Cui Shumao, Hu Mengyu, Sun Yuanyuan, Mao Bingyong, Zhang Qiuxiang, Zhao Jianxin, Tang Xin, Zhang Hao
State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
School of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
Microorganisms. 2022 Dec 23;11(1):48. doi: 10.3390/microorganisms11010048.
Freeze-drying is a commonly used method in commercial preparations of lactic acid bacteria. However, some bacteria are killed during the freeze-drying process. To overcome this, trehalose and lactose are often used as protective agents. Moreover, high-density culture is an efficient way to grow bacterial strains but creates a hypertonic growth environment. We evaluated the effects of trehalose and lactose, as a primary carbon source or as an additive in fermentation, on the freeze-drying survival of FXJCJ6-1, 173-1-2, and CCFM1040. Our results showed that FXJCJ6-1 accumulated but did not use intracellular trehalose in a hypertonic environment, which enhanced its freeze-drying resistance. Furthermore, genes that could transport trehalose were identified in this bacterium. In addition, both the lactose addition and lactose culture improved the freeze-drying survival of the bacterium. Further studies revealed that the added lactose might exert its protective effect by attaching to the cell surface, whereas lactose culture acted by reducing extracellular polysaccharide production and promoting the binding of the protectant to the cell membrane. The different mechanisms of lactose and trehalose in enhancing the freeze-drying resistance of bacteria identified in this study will help to elucidate the anti-freeze-drying mechanisms of other sugars in subsequent investigations.
冷冻干燥是乳酸菌商业制剂中常用的方法。然而，一些细菌在冷冻干燥过程中会死亡。为克服这一问题，海藻糖和乳糖常被用作保护剂。此外，高密度培养是培养细菌菌株的有效方法，但会创造一个高渗生长环境。我们评估了海藻糖和乳糖作为主要碳源或发酵添加剂对FXJCJ6-1、173-1-2和CCFM1040冷冻干燥存活率的影响。我们的结果表明，FXJCJ6-1在高渗环境中积累但不利用细胞内海藻糖，这增强了其抗冷冻干燥能力。此外，在这种细菌中鉴定出了能够转运海藻糖的基因。此外，添加乳糖和以乳糖培养均提高了该细菌的冷冻干燥存活率。进一步研究表明，添加的乳糖可能通过附着在细胞表面发挥其保护作用，而以乳糖培养则通过减少细胞外多糖的产生以及促进保护剂与细胞膜的结合来发挥作用。本研究中确定的乳糖和海藻糖增强细菌抗冷冻干燥能力的不同机制，将有助于在后续研究中阐明其他糖类的抗冷冻干燥机制。
