ABSTRACT The productions of nisin by Lactococcus lactis subsp. lactis CECT 539 and pediocin by Pediococcus acidilactici NRRL B-5627 were tested on cheap culture media from two important wastes: mussel processing wastes (MPW) and whey (W). Although both media supported the cell growth and bacteriocin production, the levels produced were lower than those obtained on MRS broth. The compositions of both the MPW and whey media were optimised using factorial experiments and empirical modelling, as a function of four factors: total sugars, nitrogen, phosphorous and buffer concentration. Nisin and pediocin productions were higher than those obtained in MRS broth when the whey and MPW media were supplemented with yeast extract or Casitone. Therefore, improvements in both nisin and pediocin productions on both media were attempted by converting the batch fermentation into a repeated re-alkalized fed-batch fermentation. The cultures of both bacteriocin-producing strains were characterised with high bacteriocin titres compared with the batch process on MRS, MPW and whey media. Mathematical models including the effects of the main variables affecting the cell growth and bacteriocin synthesis by both strains were set up to describe the effects of the main variables affecting the fed-batch production of biomass and bacteriocins by L. lactis and Ped. acidilactici. Nisin and pediocin obtained from the cultures on MRS broth showed the highest heat stability at acidic pH and short incubation times. However, the inhibitory activity of both bacteriocins disappeared almost totally after 90 min of treatment with proteolytic enzymes.
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