Mechanism and application of camellia saponins against Bacillus cereus biofilm formation on different food contact surfaces

Bacillus cereus is a serious foodborne pathogen. In nature, it can form biofilms on the surface of food utensils and food processing equipment, making it difficult to remove. In this study, the model strains B. cereus ATCC 10987 and ATCC 14579 were selected as test strains to investigate the mechanism and inhibition of biofilm by camellia saponins (CS), in order to provide a new reference for the development of a natural antibiofilm. CS had a good inhibitory on biofilms of B. cereus ATCC 10987 and ATCC 14579, with minimal biofilm inhibitory concentration (MBIC) and minimal biofilm eradication concentration (MBEC) of 64 mg/mL and 128 mg/mL, respectively, and could reduce the exopolysaccharide and eDNA secretion of B. cereus by CLSM, thereby destroying the biofilm's structure and inhibiting the early adhesion and metabolism of individual bacteria within the biofilm. The qRT-PCR showed that CS can down-regulating the expression of nine biofilm formation related genes (spo0A, codY, rpoN, comER, sinR, plcR, papR, nprR and LuxS), thus directly or indirectly affect the biofilm formation. Combined with semi-quantitative detection of AI-2 signaling molecules, it is speculated that CS inhibits the B. cereus biofilm formation by inhibiting LuxS gene expression is to reduce the production of AI-2 and down-regulate the expressions of PlcR and PapR genes, thus inhibiting the quorum sensing mediated by LuxS/AI-2 and PlcR-PapR systems. Finally, the application of CS on stainless steel, ceramic and glass surfaces showed that the ceramic surface had greater biofilm inhibition. Moreover, CS showed a better antibiofilm effect as contact time increased.