Michihiko Ike

Osaka University, Suika, Ōsaka, Japan

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Publications (164)287.97 Total impact

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    ABSTRACT: Simultaneous anammox and denitrification (SAD) process was simulated by using SBRs.•The SAD process was demonstrated in SBRs fed with ammonium, nitrate, and acetate.•Nitrogen removal in the SBR remained high for a long term in wide C/N ratios.•The anammox contribution to nitrogen removal was high at low C/N ratios.•A C/N ratio <2.0 is important to maintain the SAD process in the SBR.
    Bioresource Technology 12/2014; 174. · 5.04 Impact Factor
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    ABSTRACT: AimsTo clarify the polyhydroxyalkanoate (PHA) accumulation potential and the PHA-accumulating microbial community structure in activated sludge in municipal wastewater treatment plants (WWTPs) and to identify their influential factors.Methods and ResultsNine activated sludge samples were collected from municipal WWTPs employing various biological treatment processes. In acetate-fed 24-h batch experiments under aerobic and nitrogen- and phosphorus-limited conditions, polyhydroxybutyrate (PHB) content of activated sludge increased from 0–1.3 wt% to 7.9–24 wt%, with PHB yields of 0.22–0.50 C-mol 3-hydroxybutyrate (C-mol acetate)‒1. Microbial community analyses found that activated sludge samples that accumulated >20 wt% of PHB after 24-h PHA accumulation experiments had >5.0×108 copies/g-mixed liquor suspended solid of phaC genes.Conclusions Results indicated that (i) activated sludge in municipal WWTPs can accumulate up to approximately 20 wt% of PHA without enrichment processes, (ii) PHA accumulation potential of activated sludge varied depending on the operational conditions (treatment processes) of WWTPs, and (iii) phaC gene number can provide a simple indication of PHA accumulation potential.Significance and Impact of StudyThis is the first study to compare the PHA accumulation potential and PHA-accumulating microbial communities in activated sludge of various treatment processes. Our findings may be useful for enhancing the resource recovery potential of wastewater treatment systems.This article is protected by copyright. All rights reserved.
    Journal of Applied Microbiology 11/2014; · 2.20 Impact Factor
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    ABSTRACT: Because of heavy dependence on groundwater for drinking water and other domestic use, microbial contamination of groundwater is a serious problem in the Kathmandu Valley, Nepal. This study investigated comprehensively the occurrence of pathogenic bacteria in shallow well groundwater in the Kathmandu Valley by applying DNA microarray analysis targeting 941 pathogenic bacterial species/groups. Water quality measurements found significant coliform (fecal) contamination in 10 of the 11 investigated groundwater samples and significant nitrogen contamination in some samples. The results of DNA microarray analysis revealed the presence of 1-37 pathogen species/groups, including 1-27 biosafety level 2 ones, in 9 of the 11 groundwater samples. While the detected pathogens included several feces- and animal-related ones, those belonging to Legionella and Arthrobacter, which were considered not to be directly associated with feces, were detected prevalently. This study could provide a rough picture of overall pathogenic bacterial contamination in the Kathmandu Valley, and demonstrated the usefulness of DNA microarray analysis as a comprehensive screening tool of a wide variety of pathogenic bacteria.
    Current microbiology. 08/2014;
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    ABSTRACT: A novel DNA microarray analysis targeting key functional genes involved in most nitrogen cycling reactions was developed to comprehensively analyze microbial populations associated with the nitrogen cycle. The developed microarray contained 876 oligonucleotide probes based on the nucleotide sequences of the nif, amo, hao/hzo, nap, nar, nirK, nirS, nrf, cnor, qnor and nos genes. An analytical method combining detection by the designed microarray with whole community genome amplification was then applied to monitor the nitrogen cycling microorganisms in river water and wastewater treatment sludge samples. The developed method revealed that nitrogen cycling microorganisms in river water appeared to become less diverse in response to input of effluent from municipal wastewater treatment plants. Additionally, the nitrogen cycling community associated with anaerobic ammonium oxidation and partial nitrification reactors could be reasonably analyzed by the developed method. However, the results obtained for two activated sludge samples from municipal wastewater treatment plants with almost equivalent wastewater treatment performance differed greatly from each other. These results suggested that the developed method is useful for comprehensive analysis of nitrogen cycling microorganisms, although its applicability to complex samples with abundant untargeted populations should be further examined.
