Characterization of bacterocin-like substances produced by two local Lactobacillus paracasei subsp. paracasei strains

Document Type : Research articles.

Authors

Department of Agricultural Microbiology, Faculty of Agriculture, Fayoum University

Abstract

The increasing consumer awareness of the risks derived not only from
food borne pathogens, but also from the artificial chemical preservatives
used to control them, has led to an increased interest in food -grade
preservatives of biological origin. In this respect, special interest has been
focused on the antimicrobial bacteriocins and the lactic acid bacteria
producing them which are considered safe biopreservatives. In the present
study, sixty nine lactobacillus strains isolated from retail samples of local
foods and dairy products were screened for bacteriocin production
Of the 47 Lactobacillus isolates found to be bacteriocin-like
substances producers, five best strains which showed the strongest
antibacterial activity against E.coli; Listeria monocytogenes; Bacillus
cereus; Salmonella enteritides; and Staphylococcus aureus, were selected
and identified, among these isolates, two were found belong to Lb.
paracasei subsp. paracasei. The bacteriocin-like substances (BLS)
produced by these strains were tested for characteristics that could
determine their usefulness as food biopreservatives. The two BLS retained
most of their bacterial activity even after autoclaving and after extended
refrigerated and freezing storage, as well as after exposure to organic
solvents or surfactants, and they remained functional over a wide pH rang
of 3.0 to 12.0 and tolerated up to 20.0% sodium chloride. In addition they
exhibited broad antimicrobial spectra against not only G+ bacteria but also
against G- bacteria and yeasts. These results suggest that BLS produced by
two local Lactobacillus strains has an application potential as food
biopreservatives, and may be used as alternatives or complimentary for
antibiotics.

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