In order to find out the mechanism of death of bacterial spores by heat, several experiments were carried out using the three aerobic strains, Bacillusnatto, Bacillus megatherium, and Bacillus mycoides. When the spores of these strains were heated in M/15 phosphate buffer (pH 7.0), the relationships between the initial spore cencentration (N spores per ml) and the survival time (ts) were found to be expressed by the following equation: log N=a+b log ts This linear relationship between log N and log ts was confirmed to exist in general, though the values of the constants a and b varied with many factors such as heating temperature, heating menstrum, strain, and the kind of subculture medium. When the spores of Bac natto were subcultured in glucose broth (nutrient broth plus 0.5% glucose) the survival time of the spores was twice as much as that obtained in plain nutrient broth. The minimum effective concentration of glucose in increasing the survival time of the spores was found to lie between 10-5M and 10-6M, and the same order of glucose concentration has limited the growth of the spores in a synthetic medium. The other sugars, such as fructose, mannose, galactose, sucrose, maltose, starch, pyruvate, and alpha- glycerophosphate were also effective in elongating the survival time when they were added to nutrient broth in which the heated spores of Bac. natto were subcultured. All these effective sugars were also effective in supporting good growth of Bac. natto spores in the synthetic medium. The effects of vitamins and amino acids in the subculture medium on the survival times of Bac. natto. spores were then studied using a complete synthetic medium. Though the spores of Bac. natto require only biotin for their growth the presence of thiamine and pyridoxal in the subculture medium in addition to biotin was effective in elongating the survival time of the spores. When each of various amino acids was added to the synthetic subculture medium as a sole source of nitrogen, the survival time of Bac. natto spores varied markedly with the kind of the added amino acid. The order of the length of the survival time obtained with each amino acid was as follows: leucine<lysine<histidine and proline<arginine and aspartic acid <glutamic acid<glutamine and asparagine. The last two amino acids gave the longest survival time which could be obtained with the complete synthetic medium containing 18 amino acids. These effects of the composition of subculture medium on the survival time seemed to show that the death of bacterial spores by heat is a gradual chemical process which proceeds step by step with the time of heating and can be reversed (at least in the first stage) under the proper condition of subculture. In order to confirm such a presumption as well as to find out the reason for the linear relationship between spore concentration and survival time, the heat destruction curves (survival curves) of Bac. natto spores were quantitatively determined at various spore concentrations and using various kinds of subculture medium. It was found that the survival curved for each of the different spore concentrations were not parallel to each other, though each of them was a straight line. The death rate constant (k) was then found to be related to the initial spore concentration (N spores per ml) as follows: k=C×(1/N)n×log N When the heated spores of Bac. natto were plated on the different subculture media, the survival curves obtained were all approximately linear, but the slopes of the curves (i. e. the death rate k) varied with the composition of the media.
1. Screening tests for glutamate producing strains were carried out, with the media containing carbohydrate and ammonia source as chief ingredients. Glutamate as well as certain other amino acids was detected by paper chromatography in culture broth of many microorganisms tested. 2. Accumulation of L-glutamate in a significant amount (at least a few mg of glutamate per ml of broth) has been demonstrated by various strains of bacteria, streptomycetes, yeasts, and fungi. The highest level of glutamate production has been obtained by a new species of Micrococcus, yielding as much as 0.25 mole of it from one mole of glucose. 3. The courses of fermentations mainly by known strains of microorganisms are shown. The importances of the cultural condition and strain specificity for the production of amino acids are briefly described.
1. Two high molecular substances, D-1 and D-2 described in this paper, were isolated from natural saké and identified chemically as some kinds of mucoprotein (N-containing polysaccharides). 2. Preparing antiserum reacting with D-complex (D-1 and D-2), the amount of D-equivalent substance contained in commercial saké was determined serologically. 3. The protein turbidity producing substances in saké were identified as D-complex; when the content exceeded 0.015% the turbidity phenomenon occurred. 4. Most Aspergillus fungi produced D-complex even in synthetic media, but the fungi belonging to Penicillium, Mucor, and Rhizopus did not. 5. The role of D-complex in saké taste was discussed.