Morio Miyahara - Academia.edu (original) (raw)

Papers by Morio Miyahara

Bioresources and Bioprocessing, Nov 23, 2016

Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. ... more Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran. Findings: Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M). Polarization analyses showed that both MFCs successfully generated electricity with the maximum power densities of 360 and 520 mW m −2 (based on the projected area of anode) for MFC-W and MFC-M, respectively. Amplicon-sequencing analyses revealed that Trichococcus and Geobacter specifically occurred in anode biofilms in MFC-W and MFC-M, respectively. Conclusions: The results suggest that rice bran is a feasible fuel by itself for generating electricity in MFCs.

Journal of Water and Environment Technology, 2015

Microbial fuel cells (MFCs) are devices that are expected to be applied to the recovery of electr... more Microbial fuel cells (MFCs) are devices that are expected to be applied to the recovery of electric energy from wastewater. We have recently demonstrated that cassette-electrode MFCs (CE-MFCs) are useful for the treatment of wastewater. A concern about CE-MFCs is however relatively low columbic efficiency that may be caused by oxygen contamination from water surfaces. In the present study, floating boards were installed at the surface of water for minimizing oxygen diffusion from the air, and their effects on organics removal, electricity generation and microbial communities were analyzed. It was found that the installation of floating boards allowed an average of 10% increases in Columbic efficiency, while organic removal efficiency remained over 80%. The improved electricity generation was associated with changes in microbial communities as analyzed by denaturing gradient gel electrophoresis of 16S rRNA-gene amplicons. These results suggest the utility of floating boards for improving electricity generation in CE-MFCs used for wastewater treatment.

International Journal of Systematic and Evolutionary Microbiology, Apr 1, 2018

Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that... more Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that had been inoculated with sludge obtained from a wastewater-treatment facility in a chemical plant. The strain grows by fermenting methanol to produce acetate under anaerobic conditions, while homoacetogenic growth is not observed. MMFC1 T also grows on pyruvate and lactate but not on sugars and other organic acids. Cells are curved rods and motile, have peritrichous flagella, and form endospores. The genome sequence of strain MMFC1 T supports the physiological data. Phylogenetic analysis based on the 16S rRNA gene sequence shows that strain MMFC1 T is affiliated with the family Sporomusaceae, while the closest relative is Sporomusa ovata with nucleotide-sequence similarity of 93.5 %. Major fatty acids are iso-C 13 : 0 3-OH, C 16 : 1 !9 and iso-C 17 : 0. On the basis of its physiological, genomic and phylogenetic features, a novel genus and species are proposed to accommodate strain MMFC1 T , with the name Methylomusa anaerophila gen. nov., sp. nov. The type strain of Methylomusa anaerophila is MMFC1 T (=JCM 31821 T = KCTC 15592 T).

Journal of Bioscience and Bioengineering, Nov 1, 2014

Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize or... more Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize organic compounds using anodes as electron acceptors. Previous studies have suggested the utility of cassette-electrode (CE) MFCs for wastewater treatment, in which rice paddy-field soil was used as the inoculum. The present study attempted to convert an activated-sludge (AS) reactor to CE-MFC and use aerobic sludge in the tank as the source of microbes. We used laboratory-scale (1 L in capacity) reactors that were initially operated in an AS mode to treat synthetic wastewater, containing starch, yeast extract, peptone, plant oil, and detergents. After the organics removal became stable, the aeration was terminated, and CEs were inserted to initiate an MFC-mode operation. It was demonstrated that the MFCmode operation treated the wastewater at similar efficiencies to those observed in the AS-mode operation with CODremoval efficiencies of 75e80%, maximum power densities of 150e200 mW m L2 and Coulombic efficiencies of 20e30%. These values were similar to those of CE-MFC inoculated with the soil. Anode microbial communities were analyzed by pyrotag sequencing of 16S rRNA gene PCR amplicons. Comparative analyses revealed that anode communities enriched from the aerobic sludge were largely different from those from the soil, suggesting that similar reactor performances can be supported by different community structures. The study demonstrates that it is possible to construct wastewatertreatment MFCs by inserting CEs into water-treatment tanks.

