Abstract
Strain Enterococcus sp. GHB26, isolated from the Algerian paste of dates Ghars, produced a bacteriocin. This bacteriocin was inactivated by proteolytic enzymes. Antibacterial activity of the bacteriocin was heat stable at 120°C for 20 min (533 AU/ml), stable at pH range of 2 to 12 and resistant to chemicals (SDS, EDTA, NaCl, Tween 80, Urea). The active bacteriocin from the cell-free supernatant of Enterococcus sp. GHB26 was purified by precipitation with ammonium sulfate followed by various combinations of gel filtration on a Sephadex G-25 column, cation exchange chromatography on a CM- Sephadex Cellulose column and reverse phase-high performance liquid chromatography on a C18 column. The bacteriocin was eluted as a single peak on the chromatogram from reverse phase-high performance liquid chromatography attesting the purity of this bacteriocin. The bacteriocin exhibited a bactericidal mode of action. Sodium dodecyl sulphate - polyacrylamide gel electrophoresis indicated that molecular weight of this bacteriocin is close to 3.5 kDa. Key words: Paste of dates, bacteriocin, antibacterial activity, chromatography, mode of action.
Highlights
Lactic acid bacteria had largely been exploited in the food fermentation and they display numerous antimicrobial activities (De Vuyst and Leroy, 2007; Šušković et al, 2010)
This antibacterial activity was recorded on buffered MRS broth with a maximum activity level of 1066 arbitrary units per mililiter (AU/ml), which excludes the possible effect of lactic acid
The antibacterial activity of the cell-free supernatant was sensitive to proteolytic enzymes, except pepsin, which indicated the proteinaceous nature of the active substance
Summary
Lactic acid bacteria had largely been exploited in the food fermentation and they display numerous antimicrobial activities (De Vuyst and Leroy, 2007; Šušković et al, 2010). Mostly enterococci strains, are found in the gastrointestinal tracts of humans and animals and are considered to exert healthpromoting effects which include antimicrobial activity against pathogen strains. This is mainly due to the production of organic acids, diacetyl, hydrogen peroxide and acetaldehyde and of other compounds, such as bacteriocins (Gürakan, 2007). The bacteriocins are often cationic and amphiphilic or hydrophobic (Altuntas, 2013). The enterococcal bacteriocins are small heat stable proteins that kill closely related bacteria (Altuntas, 2013)
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