Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N1/00—Preservation of bodies of humans or animals, or parts thereof
  • A01N1/10—Preservation of living parts
  • A01N1/12—Chemical aspects of preservation
  • A01N1/122—Preservation or perfusion media
  • A01N1/125—Freeze protecting agents, e.g. cryoprotectants or osmolarity regulators
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N1/00—Preservation of bodies of humans or animals, or parts thereof
  • A01N1/10—Preservation of living parts

Definitions

• the present invention relates generally to preserving and stabilizing biological materials by freezing, drying, and freeze-drying, and more specifically to protectant mixtures and aqueous preservation media for preserving biological materials, as well as methods of preserving biological materials and the preserved biological material compositions themselves.
• Biological materials such as proteins, enzymes, cells, tissues, nucleic acid, semen, blood and its components, mammalian organs, and foodstuffs must often be stored and preserved for later use. Preservation of these biological materials is usually achieved by either freezing or drying, or a combination of the two processes.
• drying by evaporation into a moving gas stream ambient air-drying
• drying under vacuum at ambient temperatures vacuum-drying
• drying by contacting a fine mist of droplets with warm air spray-drying
• Simple freezing is often done when drying is either harmful or unnecessary.
• Certain biological materials are best preserved by freeze-drying (lyophilization), a two-step process in which the sample is first frozen and then dried at low temperature under vacuum.
• freeze-drying combines the stresses due to both freezing and drying.
• the freezing step of this process can have undesirable side effects, such as the denaturation of proteins and enzymes, and rupture of cells. These effects result from mechanical, chemical, and osmotic stresses induced by crystallization of ice in these materials.
• the activity of the biological material upon rehydration is lost either in its entirety, or to such a significant extent that the material is no longer useful for its intended purpose.
• protective agents such as cryoprotectants or lyoprotectants (freeze-drying) are used.
• cryoprotectants or lyoprotectants freeze-drying
• protective agents they must be non-toxic to the biological material at the concentrations encountered during the preservation process, and must interact favorably with water and with the biological material.
• Various protective agents have been used in the art, with varying degrees of success. These include fish proteins, certain polymers, skim milk, glycerol, dimethyl sulfoxide, and disaccharides, such as trehalose. Unfortunately, suitable protective agents and cryopreservation protocols have been developed only for a limited number of systems. Disaccharides, such as sucrose and trehalose, are natural cryoprotectants.
• Trehalose is a particularly attractive cryoprotectant because it has actually been isolated from plants and animals that remain in a state of suspended animation during periods of drought. Trehalose has been shown to be an effective protectant for a variety of biological materials, both in ambient air-drying and freeze-drying. Research has shown, (see Crowe, J.H., Crowe., L.M., and Mouriadian, R., Crvobiology., 20, 346-356 (1983)), that liposomes dried in the presence of trehalose retain both their functional and structural integrity upon rehydration.
• U.S. Patent No. 5,512,547 discloses the use of trehalose to preserve botulinum neurotoxin.
• U.S. Patent No. 4,891,319 discloses a method of protecting proteins and other biological macromolecules, such as enzymes, serum, serum complement, antibodies, antigens, fluorescent proteins and vaccine components using trehalose. Specifically, an aqueous mixture containing the macromolecule and trehalose is dried at a temperature above freezing in the presence of 0.05 to about 20% trehalose by weight of the aqueous system.
• trehalose in combination with a polymeric gelling agent, such as carboxymethylcellulose or carboxyethylcellulose. It has been suggested for human blood that saccharides combined with polymers are even more effective cryoprotectants than pure trehalose. See U.S. Patent No. 5,171,661; Sutton, R.L., J.Chem.SocFaraday Trans.. 87, 3747 (1991). Unfortunately, attempts to confirm the beneficial effect of the gelling agents have been unsuccessful. (G. Petrus, I. Heschel, and G. Rau, Cryo-Letters 17, 43-52 (1996), J.H.
• trehalose Another, more serious problem associated with the use of trehalose is that biological materials preserved using trehalose alone are not storage stable for extended periods of time, especially those stored at superambient temperatures and/or in humid environments. In other words, biological materials preserved with trehalose can lose their activity in a matter of hours or days, depending on the humidity and temperature of the storage conditions.
• freeze-drying with trehalose is of limited use for extended term storage of biological materials, such as proteins, enzymes, cells, tissues, nucleic acid, semen, blood and its components, mammalian organs, and foodstuffs, over a wide range of storage conditions, because the material will degrade, and will not have sufficient activity upon reconstitution. From a practical standpoint, this is clearly unacceptable for medical products, as one of the reasons for preserving the materials in the first place is to provide a storage-stable product.
