In some cases, a bioburden control prefilter is not necessary because the system is under control and bacteria are not found in significant numbers. In those cases, the filters used are designed to remove the particles in the system, and perhaps some larger microorganisms.
If bioburden control prefilters are used, their intent is usually to remove most, but not all bacteria. The sterilizing filters are then able to perform their function for an entire batch of product without fouling and causing undue difficulties with batch processing.
It is important to understand that bioburden reduction does not imply complete bioburden removal. These filters are in place to reduce the amount of bacteria and other particles to prevent the premature fouling of final, sterilizing filters. Bioburden control prefilters are usually membrane-based filters with pore sizes of 0.45μm to 0.80μm. The filters capture the bulk of the organisms, though not all.
Some users will design systems with the intention of having the bioburden reduction filters act as preliminary sterilizing filters, meaning they are intended to remove all of the bacteria that are expected to be in the system. The final, sterilizing filters are then in place only as a final insurance policy against system upset. This is a conservative approach that increases the safety of the final product, though it is not a required design according to regulatory authorities.
Sources of Bioburden
Unwanted bacteria may enter any system with the blood plasma itself or with materials from outside sources. However, the most likely source of microorganisms is the environment in and around the facility. Molds, yeasts and bacteria that are endemic to the plant location are likely to enter the processes. They may be carried by plant personnel or simply come in with the air.
The type of organisms will depend on the type of environment and climate. A warm moist environment may have numberous molds and bacteria. Dry or cooler environments may also have these, but perhaps in lower numbers, making control somewhat less complex.
Choosing the Right Filter
The choice of filter to use for bioburden reduction and prefiltration is based on the particles and organisms likely to be found in the process. As mentioned above, organisms endemic to the location of the facility (molds, airborne bacteria, yeasts, etc) will be the likely targets of bioburden control filtration. Depending on the size of those organisms and other particles, membrane filters with 0.65µm, 0.45µm or 0.22μm ratings may be used. In some cases, operators may choose the bioburden reduction filter based on its ability to remove all of the bacteria that are likely to be found. The sterilizing filter then only acts as a guard against system upset. In other cases, a pleated depth media filter will remove particles and enough large organisms to protect the critical sterilizing filters from premature fouling.
A critical consideration in choosing the filters, or any filters for processing blood products, is the ability of the filters to allow the product to pass with a minimum of protein binding. The filters should have little to no impact on the process yield nor should they be easily fouled by the protein content of the stream.
Custom systems are designed for new applications and to solve challenges in existing processes. Critical Process Filtration will work with you to design, build and install a cost-effective system that delivers the results you need. Contact us or visit our custom filtration systems page for more information.
Critical Process Filtration has multiple filter options for removing bacteria and other microorganisms. To read more about these filters and bioburden reduction and control in plasma fractionation, click on one of the links below. Critical Process Filtration has created short explanations of how reducing bioburden is one step in assuring product quality and safety.
- Prefiltration and Sterilizing Filtration of Plasma Based Products
- Bioburden Control and Sterilizing Filtration in USP Water Systems
The table below shows filter technology options for bioburden control in plasma fractionation from Critical Process Filtration with links to more detailed data on the filters. Click on the in the appropriate location to download a data sheet for the filter media and configuration that fits your needs.
|Media Code||Filter Media||Filter Grade||Cartridge Data Sheet||Capsule Data Sheet||Disc Filter Data Sheet||Pore Sizes Available (µm)||Features|
|PPD||Pleated Polypropylene Depth Media||Pharmaceutical||0.1, 0.22, 0.45, 0.65, 1.0, 3.0, 5.0, 10, 20, 30, 40, 60, 100||100% polypropylene construction for high purity|
|PGD||Pleated Fiberglass Depth Media||Pharmaceutical||0.22, 0.30, 0.45, 0.65, 1.0, 2.0, 3.0, 5.0, 10, 20, 30||High capacity filters for clarification and prefiltration applications|
|BPS||Asymmetric Polyethersulfone (PES) Membrane||Biophamaceutical||0.03. 0.1, 0.22, 0.45, 0.65, 1.8, 1.0, 1.2||Highly asymmetric, hydrophilic PES membrane in single-layer configurations for high efficiency, high flow rates and low product absorption|
|PPS||Double-Layered Asymmetric Polyethersulfone (PES) Membrane||Biophamaceutical||0.03. 0.1, 0.22, 0.45, 0.65, 1.8, 1.0, 1.2||Symmetric, hydrophilic PES membrane for high efficiency filtration of water.|
|BCWPS||High Capacity Polyethersulfone (PES) Membrane||Biopharmaceutical||0.2 single layer, 0.5 single layer, 0.5/0.2 dual layer||High capacity membrane with single or dual layer configurations for bacteria and particulate reduction, low product adsorption and protection of final filters|
|BPVWL||High capacity, Hydrophilic Polyvinlyidene fluoride (PVDF) Membrane||Biopharmaceutical||0.22, 0.45, 0.65, 1.2||High void volume membrane with high holding capacity for systems that may have high particulate loads|
To estimate the number of filters you will need for your application, use our unique sizing tools.
The filter media used for each process must, of course, be compatible with the fluids used in it. Contact Critical Process Filtration for assistance in determining the compatibility of filter media and support materials with your process.