紫苏精油抑制灰绿曲霉的活性与机理

Activity and Mechanism of Perilla Essential Oil in Inhibiting Aspergillus glaucus

紫苏精油(perilla essential oil,PEO)作为一种健康且高效抑菌的天然植物精油,被广泛应用于食品行业。本实验研究了紫苏精油对稻谷中灰绿曲霉的最小抑制浓度(minimum inhibitory concentration,MIC)和最小杀菌浓度,通过菌丝干质量、孢子萌发测定实验分析了不同剂量PEO对霉菌的抑菌活性;测定不同PEO剂量处理后灰绿曲霉麦角固醇质量分数的变化,通过扫描电子显微镜观察PEO对灰绿曲霉表面形态的影响;测定线粒体ATP酶活力,采用碘化丙啶(propidium iodide,PI)染色霉菌细胞,并用流式细胞仪分析PEO处理对细胞膜完整性的影响;此外,通过傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)法检测灰绿曲霉菌丝官能团的变化,从而探究PEO对灰绿曲霉的抑菌机理。结果表明:紫苏精油对灰绿曲霉的MIC为0.5μL/mL;经不同剂量紫苏精油处理的灰绿曲霉生长均被明显抑制,萌发率降低,菌丝干质量减少,0.5、1 MIC和2 MIC紫苏精油处理组的灰绿曲霉菌丝抑制率从81.75%升高至93.07%,麦角固醇质量分数也随精油剂量增加而明显降低;通过扫描电子显微镜观察可知,PEO处理的灰绿曲霉菌丝出现凹陷和孔洞,随着精油剂量的增加,菌丝体出现干瘪扭曲;在检测PEO处理的灰绿曲霉线粒体ATP酶活力时发现,与对照组相比,PEO处理组酶活力均有一定程度的降低;用PI染色时发现,孢子的细胞膜完整性降低,染色孢子的数量随PEO剂量的升高而增加;通过FTIR分析发现处理组菌丝体中有机配体基团发生明显变化,这暗示着磷脂、蛋白质和脂质的损伤。

Perilla essential oil(PEO)is a natural,healthy and highly effective plant essential oil which is widely used in the food industry.In this paper,the minimum inhibitory concentration(MIC)and minimum bactericidal concentration of PEO against Aspergillus glaucus in rice were studied.The antifungal activity of different concentrations of PEO was tested by measuring the dry mass of hyphae and percentage spore germination.The change of ergosterol content in the plasma membrane of Aspergillus glaucus was determined.The effect of PEO on the surface morphology of Aspergillus glaucus was observed by scanning electron microscope(SEM).The activity of mitochondrial ATPase was measured.The spores were stained with propidium iodide(PI)to detect the effect of PEO treatment on cell membrane integrity by flow cytometry.The change of functional groups in Aspergillus glaucus hyphae was detected by Fourier transform infrared spectroscopy(FTIR),and the antifungal mechanism of PEO was explored.The results showed that the MIC of PEO against Aspergillus glaucus was 0.5μL/mL.The growth of Aspergillus glaucus was significantly inhibited by all concentrations of PEO,and the percentage spore germination rate and dry hyphal mass were decreased.The percentage of hyphal growth inhibition by PEO at 0.5,1 and 2 MIC increased from 81.75%to 93.07%,and the ergosterol content decreased significantly with increase in essential oil concentration.Scanning electron microscopy showed that the PEO-treated myceliaof Aspergillus glaucus exhibited pits and pores.As the concentration of essential oil increased,the mycelia appeared to shrunken and distorted.PEO treatment decreased mitochondrial ATPase activity.PI staining indicated that the cell membrane integrity was reduced and the amount of stained spores increased with increase in PEO concentration.FTIR demonstrated significant changes in organic ligand groups in the mycelia in response to PEO treatment,suggesting damage to phospholipids,proteins and lipids.