Evaluation of antibacterial properties of lactic acid bacteria from traditionally and industrially produced fermented sausages from Germany
With regards to the frequently reported findings of spoilage bacteria and pathogens in various foods there is a need to explore new ways to control hazards in food production and to improve consumer safety. Fermented sausages from traditional and industrial production in Germany were screened for lactic acid bacteria with antibacterial effects towards important foodborne pathogens (Escherichia coli DSM 1103, Listeria innocua DSM 20649, Listeria monocytogenes DSM 19094, Pseudomonas aeruginosa DSM 939, Staphylococcus aureus DSM 799 and Salmonella Typhimurium DSM 19587). The obtained isolates and their cell-free supernatants were tested for their antibacterial activity by agar well diffusion assay. Isolates with an inhibitory effect were examined for the underlying antibacterial mechanism. Among the 169 collected isolates, 12.4% showed antibacterial effects only against Listeria innocua DSM 20649 and Listeria monocytogenes DSM 19094. In 6.5% of the isolates, bacteriocins were responsible for the effect. On the remaining test strains, the lactic bacteria isolates exerted no antibacterial effect. Two isolates were selected based on their antibacterial potential against Listeria spp. and the thermostability of the deriving cell free supernatants, traditional product: Pediococcus pentosaceus LMQS 331.3, industrial product: Pediococcus acidilactici LMQS 154.1, were investigated further and confirmed for the presence of bacteriocin structural genes by real-time PCR. Enriched crude bacteriocin preparations were obtained by ammonium sulfate precipitation and were found to remain stable under different pH milieus and to be active towards an extended set of Listeria spp. strains. Fermented meat products from German production are a promising source for bacteriocin-producing lactic acid bacteria. Two bacteriocin-producing isolates were identified which have the potential to contribute to product and consumer safety.