A New Strategy to Select Pediococcus pentosaceus Strains for the Application of Protective Cultures in Foods and Care Products

Pediococcus pentosaceus is a lactic acid bacterium used inter alia for fermentation of milk, meat, vegetables, fruits, and even beer. The resulting food products are tasty and safe. Furthermore, health-promoting effects such as anti-inflammation, anti-cancer, and detoxification have been attributed. Beside refining foods during the fermentation process, P. pentosaceus might be added to foods as a protective culture to improve food safety and extension of shelf-life, leaving the organoleptic properties of the food untouched. We have addressed the search for novel protective P. pediococcus strains by investigation of 38 isolates from milk samples and teat canal biofilms from dairy farms located in the vicinity of Muenster, Germany. P. pentosaceus strains were unequivocally identified by DNA sequencing of the gene encoding 16S rRNA. Binary matrices obtained from random amplification of polymorphic DNA experiments showed that all isolates differed and thus represent subspecies. The antibacterial profiles of 13 selected isolates showed that seven food pathogens and food spoilage bacteria could efficiently combat, although to various extends, gram-negative bacteria such as Pseudomonas aeruginosa or Salmonella enterica, and gram-positive bacteria such as Staphylococci and Listeria monocytogenes. Interestingly, acid production was dependent on the presence of the challenged pathogen but did not significantly correlate with the extend of inhibition. The genomes of three top-ranked isolates were sequenced. We found that the genome size and the harbored plasmids differed significantly, confirming the subtle genomic plasticity. One to two genes encoding bacteriocins could be detected in each of the three genomes. Our approach for protective culture screening demonstrates that it is worth to examine many isolates from a specific species to select the best performing strain for application in food and care products.