Enhanced nisin production by increasing genes involved in nisin Z biosynthesis in Lactococcus lactis subsp. lactis A164

Nisin Z production in Lactococcus lactis subsp. lactis A164 was improved by introducing multicopy genes, nisZ, nisRK, or nisFEG, involved in nisin biosynthesis into A164 strain. A similar growth profile was obtained from all strains tested. However, the cells expressing nisRK produced 25,000 AU nisin Z ml^-1 compared to 16,000 AU ml^-1 by the control strain. Northern blot analysis revealed that over-expression of nisRK promoted the transcription of the nisZ gene. The A164 strain expressing multicopy nisFEG also had an increased nisin Z production (25,000 AU ml ^-1) but produced the nisin more slowly than the cells expressing multicopy nisRK.