細菌胞子の熱死滅過程における速度定数変化とその解析(その1) : 微生物の熱死滅にかんする動力学的研究-II

概要

論文の詳細を見る
The kinetics of thermal death of Bacillus pumilus spores suspended in phosphate buffer (pH 7) were studied at a temperature of 95℃. Change of death rate constant from high to low took place when experiments were started with spores preserved at a low temperature. Results with spores pre-incubated at various sublethal temperatures led to the assumption that the transformation of S-spores (spores having higher sensitivity, k_1) to R-spores (those having lower sensitivity, k_2) is accelerated by heat.The spores pre-incubated at a sublethal high temperature of e.g. 65℃, tended to show a simple monomolecular thermal death rate (at 95℃) of R-spores. The lower the pre-incubation temperature was, the slower was the transformation as show in Fig. 3. And the longer the time of pre-incubation (at 65℃) was, the less became the fraction (γ) of S-spores in the population as presumed from Fig. 7. Thus, the previously presented model representing a simple "historical system", in which the above transformation occurs at the molecular level, [figure]seemed to accord well the observed results.Analyses according to the equation (cf. previous report), N/N_0=K_1exp{-(k_1+λ)θ}+K_2exp(-k_2θ), were then carried out. The values of K_2(=1-K_1), which is equal to1-{γ(k_1-k_2)/(k_1+λ-k_2)}, were obtained by extrapolating the late phase (k_2-phase) to θ=0,and k_2 could be calculated directly from the slope (Table 3,4). The rate constant of transformation, λ, was calculated by the equation, lnK_1=ln(1-K_2)=const. -λθ^1,where θ' is the time of pre-incubation at a constant temperature. From the results of thermal death rates of spores pre-incubated at various sublethal temperatures was obtained a plot of λ vs. 1/T, which yielded nearly straight line corresponding to the Arrhenius' activation energy of ca.25 Kcal. (cf. Fig. 9) The death rate constant (k_1) of S-spores were obtained either directly or by calculation as listed in Fig. 10.The results of computation according to the above equation for thermal death rate were regarded to be in accord with the experimental results (fig. 10). Reversibility of the transformation (S⇆R) was suggested from the experiments in which thermal death was interrupted in the late linear phase by cooling followed by re-heating at 95℃. (Details of the reversible reaction will be presented in the next report.) Heat-killed spores and the exudates therefrom added to the spore suspension did not cause significant change in thermal death rate. Contrary to the above "historical system", the spores of Bacillus subtilis var. niger was shown to be a "non-historical system" which showed the steady value of death rate constant throughout at a constant temperature and no change of k even in the step-up experiment in which the concentration of survival was raised to ca. 100 fold and re-heated.(presented at the Annual Meeting of the Society of Fermentation Technology, 4 November 1965)
社団法人日本生物工学会の論文
1966-08-25

細菌胞子の熱死滅過程における速度定数変化とその解析(その1) : 微生物の熱死滅にかんする動力学的研究-II

スポンサーリンク

概要

著者

関連論文

スポンサーリンク