초록
<P><B>Highlights</B></P><P>► Enterocin A synthesis was assayed in MRS broth in batch and fed-batch fermentations. ► The realkalized fed-batch fermentation technique enhanced enterocin A synthesis. ► The enterocin A production system in this culture was satisfactorily modelled. ► This bacteriocin was classified as a primary metabolite dependent on the pH drop. ► Bacteriocin stability was high around 84°C, at low pH, and short incubation times.</P> <P><B>Abstract</B></P><P>The growth, nutrient (total sugars, phosphorous, nitrogen and proteins) consumption and product formation by <I>Enterococcus faecium</I> MMRA in de Man, Rogosa and Sharpe (MRS) broth was followed in non-realkalized batch, realkalized batch and realkalized fed-batch cultures. In the latter fermentation, the growing culture was fed with a mixture of MRS medium (20g of glucose/L) and a 400g/L concentrated glucose. In the three cultures, a typically homolactic fermentation (only lactic acid was produced) was observed. The realkalized fed-batch culture was mainly characterized with higher biomass (2.4g/L), lactic acid (32.5g/L) and enterocin A (35.9AU/mL) concentrations compared with the two batch processes.</P><P>Mathematical models were developed to describe the productions of biomass, enterocin A and lactic acid in the two realkalized cultures. The growth and lactic acid production were successfully modelled with the Monod and the Luedeking and Piret models, respectively. Enterocin A was modelled by using a modified form of the Luedeking and Piret model, which includes a term for the effect of the pH drop rate on bacteriocin synthesis. Furthermore, the maximum enterocin A stability was obtained at temperatures below 100°C, at acidic pH values and short incubation times.</P>