Isolation and preliminary characterisation of bacteriocin produced by Enterococcus faecium GHB21 isolated from Algerian paste of dates “ghars”

Abstract

The bacteriocin-producing strain GHB21 isolated from the Algerian traditional paste of dates “ghars” was identified as Enterococcus faecium based on 16S rRNA sequence analysis. The bacteriocin produced by Enterococcus faecium GHB21 was sensitive to proteases, heat-stable, resistant to a wide range of pH and also to several chemicals. Recorded bacteriocin activity was higher when GHB21 was fermented in a bioreactor compared with static fermentation in a flask; it was also shown to be growth-associated and to display primary metabolite kinetics as its maximal production was detected in the early logarithmic growth phase. GHB21 presented a large activity spectrum towards different genera, and proved active against either Gram positive or Gram negative bacteria, including some pathogenic and/or spoilage bacteria. Partial purification of this bacteriocin by an adsorption-desorption method led to a fraction that lost its entire activity after 1 week of storage at 4 °C, or after 15 days when supplemented with bovine serum albumin; nevertheless the lyophilised fraction could remain stable with full activity even after 1 year. The partially purified bacteriocin exhibited a bactericidal effect on Listeria ivanovii subsp. ivanovii ATCC 19119 and could lead to its total inhibition after only 6 h but without concomitant cell lysis. Tricine-SDS-PAGE analysis of the partially purified bacteriocin indicated a low molecular weight of approximately 5 kDa.