Abstract
In this study, a bacteriocin produced by Lactococcus lactis subsp. lactis PD6.9 was purified, characterized and identified. The bacteriocin was purified to homogeneity from culture supernatant by cation exchange and reversed-phase liquid chromatography, and its molecular weight was determined by mass spectrometry. The presence of the nisin gene was confirmed by polymerase chain reaction (PCR) and DNA sequencing. The gene showed that it was a natural nisin variant, nisin Z, as indicated by substitution of an asparagine residue for histidine at position 27. The purified bacteriocin was biochemically pure, and the molecular weight was approximately 3329.571 Da. The peak of nisin Z production by L. lactis PD6.9 occurred after 5 h of culture during stationary phase. This bacteriocin demonstrated inhibitory activity towards significant foodborne pathogens and Staphylococcus aureus strains isolated from dairy cattle diagnosed with mastitis, it may be useful for future applications. Key words: Antimicrobials, Lactococcus lactis, bacteriocins, identification, inhibitory activity.
Highlights
Lantibiotics are antimicrobial peptides that have attracted widespread scientific attention as promising safe and natural food additives and as potential therapeutic agents to combat medically significant bacteria and their multidrug resistance (Field et al, 2008)
Exponential growth of L. lactis subsp. lactis took place during a period of approximately 4 h, and bacteriocin production began during the exponential phase (Figure 1)
We have carried out the identification and purification of the antimicrobial compound produced by a naturally fermented salami isolate of lactic acid bacteria, L. lactis subsp. lactis PD6.9 (Maciel, 1998)
Summary
Lantibiotics are antimicrobial peptides that have attracted widespread scientific attention as promising safe and natural food additives and as potential therapeutic agents to combat medically significant bacteria and their multidrug resistance (Field et al, 2008). Nisin A is a lantibiotic produced by Lactococcus lactis, has already been employed as a food preservative for long time and is licensed by 48 countries around the world (DelvesBroughton, 1990) and is one of the few bacteriocins to have been applied commercially (Bierbaum and Sahl, 2009). This peptide is suggested to be effective.
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