An overview of electrode materials in microbial fuel cells

Geobacter species specialize in making electrical contacts with extracellular electron acceptors and other organisms. This permits Geobacter species to fill important niches in a diversity of anaerobic environments. Geobacter species appear to be the primary agents for coupling the oxidation of organic compounds to the reduction of insoluble Fe(III) and Mn(IV) oxides in many soils and sediments, a process of global biogeochemical significance. Some Geobacter species can anaerobically oxidize aromatic hydrocarbons and play an important role in aromatic hydrocarbon removal from contaminated aquifers. The ability of Geobacter species to reductively precipitate uranium and related contaminants has led to the development of bioremediation strategies for contaminated environments. Geobacter species produce higher current densities than any other known organism in microbial fuel cells and are common colonizers of electrodes harvesting electricity from organic wastes and aquatic sediments. Direct interspecies electron exchange between Geobacter species and syntrophic partners appears to be an important process in anaerobic wastewater digesters. Functional and comparative genomic studies have begun to reveal important aspects of Geobacter physiology and regulation, but much remains unexplored. Quantifying key gene transcripts and proteins of subsurface Geobacter communities has proven to be a powerful approach to diagnose the in situ physiological status of Geobacter species during groundwater bioremediation. The growth and activity of Geobacter species in the subsurface and their biogeochemical impact under different environmental conditions can be predicted with a systems biology approach in which genome-scale metabolic models are coupled with appropriate physical/chemical models. The proficiency of Geobacter species in transferring electrons to insoluble minerals, electrodes, and possibly other microorganisms can be attributed to their unique "microbial nanowires," pili that conduct electrons along their length with metallic-like conductivity. Surprisingly, the abundant c-type cytochromes of Geobacter species do not contribute to this long-range electron transport, but cytochromes are important for making the terminal electrical connections with Fe(III) oxides and electrodes and also function as capacitors, storing charge to permit continued respiration when extracellular electron acceptors are temporarily unavailable. The high conductivity of Geobacter pili and biofilms and the ability of biofilms to function as supercapacitors are novel properties that might contribute to the field of bioelectronics. The study of Geobacter species has revealed a remarkable number of microbial physiological properties that had not previously been described in any microorganism. Further investigation of these environmentally relevant and physiologically unique organisms is warranted.

Geobacter: The Microbe Electric's Physiology, Ecology, and Practical Applications

Today, biomass covers about 10% of the world's primary energy demand. Against a backdrop of rising crude oil prices, depletion of resources, political instability in producing countries and environmental challenges, besides efficiency and intelligent use, only biomass has the potential to replace the supply of an energy hungry civilisation. Plant biomass is an abundant and renewable source of energy-rich carbohydrates which can be efficiently converted by microbes into biofuels, of which, only bioethanol is produced on an industrial scale today. Biomethane is produced on a large scale, but is not yet utilised for transportation. Biobutanol is on the agenda of several companies and may be used in the near future as a supplement for gasoline, diesel and kerosene, as well as contributing to the partially biological production of butyl-t-butylether, BTBE as does bioethanol today with ETBE. Biohydrogen, biomethanol and microbially made biodiesel still require further development. This paper reviews microbially made biofuels which have potential to replace our present day fuels, either alone, by blending, or by chemical conversion. It also summarises the history of biofuels and provides insight into the actual production in various countries, reviewing their policies and adaptivity to the energy challenges of foreseeable future.

Biofuels from microbes.

Endocrine disrupting compounds removal from wastewater, a new challenge

Biodegradation of natural and synthetic estrogens by nitrifying activated sludge and ammonia-oxidizing bacterium Nitrosomonas europaea

A novel mediator–polymer-modified anode for microbial fuel cells

The present invention relates to a microchip apparatus using liquids. More specifically, the invention provides a liquid mixing apparatus comprising at least two microchannels for introducing liquids and a mixing microchannel that connects to the at least two liquid-introducing microchannels, wherein the liquids are transported from the respective liquid-introducing microchannels toward the mixing microchannel, the apparatus further comprising means for enhancing the mixing of the liquids that converge in the mixing microchannel. The invention also provides an electrophoretic apparatus and a microchip electrophoretic apparatus for denaturing gradient gel electrophoresis.

Microfluidic treatment method and device

The behavior of estrogenic substances in the biological treatment process of sewage.

This study aimed to investigate the contribution to estrogen removal from the activated sludge of an estrogen-degrading bacterium, Novosphingobium sp. Strain JEM-1, isolated by the writers from the activated sludge. The cell numbers of the Strain JEM-1 were investigated in two full-scale wastewater-treatment plants using real-time PCR. Strain JEM-1 appears to be commonly distributed in the activated sludge. The cell numbers of Strain JEM-1 in the oxidation ditch process were higher than those in the conventional activated sludge (CAS) process, and the effluent concentrations of E1 in the CAS process tended to decrease with increased cell numbers of Strain JEM-1. In a bench-scale experiment to investigate bioaugmentation with Strain JEM-1, there was a significant difference in the effluent concentrations of estrogens between the experimental series and the control series. Linear relationships were observed between cell numbers of Strain JEM-1 and the efficiency of removal of estrogens. These results sugges...

Contribution of the estrogen-degrading bacterium Novosphingobium sp. strain JEM-1 to estrogen removal in wastewater treatment.

PROBLEM TO BE SOLVED: To provide a method of efficiently obtaining electric energy from an aqueous organic substance with a simple device. SOLUTION: In the power generating method, one of the pair of electrodes as an anode is brought into contact with solution or slurry containing viable anaerobic microbes and an organic substance, and the other as a cathode is formed at least partly by a conductive porous material having pores in a structure, mesh or fibrous material. Then, the cathode is brought into contact with air with a contact interface of the air and water existent in the pores of the cathode, the cathode is separated from the solution or the slurry through an electrolyte film, and the cathode and the anode are electrically connected to form a closed circuit, whereby, a reduction reaction is made to proceed in the cathode with oxygen as an electron acceptor, and an oxidation reaction by the microbes is made to proceed in the anode with the organic substance as an electron donor. COPYRIGHT: (C)2005,JPO&NCIPI

Akiko Miya

Papers

A novel mediator–polymer-modified anode for microbial fuel cells

Microfluidic treatment method and device

The behavior of estrogenic substances in the biological treatment process of sewage.

Contribution of the estrogen-degrading bacterium Novosphingobium sp. strain JEM-1 to estrogen removal in wastewater treatment.

Power generation method and device using organic substance