Bacteriocin production by lactic acid bacteria isolated from fish, seafood and fish products

摘要

Analysis of 1245 lactic acid bacteria (LAB) isolates obtained from fish, seafood and fish products showed that 197 exerted direct antimicrobial activity against 20 spoilage and food-borne pathogenic microorganisms. Further evaluation of 64 LAB isolates selected on the basis of their direct antimicrobial activity revealed 25 secreted bacteriocins. Biochemical characterization, PCR analysis and/or DNA sequencing of the superoxide dismutase gene (sodA) and/or 16S rRNA gene (16S rDNA), and/or SDS-PAGE analyses of the 64 selected isolates allowed the identification of 24 of them as Enterococcus faecium, 22 as Enterococcus faecalis, seven as Pediococcus pentosaceus, five as Weissella cibaria, three as Lactobacillus sakei subsp. carnosus, one as L. sakei subsp. sakei, one as Lactobacillus curvatus subsp. curvatus and one as Leuconostoc mesenteroides subsp. cremoris. PCR analyses for the detection of genes encoding previously described bacteriocins performed on the 25 bacteriocinogenic strains showed that 19 strains (18 enterococci and 1 lactobacilli) amplified, at least, one of the tested genes, and up to four and two target genes were simultaneously detected in a single enterococcal and lactobacilli strain, respectively. Moreover, in vitro safety evaluation of E. faecium strains was carried out by detection of potential virulence factors, analysis of hemolysin, gelatinase and protease production, and susceptibility testing to antibiotics of relevance for human and veterinary industry. The results reported herein demonstrate the suitability of fish, seafood and fish products for the isolation of LAB (mainly enterococci), including (multi)bacteriocinogenic strains, encoding bacteriocins active against Listeria monocytogenes and other food-borne pathogens of interest for the food industry.