FATS AS ESSENTIAL DIETARY COMPONENTS 893 



Ci6, but also of stearic acid (octadecanoic acid).^^^ Williams and Fieger^'* 

 reported that lauric (C12) and myristic (C14) also inhibit the growth of 

 Lactobacillus casei. Hassinen and colleagues^^^ observed that the Cg 

 and Cio saturated fatty acids inhibited the growth of both Gram-positive 

 and Gram-negative organisms, but that the C4, Ce, and Cg saturated acids 

 exliibited no significant depressing action against the growth of such or- 

 ganisms. The C12 saturated acid inhibited only the Gram-positive or- 

 ganisms, while the C14 acid exerted some inhibiting action upon Lacto- 

 bacillus bifidus and L. casei. On the other hand, Cheng et al}^"^ reported 

 that the saturated acids exhibited a synergistic action upon bacterial 

 growth when present along with oleic acid. This effect is discussed in the 

 next section. 



e. Growth Stimulation of Bacteria Produced by Mixed Fatty Acids from 

 Various Natural and Artificial Fats. A study of the biotin-like activities 

 of mixed fatty acids prepared from a number of fats showed that their 

 activity could not be correlated with the content of oleic and linoleic acids 

 only; it was necessary to consider the proportion of the several saturated 

 acids present. The following formula, which takes into account the 

 variation in activity of oleic and linoleic acids, and corrects for the syner- 

 gistic action for the saturated acids, was found to give excellent results in 

 predicting the activity of the fatty acid mixtures. Thus, the biotin 

 equivalent, expressed as millimicrograms of biotin per milligram of fatty 

 acids, equals: 



[(% oleic times 10.3) -f (% linoleic times 5.3)] 



100 ^ 



[{1.00 + S.3 X % saturated fatty acids)]'-^^ „^ , . ^ 

 — . Wlien this formula was em- 

 ployed, the calculated biotin-like effect of the mixed fatty acids was almost 

 identical with that found by bioassay. A comparison of the estimated 

 and found values of the fatty acids from the several fats is given in Table 5. 

 Spectori29 reported that the fatty acids of butterfat and of corn oil 

 produce similar results in stimulating the gro^\i;h of five strains of Escheri- 

 chia coli. He found no consistent distinction between their effects upon 

 bacterial growth, and presumably upon bacterial synthesis of the vitamins. 



f . Effects Other Than the Biotin-Like Effect of Unsaturated Fatty Acids 

 on Growth of Bacteria. Kodicek "5.256 demonstrated that most fatty acids 



^* J. B. Hassinen, G. T. Durbin, and F. W. Bernliart, Arch. Biochem. Biophys., SI 

 183-189(1951). 



^ E. Kodicek, Sytnposia Soc. Exptl. Biol, No. Ill, 217-232 (1949). 

 !«« E. Kodicek, Bull. soc. chim. biol., SO, 946-960 (1948). 



