等离子体活化水-苯乳酸协同杀灭大肠杆菌O157:H7作用及机制研究

拟研究等离子体活化水（Plasma-activated water，PAW）与苯乳酸（Phenyllactic acid，PLA）协同处理对大肠杆菌O157:H7的杀灭效果及其作用机制。采用平板计数、扫描电镜、荧光染色等方法研究PAW与PLA协同处理对大肠杆菌O157:H7的杀灭作用及其对细胞形态、细胞膜完整性和胞内活性氧水平等的影响。结果表明，经终浓度为0.125～1.0 mg/mL的PLA处理8 min后，大肠杆菌O157:H7活细胞数未发生显著变化（P>0.05）。经PAW与PLA（终浓度为1.0 mg/mL）协同处理8 min后，大肠杆菌O157:H7降低了5.65 lg CFU/mL，显著高于PAW单独处理组（降低了1.06 lg CFU/mL） （P<0.05）。扫描电镜结果表明，PAW与PLA协同处理可造成细胞形态发生明显变化。与对照组细胞相比，经PAW-PLA（1.0 mg/mL）协同处理8 min后，胞外蛋白含量、细胞膜电位和胞内活性氧分别升高了25.6、0.75和9.53倍（P<0.05）。综上所述，PAW与PLA协同处理能够有效杀灭大肠杆菌O157:H7，这可能与其破坏细胞膜及诱导氧化损伤等有关。本研究为PAW与PLA协同处理在食品保鲜中的应用提供了理论依据。

Synergistic Inactivation Effects and Mechanisms of Plasma-Activated Water Combined with Phenyllactic Acid against Escherichia coli O157:H7

The present study aimed to elucidate the antibacterial effect and underlying mechanisms of plasma-activated water (PAW) combined with phenyllactic acid (PLA) against Escherichia coli O157:H7. The inactivation effects of PAW and PLA on E. coli O157:H7 and their effect on cell morphology, cell membrane integrity and intracellular reactive oxygen species (ROS) level were investigated by plate counting, scanning electron microscopy and fluorescence staining. The results showed that the population of E. coli O157:H7 did not change significantly after PLA treatment at 0.125～1.0 mg/mL for 8 min (P>0.05). E. coli O157:H7 decreased by 5.65 lg CFU/mL after PAW treatment combined with 1.0 mg/mL of PLA for 8 min, which was significantly higher than the 1.06 lg CFU/mL of PAW alone (P<0.05). As shown by the scanning electron microscope images, obvious changes in the morphology of E. coli O157: H7 cells were observed after PAW treatment combined with PLA. After the co-treatment of PAW and PLA (1.0 mg/mL) for 8 min, the extracellular protein content, cell membrane potential and intracellular ROS level of E. coli O157:H7 increased by 25.6-, 0.75- and 9.53-fold (P<0.05), respectively, as compared with the control cells. In summary, PAW combined with PLA could effectively inactivate E. coli O157:H7 cells, which might be associated with membrane disruption and oxidative damages. The results could provide a scientific basis for the application of PAW and PLA in food sterilization and preservation.