Effects of High Hydrostatic Pressure on the Distribution of Oligosaccharides, Pinitol, Soysapapogenol A, and Fatty Acids in Soybean.

The effects of high hydrostatic pressure (HHP) treatment (100-600 MPa for 10-60 min) and thermal treatment (boiling for 10-60 min) on oligosaccharides, pinitol, and soyasapogenol A as taste ingredients in soybean (Glycine max (L.) Merr.) (cv. Yukihomare) were evaluated. Additionally, soybean-derived fatty acids such as α-linolenic acid, linoleic acid, oleic acid, palmitic acid, and stearic acid in pressurized soybeans were quantitatively analyzed. Sucrose, stachyose, and raffinose concentrations were decreased in all tested pressure and time combinations; however, pinitol concentrations were increased by specific pressure and time combinations at 100-400 MPa for 10-60 min. While the soyasapogenol A content in boiled soybeans decreased with increasing boiling time, that of pressurized soybeans was altered by specific pressure and time combinations. At the lower pressure and shorter time combinations, the essential fatty acids such as α-linolenic acid and linoleic acid showed higher contents. Stearic acid and oleic acid contents of pressurized soybeans increased at mild pressure levels (300-500 MPa). In contrast, the combination of higher pressure and longer time results in lower essential fatty acid contents. Non-thermal-pressurized soybeans have the potential to be a high-value food source with better taste due to the enrichment of low molecular weight components such as pinitol, free amino acids, and the reduction of isoflavones and Group A soyasapogenol.

Enzyme from Padina arborescens Holmes Synthesizes Parinaric Acid, a Conjugated Tetraenoic Fatty Acid, from α-Linolenic Acid.

Conjugated fatty acids have anticancer effects. Therefore, the establishment of a synthetic method for conjugated fatty acids is important for overcoming cancer. Here, we attempted to synthesize conjugated fatty acids using enzymes extracted from seaweeds containing these fatty acids. Lipids from 12 species of seaweeds from the seas around Japan were analyzed, and Padina arborescens Holmes was found to contain conjugated fatty acids. Then, we synthesized parinaric acid, a conjugated tetraenoic acid, from α-linolenic acid using the enzyme of P. arborescens. This method is expected to have a variety of potential applications for overcoming cancer.

Amino Acids Supplied through the Autophagy/Endocytosis Pathway Promote Starch Synthesis in Physcomitrella Protonemal Cells.

The physiological implications of autophagy in plant cells have not been fully elucidated. Therefore, we investigated the consequences of autophagy in the moss Physcomitrella by measuring biochemical parameters (fresh and dry weights; starch, amino acid, carbohydrate, and NH3 content) in wild-type (WT) and autophagy-deficient atg5 Physcomitrella cells. We found higher starch levels and a higher net starch synthesis rate in WT cells than in atg5 cells cultured in a glucose-containing culture medium, whereas net starch degradation was similar in the two strains cultured in a glucose-deficient culture medium. Additionally, the treatment of cells with the autophagy inhibitor 3-methyladenine suppressed starch synthesis. Loading bovine serum albumin into atg5 cells through endocytosis, i.e., supplying proteins to vacuoles in the same way as through autophagy, accelerated starch synthesis, whereas loading glutamine through the plasma membrane had no such effect, suggesting that Physcomitrella cells distinguish between different amino acid supply pathways. After net starch synthesis, NH3 levels increased in WT cells, although the change in total amino acid content did not differ between WT and atg5 cells, indicating that autophagy-produced amino acids are oxidized rapidly. We conclude that autophagy promotes starch synthesis in Physcomitrella by supplying the energy obtained by oxidizing autophagy-produced amino acids.

Effect of high pressure on the saccharification of starch in the tuberous root of sweet potato (Ipomoea batatas).

We analyzed the effect of high hydrostatic pressure (HHP) treatment on reducing sugar production in the tuberous root of sweet potato (Ipomoea batatas), based on pressure-gelatinization of starch and subsequent saccharification by internal amylases. HHP treatment at up to 600MPa at ambient temperature for 10min did not apparently affect the reducing sugar concentration in tuberous root. However, HHP treatment at 100 to 500MPa and 60°C or 70°C for 10min increased reducing sugar concentration as both the pressure and temperature increased. The reducing sugar concentration after HHP treatment at 500MPa and 70°C for 10min was roughly comparable to that of the thermal treatment control (80°C for 10min under atmospheric pressure). HHP treatment enabled the gelatinization and enzymatic saccharification of starch in the tuberous root of sweet potato, at a lower temperature than required by thermal treatment at atmospheric pressure.

Effects of High Hydrostatic Pressure on Water Absorption of Adzuki Beans.

