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Influence of calcium on microbial reduction of solid phase uranium(VI)
Author(s) -
Liu Chongxuan,
Jeon ByongHun,
Zachara John M.,
Wang Zheming
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21357
Subject(s) - chemistry , dissolution , shewanella oneidensis , uranyl , aqueous solution , solubility , nuclear chemistry , calcium , shewanella putrefaciens , inorganic chemistry , bicarbonate , bacteria , organic chemistry , ion , genetics , biology
The effect of calcium on the dissolution and microbial reduction of a representative solid phase uranyl [U(VI)], sodium boltwoodite (NaUO 2 SiO 3 OH · 1.5H 2 O), was investigated to evaluate the rate‐limiting step of microbial reduction of the solid phase U(VI). Microbial reduction experiments were performed in a culture of a dissimilatory metal‐reducing bacterium (DMRB), Shewanella oneidensis strain MR‐1, in a bicarbonate medium with lactate as electron donor at pH 6.8 buffered with PIPES. Calcium increased the rate of Na‐boltwoodite dissolution and U(VI) bioavailability by increasing its solubility through the formation of a ternary aqueous calcium‐uranyl‐carbonate species. The ternary species, however, decreased the rates of microbial reduction of aqueous U(VI). Laser‐induced fluorescence spectroscopy (LIFS) and transmission electron microscopy (TEM) collectively revealed that microbial reduction of solid phase U(VI) was a sequentially coupled process of Na‐boltwoodite dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) to U(IV) that accumulated on bacterial surfaces/periplasm. Under studied experimental conditions, the overall rate of microbial reduction of solid phase U(VI) was limited by U(VI) dissolution reactions in solutions without calcium and limited by microbial reduction in solutions with calcium. Generally, the overall rate of microbial reduction of solid phase U(VI) was determined by the coupling of solid phase U(VI) dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) that were all affected by calcium. Biotechnol. Bioneg. 2007;97: 1415–1422. © 2007 Wiley Periodicals, Inc.