CHARACTERISTICS OF BACTERIOCIN PRODUCED BY LACTOBACILLUS-ACIDOPHILUS LA-1

A bacteriocin produced by L. acidophilus LA-1 (referred to as acidophi licin LA-1) was studied. Acidophilicin LA-1 was active against seven s trains of Lactobacillus delbrueckii sp. bulgaricus (2501, 2505, 1515, 2517, 2519, LB-3 and LB-4), one strain each of L. casei (2603), L. hel veticus (2700) and L. jugurti (2819), but not against other lactic aci d bacteria. The production of bacteriocin occurred in MRS broth and MR S broth containing various sugars in place of glucose, but very little in milk or whey-based media. The bacteriocin showed activity over a w ide range of temperature and pH. The production of bacteriocin increas ed on addition of beta-glycerophosphate and was the highest at pH 5.5- 6.0. The activity of acidophilicin LA-1 declined when the organism ent ered the death phase; however, its stability was better in fermenters upon supplementation with glucose or triple-strength MRS broth after 8 and 16 h growth. The molecular mass of the bacteriocin was similar to 50,000 Da. The bacteriocin was successfully purified using two-stage fractionation with ammonium sulfate. Fifteen of 19 additional strains of L. acidophilus tested for antimicrobial activity against L. delbrue ckii sp. bulgaricus, L. helveticsu, L. jugurti and L. casei produced h eat-stable bacteriocin-like inhibitory substances. (C) 1998 Elsevier S cience Ltd. All rights reserved.