Simultaneous Production of Formylated and Nonformylated Enterocins L50A and L50B as well as 61A, a New Glycosylated Durancin, by Enterococcus durans 61A, a Strain Isolated from Artisanal Fermented Milk in Tunisia

Enterococcus durans 61A, a broad-spectrum strain, was isolated from artisanal fermented dairy products. The strain is a multibacteriocin producer, free from virulence genes, and could be considered a good candidate for application in food preservation. In the present study, E. durans 61A was shown to produce simultaneously formylated and nonformylated forms of leaderless enterocins L50A and L50B as well as 61A, a new glycosylated durancin. Bacteriocins were characterized using mass spectrometry. Formylation was found to increase enterocin antimicrobial activity of enterocin L50A (8X) and, to a lesser extent, the activity of L50B (2X). Durancin 61A was found glycosylated by two hexoses (glucose and arabinose) and exhibited broadspectrum inhibition against Gram-positive and Gram-negative bacteria and fungal spores. Durancin 61A was highly bactericidal at 15.6,ug/mL (10X the MIC) on Listeria innocua HPB13 and seems to target bacterial membrane as shown by ion efflux and transmission electron microscopy.