• biological materials such as proteins, enzymes, cells, tissues, nucleic acid, semen, blood and its components, mammalian organs, and foodstuffs
• a protectant mixture for use in preserving biological materials comprising: (a) at least one polyhydroxy compound, where the total amount of polyhydroxy compound in the mixture is from about 5% to about 60% by weight of the mixture if the mixture is an aqueous solution and from about 10% to about 95% by weight if the mixture is in solid form; and (b) phosphate ions, where the total amount of phosphate ions in the medium is such that the molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound is from about 0.025 to about 0.625, can be used with a wide variety of biological materials to provide an aqueous preservation medium.
• This aqueous preservation medium can then be used in a multiplicity of preservation processes, including freezing, freeze-drying and other drying processes, such as spray- drying, vacuum-drying, or ambient air-drying, to provide a stable, preserved composition of the biological material of interest.
• This preserved composition is stable for extended periods of time at superambient temperatures and/or relative humidity. Further, when the preserved biological material composition is rehydrated, the structural and functional integrity of the preserved biological material has been retained to such an extent that the biological material can be used for its intended purpose.
• the present invention also provides a method for preparing a preserved biological material composition from the above-noted preservation medium, as well as the preserved biological material composition itself.
• Fig. 1 is a graph of percent activity recovered from freeze-dried lactate dehydrogenase compositions made using varying amounts and molar ratios of phosphate and trehalose.
• Fig. 2 is a graph of percent activity recovered from frozen lactate dehydrogenase compositions made using varying amounts and molar ratios of phosphate and trehalose.
• Fig. 3 is a graph of percent activity recovered over time from freeze-dried lactate dehydrogenase compositions made using varying amounts and molar ratios of phosphate and trehalose.
• Fig. 4 is a graph of percent activity recovered over time from freeze-dried lactate dehydrogenase compositions made using varying amounts and molar ratios of phosphate and trehalose.
• Fig. 5 is a graph of percent activity recovered over time from freeze-dried lactate dehydrogenase compositions made using varying amounts and molar ratios of phosphate and trehalose.
• Fig. 6 is a graph of glass transition temperatures for various protectant mixtures of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS
• the present invention is based on the remarkable discovery that biological materials can be preserved while retaining substantial activity, when the biological material is combined with the protectant mixture of the present invention to form an aqueous preservation medium, which in turn is formed into a preserved biological material composition by subjecting the aqueous preservation medium of the present invention to (1) various drying techniques, including freeze-drying, ambient air-drying, vacuum-drying, and spray-drying, or (2) other preservation methods known in the art, such as freezing.
• the protectant mixture of the present invention comprises: (a) at least one polyhydroxy compound, where the total amount of polyhydroxy compound in the mixture is from about 5% to about 60% by weight of the mixture if the mixture is an aqueous solution and from about 10% to about 95% by weight if the mixture is in solid form; and (b) phosphate ions, where the total amount of phosphate ions in the mixture is such that the molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound is from about 0.025 to about 0.625.
• the aqueous preservation medium of the present invention comprises: (a) a biological material; (b) at least one polyhydroxy compound, where the total amount of polyhydroxy compound in the medium is from about 5% to about 60% by weight of the medium; and (c) phosphate ions, where the total amount of phosphate ions in the medium is such that the molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound is from about 0.025 to about 0.625.
• a wide range of biological materials can be used with the inventive protectant mixtures to form the aqueous preservation medium of the present invention.
• This preservation medium can then be subjected to the processes of the present invention to make a preserved biological material composition.
• biological materials include, without limitation:
• enzymes such as lactate dehydrogenase and phosphofructokinase
• proteins such as insulin
• tissue including skin, veins and arteries
• viruses such as adenovirus
• blood and its components, including red blood cells, white blood cells and platelets;
• cells including prokaryotic cells (including bacteria) and eukaroytic cells;
