Impact of operating variables on the expanded bed adsorption of Saccharomyces cerevisiae cells using a concanavalin A derivatized perfluorocarbon.

The use of fluidizable affinity adsorbents for the adsorption of cells in expanded mode is investigated. Affinity adsorbents have been synthesized by immobilizing the lectin Concanavalin A onto the surface of triazine-activated perfluorocarbon-solids. The adsorbents were found to adsorb Saccharomyces cerevisiae cells from solution with adsorption capacities of up to 6.8 x 10(9) cells mL(-1). Adsorption kinetics were rapid with a time constant of </=8 min. The adsorbed cells could be eluted using 500 mM methyl alpha,D-mannopyranoside, although the kinetics of release were slowed by the multipoint nature of the interaction. The dynamic capacity of the Con A PVA FEP in expanded mode was up to 4.5 x 10(9) cells mL(-1). The operating parameters of bed height, application flow rate, and adsorbent size distribution were investigated for any potential improvements in throughput, which may improve utility for more fragile cells. A decrease in settled-bed height from 20 to 5 cm resulted in a decrease in dynamic capacity of 27% from 4.5 to 3.3 x 10(9) cells mL(-1). An increase in application flow rate from 0.7 to 2.0 mL/min(-1) (resulting in an expansion increase from two- to fourfold) resulted in a 40% decrease in dynamic capacity from 4.0 to 2.4 x 10(9) cells mL(-1). An increase in the mean size distribution of the perfluorocarbon from 42 to 69 microm and therefore the flow rate needed for twofold expansion of 0.7 to 1.5 mL/min(-1) resulted in a 56% decrease in dynamic capacity from 4.0 to 1.8 x 10(9) cells mL(-1). The expanded bed, using certain combinations of the operating parameters, therefore shows significant potential for the robust, high efficiency and high capacity capture and separation of cells.