    World Journal of Microbiology and Biotechnology 08/2014; · 1.35 Impact Factor
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    ABSTRACT: To elucidate the bacterial community dynamics in a full-scale wastewater treatment plant (WWTP) and the relatedness among bacterial communities in the influent, effluent and sludge, the structure and metabolic ability of the bacterial community throughout a full-scale WWTP employing a conventional activated sludge process was investigated during a period of 10 months. The bacterial community structure was analyzed by terminal-restriction fragment length polymorphism targeting eubacterial 16S rRNA genes, while a Biolog assay was applied to assess the metabolic ability of the activated sludge. Influent bacterial community structure was generally stable. In contrast, the bacterial community structure in the effluent was similar to that in the influent in some cases, while in other cases it was unique and differed greatly from that in the influent and sludge. These results suggest that temporal variations of the effluent bacterial community may be useful to predict the wastewater treatment performance and settleability of activated sludge. The bacterial community structure in the sludge was relatively stable and was rarely impacted by the influent populations. Biolog assay also revealed that activated sludge maintained a remarkably similar metabolic potential of organic compounds over time due to functional redundancy, in which the minor populations played a significant role.
    Journal of Bioscience and Bioengineering 01/2014; · 1.74 Impact Factor
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    ABSTRACT: Pseudomonas aeruginosa strain RB is a bacterium capable of synthesizing cadmium selenide (CdSe) nanoparticles and was isolated from a soil sample. Here, we present the draft genome sequence of P. aeruginosa strain RB. To the best of our knowledge, this is the first report of a draft genome of a CdSe-synthesizing bacterium.
    Genome announcements. 01/2014; 2(3).
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    ABSTRACT: Bacteria capable of synthesizing CdSe from selenite and cadmium ion were enriched from a soil sample. After repeated transfer of the soil-derived bacterial cultures to a new medium containing selenite and cadmium ion 42 times (during 360 days), an enrichment culture that can simultaneously remove selenite and cadmium ion (1 mM each) from the liquid phase was obtained. The culture's color became reddish-brown, indicating CdSe nanoparticle production, as confirmed by energy-dispersive x-ray spectra (EDS). As a result of isolation operations, the bacterium that was the most responsible for synthesizing CdSe, named Pseudomonas sp. RB, was obtained. Transmission electron microscopy and EDS revealed that this strain accumulated nanoparticles (10-20 nm) consisting of selenium and cadmium inside and on the cells when cultivated in the same medium for the enrichment culture. This report is the first describing isolation of a selenite-reducing and cadmium-resistant bacterium. It is useful for CdSe nanoparticle synthesis in the simple one-vessel operation.
    Journal of Bioscience and Bioengineering 11/2013; · 1.74 Impact Factor
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    ABSTRACT: Four novel metabolic 1,4-dioxane degrading bacteria possessing high ability to degrade 1,4-dioxane (designated strains D1, D6, D11 and D17) were isolated from soil in the drainage area of a chemical factory. Strains D6, D11 and D17 were allocated to Gram-positive actinomycetes, similar to previously reported metabolic 1,4-dioxane degrading bacteria, whereas strain D1 was allocated to Gram-negative Afipia sp. The isolated strains could utilize a variety of carbon sources, including cyclic ethers, especially those with carbons at position 2 that were modified with methyl- or carbonyl-groups. The cell yields on 1,4-dioxane were relatively low (0.179-0.223 mg-protein (mg-1,4-dioxane)(-1)), which was likely due to requiring energy for C-O bond fission. The isolated strains showed 2.6-13 times higher specific 1,4-dioxane degradation rates (0.052-0.263 mg-1,4-dioxane (mg-protein)(-1) h(-1)) and 2.3-7.8 fold lower half saturation constants (20.6-69.8 mg L(-1)) than the most effective 1,4-dioxane degrading bacterium reported to date, Pseudonocardia dioxanivorans CB1190, suggesting high activity and affinity toward 1,4-dioxane degradation. Strains D1 and D6 possessed inducible 1,4-dioxane degrading enzymes, whereas strains D11 and D17 possessed constitutive ones. 1,4-Dioxane degradation (100 mg L(-1)) by Afipia sp. D1 was not affected by the co-existence of up to 3,000 mg L(-1) of ethylene glycol. The effects of initial pH, incubation temperature and NaCl concentration on 1,4-dioxane degradation by the four strains revealed that they could degrade 1,4-dioxane under a relatively wide range of conditions, suggesting that they have a certain adaptability and applicability for industrial wastewater treatment.
