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The bakers' yeast fermenting with the maximum rate under suitable conditions shows still more carbon dioxide production provided that a minute amount of thiamine is added. This phenomenon was discovered by Atkin, Schultz, and Frey, and was applied for microdetermination of this vitamin. By use of this determination method, the authors examined the accelerating effect of thiamine and twenty-three kinds of its derivatives on anaerobic carbon dioxide production, and found that this method could be used as an examination method for the biological activity of thiamine analogues. However, care must be taken of the fact that the effect on yeast do not always agree with the effect on animals. Among the thiamine analogues tested, 1) Analogues of S, S-alkyl type were found to be nearly as active as thiamine, and some of them were slightly more active than thiamine. 2) When the analogues of O, S-diacyl type were examined, the effect of O, S-diacetyl thiamine was found to be almost the same as that of thiamine. Among the following compounds, the full developement of the effect was delayed in case of the later-cited compound compared with the former-cited. O, S-diacetyl>;dipropionyl>;propionyl-benzoyl>;dibenzoyl However, after the full developement of the accelerating effect, all of these analogues were as effective as thiamine. 3) O-acyl analogues were slightly less effective than thiamine. 4) S-alkyl analogues were not effective in general. 5) Thiothiamine and its derivatives did not show any activity. 6) Three kinds of antivitamins were tested, but among these only oxythiamine exhibited a slight anti-thiamine activity. As to the mechanism of the acceleration, it was assumed that the nitrogen metabolism had an essential interrelationship with the effect. It was observed that the nitrogen source was indispensable for the development of the effect, and the increase in nitrogen content and sporation rate of yeast cells accompanied with the increase of the effect. Metal ions and the cell-membrane permeability also played some role for the development of the accelerating effect.

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In order to study the thermostable antithiamine factor (SF) of horsetail, the thiamine decomposing activities of paper chromatograms of horsetail extract were estimated and it was found that two pigments and some fluorescent substances had a strong activity. From ethyl acetate fraction of alcoholic extract of horsetail, yellow needle crystals, i. e., articulatin (C_<20>H_<18>O_<12>・2H_2O, m.p. 191°), was isolated. When articulatin was hydrolysed, yellow needles, i e., articulatidin (C_<l4>H_6O_7・l^I/2H_2O, m.p. 291-293°), and glucose were produced. It is, therefore, supposed that articulatin was pentahydroxyanthraquinone-glucoside. Because articulatin and articulatidin had a strong thiamine decomposing activity, a part of SF of horsetail was considered to be formed of these pigments.

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The following results were obtained by a submerged culture of Eremothecium ashbyii using a fermentor of 100 liters capacity : 1) Riboflavin of 50-100mg% were obtained on a medium containg glucose and peptone as main substrates ; the maximum yield was 109mg%. 2) On a medium consisting of cane molasses and fish meals chiefly, riboflavin yields were 100-150 mg% but the maximum yield was found to be 217mg%.

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1. In industrial tests using a fermenter of two tons in capacity, the authors obtained nearly the same results as the previous findings with a 100 liters plant ; namely with a medium consisting of cane molasses and peptone, or cane molasses and fish meal, riboflavin yields in the method of feeding were of 127-216mg%. 2. From cost accounting with necessary industrial plans, it was concluded that the economical scale of production should be over 500 kg of riboflavin per month, and that it is premature to materialize such methods as the amount of consumption of riboflavin is not so high in Japan.

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