Bacteriocins from Lactic Acid Bacteria

Probiotics are the beneficial bacteria that are indigenous to a healthy digestive system. Basically, these are live microorganisms, which are administered in adequate amounts in order to provide health benefit to the host. They work by crowding out the bad bacteria within the digestive system and then attaching themselves to the intestinal wall where they increase the number of beneficial bacteria regulating and maintaining balance between the beneficial and harmful bacteria. The tradition of eating foods (such as yogurt, sauerkraut, fermented milk, miso and soy beverages) fermented with bacteria is solely based on health benefits provided by these bacteria. Thousands of different lactic acid bacteria (LAB) are used as probiotics, and the dominant members are Bifidobacteria (Bifidobacterium bifidum) and Lactobacteria (Lactobacillus acidophilus, Lactobacillus plantarum). The benefits associated with the use of probiotic bacteria are well documented, but their mechanism of action still remains very unclear. LAB protect food from spoilage and pathogenic microorganisms by producing organic acids, hydrogen peroxide, diacetyl, antifungal compounds such as fatty acids or phenyllactic acid and bacteriocins. Bacteriocins are a heterogeneous family of small, heat-stable peptides that are produced by many bacterial species, including many probiotic strains. Bacteriocins of LAB are considered as safe natural preservatives with potent antimicrobial activities and antagonistic affect. Bacteriocins mainly prevent food spoilage by inhibiting growth of food-borne pathogenic microorganisms. They also protect the body from cancer and effectively improve the immune system. These are classified into several groups in which classes I (Lantibiotics) and II (Bacteriocins) are studied most thoroughly. The present review is concerned with the diversity of bacteriocins, their expression system and their applications which lead to use of lactic acid bacteria as probiotics.