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

<i>Bacillus cereus</i>, 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 <i>Toona sinensis</i> extracts against <i>B. cereus</i>. All tested <i>T</i>. <i>sinensis</i> varieties demonstrated significant antibacterial activity against <i>B. cereus</i>, with inhibition zone diameters exceeding 11 mm (P < 0.05). Notably, the extracts from Sichuan Dazhu exhibited strong antibacterial effects, even against antibiotic-resistant <i>B</i>. <i>cereus</i> 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 <i>B</i>. <i>cereus</i>, 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 <i>B</i>. <i>cereus</i> in skim milk. Collectively, these results underscore the significant antibacterial and antibiofilm potential of <i>T</i>. <i>sinensis</i> extracts, highlighting their potential applications in food safety. This report provides the first evidence of both antibacterial and antibiofilm activities in <i>T</i>. <i>sinensis</i> extract against <i>B</i>. <i>cereus</i>, while also elucidating the associated mechanisms.