Screening Of Antagonistic Yeast And Its Application In Postharvest Preservation Of Grape

Objective: Mould pollution causes a large number of fruits and vegetables to rot and deteriorate after harvest every year,resulting in serious waste,which has attracted worldwide attention.Existing studies have shown that antagonistic yeast has great potential as a new biological antibacterial agent.However,due to the factors such as stability and shelf life,its commercial application has been facing many challenges.Therefore,this study will comprehensively evaluate the feasibility of antagonistic yeast as a biological antibacterial agent,based on the analysis of the mechanism of antagonistic yeast in the host and pathogen antagonistic system,combined with its application effect in grape post-harvest preservation,and lay a theoretical foundation for commercial application in the later stage.Methods: 57 yeast strains with good tolerance screened by the team were selected as samples,and yeast strains with antagonistic ability were obtained through in vitro and in vivo experiments.The mechanism of antagonistic enzyme activity,β-glucosidase activity,acetic acid production capacity and metabolites of yeast were explored.In order to explore the fresh-keeping effect of antagonistic yeast on purplesweet seedless grape,the physical and chemical indexes and the changes of fungal community on fruit surface during storage period were analyzed.Results:(1)A total of 7 yeast strains with different antagonistic abilities to Aspergillus Carbonarius,Botrytis Cinerea and Penicillium Expansum were selected.Six strains were identified as Hanseniaspora uvarum and one was Wickerhamomyces Anomalus.The strains showed different advantages in iron consumption,volatile organic compound production,hydrogen sulfide and acetic acid production,and biofilm formation.(2)The metabolites produced by antagonistic yeast,such as flavonoids,indole derivatives and heterocyclic compounds,have free radical scavenging and antioxidant activities,and can stimulate the organism to activate the defense system to exert antibacterial properties.(3)Antagonistic yeast LY3 and LY6 showed outstanding performance in the aspects of decay inhibition,hardness maintenance,weight loss control and other aspects in grape fresh-keeping experiments.By exploring the abundance of fungal community on the surface of the antagonistic yeast,it was found that the fungal community diversity on the fruit surface were effectively reduced,also could inhibit Acremonium,Alternaria,Cladosporium and other pathogenic fungi grow and multiply,and grape decay rate was delayed.Conclusion: Antagonistic yeasts can exert bacteriostatic effect on A.carbonarius,B.cinerea and P.expansum through A combination of various mechanisms,and can effectively control the growth and reproduction of fungal pathogenic microorganisms on the surface grapes,and delay the rate of decay and deterioration,which is a potential excellent biostat.