巨大芽孢杆菌L2发酵产物对魔芋软腐病菌的抑菌机制

目的：探究巨大芽孢杆菌（Bacillus megaterium）L2发酵产物对贮藏期魔芋软腐病菌——胡萝卜软腐欧文氏菌（Erwinia carotovora subsp. carotovora）EC-1的抑菌机制。方法：以巨大芽孢杆菌菌粉为原料提取发酵产物，用常压硅胶柱层析分离得到发酵产物流分LE4-1～LE4-7，经抑菌实验筛选得到对胡萝卜软腐欧文氏菌EC-1有良好抑菌作用的流分，再使用气相色谱-质谱（gas chromatography-mass spectrometry，GC-MS）法对其进行成分分析；并通过测定其半数抑制质量浓度（half maximal inhibitory concentration，IC50）、菌液电导率、核酸蛋白泄漏、可溶性总糖质量浓度、菌体总蛋白、菌体磷代谢及胞内活性氧水平对其抑菌机制进行研究。结果：巨大芽孢杆菌L2流分LE4-3对胡萝卜软腐欧文氏菌EC-1有良好抑菌作用，经GC-MS检测其主要成分为苯乙酸乙酯（32.190%（相对含量，后同））、亚油酸乙酯（15.819%）、苯乙酸甲酯（13.793%）等；LE4-3对胡萝卜软腐欧文氏菌EC-1的IC50为（1.06±0.01）mg/mL，并初步推测其作用机制是通过影响细胞膜完整性、损伤细胞结构、抑制细胞蛋白质合成及能量代谢等对胡萝卜软腐欧文氏菌EC-1发挥抑菌作用，因此巨大芽孢杆菌L2流分LE4-3在魔芋抗软腐病贮藏中具有良好的应用前景。

Antibacterial Mechanism of Fermentation Product from Bacillus megaterium L2 against Erwinia carotovora subsp. carotovora

Objective: To explore the inhibitory mechanism of the fermentation products of Bacillus megaterium L2 against Erwinia carotovora subsp. carotovora EC-1 as a major soft rot pathogen of Amorphophallus konjac K. Koch during storage. Methods: The fermentation products were extracted from freeze-dried Bacillus megaterium culture and separated by silica gel column chromatography under atmospheric pressure into 7 fractions (LE4-1-LE4-7). LE4-3, which exhibited potent antibacterial activity against strain EC-1, was analyzed for chemical composition by gas chromatography-mass spectrometry (GC-MS), and its antibacterial mechanism was studied by measuring the half maximal inhibitory concentration (IC50), the conductivity of cell suspension, nucleic acid and protein leakage, soluble total sugar concentration, total cell protein concentration, phosphorus metabolism and intracellular reactive oxygen species (ROS) level. Results: The major compounds of LE4-3 included ethyl phenylacetate (32.190%), ethyl linoleate (15.819%), and methyl phenylacetate (13.793%). Its IC50 value against strain EC-1 was (1.06 ± 0.01) mg/mL, and the antimicrobial mechanism may be achieved by damaging bacterial cell structure, affecting the integrity of the cell membrane, and inhibiting protein biosynthesis and energy metabolism. Therefore, fraction LE4-3 has promising application prospects for soft rot resistance in Amorphophallus konjac K. Koch during storage.