Study On Isolating And Selecting Of Antagonistic Microbes And Controlling The Postharvest Decay Of Citrus Fruit

Thirty-six bacteria strains and forty-four fungi strains were isolated from different sources,and six other food microbes strains in vitro tests showed antifungal activity against Penicillium sp.which was isolated from citrus fruit.The character of B-7,B.natto,Y-15,Y-16,the optimization of the culture medium and culture conditions of four strains antagonistic microbes,the efficacy of four antagonistic microbes strains for the controlling of postharvest decay and resistance of citrus fruit were studied.The results are as followed.(1)Thirty-six bacteria strains and forty-four fungi strains isolated from different commercial retailers as milk,wine,honey,surface of citrus fruit,and six other food microbes strains in vitro tests showed antifungal activity against Penicillium sp..As a result,eight antagonistic microbes strains were selected.(2)Study on the character of eight antagonistic microbes strains,it showed that cells played a important role in the antifungal activity against Penicillium sp..The use of some concentration of Calcium chloride(CaCl₂)in the soak suspension extremely improved the antifungal activity.(3)Optimized the culture medium and culture conditions for the four antagonistic microbes strains,which increased the concentrations greatly.(4)Study on the postharvest decay proportion and resistance activity of citrus fruit by inoculated antagonistic microbes.The treatments by inoculated Y-15 and Y-16 showed stronger inhibition against citrus fruit postharvest decay than others, from 100% decreased to 58% and 47%.The capacity of scavenging DPPH were higher than comparison treatment,from 88.7% increased to 99.0% and 100.0%, the activity of Peroxidase(POD)increased 1.97～3.83 U·g^-1.min^-1,the activity of Superoxide dismutase(SOD)increased 10.07～12.06 U·mL^-1,and the concentration of Malondialdehyde(MDA)decreased 2.26～2.48umol·L^-1.It is accounted that the two antagonistic yeasts can enhance the resistance activity of citrus fruit.