Lanthanide ion-binding peptides as a natural solution for rare earth element separation and recovery

Due to their special properties, lanthanides (Ln) are of utmost importance in the current technological era – both in the present and in the future. Besides their indispensable contribution to high-tech products, they are also increasingly used in environmental technology. In recent years, attention has turned to alternative solutions such as the recycling of Ln from end-of-life products or wastewater from industry and mining. However, these contain only low concentrations of rare earth elements (REE), which are additionally very similar in their chemical and physical properties, so that the separation is cost-intensive and an efficient recovery still far away. Research and development of new recycling processes should change this and enable a cost-effective and environmentally friendly separation from electronic scrap and wastewater in order to conserve primary resources and make us independent of them. We are researching a promising approach for such a novel recycling technology and try to solve the separation problem using selective peptides. Immobilized on a suitable carrier material, this kind of biohybrid separation platform can finally be used for REE recovery.
By combining phage surface display technique with next generation sequencing and running parallel biopannings on target ion and immobilization material, we were able to enrich and identify peptide sequences showing an affinity for the europium ion (Eu3+). Most enriched and repetitive peptide variants in several biopannings with different elution types were characterized by time-resolved laser fluorescence spectroscopy and isothermal titration calorimetry with respect to their Eu3+ affinity. Calmodulin’s EF-hand 4 peptide serves as a reference system.