Copper biosorption by wild type and two engineered (Rim101 Delta, Och1 Delta) Saccharomyces cerevisiae biomasses was analyzed. Potentiometric titrations revealed that carboxylic, amino and, to less extent, phosphoric groups are responsible for the biosorption of copper. Maximum biosorption capacities of copper equal to 28.8, 8.0 and 7.5 mg/g were found at pH = 6 for wild type, Rim101 Delta and Och1 Delta respectively. A mechanistic equilibrium model was developed to describe the dependence of metal and proton binding on pH and metal liquid concentration. The developed model accounts for the exchange of metal ions with protons from functional groups in acidic form and for the sorption of metal ions on ionized groups. Model parameters were estimated based on potentiometric titration data and adsorption isotherms leading to satisfactory fitting for any considered strain. Metal removal by living cells was investigated to determine bioaccumulation capacity. No statistically significant difference was found among the bioaccumulation capacities of the three strains. For any strain, bioaccumulation could not enhance copper removal. (C) 2014 Elsevier B.V. All rights reserved.