Lactobacillus curvatus UFV-NPAC1 and other lactic acid bacteria isolated from calabresa, a fermented meat product, present high bacteriocinogenic activity against Listeria monocytogenes

Abstract

Background: Bacteriocins produced by lactic acid bacteria (LAB) can be considered as viable alternatives for food safety and quality, once these peptides present antimicrobial activity against foodborne pathogens and spoilage bacteria. Fermented foods, such as artisanal sausages and cured meats, are relevant sources of LAB strains capable of producing novel bacteriocins, with particular interest by the food industry.

Results: Three LAB strains (firstly named as Lactobacillus curvatus 12, L. curvatus 36 and Weissella viridescens 23) were obtained from calabresa by presenting promising bacteriocinogenic activity, distinct genetic profiles (rep-PCR, RAPD, bacteriocin-related genes) and wide inhibitory spectrum. Among these strains, L. curvatus 12 presented higher bacteriocin production, reaching 25,000 AU/mL after incubation at 25, 30 and 37 °C and 6, 9 and 12 h. Partially purified bacteriocins from L. curvatus 12 kept their inhibitory activity after elution with isopropanol at 60% (v/v). Bacteriocins produced by this strain were purified by HPLC and sequenced, resulting in four peptides with 3102.79, 2631.40, 1967.06 and 2588.31 Da, without homology to known bacteriocins.

Conclusions: LAB isolates obtained from calabresa presented high inhibitory activity. Among these isolates, bacteriocins produced by L. curvatus 12, now named as L. curvatus UFV-NPAC1, presented the highest inhibitory performance and the purification procedures revealed four peptides with sequences not described for bacteriocins to date.

Keywords: Bacteriocin; Calabresa; Lactic acid bacteria; Lactobacillus curvatus; Listeria monocytogenes.

Fig. 1

Growth (optical density at λ = 600 nm) and inhibitory activity (arbitrary units per mL) of Lactobacillus curvatus 12 (a, b, c), L. curvatus 36 (d, e, f) and Weissella viridescens 23 (g, h, i) cultivated in MRS broth and incubated at 25 (a, d, g), 30 (B, E, H) and 37 °C (c, f, i)

Fig. 2

Growth curves of Listeria monocytogenes 72 inoculated in brain heart infusion and incubated at 37 °C for 12 h, and added with cell free supernatant (CFS) of bacteriocinogenic lactic acid bacteria strains at 3 h of incubation (arrow). Control (●), adding of Lactobacillus curvatus 12 CFS (▲), L. curvatus 36 CFS (×) and Weissella viridescens 23 CFS (■)

Fig. 3

Chromatogram of the purified bacteriocins produced by Lactobacillus curvatus 12 (C4 reversed-phase HPLC). Asterisk indicates the peak with inhibitory activity against L. monocytogenes 72, with retention time of 56.27 min

Fig. 4

Predicted structures of four peptides produced by Lactobacillus curvatus 12 (C4 reversed-phase HPLC) designed using Pepfold3 (http://bioserv.rpbs.univ-paris-diderot.fr)