Microbiome Composition and Dynamics of a Reductive/Oxidative Bioelectrochemical System for Perchloroethylene Removal: Effect of the Feeding Composition

Abstract

Chlorinated solvents still represent an environmental concern that requires sustainable and innovative bioremediation strategies. This study describes the microbiome composition of a novel bioelectrochemical system (BES) based on sequential reductive/oxidative dechlorination for complete perchloroethylene (PCE) removal occurring in two separate but sequential chambers. The BES has been tested under various feeding compositions [i.e., anaerobic mineral medium (MM), synthetic groundwater (SG), and real groundwater (RG)] differing in presence of sulfate, nitrate, and iron (III). In addition, the main biomarkers of the dechlorination process have been monitored in the system under various conditions. Among them, Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes (tceA, bvcA, and vcrA) involved in anaerobic dechlorination have been quantified. The etnE and etnC genes involved in aerobic dechlorination have also been quantified. The feeding composition affected the microbiome, in particular when the BES was fed with RG. Sulfuricurvum, enriched in the reductive compartment, operated with MM and SG, suggesting complex interactions in the sulfur cycle mostly including sulfur oxidation occurring at the anodic counter electrode (MM) or coupled to nitrate reduction (SG). Moreover, the known Mycobacterium responsible for natural attenuation of VC by aerobic degradation was found abundant in the oxidative compartment fed with RG, which was in line with the high VC removal observed (92 ± 2%). D. mccartyi was observed in all the tested conditions ranging from 8.78E + 06 (with RG) to 2.35E + 07 (with MM) 16S rRNA gene copies/L. tceA was found as the most abundant reductive dehalogenase gene in all the conditions explored (up to 2.46 E + 07 gene copies/L in MM). The microbiome dynamics and the occurrence of biomarkers of dechlorination, along with the kinetic performance of the system under various feeding conditions, suggested promising implications for the scale-up of the BES, which couples reductive with oxidative dechlorination to ensure the complete removal of highly chlorinated ethylene and mobile low-chlorinated by-products.

Biodegradable polylactic acid emulsion ink based on carbon nanotubes and silver for printed pressure sensors

“…In recent years, there has been a noticeable increase in the attention given to electrogenic bacteria due to their potential utilization in environmentally friendly technologies focused on renewable energy and environmental stewardship 93 . Additionally, they can be employed for biodegradation or bio removal of specific pollutants [94][95][96] . The justification for the finding can be supported by inclusion of the conductive fillers in the coating, which can improve electron transfer between bacteria.…”

Electron Transfer in the Biogeochemical Sulfur Cycle

“…These systems encompass various technologies, such as microbial fuel cells, microbial electrolysis cells, and microbial electrosynthesis [40]. They are capable of reducing pollutants, facilitating bioremediation, recycling elements, synthesizing new products, and generating electricity [120][121][122][123][124]. For example, electroactive microorganisms release electrons capable of oxidizing and transforming organic matter and contaminants present in organic carbon-rich water, wastewater, soil, or sediment [125].…”

Evaluation of a Bioelectrochemical Reductive/Oxidative Sequential Process for Chlorinated Aliphatic Hydrocarbons (Cahs) Removal from a Real Contaminated Groundwater

“…The quantification of D. mccartyi 16S rRNA, reductive dehalogenase genes tceA, bvcA, vcrA and oxidative genes etnE and etnC involved in the oxidative dechlorination was performed on reductive and oxidative reactor effluents, respectively. Details of the methods adopted [20,[48][49][50] are included in the supplementary material.…”