抄録
Cup-plate technique as a microbiological assay method for vitamins has not yet been brought to practical use. A fundamental study of a plate-assay procedure for folic acid with Streptococcus faecalis as the test organism was undertaken in view of several advantages in the vitamin estimation. The folic acid content of powdered agar added to basal medium affected the clearness and sharpness of the growth zones. There was the linear relation between the diameters of growth zones and the logarithms of the concentrations within the range of 10 to 4000 mμg/ml of pure folic acid solution, and in the statistical evaluation of the assay results the maximum errors of the estimate were below 15%. These results suggest the possibility that the cup-plate method may be available for the microbiological assay of folic acid.
