370 Chapter 14
nated PAC 1.0. The production of the bacte-
riocin (designated PA - 1) was coded on a
9.4 - kbp plasmid designated pSRQ 11. Later,
Pucci et al. (1988) demonstrated that pedio-
cin PA - 1 inhibited Listeria monocytogenes in
broth, agar plate, and food systems, including
cottage cheese.
Based on the fi ndings of Pucci et al.
(1988) , a patent was issued to Vandenbergh
et al. (1990) , wherein they described the use
of dried metabolites from Pediococcus acidi-
lactici PAC 1.0 to control Listeria in food
systems. Henderson et al. (1992) extended
the study on pediocin PA - 1 by describing its
purifi cation and primary structure. Later,
Marugg et al. (1992) elucidated the nucleo-
tide sequence of the genes involved in the
production of pediocin PA - 1. As knowledge
of the bacteriocin accumulated, technology
for industrial - scale production of the bacte-
riocin and for drying the “ fermentate contain-
ing pediocin PA - 1 ” was developed.
Currently, standardized dried powders
containing the bacteriocin (pediocin PA - 1)
and other active acidic metabolites are com-
mercially available for controlling Listeria in
dairy foods. The acidic metabolite compo-
nents are considered to act synergistically
with the bacteriocin in controlling the
intended targets (Kerry, 2004f ). A similar
product containing metabolites such as
organic acids and peptides derived from the
fermentation of a dairy Lactococcus strain
exhibiting inhibitory activity against several
Gram - positive bacteria is also currently
available on the market for use in dairy prod-
ucts (Kerry, 2004g ).Purifi ed Bacteriocin
Among the various bacteriocins elaborated
by lactic acid bacteria, only nisin in purifi ed
form has been used in food products. Hirsch
(1951) fi rst suggested the use of nisin in food
products.
The term nisin denotes a family of inhibi-
tory polypeptide molecules elaborated byMicrobial Metabolites
Containing Bacteriocins
Bacteriocins are ribosomally synthesized
proteinceous substances or peptides produced
by bacteria that inhibit other bacterial species
or strains. Lactic acid bacteria commonly
used in starters and found in fermented dairy
products produce bacteriocins. Many of the
species and strains that belong to the genera
Lactococcus, Lactobacillus, Streptococcus,
and Pediococcus elaborate bacteriocins.
These bacteriocins normally have a narrow
spectrum of activity against closely related
strains or species. However, certain bacterio-
cins of lactic acid bacteria have a broader
spectrum of activity against bacteria that
cross the species and even the generic lines. A
good example of such a bacteriocin is nisin,
which is produced by certain strains of
Lactococcus lactis ssp. lactis. Nisin is active
against closely related lactococci, many lac-
tobacilli, streptococci, and pediococci, as
well as Listeria sp., and several spore - forming
Bacillus sp. and Clostridium sp.
Pediococci, often encountered in cheeses,
produce bacteriocins called pediocins. Pedio-
cins also have a wide spectrum of activity,
affecting the growth of other closely related
pediococci, many lactobacilli, and Listeria
sp. However, they have no inhibitory activity
against dairy lactococci.
All of the aforementioned bacteria belong
to the Gram - positive group. Generally, bac-
teriocins derived from Gram - positive bacte-
ria do not affect Gram - negative bacteria.
The widespread food - and dairy - related
outbreaks of Listeria monocytogenes in
several parts of the world over the past two
decades has led to a clamor for fi nding suit-
able control measures for containing listerial
food - borne outbreaks. A breakthrough for
controlling Listeria monocytogenes came
about when Gonzalez and Kunka (1987)
reported on the production of a bacteriocin
active against several Gram - positive species
by a strain of Pediococcus acidilactici desig-