Mass transfer considerations in solid-liquid two-phase partitioning bioreactors: a polymer selection guide

Abstract

BACKGROUND Selection of polymers for two-phase partitioning bioreactors (TPPBs) has been focused primarily on predicting a polymer's affinity for the target molecule. Although the extent to which a polymer absorbs a solute is important, the rate of uptake/release must be sufficiently rapid such that a TPPB is not mass transfer limited. This work focused on developing a guide to identify combinations of polymer diffusivities and diffusional path lengths that will ensure a TPPB is not limited by substrate delivery. RESULTS TPPB systems limited by substrate delivery yielded linear growth, while biologically limited systems exhibited exponential growth. Release rates of phenol from various polymer phases increased as polymer diffusivity increased, or as diffusional path length (polymer bead size) decreased. A polymer selection guide was developed identifying combinations of polymer diffusivity and bead size that will ensure a TPPB is not mass transfer limited, for a desired maximum substrate consumption rate. CONCLUSION In selecting polymers for TPPB applications, solute affinity (extent of uptake) has been relatively well characterized using first principles methods, and the present work has now ‘completed the picture’ by providing a description of polymer transport properties (diffusivity and diffusional path length) to be able to generate a guide for selecting polymers. © 2015 Society of Chemical Industry