Isolation and characterization of a new strain of Bacillus amyloliquefaciens and its effect on strawberry preservation

Bacillus amyloliquefaciens has been widely used in agriculture these years for its high efficiency in biological control of postharvest fruits. Aiming to look for efficient biopreservative of fruits and vegetables, a new strain PJ which isolated from Litopenaeus vannamei, was identified as B. amyloliquefaciens based on morphological, physiological, biochemical characteristics, and phylogenetic relationships. Subsequently, the antimicrobial peptide (termed PJAP) was isolated and purified. At last, the bioactivities and functional application of this peptide were evaluated through the determination of the antibacterial activity and the preservation effect on strawberries. Results indicated that the molecular mass of PJAP was approximately 3.3 kDa. PJAP had antagonistic effect on foodborne pathogens (minimal inhibitory concentrations, MIC values = 62.5–250 μg/mL), and electron microscopy and flow cytometry revealed that PJAP caused an increase of cell membrane permeability in Staphylococcus aureus. The rate of strawberry weight loss and titratable acid level during low temperature storage were delayed after strawberries were treated with PJAP. Consequently, this study indicated that B. amyloliquefaciens PJ and related bacteriostatic substance may have potential applications as the natural preservative for the storage of strawberry after harvest.