Effect of Zn on Fe(II) oxidation and nitrate reduction by a denitrifying bacterium, Pseudomonas stutzeri LS-2

Abstract:

[Objective] The aim of this study was to investigate the effect of Zn on the Fe(II)-driven denitrification and mineralization by a denitrifying bacterium, Pseudomonas stutzeri LS-2 under neutral anaerobic conditions. The result will extend our knowledge of microbial Fe(II)-driven denitrification and its environmental behavior under anaerobic conditions. [Methods] We designed the microbial driven Fe(II) oxidation with a series of Zn(II) concentration, detected the rates of Fe(II) oxidation and nitrate reduction, and characterized the mineralogy under different conditions.[Results] The activity of the Fe(II)-oxidizing denitrifying culture was affected by the presence of Zn. The results showed that the presence of Zn inhibited the rates of nitrate reduction and Fe(II) oxidation. A low inhibition was observed at initial concentrations of Zn(II) from 0.15 to 2 mmol/L. When Zn(II) was supplemented up to 4 mmol/L, the higher inhibition was observed. In addition, the minerals during nitrate-reducing Fe(II) oxidation can efficiently remove the supplemented Zn(II), including co-precipitation, sorption and isomorphous substitution. The nitrate-reducing Fe(II) oxidation resulted in the formation of a mixture of Fe(III) minerals in the presence of different Zn(II) concentrations. The use of low Zn(II) concentration cultures enhanced the formation of lepidocrocite, while the higher concentration resulted in the formation of franklinite. [Conclusion] The results clarified the effect of Zn on the nitrate-reducing Fe(II) oxidation process, including the rates of nitrate reduction and Fe(II) oxidation, and the mineral structure. These findings increase the understanding of the relationship between the heavy metals and the bacteria-driven Fe(II) oxidation and denitrification and provide scientific support for remediation of contaminated soils by heavy metals.