Microbial recovery of gold from neutral and acidic solutions by the baker's yeast Saccharomyces cerevisiae

An environmentally friendly method using the baker's yeast Saccharomyces cerevisiae was developed to recover soluble Au(III) from neutral and acidic solutions at room temperature. Resting cells of S. cerevisiae were able to reduce aqueous Au(III) ions in HAuCl4 solution to metallic Au(0) at pH 7.0 within 120 min when formate was provided as the electron donor under anaerobic conditions. Gold nanoparticles were deposited on the cell surface of S. cerevisiae. The S. cerevisiae cells were also applicable to a bio-material for adsorbing aqueous Au(III) ions from HAuCl4 solution at pH 1.0 under air atmosphere. When processing the aqua regia leachate of electronic waste (Central Processing Units, CPU), the S. cerevisiae cells were able to rapidly and selectively collect aqueous Au(III) ions from the aqua regia leachate at pH 1.2 within 10 min. Our proposed microbial methods enable the rapid and efficient recovery of gold over the pH range 1.0 to 7.0.