O-Benzoylthiamine(OBT) and O, S-dibenzoylthiamine(DBT) were proved to be antagonistic to thiamine for the growth of L. fermenti in the broth containing cysteine : 50% inhibition indices were 340〜490 and 410〜640,respectively. In the absence of cysteine, 50% inhibition index of OBT was 210〜240 but that of DBT was unmeasurably higher than that in the presence of cysteine. It was concluded that DBT was only antagonistic to thiamine on its conversion to OBT by cysteine.
