Influence of medium composition on oxygen transfer rate in animal cell culture

Experiments were conducted in a 0.25 m diameter bubble column to investigate the effect of animal cell culture medium composition on oxygen transfer rate. Air is used as the dispersed phase. The gas superficial velocity is varied between 0.4 and 2 cm/s (aeration rate ranging between 0.05 and 0.25 vvm) and the bubble column is thus operated in the homogenous regime. Aqueous solutions the composition (electrolyte, protein concentrations) of which mimics a mammalian cell culture medium) are used as the continuous phase. In particular, the effect on oxygen transfer rate of additive such as PVP, Pluronic F-68 which are usually used to protect cells against local hydrodynamic stresses induced by bubble coalescence and bursting is addressed.
For each composition, the mass transfer coefficient is measured by the "gas in – gas out" method using a fast response dissolved oxygen probe. Its increase with gas velocity is measured. The liquid viscosity and surface tension are experimentally determined as a function of culture medium composition. Bubble size distribution is measured at different scales using three experimental techniques: gas disengagement technique, two dual optical probes and photography, which lead to results in good qualitative agreement one with each other. The integrated analysis of these data allows to decouple the effects of the different additive on coefficient kL and on the interfacial area, a.