Conductivity and pH dual detection of growth profile of healthy and stressed Listeria monocytogenes

Liju Yang, Padmapriya P. Banada, Yi Shao Liu, Arun K. Bhunia, Rashid Bashir

Research output: Contribution to journalArticlepeer-review


In this study, growth of Listeria monocytogenes in a low conductivity growth medium (LCGM) was simultaneously monitored by conductivity and pH measurements. Detection times obtained from the conductivity and pH growth curves were inversely related to the initial concentration of L. monocytogenes in the medium. Linear responses were found by plotting detection times obtained from both conductivity and pH growth curves as a function of initial cell concentration in the range of 102 to 107 cfu/mL. The detection time was approximately 12 and 2 h for 102 and 10 7 cfu/mL of viable L. monocytogenes, respectively, using the conductivity growth curves, whereas it was approximately 1 h less using the pH growth curves. This dual detection system was used for evaluating the growth of acid-, temperature-, and salt-treated L. monocytogenes in the medium. Acid stress at pH 2 and 3 for 3 h caused approximately 12 and 4 h delay in the detection time on pH growth curves, while stress at pH 5 for 3 h did not cause a significant delay in detection time. Delay in detection times was also observed for L. monocytogenes cells exposed to 45°C for more than 1 h (2 and 6 h). Exposure to 10% NaCl for 3 h did not cause visible delay in the detection time. These observations on detection times for stressed L. monocytogenes had a consistent trend with the cell number decrease determined by surface plating method.

Original languageEnglish (US)
Pages (from-to)685-694
Number of pages10
JournalBiotechnology and bioengineering
Issue number6
StatePublished - Dec 20 2005
Externally publishedYes


  • Conductivity
  • Detection
  • Listeria monocytogenes
  • pH
  • Stressed bacteria

ASJC Scopus subject areas

  • Biotechnology
  • Microbiology


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