Journal of Bioscience and Bioengineering, Nov 1, 2016

Large quantities of oils and fats are discharged into wastewater from food industries. We evaluat... more Large quantities of oils and fats are discharged into wastewater from food industries. We evaluated the possibility of using microbial fuel cells (MFCs) forthe generation of electricity from food-industry wastewater containing vegetable oils. Single-chamber MFCs were supplied with artificial wastewater containing soybean oil, and oil removal and electric output were examined under several different conditions. We found that MFC performancecould beimproved by supplementingwastewater with an emulsifier, inoculating MFCs with oil-contaminated soil, and coating the graphite-felt anodes with carbon nanotubes, resulting in a power output of more than2 W m −2 (based onthe projected area of the anode). Sequencing of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments detected abundant amount ofBurkholderiales bacteria (known to include oil degraders) in the oil-contaminated soil and anode biofilm, whereas those affiliated with the genus Geobacter were only detected in the anode biofilm. These results suggest thatMFCs can be used for energy recoveryfrom food industry wastewater containing vegetable oils.

Bioresource Technology, Oct 1, 2016

Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment ... more Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment (MBS) and continuously supplied with an acetate medium containing different concentrations of NaCl (0 to 1.8 M). Different from MFCs inoculated with paddy-field soil (high power outputs were observed between 0.05 and 0.1 M), power outputs from MBS-MFCs were high at NaCl concentrations from 0 to 0.6 M. Amplicon-sequence analyses of anode biofilms suggest that different exoelectrogens occurred from MBS depending on NaCl concentrations; Geobacter occurred abundantly below 0.1 M, whereas Desulfuromonas was abundant from 0.3 M to 0.6 M. These results suggest that NaCl concentration is the major determinant of exoelectrogens that occur in anode biofilms from MBS. It is also suggested that MBS is a potent source of microbes for MFCs to be operated in a wide range of NaCl concentrations.

Bioresource Technology, Dec 1, 2016

Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how ... more Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how supplementation with poly iron sulfate, an inorganic polymer flocculant widely used in wastewater-treatment plants, affects electricity generation and anode microbiomes. It is shown that poly iron sulfate substantially increases electric outputs from microbial fuel cells. Microbiological analyses show that iron and sulfate separately affect anode microbiomes, and the increase in power output is associated with the increases in bacteria affiliated with the families Geobacteraceae and/or Desulfuromonadaceae. We suggest that poly iron sulfate is an effective additive for increasing the electric output from microbial fuel cells. Other utilities of poly iron sulfate in microbial fuel cells are also discussed.

Scientific Reports, May 25, 2016

Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. T... more Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. They play important roles in the global carbon cycle and contribute largely to industrial wastewater treatment. To identify and characterize methylotrophs that are involved in methanol degradation in wastewater-treatment plants, methanol-fed activated-sludge (MAS) microbiomes were subjected to phylogenetic and metagenomic analyses, and genomic features of dominant methylotrophs in MAS were compared with those preferentially grown in laboratory enrichment cultures (LECs). These analyses consistently indicate that Hyphomicrobium plays important roles in MAS, while Methylophilus occurred predominantly in LECs. Comparative analyses of bin genomes reconstructed for the Hyphomicrobium and Methylophilus methylotrophs suggest that they have different C1-assimilation pathways. In addition, function-module analyses suggest that their cell-surface structures are different. Comparison of the MAS bin genome with genomes of closely related Hyphomicrobium isolates suggests that genes unnecessary in MAS (for instance, genes for anaerobic respiration) have been lost from the genome of the dominant methylotroph. We suggest that genomic features and coded functions in the MAS bin genome provide us with insights into how this methylotroph adapts to activated-sludge ecosystems.

International Journal of Systematic and Evolutionary Microbiology, 2018

Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that... more Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that had been inoculated with sludge obtained from a wastewater-treatment facility in a chemical plant. The strain grows by fermenting methanol to produce acetate under anaerobic conditions, while homoacetogenic growth is not observed. MMFC1 T also grows on pyruvate and lactate but not on sugars and other organic acids. Cells are curved rods and motile, have peritrichous flagella, and form endospores. The genome sequence of strain MMFC1 T supports the physiological data. Phylogenetic analysis based on the 16S rRNA gene sequence shows that strain MMFC1 T is affiliated with the family Sporomusaceae, while the closest relative is Sporomusa ovata with nucleotide-sequence similarity of 93.5 %. Major fatty acids are iso-C 13 : 0 3-OH, C 16 : 1 !9 and iso-C 17 : 0. On the basis of its physiological, genomic and phylogenetic features, a novel genus and species are proposed to accommodate strain MMFC1 T , with the name Methylomusa anaerophila gen. nov., sp. nov. The type strain of Methylomusa anaerophila is MMFC1 T (=JCM 31821 T = KCTC 15592 T).

