Possible Role of the Biosurfactant-Producing and Fe-S-Oxidizing Bacterium in Silicate and Sulfide Bioflotation Processes

A biosurfactant-producing-and Fe-S-oxidizing bacterium, namely Pseudoclavibacter sp. strain SKC/XLW-1, was studied in an attempt to seek more benign alternatives for the replacement of relatively toxic chemical reagents in the flotation of silicate and sulfide minerals. Our study showed that Pseudoclavibacter sp. SKC/XLW-1 was capable of yielding biosurfactants as evidenced by a decrease in the surface tension of the solutions and an increase of the contact angle of the pyrite or silica surfaces as a function of time. This bacterial strain was also observed to promote the oxidation of pyrite, thus generating Fe-oxides as well as sulfuric acid as indicated by a decline of the solution pH and FTIR analysis. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) observations of the silica-or pyrite-bacterial cell complexes revealed the presence of bacterial cell aggregation along with silica or pyrite, where silica or pyrite particles become embedded in the biofilm matrix. It is suggested from this study that the bacterium Pseudoclavibacter sp. SKC/XLW-1 could potentially be applicable as the flotation bioreagents (collector, frother or depressant) for both silicate and sulfide flotation processes.