抄録
(1) The salt-tolerance of soy yeasts acquired by growth in the saline medium with NaCl was easily lost if these yeasts were afterwards once cultured in the ordinary medium without NaCI. Accordingly, in the case of osmophilic soy yeasts salt-tolerance was much dependable upon their cultural environments with or without NaCl. Extreme salt-tolerance could be acquired even when the yeasts were cultured in the medium of NaCl of a relatively low concentration as 5%. Thus it becomes quite apparent that the growth of osmophilic yeasts in the medium of a high concentration of NaCl involves the process of physiological adaptation.
(2) A fall in viability was not observed, contrary to the case of NaCl, when the yeasts cultured in the plain medium were transferred directly to the medium consisting of a high concentration of sugars corresponding to the osmotic pressure of 18% NaCl (135 atm.). The limiting osmotic pressure for their growtl was higher in sugars (220_??_260 atm.) than it NaC1 (150_??_165 atm.).
In these respects, the characteristic of the salt-tolerance of osmophilic soy yeasts differs from that of their sugar-tolerance and it is clear that some other limiting factors beside the osmotic pressure itself, will have effec on their salt-tolerance.
(3) The viability of the yeast cells wher transferred from the plain medium to tht various salt media generally fell. Judgin from the relations between the growth con stant and various concentrations of salts it the medium, the order of toxicity of the salt: for the growth of Zygosaccharomyces major, was estimated as follows:
K+<Na+ <Mg++<Ca++<Li+,
Cl-<S04--_??_NO3-
