Microbial Gold Biosortion and Biomineralization from Aqueous HAuCl4 Solution

The removal of gold (III) from aqueous systems using biosorption and biomineralization by microbial cells was investigated. High levels of gold (III) were removed from a hydrogen tetrachloroaurate (III) solution for 72 h by microbial species, including bacteria, fungi and yeasts. Previously, we reported that the amounts of gold (III) removed through biosorption by gram-positive bacteria, fungi, and yeasts was lower than that by gram-negative bacteria. Candida krusei was able to remove large amounts of gold (III) through biosorption and biomineralization. Interestingly, more gold was removed by atomic reduction than by biosorption. Additionally, we examined time, pH, concentration and other factors affecting gold removal. The rate of gold (III) removal by C. krusei increased for 6 h, and then stabilized, however, the rate of removal increased after 22 h, and reached a second equilibrium after 68 h.