Antibacterial Mechanism Of Cold Plasma On Salmonella Typhimurium Biofilm And Its Application In Poultry Eggs

Poultry eggs are the best source of high-quality protein,but poultry eggs are easily contaminated by bacteria during production,processing and cooking.Among them,Salmonella Typhimurium is one of the most important pathogenic bacteria that causes the contamination of poultry eggs and related products.Salmonella Typhimurium is very easy to form a biofilm on the surface of poultry eggshells.The extracellular polymer substance of the biofilm can protect Salmonella Typhimurium in biofilm,which makes it difficult for traditional sterilization methods to remove the biofilm.The purpose of this project is to study the removal effect and antibacterial mechanism of cold plasma on Salmonella Typhimurium biofilm,and to study the removal effect of cold plasma on Salmonella Typhimurium of poultry eggshell.The main research results of this paper are as follows:(1)Effect of cold plasma on the removal of Salmonella Typhimurium biofilmThe antibacterial effect of cold plasma was positively correlated with applied power and processing time.After 400 W for 3 min,the sterilization rate of cold plasma on the surface of stainless steel sheet,nylon sheet and glass sheet reached 99%,and the total amount of biofilm on the three surfaces reduced by 25%-34.7%;After 600 W for 2 min,the sterilization rate of the three surfaces reached 99.9%,and the total biofilm reduced by 68.6%-74%,indicating that cold plasma could effectively remove Salmonella Typhimurium biofilm on different surfaces.After cold plasma treatment,the percentage of Salmonella Typhimurium with metabolic activity decreased,and the diameter of the swimming ring of Salmonella Typhimurium decreased,indicating that cold plasma can weaken the swimming ability of Salmonella Typhimurium and could lead to the loss of bacterial metabolism.SEM and CLSM showed that cold plasma treatment would destroy the structure of Salmonella Typhimurium biofilm and adversely affect Salmonella Typhimurium attached to the surface.(2)Antibacterial mechanism of cold plasma on Salmonella Typhimurium biofilmCold plasma could generate hydroxyl radicals by reacting with the water environment around the biofilm to act on the biofilm and the bacteria within it.Cold plasma could stimulate bacteria to produce ROS and cause oxidative stress in Salmonella Typhimurium.The results of the enzymatic hydrolysis test showed that in the extracellular polymer substance,extracellular protein was the most,followed by the extracellular polysaccharide,and eDNA was the least.After 600 W for 2 min,the content of extracellular polysaccharide,extracellular protein and eDNA decreased by 73.1%,82% and 67.5%,respectively,indicating that cold plasma could destroy structure of the extracellular polymer substance.After cold plasma treatment,the relative expression levels of csgD,adrA,csgB,and bcsA were all down-regulated,indicating that cold plasma treatment was not conducive to the formation of extracellular polymer substa nce.The relative expression levels of genes related to oxidative stress(sodA,katE and ahpC)in Salmonella Typhimurium were all up-regulated,indicating that cold plasma could cause intracellular oxidative stress in Salmonella Typhimurium.(3)Cold plasma application for the removal of Salmonella Typhimurium biofilm on the surface of poultry eggshellsThe effect of cold plasma on the color of the eggshell and duck eggshell surface was very weak and could be ignored.After 600 W for 2 min,the sterilization rate of Salmonella Typhimurium biofilm on eggshell and duck eggshell stored at 4 ?C for 3 d reached 99.99% and 99.97%,respectively.After storage at 25 ?C for 3 days,the sterilization rate reached 99.98% and 99.97%,indicating that cold plasma can effectively remove Salmonella Typhimurium biofilm on the egg and duck eggshells.The evaluation results of the weight and internal quality the poultry eggs during storage showed that cold plasma treatment had no adverse effect on poultry eggs.