Dynamic mathematical models to describe the growth and nisin production by Lactococcus lactis subsp. lactis CECT 539 in both batch and re-alkalized fed-batch cultures

The growth and bacteriocin production by Lactococcus lactis subsp. lactis CECT 539 was studied in batch and in re-alkalized fed-batch fermentations in media prepared with whey and mussel-processing wastes. From these cultures, mathematical models were developed to describe the growth and nisin production. The growth model developed which was based on Monod kinetics, has clearly more mechanistic approach and provides a major biological interpretability of the parameters than the logistic growth equation. This is the first study presenting a pseudomechanistic model to describe the growth kinetics of lactic acid bacteria in re-alkalized fed-batch fermentations. Nisin production was modeled with a modified form of the Luedeking and Piret model, which includes a term for the effect of the optimal final pH value in bacteriocin synthesis. Both models were demonstrated for three fed-batch cultivations of L. lactis using different culture media, feeding substrates and times of re-alkalization and feeding.