Detection and characterization of a novel antibacterial substance producedby Lactobacillus plantarum ST 31 isolated from sourdough

Lactobacillus plantarum ST31 isolated from sourdough produced an antimicrob ial substance inhibiting other strains of the genera Lactobacillus, Leucono stoc, Pediococcus, Streptococcus, Bacillus and some foodborne pathogens inc luding Staphylococcus aureus. This antimicrobial substance was inactivated by proteolytic enzymes. Consequently, it was characterized as a bacteriocin and was designated plantaricin ST31. This bacteriocin was stable in the pH range 3-8 and it was not affected by amylolytic enzymes. Production of pla ntaricin was pH and temperature dependent, and maximum yields were obtained in MRS broth cultures maintained at pH 6 and incubated at 30 degrees C in the exponential phase to the early stationary growth phase of the producer organism. This bacteriocin was purified by using consecutive ammonium sulfa te and reversed-phase chromatography, It is a peptide of 20 amino acid resi dues with a mass of 2755+/-0.3 Da, as determined by electrospray mass spect rometry. The sequence of Plantaricin ST31 showed no similarity to those of other bacteriocins. Plantaricin ST31 production appeared to be chromosomall y encoded. (C) 1999 Elsevier Science B.V. All rights reserved.