Biogenesis of thiosulfate in microorganisms and its applications for sustainable metal extraction

Thiosulfate is a lixiviant with potential applications for extraction of precious metals with lower environmental impact. As an alternative leaching reagent to cyanide, thiosulfate has promising gold extraction efficiency with much lower risk to operators and the environment. Thiosulfate is often produced at high temperatures via processes utilizing sulfide or sulfur and an oxidant. However, certain microorganisms can produce thiosulfate as the final product of their metabolism. This represents potential for lower emissions and costs in the manufacture of gold leaching reagents. Biotechnological applications of these processes have not been reported in the past and need to be investigated in depth. This review serves as a study of microorganisms to collect and analyze the reported species for potential utilization of biogenic thiosulfate in industrial applications, with a specific focus on precious metals extraction. Bacteria were identified and compared with respect to thiosulfate producing ability, feasibility for the mining industry, and cost of substrates. The future applications of biogenic thiosulfate and further direction of research on the topic have been identified.