Abstract
Uranium is one of the most important metal resources, and the technology for the recovery of uranyl ions (UO22+) from aqueous solutions is required to ensure a semi-permanent supply of uranium. The NikR protein is a Ni2+-dependent transcriptional repressor of the nickel-ion uptake system in Escherichia coli, but its mutant protein (NikRm) is able to selectively bind uranyl ions in the interface of the two monomers. In this study, NikRm protein with ability to adsorb uranyl ions was displayed on the cell surface of Saccharomyces cerevisiae. To perform the binding of metal ions in the interface of the two monomers, two metal-binding domains (MBDs) of NikRm were tandemly fused via linker peptides and displayed on the yeast cell surface by fusion with the cell wall-anchoring domain of yeast α-agglutinin. The NikRm-MBD-displaying yeast cells with particular linker lengths showed the enhanced adsorption of uranyl ions in comparison to the control strain. By treating cells with citrate buffer (pH 4.3), the uranyl ions adsorbed on the cell surface were recovered. Our results indicate that the adsorption system by yeast cells displaying tandemly fused MBDs of NikRm is effective for simple and concentrated recovery of uranyl ions, as well as adsorption of uranyl ions.
Highlights
Uranium, an element from the actinide series, is one of the heaviest elements naturally occurring on earth, and is one of the most important metal resources used as nuclear fuel
The constructed multi-copy plasmids contain the fusion gene composed of the glyceraldehydes-3-phosphate dehydrogenase (GAPDH) promoter, secretion signal of glucoamylase from Rhizopus oryzae, metal-binding domains (MBDs) of NikRm, linker 1, MBD of NikRm, linker 2, FLAG-tag, and C-terminal half of -agglutinin as the cell-wall anchoring domain in this order (Figure 1)
Yeast cells harboring the constructed plasmids showed green fluorescence derived from fluorescent antibodies binding on the cell surface, and negative control cells harboring the pULD1-s plasmid for the display of only a strep-tag showed no fluorescence. These results indicate that tandemly fused MBDs of NikRm with different linker lengths were successfully displayed on the yeast cell surface
Summary
An element from the actinide series, is one of the heaviest elements naturally occurring on earth, and is one of the most important metal resources used as nuclear fuel. Cell-surface adsorption by yeast cell surface engineering, which enables the display of functional proteins by fusion with cell wall-anchoring proteins, is an advantageous strategy [1,2,3,4,5] The benefits of this technique include the capability to use mild treatment for adsorption/recovery, the easy recovery of metal ions from cells without cell breakage, and the reusability of the yeasts used in the adsorption/recovery. We attempted to construct a cell-surface-engineered yeast with uranyl ions-binding capabilities as a recovery system for uranium from aqueous solutions such as seawater. The adsorption and recovery of uranyl ions by the yeasts displaying tandemly fused MBDs of NikRm were evaluated, and the applicability of cell-surface adsorption to the collection of uranyl ions is discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
