| Pediocin AcH, Nisin, Sakacin A and Nisaplin in addition to three nonbacteriocin metabolites produced by starter culture bacteria were inhibitory to food-borne pathogens growing in foods at refrigeration temperature. All bacteriocin preparations were bacteriocidal to Listeria species/strains but not to any of the gram-negative pathogens. Storage studies indicated that bacteriocins did not have bacteriostatic properties against surviving cells. Diacetyl, however, was bacteriocidal to gram-negative pathogens but not to Listeria used in this study. Pediocin AcH was effective in reducing the population level of Listeria monocytogenes strains in sterile food systems. The maximum bacteriocidal action of pediocin AcH was rapid and was not interfered with by the food system.; The stability of pediocin producing plasmid, pSMB74, was also studied. Loss of Pap{dollar}sp+{dollar} phenotype during 60 d test period was higher in strain H than in strain LB 42-923. Among the Pap{dollar}sp-{dollar} variants only about 1 {dollar}times{dollar} 10{dollar}sp{lcub}-3{rcub}{dollar} cells for strain H and 6 {dollar}times{dollar} 10{dollar}sp{lcub}-3{rcub}{dollar} for strain LB 42-923 were Pap{dollar}sp{lcub}rm S{rcub}{dollar}. Plasmid analysis showed that the Pap{dollar}sp-{dollar} Pap{dollar}sp{lcub}rm S{rcub}{dollar} variants had lost the pSMB74. Plasmids that encode bacteriocin production phenotype in four Pediococcus acidilactici strains after restriction enzyme digestion, produced similar fragments and thus these plasmids were considered to be the same. A restriction map of this plasmid, pSMB74, has been constructed to facilitate locating the gene encoding for pediocin AcH.; Information acquired by sequencing of F3 fragments (Hind III digested pSMB74) indicated that pediocin AcH was not encoded in this fragment. Analysis of nucleotide sequence showed no ribosomal binding sites. The nucleotide sequence of this fragment showed no homology with other characterized bacteriocin operons as determined by computer analysis. |
