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adsorption 
lattice defect sites of Prussian blue filled with coordination and crystallization water moleculesIshizaki, Manabu*; Akiba, Sae*; Otani, Asako*; Hoshi, Yuji*; Ono, Kenta*; Matsuba, Mayu*; Togashi, Takanari*; Kanaizuka, Katsuhiko*; Sakamoto, Masatomi*; Takahashi, Akira*; et al.
Dalton Transactions, 42(45), p.16049 - 16055, 2013/12
Times Cited Count：179 Percentile：99.58(Chemistry, Inorganic & Nuclear)We have revealed the fundamental mechanism of specific Cs adsorption into Prussian blue (PB) in order to develop high-performance PB-based Cs adsorbents in the wake of the Fukushima nuclear accident. We compared two types of PB nanoparticles with formulae of Fe
[Fe
(CN)
]3
xH
O (x = 10-15) (PB-1) and (NH)0.70Fe1.10[Fe(CN)]1.7HO (PB-2) with respect to the Cs adsorption ability. The synthesised PB-1, by a common stoichiometric aqueous reaction between 4Fe
and 3[Fe(CN)]
, showed much more efficient Cs adsorption ability than did the commercially available PB-2.
Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*
Geomicrobiology Journal, 29(5), p.470 - 476, 2012/05
Times Cited Count：6 Percentile：17.26(Environmental Sciences)We screened 4908 non-essential gene deletion mutant yeast strains for uranium sensitivity and low accumulation by growth in agar medium containing uranium. All mutant strains grew successfully on agar media containing 0 or 0.5 mM uranium for one week at 30 centigrade. Thirteen strains with single gene deletions showed reduced growth in the agar medium containing 0.5 mM uranium and were identified as uranium-sensitive mutant strains. The phosphate transporter genes of PHO86, PHO84, PHO2, and PHO87 were among the deleted genes in the uranium-sensitive mutant strains, suggesting that genes concerned with phosphate transport contribute to uranium tolerance. Seventeen single-deletion strains showed lower uranium accumulation than the wild-type after exposure to agar medium containing 0.5 mM uranium, and were identified as mutant strains with low uranium accumulation.
Morita, Takami*; Niwa, Kentaro*; Fujimoto, Ken*; Kasai, Hiromi*; Yamada, Haruya*; Nishiuchi, Ko*; Sakamoto, Tatsuya*; Godo, Waichiro*; Taino, Seiya*; Hayashi, Yoshihiro*; et al.
Science of the Total Environment, 408(16), p.3443 - 3447, 2010/06
Times Cited Count：13 Percentile：32.9(Environmental Sciences)Iodine-131 (
I) was detected in brown algae collected off the Japanese coast. The maximum measured specific activity of I in brown algae was 0.37
0.010 Bq/kg-wet. Cesium-137 (
Cs) was also detected in all brown algal samples used in this study. There was no correlation between specific activities of I and Cs in these seaweeds. Low specific activity and minimal variability of Cs in brown algae indicated that past nuclear weapon tests were the source of Cs. Although nuclear power facilities are known to be pollution sources of I, there was no relationship between the sites where I was detected and the locations of nuclear power facilities. Most of the sites where I was detected were near big cities with large populations. On the basis of the results, we suggest that the likely pollution source of I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.
Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Ozaki, Takuo; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*
Geomicrobiology Journal, 27(3), p.225 - 230, 2010/04
Times Cited Count：18 Percentile：22.77(Environmental Sciences)The recent research results on the interation of heavy-elements and microorganisms are shown. (1) Adsorption of Pu(IV), Th(IV) and Eu(III)-DFO complexes on bacteria, (2) Biodegradation of Eu(III) in the presence of malic acids.
Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*
Journal of Nuclear Science and Technology, 46(1), p.55 - 59, 2009/01
Times Cited Count：8 Percentile：49.4(Nuclear Science & Technology)Model analysis of the transformation of Pu(VI) in a mixture of a common soil bacterium, Bacillus subtilis, and kaolinite clay was carried out. When we assumed in the model analysis that reduction rate of Pu(V) to Pu(IV) was higher on B. subtilis than on kaolinite, the estimated fractions of Pu in the solution and in the mixture, oxidation states of Pu in the solution and in the mixture were in good agreement with the measured ones. On the contrary, assumption that reduction rate of Pu(V) to Pu(IV) was the same on kaolinite as on 
gave wrong prediction of Pu association with the mixture. These results strongly suggested the electron transfer from the bacteria to Pu(V) on the bacterial cell to be reduced to Pu(IV) during the accumulation of Pu(VI) to the mixture.
Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Nankawa, Takuya; Sakamoto, Fuminori; Sakai, Takuro; Suzuki, Yoshinori; Francis, A. J.*
Chemical Geology, 253(1-2), p.23 - 29, 2008/07
Times Cited Count：28 Percentile：55.04(Geochemistry & Geophysics)We examined the changes in the chemical states of Ce(III) during the formation of manganese oxide occasioned by Mn(II)-oxidizing bacteria. The oxidation states of Ce and Mn then were measured by X-ray Absorption Near Edge Structure (XANES). We also determined the elemental distributions in the bacteria and precipitates by Scanning-Proton Induced X-ray Emission (S-PIXE). We found that the precipitation of Ce is preceded by its accumulation by the bacterium, followed by its oxidization to Ce(IV) by the Mn(III, IV)-containing precipitates that the bacteria generate.
in response to uranium exposureSakamoto, Fuminori; Nankawa, Takuya; Kozai, Naofumi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.; Onuki, Toshihiko
Journal of Nuclear and Radiochemical Sciences, 8(2), p.133 - 136, 2007/10
Protein expression of grown in the medium containing 
U(VI) and 
U(VI) was examined by two-dimensional gel electrophoresis. 
of BY4743 was grown in medium containing U of 0, 2.0, and 5.0 
10
M or U of 2.5 10
(radioactivity was higher by 350 times than 2.0 10 M U) and 5.0 10 M for 112 h at 30
C. The growths of the yeast grown in the above media were in the following order: control 
2.5 10 M U 2.0 10 M U 5.0 10 M U 5.0 10 M U. This result indicated that not only radiological but also chemical effect of U reduced the growth of the yeast. The concentrations of U in the medium containing U or U decreased, suggesting U accumulation by the yeast cells. The 2-D gel electrophoresis analysis showed the appearance of several spots after exposure to U or to U but not in the control containing no uranium. These results show that the yeast cells exposed to U express several specific proteins.
Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori*; Francis, A. J.
Environmental Science & Technology, 41(9), p.3134 - 3139, 2007/05
Times Cited Count：32 Percentile：56.92(Engineering, Environmental)We investigated the interactions of Pu(VI) with Bacillus subtilis, kaolinite clay, and a mixture of the two to determine and delineate the role of the microbes in regulating the environmental mobility of Pu. The amount of Pu sorbed by B. subtilis increased with time, but had not reached equilibrium in 48 h, whereas equilibrium was attained in kaolinite within 8 h. After 48 h, the oxidation state of Pu in the solutions exposed to B. subtilis and the mixture had changed to Pu(V), whereas the oxidation state of Pu associated with B. subtilis and the mixture was Pu(IV). In contrast, there was no change in the oxidation state of Pu in the solution or on kaolinite after exposure to Pu(VI). SEM-EDS analysis indicated that most of the Pu in the mixture was associated with B. subtilis. These results suggest that Pu(IV) is preferably sorbed to bacterial cells in the mixture, and that Pu(VI) is reduced to Pu(V) and Pu(IV).
