New “green” biotechnical concepts for the recovery of metals from primary and secondary resources

Novel environmental-friendly technologies are required in order to secure the demand of industrial relevant metals, covering the fields of exploitation, beneficiation and recycling of rare elements.
Nature itself offers promising approaches in these fields. In our group we develop bio-based technologies for extracting, treating and recycling metals such as copper or rare earths using microbes, microbial metabolites or biomolecules. The presentation gives an overview of current research activities that are performed in our group.
Natural processes such as microbial weathering, biomineralization, or biosorption are highly attractive for biotechnological applications that intend the recovery of metals from primary and secondary resources.
Currently applied bioleaching concepts use acidophilic bacteria such as Acidithiobacillus ferrooxidans for the extraction of metals from sulfidic ores. This approach is already used for the extraction of copper especially in ores with low metal content. Other concepts use metabolic products from microorganisms for indirect bioleaching processes. For example, in our group we investigate the use of heterotrophic bacteria for the extraction of strategic relevant elements such as copper and Rare Earth Elements from different sources.
Biosorption uses the metal binding capabilities of biomass or biomolecules for the recovery of metals from solutions. Such compounds can be immobilized on materials to construct metal selective filter materials. These materials enable an efficient removal of specific metals, are relatively cheap, and can be regenerated. In our group we use bacterial surface layer proteins (S-layers) for the construction of metal selective biocomposites. In other projects we select metal binding peptides using phage surface display technology. In a third approach we use metabolic products, e.g. metallophores, as complexing agents.
In conclusion, in combination with established physical and chemical processes, such biotechnological approaches have a high potential to improve metal beneficiation and recycling and contribute to environmentally friendly and sustainable processes.