Effects of Water Activity in Model Systems on High-Pressure Inactivation of Escherichia coli

2008 ◽  
Vol 2 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Ilona Setikaite ◽  
Tatiana Koutchma ◽  
Eduardo Patazca ◽  
Brian Parisi
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Water Activity ◽  
Model Systems

scholarly journals Mechanisms of Inactivation of Dry Escherichia coli by High-Pressure Carbon Dioxide

2017 ◽  
Vol 83 (10) ◽  
Author(s):  
Yuan Yao Chen ◽  
Feral Temelli ◽  
Michael G. Gänzle
Keyword(s):  
Escherichia Coli ◽  
Carbon Dioxide ◽  
High Pressure ◽  
Water Activity ◽  
Microbial Inactivation ◽  
Dominant Factor ◽  
Cyclopropane Fatty Acid ◽  
Content Type ◽  
E Coli ◽  
Cell Counts

ABSTRACT High-pressure carbon dioxide processing is a promising technology for nonthermal food preservation. However, few studies have determined the lethality of high-pressure CO2 on dry bacterial cells, and the mechanism of inactivation remains unknown. This study explored the mechanisms of inactivation by using Escherichia coli AW1.7 and mutant strains differing in heat and acid resistance, in membrane composition based on disruption of the locus of heat resistance, and in genes coding for glutamate decarboxylases and cyclopropane fatty acid synthase. The levels of lethality of treatments with liquid, gaseous, and supercritical CO2 were compared. The cell counts of E. coli AW1.7 and mutants with a water activity (aW) of 1.0 were reduced by more than 3 log10 (CFU/ml) after supercritical CO2 treatment at 35°C for 15 min; increasing the pressure generally enhanced inactivation, except for E. coli AW1.7 ΔgadAB. E. coli AW1.7 Δcfa was more susceptible than E. coli AW1.7 after treatment at 10 and 40 MPa; other mutations did not affect survival. Dry cells of E. coli were resistant to treatments with supercritical and liquid CO2 at any temperature. Treatments with gaseous CO2 at 65°C were more bactericidal than those with supercritical CO2 or treatments at 65°C only. Remarkably, E. coli AW1.7 was more susceptible than E. coli AW1.7 Δcfa when subjected to the gaseous CO2 treatment. This study identified CO2-induced membrane fluidization and permeabilization as causes of supercritical mediated microbial inactivation, and diffusivity was a dominant factor for gaseous CO2. IMPORTANCE The safety of dry foods is of increasing concern for public health. Desiccated microorganisms, including pathogens, remain viable over long periods of storage and generally tolerate environmental insults that are lethal to the same organisms at high water activity. This study explored the use of high-pressure carbon dioxide to determine its lethality for dried Escherichia coli and to provide insight into the mechanisms of inactivation. The lethality of high-pressure CO2 and the mechanisms of CO2-mediated inactivation of dry E. coli depended on the physical state of CO2. Liquid and supercritical CO2 were ineffective in reducing the cell counts of dry E. coli isolates, and the effectiveness of gaseous CO2 was related to the diffusivity of CO2. Results provide a novel and alternative method for the food industry to enhance the safety of low aW products.

Inactivation of Escherichia coli by high-pressure homogenisation is influenced by fluid viscosity but not by water activity and product composition

2005 ◽  
Vol 101 (3) ◽  
pp. 281-291 ◽  
Author(s):  
Ann M.J. Diels ◽  
Lien Callewaert ◽  
Elke Y. Wuytack ◽  
Barbara Masschalck ◽  
Chris W. Michiels
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Water Activity ◽  
Fluid Viscosity ◽  
Product Composition

Effect of High-Pressure Processing at Elevated Temperatures on Thiamin and Riboflavin in Pork and Model Systems

2007 ◽  
Vol 55 (4) ◽  
pp. 1289-1294 ◽  
Author(s):  
Peter Butz ◽  
Antal Bognar ◽  
Sepp Dieterich ◽  
Bernhard Tauscher
Keyword(s):  
High Pressure ◽  
Elevated Temperatures ◽  
High Pressure Processing ◽  
Model Systems

