Evaluation of Structural Changes Induced by High Hydrostatic Pressure in Leuconostoc mesenteroides

ABSTRACT Scanning electron microcopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) were used to evaluate structural changes in Leuconostoc mesenteroides cells as a function of high-hydrostatic-pressure treatment. This bacterium usually grows in chains of cells, which were increasingly dechained at elevated pressures. High-pressure treatments at 250 and 500 MPa also caused changes in the external surface and internal structure of cells. Dechaining and blister formation on the surface of cells increased with pressure, as observed in SEM micrographs. TEM studies showed that cytoplasmic components of the cells were affected by high-pressure treatment. DSC studies of whole cells showed increasing denaturation of ribosomes with pressure, in keeping with dense compacted regions in the cytoplasm of pressure-treated cells observed in TEM micrographs. Apparent reduction of intact ribosomes observed in DSC thermograms was related to the reduction in number of viable cells. The results indicate that inactivation of L. mesenteroides cells is mainly due to ribosomal denaturation observed as a reduction of the corresponding peak in DSC thermograms and condensed interior regions of cytoplasm in TEM micrographs.

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Inactivation of Escherichia coli andListeria innocua in Milk by Combined Treatment with High Hydrostatic Pressure and the Lactoperoxidase System

Applied and Environmental Microbiology ◽

10.1128/aem.66.10.4173-4179.2000 ◽

2000 ◽

Vol 66 (10) ◽

pp. 4173-4179 ◽

Cited By ~ 63

Author(s):

Cristina García-Graells ◽

Caroline Valckx ◽

Chris W. Michiels

Keyword(s):

Escherichia Coli ◽

High Pressure ◽

Hydrostatic Pressure ◽

High Hydrostatic Pressure ◽

Combined Treatment ◽

Food Preservation ◽

Pressure Treatment ◽

E Coli ◽

Preservation Method ◽

Lactoperoxidase System

ABSTRACT We have studied inactivation of four strains each ofEscherichia coli and Listeria innocua in milk by the combined use of high hydrostatic pressure and the lactoperoxidase-thiocyanate-hydrogen peroxide system as a potential mild food preservation method. The lactoperoxidase system alone exerted a bacteriostatic effect on both species for at least 24 h at room temperature, but none of the strains was inactivated. Upon high-pressure treatment in the presence of the lactoperoxidase system, different results were obtained for E. coli and L. innocua. For none of the E. coli strains did the lactoperoxidase system increase the inactivation compared to a treatment with high pressure alone. However, a strong synergistic interaction of both treatments was observed for L. innocua. Inactivation exceeding 7 decades was achieved for all strains with a mild treatment (400 MPa, 15 min, 20°C), which in the absence of the lactoperoxidase system caused only 2 to 5 decades of inactivation depending on the strain. Milk as a substrate was found to have a considerable effect protecting E. coli and L. innocua against pressure inactivation and reducing the effectiveness of the lactoperoxidase system under pressure on L. innocua. Time course experiments showed that L. innocua counts continued to decrease in the first hours after pressure treatment in the presence of the lactoperoxidase system.E. coli counts remained constant for at least 24 h, except after treatment at the highest pressure level (600 MPa, 15 min, 20°C), in which case, in the presence of the lactoperoxidase system, a transient decrease was observed, indicating sublethal injury rather than true inactivation.