Bioresources and Bioprocessing, 2016

Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. ... more Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran. Findings: Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M). Polarization analyses showed that both MFCs successfully generated electricity with the maximum power densities of 360 and 520 mW m −2 (based on the projected area of anode) for MFC-W and MFC-M, respectively. Amplicon-sequencing analyses revealed that Trichococcus and Geobacter specifically occurred in anode biofilms in MFC-W and MFC-M, respectively. Conclusions: The results suggest that rice bran is a feasible fuel by itself for generating electricity in MFCs.

Bioresource technology, 2016

Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how ... more Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how supplementation with poly iron sulfate, an inorganic polymer flocculant widely used in wastewater-treatment plants, affects electricity generation and anode microbiomes. It is shown that poly iron sulfate substantially increases electric outputs from microbial fuel cells. Microbiological analyses show that iron and sulfate separately affect anode microbiomes, and the increase in power output is associated with the increases in bacteria affiliated with the families Geobacteraceae and/or Desulfuromonadaceae. We suggest that poly iron sulfate is an effective additive for increasing the electric output from microbial fuel cells. Other utilities of poly iron sulfate in microbial fuel cells are also discussed.

Bioresource technology, 2016

Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment ... more Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment (MBS) and continuously supplied with an acetate medium containing different concentrations of NaCl (0-1.8M). Different from MFCs inoculated with paddy-field soil (high power outputs were observed between 0.05 and 0.1M), power outputs from MBS-MFCs were high at NaCl concentrations from 0 to 0.6M. Amplicon-sequence analyses of anode biofilms suggest that different exoelectrogens occurred from MBS depending on NaCl concentrations; Geobacter occurred abundantly below 0.1M, whereas Desulfuromonas was abundant from 0.3M to 0.6M. These results suggest that NaCl concentration is the major determinant of exoelectrogens that occur in anode biofilms from MBS. It is also suggested that MBS is a potent source of microbes for MFCs to be operated in a wide range of NaCl concentrations.

Journal of bioscience and bioengineering, Jan 8, 2016

Microbial fuel cells (MFCs) are devices that exploit microbes for generating electricity from org... more Microbial fuel cells (MFCs) are devices that exploit microbes for generating electricity from organic substrates, including waste biomass and wastewater pollutants. MFCs have the potential to treat wastewater and simultaneously generate electricity. The present study examined how anode macrostructure influences wastewater treatment, electricity generation and microbial communities in MFCs. Cassette-electrode MFCs were equipped with graphite-felt anodes with three different macrostructures, flat-plate (FP), vertical-fin (VF), and horizontal-fin (HF) structures (these were composed of a same amount of graphite felt), and were continuously supplied with artificial wastewater containing starch as the major organic constituent. Polarization analyses revealed that MFCs equipped with VF and HF anodes generated 33% and 21% higher volumetric power densities, respectively, than that of MFCs equipped with FP anodes. Organics were also more efficiently removed from wastewater in MFCs with VF an...

Scientific reports, May 25, 2016

Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. T... more Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. They play important roles in the global carbon cycle and contribute largely to industrial wastewater treatment. To identify and characterize methylotrophs that are involved in methanol degradation in wastewater-treatment plants, methanol-fed activated-sludge (MAS) microbiomes were subjected to phylogenetic and metagenomic analyses, and genomic features of dominant methylotrophs in MAS were compared with those preferentially grown in laboratory enrichment cultures (LECs). These analyses consistently indicate that Hyphomicrobium plays important roles in MAS, while Methylophilus occurred predominantly in LECs. Comparative analyses of bin genomes reconstructed for the Hyphomicrobium and Methylophilus methylotrophs suggest that they have different C1-assimilation pathways. In addition, function-module analyses suggest that their cell-surface structures are different. Comparison of the MAS bin ...

