Broad spectrum antibacterial activity of Pediococcus damnosus and Pediococcus pentosaceus in minced meat

Three Pediococcus strains producing bacteriocin-like inhibitors were tested for their antibacterial effects. The study was carried out in minced meat inoculated with four test organisms,Yersinia enterocolitica, Listeria monocytogenes or Pseudomonas fragi and Pseudomonas fluorescens. The inoculation levels of pediococci varied within a range of 10³–10⁸ cfu g⁻¹, whereas the number of test organisms inoculated was approximately constant at 10² cfu g⁻¹. In order to enhance the bacteriocin production of pediococci, the inoculated samples were first kept at 15°C for 2 days, thereafter they were stored at 6°C. The growth of test organisms was followed at 2 or 3-day intervals for 2 weeks. The results showed that all strains of pediococci inhibited the growth of test organisms at the highest inoculation level, lower levels did not have any effect on the growth of test organisms. In parallel, the experiments were carried out by replacing the viable Pediococcus cells by a cell-free crude extract of inhibitors isolated from the growth medium of pediococci. The extracts showed a strong inhibition potential against all test organisms. The pH values of the samples did not significantly decrease during the storage period. The results showed evidence that selected strains of pediococci have a broad spectrum antibacterial potential in a food matrix due to inhibition of Gram-negative organisms.