LONG-TERM VIABILITY OF PRESERVED EUKARYOTIC ALGAE

Levels of viability of Chlorella emersonii after storage of dried mate rial for one year were 0.1% on rehydration, all other dried organisms examined in this study failed to recover after prolonged storage. In a ddition, no detectable recovery was observed in any of the algae teste d after storage of freeze-dried cultures. Methods have also been devel oped to cryopreserve a range of microalgae, but no single protocol has been found to be universally satisfactory. Some strains are apparentl y not able to withstand cryopreservation using known methods, whilst o thers may be frozen successfully in the absence of cryoprotectant by p lunging directly into liquid nitrogen. A two-step protocol (cooling to an intermediate subzero temperature prior to plunging into liquid nit rogen) has been used to cryopreserve the majority of strains. Where th is has proven successful, post-thaw viability levels of over 95% have been attained for some algae. This paper demonstrates that, where appl icable, cryopreservation allows the long-term preservation of frozen a lgae with no significant reduction in viability up to 22 years storage .