Purification and partial amino acid sequence of plantaricin 1.25ααα and 1.25βββ, two bacteriocins produced by Lactobacillus plantarum TMW1.25

Two bacteriocins produced by Lactobacillus plantarum TMW1.25 have been purified by a four-step purification procedure, including ammonium sulphate precipitation and cation-exchange chromatography followed by hydrophobic-interaction chromatography on octyl sepharose. The final purification was performed by repeated reversed-phase chromatography steps which yielded two bacteriocin fractions designated plantaricin 1.25 alpha and plantaricin 1.25 beta. The molecular masses of the peptides in these fractions were 5979 and 5203 Da, respectively. Combination of the fractions did not have any synergistic effects on bacteriocin activity, indicating that they each contain a one-peptide bacteriocin. The major peptide in the alpha fraction was blocked at its N-terminus, and a partial sequence (25 residues) could only be obtained after cleavage with CNBr. This sequence did not show clear homologies with known bacteriocins. The beta peptide has been sequenced almost completely and consists, presumably, of 53 residues. This peptide displayed strong homology to the known N-terminal part of brevicin 27 produced by Lactobacillus brevis SB27. The results showed that the beta peptide contains as many as six consecutive lysine residues at the N-terminus.