Journal of bioscience and bioengineering, Jan 30, 2016

Large quantities of oils and fats are discharged into wastewater from food industries. We evaluat... more Large quantities of oils and fats are discharged into wastewater from food industries. We evaluated the possibility of using microbial fuel cells (MFCs) for the generation of electricity from food-industry wastewater containing vegetable oils. Single-chamber MFCs were supplied with artificial wastewater containing soybean oil, and oil removal and electric output were examined under several different conditions. We found that MFC performance could be improved by supplementing wastewater with an emulsifier, inoculating MFCs with oil-contaminated soil, and coating the graphite-felt anodes with carbon nanotubes, resulting in a power output of more than 2 W m(-2) (based on the projected area of the anode). Sequencing of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments detected abundant amount of Burkholderiales bacteria (known to include oil degraders) in the oil-contaminated soil and anode biofilm, whereas those affiliated with the genus Geobacter were only detected in ...

Journal of bioscience and bioengineering, 2014

Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize or... more Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize organic compounds using anodes as electron acceptors. Previous studies have suggested the utility of cassette-electrode (CE) MFCs for wastewater treatment, in which rice paddy-field soil was used as the inoculum. The present study attempted to convert an activated-sludge (AS) reactor to CE-MFC and use aerobic sludge in the tank as the source of microbes. We used laboratory-scale (1 L in capacity) reactors that were initially operated in an AS mode to treat synthetic wastewater, containing starch, yeast extract, peptone, plant oil, and detergents. After the organics removal became stable, the aeration was terminated, and CEs were inserted to initiate an MFC-mode operation. It was demonstrated that the MFC-mode operation treated the wastewater at similar efficiencies to those observed in the AS-mode operation with COD-removal efficiencies of 75-80%, maximum power densities of 150-200 mW m(-2...

Journal of Bioscience and Bioengineering, 2013

Cassette-electrode microbial fuel cells (CE-MFCs) are efficient and scalable devices for electric... more Cassette-electrode microbial fuel cells (CE-MFCs) are efficient and scalable devices for electricity production from organic waste. Previous studies have demonstrated that CE-MFCs are capable of generating electricity from artificial wastewater at relatively high efficiencies. In this study, a single-cassette CE-MFC was constructed, and its capacity for electricity generation from cattle manure suspended in water (solid to water ratio of 1:50) was examined. The CE-MFC reactor was operated in batch mode for 49 days; electricity generation became stable 2 weeks after initiating the operation. The maximum power density was measured at 16.3 W m⁻³ on day 26. Sequencing analysis of PCR-amplified 16S rRNA gene fragments obtained from the original manure and from anode biofilms suggested that Chloroflexi and Geobacteraceae were abundant in the anode biofilm (29% and 18%, respectively), whereas no Geobacteraceae sequences were detected in the original manure sample. The results of this study suggest that CE-MFCs can be used to generate electricity from water-suspended cattle manure in a scalable MFC system.

Journal of Bioscience and Bioengineering, 2013

Cassette-electrode microbial fuel cells (CE-MFCs) have been developed for the conversion of bioma... more 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.

Applied Microbiology and Biotechnology, 2011

Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass ... more Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass wastes and recover electric energy from them. In order to reveal electricity-generation mechanisms in CE-MFCs, the present study operated a bench-scale reactor (1 l in capacity; approximately 1,000 cm(2) in anode and cathode areas) for treating a high-strength model organic wastewater (comprised of starch, peptone, and fish extract). Approximately 1 month was needed for the bench reactor to attain a stable performance, after which volumetric maximum power densities persisted between 120 and 150 mW/l throughout the experiment (for over 2 months). Temporal increases in the external resistance were found to induce subsequent increases in power outputs. After electric output became stable, electrolyte and anode were sampled from the reactor for evaluating their current-generation abilities; it was estimated that most of current (over 80%) was generated by microbes in the electrolyte. Cyclic voltammetry of an electrolyte supernatant detected several electron shuttles with different standard redox potentials at high concentrations (equivalent to or more than 100 μM 5-hydroxy-1,4-naphthoquinone). Denaturing gradient gel electrophoresis and quantitative real-time PCR of 16S ribosomal RNA gene fragments showed that bacteria related to the genus Dysgonomonas occurred abundantly in association with the increases in power outputs. These results suggest that mediated electron transfer was the main mechanism for electricity generation in CE-MFC, where high-concentration electron shuttles and Dysgonomonas bacteria played important roles.

