Screening for Bacteriocins Producing Probiotic Bacteria from Fermented Sap of Palm Trees (Elaeis Guineesis and Raffia Sudanica): Production and Partial Characterization of Bacteriocins

Abstract

The spread of food spoilage microflora and food borne pathogenic bacteria are threat for food security and human health. The prolonged use of antibiotics or chemical preservatives to eradicate this microflora is disadvantageous because of the occurrence of resistant microbial strains. Bacteriocins from probiotic lactic acid bacteria currently appear as one of the best alternatives. Palm wine has been reported as rich source of lactic acid bacteria (LAB), however very few studies have been carried out on bacteriocin from palm wines isolates. This work aims at screening for bacteriocins producing lactic acid bacteria isolated from palm wines. LAB was isolated on de Man Rogosa and Sharpe agar using pour plating method. Bacteriocin activity was determined using cell free supernatant pretreated with 0.1M sodium hydroxide and catalase on Mueller Hinton Agar. LAB isolates were selected based on the capacity of their CFS to inhibit the growth of indicator microorganisms. The selected strains were identified phenotypically using API 5O CHL bioMerieux Kit and colony PCR was used to confirm the identity of the selected isolates. Three LAB isolates (IS6, IS9, IS13) were selected for their ability to produce bacteriocins with high antimicrobial activity (diameter of inhibition ≥20mm) against Esherichia coli, Salmonella enterica, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes. Inactivation of antimicrobial activity of CFS by proteolytic enzymes allowed confirming that they are bacteriocins. The selected LAB was identified as strain of Lactobacillus plantarum, Lactobacillus rhamnosus and lactobacillus brevis. The ability to significantly inhibit Listeria monocytogenes main cause of food spoilage at low temperature gives them the status of technological strains. In terms of their GRAS status and their probiotic potential, these strains may have interesting applications in agro-industries.