Reductive Dechlorination Research Papers - Academia.edu (original) (raw)

Polychlorobiphenyl (PCB) biodegradation was followed for 1 year in microcosms containing marine sediments collected from Mar Piccolo (Taranto, Italy) chronically contaminated by this class of hazardous compounds. The microcosms were performed under strictly anaerobic conditions with or without the addition of Dehalococcoides mccartyi, the main microorganism known to degrade PCBs through the anaerobic reductive dechlorination process. Thirty PCB congeners were monitored during the experiments revealing that the biodegradation occurred in all microcosms with a decrease in hepta-, hexa-, and penta-chlorobiphenyls (CBs) and a parallel increase in low chlorinated PCBs (tri-CBs and tetra-CBs). The concentrations of the most representative congeners detected in the original sediment, such as 245-245-CB and 2345-245-CB, and of the mixture 2356-34-CB+234-245-CB, decreased by 32.5, 23.8, and 46.7 %, respectively, after only 70 days of anaerobic incubation without any bioaugmentation treatment. Additionally, the structure and population dynamics of the microbial key players involved in the biodegradative process and of the entire mixed microbial community were accurately defined by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) in both the original sediment and during the operation of the microcosm. The reductive dehalogenase genes of D. mccartyi, specifically involved in PCB dechlorination, were also quantified using real-time PCR (qPCR). Our results demonstrated that the autochthonous microbial community living in the marine sediment, including D. mccartyi (6.32E+06 16S rRNA gene copy numbers g-1 sediment), was able to efficiently sustain the biodegradation of PCBs when controlled anaerobic conditions were imposed.

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- Bioremediation, Dehalococcoides, Biomonitoring, PCB

Passive flux meters (PFMs) have become invaluable tools for site characterization and evaluation of remediation performance at groundwater contaminated sites. To date, PFMs technology has been demonstrated in the field to measure midrange hydrophobic contaminants (e.g., chlorinated ethenes, fuel hydrocarbons, perchlorate) and inorganic ions (e.g., uranium and nitrate). However, flux measurements of low partitioning contaminants (e.g., 1,4-dioxane, hexahydro-1,3,5-trinitro-s-triazine (RDX)) and reactive ions-species (e.g., sulfate (SO 4 2−), Chromium(VI) (Cr(VI)) are still challenging because of their low retardation during transport and quick transformation under highly reducing conditions, respectively. This study is the first application of PFMs for in-situ mass flux measurements of 1,4-dioxane, RDX, Cr(VI) and SO 4 2− reduction rates. Laboratory experiments were performed to model kinetic uptake rates and extraction efficiency for sorbent selections. Silver impregnated granular activated carbon (GAC) was selected for the capture of 1,4-dioxane and RDX, whereas Purolite 300A (Bala Cynwyd, PA, USA) was selected for Cr(VI) and SO 4 2−. PFM field demonstrations measured 1,4-dioxane fluxes ranging from 13.3 to 55.9 mg/m 2 /day, an RDX flux of 4.9 mg/m 2 /day, Cr(VI) fluxes ranging from 2.3 to 2.8 mg/m 2 /day and SO 4 2− consumption rates ranging from 20 to 100 mg/L/day. This data suggests other low-partitioning contaminates and reactive ion-species could be monitored using the PFM.

- by Alexander Haluska and +2
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- Bioremediation, Bioremediation and Environmental microbiology, Bioaugmentation, Reductive Dechlorination

