EFFECT OF SUPERSATURATION RATIO ON THE GROWTH-RATE AND NUMBER OF PROTEASE THERMOLYSIN CRYSTALS

The effect of initial supersaturation ratio on the growth rate and num ber of protease thermolysin crystals was investigated at the initial s upersaturation ratio of 8.9 to 17.9 and pH 7.0. The average diameter a nd number of thermolysin crystals were measured by dynamic light scatt ering during crystallization. The crystallization of thermolysin proce eded through two successive steps: the formation of primary particles and the formation of large crystals from the primary particles. The si ze of the primary particles was not affected by the initial supersatur ation ratio and was about 60 nm in diameter. The growth rate of thermo lysin crystals had a maximum at the initial supersaturation ratio of 9 .5. On the other hand, the number of thermolysin crystals decreased wi th an increase of the initial supersaturation ratio, and turned to inc rease through a minimum at the initial supersaturation ratio of 13.4. The dependencies of the size and number of thermolysin crystals on the initial supersaturation ratio were explained hy the successive two st ep mechanism of crystallization.