Bioresources and Bioprocessing, Nov 23, 2016

Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. ... more Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran. Findings: Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M). Polarization analyses showed that both MFCs successfully generated electricity with the maximum power densities of 360 and 520 mW m −2 (based on the projected area of anode) for MFC-W and MFC-M, respectively. Amplicon-sequencing analyses revealed that Trichococcus and Geobacter specifically occurred in anode biofilms in MFC-W and MFC-M, respectively. Conclusions: The results suggest that rice bran is a feasible fuel by itself for generating electricity in MFCs.

Journal of Water and Environment Technology, 2015

Microbial fuel cells (MFCs) are devices that are expected to be applied to the recovery of electr... more Microbial fuel cells (MFCs) are devices that are expected to be applied to the recovery of electric energy from wastewater. We have recently demonstrated that cassette-electrode MFCs (CE-MFCs) are useful for the treatment of wastewater. A concern about CE-MFCs is however relatively low columbic efficiency that may be caused by oxygen contamination from water surfaces. In the present study, floating boards were installed at the surface of water for minimizing oxygen diffusion from the air, and their effects on organics removal, electricity generation and microbial communities were analyzed. It was found that the installation of floating boards allowed an average of 10% increases in Columbic efficiency, while organic removal efficiency remained over 80%. The improved electricity generation was associated with changes in microbial communities as analyzed by denaturing gradient gel electrophoresis of 16S rRNA-gene amplicons. These results suggest the utility of floating boards for improving electricity generation in CE-MFCs used for wastewater treatment.

International Journal of Systematic and Evolutionary Microbiology, Apr 1, 2018

Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that... more Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that had been inoculated with sludge obtained from a wastewater-treatment facility in a chemical plant. The strain grows by fermenting methanol to produce acetate under anaerobic conditions, while homoacetogenic growth is not observed. MMFC1 T also grows on pyruvate and lactate but not on sugars and other organic acids. Cells are curved rods and motile, have peritrichous flagella, and form endospores. The genome sequence of strain MMFC1 T supports the physiological data. Phylogenetic analysis based on the 16S rRNA gene sequence shows that strain MMFC1 T is affiliated with the family Sporomusaceae, while the closest relative is Sporomusa ovata with nucleotide-sequence similarity of 93.5 %. Major fatty acids are iso-C 13 : 0 3-OH, C 16 : 1 !9 and iso-C 17 : 0. On the basis of its physiological, genomic and phylogenetic features, a novel genus and species are proposed to accommodate strain MMFC1 T , with the name Methylomusa anaerophila gen. nov., sp. nov. The type strain of Methylomusa anaerophila is MMFC1 T (=JCM 31821 T = KCTC 15592 T).

Journal of Bioscience and Bioengineering, Nov 1, 2014

Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize or... more Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize organic compounds using anodes as electron acceptors. Previous studies have suggested the utility of cassette-electrode (CE) MFCs for wastewater treatment, in which rice paddy-field soil was used as the inoculum. The present study attempted to convert an activated-sludge (AS) reactor to CE-MFC and use aerobic sludge in the tank as the source of microbes. We used laboratory-scale (1 L in capacity) reactors that were initially operated in an AS mode to treat synthetic wastewater, containing starch, yeast extract, peptone, plant oil, and detergents. After the organics removal became stable, the aeration was terminated, and CEs were inserted to initiate an MFC-mode operation. It was demonstrated that the MFCmode operation treated the wastewater at similar efficiencies to those observed in the AS-mode operation with CODremoval efficiencies of 75e80%, maximum power densities of 150e200 mW m L2 and Coulombic efficiencies of 20e30%. These values were similar to those of CE-MFC inoculated with the soil. Anode microbial communities were analyzed by pyrotag sequencing of 16S rRNA gene PCR amplicons. Comparative analyses revealed that anode communities enriched from the aerobic sludge were largely different from those from the soil, suggesting that similar reactor performances can be supported by different community structures. The study demonstrates that it is possible to construct wastewatertreatment MFCs by inserting CEs into water-treatment tanks.