Onuki, Toshihiko; Yoshida, Takahiro*; Nankawa, Takuya; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori*; Francis, A. J.*
Journal of Nuclear and Radiochemical Sciences, 6(1), p.65 - 67, 2005/07
no abstracts in English
Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Yoshida, Takahiro*; Suzuki, Yoshinori*; Francis, A. J.*
no journal, ,
no abstracts in English
Yoshida, Takahiro*; Ozaki, Takuo; Sakamoto, Fuminori; Kozai, Naofumi; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*; Onuki, Toshihiko
no journal, ,
no abstracts in English
Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Sakamoto, Fuminori; Kozai, Naofumi; Nankawa, Takuya; Suzuki, Yoshinori*; Francis, A. J.*
no journal, ,
no abstracts in English
Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Ozaki, Takuo; Nankawa, Takuya; Suzuki, Yoshinori; Iefuji, Haruyuki*; Francis, A. J.
no journal, ,
no abstracts in English
Ozaki, Takuo; Nankawa, Takuya; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori; Francis, A. J.
no journal, ,
The interaction of actinides with microorganisms has been extensively studied to elucidate migration behavior of actinides in the environments. However, the mechanisms of interaction of microorganisms and actinides are poorly understood. We have been conducting basic on microbial accumulation of actinides in order to elucidate the environmental behavior of actinides under relevant conditions. Effect of desferrioxamine B (DFO) on the sorption of Pu(IV), Th(IV) and Eu(III) (analog for Am(III)) on Pseudomonas fluorescens was studied. In the presence of DFO the sorption of Pu(IV), Th(IV) and Eu(III) on the cells increased with a decrease in pH from 7 to 4. In contrast, without DFO most of Pu(IV), Th(IV) and Eu(III) were precipitated from solution. Adsorption of DFO on the cells was negligible in the solution with and without metals. Adsorption of Pu(IV), Th(IV) and Eu(III) on P. fluorescens cells decreased in the order Eu(III) Th(IV) Pu(IV), which corresponds to increasing stability constant of the DFO complexes. These results indicate that Th(IV), Pu(IV) and Eu(III) dissociate when in contact with cells, after which the metals are adsorbed. Mechanism of uranium(VI) mineralization by the yeast Saccharomyces cerevisia e was examined by batch experiment at pH 3.2. FESEM-EDS, TEM, and visible diffuse reflectance spectrometry revealed the formation of H-autunite, HUOPO 4HO on the yeast cells. Thermodynamic calculations suggest that the chemical compositions of the solutions were undersaturated with respect to H-autunite, but were supersaturated with ten-times more U(VI) and P than were actually observed. Apparently, the sorbed U(VI) on the cell surfaces reacts with Preleased from the yeast to form H-autunite by local saturation. These findings indicate that the yeast's cell surfaces, rather than the bulk solution, offer the specific conditions for this geochemical process. We studied the effect of Eu(III) on the degradation o
Onuki, Toshihiko; Ozaki, Takuo; Yoshida, Takahiro*; Nankawa, Takuya; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori*; Francis, A. J.
no journal, ,
We have been conducting basic studies on the microbial accumulation of actinides in order to understand the environmental behavior of actinides under relevant conditions. The effect of bacterial exudates on the sorption of Eu(III) and Cm(III) by Chlorella vulgaris was studied by a batch method. The pH dependence of log Kd of Eu(III) and Cm(III) for cellulose, major component of C. vulgaris cell, differed from that for C. vulgaris. However, thelog Kd of Eu(III) and Cm(III) for cellulose in the solution containing exudates from C. vulgaris cells in a 0.5% NaCl solution showed a similar pH dependence to that by C. vulgaris. These results suggests that exudates affect on the sorption of Eu(III) and Cm(III) on C. vulgaris.
