Fifty-five strains of Bacillus (53 B. laevolacticus and 2 B. racemilacticus) and 31 strains of Sporolactobacillus (3 S. inulinus, 19 S. laevus, and 9 S. racemicus) were screened for specific inhibitory activity against 8 strains of Listeria monocytogenes. Putative producer strains were propagated in Eugon, lactobacillus MRS, or sporolactobacillus broths (48-96 h, 37°C, 9.4% CO2). Assays to detect inhibition of Listeria monocytogenes were carried out on Eugon or Bacto-Agar at 37°C (9.4% CO 2). Inhibition was absent in direct assays using spot-on-the-lawn techniques but was found in well diffusion assays, and in deferred assays using stabinoculation techniques. Cell-free supernatant fluids of cultured MRS broths demonstrated superior inhibition to cell-free supernatants from Eugon and sporolactobacillus broths. The inhibitory activity of cell-free supernatant fluids was lost after neutralization (0.5M NaOH) or by dialysis (10,000 Da exclusion limit). The observed inhibition was most likely due to production of lactic acid.
All Science Journal Classification (ASJC) codes
- Food Science