Journal of Bioscience and Bioengineering, Nov 1, 2016

Large quantities of oils and fats are discharged into wastewater from food industries. We evaluat... more Large quantities of oils and fats are discharged into wastewater from food industries. We evaluated the possibility of using microbial fuel cells (MFCs) forthe generation of electricity from food-industry wastewater containing vegetable oils. Single-chamber MFCs were supplied with artificial wastewater containing soybean oil, and oil removal and electric output were examined under several different conditions. We found that MFC performancecould beimproved by supplementingwastewater with an emulsifier, inoculating MFCs with oil-contaminated soil, and coating the graphite-felt anodes with carbon nanotubes, resulting in a power output of more than2 W m −2 (based onthe projected area of the anode). Sequencing of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments detected abundant amount ofBurkholderiales bacteria (known to include oil degraders) in the oil-contaminated soil and anode biofilm, whereas those affiliated with the genus Geobacter were only detected in the anode biofilm. These results suggest thatMFCs can be used for energy recoveryfrom food industry wastewater containing vegetable oils.

Bioresource Technology, Oct 1, 2016

Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment ... more Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment (MBS) and continuously supplied with an acetate medium containing different concentrations of NaCl (0 to 1.8 M). Different from MFCs inoculated with paddy-field soil (high power outputs were observed between 0.05 and 0.1 M), power outputs from MBS-MFCs were high at NaCl concentrations from 0 to 0.6 M. Amplicon-sequence analyses of anode biofilms suggest that different exoelectrogens occurred from MBS depending on NaCl concentrations; Geobacter occurred abundantly below 0.1 M, whereas Desulfuromonas was abundant from 0.3 M to 0.6 M. These results suggest that NaCl concentration is the major determinant of exoelectrogens that occur in anode biofilms from MBS. It is also suggested that MBS is a potent source of microbes for MFCs to be operated in a wide range of NaCl concentrations.

Bioresource Technology, Dec 1, 2016

Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how ... more Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how supplementation with poly iron sulfate, an inorganic polymer flocculant widely used in wastewater-treatment plants, affects electricity generation and anode microbiomes. It is shown that poly iron sulfate substantially increases electric outputs from microbial fuel cells. Microbiological analyses show that iron and sulfate separately affect anode microbiomes, and the increase in power output is associated with the increases in bacteria affiliated with the families Geobacteraceae and/or Desulfuromonadaceae. We suggest that poly iron sulfate is an effective additive for increasing the electric output from microbial fuel cells. Other utilities of poly iron sulfate in microbial fuel cells are also discussed.

Scientific Reports, May 25, 2016

Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. T... more Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. They play important roles in the global carbon cycle and contribute largely to industrial wastewater treatment. To identify and characterize methylotrophs that are involved in methanol degradation in wastewater-treatment plants, methanol-fed activated-sludge (MAS) microbiomes were subjected to phylogenetic and metagenomic analyses, and genomic features of dominant methylotrophs in MAS were compared with those preferentially grown in laboratory enrichment cultures (LECs). These analyses consistently indicate that Hyphomicrobium plays important roles in MAS, while Methylophilus occurred predominantly in LECs. Comparative analyses of bin genomes reconstructed for the Hyphomicrobium and Methylophilus methylotrophs suggest that they have different C1-assimilation pathways. In addition, function-module analyses suggest that their cell-surface structures are different. Comparison of the MAS bin genome with genomes of closely related Hyphomicrobium isolates suggests that genes unnecessary in MAS (for instance, genes for anaerobic respiration) have been lost from the genome of the dominant methylotroph. We suggest that genomic features and coded functions in the MAS bin genome provide us with insights into how this methylotroph adapts to activated-sludge ecosystems.

International Journal of Systematic and Evolutionary Microbiology, 2018

Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that... more Abacterial strain, designated MMFC1 T , was isolated from a methanol-fed microbial fuel cell that had been inoculated with sludge obtained from a wastewater-treatment facility in a chemical plant. The strain grows by fermenting methanol to produce acetate under anaerobic conditions, while homoacetogenic growth is not observed. MMFC1 T also grows on pyruvate and lactate but not on sugars and other organic acids. Cells are curved rods and motile, have peritrichous flagella, and form endospores. The genome sequence of strain MMFC1 T supports the physiological data. Phylogenetic analysis based on the 16S rRNA gene sequence shows that strain MMFC1 T is affiliated with the family Sporomusaceae, while the closest relative is Sporomusa ovata with nucleotide-sequence similarity of 93.5 %. Major fatty acids are iso-C 13 : 0 3-OH, C 16 : 1 !9 and iso-C 17 : 0. On the basis of its physiological, genomic and phylogenetic features, a novel genus and species are proposed to accommodate strain MMFC1 T , with the name Methylomusa anaerophila gen. nov., sp. nov. The type strain of Methylomusa anaerophila is MMFC1 T (=JCM 31821 T = KCTC 15592 T).

