Effect of high hydrostatic pressure on enzyme activity in unpasteurized draft sake

ABSTRACT

Unpasteurized draft sake has a potentially high market value, due to its fresh flavor and fruity taste, compared with conventional thermal-pasteurized sake. However, the shelf life of draft sake is limited. To increase the shelf life of draft sake, it is necessary to suppress flavor and taste deterioration resulting from inactivation of enzymes produced by koji-mold. Draft sake was treated with high hydrostatic pressure (HHP) of 200 to 500?MPa at ?7 to 50°C to analyze the inactivation of α-amylases, glucose-forming enzymes, and acid carboxypeptidases. We found significant inactivation of enzymes produced by koji-mold in draft sake subjected to HHP treatment at both high and low temperature. However, HHP treatment at low temperature effectively inactivated enzymes while retaining the fresh flavor and fruity taste of draft sake.     

Adaptations for pressure and temperature effects on loop motion in Escherichia coli and Moritella profunda dihydrofolate reductase

ABSTRACT

Determining how enzymes in piezophilic microbes function at high pressure can give insights into how life adapts to living at high pressure. Here, the effects of pressure and temperature on loop motions of Escherichia coli (Ec) and Moritella profunda (Mp) dihydrofolate reductase (DHFR) are compared via molecular dynamics simulations at combinations of the growth temperature and pressure of the two organisms. Analysis indicates that a flexible CD loop in MpDHFR is an adaptation for cold because it makes the adenosine binding subdomain more flexible. Also, analysis indicates that the Thr113-Glu27 hydrogen bond in MpDHFR is an adaptation for high pressure because it provides flexibility within the loop subdomain compared to the very strong Thr113-Asp27 hydrogen bond in EcDHFR, and affects the correlation of the Met20 and GH loops. In addition, the results suggest that temperature might affect external loops more strongly while pressure might affect motion between elements within the protein.     

Effects of hydrostatic pressure and temperature on catalytic activity of Horse Liver Alcohol Dehydrogenase (HLADH)

Abstract

We have studied the effects of hydrostatic pressure and/or temperature on the catalytic activity of Horse Liver Alcohol Dehydrogenase (HLADH). The Vmax, Km and thermo-dynamical activation volume were determined versus pressure in the range of 0.1 to 225 MPa at ambient temperature (29°C) and at the optimal temperature of HLADH (53°C).     

Generation of microcellular poly(methyl methacrylate) by compressed gases

Abstract

Generation of microcellular poly(methy1 methacrylate) (PMMA) was studied in CO₂ and N₂O at pressures from 2 to 15MPa at three temperatures, 293.2K, 308.2K, and 323.2 K. The average diameter d and average number density N of voids generated by a rapid expansion of compressed gases in PMMA were measured by use of an optical microscope. Effects of gases, temperature, and pressure on the d and N values were examined. Even at pressure below glass transition pressure of PMMA with both gases, voids of diameter being as small as those found at high pressure, 15MPa, were obtained at each temperature. However, the void density of PMMA at lower pressure by both gases was not so good as those obtained at high pressures.     

Decreasing electrical resistivity of gold along the melting boundary up to 5 GPa

ABSTRACT

The electrical resistivity of gold was experimentally measured at high pressures from 2 to 5?GPa and temperatures ～300?K above melting. The resistivity decreased as a function of pressure and increased as a function of temperature as expected. The temperature dependence of resistivity in the solid and liquid phases are comparable to 1?atm results. The observed melting temperatures at each pressure agree well with previous experimental and theoretical studies. The essential result of this study is that resistivity decreases along the pressure-dependent melting boundary, conflicting with a prediction of invariant behavior as reported in the literature. This result is discussed in terms of the interaction between s and d-bands as both pressure and temperature increase along the melting boundary. The thermal conductivity of gold was calculated from the measured electrical resistivity using the Wiedemann-Franz law. The temperature-induced effect on the thermal conductivity at high temperatures is as expected in both the solid and liquid phase while the pressure-effect shows some variability.     

Variations of lattice constants and thermal expansion coefficients of indium at high pressure and high temperature

ABSTRACT

The effects of pressure and temperature on the lattice constants and thermal expansion coefficients of Indium were studied up to 18.6?GPa and 506?K based on in situ X-ray diffraction method with an externally heated diamond anvil cell. The results show that the measured axial ratio (c/a) decreases with increasing temperature and its temperature dependence decreases with increasing pressure. The thermal expansion coefficient of the a-axis decreases with increasing pressure up to 7?GPa and remains almost constant above 7?GPa, whereas that of the c-axis increases monotonously with pressure and changes from negative to positive at around 7?GPa. The observed behavior suggests that temperature reduces the tetragonal distortion on the lattice, and its effect is dominant below 7?GPa; in contrast, pressure enhances lattice distortion, and tends to have a stronger effect above 7?GPa.     

