Cell/adsorbent interactions in expanded bed adsorption of proteins

Expanded bed adsorption (EBA) is an integrated technology for the primary recovery of proteins from unclarified feedstock. A method is presented which allows a qualitative and quantitative understanding of the main mechanisms governing the interaction of biomass with fluidised resins. A pulse response technique was used to determine the adsorption of various cell types (yeast, Gram positive and Gram negative bacteria, mammalian cells and yeast homogenate) to a range of commercially available matrices for EBA. Cells and cell debris were found to interact with the ligands of agarose based resins mainly by electrostatic forces. From the adsorbents investigated the anion exchange matrix showed the most severe interactions, while cation exchange and affinity adsorbents appeared to be less affected. Within the range of biologic systems under study E. coli cells had the lowest tendency of binding to all matrices while hybridoma cells attached to all the adsorbents except the protein A affinity matrix. The method presented may be employed for screening of suitable biomass/adsorbent combinations, which yield a robust and reliable initial capture step by expanded bed adsorption from unclarified feedstock.