The inhibitory effect of Lactobacillus plantarum (Lb. plantarum) which is bacteriocinproducing strain against the growth of Listeria monocytogenes (L. monocytogenes) was examined in trypticase soy broth (TSB). TSB was inoculated with 104 cells/me L. monocytogenes and then with different numbers $(10^6;10^4;and;10^2;cells/ml)$ of Lb. plantarum. The mixed cultures were incubated at 37, 25 and $4^{circ}C$. The most effective inhibition of was found at $37^{circ}C$ and a less inhibition at $25^{circ}C$. However, there was no significant change in the cell numbers of both L. monocytogenes and Lb. plantarum at $4^{circ}C$. At same incubation temperature, the higher initial inoculum level of Lb. plantarum, the better inhibitory effect against L. monocytogenes. In addition, TSB was inoculated with L. monocytogenes at different initial inoculum levels of $10^6,;10^4$ and $10^2$ cells/me and then supplemented with 0, 30, 60 and 100 AU/ml of bacteriocin produced by Lb. plantarum. The mixed cultures were incubated at 37, 25 and $4^{circ}C$. L. monocytogenes of three different initial inoculum levels began to be inhibited in the presence of more than 60 AU/ml of bacteriocin at $37^{circ}C$. In TSB containing more than 60 AU/me of bacteriocin and incubated at $25^{circ}C$, L. monocytogenes decreased by 2 log-units during the period of 12 hrs incubation and thereafter remained steady. At $4^{circ}C$, L. monocytogenes decreased by 1.5 log-units in the presence of 60 AU/ml bacteriocin during the period of 4 days incubation and dropped to the non-detectable level in TSB with 100 AU/ml bacteriocin.
