Abstract
As previously reported (Vitamins, 1962), the growth of Kloeckera apiculata was markedly inhibited and also that of Lactobacillus fermenti was moderately inhibited by dihydrothiamine (I) at such a high concentration as 1/4×10^<-3> or 1/4×10^<-2>M. Thiamine, essential for their growth, was non-effective for recovery of the growth-inhibition of Kl. apiculata or slightly effective for L. fermenti even at the highest concentration of 1/4×10^<-2>M. The addition of 10 mg of yeast extract to the medium instead of thiamine showed similar effect to the growth. As I is unstable in the acid medium, it is easily decomposed into Tris-(2-methyl-4-amino-5-pyrimidinylmethyl)-hexahydro-S-triazine (II) and 5-hydroxy-3-mercapto-2-pentanone (III). At the presence of sufficient amount of thiamine (0.169μg), II had no inhibitory effect on Kl. apiculata even at the concentration of 1/4×10^<-3>M and on the contrary 1/4×10^<-4>M of III showed a marked inhibition on the growth. After incubation of I with the basal medium, it was developed on a filterpaper-strip by acetic acid・n-butanol・H_2O (1 : 4 : 5) and III was both clearly detected chemically by NaN_3-I_2 reagent and by the means of bioautography (growth-inhibition of Kl. apiculata) at the same spot on the strip.
