Assessment of liquid-cell membrane mass transfer resistance on growth kinetics in cell culture analog bioreactors

Characterization of the mass transfer limitations in bioreactors used in cell culture analog (CCA) systems is essential when designing and evaluating their performance. The majority of material transfer studies for gaseous substrates are based on the assumption that the primary resistance is at the gas/liquid interface. This study examines the use of hollow fiber membranes to enhance gas/liquid transport. The liquid/cell interfacial resistance is thus uncoupled from that of the gas/liquid and they can be examined separately to evaluate their potential impacts. A reduction in the mean velocity gradient while maintaining a constant substrate flux into the liquid resulted in a shift in the limiting resistance from the gas/liquid to liquid/cellular interface. This shift manifested itself as an increase in the Monad apparent half saturation constant for the chemo-autotrophic methanogenic microbial system selected as a convenient analog. The result of this work significantly influences the design and/or evaluation of reactors used in the BME research area related to animal surrogate or CCA systems. Although a reactor can be considered as well mixed, based on spatial invariance in cell density, we demonstrated that significant mass transfer resistance may remain at the liquid/cellular boundary layer