Biohydrometallurgical processes are increasingly perceived as viable solutions to the general problem of decreasing ore qualities and resource complexity. Bioleaching by autotrophic bacteria such as Acidithiobacillus is already well established on an industrial scale since decades. But also apart from acid production, microbes have developed a multitude of mechanisms for the interaction with metallic compounds, e.g. metallophores, surface structures and exopolymers. Some of these structures have a surprising element specificity, which makes them promising candidates for biological process development.
We have screened our extensive microbial strain collection (>30 000 strains) for microorganisms that are able to interact with dissolved metal compounds and surfaces, respectively. Several hundred candidates for bio-leaching, - accumulation, and - sorption of a variety of target metals have been identified. Based on these organisms, we implemented different process concepts for metal enrichment. A biomass-based method for the selective recovery of Scandium (Sc) from a genuine sulfuric ore leach will be presented. Enrichment factors of > 400 were achieved for this element in a single step procedure, with yields of more than 80%. Besides being integrated in an overall REE bioraffination scheme, biological Sc-recovery could serve as an “on-top” module in processes where Sc does not constitute an economical target by itself. In these cases, a valuable side-product could be recovered with comparatively little effort.