Food Science and Technology Department


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Published in Journal of Dairy Science 50 (1967), pp. 472-476.


Information on the inhibitory effect of free fatty acids was sought by growing lactic streptococci in the presence of labeled fatty acids and collecting the cells on membrane filters. The distribution of the radioactivity indicated adsorption by the bacteria. As the number of cells in the growth medium increased, accumulation of radioactivity with the cells on the filter increased. The cells accumulated less than one-tenth as much radioactivity from sodium butyrate as from lauric acid. Washing the cells on the filter with water decreased radioactivity. More complete elution of the radioactivity was obtained by filtering the mixture after it was made alkaline. Though this implies that the association of fatty acid and cells is pH-dependent, adsorption was always evident in the pH range of normal growth. Gas-liquid chromatographic analysis indicated the fatty acids were not metabolized. All results indicate weak adsorption at the bacteria: menstruum interface. The parallels of adsorption and inhibition indicate adsorption is associated with the inhibitory process.

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