Lactic acid bacteria isolated from commercially produced alfalfa sprouts were screened for activity against Listeria monocytogenes F4258. Most active isolates were identified as Lactococcus lactis subsp. lactis. The isolates fell into two categories, strains that inhibited by acid production only, and strains that appeared to have additional inhibitory activity. An acid-only isolate, SP26, was used to evaluate the effect of initial pH (5, 6, 7, 8) and temperature (10, 20, and 30 °C) on the interaction between the lactic acid bacterium and L. monocytogenes using “sprout juice” as a model system. The model system was inoculated with an initial level of approx. 103 CFU ml-1L. monocytogenes in both mono-culture controls and the co-cultures and the co-cultures with L. lactis (103-104 CFU ml-1). The primary inhibitory effect attributable to L. lactis was a 2 to 3 log cycle decrease in the maximum population density obtained by L. monocytogenes. The extent of the inhibition was decreased at 10 °C, but was only slightly affected by pH in the range of 6.0 to 8.0. L. monocytogenes did not grow in the sprout broth at pH 5.0 at any of the incubation temperatures.
Authors:J. Limón, N. Heredia, L. Solís-Soto, and S. Garcia
The aim of this study was to investigate the effect of some food additives used in foods on cold tolerance of Clostridium perfringens at pH close to neutral.Maximal concentrations recommended for foods of sodium benzoate, potassium sorbate, sodium nitrite, monosodium glutamate, or mixtures of those were added to cultures and their effects on C. perfringens tolerance to 10 °C were evaluated. The effect of a previous shock at 28 °C was also determined. Growth of C. perfringens was not inhibited by the substances examined. Sodium nitrite, applied at maximal permitted concentrations, increased C. perfringens survival at 10 °C. Mixtures of GRAS compounds had either no clear effect, or increased tolerance to 10 °C. A pre-shock (28 °C) of the cultures treated with sodium benzoate, sodium nitrite or monosodium glutamate increased survival and stimulated growth of the cultures treated at 10 °C.We conclude that the addition of these compounds including sodium benzoate, potassium sorbate, sodium nitrite and monosodium glutamate to cultures of C. perfringens can influence their cold tolerance. In some cases, the substances that would normally eliminate microorganisms at lower pH, can increase tolerance of this bacterium, permitting survival at low temperatures.
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Biochemical changes in shrimp inoculated with Bacillus and
Authors:V. J. Sinanoglou and S. Miniadis-Meimaroglou
Mastronicolis, S. K., German, J. B. & Smith, G. M. (1996): Isolation and fatty acid analysis of neutral and polar lipids of the food bacterium Listeria monocytogenes . Fd Chem. , 57 , 451-456.
Isolation and fatty acid analysis of
UONG , T. , C ALLANAN , M. , L ICK , S. , H AMRICK , A. , C ANO , R. & K LAENHAMMER , T.R. ( 2005 ): Complete genome sequence of the probiotic lactic acid bacterium Lactobacillus acidophilus NCFM . PNAS , 102 , 3906 – 3912