Study On Inhibitory Effects And Application Of Myriocin Against Fusarium Graminearum And Deoxynivalenol Production

Fusarium graminearum is a filamentous fungus that infects wheat,barley,corn and other crops,which also produces mycotoxins such as deoxynivalenol(DON,also known as vomitoxin)that reduced food nutrition and seriously endangered public health.Contamination of F.graminearum and its DON has become a key problem of food safety.Therefore,inhibitory activity and its mechanism of myriocin(ISP-1),an active substance derived from natural products,against F.graminearum and DON production were studied.Besides,nanofibrous films loaded with myriocin were prepared,and its application in food antifungal packaging was explored.The main research contents and results were as follows:The antifungal activity and mechanism of myriocin against F.graminearum.The minimum inhibitory concentration(MIC)of myriocin determined by the microdilution method against F.graminearum was 64?g·m L^-1 and kept stable in the range of p H 3?8.Myriocin showed inhibitory effect against F.graminearum by inhibiting mycelial growth and spore germination and showed concentration dependence between 16?128?g·m L^-1.Scanning electron microscopy and laser confocal microscopy observations showed that when treated with myriocin at MIC level,mycelia of F.graminearum became abnormal with irregular shrinkage,depression and even spores on the surface;spore viability of F.graminearum reduced and spores even died.As the concentration of myriocin increased,relative conductivity of the extracellular cells,leakage of protein and nucleic acid,and the degree of membrane lipid peroxidation increased.The results of molecular docking showed that myriocin can be combined with serine palmitoyl transferase(SPT)through hydrogen bonding and hydrophobic interaction to reduce its enzymatic activity,thereby reducing the synthesis of sphingolipids of membrane.These results indicated that myriocin affects the structure and function of the cell membrane by changing the permeability and integrity of membrane,thereby inhibiting the growth of F.graminearum.The effect of myriocin on DON biosynthesis of F.graminearum and its mechanism of action.Treated with myriocin at sub-inhibitory concentrations of 16?g·m L^-1 and 32?g·m L^-1,the DON production was inhibited by 76.40%and 84.33%,respectively.Through transcriptomics analysis of differentially expressed genes(DEGs)and changes of key metabolic pathways,it was found that the expression of the TRI gene cluster that regulates the DON synthesis pathway was down-regulated.RT-PCR results showed that myriocin treatments of 16?g·m L^-1 and 32?g·m L^-1 reduced the expression of the key gene TRI5 by 1.13 and 3.10 times,and the TRI6 decreased by 1.01 and 1.28 times.Respiratory metabolism analysis showed that myriocin at 16?g·m L^-1 and 32?g·m L^-1 reduced the production of acetone acid by 42.63%and60.14%.These results indicated that myriocin can inhibit DON biosynthesis by down-regulating the expression level of TRI5 gene and affecting acetone production of the glycolytic pathway in F.graminearum.The application of myriocin in wheat preservation and antifungal food packaging.The results showed that myriocin(80?g·g^-1)can reduce DON production per unit wheat grain weight and delay the deterioration of wheat quality.Biopolymer 3-hydroxybutyric acid-co-3-hydroxyvaleric acid copolymer(PHBV)mixed with different proportions of myriocin were used to prepare PHBV/ISP-1 nanofibrous films by electrospinning.Taking the antifungal activity and cytotoxicity of the nanofiber film as comprehensive indicators,the PHBV/3%ISP-1 nanofiber films was selected for further structural characterization and performance determination.The results showed that PHBV/3%ISP-1 nanofibrous film had a water contact angle of 113.8±5.40^o and showed hydrophobicity.SEM observation showed that the fibers are randomly connected,the surface was smooth without bead,and the average diameter was740±132 nm.Mechanical performance test showed that breaking strength of the nanofiber films was 5.49±0.39 MPa,showing good mechanical properties.Strawberry preservation experiment showed that PHBV/3%ISP-1 nanofiber films can effectively maintain strawberry quality,hardness and organic acid content,and delay strawberry spoilage,indicating its potential application of antifungal food packaging.