• Polyhydroxy compounds useful in the present invention include natural and synthetic monosaccharides and polysaccharides, other carbohydrates, and polyalcohols and their derivatives.
• polysaccharides are defined as saccharides containing two or more monosaccharide units.
• the individual polyhydroxy compounds can be used singly, or in combination with other types of polyhydroxy compounds. From the wide variety of useful polyhydroxy compounds, the use of monosaccharides and polysaccharides is preferred.
• disaccharides such as trehalose, maltose, lactose, and sucrose are preferred for use in the present invention, with trehalose being most preferred.
• the amount of polyhydroxy compound present in the protectant mixture, preservation medium, and preserved composition of the present invention depends upon the specific polyhydroxy compounds, and biological material selected for use, as well as the mass of biological material being preserved. This can be adjusted and optimized for a given system.
• the polyhydroxy compounds are present in the protectant mixture of the present invention in a total amount of from about 5% to about 60% by weight of the mixture, where the mixture is an aqueous solution.
• the protectant mixture is supplied as a solid, for example as a powder
• the polyhydroxy compounds should be present in a total amount of from about 10% to about 95% by weight of the mixture, with an amount in the range of about 20% to about 95% by weight of the mixture being preferred.
• the protectant mixture is an aqueous solution
• the polyhydroxy compounds are preferably present in a total amount such that the total amount of polyhydroxy compound in the mixture is from about 5% to about 40% by weight of the mixture, with an amount in the range of about 10% to about 30% by weight of the mixture being particularly preferred.
• the polyhydroxy compounds should be present in the preservation medium of the present invention in an amount such that the total amount of polyhydroxy compounds in the aqueous preservation medium is from about 5% to about 60% by weight of the aqueous preservation medium.
• the total amount of polyhydroxy compound present should be from about 5% to about 40% by weight of the aqueous preservation medium, with an amount in the range of about 10% to about 30% by weight of the aqueous preservation medium being particularly preferred. It should be emphasized that the above ranges can be varied, for example, depending upon the amount of biological material in the preservation medium and the preservation method chosen for use.
• a preserved biological material composition having from about 5% to about 95% polyhydroxy compound by weight of the composition. Again, this amount will depend on the mass of the biological material being preserved, the amount of phosphate present, and the amount of water removed from the system during preservation.
• the amount of polyhydroxy compound in the preserved biological composition can be determined from the amount present in the protectant mixture and/or aqueous preservation medium. Alternatively, the amount of polyhydroxy compound in the preserved biological material composition can be determined by analytical methods known in the art, such as column chromatography.
• any source of phosphate ions can be used in the protectant mixture, preservation medium, preservation process, and preserved composition of the present invention. While not wishing to be bound by any particular theory, it is believed that the phosphate ions form a complex with the polyhydroxy compound, which may contain several molecules of the polyhydroxy compound in a three-dimensional supermolecular structure cross-linked by the phosphate ions.
• the aqueous preservation medium has a much higher viscosity than a system containing the polyhydroxy compound alone in the same amount, and the preserved biological material composition has a higher glass transition temperature (T g ) than a composition containing only the polyhydroxy compound.
• T g glass transition temperature
• the phosphate ions can be provided from any source, including acids and salts. The use of sodium and potassium salts are preferred.
• Potassium salts are most preferred, because they have excellent solubility characteristics at low temperature, and crystallize as anhydrous crystals. Therefore, the phosphate ions are preferably provided through the use of sodium and/or potassium salts, with the use of a mixture of monobasic and dibasic potassium phosphate being particularly preferred.
• the amount of phosphate ion that is optimal for a given protectant mixture and/or preservation medium depends on several variables, including the specific biological material to be preserved, the amount and type of polyhydroxy compound in the protectant mixture and/or preservation medium, and the amount of biological material in the system.
• phosphate ions should be present in the protectant mixture and/or aqueous preservation medium in a total amount such that the molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound is from about 0.025 to about 0.625.
• the phosphate ions are present in an amount such that the molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound is from about 0.0375 to about 0.625.
