Yuanzineng kexue jishu (Oct 2023)
Biomineralization Kinetics of U(Ⅵ) on Bacillus sp.dwc-2
Abstract
The U(Ⅵ) biomineralization on microorganisms will affect the chemical form and migration behavior of uranium in the environment. However, there are few studies on the kinetic behavior and the relevant mechanism of U(Ⅵ) biomineralization in the growth of microorganisms. In this work, the effects of pH values, sodium glycerophosphate (SGP) and U(Ⅵ) concentration on the biomineralization behavior of U(Ⅵ) in the growth of Bacillus sp.dwc-2, a bacterial strain isolated from a potential (ultra-) low radioactive waste disposal site, and the possible mechanism were investigated. The results indicate that the formation of sodium uranyl phosphate (NaUO2PO4·3H2O) induced by Bacillus sp.dwc-2 as an enzyme-catalyzed reaction in the presence of factors such as pH value, SGP concentration, and initial U(Ⅵ) concentration. The increase of U(Ⅵ) concentration (50-150 mg/L) stimulates the expression of phosphatase activity and phosphate metabolism at the initial stage of biomineralization (0-12 hours), leading to a shift of biomineralization induced by Bacillus sp.dwc-2 at the 12th hour. The increase of the SGP concentration could promote the catalytic reaction rate of phosphatase, and then promote the U(Ⅵ) biomineralization. When the SGP concentration increases from 25 mmol/L to 125 mmol/L, the time of biomineralization induced by Bacillus sp.dwc-2 advances from 24 hours to 12 hours. The phosphatase activity increases rapidly at the initial stage of biomineralization (0-12 hours) under neutral and alkaline conditions, thus promoting the consumption of phosphate and the U(Ⅵ) biomineralization. Especially under alkaline condition, the sediment is transformed into obvious crystal minerals at the 8th hour. The above research results are helpful to better understand the behavior and mechanism of uranium biomineralization, and also have reference value for bioremediation of uranium contaminated environment.
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