Abstract
A cup-plate technique for the microbioassay of folate using Lactobacillus casei as a test organism was attempted. The folate content of powdered agar added to basal medium affected the clearness and sharpness of the growth zones. There was a linear relation between the diameters of growth zones and logarithms of the concentrations within the range of 10〜400 ng/ml of pure folate solution. In the statistical evaluation of the assay results the maximum errors of. thc estimate were below 10%. The total folate contents in some natural products obtained by cup-plate method were a little high to those obtained with turbidimetric one and the recovery experiments were successful enough. These resuls suggest that the cup-plate method may be available for the microbiological assay of folate in natural products.
