FOOD SCIENCE ›› 2020, Vol. 41 ›› Issue (23): 70-76.doi: 10.7506/spkx1002-6630-20191106-071

• Basic Research • Previous Articles     Next Articles

Synergistic Antibacterial Mechanism of Phenyllactic Acid Combined with Acetic Acid against Listeria monocytogenes

NING Yawei, FU Yunan, HE Jianzhuo, SU Dan, HOU Linlin, WANG Zhixin, JIA Yingmin   

  1. (1. School of Biological Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China; 2. School of Food and Health, Beijing Technology and Business University, Beijing 100048, China)
  • Online:2020-12-15 Published:2020-12-28

Abstract: Objective: To investigate the synergistic antibacterial activity and mechanism of phenyllactic acid (PLA) combined with acetic acid (ACE) against L. monocytogenes. Methods: The double broth dilution method was used to measure the minimum inhibitory concentration (MIC) and the fractional inhibitory concentration index. The time-killing curve was constructed by plate counting method. The antibacterial mechanism was studied by measuring Zeta potential, membrane depolarization, membrane integrity, cell morphology and DNA damage. Results: The MICs of PLA and ACE were 2.25 and 1.75 mg/mL, respectively, and the fractional inhibitory concentration index of PLA in combination with ACE was 0.5, suggesting that combination of PLA (1/4 MIC) and ACE (1/2 MIC) can exert a synergistic effect against L. monocytogenes. Zeta potential results showed that PLA and/or ACE effectively changed the cell surface charge. DiSC3(5) fluorescent probe labeling results indicated that PLA and ACE could dissipate membrane potential. Flow cytometry and fluorescence microscopy analysis showed that PLA, ACE and their combination could disrupt cell membrane integrity. After treatment with PLA at MIC, ACE at MIC or PLA (1/4 MIC) plus ACE (1/2 MIC), L. monocytogenes cells became deformed and adhered together, and the contents leaked out. Gel electrophoresis images showed that PLA and ACE could damage DNA. Conclusion: Combination of PLA and ACE shows a synergistic antibacterial activity by reducing cell surface charge, causing membrane depolarization, destroying the integrity of the cell membrane and consequently entering into the cells to interact with DNA, and finally lead to cell death. This investigation can provide a theoretical basis for applying PLA in food preservation.

Key words: phenyllactic acid; acetic acid; antibacterial mechanism; cell membrane; DNA

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