Freeze-dried Algae Research Articles

Factors affecting the viability of lyophilized algae

Summary Three species of blue-green algae ( Nostoc muscorum, Gloeocapsa alpicola , and G. membranina ) and four cultures of green algae (two cultures of Chlorella sp. from the Antarctic, and Chlorella pyrenoidosa and Stichococcos bacillaris ) have been successfully lyophilized and the viability studied as a function of temperature during the drying period, length of the drying period, and length of the storage period. N. muscorum was equally viable in all experiments and showed no decline in viability during 5 years of storage at +25°C. All the green algae showed a significant decline in viability during the same period of storage. This decline in viability could not be correlated with the conditions existing during the drying period. C. pyrenoidosa did not survive freeze-drying when the cells were maintained below −25°C throughout the drying period, whereas, it showed good survival in samples dried in a desiceator at room temperature with suspensions remaining in the frozen state only through removal of heat by sublimation of ice. Lyophilized samples of algae can survive elevated temperatures which are lethal to the hydrated cells. The viability of lyophilized samples of N. muscorum was unaffected by heating at 100°C for 10 min. The ability of Chlorella sp. to survive heating at 100°C was correlated with the length of the drying period. Samples dried for 12 to 46 hrs did not survive after heating, whereas those dried from 59 to 101 hrs did survive, with the greatest viability being recorded in those dried for 101 hrs. Evidence is presented to show that the decline of viability in freeze-dried algae is temperature-dependent and that storage in unsealed tubes exposed to dry air results in a rapid decline in viability.