[Effect of high hydrostatic pressure on microbial physiological characteristics]

Area of Science:

• Microbiology
• Food Science
• Biotechnology

Background:

• Listeria monocytogenes and Escherichia coli are significant foodborne pathogens.
• Understanding microbial responses to non-thermal processing is crucial for food safety.
• High hydrostatic pressure (HHP) is a promising food preservation technique.

Purpose of the Study:

• To investigate the physiological effects of high hydrostatic pressure on Listeria monocytogenes NCTC 11994 and Escherichia coli ATCC 80739.
• To quantify the antimicrobial efficacy of HHP against these specific bacterial strains.
• To elucidate the cellular mechanisms underlying HHP-induced microbial inactivation.

Main Methods:

• Exposure of Listeria monocytogenes NCTC 11994 and Escherichia coli ATCC 80739 to high hydrostatic pressure (400 MPa for 10 minutes).
• Enumeration of microbial counts (log cfu) before and after pressure treatment.
• Measurement of intracellular pH (pHi).
• Assessment of membrane potential.
• Quantification of intracellular potassium ion (K+) efflux.
• Determination of intracellular adenosine triphosphate (ATP) concentration.

Main Results:

• A significant reduction of 7 log cfu for both Listeria monocytogenes and Escherichia coli was observed at 400 MPa for 10 minutes.
• High hydrostatic pressure treatment led to a decrease in intracellular pH.
• Pressure-induced alterations included lowered membrane potential and efflux of intracellular potassium.
• A significant decrease in intracellular ATP concentration was detected post-treatment.

Conclusions:

• High hydrostatic pressure is highly effective in reducing viable counts of Listeria monocytogenes and Escherichia coli.
• HHP induces profound physiological changes in bacterial cells, including disruption of ion homeostasis and energy metabolism.
• These cellular disruptions contribute to the antimicrobial mechanism of high hydrostatic pressure, offering a viable non-thermal pasteurization method.