozymes A/S | Microfiltration using activated carbon |
| US8933054B2 (en) | 2005-03-22 | 2015-01-13 | Q.P. Corporation | Low molecular weight hyaluronic acid and/or salt thereof, method for producing same, and cosmetic preparation and food composition containing same |
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| US8367818B2 (en) | 2006-02-24 | 2013-02-05 | Q.P. Corporation | Low molecular weight hyaluronic acid and/or salt thereof, and cosmetic preparation, pharmaceutical composition, and food composition each using same |
| AU2008322629B2 (en) * | 2007-11-13 | 2013-05-16 | Bio-Technology General (Israel) Ltd. | Dilute filtration sterilization process for viscoelastic biopolymers |
| WO2009063291A1 (en) * | 2007-11-13 | 2009-05-22 | Bio-Technology General (Israel) Ltd. | Dilute filtration sterilization process for viscoelastic biopolymers |
Also Published As
| Publication number | Publication date |
|---|---|
| DE4134854A1 (en) | 1992-04-30 |
| GB9122504D0 (en) | 1991-12-04 |
| JPH0630605B2 (en) | 1994-04-27 |
| JPH04158796A (en) | 1992-06-01 |
| GB2249315B (en) | 1993-05-26 |
| DE4134854C2 (en) | 1993-03-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20031023 |