Cryopreservation Of 3 Green Algae Used As Food In Mariculture By Encapsulation-dehydration

Cryopreservation of 3 green algae used as food in mariculture by encapsulation-dehydrationDunaliella tertiolecta, Platymonas helgolandica and Pyramimonas sp. were cryopreserved in liquid nitrogen using encapsulation-dehydration. Algal cells in different phases were encapsulated in 3% Ca-alginate beads with 30‰ NaCl, Beads were desiccated with silica gel then directly immersed in liquid nitrogen. The cell viability after warming was evaluated by chlorophyll content. The main factors influencing the cell viability, such as water content of beads, dehydration rate, preculture and recovery methods were studied, The results are as follows:(1) Effect of algal phases on cell viability:The result of different phases on cell viability shows that the cell viability in the exponential growth phase of Dunaliella tertiolecta is higher than that in the stationary growth phase. However, The cell viability of Platymonas helgolandica and Pyramimonas sp. is higher in the stationary growth than in the exponential growth phase.(2) Effect of dehydration rate:At different dehydration rates (a water reduction per hourof 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 2.0%, 19.5%), three algae all obtained highest viability at the dehydration rate of 0.9%.(3) Effect of water content on cell viability:At an average dehydration rate of 0.9% water content/h, water contents in beads have more effects on cell viability after thawing. The three Algae Dunaliella tertiolecta, Platymonas helgolandica and Pyramimonas sp. have optimal water content when they were dehydrated to 40% of water content. Their highest viability are 60.32%, 37.06%, 34.05% respectively. (4) Effect of different recovery methods after thawing After thawing, the highest viability was obtained when Dunaliella tertiolecta and Platymonas helgolandica beads of were incubated in freezing dehydration tube for 24h in darkness at room temperature. As to Pyramimonas sp., the suitable recovery method was to put incubate beads in freezing dehydration tube for 12h in darkness at room temperature.