Microbial Biosorbent with Functionalized Curli for Efficient Recovery of Rare-Earth Elements

Recovery of rare-earth elements (REEs) from REE-containing waste streams is vital for resource sustainable supply and environmental protection. Microbial biosorption by utilizing lanthanide binding tags (LBTs) immobilized on the cell surface for selectively capturing REEs offers an appealing option, yet this technology is currently restricted by the limited adsorption capacity. Here, we report a curli display strategy to drastically raise the extracellular LBT loading of the engineered cells by using Escherichia coli as a model. The bacteria with abundant self-assembled LBT-loaded curli exhibited over 2-fold higher terbium adsorption capacity than the control with cell surface-displayed proteins. It rivals the abiotic sorbents in adsorption capacity but offers much higher selectivity. Moreover, the biosorbent still retained 94% adsorption capacity after six consecutive sorption–desorption cycles and was successfully used to recover REEs from simulated acid mine drainage. A similar strategy of curli-displayed proteins for metal binding was also applied to the recovery of gold ions from water, implying that such an engineered biosorbent may serve as a universal biological platform for metal recovery from complicated water matrices.