Fig. 1: Overview of experimental procedures.

a Measured growth curve of S. cerevisiae yeast cells (absorbance accuracy is approximately 1.75% of reported values). b High-performance liquid chromatography (HPLC) analysis results, performed to identify the number of washes with ultrapure water required to remove medium residues and metabolites from harvested yeast cells before being used in biosorption experiments: i) pure culture medium showed a peak at 8 mins representing glucose; ii) in the supernatant of the harvested liquid culture, glucose was not present but ethanol was produced (peak at 18 mins); iii) in the supernatant after the first wash of yeast cells with ultrapure water there were almost no peaks representing the presence of sugars or organic acids in the solution; iv) in the supernatant after the second wash of yeast cells with ultrapure water there were no peaks at all. Therefore, it was decided to wash the harvested cells twice to ensure absence of organic compounds that might affect further experiments. c Yeast powder after lyophilization and scanning electron microscopy (SEM) imaging of freeze-dried yeast cells (scale bar: 5 μm). d Main steps of kinetic and equilibrium experiments involving the addition of freeze-dried yeast cells in Pb-containing aqueous solutions, the adsorption of Pb ions, and the separation of biomass and supernatant after the required contact time via centrifugation for further analyses.