Vitamin requirements of lactose-fermenting and certain other yeasts

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Abstract
Lactose-fermenting yeasts require exogenous inositol, thiamine hydrochloride, nicotinic acid or nicotinamide, d-Ca pantothenate, and biotin for early, rapid, and optimal growth. [beta]-alanine, but not the lactone portion of the pantothenic acid molecule, is utilized as a precursor for pantothenic acid. Pimelic acid is not utilized as a precursor for biotin. External sources of pantothenic acid, biotin, and, with many strains, thiamine hydrochloride, are critical factors for growth even during extended incubation. Exogenous choline chloride, riboflavin, nicotinic acid or its amide, folic acid, and p-aminobenzoic acid are not critical factors for the optimal growth of these yeasts, regardless of the period of incubation. Strains of Saccharomyces cerevisiae (not fermenting lactose) differ from the above in not requiring nicotinic acid or nicotin-amide and in needing extracellular pyridoxine hydro-chloride for growth. With any yeast tested it is essential that detns. of growth be made before 24 hrs. of incubation have elapsed if significant differences are not to be greatly minimized or vitiated by the synthesis of some factors in varying degrees.

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