Bacterial Production of Organic Acids Enhances H2O2-Dependent Iodide Oxidation

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• 作者：Hsiu-Ping Li ; Chris M. Yeager ; Robin Brinkmeyer ; Saijin Zhang ; Yi-Fang Ho ; Chen Xu ; Whitney L. Jones ; Kathleen A. Schwehr ; Shigeyoshi Otosaka ; Kimberly A. Roberts ; Daniel I. Kaplan ; Peter H. Santschi
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：May 1, 2012
• 年：2012
• 卷：46
• 期：9
• 页码：4837-4844
• 全文大小：301K
• 年卷期：v.46,no.9(May 1, 2012)
• ISSN：1520-5851

文摘

To develop an understanding of the role that microorganisms play in the transport of ¹²⁹I in soil鈥搘ater systems, bacteria isolated from subsurface sediments were assessed for iodide oxidizing activity. Spent liquid medium from 27/84 bacterial cultures enhanced iodide oxidation 2鈥?0 fold in the presence of H₂O₂. Organic acids secreted by the bacteria were found to enhance iodide oxidation by (1) lowering the pH of the spent medium, and (2) reacting with H₂O₂ to form peroxy carboxylic acids, which are extremely strong oxidizing agents. H₂O₂-dependent iodide oxidation increased exponentially from 8.4 to 825.9 渭M with decreasing pH from 9 to 4. Organic acids with 鈮? carboxy groups enhanced H₂O₂-dependent iodide oxidation (1.5鈥?5-fold) as a function of increasing pH above pH 6.0, but had no effect at pH 鈮?5.0. The results indicate that as pH decreases (鈮?.0), increasing H₂O₂ hydrolysis is the driving force behind iodide oxidation. However, at pH 鈮?6.0, spontaneous decomposition of peroxy carboxylic acids, generated from H₂O₂ and organic acids, contributes significantly to iodide oxidation. The results reveal an indirect microbial mechanism, organic acid secretion coupled to H₂O₂ production, that could enhance iodide oxidation and organo-iodine formation in soils and sediments.