The influence of pH and growth rate on production of the bacteriocin, bavaricin MN, in batch and continuous fermentations

Bavaricin MN, a bacteriocin produced by Lactobacillus bavaricus MN, reached titres of 2000 AU ml ‐1 in APT broth maintained at pH 6.0, 30°C in a batch fermenter. Levels of bavaricin MN at pH 5.5 and 6.5 were lower despite comparable levels of producer cells. The addition of 3.0 g l ‐1 beef extract to APT broth resulted in increases in both the growth rate of the culture and the production of bavaracin MN. The titre of bavaricin MN in batch fermenters controlled at pH 6.0 in APT broth plus 3 g l ‐1 beef extract reached 3200 AU ml ‐1 at 30°C. This level was reduced to 800 AU ml ‐1 by 76 h. Glucose‐limited continuous culture of Lact. bavaricus MN under the same conditions resulted in an increase in the titre of bavaricin MN to 6400 AU ml ‐1 . This level was maintained, independent of growth rate, for 345 h. Growth rates of 0.205, 0.118, 0.169 and 0.058 h ‐1 were examined.