Use of acetate for enrichment of electrochemically active microorganisms and their 16S rDNA analyses

Abstract

A fuel cell-type electrochemical device has been used to enrich microbes oxidizing acetate with concomitant electricity generation without using an electron mediator from activated sludge. The device generated a stable current of around 5 mA with complete oxidation of 5 mM acetate at the hydraulic retention time of 2.5 h after 4 weeks of enrichment. Over 70% of electrons available from acetate oxidation was recovered as current. Carbon monoxide or hydrogen did not influence acetate oxidation or current generation from the microbial fuel cell (MFC). Denaturing gradient gel electrophoresis showed that DNA extracted from the acetate-enriched MFC had different 16S rDNA patterns from those of sludge or glucose+glutamate-enriched MFCs. Nearly complete 16S rDNA sequence analyses showed that diverse bacteria were enriched in the MFC fed with acetate. Electron microscopic observations showed biofilm developed on the electrode, but not microbial clumps observed in MFCs fed with complex fuel such as glucose and wastewater from a corn-processing factory. ß

A novel ecological role of the Firmicutes identified in thermophilic microbial fuel cells

“…Although 16S rDNA sequences belonging to the Firmicutes have previously been detected in the anode communities of active fuel cells (Lee et al, 2003;Kim et al, 2004Kim et al, , 2006Rabaey et al, 2004Rabaey et al, , 2007Aelterman et al, 2006;Hamid Rismani-Yazdi et al, 2007;Mathis et al, 2007), there are a limited number of publications where Firmicutes represent a dominant portion (450%) of the anode community composition (Rabaey et al, 2004(Rabaey et al, , 2007Aelterman et al, 2006;Hamid Rismani-Yazdi et al, 2007;Mathis et al, 2007). Previous studies of MFCs inoculated with Firmicutes isolates only produced current in the presence of an exogenous electron shuttle (Rabaey et al, 2005(Rabaey et al, , 2007Milliken and May, 2007;Pham et al, 2008) or as a byproduct of glucose fermentation (Park, 2001;Kim et al, 2005).…”

“…This is further supported by culture-independent studies, which indicate that the phylogenetic diversity of MFC microbial communities far exceeds that of electrochemically active isolates. Unfortunately, these community studies (Bond et al, 2002;Lee et al, 2003;Holmes et al, 2004;Kim et al, 2004;Rabaey et al, 2004;Aelterman et al, 2006;Jong et al, 2006;Kim et al, 2006) were hampered by the use of lowresolution DNA fingerprinting techniques targeting the 16S ribosomal RNA gene (16S rDNA), the presence of which does not necessarily demonstrate electrochemical activity but may simply be an artifact of gene persistence in the environment (Manefield et al, 2002). Furthermore, because these studies focused on gene presence (16S rDNA) rather than gene expression (16S rRNA) they could not elucidate active members of the anode biofilm.…”

Fast Biofilm Formation and Its Role on Power Generation in Palm Oil Mill Effluent Fed Microbial Fuel Cell

“…Kim et al [12] have proposed that these microbial clumps consist of bacteria that ferment the complex fuel into simple fermentation products. These products can then be used as substrate for electrochemically active bacteria within the biofilm to generate electricity [13,28].…”

Impact of Salt Concentrations on Electricity Generation using Hostel Sludge Based Duel Chambered Microbial Fuel Cell

“…This MFC mainly consists of two chambers, one of the chambers, where, oxidation takes place is call anodic chamber (anode) and the other chamber where reduction takes place is called cathodic chamber (cathode) [12][13][14][15]. In the presence of oxygen, microbes oxidize organic compounds to produce CO 2 and H 2 O, but if the reaction takes place in anaerobic environment then microbes decomposes organic materials to produce CO 2 , while proton and electrons are produced simultaneously [22][23][24]. Electrons thus produced are transferred to the cathodic chamber via an external circuit while protons are transferred through salt bridge [23].…”