Affinity Immobilization of Escherichia coli : Catalysis by Intact and Permeable Cells Bound to Starch

Abstract

The binding of viable Escherichia coli cells to an immobilized ligand of a surface receptor for maltodextrins has recently been demonstrated (T. Ferenci and K. S. Lee, J. Mol. Biol. 160 :431-444, 1982). The interaction of bacteria and ligand immobilized in a chromatographic column was investigated over a wide range of applied cell densities, temperatures, eluant pH values, osmotic concentrations, and flow rates. Over 95% retention of bacteria applied to starch-Sepharose was found at cell densities up to 10 9 per ml of matrix, between pH 5.5 and 8.0, between 8 and 55°C, in the presence of 0 to 0.5 M NaCl, and at elution flow rates up to 37 column volumes per h. The catalytic capability and stability of affinity-immobilized cells was demonstrated with the cytoplasmic β-galactosidase activity of starch-bound cells. Intact immobilized bacteria exhibited slowly increasing β-galactosidase activity over several days with a plateau after 6 days. Bacteria made permeable by treatment with toluene were also bound to starch-Sepharose but showed maximum β-galactosidase activity within 1 day and exhibited no loss of enzyme activity in 8 days of continuous elution at ambient temperatures.