Applied Microbiology Laboratory, Centre for Rural Development and Technology, Indian Institute of Technology Delhi, New Delhi 110016, India.
Int J Food Microbiol. 2010 Oct 15;143(3):205-10. doi: 10.1016/j.ijfoodmicro.2010.08.023. Epub 2010 Aug 31.
The aim of this study was to investigate the antibacterial activity of essential oil (in liquid as well as in vapour phase) and negative air ions (NAI) against Pseudomonas fluorescens. The combined effect of NAI with essential oil vapour was also investigated to determine kill time and morphological changes in bacterial cells. The MIC of Cymbopogon citratus (0.567 mg/ml), Mentha arvensis (0.567 mg/ml), Mentha piperita (1.125 mg/ml) and Eucalyptus globulus (2.25 mg/ml) was studied via the agar dilution method. To estimate the antibacterial activity of essential oils in the vapour phase, agar plates inoculated with P. fluorescens were incubated with various concentrations of each essential oil vapour and zone of inhibition was recorded. Further, in order to assess the kill time, P. fluorescens inoculated agar plates were exposed to selected bactericidal essential oil vapour and NAI, separately, in an air-tight chamber. A continuous decrease in bacterial count was observed over time. A significant enhancement in the bactericidal action was observed by exposure to the combination of essential oil vapour and NAI as compared to their individual action. Scanning electron microscopy was used to study the alteration in morphology of P. fluorescens cells after exposure to C. citratus oil vapour, NAI, and combination of C. citratus oil vapour and NAI. Maximum morphological deformation was found due to the combined effect of C. citratus oil vapour and NAI. This study demonstrates that the use of essential oils in the vapour phase is more advantageous than the liquid phase. Further the antibacterial effect of the essential oil vapours can be significantly enhanced by the addition of NAI. The work described here offers a novel and efficient approach for control of bacterial contamination that could be applied for food stabilization practices.
本研究旨在探讨精油（液态和蒸气态）和空气负离子（NAI）对荧光假单胞菌的抗菌活性。还研究了 NAI 与精油蒸气的联合作用，以确定杀菌时间和细菌细胞的形态变化。通过琼脂稀释法研究了香茅（0.567 mg/ml）、野薄荷（0.567 mg/ml）、胡椒薄荷（1.125 mg/ml）和蓝桉（2.25 mg/ml）的最小抑菌浓度（MIC）。为了评估精油在蒸气相中的抗菌活性，用荧光假单胞菌接种的琼脂平板与各种浓度的每种精油蒸气孵育，并记录抑菌区。此外，为了评估杀菌时间，将荧光假单胞菌接种的琼脂平板分别暴露于选定的杀菌性精油蒸气和 NAI 中，在密封的室中。随着时间的推移，细菌计数持续下降。与单独作用相比，暴露于精油蒸气和 NAI 的组合中观察到杀菌作用显著增强。扫描电子显微镜用于研究暴露于香茅油蒸气、NAI 和香茅油蒸气和 NAI 组合后荧光假单胞菌细胞形态的变化。由于香茅油蒸气和 NAI 的联合作用，发现最大的形态变形。这项研究表明，与液相相比，在蒸气相中使用精油更具优势。进一步通过添加 NAI 可以显著增强精油蒸气的抗菌效果。这里描述的工作提供了一种新颖有效的控制细菌污染的方法，可应用于食品稳定化实践。
