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In this paper we report an approach for the structural analysis of mineral-collector interfaces of (bio) flotation systems by means of attenuated total reflection Fourier-transform infrared spectroscopy (ATR FT-IR). The extraction of rare earth metals from electronic waste materials is an important challenge for the recycling industry. In a current project bacteriophage are used as biocollectors to develop a bioflotation model system for the separation of lanthanum phosphate doped with cerium and terbium (LaPO4:Ce3+,Tb3+) from mixed fluorescent phosphors. As an initial analytical concept fluorescence microscopy was successfully applied to investigate particles of spent fluorescent lamp powders and to visualize the bacteriophage on the surface of the waste material. However, due to the restrictions of this technique we are not able to identify the molecular interactions of the bacteriophage with the recycled material. ATR FT-IR was found to be an effective tool to detect the major coat protein of the bacteriophage biocollectors on the surface of the LaPO4:Ce3+,Tb3+ and sense their specific bonding interaction opening the gates for the high level chemical characterization of the interface.

Phage display for discovery of specific binding peptides is nowadays widely used in the pharmaceutical industry and in many biotechnological applications. Using state-of-the-art cloning techniques we developed an easy-to-use cloning and expression system, allowing the fast production of identified peptides while avoiding proteolysis.

The development of effective and ecofriendly processes for the recovery of critical elements poses a challenge for scientists all over the world. A novel approach is the generation of highly specific peptides that bind with high affinity to individual elements of interest. The peptides are selected by phage surface display (PSD) technology. In this study, PSD technology has been applied in two different approaches. The focus of the first approach was the identification of peptides that bind specifically to special particles of interest that are part of electronic scrap aiming towards the development of new recycling processes. In the second approach, metal ion binding peptides were isolated via PSD to use them for the targeted removal and enrichment of these elements from complex leaching solutions or from industrial waters. To address the economic production of peptides, the development of a new expression system is also part of this study.

Gallium (Ga) is a critical element for the electronic industry, however, its long-term supply is not assured. Thus, the recovery of Ga from industrial wastewaters is important. Selective sorption is a recommended technology for the recovery of Ga from industrial wastewaters, however, selective sorbents are elusive. Desferrioxamine B (DFOB), a hydroxomate siderophore that is known to be highly selective towards Fe3+, is tested for its ability to complex Ga. This study demonstrated that DFOB forms 1:1 complex with Ga and the maximum Qe-Ga is 124.4 mg of Ga complexed per g of DFOB. Further, the complexation mechanism of Ga3+ and Fe3+ with DFOB is similar, as indicated by NMR, suggesting that the selectivity of DFOB towards Fe3+ will be extended to Ga3+ as well. Thus, DFOB seems to be a suitable candidate for the sorption of Ga from industrial wastewaters.

Marinobacter sp. DS40M6 produces the siderophores marinobactins, which are amphiphilic and contain hydroxamate functional groups responsible for a strong complexation of iron(III). First tests about growth and production conditions showed on the one hand a high rate for both growth of bacteria and siderophore production at 25°C. The pH value, on the other hand, demonstrated a contrary effect, thus the optimal pH 7.0 for growth was not the most efficient pH value for siderophore production.

Phage surface display technology is a useful tool for the identification of biosorptive peptides. In this work it is used for the identification of cobalt, nickel and gallium binding peptides. We present methods for the enrichment of metal ion binding bacteriophage clones from a commercial phage display library. Metal ion selective peptides are suitable to separate as well as concentrate cobalt and nickel from copper black shale leaching products (EcoMetals project) and gallium from industrial waste waters (EcoGaIn project). In contrast to common capture methods of specific binding phage for solid materials the ionic species have to be immobilized prior to the bio-panning procedure. This was realized by chemical complexation of the metal ions using commercial complexing agents on porous matrices. Moreover, an option to harvest non elutable strong binding phage is proposed.

Most bacteria and all archaea possess as outermost cell envelope so called surface-layers (S-layers). These layers were formed by self-assembling proteins having a number of habitat depending interesting intrinsic properties. As example, S-layers from bacterial isolates recovered from heavy metal contaminated environments have outstanding metal binding properties and are highly stable. Thus they selectively bind several metals with different affinity. For using S-layer proteins for metal bioremediation and recycling three aspects of the metal-interactions with S-layer proteins must be taken into account. First, S-layers possess different functionalities, e.g. carboxyl, phosphoryl groups, binding toxic metals and metalloids, like U(VI) and As(V), nonspecifically depending on pH. Second, precious metals like Au and Pd are likewise nonspecifically bound to functional groups, but presumably covalently, making the binding irreversible. Third, intrinsic specifically bound metals, e.g. Ca2+, are needed for native protein folding, self-assembly, and the formation of highly-ordered lattices. Their binding sites also allow selective binding of chemical-equal elements including the trivalent rare earth elements, possessing comparable ionic radii. Thus this study combines older and recently generated results regarding the metal dependent binding behavior of the S-layer proteins. It enables the development of biohybrid materials for the separation, removal or recovery of strategic relevant metals from natural occurring or industrial waste waters using pH-value as regulating parameter for selective metal binding and also conceivably release.