Biosorption of heavy metals by Saccharomyces cerevisiae as a function of medium conditions

Biosorption of Cu(II) and Cr(VI) ions by the yeast Saccharomyces cerevisiae has been investigated as a function of medium conditions. For Cu(II) ions, designated optimum medium conditions were pH 5.0, 30 °C temperature, 75 ppm initial Cu(II) concentration and 3 g/L biomass concentration. At these conditions, maximum Cu(II) uptake was 11.6 mg/g. It was observed that, 0.1 M EDTA solution was an effective chelating agent for desorption of Cu(II) ions from Cu(II) loaded biomass. Both ethanol and sodium hydroxide treatment enhanced the Cu(II) biosorption capacity. The cells at lag phase of growth curve of S. cerevisiae have a higher biosorptive capacity for Cu(II) ions than that of stationary phase. Maximum metal uptake for Cr(VI) ions is reached at pH 2.0, 30 °C temperature, 60 ppm initial Cr(VI) concentration and 8 g/L biomass concentration as 4.76 mg/g.Biosorption of Cu(II) and Cr(VI) ions by S. cerevisiae explained well with Langmuir model and biosorption kinetics of these metal ions follows pseudo-second order rate model. Biosorption heats for Cu(II) and Cr(VI) ions were calculated as, 3.30 and 2.50 kcal.mol-1, respectively. Activation energies for these metal ions were determined as 1.456 and 1.463 kcalmol-1, respectively.