Cole M B, Jones M V, Holyoak C
Unilever Research, Colworth Laboratory, Sharnbrook, Bedford, UK.
J Appl Bacteriol. 1990 Jul;69(1):63-72. doi: 10.1111/j.1365-2672.1990.tb02912.x.
Factorially designed experiments have been used to study the growth and survival of Listeria monocytogenes in different combinations of pH and salt concentrations at ambient and chill temperatures. Survival at low pH and high salt concentration was strongly temperature dependent. The minimum pH values that allowed survival after 4 weeks from an initial 10(4) cells were 4.66 at 30 degrees C, 4.36 at 10 degrees C and 4.19 at 5 degrees C. These limits were salt dependent, low (4-6%) salt concentrations improved and higher concentrations reduced survival at limiting pH values. The lowest pH that allowed a 100-fold increase in cell numbers within 60 d was 4.66 at 30 degrees C but this was increased to 4.83 at 10 degrees C. At 5 degrees C growth occurred at pH 7.0 but not at pH 5.13. Simple predictive models describing the effect of hydrogen-ion and salt concentration on the time for at least a 100-fold increase in numbers at 10 degrees C and 30 degrees C were constructed after analysis of the results for a least squares fit to a quadratic model. The interactions between salt and hydrogen-ion concentration on growth were found to be purely additive.
采用析因设计实验研究了在环境温度和冷藏温度下，单核细胞增生李斯特菌在不同pH值和盐浓度组合中的生长与存活情况。在低pH值和高盐浓度下的存活情况强烈依赖于温度。从初始的10⁴个细胞开始，4周后仍能存活的最低pH值在30℃时为4.66，在10℃时为4.36，在5℃时为4.19。这些限值取决于盐浓度，低（4 - 6%）盐浓度可提高存活率，而在极限pH值下，较高盐浓度则会降低存活率。在60天内细胞数量能增加100倍的最低pH值在30℃时为4.66，但在10℃时升至4.83。在5℃时，pH值为7.0时可生长，而在pH值为5.13时则不能生长。在对结果进行分析并将其与二次模型进行最小二乘拟合后，构建了简单的预测模型，该模型描述了氢离子和盐浓度对在10℃和30℃下细胞数量至少增加100倍所需时间的影响。发现盐与氢离子浓度对生长的相互作用完全是累加性的。