Kozai, Naofumi; Suzuki, Yoshinori; Nankawa, Takuya; Sakamoto, Fuminori; Onuki, Toshihiko; Francis, A. J.
no journal, ,
One of the biomolecules at the cell surface of bacteria to bind uranium is protein. To clarify adsorption mechanism of uranium on protein, this study investigated the adsorption of uranium (VI) on protein by use of silica particles modified with a cell surface protein, protein A. Unmodified silica particles (Si-OH) and the silica particles on which one kind of the following functional groups, -COOH, -NH, and -OPO
H, was fixed were also used as reference. The adsorption pf uranyl ions on the silica particles modified with amino group and phosphoric group are the greatest. The sorption behavior of uranyl ions on silica particles modified with protein A was similar to those on the silica particles modified with amino group and phosphoric group. However, because the content of phosphoric group in protein A is low, amino group is thought to be the major adsorption site of uranyl ions on the protein A-modified particles.
Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.
no journal, ,
In this study, we carried out experiments and model analysis of the transformation of Pu(VI) in a mixture of a common soil bacterium, Bacillus subtilis, and clay (kaolinite). A simplified kinetic model was proposed to describe the association of Pu with the mixture. In the model Pu(VI) and Pu(V) are assumed to be adsorbed on B. subtilis and kaoloinite. Pu(VI) is reduced to Pu(V) only in the solution because of simplification of the model, even though the reduction of Pu(VI) is actually occurred in solution, on B. subtilis and kaoloinite. Comparison of model estimation with experimental results suggest that kinetic simple model described the association of Pu(VI) with the mixture, and suggested that reduction of Pu(V) to Pu(IV) was mainly proceeded on the surface of B. subtilis in the mixture.
Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Sakamoto, Fuminori; Kozai, Naofumi; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.
no journal, ,
We have been conducting basic scientific research on microbial interactions with actinides in order to elucidate the environmental behavior of actinides under relevant microbial process conditions. Adsorption of Pu(IV)-desferrioxamine B (DFO) on bacteria indicate that Pu(IV) is dissociated by contact with cells, after which Pu(IV) is adsorbed. Study on reduction of Pu(IV) in the presence of citric acid at pH 7.0 suggested that Pu(IV) is reduced to Pu(III) by the activity of sulphate reducing bacteria. Analysis of the U(VI)-bearing precipitates by FESEM-EDS, TEM, and visible diffuse reflectance spectrometry demonstrated the presence of H-autunite, HUOPO;4HO and thermodynamic calculations suggest that the chemical compositions of the solutions were undersaturated with respect to H-autunite. The yeast's cell surfaces, rather than the bulk solution, offer the specific conditions for this geochemical process.
exposed by uranium(VI)Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Francis, A. J.
no journal, ,
Yeast is known to accumulate U(VI). This suggests that yeast may be utilized as bisorbents for removing U from U mine tailings wastewater. It is reported that cell surface sorption, extracellular accumulation and intracellular accumulation are predominant processes in the biosorption by yeast. It is suggested that some proteins function important role for biosorption. In the present study, we explored the proteins expressed by exposure of yeast to U(VI) solutions of different concentrations. As the concentration of U increase, some proteins are gradually expressed. These proteins are TPI1 and SOD1 proteins. TPI1 protein is related to glycolytic pathway and catalyzes the reversible interconversion of glyceraldehyde 3-phosphate and dihydroxyacetone phospate. SOD1 protein catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. These results indicate that SOD protein and some enzymes in the system of glycolytic pathway are related with U accumulation by S. cerevisiae.
Kozai, Naofumi; Suzuki, Yoshinori; Nankawa, Takuya; Sakamoto, Fuminori; Onuki, Toshihiko; Francis, A. J.
no journal, ,
One of the biomolecules at the cell surface of bacteria to bind uranium is protein. To clarify adsorption mechanism of uranium on protein, this study investigated the adsorption of uranium(IV) on silica particles modified with functional groups. Uranyl ions, which are the predominant uranium(IV) species below pH 4, were not adsorbed on unmodified particles, but well adsorbed on the particles modified with phosphoric groups and amino groups. A good linear relationship was found between the complexation constants of uranyl ion for amino groups with different acid dissociation constants and the acid dissociation constants of the amino groups.
