BIOTECHNOLOGY LETTERS Volume 17 No.1 (January 1995)p.107-112 Received as revised 7th November EFFECT OF HEAVY METAL UPTAKE ON THE ELECTROKINETIC PROPERTIES OF SACCHAR0MycEs CEREF!lZ4E P. Chen and Y. P. Ting’ Department of Chemical Engineering National University of Singapore Kent Ridge 05 11 SUMMARY The effect of heavy metal ions (Cu*+, Ni*+) on the electrokinetic properties of S. cerevisiae was investigated by microekctrophoresis. The uptake of metal ions is associated with a change in surface charge on the cell surface. Increasing pH results in the cell surface being more negatively charged. Also, the change in the electrophoretic mobiity in the presenceof multi-ions is not simply due to the change in the metal concentration of the solutions, but is also dependenton the metal species involved. INTRODUCTION It is well documented that microbial biomassis capableof removing metal ions from aqueous solutions (Kuyucak & Volesky, 1989; Gadd & de Rome, 1988), and that the uptake capacity of the biomass (both living and dead) is signifkantly influenced by external factors, such as temperature, py biomass concentration and the presenceof other ions (Chen ef al., 1993; Kuyucak & Volesky, 1989; Gadd & de Rome, 1988). The surf&e of microorganismsplays a vitally important role in the interaction between the cell and its environment. In its physiological state, the surIke of a microorganism is negatively charged as a result of the presence of various tknctional groups (such as the carboxyl, hydroxyl, amine and phosphate groups). These negativeiy charged groups on the cell membrane or the cell wall may greatly afkct the uptake kinetics of charged species (including metal ions) on the surface of microbial cells. * Corresponding Author 107