Microbial Community Changes in a Chlorinated Solvents Polluted Aquifer Over the Field Scale Treatment With Poly-3-Hydroxybutyrate as Amendment.

Bruna Matturro,Marco Petrangeli Papini,Lucia Pierro,Simona Rossetti,Emanuela Frascadore

doi:10.3389/fmicb.2018.01664

Bruna Matturro, Marco Petrangeli Papini + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2018.01664

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Abstract

This study investigated the organohalide-respiring bacteria (OHRB) and the supporting microbial populations operating in a pilot scale plant employing poly-3-hydroxybutyrate (PHB), a biodegradable polymer produced by bacteria from waste streams, for the in situ bioremediation of groundwater contaminated by chlorinated solvents. The bioremediation was performed in ground treatment units, including PHB reactors as slow release source of electron donors, where groundwater extracted from the wells flows through before the re-infiltration to the low permeability zones of the aquifer. The coupling of the biological treatment with groundwater recirculation allowed to drastically reducing the contamination level and the remediation time by efficiently stimulating the growth of autochthonous OHRB and enhancing the mobilization of the pollutants. Quantitative PCR performed along the external treatment unit showed that the PHB reactor may efficiently act as an external incubator to growing Dehalococcoides mccartyi, known to be capable of fully converting chlorinated ethenes to innocuous end-products. The slow release source of electron donors for the bioremediation process allowed the establishment of a stable population of D. mccartyi, mainly carrying bvcA and vcrA genes which are implicated in the metabolic conversion of vinyl chloride to harmless ethene. Next generation sequencing was performed to analyze the phylogenetic diversity of the groundwater microbiome before and after the bioremediation treatment and allowed the identification of the microorganisms working closely with organohalide-respiring bacteria.

Highlights

Over the past 20 years, intense research efforts have been devoted to elucidate the overall mechanisms underlying the biological reductive dechlorination (RD) process and to develop effective technologies for the in situ remediation of contaminated sites (Lorenz and Löffler, 2016).The RD process is performed by specialized organohalide-respiring bacteria (OHRB) which enable the complete and efficient detoxification of a variety of aliphatic and aromatic chlorinatedMicrobiome Changes Over Bioremediation Treatment pollutants
Among the many bacterial species that are known to reductively transform organohalides, Dehalococcoides mccartyi is considered as the biomarker of the process due to the unique ability of members of this genus to fully convert chlorinated solvents to harmless products through the activity of a class of enzymes called reductive dehalogenases (RDases) (Richardson, 2013)
We report the throughout investigation on the microbial changes and the behavior of OHRB along the external operation unit of the pilot plant, focusing in particular on the PHB reactor and on the structure and role of the microbial community involved in the RD process driven by the fermentation of this slow release carbon source

Summary

Introduction

Over the past 20 years, intense research efforts have been devoted to elucidate the overall mechanisms underlying the biological reductive dechlorination (RD) process and to develop effective technologies for the in situ remediation of contaminated sites (Lorenz and Löffler, 2016).The RD process is performed by specialized organohalide-respiring bacteria (OHRB) which enable the complete and efficient detoxification of a variety of aliphatic and aromatic chlorinatedMicrobiome Changes Over Bioremediation Treatment pollutants. Among the many bacterial species that are known to reductively transform organohalides, Dehalococcoides mccartyi is considered as the biomarker of the process due to the unique ability of members of this genus to fully convert chlorinated solvents to harmless products through the activity of a class of enzymes called reductive dehalogenases (RDases) (Richardson, 2013). They are involved in the metabolic dechlorination of PCE or TCE to VC (TceA), of cis-DCE to VC and ethene (BvcA and VcrA) and are coded by the corresponding genes tceA, bvcA, and vcrA (Lee et al, 2006). The use of an integrated monitoring approach may reduce uncertainties about the ongoing groundwater processes and allow an efficient long-term management of the remedial action (Majone et al, 2015)

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