The effect of high hydrostatic pressure (HHP) treatment on dried soybean, adzuki bean, and kintoki kidney bean, which are low-moisture-content cellular biological materials, was investigated from the viewpoint of water absorption. The samples were vacuum-packed with distilled water and pressurized at 200 MPa and 25 °C for 10 min. After the HHP treatment, time courses of the moisture contents of the samples were measured, and the dimensionless moisture contents were estimated. Water absorption in the case of soybean could be fitted well by a simple water diffusion model. High pressures were found to have negligible effects on water absorption into the cotyledon of soybean and kintoki kidney bean. A non-linear least square method based on the Weibull equation was applied for the adzuki beans, and the effective water diffusion coefficient was found to increase significantly from 8.6 × 10-13 to 6.7 × 10-10 m²/s after HHP treatment. Approximately 30% of the testa of the adzuki bean was damaged upon HHP treatment, which was comparable to the surface area of the testa in the partially peeled adzuki bean sample. Thus, HHP was confirmed to promote mass transfer to the cotyledon of legumes with a tight testa.

Enzymatic production of γ-aminobutyric acid in soybeans using high hydrostatic pressure and precursor feeding.

The effects were investigated of the glutamic acid (Glu) substrate concentration on the generation and kinetics of γ-aminobutyric acid (GABA) in soybeans treated under high hydrostatic pressure (HHP; 200 MPa for 10 min at 25 °C). The conversion of Glu to GABA decreased with increasing initial Glu concentration in the soybeans. The crude glutamate decarboxylase (GAD) obtained from the HHP-treated soybeans showed substrate inhibition. The GABA production rate in the HHP-treated soybeans fitted the following substrate inhibition kinetic equation: v0=(VmaxS0)/(Km+S0+(S0)2/Ki). The Km value for the HHP-treated soybeans was significantly higher than that of the untreated soybeans. The Km values in this study show the affinity between Glu and GAD, and indicate that the HHP-treated soybeans had lower affinity between Glu and GAD than the untreated soybeans. GAD extracted from the HHP-treated soybeans showed a similar value to that in the HHP-treated soybeans. The intact biochemical system was so damaged in the HHP-treated soybeans that it showed substrate inhibition kinetics similar to that of the extracted GAD. The combination of HHP and precursor feeding proved to be a novel tool that can be used to increase the concentration of a target component.

High-throughput method for a kinetics analysis of the high-pressure inactivation of microorganisms using microplates.

Using microplates as pressure and cultivation vessels, a high-throughput method was developed for analyzing the high-pressure inactivation kinetics of microorganisms. The loss of viability from a high-pressure treatment, measured based on the growth delay during microplate cultivation, showed reproducibility with the conventional agar plate method and was applicable for the kinetics analysis.

Kinetic analysis of E. coli inactivation by high hydrostatic pressure with salts.

Inactivation of E. coli by high hydrostatic pressure (250 to 400 MPa) with salts was investigated based on kinetic analysis. At concentrations from 0.074 to 0.145 M and from 0.240 to 0.290 M, both the absolute activation volumes and the preexponential factors were similar in KCl, NaCl, and LiCl solutions, suggesting that pressure inactivation is not salt-specific. On the other hand, in the intermediate salt-concentration range of 0.145 to 0.240 M, inactivation kinetics in the presence of the Na(+) and K(+) differed significantly from those in the presence of Li(+) (P < 0.05). In this concentration range, effect of salt stress and osmotic stress differed significantly from those in concentrations below 0.145 M or above 0.240 M. The cellular response to pressure varies with salt type and salt concentration. These novel findings provide important clues to distinguish between salt stress and osmotic stress in the inactivation of E. coli.

Generation of free amino acids and gamma-aminobutyric acid in water-soaked soybean by high-hydrostatic pressure processing.

The effects of high-hydrostatic pressure processing (HPP) on soybean cotyledon as a cellular biological material were investigated from the viewpoints of the cell structure and enzyme reaction system. Damage to cell structure was evaluated by measuring dielectric properties using the Cole-Cole arc, the radius of which decreased as pressure level increased. Results suggested that cell structure was damaged by HPP. The distribution of free amino acids was measured after HPP (200 MPa) of soybean soaked in water or sodium glutamate (Glu) solution. HPP resulted in high accumulation of free amino acids in water-soaked soybean, due to proteolysis. HPP of soybean in Glu solution caused higher accumulation of gamma-aminobutyric acid, suggesting that both proteolysis and specific Glu metabolism were accelerated by HPP. We concluded that HPP partially degraded cell structure and accelerated biochemical reactions by allowing enzyme activities to remain. These events can be considered "high-pressure induced transformation" of soybean.

