Mechanistic modelling of copper biosorption by wild type and engineered Saccharomyces cerevisiae biomasses

• Copper biosorption on wild type and two engineered S. cerevisiae strains was studied.
• The main functional groups responsible for biosorption were identified.
• A model describing the influence of pH and metal concentration was developed.
• The influence of cell wall structure on copper biosorption was analyzed.
• Bioaccumulation could not enhance copper removal.

Copper biosorption by wild type and two engineered (Rim101Δ, Och1Δ) 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, Rim101Δ and Och1Δ 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.