Production of nisin with continuous adsorption to Amberlite XAD-4 resin using Lactococcus lactis N8 and L. lactis LAC48.

The production of nisin, biomass and lactic acid in pH-controlled and uncontrolled batch fermentation and batch fermentation (pH 5.5) with continuous removal of nisin was examined in the parent strain Lactococcus lactis N8 and LAC48. Strain LAC48 in batch fermentor (pH not controlled) gave a maximum nisin concentration of 2.5 x 10(6) IU g dcw(-1). The nisin concentration remained high (2.0 x 10(6) IU g dcw(-1)) after the logarithmic growth phase (10-22 h), whereas nisin production of strain N8 decreased after the logarithmic growth phase. The maximum nisin production of strain LAC48 was not directly related to the biomass formation and not associated with growth. In order to study end product inhibition in nisin production, a system was built for adsorption of nisin during fermentation. The adsorbent Amberlite XAD-4 was found to have an effective binding capacity for nisin. Cells of LAC48 and N8 compensated for the removal of nisin, indicating that nisin production also occurs in the stationary phase.