Microbial reduction of uranium (VI) by designed and indigenous consortium: efficiencies and dynamic behavior

This study was conducted to investigate whether selected microbes with specific functions are comparable or even superior to indigenous consortium (IC) in the microbial uranium reduction process and to detect the immobilization mechanisms of U(VI) with different microbial consortia. Fe(III)-reducing bacteria (FeRB), sulfate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB) were employed to construct a designed consortium (DC), and the IC was obtained from natural samples. The results showed that the uranium-reducing ratio of the DC was higher (52.69 %) than that of the IC (35.65 %) after 34 days, although the uranium removal ratio with IC (98.75 %) was slightly higher than that of the DC (95.75 %). In both the DC and IC groups, uranium was first adsorbed onto the cell surface in the first few days, then sulfate and uranium were reduced simultaneously after depletion of nitrate, and finally labile U species transformed into stable form (e.g UO₂) over time. This work refined our understanding of the construction of highly efficient uranium-reducing microbes and provided insight into strengthening strategies for treating uranium-contaminated groundwater in situ.