Breeding of antagonistic bacteria against Penicillium expansum and study on its inhibition mechanism

To breed the antagonistic strain which can inhibit Penicillium expansum effectively,and discuss its antibacterial mechanism preliminarily.An antagonistic strain BA-16,which could inhibit Penicillium expansum,was isolated from apple surface and identified based on phenotypic,physiological,biochemical and phylogenetic( 16 S r DNA) studies.In order to enhance its antagonistic capability,the mutation of BA-16 was carried out by using low energy N+implantation.Double enzyme reaction system was used to detect the phospholipase A( PLA) activity of Penicillium expansum under the action of wild- type antagonistic strain and its mutant. The strain BA- 16 was identified as Bacillus amyloliquefaciens.After the low energy N + implantation,the mutant BA-16-8,which showed the strongest antagonist capability and stable hereditary stability was selected out. In phospholipase activity detection,mutant showed stronger inhibition against PLA activity secreted by Penicillium expansum than its wild-type strain. Moreover,as the concentration of fermentation broth increased,the inhibition effect enhanced,which indicated that it was possibly the inhibitory mechanism of antagonistic strain against Penicillium expansum. The mutant BA-16-8 will be a potential biological control agent against apple blue mold decay.