Antibacterial mechanism of sucrose laurate against Bacillus cereus by attacking multiple targets and its application in milk beverage.

Sucrose laurate (SL) is a promising dual-functional additive due to its emulsification and antibacterial activity. However, the knowledge on the antibacterial action of SL against Bacillus cereus was lacking, and thus it was investigated from multiple targets. The antibacterial results demonstrated that the minimum inhibitory concentration of SL was 0.3125 mg/mL, and the time-killing curve confirmed the strong antibacterial activity of SL. The alkaline phosphatase assay suggested that SL disrupted the cell wall integrity. The flow cytometry and fluorescence spectroscopy analysis indicated that SL damaged the integrity of cell membrane and dissipated the transmembrane potential, resulting in the leakage of intracellular materials, which were further supported by scanning electron microscopy and transmission electron microscopy. iTRAQ-based proteomic analysis indicated that SL down-regulated cell wall-associated hydrolase, inhibited the synthesis of fatty acids, influenced nucleic acid synthesis, disturbed amino acid metabolism, and blocked HMP pathway and TCA cycle. Finally, the promising application of SL was evidenced in milk beverage. This investigation could provide scientific basis for the practical application of SL as a dual-functional food additive.

iTRAQ-based quantitative proteomic analysis of synergistic antibacterial mechanism of phenyllactic acid and lactic acid against Bacillus cereus.

Phenyllactic acid (PLA) as a phenolic acid by lactic acid (LA) bacteria shows enhanced antibacterial activity when coexisting with LA, while the antibacterial mechanism of PLA combined with LA was unknown. Hence, the antibacterial mechanism of PLA and LA was investigated against Bacillus cereus. Flow cytometry and TEM analysis demonstrated that single PLA and LA disrupted the membrane integrity and the morphology, while combined PLA and LA synergistically enhanced the damage. iTRAQ-based proteomic analysis suggested that PLA down-regulated kdpB and inhibited K+ transport, disturbed the function of ribosome and expression of competence genes; LA down-regulated periplasmic phosphorus-binding proteins and inhibited phosphorus transport, disturbed the function of ribosome, TCA cycle, as well as purine and pyrimidine metabolism; and combined PLA and LA inhibited K+ and phosphorus transport, and influenced the synthesis of purine and pyrimidine metabolism. The investigation could provide some insights into the application of PLA in food preservation.