Some comparative thermodynamic characteristics of fullerite and various covalent elements

Measurements of the specific heat and elastic wave velocities for a C₆₀ fullerene sample treated at high pressure and temperature are used to estimate the Debye temperature and the function ΔC=C _p−C _v, and also to calculate the thermal expansion work in the ideal approximation. Similar calculations were made for graphite, diamond, silicon, germanium, and various refractory metals. The results were used to draw qualitative conclusions on the structural stability of a new material obtained from fullerene C₆₀ which possesses extremely high hardness. Fiz. Tverd. Tela (St. Petersburg) 40, 1387–1389 (July 1998)     

Stability diagram of rice starch as determined with FTIR

Abstract

In this study, we followed in situ changes in the infrared spectrum at different conditions of pressure and temperature. Cooperative changes were observed when temperature or pressure was increased. Plotting the midpoints of cooperative transitions in a pressure-temperature plane results in an outline similar to the stability curve of proteins. We can assume that it is the first time that the pressure-temperature dependent gelation diagram is determined in situ for starch.     

Structural study of pressure-induced magnetic phase transitions in manganites Pr0.7Ca0.3Mn1-y Fe y O3 (y?=?0, 0.1)

A crystal and magnetic structure of manganites Pr_0.7Ca_0.3Mn_1?y Fe _y O₃ (y = 0, 0.1) has been studied by means of powder neutron diffraction at pressures up to 4 GPa in the temperature range 15-300 K. Under high pressure, an appearance of A-type antiferromagnetic state in both systems was observed. Both compounds exhibit anisotropic compression of the lattice which leads to the apical compression of MnO₆ octahedra along the crystallographic b-axis. The calculated from obtained structural data pressure dependence of the charge-carrier bandwidth is in a qualitative agreement with observed pressure behavior of insulator-metal transition temperature within the framework of the double-exchange model.     

Pressure induced metallization of the antiferromagnetic-insulator CoI

Abstract

High pressure electrical measurements were conducted in the antiferromagnetic insulator CoI, using a miniature Diamond Anvil Cell (DAC). The existence of a Mott Transition predicted from high pressure ¹²⁹I Mgssbauer Spectroscopy (MS)¹ has been verified. At about 8 GPa the system becomes metal1ic as evidenced by the temperature behavior of the conductivity. The conductivity at room temperature, however, still increases with increasing pressure, leveling off at 11 GPa. The metallic behavior in the 8 -11 GPa is explained by coexistence of metallic and insulating clusters via a percolating process. Above 11 GPa the material is completely metallic. This mechanism is consistent with the MS findings.     

High-pressure phases of plutonium monoselenide studied by X-ray diffraction

Abstract

Plutonium monoselenide was studied under high pressure up to 47 GPa, at room temperature, using a diamond anvil cell in an energy dispersive X-ray diffraction facility. At ambient pressure, PuSe has the NaC1-type (B1) structure. The compound has been found to undergo a second-order crystallographic phase transition at around 20 GPa. This phase can be described as a distorted B1 structure, with a rhombohedral symmetry. PuSe transforms to a new phase at around 35 GPa, which can be indexed in the cubic CsCl-type (B2). The volume collapse at this phase transition is 11%. When releasing pressure, we observed a strong hysteresis to the inverse transformation down to 5 GPa. From the pressure-volume relationship, the bulk modulus has been determined to B ₀ = 98 GPa and its pressure derivative as B ₀ = 2.6. These results are compared to those obtained with other actinide monmictides and monochalcogenides.     

Phase diagram of aqueous solution at high pressure and low temperature

Abstract

This paper presents a constant mass high pressure isothermal calorimeter and describes the range of applications that this type of equipment can deal with. As an example, the thermophysical properties of an aqueous solution of MgSO₄ at low temperature and at high pressure have been investigated. The main results showed that the phase change heat of the solution decreased with increasing pressure and the phase change temperature of the eutectic concentration was depressed under high pressure. Those changes could be related to the MgSO₄ solubility and to water latent heat changes.     

Pressure induced anisotropic magnetovolume phenomena in Lu2Fe17 Intermetallics

Magnetisation and magnetic susceptibility of a Lu₂Fe₁₇ single crystal have been studied under hydrostatic pressure up to 1.2 GPa at temperatures down to 5 K using a SQUID magnetometer. The ferromagnetic phase of Lu₂Fe₁₇ is suppressed rapidly above a critical pressure P _C = 0.4 GPa in the whole temperature range below the critical temperature T _C . A magnetic phase diagram of Lu₂Fe₁₇ has been constructed using results of the magnetic susceptibility measurements under pressure. A pressure induced incommensurate antiferromagnetic phase exhibits metamagnetic transitions with the increasing critical magnetic field H _C under pressure. Taking into account recent neutron diffraction data, the pressure induced anisotropic changes of the lattice parameters of the Lu₂Fe₁₇ are discussed.     