• the molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound will remain substantially constant throughout the preservation process, resulting in a preserved biological material having substantially the same molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound.
• the amount of phosphate ions present in the preserved biological material composition follows directly from the amount present in the aqueous preservation medium.
• the amount of phosphate ions in the preserved biological material composition can be determined analytically by methods known in the art, including ion chromatography and chemiluminescence.
• the useful amount of phosphate ions can also be determined on the basis of moles of phosphate ion per moles of the polyhydroxy compound by multiplying the above ratios by the number of hydroxyl groups present per mole of the polyhydroxy compound being used.
• trehalose and sucrose have 8 moles of hydroxyl groups per mole of compound. Therefore, where trehalose or sucrose is used as the polyhydroxy compound, the ratio of from about 0.025 to about 0.625 moles of phosphate ions per mole of hydroxyl groups can be achieved by adding sufficient phosphate ions to achieve a molar ratio of phosphate ions to sucrose or trehalose of about 0.2 to about 5.
• the preferred molar ratio of from about 0.0375 to about 0.625 translates to a molar ratio of phosphate ions to sucrose or trehalose of from about 0.3 to about 5.
• the effectiveness of the phosphate ions in stabilizing and ' preserving the structure and function of a given biological material increases as the molar ratio of phosphate ions to hydroxyl groups increases from zero, but only up to a point (the optimum ratio), after which the use of additional phosphate ion provides no or only a slight increase in effectiveness.
• the optimal ratio depends on several factors, including the amount and type of biological material used, the amount and type of polyhydroxy compounds in the preservation medium, the pH of the preservation medium, and the preservation technique to be utilized.
• phosphate ions at a molar ratio of phosphate ions to hydroxyl groups in the polyhydroxy compound that is higher than that found to be optimal for a given aqueous preservation medium of the present invention may, in many circumstances, still result, upon preservation, in a preserved biological material composition having improved structural and functional integrity, such as improved activity on rehydration, storage stability, or advantages in cost or processing over a preserved composition resulting from an aqueous preservation medium containing only the polyhydroxy compound. Therefore, it is preferred that the ratio for a given aqueous preservation medium of the present invention be less than or equal to that resulting in optimal stability and activity upon rehydration, with the use of the optimum ratio being most preferred. However, an aqueous preservation medium having a ratio greater than that needed for optimal activity of the preserved biological material upon rehydration can be used.
• the protectant mixture and/or aqueous preservation medium of the present invention can contain other components.
• they may contain a buffer to maintain the pH of the medium at an optimal value for a given biological material.
• the phosphate ions in the mixture and/or medium function as a buffer as well, so additional non-phosphate buffers may not be needed.
• the amount of phosphate ions present in the buffer should be included in determining the molar ratio of phosphate ions to hydroxyl groups of the polyhydroxy compound in the mixture and/or aqueous preservation medium, as well as the resulting preserved biological material composition.
• the pH at which a given biological material is most stable is known in the art.
• the preservation media of the present invention should have a pH in the range from about 5 to about 10, with a pH in the range from about 6 to about 9 being most preferred.
• the protectant mixture and/or aqueous preservation medium may also contain one or more antioxidants, such as sodium thiosulfate, ascorbic acid, citric acid, and sodium citrate. If an antioxidant is used, it can be present in an amount known to be useful in the art.
• the protectant mixture and/or aqueous preservation medium may also contain other components that may act as drying agents and/or osmoprotectants, such as methanol, ethanol, glycerol and DMSO. These components tend to reduce residual moisture or balance osmotic stresses in the preserved biological material compositions made from the aqueous preservation media of the present invention, which may in some cases result in better storage capability.
• the protectant mixture of the present invention can be prepared as follows.
• the polyhydroxy compound and the source of phosphate ions are added in the desired proportion to an aqueous solution. It is preferred that the phosphate ion source be dissolved in the solution prior to the addition of the polyhydroxy compound.
• the mixture may be heated if necessary to effect dissolution.
• the solution should be mixed thoroughly, until a homogenous protectant mixture is obtained.
• This protectant mixture can then be stored as an aqueous solution, or can be subjected to various processes known in the art to produce a solid mixture, such as a powder.
• the powder can be anhydrous or a partially crystalline hydrated material.