Abstract
Chlorinated compounds pose environmental concerns due to their toxicity and wide distribution in several matrices. Microorganisms specialized in leading anaerobic reductive dechlorination (RD) processes, including Dehalococcoides mccartyi (Dhc), are able to reduce chlorinated compounds to harmless products or to less toxic forms. Here we report the first detailed study dealing with the RD potential of heavy polluted marine sediment by evaluating the biodegradation kinetics together with the composition, dynamics and activity of indigenous microbial population.
A microcosm study was conducted under strictly anaerobic conditions on marine sediment collected near the marine coast of Sarno river mouth, one of the most polluted river in Europe. Tetrachloroethene (PCE), used as model pollutant, was completely converted to ethene within 150 days at reductive dechlorination rate equal to 0.016 meq L-1 d-1. Consecutive spikes of PCE allowed increasing the degradation kinetics up to 0.1 meq L-1d-1 within 20 days. Strictly anaerobiosis and repeated spikes of PCE stimulated the growth of indigenous Dhc cells (growth yield of ~7.0E+07 Dhc cells per μM Cl-1 released). Dhc strains carrying the reductive dehalogenase genes tceA and vcrA were detected in the original marine sediment and their number increased during the treatment as demonstrated by the high level of tceA expression at the end of the microcosm study (2.41E+05 tceA gene transcripts g-1). Notably, the structure of the microbial communities was fully described by Catalysed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) as wells as the dynamics of the dechlorinating bacteria during the microcosms operation. Interestingly, a direct role of Dhc cells was ascertained suggesting the existence of strains adapted at salinity conditions. Additionally, non-Dhc Chloroflexi were retrieved in the original sediment and were kept stable over time suggesting their likely flanking role of the RD process.

- by Enrica Presta and +1
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- Biodegradation, Kinetics of Biodegradation/bioremediation, Marine sediments, Chlorinated Solvents

The toxicity of polychlorinated biphenyls (PCB) can be efficiently reduced in contaminated marine sediments through the reductive dechlorination (RD) process lead by anaerobic organohalide bacteria. Although the process has been extensively investigated on PCB-spiked sediments, the knowledge on the identity and metabolic potential of PCB-dechlorinating microorganisms in real contaminated matrix is still limited. Aim of this study was to explore the composition and the dynamics of the microbial communities of the marine sediment collected from one of the largest Sites of National Interest (SIN) in Italy (Mar Piccolo, Taranto) under conditions promoting the PCBs RD. A long-term microcosm study revealed that autochthonous bacteria were able to sustain the PCB dechlorination at a high extent and the successive addition of an external fermentable organic substrate (lactate) caused the further depletion of the high-chlorinated PCBs (up to 70%). Next Generation Sequencing was used to describe the core microbiome of the marine sediment and to follow the changes caused by the treatments. OTUs affiliated to sulfur-oxidizing ε-proteobacteria, Sulfurovum, and Sulfurimonas, were predominant in the original sediment and increased up to 60% of total OTUs after lactate addition. Other OTUs detected in the sediment were affiliated to sulfate reducing (δ-proteobacteria) and to organohalide respiring bacteria within Chloroflexi phylum mainly belonging to Dehalococcoidia class. Among others, Dehalococcoides mccartyi was enriched during the treatments even though the screening of the specific reductive dehalogenase genes revealed the occurrence of undescribed strains, which deserve further investigations. Overall, this study highlighted the potential of members of Dehalococcoidia class in reducing the contamination level of the marine sediment from Mar Piccolo with relevant implications on the selection of sustainable bioremediation strategies to clean-up the site.

- by Bruna Matturro
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- Dehalococcoides, Biomonitoring, Polychlorinated Biphenyls, Taranto

Chlorinated compounds pose environmental concerns due to their toxicity and wide distribution in several matrices. Microorganisms specialized in leading anaerobic reductive dechlorination (RD) processes, including Dehalococcoides mccartyi (Dhc), are able to reduce chlorinated compounds to harmless products or to less toxic forms. Here we report the first detailed study dealing with the RD potential of heavy polluted marine sediment by evaluating the biodegradation kinetics together with the composition, dynamics and activity of indigenous microbial population. A microcosm study was conducted under strictly anaerobic conditions on marine sediment collected near the marine coast of Sarno river mouth, one of the most polluted river in Europe. Tetrachloroethene (PCE), used as model pollutant, was completely converted to ethene within 150 days at reductive dechlorination rate equal to 0.016 meq L −1 d −1. Consecutive spikes of PCE allowed increasing the degradation kinetics up to 0.1 meq L −1 d −1 within 20 days. Strictly anaerobiosis and repeated spikes of PCE stimulated the growth of indigenous Dhc cells (growth yield of ~7.0E + 07 Dhc cells per μM Cl −1 released). Dhc strains carrying the reductive dehalogenase genes tceA and vcrA were detected in the original marine sediment and their number increased during the treatment as demonstrated by the high level of tceA expression at the end of the microcosm study (2.41E + 05 tceA gene transcripts g −1). Notably, the structure of the microbial communities was fully described by Catalysed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) as wells as the dynamics of the dechlorinating bacteria during the microcosms operation. Interestingly, a direct role of Dhc cells was ascertained

