Radiotolerance of phosphatases of a Serratia sp. : potential for the use of this organism in the biomineralization of wastes containing radionuclides

Paterson-Beedle, M. and Jeong, B. C. and Lee, C.H. and Jee, K. Y. and Kim, W.H. and Renshaw, J. C. and Macaskie, L. E. (2012) Radiotolerance of phosphatases of a Serratia sp. : potential for the use of this organism in the biomineralization of wastes containing radionuclides. Biotechnology and Bioengineering, 109 (8). pp. 1937-1946. ISSN 0006-3592 (https://doi.org/10.1002/bit.24467)

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Abstract

Aqueous wastes from nuclear fuel reprocessing present special problems of radiotoxicity of the active species. Cells of Serratia sp. were found previously to accumulate high levels of hydrogen uranyl phosphate (HUP) via the activity of a phosphatase enzyme. Uranium is of relatively low radiotoxicity whereas radionuclide fission products such as 90Sr and 137Cs are highly radiotoxic. These radionuclides can be co-crystallized, held within the bio-HUP "host" lattice on the bacterial cells and thereby removed from contaminated solution, depending on continued phosphatase activity. Radiostability tests using a commercial 60Co γ-source showed that while cell viability and activity of purified phosphatase were lost within a few hours on irradiation, whole-cell phosphatase retained 80% of the initial activity, even after loss of cell culturability, which was increased to 100% by the incorporation of mercaptoethanol as an example radioprotectant, beyond an accumulated dose of >1.3MGy. Using this co-crystallization approach (without mercaptoethanol) 137Cs + and 85Sr 2+ were removed from a simulated waste selectively against a 33-fold excess of Na +.

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