EVALUATION OF LACTIC-ACID-PRODUCING BACILLUS AND SPOROLACTOBACILLUS FOR ANTILISTERIAL ACTIVITY

Fifty-five strains of Bacillus (53 B. laevolacticus and 2 B. racemilac ticus) and 31 strains of Sporolactobacillus (3 S. inulinus, 19 S. laev us, and 9 S. racemicus) were screened for specific inhibitory activity against 8 strains of Listeria manocytogenes. Putative producer strain s were propagated in Eugon, lactobacillus MRS, or sporolactobacillus b roths (48-96 h, 37 degrees C, 9.4% CO2). Assays to detect inhibition o f Listeria monacytogenes were carried out on Eugon or Bacto-Agar at 37 degrees C (9.4% CO2). Inhibition was absent in direct assays using sp ot-on-the-lawn techniques but was found in well diffusion assays, and in deferred assays using stabinoculation techniques. Cell-free superna tant 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 neu tralization (0.5M NaOH) or by dialysis (10,000 Da exclusion limit). Th e observed inhibition was most likely due to production of lactic acid .