Harnessing a Genetically Engineered Self-Assembling Protein Biosorbent for Efficient and Selective Rare Earth Element Recovery

The global demand for rare earth elements (REEs) has surged due to their critical role in high-tech and clean energy applications. However, conventional extraction from mineral ores is resource-intensive and environmentally harmful. Recovering REEs from low-grade secondary resources offers a sustainable alternative but remains a significant challenge. Here, we constructed a novel protein-based biosorbent, PCI-Hans-LanM, by genetically fusing the Hansschlegelia quercus lanmodulin (Hans-LanM) to protein crystalline inclusions (PCIs) for in vivo one-pot immobilization in Escherichia coli, eliminating the need for complex purification and carrier synthesis. The PCI-Hans-LanM exhibited rapid adsorption and desorption kinetics, with the adsorption capacity ranging from 157.6 to 197.7 μmol-REE/g-sorbent (14.0 to 34.6 mg-REE/g-sorbent) for various REEs. The biosorbent could selectively capture REEs against over 2000-fold excess non-REEs, and its performance was largely maintained over 10 consecutive adsorption-desorption cycles of reuse and during one-month storage under different conditions. More importantly, the PCI-Hans-LanM enabled efficient and selective recovery of REEs from the leachate of coal fly ash, a low-grade industrial waste source, yielding a 433-fold increase in REE purity. This study presents the potential of leveraging advanced bioengineering strategies to develop high-performance biosorbents for sustainable REE recovery from waste streams, contributing to a circular economy and a diversified supply chain.