    Biodegradation 09/2013; 24(5):665-674. · 2.17 Impact Factor
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    ABSTRACT: The nutrient removal and biomass production with duckweed Wolffia arrhiza was assessed using laboratory-scale continuous-flow mesocosms fed with model wastewater. Average removal rates of nitrogen and phosphorus by vegetative fronds were 0.03–0.18 mg-N/m2/d and 0.023–0.079 mg-P/m2/d, respectively. The maximum production rates of the vegetative fronds and the turions were respectively 86–160 g-wet/m2/d and 55–64 g-wet/m2/d, depending on the nutrient concentration. The kinetic data of the biomass and nutrient concentrations were analyzed using a mathematical model, which showed that the maximum specific growth rate of W. arrhiza was 0.35–0.38 d−1, whereas the turion formation was induced when the specific growth rate decreased below 0.085–0.12 d−1 in low-nitrogen conditions. The model developed in this study is applicable for predicting the wastewater treatment performance and biomass production of preferential biomass, the protein-rich vegetative fronds, the starch-rich turions, or total biomass of W. arrhiza.
    Ecological Engineering 08/2013; 57:210–215. · 2.96 Impact Factor
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    ABSTRACT: Retinoic acid (RA) receptor (RAR) agonists are potential teratogens to various vertebrates. Their contamination has been detected in municipal wastewater in different countries. This study involved field investigations and laboratory batch treatment experiments to elucidate the removal characteristics by activated sludge treatment of RAs (all-trans RA and 13-cis RA) and 4-oxo-RAs (4-oxo-all-trans RA and 4-oxo-13-cis RA), which were identified as major RAR agonists in municipal wastewater. Results obtained in this study show that currently employed activated sludge treatments can remove RAs, 4-oxo-RAs and overall RAR agonist contamination effectively from municipal wastewater in general, although high RAR agonistic activity might sometimes remain in the effluent. Laboratory experiments revealed that RAs were removed rapidly from the aqueous phase by adsorption to the sludge, after which they were removed further by biological and/or chemical degradation. Aside from adsorption to the sludge, 4-oxo-RAs were also apparently removed by biological and chemical degradation. Biodegradation contributed greatly to the removal. Results of additional experiments indicated that novel non-identifiable RAR agonists can occur through the biodegradation of 4-oxo-RAs by activated sludge and that they can persist for a long period.
