Abstract

Bacteriocins are antimicrobial proteinaceous compounds that are inhibitory towards sensitive strains and are produced by both Gram-positive and Gram negative bacteria. The enterococci produce anctibacterial peptides (bacteriocins), generally called enterocins. Several Enterococcus faecium strains isolated from Sardinian goat milk were tested by the agar spot-test and the well-diffusion-method, for their inhibitory effects toward some pathogenic microrganisms growth. Four of them presented antilisterial and antisalmonella activity and based on Gram staining, catalase test and according to their physiological and biochemical characteristics, were indentified as Enterococcus spp. The inhibitors produced by these strains were sensitive to proteases. Inhibition due to lytic bacteriophages was ruled out, so the isolates were classified as bacteriocin-like-substances producing lactic acid bacteria. In addition bacteriocins SD1, SD2, SD3 and SD4 activity was determined against large number of different LAB, L. monocytogenes from different serological groups, Gram-negative bacteria. All of them remained active after 120 min at 100 °C. Bacteriocins SD1 and SD2 were produced at much higher levels (51200 AU/mL) compared to bacteriocins SD3 (6400AU/mL) and SD4 (800 UA/ml).
In the second part of this study, the aim was to determine the conditions needed for optimal production and study some aspects of mode of action of bacteriocins produced by these E. faecium strains.

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