Biotechnological potential, probiotic and safety properties of newly isolated enterocin-producing Enterococcus lactis strains

Eight lactic acid bacterial (LAB) strains were newly isolated from fresh shrimps (Penaeus vannamei and Palaemon serratus) and characterised by phenotypic and molecular tests. These isolates, identified as Enterococcus lactis producing the enterocins A, B and/or P, displayed interesting antagonistic activities against pathogenic bacteria and fungi. Regarding biotechnological properties, E. lactis strains had generally great redox potentials, good proteolytic activities (P < 0.05) and medium acidification rates. Evaluated by the API ZYM system, two strains named Q1 and 4CP3 exhibited good enzymatic activities: leucine, valine and cystine arymalidases, Naphthol-AS-BI-phosphohydrolase and β-galactosidase. For probiotic assessment, the examined strains were found to resist low pH and bile salts with presence of gastric and digestive enzymes. Likewise, they indicated potentialities of adhesion and colonisation in the intestines. All strains were sensitive to clinically important antibiotics and no PCR signals were detected for any of the common antibiotic resistance genes such as vanA and vanB for vancomycin. Furthermore, virulence traits including the presence of virulence factors, haemolysin and gelatinase, were not detected. This work suggests that our E. lactis strains can be considered as promising candidates for future applications as a starter, adjunct or protective cultures or could constitute new potential probiotics.