Removal of U(VI) from aqueous solutions using Shewanella sp RCRI7, isolated from Qurugol Lake in Iran

Abstract

Isolation, genotypic and phenotypic characterization of an aqueous bacterium, Shewanella sp RCRI7, from Qurugl Lake in Iran and uranium removal from aqueous solutions using the isolate is described. Based on 16S rRNA gene sequence analysis and phylogenetic tree, strain RCRI7T falls into genus Shewanella. Closely related type strains include Shewanella xiamenensis S4(T) KJ542801, Shewanella profunda DSM15900(T) FR733713, Shewanella putrefaciens LMG 26268(T) X81623 and Shewanella oneidensis MR-1(T) AE014299. Anaerobic incubation of the bacteria in the presence of U(VI) led to uranium removal from the solution and formation of a black precipitate. Analysis of the precipitate using UV-vis confirmed the reduction of U(VI) to U(IV). The effects of pH, temperature, U(VI) concentration and cell density on uranium removal were elucidated. The maximum uranium removal was 97%. As a conclusion, the findings revealed the ability of the local strain RCRI7 for U(VI) bioreduction as an effective bacterium for uranium immobilization.