柑橘精油纳米乳的制备及对金黄色葡萄球菌的抑制活性研究

Preparation of citrus essential oil nanoemulsions and its antibacterial activity against Staphylococcus aureus

以抑菌圈直径试验筛选出的对金黄色葡萄球菌抑制效果较好的3种柑橘(佛手柑、甜橙、蜜柚)精油为油相,以吐温80为乳化剂,去离子水为水相,通过相转变法制备纳米乳。结果表明,3种柑橘精油纳米乳的配方:精油质量分数为6%、吐温80质量分数为24%、去离子水质量分数为70%,此条件下制备的纳米乳平均粒径为10~20 nm,粒径分布较均匀。抑菌圈直径试验和最小抑菌浓度试验表明,将3种柑橘精油制备成纳米乳,其抑菌活性均得到提升,其中佛手柑精油纳米乳表现出最强的抑制金黄色葡萄球菌效果,最小抑菌浓度和最小杀菌浓度均为3.75 mg/mL,抑菌活性为纯精油的2.5倍。扫描电镜结果显示,相对于纯精油,佛手柑精油纳米乳对菌体结构的破坏更显著,说明佛手柑精油纳米乳对食源性病菌金黄色葡萄球菌具有良好的抑制作用。

Citrus essential oil,as a natural extract with a broad-spectrum antibacterial effect,can effectively inhibit the growth of food-borne pathogens,but its wide application is limited due to its easy volatilization and poor water solubility.In this study,through the inhibition zone diamater test of three kinds of citrus(bergamot,sweet orange,honey pomelo)essential oilswith good antibacterial effect on Staphylococcus aureus wasusedas the oil phase.Tween 80 was used as the emulsifier,with deionized water used as the water phase,and the nanoemulsions was prepared by phase transformation method.According to the pseudo-ternary phase diagrams,the formulas of three citrus essential oil nanoemulsions were obtained,i.e.6%essential oil,24%Tween 80 and 70%deionized water.The average particle sizes of the prepared nano-emulsions were between 10~20 nm,and the particle size distributionswere uniform.The inhibition zone diameter test and the minimum inhibition concentration test showed that the antibacterial activity of the three citrus essential oils into nano-emulsions was improved,among which the bergamot essential oil nanoemulsion showed the strongest antibacterial effect against S.aureus,and the minimum inhibitory concentration and the minimum bactericidal concentration were both 3.75 mg/mL.The inhibitory activity was 2.5 times that of the pure essential oil.Scanning electron microscopy results showed that,compared with pure essential oil,bergamot essential oil nano-emulsion damaged the bacterial structure more significantly.This showed that the bergamot essential oil nano-emulsion had a good antibacterial effect on the food-borne pathogen S.aureus.