Department of Quantum and Radiation Engineering, Graduate School of Engineering, Osaka Prefecture University.
Research Center of Microorganism Control, Organization for Research Promotion, Osaka Prefecture University.
J Microorg Control. 2023;28(1):3-13. doi: 10.4265/jmc.28.1_3.
This study aimed to clarify how the phenolic monoterpene carvacrol and its structural isomer thymol both as essential oil components (EOCs) inhibit the germination of Bacillus subtilis spore. Germination was evaluated by the OD reduction rate in a growth medium and phosphate buffer containing either l-alanine (l-Ala) system or l-asparagine, d-glucose, d-fructose plus KCl (AGFK) system. The germination of the wild-type spores in the Trypticase Soy broth (TSB) was found to be greatly inhibited by thymol than by carvacrol. Such a difference in the germination inhibition was confirmed by the dipicolinic acid (DPA) release from germinating spores in the AGFK buffer system, but not in the l-Ala system. Similar to the wild-type spores, no difference in the inhibitory activity between the EOCs was also indicated with the gerB, gerK-deletion mutant spores in the l-Ala buffer system and the above substantial difference was also done with the gerA-deleted mutant spores in the AGFK. Fructose was found to release spores from the EOC inhibition and inversely even stimulated. Increased concentrations of glucose and fructose partially suppressed the germination inhibition by carvacrol. The results obtained should contribute to the elucidation of the control effects of these EOCs on bacterial spores in foods.
本研究旨在阐明作为精油成分(EOCs)的单萜酚类化合物香芹酚及其结构异构体百里酚如何抑制枯草芽孢杆菌孢子的萌发。通过在含有 l-丙氨酸(l-Ala)系统或 l-天冬酰胺、d-葡萄糖、d-果糖加 KCl(AGFK)系统的生长培养基和磷酸盐缓冲液中测量 OD 降低率来评估萌发。发现百里酚比香芹酚更能强烈抑制 Trypticase 大豆肉汤(TSB)中野生型孢子的萌发。在 AGFK 缓冲液系统中从萌发孢子中释放出的二吡啶甲酸(DPA)证实了这种萌发抑制的差异,但在 l-Ala 系统中没有。类似于野生型孢子,在 l-Ala 缓冲液系统中 gerB、gerK 缺失突变体孢子和 AGFK 中的 gerA 缺失突变体孢子中,EOC 之间的抑制活性没有差异。果糖被发现能使孢子从 EOC 抑制中释放出来,甚至起到了相反的刺激作用。葡萄糖和果糖浓度的增加部分抑制了香芹酚的萌发抑制作用。所得结果应有助于阐明这些 EOC 对食品中细菌孢子的控制作用。