L actic acid bacteria (LAB) and related microorganisms such as propionic acid bacteria are important microorganisms that are used in dairy and food industries. LAB and other food grade organisms have been subjected to intensive research due to their potential use as food preservatives (Stiles, 1996). Antimicrobial peptides (bacteriocins) produced by food-associated microorganisms can be used as natural preservatives. Bacteriocins are produced by numerous Grams-positive and Grams-negative bacteria (Tagg et al., 1976). Bacteriocins are ribosomally synthesized antimicrobial peptides or proteins with antagonistic activity (Cummins and Johnson, 1986; De Vuyst and Vandamme, 1994). They are consumed in LAB-fermented food and their actions result in desirable food characteristics, such as taste and appearance (eyeholes) in Swiss cheese. Thus, like LAB, they are a preferred source of antimicrobial agents that could be employed as new food preservatives because of their presumed non-toxicity for humans (Daeschel et al., 1990). Propionibacterium ssp. are able to produce a wide variety of biological compounds that enhance the human health like folic acid, proline, conjugated linoleic

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