title: The cryopreservation of Chlorella. 1. Interactions of rate of cooling, protective additive and warming rate.
abstract: The cryoprotective additives glycerol and dimethylsulphoxide were found to be toxic to Chlorella cells at concentrations greater then 2.5% w/v. Polyvinylpyrrolidone, was not damaging up to a concentration of 15%w/v. Chlorella 211/7a had a recovery rate greater than 95% at all rates of cooling studied. With Chlorella 211/8h the survival was lower than 0.1% at all rates examined. The addition of dimethylsulphoxide (5% w/v) to Chlorella 211/8h increased the recovery, particularly at the faster rates of cooling; with polyvinylpyrrolidone (10% w/v) there was an optimum range of cooling rate. Cells of Chlorella 211/7a from the exponential phase of growth were found to be damaged both by a temperature reduction from 25 degrees C to 0 degrees C (thermal shock) and by freezing and thawing. In contrast cells from the stationary phase of growth were resistant to these stresses.
mesh_terms: D002455:Cell Division; D002470:Cell Survival; D002708:Chlorella / Q000254:growth & development; D003451:Cryoprotective Agents; D005615:Freezing; D010461:Peptones; D011205:Povidone; D011309:Preservation, Biological; D013997:Time Factors
chemical_list: D003451:Cryoprotective Agents; D010461:Peptones; D011205:Povidone