Cold Shock Treatments Affect the Viability of Streptococcus thermophilus BCRC 14085 in Various Adverse Conditions

Streptococcus thermophilus是一種乳酸菌常用來當作菌酛以置備發酵乳製品。在本研究中S. thermophilus BCRC 14085菌體先予以不同條件之冷震處理（10℃，15℃或20℃下處理2h或4h）。然後探討冷震處理影響其於後續致死壓力如低（5，-20℃），高溫（58℃），酸性pH（2.5），高滲透壓（75%山梨醇）與高乙醇濃度（20%）之存活情形。結果顯示S. thermophilus之冷震效應會因其所受冷震處理條件及致死壓力之不同而不同。與控制組相比，經10℃2，4h，或15℃2h冷震之S. thermophilus在-20℃下之存活較高，但20℃-4h冷震菌體之存活則較低。冷震處理且不影響其於5℃下之存活。在58℃下，經l0℃冷震處理者其存活菌數增加，但其他冷震處理者存活菌數則減少。先在10或15℃下冷震處理2或4h提高S. thermophilus菌體在高滲透壓及高乙醇濃度下之耐受性。經過l0℃冷震之菌體在pH 2.5下亦顯示有較高之存活性。如此適當冷震所誘發增強S. thermophilus對壓力之抵抗力將提供在食品工業上潛在之好處。

關鍵字

Streptococcus thermophilus ；冷震處理；後續致死壓力

並列摘要

Streptococcus thermophilus, is a lactic acid bacterium, commonly used as a starter organism for the manufacture of fermented dairy products. In this study, S thermophilus BCRC 14085 was first subjected to different cold shock treatments (10, 15 and 20 for 2 and 4 h). The viabilities of cold-shocked cells in subsequent lethal stress environments such as low temperature (5,-20°C), high temperature (58°C), acidic pH (2.5), high osmotic pressure (75% sorbitol) and high ethanol (20%), were then compared with the controls. Results revealed that the cold shock response of S. thermophilus varied with the cold shock treatments and types of lethal stress. Compared with control cells, S. thermophilus cold-shocked at 10°C for 2 and 4 h, or 15°C for 2 h showed enhanced survival, while the cold-shocked cells at 20°C for 4 h exhibited reduced survival at -20℃. Cold shock did not affect the viability of S, thermophilus at 5°C. Regardless of the duration of cold shock, the 10°C cold-shocked cells exhibited enhanced survival while other cold shocked cells showed reduced viability at 58°C. Pre-adaptation at 10 or 15°C for 2 or 4 h enhanced S.thermophilus's tolerance against high osmophilic pressure and 20% ethanol. Finally, the 10°C cold-shocked cells showed enhanced survival at pH 2.5. Thus, the enhanced stress resistance of S. thermophilus induced by an appropriate cold shock treatment may yield its potential benefits in the food industry.

並列關鍵字

Streptococcus thermophilus ； cold shock treatments ； subsequent lethal stresses

國際替代計量

Cold Shock Treatments Affect the Viability of Streptococcus thermophilus BCRC 14085 in Various Adverse Conditions

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