title: Characterization of the enhancement of zero valent iron on microbial azo reduction.
abstract: BACKGROUND
  The microbial method for the treatment of azo dye is promising, but the reduction of azo dye is the rate-limiting step. Zero valent iron (Fe(0)) can enhance microbial azo reduction, but the interactions between microbes and Fe(0) and the potential mechanisms of enhancement remain unclear. Here, Shewanella decolorationis S12, a typical azo-reducing bacterium, was used to characterize the enhancement of Fe(0) on microbial decolorization.
  
  
  RESULTS
  The results indicated that anaerobic iron corrosion was a key inorganic chemical process for the enhancement of Fe(0) on microbial azo reduction, in which OH(-), H2, and Fe(2+) were produced. Once Fe(0) was added to the microbial azo reduction system, the proper pH for microbial azo reduction was maintained by OH(-), and H2 served as the favored electron donor for azo respiration. Subsequently, the bacterial biomass yield and viability significantly increased. Following the corrosion of Fe(0), nanometer-scale Fe precipitates were adsorbed onto cell surfaces and even accumulated inside cells as observed by transmission electron microscope energy dispersive spectroscopy (TEM-EDS).
  
  
  CONCLUSIONS
  A conceptual model for Fe(0)-assisted azo dye reduction by strain S12 was established to explain the interactions between microbes and Fe(0) and the potential mechanisms of enhancement. This model indicates that the enhancement of microbial azo reduction in the presence of Fe(0) is mainly due to the stimulation of microbial growth and activity by supplementation with elemental iron and H2 as an additional electron donor. This study has expanded our knowledge of the enhancement of microbial azo reduction by Fe(0) and laid a foundation for the development of Fe(0)-microbial integrated azo dye wastewater treatment technology.
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, 410083, Changsha, China. fangyun1987@126.com.|Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 510070, Guangzhou, China. fangyun1987@126.com.|State Key Laboratory of Applied Microbiology Southern China, 510070, Guangzhou, China. fangyun1987@126.com.|Key Laboratory of Biometallurgy of Ministry of Education, 410083, Changsha, China. fangyun1987@126.com.
authors.forename: Yun
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 510070, Guangzhou, China. xumy@gdim.cn.|State Key Laboratory of Applied Microbiology Southern China, 510070, Guangzhou, China. xumy@gdim.cn.
authors.forename: Meiying
authors.initials: M
authors.lastname: Xu
authors.affiliation: Department of Civil and Environmental Engineering, Center for Sustainable Development and Global Competitiveness, Codiga Resource Recovery Center, Stanford University, Stanford, CA, 94305, USA. wei-min.wu@stanford.edu.
authors.forename: Wei-Min
authors.initials: WM
authors.lastname: Wu
authors.affiliation: Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 510070, Guangzhou, China. xingjuan_chen@aliyun.com.|State Key Laboratory of Applied Microbiology Southern China, 510070, Guangzhou, China. xingjuan_chen@aliyun.com.
authors.forename: Xingjuan
authors.initials: X
authors.lastname: Chen
authors.affiliation: Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 510070, Guangzhou, China. guopingsun@163.com.|State Key Laboratory of Applied Microbiology Southern China, 510070, Guangzhou, China. guopingsun@163.com.
authors.forename: Guoping
authors.initials: G
authors.lastname: Sun
authors.affiliation: Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 510070, Guangzhou, China. guojun@gzb.ac.cn.|State Key Laboratory of Applied Microbiology Southern China, 510070, Guangzhou, China. guojun@gzb.ac.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Guo
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, 410083, Changsha, China. xueduanliu@yahoo.com.|Key Laboratory of Biometallurgy of Ministry of Education, 410083, Changsha, China. xueduanliu@yahoo.com.
authors.forename: Xueduan
authors.initials: X
authors.lastname: Liu
mesh_terms: D000693:Anaerobiosis; D001391:Azo Compounds / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D004583:Electrons; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D020592:Shewanella / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D062065:Wastewater
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D006859:Hydrogen; D007501:Iron; D062065:Wastewater