Study On Screening Of Biological Antagonistic Bacteria And Its Formulations During The Preservation Of Fruits And Vegetables

Biological control of postharvest diseases in fruits and vegetables was considered to be the most promising alternative to chemical fungicide.Using the red globe grapes as the materials,aiming to isolate and screen the potential antagonistic yeast from different periods and parts of the red globe grapes,We Identified the inhibitory action by in vitro and vivo and screenned out the best one named YT-2 from the 6 strains.After that,the biological characteristics and antagonism effect of YT-2 were studied.And its possible mechanism of antagonism was discussed.The liquid and powder antistaling agents were prepared.Some conclusions were drawn as following:1.Isolation and identification of dominant pathogenic bacteria of red globe grapeIn the four periods of postharvest of the red globe grape,four dominant pathogens were separated from the three parts of the fruit,the wound and the fruit stem.Those were identified as the Botrytis cinerea,Alternaria spp.,Aspergillus niger and Penicillium spp...2.Isolation and screening of antagonistic yeastIn the four periods of postharvest of the red globe grape,26 strains of antagonistic yeasts were separated from the three parts of the fruit,the wound and the fruit stem.The best one named YT-2 was Screenned out by in vitro and vivo,which had significant inhibitory effects on Botrytis cinerea,Alternaria spp.,Aspergillus niger and Penicillium spp.3.Identification of antagonistic yeast YT-2YT-2 was identified as Pichia kudriavzevii by the identification of colony morphology,culture characteristics,physiological-biochemical characteristics and 26S rDNA sequencing,4.Study on the biological characteristics of antagonistic yeast YT-2Both in the mash medium and NYDB medium,the trends of growth curve of YT-2 were basically consistent.It entered the logarithmic growth period in 4 hours,the stable period after 12 hours.Optimal growth carbon source is glucose;the optimal growth nitrogen source is peptone,followed by yeast extract.The optimal pH is 6?7.The optimal temperature 28 ?.The inorganic salts that affect its growth most are CaCl2 and NaCl.5.Study on antagonistic mechanism of antagonistic yeast YT-2The optimal antagonistic effect concentration was 1.0×108CFU/mL.YT-2 suspension was inoculated ahead of 48h,24h,2h and later 2h,24h,48h than pathogenic spores suspension,which proved that all of them could inhibit the growth of pathogenic bacteria in varying leves.The earlier of the YT-2 be inoculated,the more obvious effect was.Both the cultivation of clear liquid and heat kill fluid had no inhibition effect on pathogens,which showed that the antagonistic mechanism of YT-2 was not secret antagonistic substances.The antagonistic mechanism of the YT-2 may involve the nutrition and spatial competition,since the inhibition effect of the cell suspending liquid was better than the original fluid.6.Preliminary study on bio-control agent and application of antagonistic yeast YT-2Both liquid bio-control agent and dry powder bio-control agent of YT-2,the cell survival rate were better than control group under the condition of 4?.The cell survival rate maintained more than 50%during the preservation time,respectively for 60 days,90 days and 20days.Applied the agents to preservation of globe grapes,the decaying rate of the liquid formulation treatment group was 18.6%,the the dry powder was 28%,whereas the control group was 100%after 6 days during 25 ?.