Development of an electroactive aerobic biocathode for microbial fuel cell applications
TL;DR: It is suggested that microbial consortia are capable of replacing expensive platinum as a cathode catalyst in microbial fuel cells (MFCs) with a variety of CO2 fixing and nitrate reducing bacteria.
Abstract: Microbial biocathodes are gaining interest due to their low cost, environmental friendliness and sustainable nature. In this study, a microbial consortium was enriched from activated sludge obtained from a common textile effluent treatment plant in the absence of organic carbon source to produce an electroactive biofilm. Chronoamperometry method of enrichment was carried out for over 70 days to select for electroactive bacteria that could be used as a cathode catalyst in microbial fuel cells (MFC). The resultant biofilm produced an average peak current of -0.7 mA during the enrichment and produced a maximum power density of 64.6 ± 3.5 mW m-2 compared to platinum (72.7 ± 1.2 mW m-2 ) in a Shewanella-based MFC. Microbial community analysis of the initial sludge sample and enriched samples, based on 16S rRNA gene sequencing, revealed the selection of chemolithotrophs with the most dominant phylum being Bacteroidetes, Proteobacteria, Firmicutes, Actinobacteria and Acidobacteria in the enriched samples. A variety of CO2 fixing and nitrate-reducing bacteria was present in the resultant biofilm on the cathode. This study suggests that microbial consortia are capable of replacing expensive platinum as a cathode catalyst in MFCs.
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TL;DR: In this paper, the basic operational characteristics of microbial fuel cells and microbial electrolysis cells using wastewater as fuel have been highlighted, along with challenges related to their operation, as well as possible integration with other technologies, have all been critically discussed.
Abstract: The application of bioelectrochemical systems mostly aims to be used for the generation of electricity or chemicals. The quest to generate energy that is both sustainable and environmentally friendly over the last few years has accelerated the growth in research activities in bioelectrochemical cells, namely: microbial fuel cells (MFCs), microbial electrolysis cells (MECs), microbial desalination cells (MDCs), and microbial electrolysis desalination cells (MEDCs). Microbial fuel cells and microbial electrolysis cells are considered the most developed technologies among these various types of bioelectrochemical systems. This investigation, intends to highlight the basic operational characteristics of MFCs and MECs using wastewater as fuel. The prospects associated with this novel technology, along with challenges related to their operation, have all been highlighted in this investigation. The application of bioelectrochemical systems, as well as possible integration with other technologies, have all been critically discussed. Moreover, the current work identified key factors impeding the commercialization of these technologies, including lower efficiencies, mass transfer limitations, porosity, and protonic conductivity. Other factors include the mechanical and chemical stability of materials, along with their biocompatibility. In summary, the application of bioelectrochemical systems futuristically will revolve around energy generation, mitigation of toxic gas emissions, wastewater treatment, bioanalysis, and environmental remediation.
67 citations
TL;DR: In this paper, the food-energy-water (FEW) nexus in biorefineries and bio-electrochemical system (BES) and looking into the energy-efficient and value-added product recovery has been discussed.
Abstract: Concerns around acquiring the appropriate resources toward a growing world population have emphasized the significance of crucial connections between food, energy, and water devices, as described within the food-energy-water nexus theory. Advanced biorefineries provide second-generation biofuels and added-value chemicals through food products have affected these nexus sources. We combine various conversion technologies and expected options to look further for cost-effective technologies that maximize the value of resource use and reuse and minimize the amount of resource needed and environmental impacts. In this review article, our central focus is on structure and application, the outline of food-energy-water (FEW) nexus in biorefineries and bio-electrochemical system (BES) and looking into the energy-efficient and value-added product recovery. In addition, based on BES analysis for energy efficiency and valuable product recoveries such as hydrogen evaluation, acetate, recovery of heavy metals, nutrient’s recovery has been discussed under this article. Additionally, we focused on wastewater processing methods, novel electrode materials used in BES, BESs-based desalination and wastewater treatment, recent BES architecture and designs, genetic engineering for enhanced productivity, and valuable materials production surfactants and hydrogen peroxide. Finally, we concluded the topic by discussing the remediation of soil contamination, photosynthetic & microfluidic BES systems, possibilities of employing CO2, including prospects and challenges.
24 citations
TL;DR: A three-chamber electrochemical membrane bioreactor with a microbial fuel cell was employed to co-treat synthetic wastewater and 20% landfill leachate (LFL) and produce electrical energy.
Abstract: A three-chamber electrochemical membrane bioreactor (EMBR) with a microbial fuel cell (MFC) was employed to co-treat synthetic wastewater and 20% landfill leachate (LFL) and produce electrical energy. We observed the following removal rates: 98 ± 1% of BOD5,20, 86 ± 5% of COD, 79 ± 2% of N-NH4+, 72 ± 6% of DOC and 43 ± 3% of N-total, while voltage generation was 463 ± 41 mV. The EMBR compartments showed distinct microbial communities and inferred metabolic pathways. Acinetobacter spp. was the most abundant bacteria in the anodic biofilm and has an important role in energy generation, as noted elsewhere. Meanwhile, the high abundance of Nitrospira spp. in the cathodic biofilm indicated its importance in the nitrification process in this system, essential for treating matrices with high-nitrogen content, such as LFL. Important abundant metabolic pathways inferred in the EMBR also included aerobic chemoheterotrophs, fermenters, degraders of aromatic compounds/hydrocarbon, and denitrifiers. Clearly, metabolic groups showed that microbial communities developed in the EMBR can degrade organic matter and remove toxic compounds (e.g., aromatic compounds) and nitrogen from LFL while producing energy. Furthermore, this study indicated that a MBR coupled with MFC create a great system for the co-treatment of LFL with wastewater, achieving both pollutant removal and electrical energy generation.
