Shizuo Nakamura

Changes in Microbiota Population during Fermentation of Narezushi as Revealed by Pyrosequencing Analysis

Modern Japanese sushi is derived from an archetype, narezushi, which is made by the fermentation of salted fish with rice. Several studies have demonstrated that lactic acid bacteria are dominantly present in narezushi, but no studies have addressed how microbial composition changes during fermentation. In this study, we examined changes in the microbial population in aji (horse mackerel)-narezushi during fermentation by pyrosequencing the 16S ribosomal RNA gene (rDNA). Ribosomal Database Project Classifier analysis revealed that among the 53 genera present, the Lactobacillus population drastically increased during fermentation, while the populations of other bacteria remained unchanged. Basic Local Alignment Search Tool analysis revealed that L. plantarum and L. brevis were the major species. Comparison with other fermented food microbiota indicated high product-dependency of the bacterial composition, which might have been due to the starter-free fermentation process.

Pyrosequencing Analysis of Microbiota in Kaburazushi, a Traditional Medieval Sushi in Japan

The processing of archetypal Japanese sushi involves microbial fermentation. The traditional sushi kaburazushi, introduced in the middle ages, is made by fermenting salted yellow tail, salted turnip, and malted rice, and is distinguished from the ancient sushi narezushi, made from fish and boiled rice. In this study, we examined changes in the microbial population during kaburazushi fermentation by pyrosequencing the 16S ribosomal RNA genes (rDNA) of the organisms in the fermentation medium. Ribosomal Database Project Classifier analysis identified 31 genera, among which Lactobacillus drastically increased during fermentation (150-fold increment over 8 d), while the relative populations of the other gram-positive bacteria (Staphylococcus and Bacillus) decreased. Basic Local Alignment Search Tool analysis revealed the dominant species to be L. sakei. This organism constituted approximately 90% of Lactobacillus and 79% of total microbiota. The taxonomic diversity and species richness (assayed by Shannon-Weiner Index and Chao 1, respectively) were not significantly different between middle-ages kaburazushi and ancient narezushi. Both types were characterized by the preferential growth of Lactobacillales.

Effective Removal of Cadmium from Fish Sauce Using Tannin

Fish sauce prepared from squid organs contains cadmium (Cd), which may be present at hazardous concentrations. In this study, we report a new, inexpensive, and acceptable method for removing Cd from fish sauce using tannin, which is an approved food additive in Japan. Decreases in Cd concentrations of 13-fold were observed (0.39-0.03 mg/100 mL) by incorporating the soluble Cd into a precipitate generated by tannin treatment. The total nitrogen content, free amino acid content, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and angiotensin I-converting enzyme inhibitory activity of the treated fish sauce were the same as those of the untreated fish sauce.

Tracing microbiota changes in yamahai-moto, the traditional Japanese sake starter

Sake is made from steamed rice, malted rice, and water. Sake production begins with the preparation of a small-scale starter (moto); the quality of moto significantly influences the flavor and richness of sake. In the traditional starter, yamahai-moto, the growth of naturally occurring lactic acid bacteria represses the putrefactive micro-organisms, whereas in the modern starter, sokujo-moto, this is achieved by adding lactic acid. In this study, the successive change in bacterial flora of yamahai-moto was analyzed by pyrosequencing 16S ribosomal RNA genes. Lactobacillus was dominant throughout the process (93–98%). Nitrate-reducing bacteria that have been generally assumed to be the first colonizers of yamahai-moto were scarcely found in the early stage, but Lactobacillus acidipiscis dominated. Lactobacillus sakei drastically increased in the middle stage. This is the first report, though one case study, to show how the early stage microbiota in Japanese yamahai-moto is varyingly controlled without nitrate-reducing bacteria using next-generation sequencing. Graphical abstract Microbiota change during the fermentation of traditional Japanese sake starter yamahai-moto.

Measurements of Molecular Densities in Low Pressure Discharge Plasmas Using Laser Raman Scattering

The possibility of using Raman scattering as a method of molecular density measurements in low pressure discharge plasmas has been investigated. Firstly, the detection limit of Raman signal was examined in low pressure air. It was shown that the Raman scattering from nitrogen molecules was detectable down to 0.06 Pa (particle density of 1.4×1019 m-3) when a photon counting detection system was used. The method was then applied to detect methane and its reaction products in an electron cyclotron resonance plasma operated at a pressure of 50 Pa. Densities of CH4, C2H2, C2H6 and H2 were absolutely determined using the calibrated data of the optical system. Also, it was clearly demonstrated that the gas composition in the discharge was dependent on gas flow rate. These experimental results showed the usefulness of the method for quantitative measurements of molecular densities in processing plasmas.

