Effect of heat shock or cold shock treatment on the resistance of Lactococcus lactis to freezing and lyophilization
Effect of heat shock or cold shock treatment on the resistance of Lactococcus lactis to freezing and lyophilization
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DOI：
10.1006/cryo.1999.2190
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发表时间：
1999-08-01
期刊：
影响因子：
2.7
通讯作者：
Lin, C
中科院分区：
文献类型：
--
作者：
Broadbent, JR;Lin, C
本研究探讨了热休克和冷休克处理对商品乳酸乳球菌抗性的影响。Lactis和L.lactis SSP.奶油干酪发酵剂菌种要冷冻和冷冻干燥。在不同的乳球菌中，在-60摄氏度下24小时的耐寒能力是不同的，但在大多数菌株中，42摄氏度25分钟的热休克可以显著提高(P<；0.05)。Lactis)或39℃(L.lactis SSP.此外，显著提高乳球菌耐冷性的应激处理(P<；0.05)提高了大多数菌株对冷冻干燥的抵抗力。当在含有红霉素的肉汤中进行胁迫处理时，没有检测到对冷冻或冷冻干燥的更大抵抗力，这表明胁迫诱导蛋白是细胞保护所必需的。应激处理细胞的膜脂肪酸分析表明，细胞抗冻性和冻干性的增强可能与细胞膜脂质成分的变化有关。热休克细胞的19：0环丙烷脂肪酸含量高于对照细胞，而冷休克TELS细胞的饱和脂肪酸与不饱和脂肪酸的比例较低。然而，其他因素也必须参与细胞保护，因为在那些对冷冻和冷冻干燥的抵抗力没有通过热或冷冲击处理提高的菌株中也检测到了类似的膜脂组成的变化。(C)1999年学术出版社。
This study investigated the effect of heat shock or cold shock treatment on the resistance of commercial Lactococcus lactis ssp. lactis and L. lactis ssp. cremoris cheese starter bacteria to freezing and freeze-drying. The ability to withstand freezing at -60 degrees C for 24 h was variable among lactococci, but could be significantly (P < 0.05) improved in most strains by a 25-min heat shock at 42 degrees C (L. lactis ssp. lactis) or 39 degrees C (L. lactis ssp. cremoris) or by a 2-h cold shock at 10 degrees C. In addition, stress treatments that improved lactococcal cryotolerance significantly (P < 0.05) enhanced the resistance of most strains to lyophilization. Greater resistance to freezing or lyophilization was not detected when stress treatments were performed in broth that contained erythromycin, which indicated that stress-induced proteins were required for cell protection. Membrane fatty acid analysis of stress-treated cells suggested that enhanced resistance to freezing and lyophilization may be related to changes in cell membrane lipid composition. Heat-shocked cells had a higher 19:0 cyclopropane fatty acid content than control cells, and cold-shocked tells contained a lower ratio of saturated to unsaturated fatty acids. Other factors must also be: involved in cell protection, however, because similar changes in membrane lipid composition were detected in strains whose resistance to freezing and lyophilization was not improved by heat or cold shock treatment. (C) 1999 Academic Press.