The effects of cryoprotectants on the survival rate of Saccharomyces cerevisiae in a freeze-dried gelatin matrix.

摘要

This study was carried out to determine the effects of cryoprotectants on yeast survival rate. Here, yeast was mixed with the following cryoprotectants: saccharose, hydroxyethylstarch, trehalose, lactose, caboxymethyl cellulose, and kappa -carrageenan, and then frozen at -40 degrees C, -30 degrees C, and -18 degrees C, respectively. The freeze-dried gelatin matrices were cut horizontally into 5 mm thick slices from the bottom and their pore sizes were measured. The freezing temperature (-40 degrees C, -30 degrees C, and -18 degrees C) affected the freezing rate, and the partial freezing rate in the matrix was dependent on the distance. The higher the sample distance was from the bottom, the lower the partial freezing rate. We also found that the cryoprotectant concentration affected the freezing rate. Furthermore, the cryoprotectant and freezing rate affected the different survival rates of the yeast. The highest survival rate occurred with saccharose and trehalose, and was obtained by freezing at -40 degrees C, which depended significantly on the concentration of trehalose. The ice dendrite sizes that formed during freezing at -40 degrees C, -30 degrees C, and -18 degrees C showed a direct relationship with the freezing rate and cryoprotectant concentration. In the samples, the maximum primary ice dendrite size was 215.9 micro m at 1%, and the minimum primary ice dendrite size was 145.6 micro m at 5%, from the experiments at -18 degrees C.