Strains and Culture Conditions

P. polymyxa Y-1 was isolated and identified in our previous study (Yang et al., 2018) and cultured at 28°C in potato dextrose broth (PDB) medium and stored at –80°C in Luria-Bertani with 30% (v/v) glycerol. The pathogenic bacterial strain was cultured in 500 ml of PDB at 28°C until bacteria PDB medium has grown into the logarithmic phase. The supernatant was inoculated into 30 L of PDB medium and grown for 14 days until the OD₅₉₅ reached more than 1.1. The fermentation broth was centrifuged at 8,000 rpm for 30 min at room temperature, and then collected the supernatant for testing the antibacterial activity and isolating the antibacterial metabolites.