Microbiological Assay of Vitamin B6 by Thin-Layer Cup-Plate Method with Saccharomyces carlsbergensis

概要

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The agar-plate diffusion method for determination of vitamin B6 in natural products was presented, which improved on its weak point of relative insensitivity by using a thin-layer plate technique.The optimum conditions for the assay were proposed as follows. Assay medium: Atkin's basal medium with minor modifications and 1% agar, 0.75mm plate thickness (thin-layer), pH 5.0 to 6.0. Standard solutions of vitamin B6: pH 5.0 to 6.0. Inoculum size of test organism: 0.075 optical density in final. Incubation: 30°, 12 to 16 hr.Under our conditions a reproducible, clear and sharply-defined growth zone on the assay plate was steadily obtained and there was a linearity of the dose-response to pure vitamin B6 solution over a wide range of 20 to 2, 000mμg/ml. In the statistical analysis of the results the probable errors amounted to only 4 to 5%. The total vitamin B6 values in some natural materials obtained by this method were as equal as those determined with turbidimetric ones. Also, recovery experiments were successful enough and the dose-response line for all samples used hardly had any drift from that for pure vitamin B6 solution.This method is simple, accurate and adequate for the routine assay of a large number of samples.
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