Observations of the Ferroelastic Domain Structure of MP5O14 (M: La-Tb) by means of Scanning Tunneling Microscope, Electron Spin Resonance and X-Ray Diffraction.

The ferroelasticity of rare earth pentaphosphate, MP5O14 (M: La-Tb) belonging to the species mmmF2/m is studied by scanning tunneling microscope (STM), electron spin resonance (ESR) and X-ray diffraction. The temperature dependence (from room temperature to 180°C) of ferroelastic domain structure and monoclinic β angle of EuP5O14 was obtained by STM and X-ray diffraction (ω scan technique). The spin Hamiltonian parameters of LaP5O14:Cr3+ at 150°C in the para phase obtained from the ESR spectra are gx= gy= gz=1.97, D = 0.45 cm-1 and E = 0.05 cm-1. The principal axes of one of the Cr3+ paramagnetic centers are given by the Eulerian angles =15°, θ=90° and ψ= 0°.

XPS Study of Surface Cation Segregation in Mullite/Zirconia Composites

We have investigated thermally induced cation surface segregation in mullite/zirconia composites with zirconia content ranging from 0% to 100% using x-ray photoelectron spectroscopy (XPS). As a result of thermal annealing at 1000 °C, slight surface Si enrichment with respect to Al was found in the pure mullite sample (0% zirconia). In contrast to the mullite sample, surface segregation in Si, Na, Al and Y was observed in the pure zirconia sample. The segregation behaviour of all the composite samples (10-90 mass% zirconia) is dominated by the zirconia phase. For samples with 10-100 mass% zirconia, segregation leads to the formation of silicates and sodium oxides at the surface.

Electrical resistances and deformation of yttria-stabilized cubic zirconia with alumina

Abstract The effect of addition of alumina to cubic zirconia was investigated in order to explore the possibility of plastic deformation in cubic phase materials and to examine its influence on the electrical conductivity. Zirconia powders with additives of 5.5 mol% yttria and 1, 5, 10 and 20 wt% alumina were made by coprecipitation. Without alumina the grain size increased to about 2 μm after sintering at 1450°C, but only to 0.5 μm for the material with 5 wt% alumina additives. The latter showed a large deformation in spite of the presence of the cubic phase. The frequency dispersion measurements of cubic zirconia with 5.5 mol% Y 2 O 3 added together with additives of 0, 3, 5, 7 and 10 wt% alumina were analyzed using the brick layer model. Two overlapping arcs in cubic zirconia with 5 wt% alumina were observed in the impedance results obtained at 400°C. The arc on the high-frequency side is referred to as the bulk resistance. The other one is related to the grain boundaries. The size of this second arc is dependent on the alumina content. The diameter is large for samples containing no alumina. With increasing alumina content, the size of this arc passes through a minimum at 5 wt% and increases slightly with increasing alumina content.

Atomic Force Microscopy Observation of Ferroelastic Domain Boundary in GdP5O14

The surface structure of GdP 5 O 14 (gadolinium pentaphosphate) with a ferroelastic domain boundary is investigated by AFM (atomic force microscopy) at room temperature in air. The AFM data are obtained for a 1500-nm-square area (400×400 data points) on the (100) surface of the sample. The domain boundary is observed as a zigzag pattern about 300 nm in width. The contour map of the surface shows a unique surface structure in which hollows are aligned along the domain boundary; the hollows have a width of about 600 nm and a depth of 2 nm. If the surface image indicates a strain originating from the domain boundary structure, the thickness of the ferroelastic domain wall of GdP 5 O 14 is estimated to be about 0.6 µm at room temperature.

XHV System for Surface Analysis Using a New Getter to Reduce Hydrogen

For almost the past two decades, surface analysis instruments have maintained an UHV environment which is achieved by UHV pumps. Recently, the XHV environment has been required in surface analysis, but an instrument which has many parts in a vacuum is eventually limited in the baking temperature. To achieve an XHV environment in a surface analysis instrument, H2 is the key component. Thus we tested a nonevaporable getter pump to reduce the amount of H2 and we have measured the residual mass spectrum in a practical instrument using a low outgassing rate mass spectrometer. We obtained a low range of 10-9 Pa using the NEG pump and conventional pumps with relatively low baking temperature. The ion source of the sputter-etching gun was mainly the outgassing of H2 under operating conditions, and hence the pumping speed was not sufficient to maintain the amount of H2 from the ion gun.