Cryopreservation of Marine Diatom Algae by Encapsulation-Vitrification

In this paper, the cryopreservation of marine diatom algae (Nitzschia closterium f. minutissima Allen and Nelson and Chaetoceros muelleri Lemmermann) using the encapsulation-vitrification technique was studied. The effect of the composition the vitrification solution, of the concentration of the loading solution, of the duration of loading and dehydration treatments and of the washing method on viability of algae was investigated. The results showed that PVS2 was suitable for cryopreservation of these diatoms. In the case of N. closterium, the highest viability (73.8%) was obtained when alginate beads containing the algal cells were loaded with 50% PVS2 for 60 min, dehydrated with 100% PVS2 for 60 min at 0°C, frozen and rewarmed rapidly and washed with a 1.2 M sucrose solution for 30 min at 20°C. In the case of C. muelleri, the highest viability (48.2%) was obtained when alginate beads containing the algal cells were loaded with 50% PVS2 for 40 min, dehydrated with 100% PVS2 for 60 min at 0°C, frozen and rewarmed rapidly and washed with a 1.2 M sucrose solution for 30 min at 20°C.