Purification and characterization of a two-peptide bacteriocin with synergistic activity from Enterococcus faecalis MGL-3

Bacteriocins are food-grade bioactive peptides produced by some bacterial strains, including lactic acid bacteria (LAB). Bacteriocins derived from food-grade LAB possess enormous potential for various applications in the food and medical industries. A newly isolated lactic acid bacterium from a fermented vegetable, strain MGL-3, was found to produce two bioactive peptides. In this study, the identification of strain MGL-3 as well as the purification and partial characterization of its bacteriocinogenic peptides are described. Morphological, biochemical, and bioinformatic analyses revealed that strain MGL-3 is an Enterococcus faecalis strain. Two bioactive peptides were purified from the cell-free supernatant of strain MGL-3 after a 3-step purification scheme involving salt precipitation and chromatographic techniques. Characterization of these peptides showed that they exhibit relatively weak bioactivity when tested alone but manifest very potent bioactivity when combined, suggesting synergistic activity. The antibacterial spectrum of these peptides was found to target many bacterial strains that are known contaminants in the vegetable pickle industry, highlighting their potential utility in the industry. Nonetheless, further study is needed to confirm the novelty of these peptides, such as the determination of their amino acid sequence and/or the identification of their biosynthetic gene cluster.