Some experiments were carried out in order to investigate the resistance of yeast. cells against low temperature.
Cells of Saccharcmyces cerevisiae, cultured and suspended in various sorts of media, were fro-zen and thawed, varying the conditions of cooling and warming. After thawing, the viability, fermentation and catalase activity of organisms thus treated were measured.
The results obtained were as follows:
1) The greater the cooling rate was, the more severely were organisms injured.
2) At the warming rate within 3°_??_15°/min, there was no marked difference in the effect on the organisms.
3) The cells, grown in the serial successive broth cultures with hypertensional concentration of glucose, or suspended in hypertensional media, were more intensively affected by freezing and thawing than those in hypotensional conditions.
4) When the yeast suspensions were repeatedly frozen and thawed, almost all of the orga-nisms were damaged by the first or second treatment.