A Microbiological Assay for Biotin

Because of its role in the nutrition of animals and lower forms of life, biotin has become an important member of the B vitamins.Although widely distributed in nature, it occurs in exceedingly low concentration.To study its occurrence, properties, and functions, suitable methods for its determination are imperative.Kijgl and Tennis (1) utilized yeast growth as a quantitative measure of the biotin in their preparations.Later Snell, Eakin, and Williams (2) reported a 16 hour assay for biotin which also utilized the response of yeast to added increments of biotin as a measure of the biotin present.West and Wilson (3) used a strain of Rhizobium trijolii for the determination of biotin.In all of these methods, growth is measured turbidimetrically.In this paper is described a method for the assay of biotin which offers certain advantages over previously published methods.It is based on the fact that, under proper conditions, the titratable acidity produced by Lactobacillus casei E is a function of the quantity of biotin present in the medium.Colored and turbid solutions, which give anomalous results with turbidity methods, can be assayed satisfactorily by this method.The same organism that is used in the riboflavin (4) and pantothenic acid (5) assays is used in this assay; thus no separate stock cultures are necessary.