title: Humic substance-mediated reduction of iron(III) oxides and degradation of 2,4-D by an alkaliphilic bacterium, Corynebacterium humireducens MFC-5.
abstract: With the use of an alkaliphilic bacterium, Corynebacterium humireducens MFC-5, this study investigated the reduction of goethite (α-FeOOH) and degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) mediated by different humic substances (humics) and quinones in alkaline conditions (pH of 9.0). The results indicated that (i) using sucrose as the electron donor, the strain MFC-5 was capable of reducing anthraquinone-2,6-disulfonic acid (AQDS), anthraquinone-2-disulfonic acid (AQS), anthraquinone-2-carboxylic acid (AQC), humic acid (HA) and fulvic acid (FA), and its reducing capability ranked as AQC > AQS > AQDS > FA > HA; (ii) the anaerobic reduction of α-FeOOH and 2,4-D by the strain was insignificant, while the reductions were greatly enhanced by the addition of quinones/humics serving as redox mediators; (iii) the Fe(III) reduction rate was positively related to the content of quinone functional groups and the electron-accepting capacities (EAC) of quinones/humics based on fourier-transform infrared spectroscopy (FT-IR) and electrochemical analyses; however, such a relationship was not found in 2,4-D degradation probably because quinone reduction was not the rate-limiting step of quinone-mediated reduction of 2,4-D. Using the example of α-FeOOH and 2,4-D, this study well demonstrated the important role of humics reduction on the Fe(III)/Fe(II) biogeochemical cycle and chlorinated organic compounds degradation in alkaline reducing environments.
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, China.
authors.forename: Chun-yuan
authors.initials: CY
authors.lastname: Wu
authors.forename: Li
authors.initials: L
authors.lastname: Zhuang
authors.forename: Shun-gui
authors.initials: SG
authors.lastname: Zhou
authors.forename: Yong
authors.initials: Y
authors.lastname: Yuan
authors.forename: Tian
authors.initials: T
authors.lastname: Yuan
authors.forename: Fang-bai
authors.initials: FB
authors.lastname: Li
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D001673:Biodegradation, Environmental; D001709:Biotechnology / Q000379:methods; D003352:Corynebacterium / Q000145:classification / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D011809:Quinones / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D005290:Ferric Compounds; D006812:Humic Substances; D011809:Quinones; C000499:ferric oxide; D015084:2,4-Dichlorophenoxyacetic Acid