Bio-preservative Activities of Partially Purified Bacteriocin Extracts of Lactobacillus mindensis TMW and Lactobacillus tucceti CECT 5920 Isolated from Nigerian Fermented Foods

Abstract

The preservative potentials of lactic acid bacteria (LAB) recovered from some Nigerian traditional fermented foods were assessed by inoculating 0.1 ml aliquots of suitable dilutions of the food samples on De Man Rogosa Sharpe (MRS) agar fortified with 50mg of nystatin. The isolates were assessed for their ability to produce bacteriocin using Agar Well Diffusion assay method.  By using (GTG)5-PCR and 16s rDNA sequencing tools, two bacteriocin-producing LAB namely Lactobacillus tucceti CECT 5920 and Lactobacillus mindensis TMW were identified. Both LAB isolates had equal level of bacteriocin activity. Studies on inhibitory activity of partially purified bacteriocin extracts showed that temperature of 35°C had maximum effect on bacteriocin antimicrobial activity of L. tucceti CECT 5920 against Staphylococcus aureus NCTC 8325 and Escherichia coli 0157:H7, while pH had same effects on both LAB isolates against the test bacteria. Maximum tolerance of acidic medium was exhibited by both LAB isolates at pH 3-8.  Bacteriocin inhibitory activity was best against both test bacteria at 0.2% concentration of NaCl. Combination of ginger with partially purified bacteriocin sample from both LAB isolates had reduction effect on both test pathogens for both Lactic acid bacteria isolates. When stored for 14 days, bacteriocin activity was optimum for the first day against both test pathogens, but decreased progressively with increased in storage time. The two LAB isolates had similar inhibitory activity against both test pathogens. L. tucceti CECT 5920 gave greater reduction result (90.03%) on S. aureus NCTC 8325 in fish sample and 78.07% against E. coli 0157:H7 in meat sample while L mindensis TMW had highest significant reduction effect (90.12%) in fish sample against S. aureus NCTC 8325 and 77.80% against E. coli 0157:H7 in fish sample. Both LAB isolates will perform well as preservative agents in food preservation as they showed production of bacteriocin which has antimicrobial activity and rapid acidification in growth medium.