Evaluation of Antimicrobial Activity and Safety Aspect of Enterococcus ItalicusGGN10 Strain Isolated from Tunisian Bovine Raw Milk

Abstract

Screening of lactic acid bacteria (LAB) from Tunisian raw bovine milk has resulted in the isolation of an Enterococcus italicus strain designated as GGN10, which has demonstrated a bacteriocin-like activity against Listeria spp. Antibacterial activity in the culture supernatant was lost after treatment with proteolytic enzymes, whereas it was stable over a wide range of pH (2-10). The treatment of extracellular extract of this strain at 100C did not cause loss of antimicrobial activity. The bacteriocin yield reached a maximum of 67,677.1AU/mL at the beginning of the exponential growth phase and remained stable during 24h of incubation. Amplification of bacteriocin genes revealed entA and entB genes present in GGN10. In addition, this result was confirmed by the bacteriocin's reversed-phase high-performance liquid chromatography purification and mass spectrometry analysis. This is the first report on enterocins A and B production by this newly isolated strain. Safety elucidation and antibiotics susceptibility of E.italicusGGN10 was conducted using polymerase chain reaction analysis. No commonly associated pathogenicity islands were identified. An enzymatic study revealed GGN10 as a high producer of acid phosphatase and aminopeptidase, which are important features in flavor and texture development during fermentation. Thus, E.italicusGGN10 produces antimicrobial substances and other biologically active substances of importance for food preservation.