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

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Abstract
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 × 109 cells mL−1. Adsorption kinetics were rapid with a time constant of ≤8 min. The adsorbed cells could be eluted using 500 mM methyl α,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 × 109 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 × 109 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 × 109 cells mL−1. An increase in the mean size distribution of the perfluorocarbon from 42 to 69 μm 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 × 109 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. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 506–516, 2003.