Purification of bacteriocin LS1 produced by human oral isolate Lactobacillus salivarius BGHO1

Introduction: Lactobacillus salivarius BGHO1, a human oral isolate with antagonistic activity against growth of Streptococcus mutans, Streptococcus pneumoniae, Staphylococcus aureus, Enterococcus faecalis, Micrococcus flavus, and Salmonella enteritidis, probably produces more than one proteinaceous antimicrobial substance. The objective of this study was the purification of a bacteriocin, named LS1, produced by L. salivarius BGHO1. Methods: A simple and fast procedure for bacteriocin purification was developed, consisting of reverse-phase chromatography of the ammonium sulfate precipitate of cell-free culture supernatant by fast protein liquid chromatography and high-performance liquid chromatography, followed by tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), with the subsequent extraction of bacteriocin from the gel. Results: The supernatant of L. salivarius BGHO1 culture retained its antimicrobial activity after boiling in a water bath for 15 min. Its antimicrobial activity was also maintained even after treatment for 20 min at 121 degrees C in an autoclave. Bacteriocin LS1 was purified to homogeneity. The molecular mass of bacteriocin LS1 was estimated to be approximately 10 kDa, based on tricine SDS-PAGE. During purification, another compound with antimicrobial activity, produced by L. salivarius BGHO1, was detected. The molecular mass of this compound was estimated to be approximately 5 kDa, based on tricine SDS-PAGE. Conclusion: Our results imply that LS1 is most probably a new bacteriocin, different from previously described bacteriocins produced by L. salivarius strains. The purification of bacteriocin LS1 enabled the further characterization of LS1 on both the molecular and genetic levels.