Efects of Glass Transition Temperature and Disintegration Temperature on Freeze-Drying Survival Rate of Lactobacillus plantarum

Abstract:

[Objective] To determine the effects of glass transition temperature(T_g) and collapse temperature(T_c) of protectants on the freeze-drying survival rate of Lactobacillus plantarum(L. plantarum). [Method] The T_g and T_c of protectants, such as 10% sucrose, 10% sorbitol, and PBS buffer, were measured by differential scanning calorimetry (DSC) and freeze-drying microscopy (FDM). [Result] The relationship of the freeze-drying survival rate of strains with the T_g and T_c of different protectants showed that there was a close relationship of the freeze-drying survival rate of strains with the T_g and T_c of the protectant suspension. Compared to sorbitol and PBS groups, the T_g of sucrose group increased by 7.2 and 7.7 ℃, respectively, while T_c increased by 8.0 and 8.8 ℃, respectively. The freeze-drying survival rate of the sucrose group was the highest, showing improvements of 49.2% and 54.6% over the sorbitol and PBS groups, respectively. Furthermore, a high T_g polysaccharide composite protectant was developed. The T_g and T_c of the optimal composite protectant increased by 4.6 ℃ and 4.4 ℃ compared to those of a single sucrose protectant, and the freeze-drying survival rate was 28.2% higher than that of a single sucrose protectant. [Conclusion] The results showed that the T_g and T_c of different protectants were very different. As the T_g and T_c became higher, the freeze-drying survival rate was higher. Based on T_g, a highly efficient composite protectant was developed, which was beneficial in improving the freeze-drying survival rate of Lactobacillus plantarum.