Induced freezing and desiccation tolerance in the microalgae wild type Nannochloropsis sp. and Scenedesmus dimorphus

The induction of desiccation and freezing tolerance in one marine and one fresh water unicellular algae strains was assayed by culture density and chlorophyll a content when treated cultures were grown in liquid medium. Both strains showed significant growth inhibition after desiccation. Acquisition of cell tolerance to slow desiccation to air dried state facilitated faster recovery growth when compared to fast desiccation. Investigated desiccated algae strains withstand one year freezing at -15°C. Fresh water alga Scenedesmus dimorphus was more tolerant to desiccation and freezing than marine alga of Nannochloropsis sp. and slow-dried cells of frozen Scenedesmus dimorphus strain also displayed significant increase in cell density (p<0.05) and chlorophyll a content (p<0.05) compared to untreated cells. It is anticipated that further research and understanding on the basic mechanisms of induced desiccation and freezing tolerance and empirical development of improved protocols could expand the number and diversity of algal species that can be successfully preserved and stored at -15°C without cryoprotectant.