Shanghai Engineering Research Center of Food Microbiology, School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China.
Shanghai Engineering Research Center of Food Microbiology, School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China.
J Dairy Sci. 2020 Apr;103(4):3066-3075. doi: 10.3168/jds.2019-17685. Epub 2020 Feb 7.
Although freeze-drying is an excellent method for preserving microorganisms, it inevitably reduces cell activity and function. Moreover, probiotic strains differ in terms of their sensitivity to the freeze-drying process. Therefore, it is necessary to optimize the variables relevant to this process. The pre-freezing temperature is a critical parameter of the freeze-drying process, but it remains unclear whether the optimal pre-freezing temperature differs among strains and protectants. This study explored the effects of 4 different pre-freezing temperatures on the survival rates of different Lactobacillus plantarum strains after freeze-drying in the presence of different protectants. Using phosphate-buffered saline solution and sorbitol as protectants, pre-freezing at -196°C, -40°C, and -20°C ensured the highest survival rates after freeze-drying for AR113, AR307, and WCFS1, respectively. Using trehalose, pre-freezing at -20°C ensured the best survival rate for AR113, and -60°C was the best pre-freezing temperature for AR307 and WCFS1. These results indicate that the pre-freezing temperature can be changed to improve the survival rate of L. plantarum, and that this effect is strain-specific. Further studies have demonstrated that pre-freezing temperature affected viability via changes in cell membrane integrity, membrane permeability, and lactate dehydrogenase activity. In summary, pre-freezing temperature is a crucial factor in L. plantarum survival after freeze-drying, and the choice of pre-freezing temperature depends on the strain and the protectant.
虽然冷冻干燥是保存微生物的一种极好方法，但它不可避免地会降低细胞的活性和功能。此外，益生菌菌株对冷冻干燥过程的敏感性存在差异。因此，有必要优化与该过程相关的变量。预冻温度是冷冻干燥过程的一个关键参数，但不同保护剂的最佳预冻温度是否存在差异仍不清楚。本研究探讨了在不同保护剂存在的情况下，4 种不同预冻温度对不同植物乳杆菌菌株在冷冻干燥后的存活率的影响。使用磷酸盐缓冲盐水和山梨醇作为保护剂，-196°C、-40°C 和-20°C 的预冻温度分别确保了 AR113、AR307 和 WCFS1 菌株在冷冻干燥后的最高存活率。使用海藻糖作为保护剂时，-20°C 的预冻温度可确保 AR113 菌株的最佳存活率，而-60°C 是 AR307 和 WCFS1 菌株的最佳预冻温度。这些结果表明，可以改变预冻温度来提高植物乳杆菌的存活率，并且这种效果是菌株特异性的。进一步的研究表明，预冻温度通过改变细胞膜完整性、膜通透性和乳酸脱氢酶活性来影响细胞活力。总之，预冻温度是冷冻干燥后植物乳杆菌存活的关键因素，预冻温度的选择取决于菌株和保护剂。
