Microbiological assay of nicotinic acid in natural materials

Graduation date: 1944During the routine determination of the vitamin contents of dehydrated foods, it was observed that nicotine acid values were often lower than expected. The methods of extraction of the food samples were therefore studied, together with the manner of preparation of the assay medium in an effort to secure optimum assay conditions. \ud The procedure followed in the improvement of the assay method was to use extracts of natural materials in the basal medium provided for the growth of Lactobacillus arabinosus. These extracts were rendered nicotinic acid-free by adsorption of Llyod's reagent. Of the materials investigated, yeast and peptone were included in the medium. These extracts furnished several of the known vitamins and also possessed extra stimulatory ingredients required by the organism. The improved medium was simple and afforded an increased sensitivity of the organism to nicotinic acid; also the standard curve obtained by use of this medium was linear over a wide range. The time required to establish a satisfactory standard curve has been shortened from 72 hours to 36 hours