Rao Lei, Zhao Feng, Wang Yongtao, Chen Fang, Hu Xiaosong, Liao Xiaojun
Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural UniversityBeijing, China; National Engineering Research Center for Fruit and Vegetable ProcessingBeijing, China; Key Lab of Fruit and Vegetable Processing, Ministry of AgricultureBeijing, China.
National Engineering Research Center for Fruit and Vegetable ProcessingBeijing, China; Key Lab of Fruit and Vegetable Processing, Ministry of AgricultureBeijing, China.
Front Microbiol. 2016 Sep 7;7:1411. doi: 10.3389/fmicb.2016.01411. eCollection 2016.
The objective of this study was to investigate the inactivation mechanism of Bacillus subtilis spores by high pressure CO2 (HPCD) processing. The spores of B. subtilis were subjected to heat at 0.1 MPa or HPCD at 6.5-20 MPa, and 64-86°C for 0-120 min. The germination, the permeability of inner membrane (IM) and cortex, the release of pyridine-2, 6-dicarboxylic acid (DPA), and changes in the morphological and internal structures of spores were investigated. The HPCD-treated spores did not lose heat resistance and their DPA release was lower than the inactivation, suggesting that spores did not germinate during HPCD. The flow cytometry analysis suggested that the permeability of the IM and cortex of HPCD-treated spores was increased. Furthermore, the DPA of the HPCD-treated spores were released in parallel with their inactivation and the fluorescence photomicrographs showed that these treated spores were stained by propidium iodide, ensuring that the permeability of IM of spores was increased by HPCD. The scanning electron microscopy photomicrographs showed that spores were crushed into debris or exhibited a hollowness on the surface, and the transmission electron microscopy photomicrographs exhibited an enlarged core, ruptured and indistinguishable IM and a loss of core materials in the HPCD-treated spores, indicating that HPCD damaged the structures of the spores. These findings suggested that HPCD inactivated B. subtilis spores by directly damaging the structure of the spores, rather than inducing germination of the spores.
本研究的目的是探究高压二氧化碳（HPCD）处理对枯草芽孢杆菌孢子的灭活机制。将枯草芽孢杆菌的孢子在0.1 MPa压力下加热，或在6.5 - 20 MPa压力、64 - 86°C条件下进行HPCD处理0 - 120分钟。研究了孢子的萌发、内膜（IM）和芽孢皮层的通透性、吡啶-2,6-二羧酸（DPA）的释放以及孢子形态和内部结构的变化。经HPCD处理的孢子并未丧失耐热性，且其DPA释放量低于灭活程度，这表明在HPCD处理过程中孢子未萌发。流式细胞仪分析表明，经HPCD处理的孢子的IM和芽孢皮层的通透性增加。此外，经HPCD处理的孢子的DPA释放与其灭活过程同步，荧光显微照片显示这些处理过的孢子被碘化丙啶染色，这证实了HPCD增加了孢子IM的通透性。扫描电子显微镜照片显示孢子被压碎成碎片或表面出现空洞，透射电子显微镜照片显示经HPCD处理的孢子的核心增大、IM破裂且难以分辨以及核心物质流失，表明HPCD破坏了孢子的结构。这些发现表明，HPCD通过直接破坏孢子结构而非诱导孢子萌发来灭活枯草芽孢杆菌孢子。
