Recovery of Rare Earth Elements from Low-Grade Feedstock Leachates Using Engineered Bacteria

The use of biomass for adsorption
of rare earth elements (REEs)
has been the subject of many recent investigations. However, REE adsorption
by bioengineered systems has been scarcely documented, and rarely
tested with complex natural feedstocks. Herein, we engineered E. coli cells for enhanced cell surface-mediated extraction
of REEs by functionalizing the OmpA protein with 16 copies of a lanthanide
binding tag (LBT). Through biosorption experiments conducted with
leachates from metal-mine tailings and rare earth deposits, we show
that functionalization of the cell surface with LBT yielded several
notable advantages over the nonengineered control. First, the efficiency
of REE adsorption from all leachates was enhanced as indicated by
a 2–10-fold increase in distribution coefficients for individual
REEs. Second, the relative affinity of the cell surface for REEs was
increased over all non-REEs except Cu. Third, LBT-display systematically
enhanced the affinity of the cell surface for REEs as a function of
decreasing atomic radius, providing a means to separate high value
heavy REEs from more common light REEs. Together, our results demonstrate
that REE biosorption of high efficiency and selectivity from low-grade
feedstocks can be achieved by engineering the native bacterial surface.