For centuries lactic acid bacteria (LAB) have been used as biocatalysts for the production of fermented dairy foods, including cheese and yogurt. Several of these dairy cultures have also been shown to naturally produce antimicrobial peptides call bacteriocins, which have the potential to prevent spoilage and foodborne illness. In addition, LAB which produce broad spectrum bacteriocins have been investigated for their potential as probiotics for inclusion in functional foods. ARS research currently focuses on the identification of novel bacteriocin-producing LAB, and characterization of the molecular mechanisms which regulate peptide expression. These studies have identified two Streptococcus thermophilus strains, ST109 and ST110, which naturally produce broad spectrum bacteriocins encoded within a bacteriocin-like peptide (blp) gene cluster on the bacterial chromosome. The natural production of these bacteriocins is unique in that other characterized strains require the use of a synthetic peptide to induce bacteriocin production. The broad spectrum antimicrobial activity of thermophilin 110, which includes activity against Listeria monocytogenes and streptococcal pathogens, suggests it has potential food safety and probiotic applications. Streptococcus thermophilus and other dairy LAB have also been investigated as microbial production systems for generating potential food-grade bacteriocins with anti-listerial activity, such as pediocin and durancin GL. Duancin GL is a bacteriocin that is naturally produced by Enterococcus durans 41D, which was identified as part of the indigenous microflora in a raw-milk cheese. The genetic elements required for the production of durancin GL have been characterized; and the strain is currently being investigated for its potential to serve as an adjunct culture for preventing the growth of L. monocytogenes.

Characterization of LAB bacteriocins with the potential for food safety and functional food applications

252nd National Meeting (2016)

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