Uranium speciation and distribution in Shewanella putrefaciens and anaerobic granular sludge in the uranium immobilization process

The uranium (U) in Shewanella putrefaciens (S. putrefaciens) and anaerobic granular sludge (AnGS) were fractionated, and the contents and forms of U in each fraction were investigated. The functional groups of microorganisms for U binding and the deposition of U in microbial aggregates were also analyzed. Four main approaches were found involved in U immobilization, including biosorption/complexation by microbial cells and their extracellular polymeric substances (EPS), non-reductive biomineralization, bioreduction and intracellular accumulation. Results show that non-reductive biomineralization was found to be dominated in the U(VI) immobilization process. Besides, the contribution of EPS to U removal could not be ignored.