- by Bruna Matturro
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- Bioremediation, Dehalococcoides, Reductive Dechlorination
- by José María Carmona Pérez
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- Hydrogeology, Chemistry, Bioremediation, Medicine
- by Lisa M Douglas
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- Chemistry, Stable Isotope Analysis, Environmental Chemistry, Medicine

Anaerobic granules developed for the treatment of pentachlorophenol (PCP) completely minearilized C-labeled PCP to CH and CO. Release of chloride ions from PCP was performed by live cells in the granules under anaerobic conditions. No chloride ions were released under aerobic conditions or by autoclaved cells. Addition of sulfate enhanced the initial chloride release rate and accelerated the process of mineralization of C-labeled PCP. Addition of molybdate (10 mM) inhibited the chloride release rate and severely inhibited PCP mineralization. This suggests involvement of sulfate-reducing bacteria in PCP dechlorination and mineralization. Addition of 2-bromoethane sulfonate slightly decreased the chloride release rate and completely stopped production of CH and CO from [C]PCP. 2,4,6-trichloro-phenol was observed as an intermediate during PCP dechlorination. On the basis of experimental results, dechlorination of 2,4,6-trichlorophanol by the granules was conducted through 2,4-dichlorophenol, 4-chloro-phenol or 2-chlorophenol to phenol at pH 7.0-7.2.

- by Wei-Min Wu
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- Reductive Dechlorination, Metabolic Pathyways, Chlorinated Phenols

""""Three microbial cultures were enriched on PCE (hereafter named RM3), TCE (B2), or cis-DCE (B3) (as electron acceptors) and lactate (as electron donor). All cultures, which were found to completely transform the chlorinated contaminants to ethene, were kinetically characterised and analysed to define the dynamics and activity of dechlorinating microbial populations. Specific biodegradation rates were estimated by means of conventional biomass parameter (i.e. VSS, volatile suspended solids) and by cell numbers of dechlorinating population specifically discriminated and quantified by biomolecular tools.
Kinetic batch experiments, carried out after a pseudo-steady state performance had been established, revealed that the observed dechlorination rates followed the order RM3 (PCE-enriched)>B2 (TCE-enriched)>B3 (cis-DCE-enriched).
Dechlorinating bacteria were quantified by combining in situ hybridization techniques and PCR-based approaches. Fluorescence in situ hybridization (FISH and CARD-FISH) allowed the cell numbers estimation of active and not active i) dechlorinating bacteria involved in the partial degradation of PCE or TCE to cis-DCE (Desulfitobacterium spp., Dehalobacter spp., spp., Geobacter spp., Sulfurospirillum spp.) as well as ii) “Dehalococcoides” spp. known to be able to completely dechlorinate such compounds to harmless ethene. Gene expression profile of reductive dehalogenase genes (tceA, bvcA, vcrA) were also estimated and correlated to kinetic performances and dechlorinating bacteria abundances. The potential for field application of the outputs of this study will be discussed.""""

- by Bruna Matturro
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- Bioremediation, Dehalococcoides, qPCR, FISH
- by Carolina Cruz Viggi
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- Chemistry, Bioremediation, Environmental Chemistry, Reductive Dechlorination
- by Wei-Min Wu
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- Reductive Dechlorination, Mixed Culture, perchloroethylene

A convenient method for the synthesis of tritium-labeled brassinosteroids with very high specific activity is
reported. A 3H-labeled 24-epicastasterone was isolated in high yield (40 mCi), radiochemical purity (>97%)
and a specific activity up to 99 Ci mmol1. The labeling strategy was designed to employ a radiolabeling step
at the late stage of the synthetic sequence.

- by Aleš Marek
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- STEROIDS, Enantioselective Synthesis, Tritium, Reductive Dechlorination