A modified medium for Lactobacillus casei for the assay of B vitamins

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Abstract
An improved medium was developed for the assay of folic acid with L. casei and was tested for some other B vits. and tryptophan. The titrimetric dose-response curves for riboflavin, nicotinic acid, Ca pantothenate, biotin and tryptophan were satisfactory. The medium has been used in particular for the microbiological assay of total nicotinic acid, and the results were in good agreement with the chemical values. The bound form of nicotinic acid present in cereals was found to be less active than the free vitamin. A number of conjugates of pteroylglutamic acid and other pteridines were tested.