Characterization of anti-Listeria bacteriocins isolated from shellfish: Potential antimicrobials to control non-fermented seafood

Abstract

This work had as main objectives to characterize two bacteriocins produced by lactic acid bacteria (LAB) previously isolated from non-fermented seafood, in order to evaluate their potential as new food protective agents. The two bacteriocinogenic isolates were identified by Polymerase Chain Reaction (PCR) using genus- and species-specific primers, and confirmed by 16S rDNA sequencing, as Enterococcus faecium and Pediococcus pentosaceus. The antimicrobial spectrum of each strain included several indicator microorganisms, some of them also isolated from seafood. Growth of Listeria innocua, L. monocytogenes, Staphylococcus aureus, Bacillus cereus and other LAB species were inhibited, although no inhibition of Gram-negative microorganisms was observed. Proteolytic, but not lipolytic or glycolytic enzymes, completely inactivated the antimicrobial effect of both cell-free supernatants confirming the proteinaceous nature of the inhibitors. The antimicrobial activity was maintained after treatment with NaCl, SDS, Triton X-100, Tween 20, Tween 80 and EDTA after 2 h or 5 h of exposure and both bacteriocins were stable over a wide range of pH and temperatures. Production of bacteriocin by E. faecium (bacALP7) was detected initially at exponential phase and reached a maximum activity of 25,600 AU/ml in the early stationary phase, whereas bacteriocin production by P. pentosaceus ALP57 (bacALP57) reached the maximum at exponential phase with 12,800 AU/ml. The bacteriocins did not kill L. monocytogenes ESB54 nor L. innocua 2030c however, cellular growth was reduced. The partially purified bacteriocins, bacALP7 and bacALP57, were below 6.5 kDa in size as determined by Tricine-SDS gel electrophoresis. E. faecium and P. pentosaceus contained DNA fragments corresponding in size to those recorded for enterocin B and pediocin PA-1, respectively. Sequencing of the fragments from both bacteriocins confirmed the homology. To our knowledge, for the first time two LAB producing bacteriocins similar to pediocin PA-1 and enterocin B, were isolated from non-fermented shellfish. The adaptation of the cultures to seafood matrices may be advantageous in terms of application as a biopreservation strategy for reduction of L. monocytogenes levels in seafood products.

Antagonistic Activity, Antimicrobial Susceptibility and Potential Virulence Factors of Enterococcus faecalis

“…Bacteriocin production in isolates from seafood was reported by Valenzuela et al [9] and Pinto et al [24].…”

“…The bacteriocin described in the study by Pinto et al [24] partially lost activity after treatment at different temperatures (90-120 °C).…”

“…Inhibitory activity remained at 76% (13/22) even after passing through treatments with proteolytic enzymes and pH (7.0) neutralization. Based on the results, the nature of inhibitory compound produced cannot be stated, because the characteristics are atypical when compared with other studies [25], that is, treatment with proteolytic enzymes should promote bacteriocin inactivation because they are composed of peptides [24].…”

Identification of Listeria monocytogenes on Green Mussels and Cockle Shell

“…Salah satu penyebab rendahnya kontaminasi L. monocytogenes pada kerang-kerangan adalah adanya bakteriosin yang dihasilkan oleh bakteri asam laktat yang dihasilkan oleh kerang-kerangan. Hal ini dibuktikan oleh penelitian yang dilakukan Pinto et al (2009) yang menunjukkan keberadaan antiListeria bakteriosin yang diisolasi dari kerang. Pada penelitian tersebut, terdapat dua jenis bakteriosin yang diproduksi oleh Enterococcus faecium dan Pediococcus pentosaceus yang telah terbukti memiliki aktivitas penghambatan terhadap pertumbuhan L. monocytogenes.…”

Selection of Lactobacillus Species from Intestinal Microbiota of Fish for Their Potential Use as Biopreservatives

“…It is clear that indigenous bacteria present in marine environment as well as resulting from post contamination during processing are responsible for many cases of illnesses [1][2][3]. In the last years, traditional processes applied to seafood like salting, smoking and canning have decreased in favor of mild technologies involving lower salt content, lower heating temperature and vacuum (VP) or modified atmosphere packing (MAP, [3][4][5].…”