The viability and recovery of Saccharomyces Cerevisiae after freezing at -84°C with different concentrations of glycerol

Abstract

We studied the survival of Saccharomyces cerevisiae cells after cryopreservation in different concentrations of glycerol. We wanted to determine which concentration of glycerol would be most protective against very cold temperatures. The concentration of glycerol varied from 0%, 5%, and 40%. Counts were done after cryopreservation for one week at -84 ºC to observe the percentage of dead yeast cells. Then we used hemocytometers to count the number of cells per mL. Upon data analysis, we found that immediately after thawing, the cell count per mL did not show any significant difference. However, after a 17-hour recovery period, the 0 and 40% glycerol treatments showed significantly different cell counts. We also looked at the percentage of dead cells after thawing, 1 hour, and 17 hours. Although not significant, the overall trend was that there were more dead cells when glycerol concentration was low. At 40% glycerol, the percentage of dead cells was below 3% for all treatments. The fewest cells died in 40% glycerol, however the yeast with no glycerol in its medium had more cells per mL after 17 hours.