The cryopreservation of Chlorella. 4. Accumulation of lipid as a protective factor

Following growth under sub-optimal concentrations of nutrients, cells of Chlorella emersonii accumulated lipid and became more resistant to the damage caused by freezing and thawing. These results suggest that the factor responsible for the cold hardening of some Chlorella spp is not the effect of low temperatures per se but simply that of the reduced metabolic rate. Evidence is given that the post-thaw injury observed following rapid rates of cooling is associated with the vacuole.