ADSORPTIVE PHENOMENA INVOLVING BACTERIAL CELLS AND AN ANION EXCHANGE RESIN

Abstract

Adsorptive phenomena involving Escherichia coli and an anion exchange resin, Dowex 1 in chloride form, were studied in terms of three categories; attachment, loose immobilization and repulsion. Attachment was directly quantified, but the latter two were estimated by the ratio between cell concentrations in the inter-particle space in resin sediment (C_r) and in the supernatant (C_l). Attachment was accompanied by proportional desorption of chloride ions. Attachment and loose immobilization with unmodified and modified cells were affected by pH, suggesting that the number and dissociation balance of anionic and cationic groups of bacterial surface are involved in both of them. Attachment of more cells became difficult with the increase in attached cell density. This was attributed to the repulsion between free and attached cells. When cell concentration in bulk solution was not so high, the repulsion varied with the amount of attached cells and pH. Under the conditions where the repulsion was great, it was visible as a thin transparent zone at the boundary between resin sediment and supernatant. A previously postulated cationic layer around the resin is discussed in terms of the repulsion. When cell concentration in bulk solution increased greatly, free cells again attached to the resin. This was attributed to decreased repulsion and a possible mechanism is discussed.