Production of enterocin A byEnterococcus faeciumMMRA isolated from ‘Rayeb’, a traditional Tunisian dairy beverage

Abstract

Aims: Characterization and purification of a bacteriocin produced by a wild Enterococcus faecium strain, isolated from a Tunisian traditional fermented milk. Methods and Results: Enterococcus faecium MMRA was selected on the basis of its strong anti‐Listeria activity. The antibacterial activity was sensitive to proteases, confirming its proteinaceous nature. It was extremely heat stable (15 min at 121°C), remained active over a wide pH range (2–12), and also after treatment with lipase, amylase, organic solvents, detergents, lyophilisation and long‐term storage at −20°C. Production of the bacteriocin occurred throughout the logarithmic growth phase, it did not adhere to the surface of the producer cells and the mode of action was bactericidal. After partial purification of the active supernatants, a 4‐kDa band with antibacterial activity was revealed by SDS‐PAGE electrophoresis and bioassay. Tryptic digestion followed by MALDI‐TOF mass spectrometry identified the peptide as enterocin A. Conclusions: The inhibitory activity of Ent. faecium MMRA, a wild strain isolated from the artisan dairy beverage ‘Rayeb’, is due to the synthesis of an enterocin A. Significance and Impact of the Study: Traditional fresh Tunisian fermented dairy products are generally manufactured with raw milk that can be used as a source of uncharacterized wild lactic acid bacteria strains. To our knowledge, this is the first report on the isolation of an enterocin A producing Ent. faecium from ‘Rayeb’. This bacteriocin or the producing strain might have a promising potential in biopreservation to enhance the hygienic quality of this dairy product.

Genetic Diversity and Some Aspects of Antimicrobial Activity of Lactic Acid Bacteria Isolated from Goat Milk

“…and Enterococcus spp. [14,30,53]. Nisin usually retains its antimicrobial activity when exposed to a variety of pH levels and is capable of displaying the highest inhibitory activity at low pH; when the pH is lowered, the solubility and stability of nisin tend to increase [11,17,19,22,42,12].…”

Probiotic properties of Enterococcus faecium CE5-1 producing a bacteriocin-like substance and its antagonistic effect against antibiotic-resistant enterococci in vitro

“…That no activity was shown against Gram-negative bacteria may be due to the relative impermeability of their outer membranes (Jack et al, 1995). Rehaiem et al (2009) reported that CS of Ent. faecium MMRA could inhibit Lactobacillus, Leuconostoc, Enterococcus, and Listeria species, but there was no inhibition of Gram-negative bacteria, Hafnia, Serratia, and E. coli.…”

“…A decrease in the bacteriocin activity has also been observed for bacteriocins produced by Ent. faecium MMRA (Rehaiem et al, 2009), Leuconostoc mesenteroides E131 (Xiraphi et al, 2008), and Lb. acidophilus (Karthikeyan and Santhosh, 2009).…”

“…Ent. faecium MMRA supernatant reduced L. ivanovii BUG 496 at 60 AU/ml (Rehaiem et al, 2009). In the same way, the number of cells of L. innocua LMG 13568 decreased from 4.8 × 10 3 CFU/ml to 2.0 × 10 2 CFU/ml for 32 h in a co-culture of Ent.…”

Effectiveness of convective drying to conserve indigenous yeasts with high volatile profile isolated from algerian fermented raw bovine milk (Rayeb)

“…Rayeb, produced by spontaneous fermentation of raw milk at ambient temperature for a period of 24 h to 72 h, has nutritional benefits and plays an important role in the population diet, particularly those of rural population (Idoui et al, 2010). Mixed species of lactic acid bacteria (LAB), Leuconostoc, enterococci, yeasts, especially species of the genera Saccharomyces and Candida as well as moulds are responsible of spontaneous fermentation (Rehaiem et al, 2010). Dwing to their proteolytic and lipolytic activities, yeasts represent a significant part in flavoring properties by producing volatile compounds and inducing organoleptic characteristics of Mediterranean areas-fermented milk .…”