Diatom cultivation and lipid productivity for non-cryopreserved and cryopreserved cells
Ege University, Faculty of Engineering, Department of Bioengineering, TR 35100 Bornova-Izmir, Turkey
Many freshwater and marine algae can be cryopreserved, but typically with lower post-thaw viability levels. However, most of the algae groups (dinoflagellates, cryptophytes, synurophytes, and raphidophytes) cannot be successfully cryopreserved in these days. Marine diatoms can be cryopreserved and frequently have shown great viability. The aim of this study is to compare the cultivation and lipid productivity for non-cryopreserved and cryopreserved marine diatom cells. Diatoms preserved in the EGEMACC (Ege University Microalgae Culture Collection) are usually maintained by serial sub-culturing. In this study, the cryopreservation of marine diatom algae (Amphora cf. capitellata, Cylindrotheca closterium, Nanofrustulum shiloi) using the passive freezing system procedure was studied. Investigation into the cause of the freezing injury at the cellular level was made at different salt concentrations. Passive freezing method used in sea salts liquid media at the percentage of 1%, 2% and 3% containing cryoprotectant of 10% Me2SO for six months in liquid nitrogen. C. closterium was obtained with the highest viability however N. shiloi was revival extended period of time. All of the diatom cells were grown in 1 L sterile bottle containing 900 mL of F/2 medium under the light intensity of 20 μmol photons m-2 s-1 at 22 ± 2 °C with the air flow rate of 1 L/min for 15 days. The growth rate and biomass productivity were determined at the end of the batch production process. Also, lipid content of A. capitellata was obtained at the highest concentration compared to that of the other diatoms.