• the protectant mixture is a solid, such as a powder
• the solid mixture can be directly added to an aqueous solution containing the biological material to form the aqueous present medium.
• the protectant mixture in the form of an aqueous solution is then added to an aqueous solution of the biological material.
• the aqueous solution of biological materials is preferably prepared in the same buffer. These two solutions are then thoroughly mixed, to form the aqueous preservation medium of the present invention.
• an antioxidant is being used, it is generally added to the aqueous solution of biological material before addition of the protectant solution.
• the amount of biological material used in the aqueous preservation medium of the present invention ' can be varied as desired, depending for example upon the specific biological material to be preserved, the amounts of phosphate ions and polyhydroxy compound present, the preservation technique to be employed.
• the aqueous preservation medium can then be preserved by one or more techniques known in the art, including freezing, freeze-drying, vacuum-drying, ambient air-drying, and/or spray-drying, to provide a preserved biological material composition of the present invention.
• the resulting preserved biological material composition can be anhydrous, or can be a partially crystalline hydrated material. It is preferred that the preserved biological material be substantially anhydrous in nature.
• substantially anhydrous means that the preserved biological material composition contains less than
• EXAMPLE 1 Various protectant mixtures in aqueous solution form were made in Butterfield's buffer (0.6mM potassium phosphate buffered water having a pH of 7.2), by adding predetermined amounts of a polyhydroxy compound and phosphate ions, and mixing to form a homogenous solution. A given protectant mixture was then added to an L. acidophilus cell solution in a 1 :1 mass ratio, and the resulting aqueous protective medium was thoroughly mixed and allowed to incubate at room temperature for 30 minutes.
• the L. acidophilus cell solution was prepared as follows: concentrated L. acidophilus bacterial cultures having a 15.3 wt% dry mass were mixed with 1.9% sodium thiosulfate to form an L. acidophilus cell solution and allowed to incubate at room temperature for 30 minutes. Samples of each aqueous protective medium made in the above manner were then subjected to either freezing, freeze-drying or vacuum-drying.
• the aqueous preservation medium was dripped through a 25 gauge syringe needle into liquid nitrogen.
• the drops usually formed pellets of 2-3 mm in diameter, which froze completely within about 10 seconds.
• the samples that were freeze-dried were subjected to freezing as detailed above, and the resulting pellets were placed in a Virtis 12EL freeze dryer on precooled shelves at a temperamre no greater than -45°C. Additionally, small samples of the preservation medium were weighed to determine their density, and then freeze-dried as a thin layer in glass dishes. These samples were weighed before and after freeze-drying to calculate the amount of water lost by each sample during freeze-drying, and hence to determine the amount of water needed for rehydration.
• freeze-dried samples were subjected to the following freeze-drying protocol, where the pressures and temperatures are set points.
• the freeze dryer was evacuated with a pressure of 0 mtorr.
• the samples were held at -45°C and 0 mtorr for 1200 minutes, after which the temperature and pressure were increased to -40°C and 20 mtorr, respectively, over a period of 50 minutes.
• the samples where then held at -40°C and 20 mtorr for 600 minutes.
• the temperamre was then increased to — 35°C over a period of 50 minutes, and the samples were then held at -35°C and 20 mtorr for 600 minutes.
• the temperature and pressure were next increased to -30°C and 50 mtorr, respectively, over 50 minutes and the samples were then held at — 30°C and 50 mtorr for 600 minutes. At the end of that period of time, the temperature and pressure were increased to — 25°C and 100 mtorr, respectively, over 50 minutes, and the samples were held at— 25°C and 100 mtorr for 600 minutes. The temperature was then increased to — 20°C over 50 minutes, and the samples were then held at -20°C and 100 mtorr for 600 minutes. The temperamre was next increased to — 10°C over 100 minutes, and the samples were held at that temperature and 100 mtorr for 600 minutes.
• the samples were then increased to a final temperature of 40°C at a rate of 0.5°C/min, at 50 mtorr. The samples were then held at the final temperature at 0 mtorr for 1200-2400 minutes. The freeze dryer was then vented with nitrogen gas, and the preserved cell composition samples were removed, sealed in 50 ml plastic centrifuge tubes, and stored in a 37°C incubator.
• 0.2 ml of the preservation medium was placed in a 1.8 ml plastic microcentrifuge tube.
• the samples were then placed into a Savant Instruments SVC-100H SpeedVac Concentrator vacuum dryer and rotary evaporated at room temperature for approximately 4 days at a final pressure of 85 mtorr, to obtain preserved cell compositions.
• the tubes were then sealed, and stored at room temperamre in a desiccator.
