ANTAGONISTIC ACTIVITY OF LACTIC-ACID BACTERIA ISOLATED FROM NATURAL WHEY STARTERS FOR WATER-BUFFALO MOZZARELLA CHEESE MANUFACTURE

Thirty-four Streptococcus thermophilus, 72 lactococci, 27 enterococci, 30 lactobacilli and 30 leuconostocs isolated from natural whey starte rs for water-buffalo Mozzarella cheese manufacture were screened for a ntagonistic activity. Antagonistic activity due to acidification was w idespread among lactobacilli. No strain among these microorganisms as well as among Str. thermophilus or leuconostocs produced bacteriocins. Lactococci (16.7%) and enterococci (40.7%) were found to produce bact eriocin-like inhibitors in solid media. Four and three different types of bacteriocins, respectively, produced by lactococci and enterococci both on solid and liquid media could be differentiated by cluster ana lysis considering the inhibitory spectrum against 37 indicators, inclu ding lactic acid bacteria, spoilage and pathogenic organisms, cross-in hibition patterns, and sensitivity to heat and proteolytic enzymes. So me substances clearly differed from known bacteriocins. The lactococci ns found are of great interest as potential food preservatives because of their activity towards Clostridium spp. Some enterocins showed int eresting activity towards Listeria monocytogenes. Media for optimal ba cteriocin production varied among strains. In the case of lactococcal strain 140, a surprisingly highly active bacteriocin was produced unde r all the conditions assayed.