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Filtration Applications In Fermentation
创建于2024.09.14
Fermentation and cell culture applications involve preparation of fermentor or bioreactor liquid and gaseous feeds to support growth of the desired cells. There is need to maintain sterility in both liquid and gas feeds to support growth of the desired cells during fermentation process. To fulfill sterility requirement, Filtration application is play vital role.
In this article, Various application of Filtration in fermentation process is discussed. A typical air filtration application for air filtration is illustrated here.
1. Pre-filtration of inlet air:
Air Compressors are used to generate air flow for the manufacturing facility. There are two types of compressors, oil-free and oil-lubricated.
Pre-filtration of inlet air is become necessary for removal of oil droplets in oil-lubricated air compressor. A coalesce filter, like glass fiber filter can provide greater than 99.9% removal of oil and also remove water droplets (Dew) in wider range. This glass-fiber filter is also acts as an excellent pre-filter for the hydrophobic membrane pleated filters that mainly used for sterilizing the inlet air to the fermentor.
For oil-free compressors, a pre-filter acts to remove dirt in the air system & extending the life of the final filter. For use with fermentation air, a cellulose pleated filter and polypropylene filters are use for this application.
2. Sterile Air Filtration:
Bacteria and bacteriophage, when present in air feeds, can enter fermentation tanks or bioreactors and contaminate the product. This can destroy the desired producing cells and reduce yields. Therefore, to supply this sterile air is crucial for fermentation process.
There are various methods considered for the sterilization of fermenter inlet air. These include filtration, heat, irradiation, washing with sterilizing chemicals, and electrostatic precipitation. Where, Washing and electrostatic precipitation are not effective for the removal of microorganisms. Heat and irradiation are not inexpensive. Hence, Filtration is the only technique that meets all the requirements for sterilizing fermenter inlet air.
Hydrophobic membrane pleated filters are widely recommended for this. The hydrophobic (water repelling) nature of these membranes can provide for bacteria and bacteriophage removal with 100% efficiency under moist or dry operating conditions. This is key benefit over fiberglass and cartridges.
For some fermentation process, the high elevated temperature filtered air is requirement. For this, the filter is made of inherently hydrophobic PTFE used.
3. Sparging:
Sparging acts to disperse air evenly in the fermentor or bioreactor containing the growth medium and product. For this application is porous stainless steel sparging elements used, which provides an uniform and fine aeration gas dispersion. These SS elements are fabricated with one face of porous metal and one face of solid metal.
Fine grades of porous stainless steel (ie.3.0 µm) are ideal even for shear-sensitive mammalian cell cultures because of their high gas transfer and low-shear aeration capability.
4. Exhaust Air/Off-Gas Filtration:
The purpose of a vent filter on a sterile fermentation tank is twofold;
· To prevent contamination of the tank and to provide containment of the material inside the tank. Prevention of contamination in the tank is desirable for processes that involve long fermentation cycles or require a sensitive fermentation medium (e.g., tissue culture medium).
· To prevent the releasing of organism from fermentation tank to protect the environment and prevent the escape of microorganisms from the fermentation tank.
The exhaust filtration system for a recombinant or mammalian cell fermentor/bioreactor must vent sterile air to the environment and provide a sterile barrier to prevent ingress of contaminants. Additionally, it must be in situ steam sterilizable, and typically has a clean differential pressure of less than 1 psid.
The recommended exhaust filtration system design in two stages;
· Pre-filter (typically 1.2 μm polypropylene filter cartridge): It remove aerosolized particles and liquid droplets containing cells or growth media from the fermentation off-gas or exhaust air and extend the extend the service life of the final sterilizing filter.
· Hydrophobic membrane (PVDF or PTFE ) filter cartridge (0.2 μm): It prevent organisms from entering or leaving the controlled zone, even in the presence of water droplets and saturated gas.
5. Filtration of Fluid Raw Materials:
Fermentation and cell culture growth media are frequently sterilized by filtration, especially when heat-labile components are present. The 0.xn--2-m-yyc hydrophilic membrane sterilizing filter is widely use for these applications. Positive zeta potential hydrophilic membrane is enhanced removal of bacterial endotoxins (pyrogens) from makeup water.
Polypropylene filters are also an excellent choice for pre-filtration of aggressive solvents and viscous fluids, and for applications requiring high flow rates.
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