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Effect of ultra-high hydrostatic pressure on the survival of Chromohalobacter beijerinckii

Medycyna Weterynaryjna ◽

10.21521/mw.5520 ◽

2016 ◽

Vol 72 (6) ◽

pp. 364-368

Author(s):

Janina Pęconek ◽

Monika Fonberg-Broczek ◽

Jacek Szczawiński ◽

Dorota Sawilska-Rautenstrauch

Keyword(s):

High Pressure ◽

Hydrostatic Pressure ◽

High Hydrostatic Pressure ◽

Nutrient Broth ◽

Aerobic Bacteria ◽

Pressure Treatment ◽

Average Sensitivity ◽

High Pressure Treatment ◽

Smoked Salmon ◽

D Values

The aim of the study was to determine the effect of ultra-high hydrostatic pressure on the survival of Chromohalobacter beijerinckii in samples of nutrient broth containing a 6% addition of NaCl and in samples of cold-smoked salmon. Both types of samples were exposed to ultra-high hydrostatic pressure of 300 and 400 MPa for 0, 5, 10 and 15 min. The number of Chromohalobacter beijerinckii was determined in all control samples and samples subjected to high pressure. The total number of aerobic bacteria was additionally determined in the samples of cold-smoked salmon intentionally inoculated with Chromohalobacter beijerinckii. It was found that Chromohalobacter beijerinckii showed a clearly greater sensitivity to high hydrostatic pressure in the nutrient broth (D-values: 300 MPa - 3.72 min; 400 MPa - 1.90 min) than it did in the samples of cold-smoked salmon (D-values: 300 MPa - 5.83 min; 400 MPa - 3.08 min). The results concerning the total number of aerobic bacteria show that Chromohalobacter beijerinckii is more susceptible to high pressure than the accompanying microflora present in cold-smoked salmon. High pressure treatment at 400 MPa applied for 15 min caused a destruction of Chromohalobacter beijerinckii cells that was clearly visible under a scanning electron microscope. Chromohalobacter beijerinckii belongs to bacteria that have average sensitivity to high hydrostatic pressure.

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Predictive Model for Inactivation of Campylobacter spp. by Heat and High Hydrostatic Pressure

Journal of Food Protection ◽

10.4315/0362-028x-70.9.2023 ◽

2007 ◽

Vol 70 (9) ◽

pp. 2023-2029 ◽

Cited By ~ 22

Author(s):

SEHAM LORI ◽

ROMAN BUCKOW ◽

DIETRICH KNORR ◽

VOLKER HEINZ ◽

ANSELM LEHMACHER

Keyword(s):

High Pressure ◽

Hydrostatic Pressure ◽

High Hydrostatic Pressure ◽

Poultry Meat ◽

Inactivation Kinetics ◽

Order Kinetic ◽

Pressure Treatment ◽

Short Term ◽

Short Term Treatment ◽

High Pressure Treatment

Campylobacter represents one of the leading causes of foodborne enteritis. Poultry and its products frequently transmit the pathogen. The objective of the present study was to model predictively the short-term inactivation of Campylobacter in a ready-to-eat poultry product to develop an economic high-pressure treatment. We inactivated baroresistant strains of Campylobacter jejuni and Campylobacter coli, grown to stationary phase on nutrient agar and inoculated in poultry meat slurry, by heat and high hydrostatic pressure. Incubation at ambient pressure at 70°C for 1 min and at 450 MPa at 15°C for 30 s inactivated more than 6 log CFU of this foodborne pathogen per ml of poultry meat slurry. Thermal and pressure inactivation kinetics of C. coli and C. jejuni in poultry meat slurry were accurately described by a first-order kinetic model. A mathematical model was developed from 10 to 65°C and from ambient to 500 MPa that predicts the reduction in numbers of Campylobacter in response to the combination of temperature, pressure, and treatment time. We suggest the high-pressure treatment of foods to avoid health risks caused by Campylobacter. The nonthermal short-term treatment of the examined food model system represents a successful step to an economic high-pressure procedure.

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Inactivation of Geobacillus stearothermophilus Spores by High-Pressure Carbon Dioxide Treatment

Applied and Environmental Microbiology ◽

10.1128/aem.69.12.7124-7129.2003 ◽

2003 ◽

Vol 69 (12) ◽

pp. 7124-7129 ◽

Cited By ~ 87

Author(s):

Taisuke Watanabe ◽

Soichi Furukawa ◽

Junichi Hirata ◽

Tetsuya Koyama ◽

Hirokazu Ogihara ◽

...

