Purification and characterization of bacteriocin F1, a novel bacteriocin produced by Lactobacillus paracasei subsp tolerans FX-6 from Tibetan kefir, a traditional fermented milk from Tibet, China

A bacteriocin-producing lactic acid bacteria, FX-6, was isolated from Tibetan kefir using the agar well diffusion assay. Strain FX-6 was identified as Lactobacillus paracasei subsp. tolerans on the basis of 16S rDNA sequence analyses. This bacteriocin, which was designated bacteriocin Fl, was purified by a threestep purification procedure. The molecular mass of bacteriocin Fl was 2113.842 Da by MALDI-TOF MS analyses. It was also discovered to have blocked N-termini, hampering analysis by Edman degradation. Bacteriocin Fl exhibited a wide range of antimicrobial activity, strong heat stability (20minat 121 C, or 60 min at 100 degrees C) and pH stability (pH 3.0-9.0). Following treatment by pepsin and trypsin, the antibacterial activity was partly reduced. Bacteriocin Fl is the first reported bacteriocin produed by L paracasei subsp. tolerans which can not only inhibit fungi but also bacteria. The characterization of bacteriocin Fl suggested that it was a novel bacteriocin with potential research and application value in food industry. (C) 2014 Elsevier Ltd. All rights reserved.