Inhibitory Effect And Mechanism Of Perilla Frutescens Essential Oil On Aspergillus Flavus

Plant essential oils are used and favored by researchers because of their safety,high efficiency,broad-spectrum sterilization,low toxicity,or non-toxicity and other advantages.Perilla Frutescens Essential Oil(PEO),as the main extract of perilla leaves,is often used in the chemical,food,and medical industries.It has anti-oxidant,anti-inflammatory,and anti-allergic effects.PEO has good broad-spectrum antibacterial activity and can effectively inhibit the growth of a variety of food-borne pathogens.However,the antibacterial mechanism of PEO inhibits food-borne pathogens has not been deeply studied.In this paper,the inhibitory effect and action mode of PEO on Aspergillus flavus(A.flavus)were clarified by investigating the effect of PEO on the phenotypic,transcriptomics and proteomics of A.flavus.Based on the research on the inhibitory mechanism of PEO on A.flavus,the antifungal effect of PEO fumigation treatment on the quality of high-moisture rice was evaluated.The main conclusions were as follows:1.The antibacterial activity of PEO on A.flavus was evaluated by the minimum inhibitory concentration(MIC),spore germination and mycelial growth.The results showed that MIC of PEO against A.flavus was 0.4?L/m L.The spore germination rate and the dry weight of hyphae of A.flavus were negatively correlated with volume concentration of PEO.The surface of A.flavus hyphae treated with PEO had wrinkles,distortions,and depressions.The intracellular material of A.flavus treated with PEO leaked,the cell membrane permeability increased,the protein and ergosterol concentration decreased,and the activity of Ca²⁺Mg²⁺-ATPase and Na⁺K⁺-ATPase decreased.In other words,PEO could cause damage to the cell membrane of A.flavus,causing spore germination and mycelial growth to be inhibited.2.The active oxygen content,defense enzyme activity,ATP concentration and mitochondrial enzyme activity of A.flavus treated with PEO were studied.The results showed that PEO could induce a large amount of active oxygen accumulation in the cells of A.flavus and aggravate the damage of cell membranes.The decrease in the activities of peroxidase,catalase and superoxide dismutase in the cells further aggravated the accumulation of intracellular reactive oxygen species.In addition,PEO could reduce the ATP content of A.flavus by inhibiting mitochondrial ATPase activity,which affected the normal energy supply of A.flavus.3.Transcriptomics analysis of A.flavus treated with PEO was performed with RNA-seq.Results revealed that there were 5914 differentially expressed genes,of which 3025 were up-regulated and 2889 were down regulated.The results showed that DEGs related to spore germination were significantly down-regulated.DEGs related to cell membrane protein(39/70),chitin synthase(15/17)and ergosterol synthesis(11/25)in A.flavus were also down-regulated.The above results indicated that PEO inhibited the synthesis of A.flavus cell membrane components,leading to destroy the integrity of cell membranes.DEGs related to oxidative stress(8/16)were down-regulated,indicating that the ability of A.flavus to eliminate reactive oxygen species was weakened,and it was confirmed that A.flavus cell membranes were damaged after PEO treatment.4.Proteomics analysis of PEO treated A.flavus was performed with TMT.Results revealed that there were 793 differentially expressed proteins,of which 545 were up-regulated and 248 were down regulated.PEO could induce the accumulation of Reactive Oxygen Species(ROS)in A.flavus,aggravate the damage of oxidative stress to A.flavus by destroying the antioxidant enzyme system,and interfere with the oxidative stress regulation system of A.flavus.At the same,the glycolytic pathway was inhibited.A.flavus activated amino acid metabolism,pyruvate metabolism,fatty acid degradation,glyoxylic acid metabolism and tricarboxylic acid cycle to maintain stability and maintain normal energy metabolism.5.The high-moisture rice inoculated with A.flavus was fumigated and treated with PEO and stored under the storage conditions of 30?and 85%temperature and humidity,respectively.The antibacterial application effect of PEO in high-moisture rice was evaluated by measuring the total number of A.flavus.The results showed that the fumigation effect of PEO at a concentration of 5?L/g and above was the best.PEO could significantly inhibit the growth of A.flavus,and effectively maintain the soluble protein content and catalase activity of rice.It could also delay the rising trend of polyphenol oxidase activity in high-moisture rice,reduce the browning degree of rice,and effectively maintain the apparent color of rice.At the same time,PEO fumigation treatment can significantly inhibit the increase in the fatty acid value of rice,effectively reduce the content of malondialdehyde,and maintain the structure and function of the rice cell membrane,effectively delaying the deterioration of high-moisture rice quality.