Effect of medium components on bacteriocin production by Lactobacillus plantarum strains ST23LD and ST341LD, isolated from spoiled olive brine

Summary Bacteriocin ST23LD levels of 2930 AU/OD were recorded in MRS broth (pH of 6.5) and in the presence of tryptone and yeast extract as sole nitrogen sources. Growth in MRS broth at an initial pH of 6.0 yielded only 1460 AU/OD bacteriocin ST23LD. Activities of 5861 AU/OD were recorded with maltose (20, 30 and 40 g/l) as sole carbon source and 9036 AU/OD with the addition of 2.0–10.0 g/l KH 2 PO 4 . Bacteriocin ST341LD levels of 2850 and 2841 AU/OD were recorded in MRS broth at an initial pH of 6.0 or 5.5, respectively. Only 709 AU/OD was recorded in the same medium with an initial pH of 6.5. Bacteriocin ST341LD production was stimulated by the presence of tryptone. However, glucose at 10 and 40 g/l, or the presence of 5.0 or 10.0 g/l K 2 HPO 4 , resulted in a 50% reduction of bacteriocin activity. Glycerol in the growth medium repressed bacteriocin production. No increased bacteriocin production was recorded in medium supplemented with vitamins.