Metabolic activities of Listeria monocytogenes in the presence of sodium propionate, acetate, lactate and citrate

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Abstract
The effects of sodium propionate, acetate, lactate and citrate on cell proliferation, glucose and oxygen consumption, and ATP production in Listeria monocytogenes were investigated in growing and resting cells. Media pH was 6.7‐6.8. Growth inhibition increased while glucose consumption continued in the presence of ≥ 1% propionate, ≥ 3% acetate and ≥ 5% lactate in broth during incubation at 35°C, indicating that glucose consumption was uncoupled from cell proliferation. Acetate and propionate were the most effective antilisterials, whereas citrate (5%) was only slightly inhibitory. Of the four salts, only lactate supported growth, oxygen consumption and ATP production. While concentrations of 1 and 5% propionate, acetate and citrate did not have an effect on oxygen consumption, they inhibited ATP production. ATP production in the presence of the four salts was consistently lower at pH 6.0 than at neutral pH. Lactate served as an alternative energy source for L. monocytogenes in the absence of glucose but became toxic to the organism in the presence of the carbohydrate.