CHARACTERIZATION AND ANTIMICROBIAL SPECTRUM OF BIFIDOCIN-B, A BACTERIOCIN PRODUCED BY BIFIDOBACTERIUM-BIFIDUM NCFB-1454

Five strains of Bifidobacterium bifidum (ATCC 11863 and 29591, and NCF B 1453, 1454, and 1455) were examined for production of bacteriocins i n MRS broth with 0.05% cysteine. Only strain NCFB 1454 excreted a bact eriocin into the broth; it was designated bifidocin B. Bifidocin B was sensitive to several proteolytic enzymes (protease IV, pronase E, pro tease XVII, proteinase K, trypsin, alpha-chymotrypsin, papain, and pep sin), but was resistant to catalase, peroxidase, lipase, lysozyme, cel lulase, ribonuclease A, and amylases. It was also resistant to organic solvents such as ethyl alcohol, acetone, hexane, chloroform, methanol , and ether, and to heating at 90 degrees C for 15, 30, and 60 min or at 121 degrees C for 15 min. Bifidocin B remained active after storage at -20 or -70 degrees C for 3 months and retained biological activity after exposure to pH values of 2 to 10. Bifidocin B was active agains t some food-home pathogens and food spoilage bacteria such as Listeria , Enterococcus, Bacillus Lactobacillus, Leuconostoc, and Pediococcus s pecies but was not active against the other gram-positive and gram-neg ative bacteria tested. Bifidocin B was produced during exponential pha se, reaching a maximum activity of 3,200 AU/ml at early stationary pha se. Bifidocin B had a molecular mass of about 3.3 kDa as analyzed by T ricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis.