Characterization of bacterial and archaeal communities in air-cathode microbial fuel cells, open circuit and sealed-off reactors

Abstract

A large percentage of organic fuel consumed in a microbial fuel cell (MFC) is lost as a result of oxygen transfer through the cathode. In order to understand how this oxygen transfer affects the microbial community structure, reactors were operated in duplicate using three configurations: closed circuit (CC; with current generation), open circuit (OC; no current generation), and sealed off cathodes (SO; no current, with a solid plate placed across the cathode). Most (98 %) of the chemical oxygen demand (COD) was removed during power production in the CC reactor (maximum of 640 ± 10 mW/m(2)), with a low percent of substrate converted to current (coulombic efficiency of 26.5 ± 2.1 %). Sealing the cathode reduced COD removal to 7 %, but with an open cathode, there was nearly as much COD removal by the OC reactor (94.5 %) as the CC reactor. Oxygen transfer into the reactor substantially affected the composition of the microbial communities. Based on analysis of the biofilms using 16S rRNA gene pyrosequencing, microbes most similar to Geobacter were predominant on the anodes in the CC MFC (72 % of sequences), but the most abundant bacteria were Azoarcus (42 to 47 %) in the OC reactor, and Dechloromonas (17 %) in the SO reactor. Hydrogenotrophic methanogens were most predominant, with sequences most similar to Methanobacterium in the CC and SO reactor, and Methanocorpusculum in the OC reactors. These results show that oxygen leakage through the cathode substantially alters the bacterial anode communities, and that hydrogenotrophic methanogens predominate despite high concentrations of acetate. The predominant methanogens in the CC reactor most closely resembled those in the SO reactor, demonstrating that oxygen leakage alters methanogenic as well as general bacterial communities.

Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities

“…The CSMER Anode community was most similar to Syntrophobacter (20.8%), Anaerolinea (15.6%) and Geobacter (12.4%), which was much different from that of CSTR Up . Geobacter , which was the most predominant known exoelectrogen, was found present only in CSMER, suggesting that exoelectrogens have a competitive advantage over other bacteria when current was generated33. The Syntrophobacter genus is a syntrophic bacteria capable of oxidizing VFAs to formate, acetate and hydrogen, which is always in coculture with hydrogen or formate-utilizing methanogens34.…”

Attenuation of trace organic compounds (TOrCs) in bioelectrochemical systems

“…3C). An opposing trend of attenuation under closed and open circuit conditions can be observed in MFCs and MECs which could be due to the activity of different microbial communities (Sayess et al, 2013;Shehab et al, 2013). In the presence of NaN 3 the attenuation of TCEP was approximately 25% in both MFCs and MECs (Fig.…”

Distribution of sediment bacterial and archaeal communities in plateau freshwater lakes

“…The average amplification efficiency and coefficient (r 2 ) for the archaeal and bacterial 16S rRNA genes were 94 % and 0.998, and 97 % and 0.999, respectively. Sediment DNA were amplified using the bacterial and archaeal primer sets 515F (5′-GTGCCAGCMGCCGCGG-3′)/806R (5′-GGACTACHVGGGTWTCTAAT-3′) and 519-537F (5′-CAGYMGCCRCGGKAAHACC-3′)/806-825R (5′-GGACTACNSGGGTMTCTAAT-3′), respectively, according to the literatures (Caporaso et al 2012;Shehab et al 2013). The amplicons from each triplicate sediment sample were mixed in equal amounts and then were subjected to Illumina MiSeq sequencing.…”