Purification and Partial Characterization of Novel Bacteriocin L23 Produced by Lactobacillus fermentum L23

Abstract

Lactobacillus fermentum strain L23 produced a small bacteriocin, designated bacteriocin L23, with an estimated molecular mass of <7,000 Da. Isolation, purification, and partial characterization of bacteriocin L23 are described. It displayed a wide inhibitory spectrum including both Gram-negative and Gram-positive pathogenic strains, and two species of Candida. The antibacterial activity of cell-free culture supernatant fluid was not affected by catalase or urease, but was abolished by the proteolytic enzymes trypsin and protease VI. Bacteriocin L23 was heat-stable (60 min at 100ºC) and showed inhibitory activity over a wide pH range (4.0 to 7.0). The proteinaceous compound was isolated from cell-free culture supernatant fluid and purified. Crude bacteriocin sample was prepared by a process of ammonium sulfate precipitation, gel filtration, thin-layer chromatography (TLC), bioautography, and reversed-phase HPLC.