介质阻挡放电用于细菌灭活的机理研究

Bacteria Inactivation Mechanisms by Dielectric Barrier Discharge

为研究低温等离子体灭菌的机理,利用介质阻挡放电(DBD)低温等离子体来进行了细菌灭活实验。试验选取了两种典型细菌:革兰氏阳性的金黄色葡萄球菌和革兰氏阴性的大肠杆菌。将载有细菌悬浊液的盖玻片放置在下平板电极的中央,通过调整电源电压、气隙间距和处理时间来考察电场和等离子体对两种不同细菌的作用;利用电子透射电镜(TEM)观察了等离子体处理后的细菌细胞,以确定细胞的完整性;测量了等离子体处理后的两种细菌悬浊液中蛋白质,核酸和K+的浓度。实验结果表明:在<10s时间内金黄色葡萄球菌死亡率接近100%;<7s内,大肠杆菌死亡率接近100%,取得了良好的灭菌效果。分析认为电场作用不是细菌灭活的主要因素,而等离子体中的氧自由基可以破坏细胞壁和细胞膜,以及细胞质中的蛋白质和核酸,从而起到杀菌的效果。

The low-temperature plasma generated by dielectric harrier discharge （DBD） was used to sterilize the bacteria. Two kinds of typical bacteria, gram-positive （Staphylococcus aureus） and gram-negative （Escherichia coli）, were employed to explore the inactivation mechanisms. Cells of bacteria held by cover-glass were placed on the parallel-plate electrode in atmospheric air. Based on adjusting the applied voltage, gap distance and treatment time, the effects of electric field and plasma on the bacteria inactivation were investigated. The transmission electron micro- scope （TEM） was used to observe the plasma treated cells to detect their integrality. The concentration of protein, nucleic acid and K^＋ inside cells was also measured. Experimental results demonstrate that, nearly 100% of S. aureus is killed in less than 10 s treatment, and nearly 100% of E. coli is killed in less than 7 s. It can be concluded that, the reactive oxygen species in plasma but not electric field, play a dominant role in the inactivation process. The reactive oxygen species can oxidize the cell membrane, and then damage the protein and nucleic acid inside the cells, and thus the bacteria are killed.