Enterocin 012, a bacteriocin produced by Enterococcus gallinarum isolated from the intestinal tract of ostrich

Enterococcus gallinarum strain 012, isolated from the duodenum of ostrich, produced enterocin 012 which is active against Ent. faecalis, Lactobacillus acidophilus, Lact. sake, Listeria innocua, Propionibacterium acidipropionici, Propionibacterium sp., Clostridium perfringens, Pseudomonas aeruginosa and Salmonella typhimurium. One of the four pathogenic strains of Escherichia coli isolated from the intestinal tract of ostrich was inhibited by enterocin 012. No antimicrobial activity was recorded against Bacillus cereus, Cl. sporogenes, Cl. tyrobutyricum, Leuconostoc cremoris, Pediococcus pentosaceus, Staphylococcus carnosus and Streptococcus thermophilus. Enterocin 012 was resistant to treatment with lysozyme, catalase, lipase and papain, but sensitive to Proteinase K, α‐chymotrypsin, trypsin and pepsin. Treatment of enterocin 012 with gastric juice from the duodenum resulted in a 50% loss of antibacterial activity. Half of the activity was lost when incubated at 80 °C for 30 min, or when kept overnight at a pH of 1·0–5·0 and pH 11·0 and 12·0, respectively. Enterocin 012 production started in mid‐logarithmic growth and reached a maximum of 800 AU ml−1, but increased further to 1600 AU ml−1 in the stationary growth phase. The peptide is approximately 3·4 kDa in size, as determined after partial purification with Amberlite XAD‐1180 and ammonium sulphate precipitation, followed by tricine‐sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. The mechanism of antimicrobial activity against Lact. sake LMG 13558 is bactericidal and caused cell lysis of active growing cells.