    Water Science & Technology 06/2013; 67(12):2868-2874. · 1.10 Impact Factor
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    ABSTRACT: Plasmid-mediated bioaugmentation was demonstrated using sequencing batch reactors (SBRs) for enhancing 2,4-dichlorophenoxyacetic acid (2,4-D) removal by introducing Cupriavidus necator JMP134 and Escherichia coli HB101 harboring 2,4-D-degrading plasmid pJP4. C. necator JMP134(pJP4) can mineralize and grow on 2,4-D, while E. coli HB101(pJP4) cannot assimilate 2,4-D because it lacks the chromosomal genes to degrade the intermediates. The SBR with C. necator JMP134(pJP4) showed 100 % removal against 200 mg/l of 2,4-D just after its introduction, after which 2,4-D removal dropped to 0 % on day 7 with the decline in viability of the introduced strain. The SBR with E. coli HB101(pJP4) showed low 2,4-D removal, i.e., below 10 %, until day 7. Transconjugant strains of Pseudomonas and Achromobacter isolated on day 7 could not grow on 2,4-D. Both SBRs started removing 2,4-D at 100 % after day 16 with the appearance of 2,4-D-degrading transconjugants belonging to Achromobacter, Burkholderia, Cupriavidus, and Pandoraea. After the influent 2,4-D concentration was increased to 500 mg/l on day 65, the SBR with E. coli HB101(pJP4) maintained stable 2,4-D removal of more than 95 %. Although the SBR with C. necator JMP134(pJP4) showed a temporal depression of 2,4-D removal of 65 % on day 76, almost 100 % removal was achieved thereafter. During this period, transconjugants isolated from both SBRs were mainly Achromobacter with high 2,4-D-degrading capability. In conclusion, plasmid-mediated bioaugmentation can enhance the degradation capability of activated sludge regardless of the survival of introduced strains and their 2,4-D degradation capacity.
    Biodegradation 06/2013; 24(3):343-352. · 2.17 Impact Factor
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    ABSTRACT: Although 4-tert-butylphenol (4-t-BP) is a serious aquatic pollutant, its biodegradation in aquatic environments has not been well documented. In this study, 4-t-BP was obviously and repeatedly removed from water from four different environments in the presence of Spirodela polyrrhiza, giant duckweed, but 4-t-BP persisted in the environmental waters in the absence of S. polyrrhiza. Also, 4-t-BP was not removed from autoclaved pond water with sterilized S. polyrrhiza. These results suggest that the 4-t-BP removal from the environmental waters was caused by biodegradation stimulated by the presence of S. polyrrhiza rather than by uptake by the plant. Moreover, Sphingobium fuliginis OMI capable of utilizing 4-t-BP as a sole carbon and energy source was isolated from the S. polyrrhiza rhizosphere. Strain OMI degraded 4-t-BP via a meta-cleavage pathway, and also degraded a broad range of alkylphenols with linear or branched alkyl side chains containing two to nine carbon atoms. Root exudates of S. polyrrhiza stimulated 4-t-BP degradation and cell growth of strain OMI. Thus, the stimulating effects of S. polyrrhiza root exudates on 4-t-BP-degrading bacteria might have contributed to 4-t-BP removal in the environmental waters with S. polyrrhiza. These results demonstrate that the S. polyrrhiza-bacteria association may be applicable to the removal of highly persistent 4-t-BP from wastewaters or polluted aquatic environments.
    Biodegradation 04/2013; 24(2):191-202. · 2.17 Impact Factor
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    ABSTRACT: Retinoic acid (RA) receptors (RARs) are nuclear receptors whose specific natural ligands are all-trans RA (atRA) and 9-cis RA. RARs control aspects of vision, cell differentiation, immune response, and embryonic development in vertebrates. However excess RAR signaling can cause various teratogenic effects on developing vertebrates. In our previous studies, we have revealed that municipal wastewater generally contains RAR agonists, and identified that the major causative compounds are RAs [atRA and 13-cis RA (13cRA)] and 4-oxo-RAs (4-oxo-atRA and 4-oxo-13cRA), which are oxidative metabolites of RAs. In this study, to elucidate the fates of RAs and 4-oxo-RAs during wastewater treatment, we investigated the variations in their concentrations and the overall RAR agonistic activity in municipal wastewater treatment plants in Osaka, Japan. Results of this study suggested that RAs and 4-oxo-RAs in wastewater can be readily removed by activated sludge treatment, regardless of season and treatment type, and that unidentified RAR agonists are produced during the treatment and persist in the final effluent under certain conditions. However, the current RAR agonist level in the final effluent is unlikely to cause deleterious biological effects.
    Journal of Japan Society on Water Environment 03/2013; 36(2):57-65.
