Simşek Omer, Buzrul Sencer, Akkoç Nefise, Alpas Hami, Akçelik Mustafa
Institute of Biotechnology, University of Ankara, Ankara, Turkey.
Appl Biochem Biotechnol. 2009 Aug;158(2):387-97. doi: 10.1007/s12010-008-8350-9. Epub 2008 Sep 4.
The purpose of this study is to determine the survival and nisin production behaviors of two strains of Lactococcus lactis under different stress conditions that represent the food ecosystem. In this respect, the survival ratios of two nisin producers were determined under different pH, temperature, NaCl, and bile salt concentrations. Then, nisin production levels of the strains were determined at each stress conditions. Both strains had similar growth or inactivation patterns under the same stress conditions. NaCl and bile salt stresses on the survival ratio of the strains could be successfully described by the exponential decay function, whereas Gaussian function produced good fits for temperature and pH stresses. The nisin activity of two nisin producers (in their mid-exponential and/or early stationary phase) decreased dramatically under all stress conditions, except osmotic (NaCl) and low temperature applications. The results of this study showed that two nisin producers had similar adaptive responses under severe stress conditions, which could be described by appropriate mathematical equations. Moreover, the effect of harsh environment on the nisin activity of L. lactis strains depends on the stress factors applied.
本研究的目的是确定两株乳酸乳球菌在代表食品生态系统的不同应激条件下的存活情况和乳酸链球菌素产生行为。在这方面，测定了两株乳酸链球菌素产生菌在不同pH值、温度、NaCl和胆盐浓度下的存活率。然后，在每种应激条件下测定菌株的乳酸链球菌素产生水平。在相同应激条件下，两株菌具有相似的生长或失活模式。NaCl和胆盐对菌株存活率的胁迫可用指数衰减函数成功描述，而高斯函数对温度和pH胁迫拟合良好。除了渗透压（NaCl）和低温处理外，两株乳酸链球菌素产生菌（处于指数中期和/或稳定前期）的乳酸链球菌素活性在所有应激条件下均显著下降。本研究结果表明，两株乳酸链球菌素产生菌在严重应激条件下具有相似的适应性反应，可用适当的数学方程描述。此外，恶劣环境对乳酸乳球菌菌株乳酸链球菌素活性的影响取决于所施加的应激因素。
