(467f) Foamless and Bubble Free Dynamic Gas-Liquid Mixing in Cell Culture Bioreactor

Advances in metabolic engineering have increased cell densities and yields in production of monoclonal antibodies and therapeutic proteins.  However, scale-up become more difficult for high cell density cell culture mainly due to foaming, excessive dissolved CO₂ and uncontrolled osmolality levels.  Increase in hydrostatic liquid head of larger scale bioreactors favors gas dissolution but not dissolved CO₂ removal.  Attempts to remove excessive CO₂ by sparging with air are limited by the amount of foaming this cause.  Countering excess foaming with antifoaming agents reduces gas exchange rate and fouls downstream processing equipment.  Yield reduction up to 65% has been reported during scale-up to 10,000 L bioreactors.  At present, no existing commercial process is capable of achieving these optimal levels without creating excessive shear and foaming.  Against conventional wisdom, a dynamic surface gas exchange technique has been demonstrated to overcome a reduction in surface-to-liquid volume ratio during scale up.     By controlling the dissolved CO₂ levels, sodium bicarbonate addition for pH control can be minimized, resulting in improved cell viability and product yield.  As bioreactors are scaled up, the static liquid surface to volume ratio will decrease.  However, it was discovered that dissolved CO₂ can be removed from large bioreactors without the typical process limitations.   Data from over 100 fed-batch runs and 150 L pilot data will be summarized and presented.