Modeling the inactivation of Escherichia coli O157:H7 and generic Escherichia coli by supercritical carbon dioxide.
In this study, supercritical carbon dioxide (SC-CO(2)) was applied in the inactivation of pathogenic Escherichia coli (E. coli) O157:H7 and generic E. coli. For both strains suspended in physiological saline (PS), colony forming units per ml were reduced by 8 log orders within 15-30 min, in a treatment range of 80-150 bar and 35-45 degrees C. Any significant differences between the two E. coli strains during the inactivation by SC-CO(2) were not noticed. The microbial inactivation curve, which was established by the modified Gompertz model describing the survival rate with treatment time, was divided into three distinct stages. When using cells in PS, k(dm), lambda and t(8) (the time for an 8-log reduction of cell counts) were 0 to 3 min(-1), 8 to 16 min and 11 to 29 min, respectively. The temperature-dependency of the microbial inactivation was verified via the correlation of the logarithm of k(dm) versus the inverse of temperature. We have observed lower inactivation rates in phosphate-buffered saline (PBS) than in PS, the lowered pH, and an increase of UV-absorbing substances in the cell suspension after SC-CO(2) treatment. Also, the deformation and collapse of the SC-CO(2)-treated cells were revealed by scanning and transmission electron microscopy, and the deactivation of cellular enzymes occurred. These all suggest that the inactivation of E. coli O157:H7 and generic E. coli was possibly caused in a concerted manner by acidification, damage to cell membranes and subsequent leakage of cellular materials, and the inactivation of cellular enzymes.
Kim
Soo Rin
SR
Division of Food Bioscience and Technology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea.
Rhee
Min Suk
MS
Kim
Byoung Chul
BC
Kim
Kyoung Heon
KH
D002245:Carbon Dioxide / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006874:Hydrostatic Pressure; D007700:Kinetics; D008433:Mathematics; D050296:Microbial Viability; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D013997:Time Factors
D002245:Carbon Dioxide