Production, stability, gene sequencing and in situ anti-Listeria activity of mundticin KS expressed by three Enterococcus mundtii strains

Abstract

a b s t r a c tThree enterococci (WFE3, WFE20 and WFE31) selected as presumptive bacteriocin producers were found to be active against Listeria monocytogenes. In this study, due to their potential industrial/food applications, the three bacterial isolates were extensively characterized. Identification was performed by means of a combined 16S rRNA gene sequencing and multiplex PCR approach, and was confirmed with the sequencing of a partial region of a protein-encoding gene, namely pheS. The three isolates belonged unequivocally to the species Enterococcus mundtii. The randomly amplified polymorphic DNA (RAPD) analysis recognized three distinct strains. The supernatants were mainly active against Listeria spp., but some lactic acid bacteria were also inhibited. The proteinaceous nature of the three supernatants was detected after treatment with proteinase K, protease B and trypsin. The bacteriocins were found to be heat resistant, stable in a large pH range and in presence of ethanol. The bacteriocins were not adsorbed onto the surface of the producer cells and their effect was bactericidal. The production of bacteriocins was higher at neutral pHs and temperatures in the range 30e37 C. The active supernatants did not show cytotoxicity against human erythrocytes and the three strains were susceptible to the action of common antibiotics. The genetic characterization of the bacteriocin genes showed that all three strains produced mundticin KS. They produced it in five food model systems, sterilized by thermal treatment or filtration, prepared from fresh vegetables, cereals, cheeses, meats and fishes. The in situ anti-listerial activities of the strains WFE3, WFE20 and WFE31 were quantitatively different.

Anti-proliferative effects of Enterococcus strains isolated from fermented dairy products on different cancer cell lines

“…Similar results have been reported by other researchers (Settanni et al, 2014;Vera Pingitore, Todorov, Sesma, & Gombossy de Melo Franco, 2012). Meanwhile, all three examined strains showed high inhibition activities for Gram-negative pathogens, such as K. pneumoniae and S. flexneri.…”

Transfer, composition and technological characterization of the lactic acid bacterial populations of the wooden vats used to produce traditional stretched cheeses

“…In that work, E. faecalis persisted longer than other species during ripening. This species, together with E. faecium, E. durans, Enterococcus mundtii and E. casseliflavus, is commonly found in many raw materials and foods (Corsetti et al, 2007;Franciosi et al, 2009;Settanni et al, 2014).…”

Synergistic antimicrobial action and potential application for fish preservation of a bacteriocin produced by Enterococcus mundtii isolated from Odontesthes platensis

“…On the contrary, none of the enterocin A, B, P and L50A/B structural genes could be amplified suggesting that the corresponding gene clusters were not present in E. mundtii. In particular, only a few studies reported the inhibitory action of bacteriocins produced by E. mundtii (Pingitore, Todorov, Sesma, & Franco, 2012;Settanni et al, 2014). It must be highlight that mundticin KS produced by E. mundtii Tw56 was active against Gram negative bacteria, an unusual characteristic for bacteriocin produced by LAB.…”