Uranium sequestration by biofilm-forming bacteria isolated from marine sediment collected from Southern coastal region of India

The present study was aimed at isolation of unique bacteria with radio-tolerance capability, biofilm formation as well as having an ability to sequester uranium. Marine sediment bacteria were isolated and were molecularly characterized. Among the 13 isolates (denoted as MS-1 to MS-13), 9 isolates showed good biofilm-forming ability. The bacterial isolates MS-8 and MS-13 were found to be radio-tolerant, they could survive up to 1000 Gy of radiation dose. Three bacterial strains namely MS-8, MS-11 and MS-13 showed both efficient biofilm formation and uranium sorption ability. These isolates were identified as Exiguobacterium profundum (MS-8), Pseudomonas putida (MS-11), and Bacillus marisflavi (MS-13). Removal of uranium from aqueous solution was studied in batch mode using these bacterial biofilms. The maximum biosorption capability of uranium on MS-8, MS-11 and MS-13 were 45%, 65% and 55% respectively with an initial uranium concentration of 100 mg/L. MS-11 biofilm showed highest U uptake when compared to that of other biofilm-forming strains. In MS-11, U sequestration was up to 88%, when treated with lower U concentrations (1 mg/L to 50 mg/L). The autoclaved biofilm biomasses were able to retain their U sorption capacity proving that the U bioremediation process is mainly a biosorption phenomenon. Further experiments showed ambient temperature and pH range of 3.0–5.0 are optimum physicochemical parameters for maximum uranium removal efficiency by E. profundum MS-8, P. putida MS-11, and B. marisflavi MS-13. FTIR results further confirmed the adsorption of uranium by amino, hydroxyl and amide groups. Among the 13 isolates, overall, P. putida MS-11 showed good biofilm formation and significant U removal at both higher and lower concentrations, with radiation dose tolerance up to 100 Gy. This study specifies the potential application of this bacterium for bioremediation. [Display omitted] •Exiguobacterium profundum, Pseudomonas putida and Bacillus marisflavi were isolated from marine sediment, having good biofilm forming and uranium removal capacity.•All three strains showed substantial radiotolerance in the range of 100–1000 Gy.•P. putida could uptake U at different concentrations with a max. efficiency of 88%.•U removal by live-dead biomass and FTIR analysis showed absorption to be major mechanism involved in uranium removal.•FTIR analysis revealed the involvement of amide, carboxy and phosphate group involvement in uranium sorption.