Partial characterization of bacteriocins produced by three strains of Lactobacillus sakei, isolated from salpicao, a fermented meat product from North-West of Portugal

Abstract

Lactobacillus sakei ST22Ch, ST153Ch and ST154Ch were isolated from traditional pork product from Northwest of Portugal, and identified based on API50CHL, PCR with specific primers and 16s rDNA sequencing. RAPD-PCR analysis showed significant differences between isolates. The selected isolates inhibited the growth of Enterococcus spp., Listeria spp., Escherichia coli, Klebsiella spp., Pseudomonas spp., Staphylococcus spp., and Streptococcus spp. The mode of action of the bacteriocins was bactericidal, as observed against Enterococcus faecium. A reduction in antimicrobial activity was recorded after treatment of the bacteriocins with proteolytic enzymes, but not when they were exposed in presence of α-amylase, suggesting that they are not glycosylated. Maximal activity of bacteriocins was recorded during the early stationary phase and remained stable only for a short period, followed by a decrease. According to tricine/SDS-PAGE, the size of bacteriocins ST22Ch, ST153Ch and ST154Ch are approximately 3.0 kDa, 10.0 kDa and 3.0 kDa, respectively. Bacteriocins were heat tolerant and remained active after 2 h at 100 °C. Activity of bacteriocins was not affected by treatment with 1% Triton X-100, Tween 20, Tween 80, SDS, NaCl, urea and EDTA. In presence of 1% Triton X-114 bacteriocins were inactivated. PCR reactions targeting genes for enterocin A, enterocin P, sakacin P, sakacin G1 and sakacin G2 in the total DNA of L. sakei ST22Ch, ST153Ch and ST154Ch, generated positive results. Curvacin A gene was detected only in L. sakei ST154Ch DNA.