Laboratory of Epidemiology and Microbiology, Bacteriology and Biotechnology Development Group, Pasteur Institute of Tunisia (IPT), Belvédère, 1002 Tunis, Tunisia.
Food Microbiol. 2013 Dec;36(2):320-6. doi: 10.1016/j.fm.2013.06.021. Epub 2013 Jul 8.
Spores of Bacillus sporothermodurans are known to be contaminant of dairy products and to be extremely heat-resistant. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk stability. In this study, the nutrient-induced germination of B. sporothermodurans LTIS27 spores was studied. Testing the effect of 23 nutrient elements to trigger an important germination rate of B. sporothermodurans spores, only D-glucose, L-alanine, and inosine were considered as strong independent germinants. Both inosine and L-alanine play major roles as co-germinants with several other amino acids. A central composite experimental design with three factors (L-alanine, D-glucose, and temperature) using response surface methodology was used to optimize the nutrient-induced germination. The optimal rate of nutrient-induced germination (100%) of B. sporothermodurans spores was obtained after incubation of spore for 60 min at 35 °C in presence of 9 and 60 mM of D-glucose and L-alanine, respectively. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination, which will be beneficial for screening of B. sporothermodurans in milk after induction their germination. Moreover, the chosen method of optimization of the nutrient-induced germination was efficient in finding the optimum values of three factors.
芽胞杆菌 sporothermodurans 的孢子已知是奶制品的污染物，并且具有极强的耐热性。在热处理之前诱导内生孢子发芽可能是一种有效方法，可以灭活这些细菌并确保牛奶的稳定性。在这项研究中，研究了 sporothermodurans LTIS27 孢子的营养诱导发芽。测试了 23 种营养元素对触发 sporothermodurans 孢子重要发芽率的影响，只有 D-葡萄糖、L-丙氨酸和肌苷被认为是强独立发芽剂。肌苷和 L-丙氨酸都作为与其他几种氨基酸的共发芽剂发挥主要作用。使用响应面法的三因素（L-丙氨酸、D-葡萄糖和温度）中心复合实验设计用于优化营养诱导发芽。在 35°C 下孵育孢子 60 分钟，分别存在 9 和 60 mM 的 D-葡萄糖和 L-丙氨酸时，可获得 sporothermodurans 孢子的最佳营养诱导发芽率（100%）。本研究的结果有助于预测环境因素和营养物质对孢子发芽的影响，这将有助于在诱导其发芽后筛选牛奶中的 sporothermodurans。此外，选择的营养诱导发芽优化方法能够有效地找到三个因素的最佳值。
