Purification and characterization of the Lactobacillus acidophilus bacteriocin lactacin B

Parameters for production and purification of a bacteriocin produced by Lactobacillus acidophilus N2 are described. Production of lactacin B was pH dependent, with maximum activity detected in broth cultures maintained at pH 6. Lactacin B was purified by ion-exchange chromatography, ultrafiltration, and successive gel filtrations in the presence of 8 M urea and then 0.1% sodium dodecyl sulfate. The molecular weight of lactacin B was ca. 6,000 to 6,500, and the purified compound showed maximum absorbance at 211 nm. The activity of purified lactacin B was bactericidal to sensitive cells and restricted to members of the family Lactobacilliaceae, L. leichmannii, L. bulgaricus, L. helveticus, and L. lactis. Characteristics identified for lactacin B indicated that it was a peptide and confirmed its identity as a bacteriocin.