Abstract Lactococcus lactis ssp. cremoris and Lactobacillus acidophilus NCFM were cultured in growth media supplemented with CaCl2 to induce intracellular accumulation of Ca2+. Both strains grown with 10 mM Ca2+ demonstrated enhanced thermal stability, with increased survival after spray drying from 49.9% to 64.9% for the coccus and from 35.5% to 43.3% for the rod. The increased intracellular Ca2+ level was confirmed with murexide assay. Adding Ca2+ in the reconstitution solution could not improve the viability of spray dried cells at extended storage stages. We hypothesized that the over-presence of intracellular Ca2+ might stimulate the activity of heat shock proteins, increasing cell survival towards heat stress. The positive effect of calcium partly explained the protective mechanism of some calcium-containing protectants. The reported approach, which improves the stress tolerance of cells, can be combined with the optimization of spray drying conditions and protectant formulation for developing a consolidated powder production scheme.

中文翻译：

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通过细胞内钙的积累提高喷雾干燥过程中乳酸菌的热稳定性

摘要 乳酸乳球菌 ssp。cremoris 和嗜酸乳杆菌 NCFM 在补充有 CaCl2 的生长培养基中培养，以诱导细胞内 Ca2+ 的积累。用 10 mM Ca2+ 生长的两种菌株都表现出增强的热稳定性，喷雾干燥后球菌的存活率从 49.9% 增加到 64.9%，杆的存活率从 35.5% 增加到 43.3%。增加的细胞内 Ca2+ 水平通过 murexide 测定得到证实。在重构溶液中添加 Ca2+ 不能提高喷雾干燥细胞在延长储存阶段的活力。我们假设细胞内 Ca2+ 的过度存在可能会刺激热休克蛋白的活性，从而增加细胞对热应激的存活率。钙的积极作用部分解释了一些含钙保护剂的保护机制。