Research Article Safety Aspect of Enterococcus faecium FL31 Strain and Antibacterial Mechanism of Its Hydroxylated Bacteriocin BacFL31 against Listeria monocytogenes Ahlem Chakchouk-Mtibaa, 1 Imen Sellem, 1 Yosra Kamoun, 2 Slim Smaoui , 1 Ines Karray-Rebai , 1 and Lotfi Mellouli 1 1 Laboratory of Microorganisms and Biomolecules, Center of Biotechnology of Sfax, University of Sfax, Road of Sidi Mansour Km 6, P.O. Box 1177, 3018, Tunisia 2 Laboratory of Molecular Biotechnology of Eukaryotes, Center of Biotechnology of Sfax, University of Sfax, Road of Sidi Mansour Km 6, P.O. Box 1177, 3018, Tunisia Correspondence should be addressed to Lotf Mellouli; lotf.mallouli@cbs.rnrt.tn Received 10 July 2018; Accepted 9 October 2018; Published 1 November 2018 Academic Editor: Heather Simpson Copyright © 2018 Ahlem Chakchouk-Mtibaa et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In previous work we have isolated and identifed a new strain called Enterococcus faecium FL31. Te active compound secreted by this strain, “BacFL31”, has been purifed and characterized. In the present study, safety aspect, assessed by microbiological and molecular tests, demonstrated that Enterococcus faecium FL31 was susceptible to relevant antibiotics, free of hemolytic, gelatinase, DNase, and lipase activities. In addition, it did not harbor virulence and antibiotic resistance genes. Combined SYTOX Green dye and UV-absorbing experiments, along with released extracellular potassium and transmembrane electrical potential measurements, showed that pure BacFL31 at a concentration of 1×MIC (50 g/mL) could damage cytoplasmic membrane of the pathogen Listeria monocytogenes ATCC19117. Te same concentration causes the leakage of its intracellular constituents and leads to the destruction of this pathogenic microorganism. In summary, this work refected characteristics of Enterococcus faecium FL31 strain and its bacteriocin in terms of functional and safety perspectives. 1. Introduction Enterococcus is a large genus of lactic acid bacteria (LAB) and several species from this genus have been used as probiotic for humans or animals [1]. In addition, some Ente- rococcus faecium spp. act as protective agents against food- spoilage and pathogenic bacteria, such as Listeria monocy- togenes, Salmonella typhimurium, Staphylococcus aureus, and Clostridium perfringens spores due to their ability to produce antimicrobial peptides called bacteriocins (enterocins) [2–5]. However, certain species of Enterococcus faecium can have relatively low virulence and cause nosocomial infec- tions especially endocarditis, septicemia, urinary tract infec- tions, meningitis, and others human infections [6]. Tese pathogenic strains can also carry multiple antibiotic resis- tances and several virulence factors like haemolysin, gelati- nase, invasins, adhesins, cytolysin, and enterococcal surface proteins [7]. It should be noted that several studies have shown that enterococci possessing virulence genes are only isolated from infected patients and clinical samples, whereas the majority of Enterococcus strains isolated from foodstufs have probiotic efects and health benefts [2]. In food storage, the application of bacteriocins of LAB as natural preservatives to control the growth of spoilage and pathogenic bacteria in food requires the safety confrmation of the producing strain and the understanding of its bacteriocin action mechanism against food-spoilage and pathogenic bacteria [8]. In previous works, a strain called FL31, isolated from fermented olives, was selected for its antimicrobial activity and identifed a new lactic acid bacteria designated Ente- rococcus faecium FL31. Te active compound of the strain FL31 was identifed as a proteinaceous substance and named BacFL31. Te N-terminal amino acid sequence of the purifed Hindawi BioMed Research International Volume 2018, Article ID 5308464, 10 pages https://doi.org/10.1155/2018/5308464