Non-reductive biomineralization of U(VI)-phosphate minerals through the activities of microbial phytases
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In environments characterized by low pH and/or high nitrate, the biomineralization of U(VI)-phosphate minerals represents a uniquely suited bioremediation method involving microbially-mediated hydrolysis of organophosphates coupled to a chemical precipitation of sparingly soluble U(VI)-phosphate minerals. In this study, the ability of natural microbial phytases to hydrolyze phytate, a naturally-occurring and abundant organophosphate, and precipitate uranium-phosphate minerals was investigated through a combination of sediment microcosms, soil slurries, and pure culture studies. In this study, biomineralization of U(VI)-phosphate minerals promoted by addition of glycerol-2-phosphate was shown to outcompete bioreduction in anaerobically-maintained sediment microcosms containing contaminated soils. Addition of phytate to aerobic soils slurries containing ORFRC soils also resulted in significant production of inorganic phosphate, and two microorganisms that efficiently hydrolyze phytate were isolated from these experiments. Overall, the results of this study demonstrate phytate hydrolysis by subsurface microorganisms coupled to precipitation of U(VI)-phosphate minerals for the first time, suggesting that phytate may represent an ideal organophosphate to promote this process.