Tolerance of three marine microalgae to cryoprotectant dimethy sulfoxide, methanol and glycerol

Abstract

Studies on tolerance limit of cryoprotectants. is of much importance in determining the viability of cells after freezing them at below normal temperatures. <i>Tetraselmis gracilis </i>showed survival on exposure to 5 to 30% <i>(v/v) </i>DMSO, 5 to 25% methanol and 5 to 40% glycerol for periods of up to 2 h. DMSO and methanol were lethal at higher concentrations (>10%)for <i>Chlorella marina </i>and <i>Chaetoceros calcitrans </i>even on exposure for 15 min. At 25%, DMSO was so much lethal that the cells of <i>C</i>. <i>calcitrans </i>and <i>C.</i> <i>marina </i>were dead even after 60 sec. At 20%, all cells were dead within 60 min. Safer

<span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">concentrations for DMSO were at 5% and lower. Methanol incubations significantly reduced cell viability above 25% (60 sec) for <i>T. gracilis, </i>15% (up to 20 min) for <i>C</i>. <i>calcitrans </i>and 20% (up to 60 min) for <i>C</i>. <i>marina. </i>All the three algae could tolerate glycerol even up to 30% (60 min). The survival was highest at 10% concentration of glycerol for 120 min. Based on cell recovery rate after 24 h post thaw and growth rate determination, DMSO at 5% or 10% glycerol are the best treatments for cryopreservation. Glycerol was found to be better than DMSO in all the three cases. Post thaw viability in 5% methanol was almost negligent for all the three strains.</span>