Effects of pressure on protein structure

Abstract

The main targets for the pressure induced changes in proteins are those regions primarily stabilised by hydrophobic and electrostatic interactions, since hydrogen bonds are almost pressure insensitive. Thus pressure treated proteins may well have very different structures to their native or heat treated counterparts and as a consequence different functionalities. This concept is used to discuss how pressure can modify the foaming, emulsifying and gelling properties of some food proteins and can also be used to modify the activity of some enzymes of importance in dictating food quality.     

In-situ X-ray diffraction study on β-CrOOH at high pressure and high-temperature

ABSTRACT

High pressure hydrous phases with distorted rutile-type structure have attracted much interest as potential water reservoirs in the Earth’s mantle. An in-situ X-ray diffraction study of β-CrOOH was performed at high pressures of up to 6.2?GPa and high-temperatures of up to 700?K in order to clarify the temperature effect on compression behaviors of β-CrOOH. The P-V-T data fitted to a Birch–Murnaghan equation of state yielded the following results: isothermal bulk modulus K_T0?=?191(4)?GPa, temperature derivative (?K_T/?T)_P?=??0.04(2)?GPa?K^?1, and volumetric thermal expansion coefficient α?=?3.3(2)?×?10^?5?K^?1. In this study, at 300?K, the a-axis became less compressible at pressures above 1–2?GPa. We found that the pressure where the slopes of a/b and a/c ratios turned positive increased with temperature. This is the first experimental study indicating the temperature dependence of the change in the axial compressibility in distorted rutile-type M³⁺OOH.     

Raman spectra of forsterite and fayalite at high pressures and room temperature

Abstract

Raman spectra of the two pure end-members of olivine (forsterite and fayalite) were studied at high pressures and room temperature in a diamond-anvil cell using both single-crystals and polycrystalline samples in pressure mediums of either an ethanol-methanol mixture or H₂O. Variations with pressure were studied up to 170kbar for fayalite and to 300kbar for forsterite. Two intensive Raman bands of fayalite were definitely observable at high pressures, but only one of them can be reliably determined. Both have a linear variation within experimental uncertainty. Because of interference from the high spectral background, we found that nearly all the weak bands of forsterite could not be reliably determined at high pressures. However, the pressure variations of all bands of forsterite which can be reliably determined are non-linear. The rates of frequency change for the intense bands of forsterite determined in the present experiment are consistent with those of natural forsterites determined by Besson et al. ¹ and Gillet et al. ², but are in a slight discordance with those reported by Chopelas³. Furthermore, there is no evidence for the olivine ? spinel phase transition occurring at room temperature.     

High pressure raman study of Y-124

In this work, a micro-Raman study under high hydrostatic pressure (up to ～5.5 GPa) has been carried on YBa₂Cu₄O₈ and Y(Ba, Sr)₂Cu₄O₈ single crystals at room temperature. In both samples, seven strong modes, of A_g symmetry, and one weak, of B_3g symmetry, have been observed and examined in connection with previously published results concerning YBa₂Cu₄O₈. With the Sr substitution for Ba, the ambient pressure measurements show an upward shift in energy for all modes, except those that involve vibrations of the plane and apex oxygen atoms. With increasing hydrostatic pressure all phonons shift to higher energies. Anomalous nonlinear pressure behaviour has been observed for three phonons, which is correlated with the pressure dependence of T _c of these compounds.     

High-pressure optical studies on R-line fluorescence lifetime in Al2O3:V2+

The effect of high hydrostatic pressure (up to 10.3?GPa) at room temperature on fluorescence lifetime τ for R line (²E→⁴A₂ transition) in ruby Al₂O₃:V²⁺ was studied. The performed studies show the linear increase of τ with increasing pressure. At 10.3?GPa, τ is about 1.36 times higher than at ambient pressure. The obtained trend was explained by a model which considered the effect of pressure on τ through an induced change of line position, inter-ionic distance, compressibility, and molecular polarizability. A good agreement between the calculated and experimental values for τ was obtained.     

Kinetics of the pressure-induced first-order phase transformation of RbJ

Abstract

We have studied at room temperature the kinetics of the phase transformation in RbJ from the 6-coordinated NaCl to 8-coordinated CsCl type structure by energy dispersive diffraction technique with synchrotron radiation. The time resolution was between 0.3 and 1.0 sec. The measurements were analyzed by fitting the Avrami equation to the measured data. The final transformation pressure is p_tr = 3.74 ± 0.05 kbar obtained by extrapolating k, the transformation constant in the Avrami equation, to k=0.The growth constant n is (n) = 1 indicating growth of the new high pressure phase on the crystal faces. The transformation can be interpreted as a dilatational transformation, according to Buerger.