At present four classes of LAB bacteriocins have been
identified (Table 1). Nisin which is produced by Lactobacillus
lactis subsp lactisstrains, belongs to the class 1 lantibiotics
(Dodd and Gasson, 1994; Jack et al.,1995) and is active
against many gram positive bacteria including Listeria spp. It
prevents the growth of germinating bacillus and clostridial
spores and through the addition of calcium chelator, it is
active against some gram negative bacteria (Stevens et al.,
1991). The mature nisin molecule is just 34 amino acids long
and undergoes certain post translational modifications in
which serine and threonine residues are dehydrated and
several thio-ether bridges are formed, this results in the
formation of fivering structures. The primary target of Nisin’s
antimicrobial action is the cell membrane. It is thought that