Assessment of heat resistance of bacterial spores from food product isolates by fluorescence monitoring of dipicolinic acid release
Assessment of heat resistance of bacterial spores from food product isolates by fluorescence monitoring of dipicolinic acid release
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DOI：
10.1128/aem.71.7.3556-3564.2005
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发表时间：
2005-07-01
影响因子：
4.4
通讯作者：
Brul, S
中科院分区：
文献类型：
--
作者：
Kort, R;O'Brien, AC;Brul, S
本研究旨在开发一种方便、快速的光学方法来监测食品样品中细菌内生孢子的湿热抗性。我们测试了测量丰富的孢子成分二吡啶酸（DPA）释放量作为热失活探针的可行性。从实验室型枯草芽孢杆菌168和两个食品分离株枯草芽孢杆菌A163和芽孢热改造芽孢杆菌IC4中分离到孢子。来自实验室菌株的孢子的耐热性明显低于来自两种食品分离株的孢子。在105℃、120℃和131℃条件下，菌株168、A163和IC4孢子在Trypticase大豆琼脂上的还原时间（D值）分别为1.4、0.7和0.3 min。估计的Z值分别为6.3摄氏度、6.1摄氏度和9.7摄氏度。监测了三种孢子作物的DPA释放程度随孵育时间和温度的变化。DPA浓度是通过在微滴板荧光计中测量荧光铽-DPA复合物在545 nm处的发射来确定的。我们将孢子耐热性定义为临界DPA释放温度（T-c），即在固定孵育时间内释放一半DPA含量的温度。我们发现芽孢杆菌菌株168、A163和IC4孢子的T值分别为108℃、121℃和131℃。在这些观察的基础上，我们建立了一个定量模型，描述了实验确定的DPA释放程度和孢子失活程度的时间和温度依赖性。该模型预测每个灭活孢子的DPA释放率。此外，还发现孢子失活率、DPA释放持续时间和DPA释放延迟的温度依赖参数值存在显著差异。
This study is aimed at the development and application of a convenient and rapid optical assay to monitor the wet-heat resistance of bacterial endospores occurring in food samples. We tested the feasibility of measuring the release of the abundant spore component dipicolinic acid (DPA) as a probe for heat inactivation. Spores were isolated from the laboratory type strain Bacillus subtilis 168 and from two food product isolates, Bacillus subtilis A163 and Bacillus sporothermodurans IC4. Spores from the lab strain appeared much less heat resistant than those from the two food product isolates. The decimal reduction times (D values) for spores from strains 168, A163, and IC4 recovered on Trypticase soy agar were 1.4, 0.7, and 0.3 min at 105 degrees C, 120 degrees C, and 131 degrees C, respectively. The estimated Z values were 6.3 degrees C, 6.1 degrees C, and 9.7 degrees C, respectively. The extent of DPA release from the three spore crops was monitored as a function of incubation time and temperature. DPA concentrations were determined by measuring the emission at 545 nm of the fluorescent terbium-DPA complex in a microtiter plate fluorometer. We defined spore heat resistance as the critical DPA release temperature (T-c), the temperature at which half the DPA content has been released within a fixed incubation time. We found T, values for spores from Bacillus strains 168, A163, and IC4 of 108 degrees C, 121 degrees C, and 131 degrees C, respectively. On the basis of these observations, we developed a quantitative model that describes the time and temperature dependence of the experimentally determined extent of DPA release and spore inactivation. The model predicts a DPA release rate profile for each inactivated spore. In addition, it uncovers remarkable differences in the values for the temperature dependence parameters for the rate of spore inactivation, DPA release duration, and DPA release delay.