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Appl. Environ. Microbiol., 02 1996, 612-619, Vol 62, No. 2
MP Ryan, MC Rea, C Hill and RP Ross
Lactococcus lactis DPC3147, a strain isolated from an Irish kefir grain,
produces a bacteriocin with a broad spectrum of inhibition. The bacteriocin
produced is heat stable, particularly at a low pH, and inhibits
nisin-producing (Nip+) lactococci. On the basis of the observation that the
nisin structural gene (nisA) does not hybridize to DPC3147 genomic DNA, the
bacteriocin produced was considered novel and designated lacticin 3147. The
genetic determinants which encode lacticin 3147 are contained on a 63-kb
plasmid, which was conjugally mobilized to a commercial cheese starter, L.
lactis subsp. cremoris DPC4268. The resultant transconjugant, DPC4275, both
produces and is immune to lacticin 3147. The ability of lacticin
3147-producing lactococci to perform as cheddar cheese starters was
subsequently investigated in cheesemaking trials. Bacteriocin-producing
starters (which included the transconjugant strain DPC4275) produced acid
at rates similar to those of commercial strains. The level of lacticin 3147
produced in cheese remained constant over 6 months of ripening and
correlated with a significant reduction in the levels of nonstarter lactic
acid bacteria. Such results suggest that these starters provide a means of
controlling developing microflora in ripened fermented products.
Copyright © 1996, American Society for Microbiology
An application in cheddar cheese manufacture for a strain of Lactococcus lactis producing a novel broad-spectrum bacteriocin, lacticin 3147
National Dairy Products Research Centre, Moorepark, Fermoy, County Cork, Republic of Ireland.
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