Engineered Protein Materials for Selective Binding of Strategic Metals | AIChE

Engineered Protein Materials for Selective Binding of Strategic Metals

Authors 

Charrier, M. - Presenter, Joint BioEnergy Institute
Ajo-Franklin, C., Lawrence Berkeley National Laboratory
The ability to extract dilute strategic metals or critical metals, such as rare earth elements, from complex solutions could improve the economics of waste streams or allow for mining of natural resources. However, current technologies have proven insufficiently selective, insufficiently robust, or too expensive to be widely adopted by industry. To meet this need, we engineered thermostable surface-layer (S-layer) proteins to act as a low-cost, targeted metal adsorbent. The SbsB S-layer protein from Geobacillus stearothermophilus was fused to either Zn2+ or Gd3+ metal binding domains and heterologously expressed in Escherichia coli. By performing the outgrowth at a low temperature, we developed a new, simpler method of expressing and purifying recombinant SbsB that increases the yield 10-fold over previous methods. These engineered protein materials are capable of binding more Zn2+ or Gd3+ at 25°C and 40°C than their native counterparts, and can selectively extract Zn2+ or Gd3+ in the presence of 106 higher concentrations of competing ions. The ability for this material to remain intact and functional at elevated temperatures and salinity demonstrates its robustness to environmental conditions. Put together, these results show that engineered S-layer proteins are a robust, selective, low-cost material for strategic metal extraction.