CHARACTERIZATION OF A BACTERIOCIN PRODUCED BY STREPTOCOCCUS-THERMOPHILUS-81

A new bacteriocin, produced by Streptococcus thermophilus 81 has been isolated, purified and characterized. By its heat sensitivity and broa d inhibitory spectrum it does not resemble any other S. thermophilus b acteriocin. The mode of action is bacteriostatic. This peptide of 32 a mino acids is efficient against several Bacillus species, Listeria mon ocytogenes, Salmonella typhimurium, Escherichia coli, Yersinia pseudot uberculosis and Yersinia enterocolitica. This bacteriocin is heat labi le but its activity was not altered by pH variation from 3 to 10. Six months of storage at 40 degrees C did not influence the activity. The inactivation by detergents and the inability to resolve the protein in SDS-PAGE supposes a more complex structure or a possible stabilizing effect of other molecules. The low sensitivity of Lactobacillus delbru eckii subsp. bulgaricus to the isolated bacteriocin suggests that S. t hermophilus 81 may be used in yoghurt starters. (C) 1998 Elsevier Scie nce B.V.