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Advisor(s)
Abstract(s)
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 genusand
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.
Description
Keywords
Bacteriocins Characterization Seafood Enterococcus faecium Pediococcus pentosaceus Listeria monocytogenes Biopreservation
Citation
"International Journal of Food Microbiology". ISSN: 0168-1605. 129: 1 (2009) 50–58
Publisher
Elsevier