Keyword(s):

Heat Treatment ◽

Activation Energy ◽

High Pressure ◽

Hydrostatic Pressure ◽

High Hydrostatic Pressure ◽

Bacillus Coagulans ◽

Bacterial Spores ◽

Pressure Treatment ◽

Geobacillus Stearothermophilus ◽

High Hydrostatic Pressure Treatment

ABSTRACT High-pressure CO2 treatment has been studied as a promising method for inactivating bacterial spores. In the present study, we compared this method with other sterilization techniques, including heat and pressure treatment. Spores of Bacillus coagulans, Bacillus subtilis, Bacillus cereus, Bacillus licheniformis, and Geobacillus stearothermophilus were subjected to CO2 treatment at 30 MPa and 35°C, to high-hydrostatic-pressure treatment at 200 MPa and 65°C, or to heat treatment at 0.1 MPa and 85°C. All of the bacterial spores except the G. stearothermophilus spores were easily inactivated by the heat treatment. The highly heat- and pressure-resistant spores of G. stearothermophilus were not the most resistant to CO2 treatment. We also investigated the influence of temperature on CO2 inactivation of G. stearothermophilus. Treatment with CO2 and 30 MPa of pressure at 95°C for 120 min resulted in 5-log-order spore inactivation, whereas heat treatment at 95°C for 120 min and high-hydrostatic-pressure treatment at 30 MPa and 95°C for 120 min had little effect. The activation energy required for CO2 treatment of G. stearothermophilus spores was lower than the activation energy for heat or pressure treatment. Although heat was not necessary for inactivationby CO2 treatment of G. stearothermophilus spores, CO2 treatment at 95°C was more effective than treatment at 95°C alone.

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Subunit interaction of vacuolar H+-pyrophosphatase as determined by high hydrostatic pressure

Biochemical Journal ◽

10.1042/bj3310395 ◽

1998 ◽

Vol 331 (2) ◽

pp. 395-402 ◽

Cited By ~ 12

Author(s):

Su J. YANG ◽

Shu J. KO ◽

Yuan R. TSAI ◽

Shih S. JIANG ◽

Soong Y. KUO ◽

...

Keyword(s):

High Pressure ◽

Hydrostatic Pressure ◽

High Hydrostatic Pressure ◽

Spectroscopic Techniques ◽

Dependent Manner ◽

Pressure Treatment ◽

Concentration Dependent Manner ◽

Subunit Dissociation ◽

Km Value ◽

And Function

Vacuolar H+-pyrophosphatase (H+-PPase) from etiolated hypocotyls of mung bean (Vigna radiata L.) is a homodimer with a molecular mass of 145 kDa. The vacuolar H+-PPase was subjected to high hydrostatic pressure to investigate its structure and function. The inhibition of H+-PPase activity by high hydrostatic pressure has a pressure-, time- and protein-concentration-dependent manner. The Vmax value of vacuolar H+-PPase was dramatically decreased by pressurization from 293.9 to 70.2 µmol of PPi (pyrophosphate) consumed/h per mg of protein, while the Km value decreased from 0.35 to 0.08 mM, implying that the pressure treatment increased the affinity of PPi to vacuolar H+-PPase but decreased its hydrolysis. The physiological substrate and its analogues enhance high pressure inhibition of vacuolar H+-PPase. The HPLC profile reveals high pressure treatment of H+-PPase provokes the subunit dissociation from an active into inactive form. High hydrostatic pressure also induces the conformational change of vacuolar H+-PPase as determined by spectroscopic techniques. Our results indicate the importance of protein–protein interaction for this novel proton-translocating enzyme. Working models are proposed to interpret the pressure inactivation of vacuolar H+-PPase. We also suggest that association of identical subunits of vacuolar H+-PPase is not random but proceeds in a specific manner.

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