Characteristics of bacteriocin produced by Lactobacillus acidophilus LA-1

Abstract

A bacteriocin produced by L. acidophilus LA-1 (referred to as acidophilicin LA-1) was studied. Acidophilicin LA-1 was active against seven strains of Lactobacillus delbrueckii sp. bulgaricus (2501, 2505, 1515, 2517, 2519, LB-3 and LB-4), one strain each of L. easel (2603), L. helveticus (2700) and L. jugurti (2819), but not against other lactic acid bacteria. The production of bacteriocin occurred in MRS broth and MRS broth containing various sugars in place of glucose, but very little in milk or whey-based media. The bacteriocin showed activity over a wide range of temperature and pH. The production of bacteriocin increased on addition of β-glycerophosphate and was the highest at pH 5.5-6.0. The activity of acidophilicin LA-1 declined when the organism entered the death phase; however, its stability was better in fermentors upon supplementation with glucose or triple-strength MRS broth after 8 and 16 h growth. The molecular mass of the bacteriocin was ~ 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. delbrueckii sp. bulgaricus, L. helveticus, L. juqurti and L. casei produced heat-stable bacteriocin-like inhibitory substances.