Antioxidant capacity, and probiotic properties of Enterococcus faecium strains isolated from raw milk of indigenous brown atlas cows.

In this work, we investigated the safety characteristics and probiotic proprieties of Enterococcus faecium (E. Faecium) strains isolated from raw milk of indigenous Brown Atlas cows reared in the Tafoughalt region (Berkane, Morocco). Eleven isolates were identified as E. faecium by 16S rRNA gene sequencing and subjected to an in-vitro evaluation approach including antibiotic susceptibility, safety related enzymatic activities, tolerance to gastrointestinal stress conditions, antioxidant capacity, and antibacterial activity against selected foodborne pathogens. All isolates were susceptible to clinically relevant antibiotics, such as ampicillin, vancomycin, gentamicin, tetracycline, and chloramphenicol, and none exhibited evidence of acquired or transferable antibiotic resistance. Safety assessment revealed the absence of haemolytic, DNase, and gelatinase activities in all strains. The isolates demonstrated marked tolerance to acidic conditions (pH 2.0-3.0) and bile salt concentrations (0.15%-0.30%), indicating their ability to survive simulated gastrointestinal environments. All strains inhibited the growth of Staphylococcus aureus ATCC 29213 in a strain and concentration dependent manner, while moderate inhibitory activity was observed against Escherichia coli ATCC 25922. Neutralisation and enzymatic treatments indicated that the antibacterial activity was primarily associated with organic acid production and, to a lesser extent, with proteinaceous compounds, suggesting the involvement of bacteriocin like substances. In addition, the isolates exhibited moderate, strain dependent antioxidant activity, ranging from approximately 15% to 27%. Among the evaluated strains, E. faecium EF89 displayed the most favourable combination of safety attributes and probiotic properties. Collectively, these results show that E. faecium strains isolated from Brown Atlas cow milk in Eastern Morocco are safe and promising candidates for use in functional foods and food biopreservation, supporting the valorisation of indigenous dairy resources.