BACKGROUND: Detrimental processing conditions can be expected in any downstream operation where direct contacting between a crude feedstock and a reactive solid phase is supposed to occur. In this paper we have investigated the factors influencing intact yeast cells deposition onto anion and cation exchangers currently utilized for expanded-bed adsorption of biotechnological products. The aim of this study was twofold: (a) to confirm previous findings relating biomass deposition with surface energetics according to the extended Derjaguin, Landau, Verwey and Overbeck theory (XDLVO) theory; and (b) to provide a simple experimental fool to evaluate biomass deposition onto process surfaces. RESULTS: Biomass deposition experiments were performed on an automated workstation utilizing a packed-bed format. Two commercial ion exchangers intended for the direct capture of bioproducts in the presence of suspended biological particles were employed. Intact yeast cells in the late exponential phase of growth were selected as model bio-colloids. Cell deposition was systematically evaluated as a function of fluid-phase conductivity and quantitatively expressed as a biomass deposition parameter (a). CONCLUSION: a alpha <= 0.15 was established as a criterion to reflect negligible biomass adhesion to the process support(s). Biomass deposition experiments further confirmed predictions made on the basis of free interfacial energy calculations as per the extended DLVO approach. (c) 2008 Society of Chemical Industry.