RESUMEN
ve To study the growth curve of Alexandrium tamarense and the toxicity of paralytic shelfish poisoning(PSP) selected in different growth phases, as well as to quantitatively analyze the toxins and compare the different efficiency of breaking cell wall and their virtues and defects between freezing-thawing method and supersonic method, and to provide theoretical basis for the selection of the methods for extraction of PSP. Methods Cells were collected by suction filter, cell wall was broken by freezing-thawing method and supersonic method, the toxicities of Alexandrium tamarense among different growth phases were detected and compared. Results The growth of Alexandrium tamarense typically showed three phases which included a lag phase(0~9 days), an exponential growth phase(10~18 days), and a stationary phase(19~22 days) . The maximum toxicity of cells in the stationary phase appeared, especially in day 21 when the population of cells reached to 9.43?10-6 MU/cell, although the cells in the exponential phase grew fastest. Toxicity of the cells in the lag phase broken by freezing-thawing method was more stronger than that by supersonic method, that meant the toxicity of cells was lowered after the supersonic treatment. In additional, the filtering method for collecting cells presented a lower recovery rate of average 69.0% . Conclusion As for the comparing of freezing-thawing method and supersonic method, it was found that, when cells were in the same phase, the supersonic method had remarkable advantages, but it also had the disadvantage of lowering the tox-icity of cells. When in the same condition of growth and method of fragmentation, cells in the lag phase were broken most easily, and cells in the stationary phase were more difficult to be broken than those in the other two phases. Toxicity of cells was larger and larger with the time of incubation. The toxicity of cells in the lag phase had reached a higher intensity, although toxicities of cells in the next two phases would increase a little.