• additional samples from the aqueous preservation media were taken, diluted, and plated on agar medium using a standard pour-plating technique to determine the viable cell number in the preservation medium prior to any preservation process being conducted.
• the samples were diluted to achieve a cell concentration of about 100 cells/ml.
• One or two milliliters of the diluted preservation medium were then placed in a petri dish and mixed with liquid agar growth medium (15 g/L agar with 55 g/L MRS Lactobacillus Broth and 0.1% L-cysteine) at 45°C.
• the dish was allowed to cool, solidifying the agar, at which time the dishes were inverted and placed in an anaerobic growth chamber (GasPak jar) at 37°C for 2-3 days, at which time colonies were visible in the agar.
• each colony represents a single viable cell in the preservation medium.
• portions of the preserved cell compositions prepared by freeze- drying and vacuum drying were rehydrated in Butterfield's buffer. Freeze-dried samples were rehydrated to approximately 1/100 th of their original concentration, allowed to incubate for 30 minutes, diluted, and plated as described above. Vacuum- dried samples were rehydrated to approximately 1/5* their original concentration, mixed to fully dissolve the pellet, diluted, and plated as described above. All samples were plated in at least triplicate. For these experiments, time zero is the time at which the samples were removed from the dryers.
• the preserved cell compositions that were prepared by freezing samples of the preservation medium in liquid nitrogen were plated as described above after complete thawing at room temperature had occurred.
• results for a given set of samples are set forth below in Table 1, where the numbers represent the percent of original activity that was recovered upon rehydration.
• the "solution” column provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone” sample being defined as 100%.
• Example 2 The procedure of Example 1 was repeated, using phosphate, carbonate, or sulfate ions with polyhydroxy compounds in varying amounts.
• the results for a given set of samples are set forth below in Table 2, where the numbers represent the percent of original activity that was recovered upon rehydration.
• the "solution” column' provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone” sample being defined as 100%.
• Example 3 The procedure of Example 1 was repeated, using preservation media containing various sources of phosphate ions in varying amounts, and varying amounts of trehalose, with the exception that the freeze-dried samples were dried to 50°C. In addition, the residual water in the freeze-dried samples was measured by Karl Fischer (KF) analysis, and the glass transition temperature (T g ) was obtained. The results for a given set of samples are set forth below in Table 3, where the numbers represent the percent of original activity that was recovered upon rehydration. The "solution" column provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone" sample being defined as 100%.
• Example 4 The procedure of Example 1 was repeated, using varying amounts of trehalose and different phosphate ion sources in the preservation medium, with the exception that the freeze-dried samples were dried to a temperature of 50°C. In two samples, ethanol was added as a drying agent to the preservation medium, while in one sample, the L. acidophilus cells were "washed” (centrifuged, decanted and resuspended) to remove residual growth medium. Media containing different buffers were also tested. The results for a given set of samples are set forth below in Table 4, where the numbers represent the percent of original activity that was recovered upon rehydration. The "solution” column provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone” sample being defined as 100%.
• thio is shorthand for 1.9% sodium thiosulfate. 3 NA: Samples with ⁇ 10% recovery were not assayed at later time points.
• Example 1 The procedure of Example 1 was repeated, using trehalose, phosphate ions, and various antioxidants or no antioxidant, with the exception that the samples were freeze- dried to a temperature of 50°C.
• the results for a given set of samples are set forth below in Table 5, where the numbers represent percent of original activity that was recovered upon rehydration.
• the "solution” column provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone” sample being defined as 100%.
• Example 2 The procedure of Example 1 was repeated, with the exceptions that a Pediococcus species was substituted for L. acidophilus cells, and the freeze-dried samples were dried to a temperature of 25°C or further dried to 50°C.
• the results for a given set of samples are set forth below in Table 6, where the numbers represent percent of original activity that was recovered upon rehydration.
• the "solution” column provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone + thio" sample being defined as 100%.
• L -Lactate dehydrogenase (LDH, EC 1.1.1.27, Type II, rabbit muscle) was dialyzed overnight at 4°C in 100 mM potassium phosphate buffer solution at pH 7.5.
• the total protein content was assayed using SIGMA DIAGNOSTIC, a protein determination kit purchased from Sigma Chemical Company (St. Louis, Missouri), using the modified biuret method of Ohnishi and Barr, "Simplified Method for Quantitating Protein using the Biuret and Phenol Reagents ,” Analytical Biochem. 86: 193-200 (1978).
