Intracellular recovery of gold by microbial reduction of AuCl4− ions using the anaerobic bacterium Shewanella algae

Microbial reduction and intracellular precipitation of gold was achieved at 25 DDGC and pH 7 by using the mesophilic anaerobic bacterium Shewanella algae with H2 as the electron donor. The reductive precipitation of gold by S. algae was a fast process: 0DDT1-1 mol/m3AuCl4-ions were completely reduced to insoluble gold within 30 min. The biogenic precipitates were crystalline gold nanoparticles of 10-20 nm present in the periplasmic space. The reducing power of S. algae at 3DDT2x1015cells/m3and 25DDGC was comparable to that of aqueous citric acid solution (chemical reductant) at 20 mol/m3and 50DDGC. The intracellular recovery of gold is potentially attractive as an environmentally friendly alternative to conventional methods.