Uranium adsorption by extracellular polymeric substances from Desulfovibrio vulgaris UR1: Extraction optimization and binding mechanisms

Extracellular polymeric substances (EPSs) play a crucial role in the microbial remediation of groundwater contaminated with radioactive uranium. In this study, EPSs were extracted from Desulfovibrio vulgaris UR1, a highly efficient uranium-reducing bacterium isolated from a uranium mining area, using six different treatment methods: heating, ultrasonication, centrifugation, pH adjustment, the addition of EDTA-2Na, and the use of a cation exchange resin. The physicochemical properties of the extracted EPSs were characterized through adsorption experiments and spectroscopic analyses. Compared with the other methods, heating at 318 K resulted in the highest EPS extraction amount of 63.36 mg·g –1 dry cell, while the cell viability was maintained above 80%. The extraction method significantly influenced the contents of protein and polysaccharide in the EPSs. EPSs obtained by heating at 318 K exhibited a uranium adsorption capacity of up to 454.85 mg·g –1 , with carboxyl and hydroxyl groups in proteins identified as the primary functional groups responsible for adsorption. This work investigated the extraction methods and uranium adsorption performance of EPSs from Desulfovibrio vulgaris UR1, contributing to a better understanding of the adsorption mechanisms and resistance strategies of microorganisms in anaerobic groundwater environments contaminated with uranium.