Abstract: Changes of the amount of intracellular trehalose before and after lyophilization on Saccharomyces cerevisiae HS-2 strain were studied. Diversity survival ratio of HS-2 strain in different suspension medium was compared in this experiment. The results showed as follows: The amount of intracellular trehalose in per gram cells of HS-2 strain went up obviously from 1.58 mg before lyophilization to 9.34 mg after lyophilization.The amount of intracellular trehalose of HS-2 strain in skim milk was higher than that in aseptic water. The cells survival ratio of HS-2 strain was high when the amount of intracellular trehalose after lyophilization was high .At this time , it was able to resist lyophilization. The trehalose added could promote survival ratio of HS-2 strain after lyophilization.It was better when the trehalose concentration was 8 %. Both trehalose and sucrose worked as cryoprotectant when HS-2 strain was lyophilized. Two kinds of sugarg differed in their optimum concentration. The amount of sucrose added was more than that of trehalose added when HS-2 strain reached approximately the same survival ratio after lyophilized.

Key words: T rahalose Saccharomyces cerevisiae Lyophilization Inherent mechanism