Magnetically stabilised fluidised bed adsorption: practical benefit of uncoupling bed expansion from fluid velocities in the purification of a recombinant protein from Escherichia coli

A composite magnetite-agarose adsorbent has been fabricated in a bead emuls ification process and, following derivatisation with a peptide, exploited i n the direct, one-step purification to near molecular homogenity of an anti -MUC1 diabody fragment (dbFv) expressed in the periplasm of recombinant Esc herichia coli. Variation of performance with temperature and feedstock conc entration was attributed respectively to conformational variation of the im mobilised ligand and different kinetic driving forces at adsorption. The lo w particle density (1.12 g cm(-3)) resulting from the low mass percentage o f introduced magnetite required that adsorption be operated in a magnetical ly stabilised fluidised bed (MSFB) contactor. The contactor achieved direct adsorption of product from EDTA-treated E coli whole broth while operating under conditions of bed expansion uncoupled from fluid velocity and viscos ity. The generic applicability of such adsorbents and contactors to the dir ect biorecovery of proteins from complex feedstock is discussed. (C) 1999 S ociety of Chemical Industry.