II. CHEMISTRY 5G5 



scntial nutrient in the medium.'^''-^" This so-called oleic acid factor may 

 even satisfy the biotin requirement of mosquito larvae (Aedes aegypti) for 

 their growth to the fourth instar.^^^ 



The cts-octadecenoic acids to which the oleic acid (czs-9-octadecenoic 

 acid) belongs showed in test no great differences in biotin-like activity. 

 In contrast, wide variations were found among the (ra7is acids. The activity 

 of /rans-9-octadecenoic (elaidic) acid was of the same order as that of oleic 

 acid. Activity of trans acids tested decreased for positional change of the 

 double bond on either side of trans-9- to almost no activity for trans-Q- 

 and for A-17-octadecenoic acid. Considerable synergistic activity with 

 biotin was noticeable for the trans compounds except for ^rans-9-octa- 

 decenoic acid, but only additive effect for the cis acids. The biotin-like 

 effect of isooleic acid mixtures formed during hydrogenation of vegetable 

 oils was comparable to that of oleic acid itself. Saturated fatty acids, with- 

 out showing any biotin-like activity per se, augmented the activity of the 

 unsaturated fatty acids in the mixture. ^^^ 



The dextran-forming Lenconostoc requires biotin in glucose and fructose 

 media but does not require this vitamin in sucrose media to the degree 

 that the disaccharide was utilized via the mechanism resulting in dextran 

 synthesis. ^®° Biotin may be replaced for Lenconostoc by oleic acid, which was 

 used in the form of the surface-active polyoxyethylene sorbitan monooleate 

 (Tween 80) and even by the saturated fatty acid, lauric acid, when added 

 to the medium in form of Tween 20, the surface active polyoxyethylene 

 sorbitan monolaurate.^^^ 



Various explanations were given for the biotin-sparing effect of oleic acid 

 and related compounds. It has been postulated that biotin is essential for 

 the synthesis of oleic acid and perhaps of other fatty acids^^^ or that oleic 

 acid may act as a precursor or should function only by alteration of cell 

 peraieability.^"^' ^^'* The effect of Tween 20 on Lenconostoc underscores the 

 physical factor. On the other hand it has been recently shown that washed 

 cells of Lactohacillus casei harvested from the culture medium containing 

 oleic acid and no biotin contained ten times as much biotin as originally 



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1" W. L. Williams, H. P. Broquist, and E. E. Snell, ./. Biol. Chem. 170, 619 (1947). 



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