Abstract
Carbethoxythiamine (I), carbobutoxythiamine (II) and dicarbethoxythiamine (III) were proved to have no growth-stimulating activity to L. fermenti in the broth without cysteine, but in the broth containing cysteine, (I) or (II) showed an activity less than 1/10 and (III) showed an activity less than 1/100 in comparison with that of thiamine-HCl. It was shown that (I) was more effective than thiamine in stimulating the growth of Kl. apiculata, while (II) was a little inferior and (III) was more inferior to thiamine after incubation for 20 hours. After incubation for 60 hours, the growth response to (I) or (II) was better than that to thiamine and the rssponse to (III) was nearly same as that fo thiamine. It was demonstrated by means of bioautography of the extract from Kl. apiculata after incubation with (I) for 20 hours that the cells contained thiamine or its diphosphate but not (I).
