Antimicrobial Activity And The Preliminary Antibacterial Mechanism For L. Monocytogenes Of The Phenyllactic Acid

Phenyllactic acid(PLA)is a small molecule bactericidal substance produced by lactonacillus with properties of safety,non-toxic,good stability.Since PLA can inhibit and kill a variety of microorganisms such as pathogenic bacteria and spoilage organisms.it has become one of the current hot spots in the research field of biological preservative.This experiment aimed to investigate the antibacterial properties of PLA and gain the insights into antibacterial mechanism of Listeria monocytogenes considered as Food-borne pathogenic bacteria.Analysis method of the antibacterial activity of PLA was established in this study:Agar diffusion method was identified for the qualitative detection of antifungal activity of phenyllactic acid(PLA),and S.aureus ATCC 14458 was used as indicator.Then,titer standard curve of PLA was prepared,which was used to determine the antibacterial activity of phenyllactic acid(PLA).Afterwards,the antibacterial ability of PLA against Gram-positive bacteria(G+),Gram-negative bacteria(G-)was determined by agar diffusion process.The antibacterial activity of PLA gainst L.monocytogenes was studied Firstly,the MIC of PLA was determined.The MIC of D-PLA and L-PLA to L.monocytogenes EGD or L.monocytogenes scottA are both 2.5 mg/mL,while the MIC of sodium benzoate is 16 mg/mL.The MIC of D-PLA and L-PLA to L.monocytogenes 10403s are 2 mg/mL,while The MIC of sodium benzoate is 16 mg/mL.The results indicated that PLA showed greater antibacterial activity than that of sodium benzoate.Secondly,the antibacterial ability of PLA configuration for L.monocytogenes was compared by agar diffusion method,the results showed that the inhibitory of D-PLA and L-PLA have no significant differences.Then,the combined effects of the D-PLA and lactate for L.monocytogenes 10403s was investigated by broth dilution method and the results showed that the combination of D-PLA plus lactic acid results in a synergistic effect to L.monocytogenes 10403s.The bactericidal kinetic curve of L.monocytogenes 10403s composed with PLA was demonstrated.It was observed that the cell wall was damaged as shown by Transmission electron microscopy(TEM).And then,the integrity of cell membrane was detected by spectrophotometer,the results suggested that cell wall would be one of the targets for PLA.