Inhibition of Proteusbacillus vulgaris by Main Antibacterial Substances in Lactobacillus casei LDJ
Lactobacillus casei LDJ is an excellent strain that can inhibit the growth of Proteusbacillus vulgaris.To investigate the antibacterial effect of the cell-free supernatant of Lactobacillus casei LDJ,the antibacterial ability of cell-free supernatant with different fermentation time on Proteusbacillus vulgaris was tested by the Oxford cup method.When the fermentation time was 0-4 h,the cell-free supernatant had no antibacterial ability.The antibacterial ability increased gradually after fermentation of 8 h and tended to be stable when fermentation time was 24-48 h.Specifically,when the fermentation time was 36 h,the diameter of the antibacterial zone was the largest(20.48 mm).The research on physicochemical properties of the antibacterial substances in the cell-free supernatant of Lactobacillus casei LDJ shows that the antibacterial substance has various inhibitory effects on Escherichia coli,Staphylococcus aureus,and Listeria monocytogenes.The cell-free supernatant still has good antibacterial activity after treatment at 40-100℃for 30 min.The antibacterial substance has a good antibacterial effect in the range of pH value 3-6 but shows no antibacterial effect under neutral and alkaline conditions.Different enzyme treatments have different effects on the antibacterial effect of cell-free supernatant.Therefore,it is speculated that the effective antibacterial components of Lactobacillus casei LDJ may be peptides and organic acids.
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