Sterilizing Effect Of DBD And APPJ Cold Plasma At Atmospheric Pressure On Yeast

The dielectric barrier discharge (DBD) plasma and atmospheric pressure plasma jet (APPJ) sterilization is presented in this paper. They have been thought as a potential technology due to many advantages, such as a high efficiency, a quick speed, a nonthermal, and simple operation as well as non-toxicity process, which shows a great promise. In this paper, the mechanism of yeast inactivation in low temperature atmospheric pressure helium, nitrogen and air plasmas generated by DBD and helium plasma by APPJ is analyzed and compared.The results show that the three gas plasmas generated by DBD all have a high germicidal efficiency. The reduction of seven orders of magnitude of yeast suspension treated by helium DBD is presented, and the reduction of five orders of magnitude by nitrogen plasma and six orders of magnitude by air plasma is presented. The morphology of the yeast is observed by scanning electron microscopy, which reveals the yeast treated in helium DBD plasma is ruptured completely but there are only some flaws on the cell walls in nitrogen and air DBD plasma treatment samples, even the flaws on the cell walls treated by air DBD plasma are more significant than that by nitrogen DBD treatment. Simultaneously, pH values of the samples after 5 min nitrogen and air DBD plasma treatments have no remarkable change, while that the sample treated with helium DBD plasma descends with the treatment time extended, the value is beyond the optimum one for the yeast living environment. It is the combined action of electrostatic tension, reactive species that kill the yeast. While the different pH values are maybe the causes for a treatment effect and the cell rapture degree when different gas discharge plasma treatments are applied.The reduction of eight orders of magnitude by helium APPJ is presented. The morphology of the yeast is also observed by scanning electron microscopy, which reveals the yeast treated by APPJ plasma is also ruptured completely. It can be seen that the efficiency of APPJ plasma sterilization is higher than DBD plasma. Simultaneity the pH value of the samples after 5 min APPJ plasma treatment also descends quickly with the treatment time extended. While the sample is far away from the discharge room, there are long odds on the action of electrostatic tension. It maybe the combined action of more reactive species generated by helium APPJ and pH value that cause the higher efficiency.