High subzero temperature preservation of Spirulina platensis (Arthrospira fusiformis) and its Ultrastucture

Abstract

The high subzero preservation of Spirulina: S. platensis CMU2 and S. platensis GD1 was performed by step wise freezing at 25, 4, and -20°C for 30 min. Then they were preserved at -80°C for seven months with four cryoprotectants: dimethyl sulfoxide, horse serum, calf serum and glycerol. The viability of these two strains and cell concentration was not significantly different (p>0.05). The survival of S. platensis depended on type and concentration of cryoprotectant and thawing temperature. The best condition for high subzero preservation was obtained by using 5% glycerol as cryoprotectant and rapid thawing at 40°C. After high subzero preservation, their ultrastructure such as cell wall, thylakoid and nucleoplasmic region were changed but cryoprotectant helped to protect these important organelles from freeze-induced damage.