生細胞凍結乾燥の2次乾燥における2,3の問題

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The authors focused attention on the equilibrium vapor pressure (p_e) of samples in the course of freeze-drying especially in the secondary drying, since p_e was considered to represent water activity effective in physico-chemical changes by which the cells survived through the primary drying are killed.Firstly the equilibrium vapor pressures of various freeze-dried materials (B. subtilis, Asp. oryzae, S. cerevisiae, mixture of protective substance) were measured by Taylor's manometric method at various temperatures and various levels of water content. Hitherto proposed equations dealing with the relation between p_e and moisture content (e. g. Henderson's equation) were unable to be applied to the experimental results obtained, presumably because the phenomenon was not a simple moisture adsorption but would include some changes in molecular configuration. (Fig. 1). The curve of equilibrium relative humidity of a sample (S. cervisiae) against temperature in the course of heating or cooling suggested the occurrence of irreversible dehydration by heating at 70℃ (Fig. 2). Secondly, by following the time course of vapor pressure (p)of a freeze-dried sample in a closed system, it was established that the dehydration process obeys monomolecular kinetics. The velocity constants (k or k'= log e) were estimated with vatious samples (Fig. 3,Table 1). The rates of dehydration calculated from the velocity constants (equations 3 & 5) were fairly in accord with the experimental results (Table 2).Thirdly, death rate constants (k_v) in the secondary drying of yeast cells were estimated at various levels of temperature and p_e (Table 3). Arrhenius activation energy of thermal death was shown to be ca. 15 kcal, indicating that the process was concerned not with protein denaturation but with ordinary chemical reaction. The values of k_v deoended greatly upon p_e; k_v became lower as p_e was reduced by the secondary drying(Fig. 10).
社団法人日本生物工学会の論文
1964-02-15

生細胞凍結乾燥の2次乾燥における2,3の問題

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