抄録
A favourable condition for obtaining a reproducible and sharply defined growth zone in the plate method was indicated as follows. Assay medium : U.S.P. XV composition with 1% agar, 1.5 mm plate thickness, pH 6.5 to 7.0. Biotin solution : pH 6.0 to 7.0. Inoculum size of test organism : 0.075 OD in final. Incubation : 37℃, 20 to 24 hrs. Under the optimal condition there was a linearity of the dose-response to pure solution of biotin over a wide range of 4 to 200 mμg per ml. In the statistical evaluation of the results the maximum errors were below 14%. The biotin contents in several biological materials determined by the plate method were nearly equal to those obtained by the turbidimetric ones. Also, the recoveries of the added vitamin were satisfactory enough except for the case of a few animal samples, and the dose-response lines for all samples used hardly had any drift from that for pure biotin solution. These results may suggest that the cup-plate method using L. arabinosus as test organism is useful for the microbioassay of biotin in natural products.
