Development of Purification Method and Identification of a Peptide Antibiotic Produced by Lactococcus lactis IO-1

Abstract

The culture supernatant of Lactococcus lactis IO-1, which was isolated in our laboratory, inhibited the cell growth of various Gram-positive bacteria but did not inhibit the nisin A-producing strain, L. lactis NCDO 497. A nisin-like peptide antibiotic produced by L. lactis IO-1 was efficiently purified sequentially by acid treatment (at pH 3), ammonium sulfate precipitation, cation-exchange chromatography and reversed-phase high performance liquid chromatography. Dissociation of the peptide aggregates with high molar concentrations of urea resulted in successful purification. The molecular mass of this peptide antibiotic was 3335.67 by fast atom bombardment-mass spectrometry, confirming that the peptide antibiotic from L. lactis IO-1 is nisin Z, a natural nisin variant. The purification method used is rapid, simple and effective, permitting the specific activity to increase 122-fold, and the recovery was 24%.