• the protein assay was conducted at the characteristic absorption at 725 nm at room temperature using a Varian UV Spectrophotometer.
• the reaction mixture contained 100 mM potassium phosphate buffer (pH 7.5), 0.150 mM NADH, and 1.20 mM pyruvic acid.
• the dialyzed LDH was diluted with the same potassium phosphate buffer that had been used for dialysis.
• the resulting enzyme solution had a
• the mixture sets had a trehalose concentration of 200 mM, 400 mM and 600 M, respectively.
• Each mixture set consisted of four separate protectant samples, containing phosphate ions in a concentration of 100 mM, 300 mM, 500 mM and 700 mM, respectively. These samples were made by dissolving the trehalose in an aqueous phosphate solution containing a given amount of phosphate ions.
• LDH solution Two milliliters of the LDH solution were then mixed with 2 ml of each of the twelve protectant mixtures to provide 4 ml solutions of aqueous preservation media having a trehalose concentration of either 100 mM, 200 mM, or 300 mM, LDH
• the samples were held at -45°C and 0 mtorr for 600 minutes, after which the temperature and pressure were increased to -40°C and 20 mtorr, respectively, over a period of 50 minutes.
• the samples where then held at - 0°C and 20 mtorr for 600 minutes.
• the temperature was then increased to — 35°C over a period of 50 minutes, and the samples were then held at-35°C and 20 mtorr for 600 minutes.
• the temperature and pressure were next increased to -30°C and 50 mtorr, respectively, over 50 minutes and the samples were then held at — 30°C and 50 mtorr for 600 minutes.
• the temperature and pressure were increased to — 25°C and 100 mtorr, respectively, over 50 minutes, and the samples were held at -25°C and 100 mtorr for 600 minutes.
• the temperature was then increased to -20°C over 50 minutes, and the samples were then held at -20°C and 100 mtorr for 600 minutes.
• the temperature was next increased to — 10°C over 100 minutes, and the samples were held at that temperature and 100 mtorr for 600 minutes.
• L -Lactate dehydrogenase (LDH, EC 1.1.1.27, Type II, rabbit muscle) was dialyzed overnight at 4°C in 100 mM potassium phosphate buffer solution at pH 7.5.
• the total protein content was assayed using SIGMA DIAGNOSTIC, a protein determination kit purchased from Sigma Chemical Company (St. Louis, Missouri), using the modified biuret method of Ohnishi and Barr, "Simplified Method for Quantitating Protein using the Biuret and Phenol Reagents," Analytical Biochem. 86:193-200 (1978).
• the protein assay was conducted at the characteristic absorption at 725 nm at room temperature using a Varian UV Spectrophotometer.
• the reaction mixture contained 100 mM potassium phosphate buffer (pH7.5), 0.150 M NADH, and 1.20 mM pyruvic acid.
• protectant mixtures having a volume of 25 ml were then prepared in 50 ml containers. Each mixture contained 400 mM of trehalose, and varying amounts of phosphate ion. To make the first mixture (reference), the trehalose was dissolved in 10 mM potassium phosphate solution. For the second mixture, the trehalose was dissolved in 100 mM potassium phosphate solution. The third and fourth mixtures were made by dissolving the trehalose in 500 mM potassium phosphate solution and 900 mM potassium phosphate solution, respectively. The LDH samples were then mixed with the protectant mixtures to provide 50
• phosphate ion concentration for samples 1-4 was 10 mM, 100 mM, 300 mM, and 500 mM, respectively, for a phosphate ion to trehalose molar ratio of 0.05 for Sample 1, 0.5 for Sample 2, 1.5 for Sample 3, and 2.5 for Sample 4.
• Table 8 The above sample preparation is shown below in Table 8.
• the preserved LDH samples in the vials were removed, the vials were sealed, and stored in either a 37°C incubator, a 30°C incubator or at 4°C in a refrigerator.
• LDH activity was then measured periodically for the samples. Before the activity was measured, each sample was weighed to determine the amount of water loss, and rehydrated with purified water (MilliQ System from Millipore Corp.) in the amount of the water that was lost. LDH activity was then determined using the same method discussed previously.
• Example 1 The procedure of Example 1 was repeated. The results are set forth below in Table 9, where the numbers represent percent of original activity that was recovered upon rehydration.
• the "solution” column provides the amount of viable cells in a given preservation medium, with the amount of viable cells in the "cells alone” sample being defined as 100%.
• Aqueous protectant mixtures containing 7.5% of sucrose or trehalose on a molar basis and varying amounts of phosphate ions provided by either potassium monophosphate or potassium diphosphate were prepared, and 25 microliters of each mixture was sealed into an aluminum Differential Scanning Calorimetry pan. The samples were then quenched by immersion in liquid nitrogen and loaded into the Differential Scanning Calorimeter, which had been preco led to — 140°C. The samples were then scanned at a rate of 5°C/min to a temperamre of 50°C, and the glass transition temperature (T g ) was determined. The results for each sample are shown in Fig. 6,

