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Hasegawa T.,Niigata University of Pharmacy and Applied Life Sciences | Hayashi M.,Niigata University of Pharmacy and Applied Life Sciences | Nomura K.,Niigata University of Pharmacy and Applied Life Sciences | Kido M.,Niigata Industrial Creation Organization NICO | And 9 more authors.
Journal of Bioscience and Bioengineering | Year: 2012

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. © 2012 The Society for Biotechnology, Japan.


Shigematsu T.,Niigata University | Hayashi M.,Niigata Industrial Creation Organization NICO | Nakajima K.,Niigata University | Uno Y.,Niigata University | And 6 more authors.
Journal of Physics: Conference Series | Year: 2010

High hydrostatic pressure (HP) with approximately below 400 MPa can induce a transformation of food materials to an alternative form, where membrane systems are damaged but certain enzymes are still active. HP treatment of water soaked brown rice grain could modify the mass transfer inside and apparent activities of enzymes, resulting in HP-dependent change of distribution of free amino acids. Thus, the distribution of free amino acids in brown rice grain during preservation after HP treatment was analyzed. Just after HP treatment at 200 MPa for 10 min, the distribution of free amino acids was not apparently different from that of untreated control. In contrast, after 1 to 4 days preservation at 25°C, amino acids, such as Ala, Glu, Gly, Asp and Val, showed higher concentrations than those in control. This result suggested that HP treatment induced proteolysis to produce free amino acids. However, Gln, Thr and Cys, showed no apparent difference, suggesting that conversion of certain amino acids produced by proteolysis occurred. Moreover, the concentration of γ-aminobutyric acid (GABA) in HP-treated sample was higher than that in untreated control. These results suggested that HP treatment induced alteration of distribution of free amino acids of rice grains via proteolysis and certain amino acids metabolism pathways. © 2010 IOP Publishing Ltd.


Shigematsu T.,Niigata University of Pharmacy and Applied Life Sciences | Nasuhara Y.,Niigata University of Pharmacy and Applied Life Sciences | Nagai G.,Niigata University of Pharmacy and Applied Life Sciences | Nomura K.,Niigata University of Pharmacy and Applied Life Sciences | And 6 more authors.
Journal of Food Science | Year: 2010

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. © 2010 Institute of Food Technologists®.


Nanba M.,Niigata University of Pharmacy and Applied Life Sciences | Nomura K.,Niigata University of Pharmacy and Applied Life Sciences | Nasuhara Y.,Niigata University of Pharmacy and Applied Life Sciences | Hayashi M.,Niigata University of Pharmacy and Applied Life Sciences | And 8 more authors.
High Pressure Research | Year: 2013

A high pressure (HP) tolerant (barotolerant) mutant a2568D8 and a variably barotolerant mutant a1210H12 were generated from Saccharomyces cerevisiae using ultra-violet mutagenesis. The two mutants, a barosensitive mutant a924E1 and the wild-type strain, were pressurized (225 MPa), and pressure inactivation behavior was analyzed. In the wild-type strain, a proportion of the growth-delayed cells were detected after exposure to HP. In a924E1, the proportion of growth-delayed cells significantly decreased compared with the wild-type. In a2568D8, the proportion of growth-delayed cells increased and the proportion of inactivated cells decreased compared with the wild-type. In a1210H12, the growth-delayed cells could not be detected within 120 s of exposure to HP. The proportion of growth-delayed cells, which incurred the damage, would affect the survival ratio by HP. These results suggested that cellular changes in barotolerance caused by mutations are remarkably affected by the ability to recover from cellular damage, which results in a growth delay. © 2013 Copyright Taylor and Francis Group, LLC.


Hasegawa T.,Niigata University of Pharmacy and Applied Life Sciences | Nakamura T.,Niigata University of Pharmacy and Applied Life Sciences | Hayashi M.,Niigata University of Pharmacy and Applied Life Sciences | Kido M.,Niigata Industrial Creation Organization NICO | And 8 more authors.
High Pressure Research | Year: 2013

We analyzed high hydrostatic pressure (HP)-induced inactivation of Escherichia coli in the presence of sucrose, NaCl, KCl, or LiCl under 250-400 MPa. Salt stress response (osmotic or cationic) mechanism was demonstrated to be evaluated by HP-induced inactivation kinetics. We selected nine mutant strains from the Keio collection; five strains each lacked one osmoregulatory gene (ΔmzrA, ΔenvZ, ΔompR, ΔompC or ΔompF), and four strains each lacked one cationic stress-response gene (ΔmscS, ΔmscL, ΔchaA or ΔnhaA). The nine mutants exhibited three different patterns of HP-induced inactivation. Of the nine genes, four (mzrA, mscS, nhaA and mscL) were involved in piezotolerance at NaCl concentration of 0.0-0.35 M. © 2013 Copyright Taylor and Francis Group, LLC.

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