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    ABSTRACT: Selenium is an important rare metal and its recovery from waste and wastewater is necessary for its sustainable utilization. Microbial selenium volatilization is suitable for selenium recovery from industrial wastewater because volatile selenium can be recovered in recyclable forms free from other chemicals. We found that Pseudomonas stutzeri NT-I can aerobically transform selenate, selenite, and biogenic elemental selenium into dimethyldiselenide as well as dimethylselenide; these were temporarily accumulated in the aqueous phase and then transferred into the gaseous phase. The rate of selenium volatilization using strain NT-I ranged 6.5-7.6 μmol/L/h in flask experiments and was much higher than the rates reported previously for other microbes. The selenium volatilization rate accelerated to 14 μmol/L/h in a jar fermenter. Furthermore, 82% of the selenium volatilized using strain NT-I was recovered with few impurities within 48 h in a simple gas trap with nitric acid, demonstrating that strain NT-I is a promising biocatalyst for selenium recovery through biovolatilization from the aqueous phase.
    Water Research 03/2013; 47(3):1361-1368. · 4.66 Impact Factor
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    ABSTRACT: 1,4-Dioxane is a cyclic ether mainly utilized in various chemical and pharmaceutical industries as solvent and reactant. Due to its toxic and persistent nature, 1,4-dioxane is a serious pollutant in the aquatic environment. Although 1,4-dioxane is quite recalcitrant to biodegradation, recent researches have shown 1,4-dioxane biodegradation as a sole carbon and energy source or by co-metabolism with tetrahydrofuran (THF). This study isolated and characterized THF-degrading bacteria to develop a biological process of 1,4-dioxane-containing wastewater treatment. Among five THF-degrading bacteria that were isolated, strain T1 from landfill soil and strains T3 and T5 from activated sludge showed stable co-metabolic degradation of 100 mg/L of 1,4-dioxane when coexisting with 100 mg/L of THF. Strains T1 and T5, identified as Rhodococcus ruber, were further characterized. Both strains could utilize a wide range of carbon sources, and grow at 15 - 35°C and pH 6 - 8. They demonstrated to have inducible THF degrading enzymes, and degraded up to 400 mg/L of THF as a growth substrate although they could not mineralize it. The optimum THF/1,4-dioxane ratios for the co-metabolic 1,4-dioxane degradation by strains T1 and T5 were determined to be 2 to 4. Our results would be useful for the development of biological 1,4-dioxane-containing wastewater treatment system.
    Journal of Water and Environment Technology 02/2013; 11(1):11-19.
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    ABSTRACT: Some strains belonging to the genera Citrobacter and Enterobacter have been reported to produce chitin/chitosan-like bioflocculants (BFs) from acetate. In this study, to investigate the distribution of the BF-producing potential in the genus Citrobacter and to screen stably and highly BF-producing strains, we obtained 36 Citrobacter strains from different culture collection centers, which were distributed among seven species in the genus, and tested for the flocculating activities of their culture supernatants using a kaolin suspension method. As a result, 21 strains belonging to C. freundii (17 strains in 23 strains tested), C. braakii (two in two), C. youngae (one in one), and C. werkmanii (one in two) showed flocculating activity, but this ability was limited to cells grown on acetate. Gas chromatography/mass spectrometry (GC/MS) analysis of the hydrolysates from the BFs of five selected strains indicated that they consisted of glucosamine and/or N-acetylglucosamine, such as the chitin/chitosan-like BF (BF04) produced by Citrobacter sp. TKF04 (Fujita et al. J Biosci Bioeng 89: 40-46, 2000). Gel filtration chromatography using a high-performance liquid chromatography system revealed that the molecular weight ranges of these BFs varied, but the average sizes were all above 1.66 × 10(6) Da.
