V(Ⅴ)reduction by iron minerals combined with Shewanella oneidensis MR-1 and its mechanism
Minerals in collaboration with microorganisms can reduce highly toxic V(Ⅴ)to less toxic and less mobile V(Ⅳ),thereby achieving the purpose of vanadium pollution control.Using Shewanella oneidensis MR-1 as the test strain and pyrite,siderite,and mackinawite as the test iron minerals,this research investigated the characteristics of V(Ⅴ)reduction by iron minerals combined with microorganisms.Meanwhile,the factors affecting V(Ⅴ)reduction were examined,and the impact of mackinawite combined with S.oneidensis MR-1on the reduction of V(Ⅴ)regarding intracellular enzyme activity,extracellular polymeric substances(EPS),and electron transfer were determined.The results showed that all three iron minerals promoted the reduction of V(Ⅴ)by S.oneidensis MR-1,with mackinawite being the most effective,increasing the reduction rate of V(Ⅴ)from 80.84％in the control group to 95.54％.The reduction rate of V(Ⅴ)by mackinawite in conjunction with S.oneidensis MR-1 was inversely proportional to the initial V(Ⅴ)concentration and pH value,and directly proportional to the amount of added mineral and inoculated bacteria.The addition of mackinawite enhanced the contents of intracellular nitrate reductase(NAR),nitrite reductase(NIR),reduced nicotinamide adenine dinucleotide(NADH)and ATP,increased the contents of proteins,polysaccharides and nucleic acids in EPS,and enhanced electron transfer capability,thereby promoting the bioreduction of V(Ⅴ).Scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDS)and X-ray photoelectron spectroscopy(XPS)showed that mackinawite promoted the reduction of V(Ⅴ)to insoluble V(Ⅳ)by S.oneidensis MR-1,forming precipitates that accumulated around the bacterial cells.
V(Ⅴ)Shewanella oneidensis MR-1mackinawitenitrite reductaseextracellular polymeric substanceelectron transfer
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