Study On The Antibacterial Activity And Antibacterial Mechanism Of Three Plant Essential Oil Inclusion Compounds On Postharvest Rambutan Fruit Pathogen Aspergillus Aculeatus

Rambutan（Nephelium lappaceum L.）has good flavor and high nutritional value.It is a popular tropical fruit.Rambutan is listed by the UN Food and Agriculture Organization as one of the"Four Major Fruits"with priority for promotion.Hainan is the only region suitable for large-scale cultivation of rambutan in my country,and currently has the largest rambutan production base in China.Rambutan has a unique flavor and exquisite appearance,which is very popular among consumers.However,the rambutan fruit is extremely intolerant to storage and transportation.On the one hand,the densely distributed soft thorns and stomata on the surface of the fruit make the fruit prone to dehydration and browning,so it is necessary to maintain a high humidity environment during storage,transportation and sales;however,it is more prone to rot under high humidity.On the other hand,the soft spines of rambutan fruit are easily damaged and accelerate the browning of the peel.At the same time,the wound will become a channel for pathogen infection.The laboratory isolated and identified Aspergillus aculeatus（Aspergillus aculeatus）as the main pathogen of rambutan fruit brown spot disease in Hainan.The thesis embeds 3 kinds of plant essential oils（cinnamon essential oil,mustard essential oil,clove essential oil）withβ-cyclodextrin,and investigates the antibacterial activity and inhibitory mechanism of plant essential oil inclusion compounds against Aspergillus aculeatus.The specific research results are as follows:（1）Taking Aspergillus aculeatus as the research object,the growth rate method was used to determine the antibacterial activity of three plant essential oil inclusion compounds.The results showed that the EC₅₀ of the clove essential oil inclusion compound was 2.24g/L;the EC₅₀ of the cinnamon essential oil inclusion compound was 4.78g/L;the EC₅₀ of the mustard essential oil inclusion compound was 1.00g/L,and the mustard essential oil inclusion compound had an EC₅₀ of 1.00g/L.The compound has the best antibacterial activity against Aspergillus aculeatus.Scanning electron microscopy was used to observe the morphological changes before and after the antibacterial treatment,and it was found that the hyphae had shrunk and wrinkled,and the conidia apical cyst and morphology changed significantly;Electron microscope observation revealed that the cell morphology has shrunk,the boundary of the cell wall membrane is blurred,and serious internal dissolution has occurred.（2）Treatment of Aspergillus aculeatus with the mustard essential oil inclusion compound at a concentration of 1.00 g/L for 60 h（treatment group）,and the control group without the mustard essential oil inclusion compound treatment.Transcriptome sequencing analysis of the control group and the treatment group found that 1057 differentially expressed genes were obtained,of which 528 genes were up-regulated and 529 genes were down-regulated;through GO annotation of the differential genes,it was found that the main focus was on the respiratory electron transport chain and aerobic respiration.,Sequence-specific DNA binding,nucleic acid binding transcription factor activity,RNA polymerase II transcription factor activity,extracellular region,mitochondrial membrane,organelle inner membrane and other pathways;through KEGG enrichment analysis,it is found that differentially expressed genes mainly focus on energy metabolism and carbon water Pathways such as compound metabolism,amino acid metabolism,folding,classification and degradation,cell growth and death,transportation and catabolism,and nucleotide metabolism.（3）Treatment of Aspergillus aculeatus with the mustard essential oil inclusion compound at a concentration of 1.00 g/L for 60 h（treatment group）,and the control group without the mustard essential oil inclusion compound treatment.Theβ-1,3-glucanase and chitinase activities of the treatment group increased compared with the control.It is inferred that the main structural components of the cell wall（β-1,3-glucan and chitin）have developed more Compared with the control group,the content of malondialdehyde（MDA）and catalase activity in the treatment group were higher.It is speculated that more intracellular reactive oxygen species in the treatment group caused cell membrane damage,thus making Membrane lipid peroxidation product（MDA）content increased;compared with the control,the activity of succinate dehydrogenase and Ca²⁺Mg²⁺-ATPase decreased in the treatment group,indicating that the cellular respiration in mitochondria was weakened;compared with the control,NADH oxidase in the treatment group And coenzyme II-NADP（H）content,NADPH-cytochrome c reductase activity are relatively higher,indicating that cells proliferate in large numbers in order to resist.Generally speaking,due to the weakening of cell energy supply and the inability of electrons to pass normally,cell activities cannot be carried out normally.