Antibacterial and antibiofilm activities and mechanisms of Toona sinensis extracts against Bacillus cereus and its application in milk

Bacillus cereus, a well-known foodborne pathogen, poses an increased risk because of its ability to form biofilms. In this study, we evaluated the antibacterial and antibiofilm activities of Toona sinensis extracts against B. cereus. All tested T. sinensis varieties demonstrated significant antibacterial activity against B. cereus, with inhibition zone diameters exceeding 11 mm (P < 0.05). Notably, the extracts from Sichuan Dazhu exhibited strong antibacterial effects, even against antibiotic-resistant B. cereus strains. 239 compounds were identified in Sichuan Dazhu extracts by LC-MS. The MIC and MBC of the extracts against strain ATCC 11778, BCL043 and BCL047 were 0.195 and 0.391 mg/mL, respectively. These findings were corroborated by growth curve experiments, live/dead cell staining, and scanning electron microscopy observations. Moreover, the extracts demonstrated remarkable antibiofilm activity against B. cereus, reducing biofilm biomass to less than 40 % (P < 0.05). Transcriptome analysis revealed its antibacterial and antibiofilm mechanisms. Additionally, the extracts exhibited potent antibacterial activity against B. cereus in skim milk. Collectively, these results underscore the significant antibacterial and antibiofilm potential of T. sinensis extracts, highlighting their potential applications in food safety. This report provides the first evidence of both antibacterial and antibiofilm activities in T. sinensis extract against B. cereus, while also elucidating the associated mechanisms.