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Engineering & Computer Science (AREA)
• Dentistry (AREA)
• General Health & Medical Sciences (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Environmental Sciences (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Micro-Organisms Or Cultivation Processes Thereof (AREA)
• Apparatus Associated With Microorganisms And Enzymes (AREA)
• Enzymes And Modification Thereof (AREA)

Priority Applications (9)

Applications Claiming Priority (2)

Publications (2)

Family

ID=24507345

Family Applications (1)

Country Status (15)

Cited By (9)

Families Citing this family (88)

Citations (4)

Family Cites Families (38)

• 2000
  • 2000-07-26 US US09/625,735 patent/US6653062B1/en not_active Expired - Lifetime
• 2001
  • 2001-05-09 KR KR1020037000995A patent/KR100771388B1/ko not_active Expired - Lifetime
  • 2001-05-09 PT PT01945951T patent/PT1303184E/pt unknown
  • 2001-05-09 MX MXPA03000251A patent/MXPA03000251A/es active IP Right Grant
  • 2001-05-09 ES ES01945951T patent/ES2273854T3/es not_active Expired - Lifetime
  • 2001-05-09 DK DK01945951T patent/DK1303184T3/da active
  • 2001-05-09 EP EP01945951A patent/EP1303184B1/en not_active Expired - Lifetime
  • 2001-05-09 BR BRPI0112638-5A patent/BRPI0112638B1/pt not_active IP Right Cessation
  • 2001-05-09 CN CN01813325A patent/CN1444442A/zh active Pending
  • 2001-05-09 CA CA002412330A patent/CA2412330C/en not_active Expired - Lifetime
  • 2001-05-09 DE DE60122896T patent/DE60122896T2/de not_active Expired - Lifetime
  • 2001-05-09 WO PCT/US2001/014939 patent/WO2002009515A1/en not_active Ceased
  • 2001-05-09 JP JP2002515080A patent/JP2004505024A/ja active Pending
  • 2001-05-09 AU AU2001268057A patent/AU2001268057B2/en not_active Expired
  • 2001-05-09 AU AU6805701A patent/AU6805701A/xx active Pending
  • 2001-05-09 AT AT01945951T patent/ATE338458T1/de not_active IP Right Cessation
• 2003
  • 2003-09-05 US US10/657,017 patent/US6919172B2/en not_active Expired - Lifetime
• 2004
  • 2004-03-12 US US10/799,462 patent/US7169606B2/en not_active Expired - Fee Related
• 2007
  • 2007-09-18 JP JP2007241092A patent/JP4889602B2/ja not_active Expired - Lifetime

Patent Citations (5)

Also Published As

Similar Documents

Legal Events