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Int. J. Environ. Res. Public Health 2018, 15(12), 2753; https://doi.org/10.3390/ijerph15122753

Humin as an External Electron Mediator for Microbial Pentachlorophenol Dechlorination: Exploration of Redox Active Structures Influenced by Isolation Methods

1
Department of Civil Engineering, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
2
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8603, Japan
*
Author to whom correspondence should be addressed.
Received: 23 October 2018 / Revised: 13 November 2018 / Accepted: 2 December 2018 / Published: 5 December 2018
(This article belongs to the Section Environmental Science and Engineering)
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Abstract

Humin (HM) has been reported to function as an external electron mediator (EEM) in various microbial reducing reactions. In this study, the effect of isolation methods on EEM functionality and the chemical/electrochemical structures of HM were examined based on the correlation between dechlorination rates in the anaerobic HM-dependent pentachlorophenol (PCP)-dechlorinating consortium and the chemical/electrochemical structures of HM. A lack of PCP dechlorination activity suggested no EEM function in the HM samples prepared as a soluble fraction in dimethyl sulfoxide and sulfuric acid (which did not contain any electric capacitance). Other HM samples exhibited EEM functionality as shown by the dechlorination activity ranging from 0.55 to 3.48 (µmol Cl) L−1d−1. The comparison of dechlorination activity with chemical structural characteristics suggested that HM with EEM functionalities had predominantly aliphatic and carbohydrate carbons with the partial structures C=O, O=C–N, and O=C–O. EEM functionality positively correlated with the proportion of O=C–N and O=C–O, suggesting an association between peptidoglycan structure and EEM functionality. The lack of detection of a quinone structure in one HM sample with EEM functionality and a negative correlation with aromatic or C=C carbon suggested that the mechanism containing quinone structures is a minor component for the functionality of EEM. View Full-Text
Keywords: humin; PCP dechlorination; external electron mediator; redox-active function; quinone structure; peptidoglycan; aromaticity humin; PCP dechlorination; external electron mediator; redox-active function; quinone structure; peptidoglycan; aromaticity
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Pham, D.M.; Katayama, A. Humin as an External Electron Mediator for Microbial Pentachlorophenol Dechlorination: Exploration of Redox Active Structures Influenced by Isolation Methods. Int. J. Environ. Res. Public Health 2018, 15, 2753.

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