Production of bacteriocins by streptococci

ABSTRACT

Production of inhibitory substance [s] was investigated by using 8 strains of Streptococcus lactis ssp. lactis and 6 strains of Streptococcus lactis ssp. cremoris isolated from Domiati cheese samples. Among the strains tested, Streptococcus lactis spp. lactis 5 and 7 were found to inhibit the growth of S. lactis spp. lactis 1, 3 and 6, S. lactis spp., cremoris 11, 14, 19, 20 and CNRZ 117, Leuconostoc mesenteroides ssp. mesenteroids 1, Lactobacillus delbrueckii ssp. bulgaricus CNRZ 1188, 1183 and Lactobacillus plantarum 19. In contrast, strains of S. lactis ssp. cremoris tested did not inhibit the growth of indictor strains used. The inhibitor substance [s] was completely inactivated by alpha chemotrypsin, but it was less sensitive to trypsin and pronase. The optimum pH for the activity of antibacterial agent was 4.5-5. Addition of 4% NaCl to the growth medium of the producer strain reduced the titer of bacteriocin