Study On Mechanism Of Inhibiting The Growth Of Aspergillus Flavus By Electron Beam

The carcinogenicity of Aspergillus flavus,as a hidden danger in the postharvest storage of agricultural products,seriously endangers the safety of human life and property.In this paper,the advantages of short processing time,high sterilization efficiency,no pollution and no addition of electron beam irradiation are used to prevent and control Aspergillus flavus pollution.The main results are as follows:（1）Effect of electron beam irradiation on the growth of Aspergillus flavus.The effects of electron beam irradiation on the growth of Aspergillus flavus were determined by comparing and monitoring the effects of different doses on Aspergillus flavus spore germination,D₁₀value,Aspergillus flavus growth inhibition rate,hyphae dry weight,and Aflatoxin B₁content before and after irradiation.Finally,peanut infestation was used to verify it.The results showed that Aspergillus flavus spore germination decreased with the increase of irradiation dose,D₁₀value was 0.92 k Gy,Aspergillus flavus hyphae growth was inhibited,hyphae dry weight weight decreased,aflatoxin B₁content decreased significantly,and peanut infection decreased with the increase of irradiation dose,indicating that the normal growth of cells was inhibited.（2）Effect of electron beam irradiation on the structure and physiological indexes of Aspergillus flavus hyphae.The morphology of Aspergillus flavus,mycelium growth and spore morphology were observed under electron microscope and optical microscope to determine the effect of irradiation on Aspergillus flavus mycelium.The effects of irradiation on the cell membrane and cell wall of Aspergillus flavus were investigated by the contents of chitinase,malondialdehyde and protein.The damage of antioxidant system was determined by hydrogen peroxidecontent,catalaseenzyme activity,superoxide dismutase activity,anti-superoxide anion activity,and 1,1-diphenyl-2-trinitrophenylhydrazine inhibition rate.The results showed that after irradiation,the morphology of bacteria was damaged,the growth of mycelium was inhibited,the chitinase activity and malondialdehyde content were increased,and the contents of chitin and protein were decreased.The activity of catalase,the activity of superoxide dismutase,the activity of anti-superoxide anion and the inhibitory rate of 1,1-diphenyl-2-trinitrophenylhydrazine were decreased,and the content of hydrogen peroxide was increased,indicating that the permeability of Aspergillus flavus cell membrane increased,the integrity of cell wall decreased,the function of antioxidant system was disabled,and the cells were damaged by oxidation.（3）Effects of electron beam irradiation on energy metabolism and related enzymes of Aspergillus flavus.The mitochondrial structure was analyzed by transmission electron microscopy.The effects of electron beam irradiation on energy metabolism of Aspergillus flavus were determined by measuring alkaline phosphatase,ultrafine Na⁺K⁺-ATPase,Ca²⁺Mg²⁺-ATPase and total ATPase activity.Pyruvate content,pyruvate dehydrogenase,cytoplasmic isocitrate dehydrogenase,α-ketoglutarate dehydrogenase,succinate dehydrogenase,malate dehydrogenase,which are key enzymes in the tricarboxylic acid cycle,were determined to determine the effects of electron beam irradiation on tricarboxylic acid pathways associated with energy metabolism.The results showed that the cell structure and spores were damaged under transmission electron microscope and mitochondria were swollen under high dose irradiation.Alkaline phosphatase enzyme activity,ultrafine Na⁺K⁺-ATPase,Ca²⁺Mg²⁺-ATPase,total ATPase activity decreased.The activity of pyruvate dehydrogenase,isocitrate dehydrogenase,α-ketoglutarate dehydrogenase,succinate dehydrogenase and malate dehydrogenase decreased,but the increase of pyruvate content,indicating that electron beam irradiation affected the normal operation of mitochondria and inhibited the growth of Aspergillus flavus.（4）The effect of electron beam irradiation on Aspergillus flavus was analyzed based on transcriptomics.According to RNA-Seq transcriptomic sequencing analysis,the number of significantly differentially expressed genes in Aspergillus flavus under electron beam irradiation was 3849,with 1891 genes down-regulated and 1958 genes up-regulated.In the analysis of electron beam irradiation on Aspergillus flavus cell wall,cell membrane,antioxidant system,tricarboxylic acid cycle,aflatoxin B₁synthesis,it was found that most of the related genes were downregulated,affecting the normal operation of the pathway.The main pathways involved are pyruvate metabolism,endoplasmic reticulum protein processing,MAPK signaling pathway,gluconeogenesis/glycolysis,co-factor synthesis,etc.Electron beam irradiation as a means of postharvest control has a wide application prospect in the future agricultural industry.