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25 bacterial strains that secrete mucous materials were isolated from sediment obtained from King George Island, Antarctica. Seven of these strains proved capable of producing cryoprotective exopolysaccharides. The strain KOPRI 21653 was selected for the further study. KOPRI 21653 was identified as Pseudoalteromonas arctica as the result of 16S rRNA analysis. The exopolysaccharide, P-21653, was purified by Cetylpyridinium chloride (CPC) and protease treatment from the KOPRI 21653 culture. The sugar components of P-21653 determined to be galactose and glucose, at a ratio of 1:1.5, by GC-MS analysis. The cryoprotective effect of P-21653 was determined by a red blood cell (RBC) LDH assay. In the presence of 0.5% (w/v) P-21653, the Damaged cell ratio of RBC was 20.83±2.83%, after three repeated freeze-thaw cycles. The damaged cell ratio of RBC increased to 26.1%, in five repeated cycle conditions in same concentration of P-21653. However, the damaged cell ratios of RBC were increased (20.83±2.83 - 42.11±7.27 %) in the presence of 0.5 - 0.2% (w/v) P-21653. In addition, at lower concentrations of P-21653 (0.2 - 0.5%), the damaged cell ratios of RBC were more less than generally employed as a RBC cryoprotectant (glycerol), which was utilized at the recommended concentrations (40%). The biochemical characteristics of exo-polysaccharide P-21653 reflect that this compound may be developed as a useful cryo-protectant for use in medical applications.