Bioresources and Bioprocessing, 2016

Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. ... more Background: Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran. Findings: Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M). Polarization analyses showed that both MFCs successfully generated electricity with the maximum power densities of 360 and 520 mW m −2 (based on the projected area of anode) for MFC-W and MFC-M, respectively. Amplicon-sequencing analyses revealed that Trichococcus and Geobacter specifically occurred in anode biofilms in MFC-W and MFC-M, respectively. Conclusions: The results suggest that rice bran is a feasible fuel by itself for generating electricity in MFCs.

Bioresource technology, 2016

Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how ... more Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how supplementation with poly iron sulfate, an inorganic polymer flocculant widely used in wastewater-treatment plants, affects electricity generation and anode microbiomes. It is shown that poly iron sulfate substantially increases electric outputs from microbial fuel cells. Microbiological analyses show that iron and sulfate separately affect anode microbiomes, and the increase in power output is associated with the increases in bacteria affiliated with the families Geobacteraceae and/or Desulfuromonadaceae. We suggest that poly iron sulfate is an effective additive for increasing the electric output from microbial fuel cells. Other utilities of poly iron sulfate in microbial fuel cells are also discussed.

Bioresource technology, 2016

Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment ... more Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment (MBS) and continuously supplied with an acetate medium containing different concentrations of NaCl (0-1.8M). Different from MFCs inoculated with paddy-field soil (high power outputs were observed between 0.05 and 0.1M), power outputs from MBS-MFCs were high at NaCl concentrations from 0 to 0.6M. Amplicon-sequence analyses of anode biofilms suggest that different exoelectrogens occurred from MBS depending on NaCl concentrations; Geobacter occurred abundantly below 0.1M, whereas Desulfuromonas was abundant from 0.3M to 0.6M. These results suggest that NaCl concentration is the major determinant of exoelectrogens that occur in anode biofilms from MBS. It is also suggested that MBS is a potent source of microbes for MFCs to be operated in a wide range of NaCl concentrations.

Journal of bioscience and bioengineering, Jan 8, 2016

Microbial fuel cells (MFCs) are devices that exploit microbes for generating electricity from org... more Microbial fuel cells (MFCs) are devices that exploit microbes for generating electricity from organic substrates, including waste biomass and wastewater pollutants. MFCs have the potential to treat wastewater and simultaneously generate electricity. The present study examined how anode macrostructure influences wastewater treatment, electricity generation and microbial communities in MFCs. Cassette-electrode MFCs were equipped with graphite-felt anodes with three different macrostructures, flat-plate (FP), vertical-fin (VF), and horizontal-fin (HF) structures (these were composed of a same amount of graphite felt), and were continuously supplied with artificial wastewater containing starch as the major organic constituent. Polarization analyses revealed that MFCs equipped with VF and HF anodes generated 33% and 21% higher volumetric power densities, respectively, than that of MFCs equipped with FP anodes. Organics were also more efficiently removed from wastewater in MFCs with VF an...

Scientific reports, May 25, 2016

Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. T... more Methylotrophs are organisms that are able to grow on C1 compounds as carbon and energy sources. They play important roles in the global carbon cycle and contribute largely to industrial wastewater treatment. To identify and characterize methylotrophs that are involved in methanol degradation in wastewater-treatment plants, methanol-fed activated-sludge (MAS) microbiomes were subjected to phylogenetic and metagenomic analyses, and genomic features of dominant methylotrophs in MAS were compared with those preferentially grown in laboratory enrichment cultures (LECs). These analyses consistently indicate that Hyphomicrobium plays important roles in MAS, while Methylophilus occurred predominantly in LECs. Comparative analyses of bin genomes reconstructed for the Hyphomicrobium and Methylophilus methylotrophs suggest that they have different C1-assimilation pathways. In addition, function-module analyses suggest that their cell-surface structures are different. Comparison of the MAS bin ...

