Purification and characteristics of bifidocin A, a novel bacteriocin produced by Bifidobacterium animals BB04 from centenariansʹ intestine

Bacteriocin-producing strain BB04, isolated from centenariansʹ intestine and identified as Bifidobacterium animals, produced the maximum activity of bifidocin A (640 AU/ml) in MRS medium supplemented with 0.05% (w/v) l-cysteine hydrochloride in the mid-stationary phase of growth (i.e. after 32 h at 37 °C). The bacteriocin, with a molecular mass of 1198.68 Da, was successfully purified by a four-step procedure consisting of adsorption and desorption onto/from producer cells, cation-exchange chromatography, gel filter chromatography and reverse phase high-performance liquid chromatography (RP-HPLC). Purified bifidocin A exhibited a wide range of antimicrobial activity against many food-borne spoilage and pathogenic bacteria such as Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, as well as some yeast. The mode of action of bifidocin A was bactericidal with concomitant cell lysis. Also, bifidocin A was heat stable, pH resistant and protease sensitive. EDTA, Tween 80, Tween 20 and urea did not decrease the activity, whereas, SDS induced 36% activity loss. This is the first report on a bacteriocin produced by B. animals. And the characterization, antimicrobial spectrum and molecular mass of bifidocin A suggested that it was a novel bacteriocin with potential research and application value in food industry.