Modelling the stress inducing biphasic growth and pediocin production by Pediococcus acidilactici NRRL B-5627 in re-alkalized fed-batch cultures

Five re-alkalized fed-batch cultures of Pediococcus acidilactici NRRL B-5627 were carried out in culture media prepared with mussel processing wastes (MPWs) and whey under different fermentation conditions. The shift from homolactic to mixed acid product formation and the biphasic kinetics observed for cell growth, nitrogen consumption and pediocin production were the most noteworthy observations of these cultures. For a better understanding of the culture dynamics and for a suitable description of the bacteriocin production system, an unstructured mathematical model based on the two phases of nitrogen consumption was developed. The model was expressed in terms of biomass, product accumulation and substrate utilization. Excellent agreements between model predictions and experimental data were achieved in the five re-alkalized fed-batch cultures and a reasonable description for each parameter in each growth phase was provided by the model. Using published experimental data by other researchers, model agreement was also found for the growth of Ped. acidilactici NRRL B-5627 in a repeatedly re-alkalized culture in a synthetic culture medium. The developed model appears to be useful for the design, scale-up, control and optimization of the production of potentially probiotic cultures and bacteriocins.