Cryopreservation of six marine microalgae used in Taiwanese aquaculture

Abstract

AbstractWe investigated the possible conditions to cryopreserve six marine microalgae that are frequently used in Taiwanese aquaculture: Amphora exigua, Isochrysis galbana, Nannochloropsis oculata, Seminavis gracilenta, Skeletonema costatum, and Tetraselmis elliptica. The approaches for microalgae cryopreservation with cooling from room temperature to −40°C, a rate of approximately −1°C/min, and final storage in liquid nitrogen at −196°C are described. We subsequently assessed the viability of cultures of these microalgae after thawing in a 40°C water bath and evaluated the relative survival rates to compare the suitability of cryoprotectant and cryopreservation conditions. We used four concentrations (5%, 10%, 15%, and 20%) of five cryoprotectants, dimethyl sulfoxide (DMSO), methanol (MeOH), glycerine (GLY), ethylene glycol (EG), and propylene glycol (PG), and found that the individual microalgae required distinct cryoprotectant and concentrations. Only S. costatum was not viable after cryopreservation under any of the conditions tested. Relative survival rates were 87.6% (A. exigua), 70.73% (I. galbana), 87.48% (N. oculata), 91.0% (S. gracilenta), and 57.8% (T. elliptica), when using 20% DMSO, 15% Gly, 20% EG, 20% DMSO, and 20% PG as cryoprotectants, respectively. In summary, we established suitable conditions to cryopreserve these five microalgae that will facilitate conserving their genetic diversity.