Journal of bioscience and bioengineering, Jan 30, 2016

Large quantities of oils and fats are discharged into wastewater from food industries. We evaluat... more Large quantities of oils and fats are discharged into wastewater from food industries. We evaluated the possibility of using microbial fuel cells (MFCs) for the generation of electricity from food-industry wastewater containing vegetable oils. Single-chamber MFCs were supplied with artificial wastewater containing soybean oil, and oil removal and electric output were examined under several different conditions. We found that MFC performance could be improved by supplementing wastewater with an emulsifier, inoculating MFCs with oil-contaminated soil, and coating the graphite-felt anodes with carbon nanotubes, resulting in a power output of more than 2 W m(-2) (based on the projected area of the anode). Sequencing of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments detected abundant amount of Burkholderiales bacteria (known to include oil degraders) in the oil-contaminated soil and anode biofilm, whereas those affiliated with the genus Geobacter were only detected in ...

Journal of bioscience and bioengineering, 2014

Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize or... more Wastewater can be treated in microbial fuel cells (MFCs) with the aid of microbes that oxidize organic compounds using anodes as electron acceptors. Previous studies have suggested the utility of cassette-electrode (CE) MFCs for wastewater treatment, in which rice paddy-field soil was used as the inoculum. The present study attempted to convert an activated-sludge (AS) reactor to CE-MFC and use aerobic sludge in the tank as the source of microbes. We used laboratory-scale (1 L in capacity) reactors that were initially operated in an AS mode to treat synthetic wastewater, containing starch, yeast extract, peptone, plant oil, and detergents. After the organics removal became stable, the aeration was terminated, and CEs were inserted to initiate an MFC-mode operation. It was demonstrated that the MFC-mode operation treated the wastewater at similar efficiencies to those observed in the AS-mode operation with COD-removal efficiencies of 75-80%, maximum power densities of 150-200 mW m(-2...

Journal of Bioscience and Bioengineering, 2013

Cassette-electrode microbial fuel cells (CE-MFCs) are efficient and scalable devices for electric... more Cassette-electrode microbial fuel cells (CE-MFCs) are efficient and scalable devices for electricity production from organic waste. Previous studies have demonstrated that CE-MFCs are capable of generating electricity from artificial wastewater at relatively high efficiencies. In this study, a single-cassette CE-MFC was constructed, and its capacity for electricity generation from cattle manure suspended in water (solid to water ratio of 1:50) was examined. The CE-MFC reactor was operated in batch mode for 49 days; electricity generation became stable 2 weeks after initiating the operation. The maximum power density was measured at 16.3 W m⁻³ on day 26. Sequencing analysis of PCR-amplified 16S rRNA gene fragments obtained from the original manure and from anode biofilms suggested that Chloroflexi and Geobacteraceae were abundant in the anode biofilm (29% and 18%, respectively), whereas no Geobacteraceae sequences were detected in the original manure sample. The results of this study suggest that CE-MFCs can be used to generate electricity from water-suspended cattle manure in a scalable MFC system.

Journal of Bioscience and Bioengineering, 2013

Cassette-electrode microbial fuel cells (CE-MFCs) have been developed for the conversion of bioma... more 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.

Applied Microbiology and Biotechnology, 2011

Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass ... more Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass wastes and recover electric energy from them. In order to reveal electricity-generation mechanisms in CE-MFCs, the present study operated a bench-scale reactor (1 l in capacity; approximately 1,000 cm(2) in anode and cathode areas) for treating a high-strength model organic wastewater (comprised of starch, peptone, and fish extract). Approximately 1 month was needed for the bench reactor to attain a stable performance, after which volumetric maximum power densities persisted between 120 and 150 mW/l throughout the experiment (for over 2 months). Temporal increases in the external resistance were found to induce subsequent increases in power outputs. After electric output became stable, electrolyte and anode were sampled from the reactor for evaluating their current-generation abilities; it was estimated that most of current (over 80%) was generated by microbes in the electrolyte. Cyclic voltammetry of an electrolyte supernatant detected several electron shuttles with different standard redox potentials at high concentrations (equivalent to or more than 100 μM 5-hydroxy-1,4-naphthoquinone). Denaturing gradient gel electrophoresis and quantitative real-time PCR of 16S ribosomal RNA gene fragments showed that bacteria related to the genus Dysgonomonas occurred abundantly in association with the increases in power outputs. These results suggest that mediated electron transfer was the main mechanism for electricity generation in CE-MFC, where high-concentration electron shuttles and Dysgonomonas bacteria played important roles.