title: Toxicity of ionic liquids to Clostridium sp. and effects on uranium biosorption.
abstract: As green solvents ionic liquids (ILs) show high potential in nuclear industry for extraction and purification of actinides. However, to date relatively little information has been gained on ILs application in microbial processes, for example biosorption of radionuclides. We investigated the effects of three ILs, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), N-ethylpyridinium trifluoroacetate (EtPyCF3COO) and N-ethylpyridinium tetrafluoroborate (EtPyBF4) on the growth and biosorption of uranium by Clostridium sp. The ILs affected the growth of the bacterium as evidenced by decreases in optical density, total gas production, and organic acids production from glucose metabolism. The IC50-48h of three ILs decreased in the order of BMIMPF6 (8.26mM)>EtPyBF4 (7.04mM)>EtPyCF3COO (4.05mM). Uranium biosorption by the bacterial cells decreased by 75% in the presence of 1% (v/v) BMIMPF6 and by about 90% with 1% (v/v) EtPyBF4 or EtPyCF3COO, in comparison to the control without ILs. The diminished biosorption may be attributed to the membrane damages induced by EtPyBF4 and EtPyCF3COO, which can be visualized by Transmission Electron Microscope (TEM) analysis. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed the accumulation of uranium inside peripheral membrane of the cells exposed to uranium alone or with BMIMPF6, while little or no accumulation was observed in the presence of EtPyBF4 and EtPyCF3COO. These results imply that potential toxicity of ILs towards microorganisms is a particularly important issue in limiting its biotechnological applications.
authors: College of Environmental Science and Engineering, Nankai University, Tianjin, China 300071; Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ 07104 USA. Electronic address: zhangchengdong@nankai.edu.cn.
authors: C
authors: C
authors: Zhang
authors: Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ 07104 USA.
authors: S V
authors: SV
authors: Malhotra
authors: Environmental Sciences Department, Brookhaven National Laboratory, Upton, NY 11973 USA; Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, Pohang, 790-784 South Korea.
authors: A J
authors: AJ
authors: Francis
mesh_terms: D000042:Absorption; D003013:Clostridium / Q000187:drug effects* / Q000378:metabolism; D052578:Ionic Liquids / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D013052:Spectrometry, X-Ray Emission; D014501:Uranium / Q000378:metabolism*
chemical_list: D052578:Ionic Liquids; D014501:Uranium
keywords: Biosorption; Clostridium sp.; Ionic liquids; Toxicity; Uranium