A new bacteriocin- like-inhibitory substance from Egyptian dairy products isolated from Enterococcus faecium with anti-SARS-CoV-2 activity

Bacteriocins generated by lactic acid bacteria have increased in popularity due to their safety and versatility of application. Dairy products are rich sources of lactic acid bacteria. This work screened 31 Egyptian dairy product isolates for antimicrobial activity. Two bacteriocinogenic isolates, Enterococcus faecium CH019 and Enterococcus faecium CM019, were identified using molecular techniques. The production conditions of Bacteriocin-like inhibitory substances (BLIS) were optimized. The physical and chemical properties of the Enterococcus faecium CM019 bacteriocin-like compound were analyzed. Cytotoxic and antiviral properties against SARS-CoV-2 were evaluated. Enterococcus faecium CM019 produces bacteriocin-like substances most effectively in MRS broth with a pH of 6.5 and incubation temperature of 35 degrees C for 24 h. In the presence of surfactant, solvent, and high temperature, the bacteriocin-like substance activity was persistent, but it was eliminated by proteinase K, trypsin, and lipase. The BLIS proved effective against Listeria monocytogenes and Staphylococcus aureus. The CC50 of the bacteriocin-like compound was 108.3 mu g/ml, while the IC50 against SARS-CoV-2 was 22.9 mu g/ml. With an acceptable toxicity limit, BLIS generated by Enterococcus faecium CM019 isolated from Egyptian dairy products has a broad antimicrobial spectrum and can be employed as an antibacterial agent against Gram-positive bacteria and anti-SARS-CoV-2.