What are the main types of Fermenters bioreactors used in animal cell culture What are the problems one would face with animal cell culture compared to microbial cell culture?

Answer 1

- Animal cells are large (10 to 20 micrometer diameter), slow growing, and are very shear sensitive. Hence, animal cell reactors must be gently agitated and aerated - Most animal cells are anchorage dependent, hence, surfaces of glass, specially treated plastics, natural polymers such as collagen, or other support materials are used. - Product concentration is very low and toxic metabolites such as ammonium and lactate are produced. Hence suitable measures must be taken to remove these products continuously. In lab scale, T- flasks , spinner bottles, roller bottles and trays containing shallow liquid cultures are used. Large scale reactors: microcarrier systems, hollow fiber reactors, ceramic matrix systems, weighted porous beads) are used for anchorage dependent cells and Stirred tank reactors and bubble column reactors are used for suspension cultures. 1) With roller bottles, the liquid covers about 25% of the surface area. Bottles are rotated about the long axis with the cells adhered to it's sides. They are therefore dipped in the medium for 25 % of the time and are aerated for 75% of the time. It has the advantage of increased surface area for the cells compared to the T-flasks. But it requires high labour and there is bottle to bottle variability. 2) The use of microcarriers of DEAE or dextran for anchorage dependent cells is an attractive approach. They allow high surface to volume ratio. Cells grow on the surface of the microcarriers, usually in the form of monolayers and sometimes as multilayers. But bead to bead contact will expose cells to great stress. Hence microporous microcarriers are used in which cells grow inside them and stress is reduced. 3) For suspension cultures, conventional bioreactors have been modified to reduce shear rates on cells in suspension. Sail-type and axial hydrofoil agitators have been developed and used for suspension cultures. Many shear protection agents lide serum or Pluronic F-68 are added. 4) Hollow fiber reactors are also used to provide a high growth surface- volume ratio and, therefore, high cell concentrations. Cells are immobilized on the external surfaces of hollow fibres, and nutrients pass through the tubes. However the control of microenvironment conditions are different. Other immobilization based reactors: Tubular ceramic matrix reactors , microencapsulation in spherical membranes and gel encapsulation

Answer 2

The main types of fermenters/bioreactors used in animal cell culture are stirred-tank bioreactors, airlift bioreactors, and perfusion bioreactors. Some common problems faced with animal cell culture compared to microbial cell culture include the need for more complex culture media, sensitivity to shear forces, and higher requirements for oxygen transfer and control of pH. Additionally, animal cells are more prone to genetic instability and have slower growth rates.