Sterilizing filtration is the process of removing all microorganisms excluding viruses from the solution, without adversely affecting the product quality.
It is suitable sterilization method (aseptic process) for heat sensitive drug products.
1. Porcelain filter cartridges- Discontinued
2. Asbestos cellulose layers- - Discontinued
3. Membrane filters
Pseudomonas diminuta (currently reclassified as Brevundimonas diminuta)= 0.3x0.6-0.8 µm registered with American Type Culture Collection ATCC No.: 19146.
Use of this organism leads to several advantage-
1. Non-pathogenic to human.
2. Can be consistently cultured under controlled condition to to yield very small , mono-dispersed cells with narrow size distribution.
3. A process stream isolate, it is therefore a realistic potential problem organism.
The disadvantages of B. diminuta are-
1. Not viable in many pharmaceutical formulations.
2. May not be the smallest bacterium potentially encountere d in all formulations, and thus may not
represent bioburden organisms in terms of morphology and physiology.
3. Spite of being stable, batch-to-batch variation in its morphology (size) should be examined
The bacterial challenge test serves two major functions. The filter manufacturer uses it to classify
filters as sterilizing grade if the filter provides a sterile effluent with a minimum of 107 cfu of B.
diminuta ATCC 19146/ cm 2 of effective filter surface area.
The filter challenge test must be performed with actual product or, where justified, suitable
surrogate fluid.
Filter Types-
Current available materials of construction include, but are not limited to polymers such as cellulose
esters, nylon, polyesters, polytetrafluoroethylene, polyvinylidene flouride, polycarbonate, polypropylene, polyethersulfone and polysulfone.
Minor components, such as surfactants may be added to the filter to enhance wettability, or render the filter membrane hydrophilic or hydrophobic.
Hydrophobic means that the membrane pores are not easily penetrated by water or aqueous streams.
Hydrophilic means that the pores of the membrane are readily penetrated by water or aqueous fluids.
Whether the filter is hydrophilic or hydrophobic also greatly affects its ability to properly serve in a
given process. Generally, hydrophilic filters are used for aqueous based liquid processes, while
hydrophobic filters are used for solvent, vent and gas applications.
It is suitable sterilization method (aseptic process) for heat sensitive drug products.
1. Porcelain filter cartridges- Discontinued
2. Asbestos cellulose layers- - Discontinued
3. Membrane filters
Pseudomonas diminuta (currently reclassified as Brevundimonas diminuta)= 0.3x0.6-0.8 µm registered with American Type Culture Collection ATCC No.: 19146.
Use of this organism leads to several advantage-
1. Non-pathogenic to human.
2. Can be consistently cultured under controlled condition to to yield very small , mono-dispersed cells with narrow size distribution.
3. A process stream isolate, it is therefore a realistic potential problem organism.
The disadvantages of B. diminuta are-
1. Not viable in many pharmaceutical formulations.
2. May not be the smallest bacterium potentially encountere d in all formulations, and thus may not
represent bioburden organisms in terms of morphology and physiology.
3. Spite of being stable, batch-to-batch variation in its morphology (size) should be examined
Bacterial Challenge Testing-
Sterilizing grade filter has been defined as a filter which will retain 107 cfu of B.
diminuta ATCC 19146/ cm 2 of effective filter surface area (FDA, 1987), under specified conditions.The bacterial challenge test serves two major functions. The filter manufacturer uses it to classify
filters as sterilizing grade if the filter provides a sterile effluent with a minimum of 107 cfu of B.
diminuta ATCC 19146/ cm 2 of effective filter surface area.
The filter challenge test must be performed with actual product or, where justified, suitable
surrogate fluid.
Filter Types-
Current available materials of construction include, but are not limited to polymers such as cellulose
esters, nylon, polyesters, polytetrafluoroethylene, polyvinylidene flouride, polycarbonate, polypropylene, polyethersulfone and polysulfone.
Minor components, such as surfactants may be added to the filter to enhance wettability, or render the filter membrane hydrophilic or hydrophobic.
Hydrophobic means that the membrane pores are not easily penetrated by water or aqueous streams.
Hydrophilic means that the pores of the membrane are readily penetrated by water or aqueous fluids.
Whether the filter is hydrophilic or hydrophobic also greatly affects its ability to properly serve in a
given process. Generally, hydrophilic filters are used for aqueous based liquid processes, while
hydrophobic filters are used for solvent, vent and gas applications.
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