Use of cassette-electrode microbial fuel cell for wastewater treatment.

Cassette-electrode microbial fuel cells (CE-MFCs) have been developed for the conversion of biomass wastes into electric energy. The present study modified CE-MFC for its application to wastewater treatment and examined its utility in a long-term (240 days) experiment to treat a synthetic wastewater, containing starch, yeast extract, peptone, plant oil, and a detergent (approximately 500 mg of total chemical oxygen demand [COD] per liter). A test MFC reactor (1 l in capacity) was equipped with 10 cassette electrodes with total anode and cathode projection areas of 1440 cm(2), and the operation was initiated by inoculating with rice paddy-field soil. It was demonstrated that CE-MFC achieved COD removal rates of 80% at hydraulic-retention times of 6 h or greater, and electricity was generated at a maximum power density of 150 mW m(-2) and Coulombic efficiency of 20%. Microbial communities established on anodes of CEs were analyzed by pyrosequencing of PCR-amplified 16S rRNA gene fragments, showing that Geobacter, Clostridium, and Geothrix were abundantly detected in anode biofilms. These results demonstrate the utility of CE-MFC for wastewater treatment, in which Geobacter and Geothrix would be involved in the electricity generation.

Methanogenesis facilitated by electric syntrophy via (semi)conductive iron-oxide minerals.

Methanogenesis is an essential part of the global carbon cycle and a key bioprocess for sustainable energy. Methanogenesis from organic matter is accomplished by syntrophic interactions among different species of microbes, in which interspecies electron transfer (IET) via diffusive carriers (e.g. hydrogen and formate) is known to be the bottleneck step. We report herein that the supplementation of soil microbes with (semi)conductive iron-oxide minerals creates unique interspecies interactions and facilitates methanogenesis. Methanogenic microbes were enriched from rice paddy field soil with either acetate or ethanol as a substrate in the absence or presence of (semi)conductive iron oxides (haematite or magnetite). We found that the supplementation with either of these iron oxides resulted in the acceleration of methanogenesis in terms of lag time and production rate, while the supplementation with an insulative iron oxide (ferrihydrite) did not. Clone-library analyses of 16S rRNA gene fragments PCR-amplified from the enrichment cultures revealed that the iron-oxide supplementation stimulated the growth of Geobacter spp. Furthermore, the addition of a specific inhibitor for methanogenesis suppressed the growth of Geobacter spp. These results suggest that Geobacter grew under syntrophic association with methanogens, and IET could occur via electric currents through (semi)conductive iron-oxide minerals (termed 'electric syntrophy'). Given the ubiquity of conductive minerals in nature, such energetic interactions may occur widely in soil and sediments and can be used to develop efficient bioenergy processes.

Roles of siderophore in manganese-oxide reduction by Shewanella oneidensis MR-1.

Dissimilatory metal-reducing bacteria (DMRB), such as Shewanella oneidensis MR-1, are of great interest for their importance in the biogeochemical cycling of metals and utility in biotechnological processes, such as bioremediation and microbial fuel cells. To identify genes necessary for metal reduction, this study constructed a random transposon-insertion mutant library of MR-1 and screened it for isolating mutants that were deficient in metal reduction. Examination of approximately 5000 mutants on lactate minimal-medium plates containing MnO(2) resulted in the isolation of one mutant, strain N22-7, that showed a decreased MnO(2)-reduction activity. Determination of a transposon-insertion site in N22-7 followed by deletion and complementation experiments revealed that the disruption of SO3030, a siderophore biosynthesis gene, was responsible for the decreased MnO(2)-reduction activity. In ΔSO3030 cells, iron and cytochrome contents were decreased to approximately 50% of those in the wild-type cells, when they were incubated under MnO(2)-reduction conditions. In addition, the transcription of genes encoding outer-membrane cytochromes necessary for metal reduction was repressed in ΔSO3030 under MnO(2)-reduction conditions, while their transcription was upregulated after supplementation of culture media with ferrous iron. These results suggest that siderophore is important for S. oneidensis MR-1 to respire MnO(2), because iron availability influences the expression of cytochromes necessary for metal reduction.

Respiratory interactions of soil bacteria with (semi)conductive iron-oxide minerals.

Pure-culture studies have shown that dissimilatory metal-reducing bacteria are able to utilize iron-oxide nanoparticles as electron conduits for reducing distant terminal acceptors; however, the ecological relevance of such energy metabolism is poorly understood. Here, soil microbial communities were grown in electrochemical cells with acetate as the electron donor and electrodes (poised at 0.2 V versus Ag/AgCl) as the electron acceptors in the presence and absence of iron-oxide nanoparticles, and respiratory current generation and community structures were analysed. Irrespective of the iron-oxide species (hematite, magnetite or ferrihydrite), the supplementation with iron-oxide minerals resulted in large increases (over 30-fold) in current, while only a moderate increase (∼10-fold) was observed in the presence of soluble ferric/ferrous irons. During the current generation, insulative ferrihydrite was transformed into semiconductive goethite. Clone-library analyses of 16S rRNA gene fragments PCR-amplified from the soil microbial communities revealed that iron-oxide supplementation facilitated the occurrence of Geobacter species affiliated with subsurface clades 1 and 2. We suggest that subsurface-clade Geobacter species preferentially thrive in soil by utilizing (semi)conductive iron oxides for their respiration.

Effect of yokukansan on the behavioral and psychological symptoms of dementia in elderly patients with Alzheimer's disease.

OBJECTIVE: The aim of this study was to investigate the effects of yokukansan (YKS) on the behavioral and psychological symptoms of dementia (BPSD) in elderly patients with Alzheimer's disease (AD). METHODS: Fifteen patients with AD (mean age: 80.2+/-4.0 years) participated in the study. The Mini-Mental State Examination (MMSE) was used for the assessment of cognitive function. BPSD were evaluated using the Neuropsychiatric Inventory (NPI). The Barthel Index was used for the assessment for the activities of daily living (ADL). The treatment with YKS along with sulpiride, a dopamine D(2) selective antipsychotic, was performed for 12 weeks. RESULTS: Fourteen patients completed the trial. After the 12 weeks of treatment with YKS, significant improvement of the mean NPI score was observed while no significant improvement was observed in the control group. The average dose of sulpiride at the end of the present study was less in the YKS group than in the control group. The MMSE results did not change either in the YKS group or in the control group. The Barthel Index did not significantly change either in the YKS group or in the control group. No serious adverse effects were noted. CONCLUSIONS: Twelve weeks of the YKS treatment significantly improved BPSD with less antipsychotics in elderly patients with AD. The YKS treatment did not cause any cognitive decline or ADL decline and no serious adverse effects were noted. The present study suggests that YKS is beneficial for the treatment of BPSD and that it can possibly reduce the doses of antipsychotics required for the treatment of BPSD. Further studies with larger patient populations using a double-blind placebo-controlled design should be performed.