Rapid Isolation and Purification of Secreted Bacteriocins from Streptococcus mutans and Other Lactic Acid Bacteria

Bacteriocins are small ribosomally synthesized antimicrobial peptides produced by some microorganisms including lactic acid bacteria (LAB), a group of Gram-positive bacteria (cocci, rods) expressing high tolerance for low pH. Bacteriocins kill bacteria rapidly and are biologically active at very low concentrations. Bacteriocins produced by LAB are primarily active against closely related bacterial species. Many bacteriocins have been investigated with respect to their potential use in promoting human, plant, and animal health, and as food biopreservatives. Bacteriocins produced by LAB are particularly interesting since several LAB have been granted GRAS (Generally Recognized as Safe) status. Because it is not always possible to extract active bacteriocins secreted from cells grown in liquid medium, we developed a simple and inexpensive peptide extraction procedure using a semi-solid nutrient-rich agar medium. We hereby present a detailed procedure that leads to the rapid extraction of secreted bioactive bacteriocin peptides from the oral species Streptococcus mutans, a prolific bacteriocin-producing species, and its potential application for bacteriocin extraction from other LAB (e.g., Streptococcus, Lactococcus, Enterococcus). We also present a simple method for the detection of bacteriocin activity from the purified extracellular peptide extract.