Nicotinic Acid Requirements of Certain Yeasts.

Knowledge of the accessory growth factors concerned in the physiology of lactose-fermenting yeasts was needed in an investigation of fermentation that was being conducted by the Bureau of Dairy Industry. Since information on nicotinic acid requirements for the growth of yeasts not fermenting lactose was at best fragmentary and incomplete and information on lactose-fermenting yeasts was completely lacking, a study was undertaken to develop the pertinent knowledge. It has been known since 1913 that cells of the ill-defined species, Saccharomyces cerevisiae, contain nicotinic acid. Funk (1913) obtained nicotinic acid as a constituent of his "vitamine" fraction from yeast. With this knowledge of the nicotinic acid content of yeast, it would seem that investigators would have become interested in the growth response of living cells. However, a careful search of the literature has revealed very few publications on the growth response of yeast to nicotinic acid. Schultz, Atkin and Frey (1938) stated that nicotinic acid has no "bios" effect on strains of S. cerevisiae. Fink and Just (1939) showed that Torula utilis, an organism which does not ferment lactose, can synthesize the pyridine ring of nicotinic acid from such simple sources as ethanol, acetic acid, fermentable carbohydrates, ammonia nitrogen, and nutritive salts. K6gl and Borg (1941) found that the growth of the Konigsgist or Strain M yeast is not stimulated by nicotinamide alone. Nicotinamide plus thiamine produced a slight stimulation which probably was caused by the thiamine rather than the nicotinamide. Leonian and Lilly (1942) cultivated yeasts which had been trained to grow on a completely synthetic medium devoid of vitamins. As will be shown later in this paper, it is unnecessary to "train" yeasts not fermenting lactose to grow in a medium free of nicotinic acid only. Koser, Wright, and Dorfman (1942) mentioned, en passant, that nicotinamide was one of the factors necessary for rapid growth of one strain of Torula cremoris. No other information was found in the literature concerning the growth response of lactose-fermenting yeasts to nicotinic acid.