Enhancement of Au Dissolution by Microorganisms Using an Accelerating Cathode Reaction

A Chromobacterium violaceum (C. violaceum) strain that produces cyanide was used to dissolve Au. In this bacterial Au dissolution process, decreased dissolved oxygen concentration in the bacterial medium significantly inhibits Au dissolution. Although aeration is effective in increasing the level of dissolved oxygen in the bacterial medium, it is not effective in increasing Au dissolution during the growth phase of the bacteria because of the latter's high respiratory consumption of oxygen. The present study investigated the utility of H(2)O(2), rather than aeration, for increasing dissolved oxygen concentrations in bacterial growth medium. It was anticipated that the stronger oxidation reagent would increase Au dissolution by accelerating the cathode reaction during the bacterial growth phase. In fact, the addition of H(2)O(2) to the bacterial culture increased dissolved oxygen concentrations in the growth phase and also drastically increased the dissolution rate of Au. Electrochemical measurements indicated that H(2)O(2) addition to the bacterial medium accelerated the cathode reaction and thus enhanced Au dissolution by this biological process.