High Pressure Inactivation of Escherichia coli, Campylobacter jejuni, and Spoilage Microbiota on Poultry Meat

2012 ◽  
Vol 75 (3) ◽  
pp. 497-503 ◽  
Author(s):  
YANG LIU ◽  
MIRKO BETTI ◽  
MICHAEL G. GÄNZLE
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Campylobacter Jejuni ◽  
Resistant Mutant ◽  
Poultry Meat ◽  
E Coli ◽  
Cell Counts ◽  
Meat Spoilage ◽  
Brochothrix Thermosphacta ◽  
Pressure Resistance

This study evaluated the high pressure inactivation of Campylobacter jejuni, Escherichia coli, and poultry meat spoilage organisms. All treatments were performed in aseptically prepared minced poultry meat. Treatment of 19 strains of C. jejuni at 300 MPa and 30°C revealed a large variation of pressure resistance. The recovery of pressure-induced sublethally injured C. jejuni depended on the availability of iron. The addition of iron content to enumeration media was required for resuscitation of sublethally injured cells. Survival of C. jejuni during storage of refrigerated poultry meat was analyzed in fresh and pressure-treated poultry meat, and in the presence or absence of spoilage microbiota. The presence of spoilage microbiota did not significantly influence the survival of C. jejuni. Pressure treatment at 400 MPa and 40°C reduced cell counts of Brochothrix thermosphacta, Carnobacterium divergens, C. jejuni, and Pseudomonas fluorescens to levels below the detection limit. Cell counts of E. coli AW1.7, however, were reduced by only 3.5 log (CFU/g) and remained stable during subsequent refrigerated storage. The resistance to treatment at 600 MPa and 40°Cof E. coli AW1.7 was compared with Salmonella enterica, Shiga toxin–producing E. coli and nonpathogenic E. coli strains, and Staphylococcus spp. Cell counts of all organisms except E. coli AW 1.7 were reduced by more than 6 log CFU/g. Cell counts of E. coli AW1.7 were reduced by 4.5 log CFU/g only. Moreover, the ability of E. coli AW1.7 to resist pressure was comparable to the pressure-resistant mutant E. coli LMM1030. Our results indicate that preservation of fresh meat requires a combination of high pressure with high temperature (40 to 60°C) or other antimicrobial hurdles.

scholarly journals Influence of High Pressure on the Dimerization of ToxR, a Protein Involved in Bacterial Signal Transduction

2008 ◽  
Vol 74 (24) ◽  
pp. 7821-7823 ◽  
Author(s):  
Kai Linke ◽  
Nagarajan Periasamy ◽  
Matthias Ehrmann ◽  
Roland Winter ◽  
Rudi F. Vogel
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
High Pressure ◽  
Structure And Function ◽  
Transmembrane Segments ◽  
Bacterial Signal Transduction ◽  
Reporter Strains ◽  
And Function ◽  
First Time

ABSTRACT High hydrostatic pressure (HHP) is suggested to influence the structure and function of membranes and/or integrated proteins. We demonstrate for the first time HHP-induced dimer dissociation of membrane proteins in vivo with Vibrio cholerae ToxR variants in Escherichia coli reporter strains carrying ctx::lacZ fusions. Dimerization ceased at 20 to 50 MPa depending on the nature of the transmembrane segments rather than on changes in the ToxR lipid bilayer environment.

scholarly journals Effect of high-pressure carbon dioxide processing on the inactivation of aerobic mesophilic bacteria and Escherichia coli in human milk

2017 ◽  
Vol 16 (1) ◽  
pp. 122-126 ◽  
Author(s):  
Ana Claudia Berenhauser ◽  
Douglas Soares ◽  
Norton Komora ◽  
Juliano De Dea Lindner ◽  
Elane Schwinden Prudêncio ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Carbon Dioxide ◽  
High Pressure ◽  
Human Milk ◽  
Mesophilic Bacteria
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