[The effect of medium acidity on the light-dependent antibacterial activity of fatty acids]

The goal of this work was to study how the acidity of a medium influenced the light-dependent antibacterial activity of fatty acids towards Staphylococcus aureus. The antibacterial activity of arachidonic, linolenic, linoleic and oleic acids increased abruptly (by 1-2 orders of magnitude) under the action of visible light, it became more intensive with a rise in the number of double bonds in a fatty acid molecule, and the maximum shifted from the neutral region to an alkaline one as the aeration was intensified. In the case of saturated fatty acids (palmitic and stearic), the antibacterial activity with a maximum in the alkaline region was detected only in the light. The effect exerted by the number of double bonds in a fatty acid molecule and by the acidity of a medium on the mechanisms of fatty acid photooxidation is discussed.