Natural antimicrobials as additives and ingredients for the preservation of foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 132

the starter cultures, but at the same time provide protection against colonisation
and growth of Gram-positive food poisoning bacteria.
The two bacteriocins that have attracted most interest in addition to nisin are
pediocin and sakacin; these are described below. A number of comprehensive
reviews are available that describe other bacteriocins that have potential as food
preservatives (see Section 6.9 Sources of further information and advice).

Pediocin
Pediocins (class II bacteriocin) are produced by several strains of Pediococcus
acidilactici and P. pentosaceus (Papagianni and Anastasiadou 2009). Interestingly
a strain of Lactobacillus plantarum , strain WHE92, isolated from cheese has also
been shown to produce pediocin (Ennahar et al. 1996). The bacteriocins produced
by P. acidilactici are AcH, PA-1, JD and 5, and those produced by P. pentosaceus
are A, N5p, ST18, and PD1 (Anastasiadou et al. 2008). A non-purifi ed fermentate
commercial preparation of pediocin known as Alta™ 2341 based on PA1/AcH is
available but the active ingredient is not stated (Rodríquez et al. 2000; Papagianni
and Anastasdiou 2009).
The mode of action of pediocin towards sensitive Gram-positive bacteria is
directed at the cellular membrane and is more bactericidal than bacteriostatic
(Bhunia et al. 1988, 1991; Chikindas et al. 1993). Pediocins have a wide range of
antimicrobial spectrum against Gram-positive bacteria but like nisin have little or
no activity against Gram-negative bacteria, yeasts and moulds. Again like nisin,
pediocins can be effective against Gram-negative bacteria if the outer cell
envelope is permeabilized by the action of chelating agents. Strains of B. cereus ,
L. monocytogenes , L. innocua , S. aureus , Lc. lactis , C. botulinum , C. tyrobutyricum
and C. sporogenes have been reported as sensitive (Berry et al. 1991; Daeschel
and Klaenhammer 1985; Hoover et al. 1988; Piva and Headon 1994; Pucci et al.
1998). Some Gram-positive bacterial species and strains are resistant to pediocin
PA-1/AcH (Bhunia et al. 1988, 1991; Hanlin et al. 1993). Mode of action studies
indicate that resistant cells absorb pediocin Pa-1/AcH on to the cell surface but at
a lower level than a sensitive strain. A number of applications have been
investigated and these are summarised in Table 6.2.

￿ ￿ ￿ ￿ ￿

Sakacin
Sakacins (class II bacteriocins) are a group of bacteriocins produced by certain
Lb. sakei strains. The fi rst sakacin identifi ed was sakacin A produced by Lb. sakei
Lb 706 isolated from raw meat (Schillinger and Lücke 1989). Since then various
other sakacins have been identifi ed and characterised from a variety of Lb. sakei
strains, most of which have been isolated from raw meat. Examples are sakacin M
(Sobrino et al. 1991, 1992), sakacin P (Tichacaczek et al. 1994), sakacin 674
(Holck et al. 1994), sakacin B (Samelis et al. 1994) and sakacin K (Hugas et al.
1995). No commercial products are currently available.
Like both nisin and pediocin described previously the mode of action is
directed at the cytoplasmic membrane of susceptible Gram-positive bacteria.
Compared to nisin and pediocin, sakacins have a relatively narrow antibacterial