Biomineralization of Uranium-Phosphates Fueled by Microbial Degradation of Isosaccharinic Acid (ISA)

Abstract

Geological disposal is the globally preferred long-term solution for higher activity radioactive wastes (HAW) including intermediate level waste (ILW). In a cementitious disposal system, cellulosic waste items present in ILW may undergo alkaline hydrolysis, producing significant quantities of isosaccharinic acid (ISA), a chelating agent for radionuclides. Although microbial degradation of ISA has been demonstrated, its impact upon the fate of radionuclides in a geological disposal facility (GDF) is a topic of ongoing research. This study investigates the fate of U­(VI) in pH-neutral, anoxic, microbial enrichment cultures, approaching conditions similar to the far field of a GDF, containing ISA as the sole carbon source, and elevated phosphate concentrations, incubated both (i) under fermentation and (ii) Fe­(III)-reducing conditions. In the ISA-fermentation experiment, U­(VI) was precipitated as insoluble U­(VI)-phosphates, whereas under Fe­(III)-reducing conditions, the majority of the uranium was precipitated as reduced U­(IV)-phosphates, presumably formed via enzymatic reduction mediated by metal-reducing bacteria, including Geobacter species. Overall, this suggests the establishment of a microbially mediated “bio-barrier” extending into the far field geosphere surrounding a GDF is possible and this biobarrier has the potential to evolve in response to GDF evolution and can have a controlling impact on the fate of radionuclides.

High-energy resolution X-ray spectroscopy at actinide M4,5 and ligand K edges: what we know, what we want to know, and what we can know

“…The actinide M 4,5 HERFD-XANES method gives the opportunity to fingerprint the oxidation state of the actinidecontaining materials. The first U M 4 experiment has been done on the mixed uranium oxides 3 , which was followed by several other Please do not adjust margins Please do not adjust margins studies on the chemical state verification in actinide systems 3,6,9,12,[60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77] . Fig.…”

“…For example, Pu(IV) species are considered less mobile than species with other oxidation states because of their solubility. Therefore, the HERFD method at the An M 4,5 edges is the only one for the moment, which allows us to fingerprint the mixtures of actinide oxidation states with high precision (as low as the 2% contribution) in environmentally relevant systems 65,67,75,80,81 .…”

Biomolecular Insights into Extracellular Pollutant Reduction Pathways of Geobacter sulfurreducens Using a Base Editor System

“…Geobacter species, as the predominant microorganisms for Fe­(III) and Mn­(IV) reduction in the natural environment, fill key niches in the soils, sediments, and groundwater. − In addition, they possess powerful abilities in radionuclide immobilization, toxic metal detoxification, and electrical interaction with solid electrodes or minerals. − The versatile sensory networks, respiratory chains, and metabolic reactions further strengthen their ability to adapt to a diverse and variable environment. − All of these favorable features make them important players in elemental biogeochemical cycling and environmental bioremediation. However, the highly complicated, dynamic pathways of sensing, metabolism, and respiration also severely hinder a deep understanding and effective engineering of these bacteria.…”

Bioremediation of Uranium- and Nitrate-Contaminated Groundwater after the In Situ Leach Mining of Uranium

“…In recent decades, a number of biotechnologies, including biomineralization [15][16][17], bioreduction [18][19][20][21], biosorption [22][23][24][25], and bioaccumulation [26], have been proposed in order to immobilize uranium in contaminated groundwater. Among the uranium bioremediation techniques available, uranium bioreduction has been studied extensively, where U(VI) is reduced to U(IV) by a variety of bacteria.…”