通过测定最低抑菌浓度(minimum inhibitory concentration,MIC)和最小杀菌浓度(minimum fungicidal concentration,MFC)、孢子萌发抑制率、菌丝生长抑制率确定柠檬皮中柠檬苦素对青霉的抑菌活性;结合总糖含量和蛋白质含量、碱性磷酸酶(alkaline phosphatase, AKP)活力等的变化,以及扫描电镜观察对抑菌机理进行研究。结果表明:柠檬皮中柠檬苦素对青霉有很强的抑菌活性,对青霉的MIC和MFC分别为625和2 500 μg/mL,对青霉菌丝生长和孢子萌发抑制的EC50值分别为85.618和246.755 μg/mL。柠檬苦素能在短时间内对青霉的细胞壁和细胞膜造成破坏,使胞内物质大量渗出;且柠檬苦素浓度越高,胞内物质渗出越多。扫描电镜观察也发现经柠檬苦素处理的青霉外附着渗出物;产孢数量变少,孢子变形;小梗破损、凹裂;菌丝变细,变形。
The antifungal activities of limonoids against Penicillium were investigated by determining their minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and inhibition rates of spore germination and mycelium growth. By determining the changes of total sugar content, protein content, and alkaline phosphatase (AKP) activity, together with scanning electron microscope (SEM) observation, the antifungal mechanisms of limonoids were investigated. The results showed that limonoids had strong inhibitory activities against Penicillium. The MIC and MFC of limonoids were 625 μg/mL and 2 500 μg/mL, respectively. Their EC50 values of inhibiting mycelium growth and spore germination of Penicillium were 85.618 μg/mL and 246.755 μg/mL, respectively. Limonoids could destroy the cell wall and cell membrane of Penicillium in a short time, which caused a large amount of exudation of intracellular substances. Additionally, the higher concentration of limonoids, the more exudates of Penicillium. Moreover, SEM observation also indicated that Penicillium treated with limonoids had adherent exudates. Furthermore, the number of spores of the treated Penicillium decreased, and the spores also deformed. Besides, the pedicels damaged and cracked, and the mycelia became finer and deformed.
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