Safety and biotechnological properties of Enterococcus faecalis and Enterococcus faecium isolates from Meju

We assessed the safety and biotechnological properties of 17 Enterococcus faecalis and 18 Enterococcus faecium strains isolated from Meju to select starter candidates for quality Meju production. Minimum inhibitory concentration assays showed that all strains were susceptible to ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, penicillin G, and tetracycline, as judged by the breakpoint values defined at the species level by the European Committee on Antimicrobial Susceptibility Testing, whereas two E. faecalis strains were resistant to vancomycin, which could be ascribed to acquired resistance. None of the strains exhibited α- or β-hemolytic activities or biofilm formation. Both species showed similar levels of biogenic amine production, and noticeable amounts of tyramine (3397.4 ± 172.4 ppm) were produced by all strains in the presence of precursors (histidine, lysine, ornithine, and tyrosine). All strains exhibited protease, lipase, and acid production, with decreased activity observed with increasing NaCl concentrations. This study confirmed the necessity of antibiotic resistance screening of Enterococcus species for food production, with the identification of vancomycin-resistant strains from Meju.