Antimicrobial activity of lactobacilli: preliminary characterization and optimization of production of acidocin B, a novel bacteriocin produced by Lactobacillus acidophilus M46

摘要

Approximately 1000 lactobacillus strains were isolated and screened for the production of antimicrobial activity, using a target panel of spoilage organisms and pathogens. Only eight positive strains were found; two of these were studied in more detail.Lactobacillus salivariusM7 produces the new broad spectrum bacteriocin salivaricin B which inhibits the growth ofListeria monocytogenes, Bacillus cereus, Brochothrix thermosphacta, Enterococcus faecalisand many lactobacilli. A new atypical bacteriocin produced byLact. acidophilusM46, acidocin B, combines the inhibition ofClostridium sporogeneswith a very narrow activity spectrum within the genusLactobacillusand was selected for further characterization. Acidocin B is sensitive to trypsin, heat‐stable (80°C for 20 min) and can be extracted from the culture supernatant fluid with butanol. Native acidocin B occurs as a large molecular weight complex (100 kDa), while with SDS‐PAGE the partly purified activity migrates as a peptide of 2·4 kDa. Optimization of the cultivation conditions resulted in an eightfold increase of the amount of acidocin B produced during growth. Growth is not necessary for acidocin B production; washed producer cells can synthesize the bacteriocin in a chemically defined production medium. The application potential of acidocin B is disc