Production of enterocin A by Enterococcus faecium MMRA isolated from 'Rayeb', a traditional Tunisian dairy beverage.
OBJECTIVE
Characterization and purification of a bacteriocin produced by a wild Enterococcus faecium strain, isolated from a Tunisian traditional fermented milk.


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 degrees 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 degrees 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.


CONCLUSIONS
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.
Faculté des Sciences de Tunis, Département de Biologie, Laboratoire de Biochimie et Biologie Moléculaire, Campus Universitaire, Tunis, Tunisie.
A
A
Rehaiem
B
B
Martínez
M
M
Manai
A
A
Rodríguez
D000818:Animals; D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D001430:Bacteriocins / Q000096:biosynthesis* / Q000302:isolation & purification / Q000494:pharmacology; D043302:Cultured Milk Products / Q000382:microbiology*; D004591:Electrophoresis, Polyacrylamide Gel; D016984:Enterococcus faecium / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D005516:Food Microbiology; D014416:Tunisia
D000900:Anti-Bacterial Agents; D001430:Bacteriocins; C107799:enterocin A