    Applied Microbiology and Biotechnology 01/2013; · 3.81 Impact Factor
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    ABSTRACT: A co-beneficial system using constructed wetlands (CWs) planted with aquatic plants is proposed for bioethanol production and nutrient removal from wastewater. The potential for bioethanol production from aquatic plant biomass was experimentally evaluated. Water hyacinth and water lettuce were selected because of their high growth rates and easy harvestability attributable to their free-floating vegetation form. The alkaline/oxidative pretreatment was selected for improving enzymatic hydrolysis of the aquatic plants. Ethanol was produced with yields of 0.14-0.17 g-ethanol/ g-biomass in a simultaneous saccharification and fermentation mode using a recombinant Escherichia coli strain or a typical yeast strain Saccharomyces cerevisiae. Subsequently, the combined benefits of the CWs planted with the aquatic plants for bioethanol production and nutrient removal were theoretically estimated. For treating domestic wastewater at 1,100 m(3)/d, it was inferred that the anoxic-oxic activated sludge process consumes energy at 3,200 MJ/d, whereas the conventional activated sludge process followed by the CW consumes only 1,800 MJ/d with ethanol production at 115 MJ/d.
    Water Science & Technology 01/2013; 67(11):2637-44. · 1.10 Impact Factor
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    ABSTRACT: Recently, we showed that Sphingobium fuliginis OMI utilizes 4-tert-butylphenol as a sole carbon and energy source via phenolic ring hydroxylation followed by a meta-cleavage pathway, and that this strain can degrade various alkylphenols. Here, we showed that strain OMI effectively degrades bisphenol A (BPA) via the pathway in which one or two of the phenolic rings of BPA is initially hydroxylated without any modification of the alkyl group that binds the two phenolic rings, and then the aromatic ring is cleaved via a meta-cleavage pathway. Strain OMI also degraded other bisphenols, including bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)sulfone (BPS), 2,2-bis(4-hydroxyphenyl)butane, bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4'-thiodiphenol (TDP), and 4,4'-dihydroxybenzophenone via phenolic ring hydroxylation and meta-cleavage pathway. To our knowledge, this is the first report to describe the aerobic biodegradation of BPS and TDP. The bisphenols degradation pathway of strain OMI is completely different from the known degradation pathways of BPA or bisphenols, and unique in that it does not appear to be influenced by the chemical structure that binds the two phenolic rings. This newly found pathway may play a part in the environmental fate of bisphenols and biotreatment/bioremediation of various bisphenols.
    Environmental Science and Technology 01/2013; 47(2):1017-1023. · 5.48 Impact Factor
  • Japanese Journal of Water Treatment Biology 12/2012; 48(4):145-156.
  • Journal of Environmental Sciences 12/2012; 24(12):2133-2140. · 1.77 Impact Factor

Publication Stats

1k Citations
287.97 Total Impact Points


  • 1995–2014
    • Osaka University
      • • Division of Sustainable Energy and Environmental Engineering
      • • Graduate School of Engineering
      Suika, Ōsaka, Japan
    • Himeji Institute of Technology
      Suika, Ōsaka, Japan
  • 2013
    • Kitasato University
      • Department of Health Science
      Tokyo, Tokyo-to, Japan
  • 2009–2012
    • Vietnam National University, Ho Chi Minh City
      Thành phố Hồ Chí Minh, Ho Chi Minh City, Vietnam
    • Peking University
      • College of Urban and Environmental Sciences
      Peping, Beijing, China
    • Muroran Institute of Technology
      • Department of Applied Sciences
      Muroran, Hokkaido, Japan
  • 2010
    • Kurita Water Industries
      Edo, Tōkyō, Japan
  • 2001–2010
    • University of Yamanashi
      • • Interdisciplinary Graduate School of Medicine and Engineering
      • • Department of Civil and Environmental Engineering
      Kōfu-shi, Yamanashi-ken, Japan
    • Kyoto University
      • Institute for Chemical Research
      Kyoto, Kyoto-fu, Japan
  • 2004–2009
    • National Institute for Environmental Studies
      • Center for Material Cycles and Waste Management Research
      Tsukuba, Ibaraki, Japan
    • National Institute of Livestock and Grassland Science
      Ibaragi, Ōsaka, Japan
  • 2008
    • Osaka City General Hospital
      Ōsaka, Ōsaka, Japan
  • 2005
    • Toyama Prefectural University
      • Department of Environmental Systems Engineering
      Toyama-shi, Toyama-ken, Japan