19 citations
TL;DR: In this article , a review of effective methods for the remediation of water contaminated with heavy metals is presented, concluding that bio-sorption is among the most employed and successful mechanisms because of its high efficacy and eco-friendly nature.
14 citations
TL;DR: In this paper , secondary electroactive biofilms were formed on carbon electrodes from Desulfuromonas-dominated inoculum of pre-formed bioanodes, and the performance of primary bio-anodes when the planktonic community was conserved, a Clostridium enrichment allowed to restore the performance in maximal current densities promoting an increase of Geobacter population.
10 citations
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TL;DR: This genome has provided new insights into the growth and metabolism of ammonia-oxidizing bacteria as well as predicted insertion sequence elements in eight different families.
Abstract: Nitrosomonas europaea (ATCC 19718) is a gram-negative obligate chemolithoautotroph that can derive all its energy and reductant for growth from the oxidation of ammonia to nitrite. Nitrosomonas europaea participates in the biogeochemical N cycle in the process of nitrification. Its genome consists of a single circular chromosome of 2,812,094 bp. The GC skew analysis indicates that the genome is divided into two unequal replichores. Genes are distributed evenly around the genome, with ∼47% transcribed from one strand and ∼53% transcribed from the complementary strand. A total of 2,460 protein-encoding genes emerged from the modeling effort, averaging 1,011 bp in length, with intergenic regions averaging 117 bp. Genes necessary for the catabolism of ammonia, energy and reductant generation, biosynthesis, and CO 2 and NH 3 assimilation were identified. In contrast, genes for catabolism of organic compounds are limited. Genes encoding transporters for inorganic ions were plentiful, whereas genes encoding transporters for organic molecules were scant. Complex repetitive elements constitute ca. 5% of the genome. Among these are 85 predicted insertion sequence elements in eight different families. The strategy of N. europaea to accumulate Fe from the environment involves several classes of Fe receptors with more than 20 genes devoted to these receptors. However, genes for the synthesis of only one siderophore, citrate, were identified in the genome. This genome has provided new insights into the growth and metabolism of ammonia-oxidizing bacteria.
514 citations
TL;DR: Biocathodes alleviate the need to use noble or non-noble catalysts for the reduction of oxygen, which increases substantially the viability and sustainability of MFCs.
Abstract: The reduction of oxygen at the cathode is one of the major bottlenecks of microbial fuel cells (MFCs). While research so far has mainly focused on chemical catalysis of this oxygen reduction, here we present a continuously wetted cathode with microorganisms that act as biocatalysts for oxygen reduction. We combined the anode of an acetate oxidizing tubular microbial fuel cell with an open air biocathode for electricity production. The maximum power production was 83 11 W m(-3) MFC (0.183 L MFC) for batchfed systems (20-40% Coulombic yield) and 65 5 W m(-3) MFC for a continuous system with an acetate loading rate of 1.5 kg COD m(-3) day(-1) (90 +/- 3% Coulombic yield). Electrochemical precipitation of manganese oxides on the cathodic graphite felt decreased the start-up period with approximately 30% versus a non-treated graphite felt. After the start-up period, the cell performance was similar for the pretreated and non-treated cathodic electrodes. Several reactor designs were tested, and it was found that enlargement of the 0.183 L MFC reactor by a factor 2.9-3.8 reduced the volumetric power output by 60-67%. Biocathodes alleviate the need to use noble or non-noble catalysts for the reduction of oxygen, which increases substantially the viability and sustainability of MFCs.
395 citations
TL;DR: A carbon cathode open to the air is described, on which attached bacteria catalyzed oxygen reduction using electrons provided by the solid-phase cathode, and the strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction.
Abstract: Microbial fuel cells (MFCs) have the potential to combine wastewater treatment efficiency with energetic efficiency. One of the major impediments to MFC implementation is the operation of the cathode compartment, as it employs environmentally unfriendly catalysts such as platinum. As recently shown, bacteria can facilitate sustainable and cost-effective cathode catalysis for nitrate and also oxygen. Here we describe a carbon cathode open to the air, on which attached bacteria catalyzed oxygen reduction. The bacteria present were able to reduce oxygen as the ultimate electron acceptor using electrons provided by the solid-phase cathode. Current densities of up to 2.2 A m(-2) cathode projected surface were obtained (0.303 +/- 0.017 W m(-2), 15 W m(-3) total reactor volume). The cathodic microbial community was dominated by Sphingobacterium, Acinetobacter and Acidovorax sp., according to 16S rRNA gene clone library analysis. Isolates of Sphingobacterium sp. and Acinetobacter sp. were obtained using H-2/O-2 mixtures. Some of the pure culture isolates obtained from the cathode showed an increase in the power output of up to three-fold compared to a non-inoculated control, that is, from 0.015 +/- 0.001 to 0.049 +/- 0.025 W m(-2) cathode projected surface. The strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction. Owing to the high overpotential for non-catalyzed reduction, oxygen is only to a limited extent competitive toward the electron donor, that is, the cathode. Further research to refine the operational parameters and increase the current density by modifying the electrode surface and elucidating the bacterial metabolism is warranted.
276 citations
TL;DR: This pre-enrichment procedure enables simplified start-up of anaerobic biocathodes for applications such as electrofuel production by facultatively autotrophic electrotrophs.
131 citations