Isolation and characterization of barosensitive mutants of Saccharomyces cerevisiae obtained by UV mutagenesis.

Using UV mutagenesis, 2 high-pressure (HP) sensitive (barosensitive) mutants of Saccharomyces cerevisiae were obtained. The HP inactivation of the mutants, as well as their parent strains, followed 1st-order kinetics in the range of 175 to 250 MPa within 600 s. Both mutants showed larger 1st-order inactivation rate constant values or significant loss of viabilities, compared with their parent strains in the pressure range tested. The inactivation rate constant value of one of the mutants was comparable with that of a previously reported highly barosensitive strain, which was generated by deletion of hsp104 in a trehalose deficient strain. The activation volume values of HP inactivation reactions in the 2 mutants were apparently equivalent with those of their parent strains. This suggested that the mutation did not bring drastic volume changes of the key molecules for HP inactivation. Their auxotrophic properties, growth, and ethanol fermentation were identical in mutant and parent strains. The mutants could therefore be useful for fermentations where control by HP processing is desired.

Effect of the grain boundary of ice crystals in a frozen gelatin solution on the dielectric properties at a subzero temperature.

The effect of the grain boundary of ice crystals in a frozen gelatin solution on the dielectric properties was investigated by the combination of a dielectric spectrometer and image analysis. A micro-slicer image processing system (MSIPS) was applied to measure the grain boundary properties as the perimeter density and number density of ice crystals. The perimeter density and number density of the ice crystals increased with increasing freezing rate. The dielectric properties of the frozen gelatin solution at various freezing rates were measured in the frequency range of 100 Hz to 100 kHz at -40 degrees C. The relaxation time did not affect the grain boundary properties. The perimeter density and number density significantly affected dielectric parameter epsilon(0)-epsilon(infinity) and electrical conductivity sigma(0). These results indicate that the dielectric spectrometer could be used to estimate the grain boundary properties in a frozen gelatin solution.

Estimation of damage to cells of Japanese radish induced by high pressure with drying rate as index.

The relative drying rate of samples (RDR), which is the ratio of the drying rate of pretreated samples to that of untreated ones, might be used as a tool to investigate the damage to cells of agroproducts induced by high-pressure treatment. Damage to cells induced by high pressure was estimated by comparing the RDR after high-pressure pretreatment with the RDR after chloroform-vapor, heat, and freeze-thaw pretreatments of Japanese radish samples. The RDR after high-pressure pretreatment was similar to the RDR after chloroform-vapor pretreatment, and was lower than for heat, and for freeze-thaw pretreatment. For agroproducts, high-pressure treatment is thus comparatively moderate.

Formation of green-blue compounds in Brassica rapa root by high pressure processing and subsequent storage.

The effect of high pressure treatment on biochemical changes during storage was investigated using Brassica rapa root. High pressure treated samples with 400 and 600 MPa formed unique green-blue color during 7-d storage at 4 degrees C. The mechanism of green-blue compound formation would be based on biochemical pathway for a unique green-blue pigment synthesis, containing O2-dependent steps and possibly enzymatic reactions.

A culture-dependent bacterial community structure analysis based on liquid cultivation and its application to a marine environment.

A method for analyzing culture-dependent bacterial community structure by liquid cultivation was established using 96-well microplates. Using 96-well microplates, this method can easily provide accurate enumeration of viable microorganisms and simultaneous separation of bacteria, which allowed us to analyze the bacterial community. Bacteria in diluted surface seawater were separated using 96-well microplates and cultivated with 1/5 ZoBell 2216E liquid medium. The 98 cultures obtained were subsequently applied to phylogenetic analysis based on 16S rRNA gene sequences. The bacterial diversity, evaluated by the Shannon-Weaver index, was relatively small but comparable to previously reported bacterial communities of several environments. The most abundant group was the family Rhodobacteraceae, which has been frequently detected in marine environments. Most bacteria were phylogenetically related to bacteria or uncultured clones detected in marine environments, but distant from published species. The analysis of bacterial community structure by liquid cultivation would be useful as an alternative culture-dependent approach.

Comparative analyses of viable bacterial counts in foods and seawater under microplate based liquid- and conventional agar plate cultivation: increased culturability of marine bacteria under liquid cultivation.

Bacterial counts under liquid cultivation using 96-well microplates were performed. The counts under liquid and under solid cultivation were equivalent in foods, although the counts under liquid cultivation exceeded those under solid cultivation in seawater, suggesting that some bacteria in seawater were viable but did not form detectable colonies. Phylogenetic analysis of bacteria obtained under liquid cultivation was also performed.