EFFECT OF ENVIRONMENTAL AND NUTRITIONAL FACTORS ON THE PRODUCTION OF BACTERIOCIN-LIKE INHIBITORY SUBSTANCES (BLIS) BY ENTEROCOCCUS FAECIUM STRAINS

Five bacteriocin-like inhibitory substances (BLIS)-producer Enterococcus faecium strains (WGW7.2, WGJ17.2, WGJ21.2, WGJ28.1 and WGW33.2) were characterized for their antimicrobial compound production under several growth conditions, at different concentrations and with different sources of nutritional factors and in the presence of ethanol and NaCl. The strains showed different behaviours. MRS and SDB were found to be the optimal media for BLIS expression. A higher BLIS production was observed at 30 degrees and 37 degrees C and at a pH in the neutral range. Low or no BLIS activity was detected after growth in the absence of nitrogen sources, carbohydrates, MgSO4 and MnSO4. Ethanol did not generally play a negative role, while NaCl determined a consistent decrease in BLIS activity that was proportional to its concentration. Due to the absence of plasmids, BLIS production by all strains was chromosomally encoded. This study is part of a more comprehensive study aimed at characterizing lactic acid bacteria (LAB) associated with the raw materials used to prepare sourdough.