Abstract

Lactic acid bacteria play a key role in maintaining the balance of normal gastro-intestinal micro flora. Food contamination by Staphylococcus aureus is a major problem for consumer’s health in Algeria, especially during the summer period. The use of bacterial interactions is a new way to limit the pathogenic germs growth. Detection of antimicrobial substances produced by lactic acid bacteria against the undesirable germs is the objective of this work. Microbiological and biochemical methods were used to identify lactic acid bacteria having an antimicrobial activity. The 2 isolates of lactic acid bacteria obtained from raw goats’ milk in western Algeria's areas were identified: Lactobacillus rhamnosus, Lactobacillus plantarum. The interactions study revealed that three lactobacilli species: L. plantarum (58) and L. plantarum (68) are able to inhibit S. aureus’ growth. In mixed culture after 24 h, L. plantarum reduces the growth of S. aureus by 1.6 log and this latter bacteria was not found after 72 h. The various tests used reveal the proteinic nature of the substance which was responsible for the growth inhibition of S. aureus. The ecological adaptation and growth characteristics of cultures of L. plantarum in food products will determine their effectiveness as bio-control agent in dairy foods.

Key words: Raw goats’ milk, lactic acid bacteria, Lactobacillus plantarum, interaction, bacteriocin, Staphylococcus, mixed culture.