Oleic Acid and Related Compounds as Growth Factors for Lactic Acid Bacteria*

It is well known that under special conditions certain fatty acids markedly affect growth of lactic acid bacteria. In the microbiological assay of riboflavin and of pantothenic acid, marked stimulation of the assay organism, Lactobacillus cusei, results from the presence of small amounts of lecithin or of fatty acids (1, 2) when these vitamins are present in suboptimal amounts. At higher levels of the fatty substances, inhibition may result. The same effect of lipoidal materials is observed in the assay of pantothenic acid with Lactobacillus arabinosus (3). More recently it was observed that the presence of oleic acid (4), rice oil (4), or a fat-soluble substance of unknown nature obtained from blood (5) eliminates the requirement of Lactobacillus casei for biotin. Oleic acid also duplicates, in many respects, the growth-promoting action of acetate for a variety of lactic acid bacteria (6). In surveying the nutritive requirements of various lactic acid bacteria, a number of cultures were encountered for which oleic acid or related compounds are essential growth factors, even in the presence of both biotin and acetate. The present study deals with these organisms and extends the studies on lactic acid bacteria for which fatty acids can substitute for biotin.