Published on July 2013 | Microbiology

Isolation and Partially Characterization of Bacteriocin Produced by Lactic Acid Bacteria Isolated from Barley Beer

Twenty lactic acid bacteria (LAB) were isolated from barley beer, six of these beer isolates were observed to secrete the inhibitory compounds into the cellfree filtrate with optimal production occurring in the late exponential growth phase. The inhibitory spectra of these isolates included various Gram’s positive and Gram’s negative bacteria and a variety of beer-spoiling bacteria. Based on standard biochemical and microbiological tests, these isolates were tentatively identified as Lactococcus lactis subsp. lactis, Lactobacillus sakei, Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus paracasei. These inhibitory isolates were inactivated by treatment with proteolytic enzymes indication that the inhibitory compound was proteinaceous in nature, the proteinaceous nature and inactivation by catalase identified them as bacteriocins. These bacteriocins were partially characterized. Bacteriocins produced by these six isolates were active across a wide pH range, relatively insensitive to heat treatment. Stability of the secreted bacteriocins at varying pH values indicated that full activity was retained in all samples at pH 4-6 with a significant reduction in activity at pH 2-3 and pH 7-10.