Biomedical Engineering Reference
In-Depth Information
7.2
Application of Bacteriocin-Producing Strains
Bacteriocin production by fi sh-acclimatized bacterial species is of great interest for
inhibition of pathogenic microorganisms in seafood products (Table
7.1
).
Antagonistic bacterial strains (such as those isolated from cold smoked seafood
products) could be applied for the competitive exclusion of
L. monocytogenes
in the
processed food products. Many LAB strains are able to grow at refrigeration tem-
peratures. They tolerate modifi ed atmosphere packaging, low pH, high salt concen-
trations, and the presence of additives such as lactic acid, ethanol, or acetic acid.
The selected antagonistic strains should meet several criteria: (1) to be able to grow
on the fi sh product during cold storage and produce antimicrobials to inactivate
L. monocytogenes
, or at least inhibit growth of the pathogen; (2) do not cause
adverse effects on the food product (such as off fl avours, colour changes); (3) do not
have adverse effects on health (e.g., production of biogenic amines) or carry antibi-
otic resistance or virulence traits. Inoculated strains could have probiotic properties,
but this approach for administration of probiotics through seafood products has not
been exploited yet.
Since LAB comprise the dominant microbiota in CSS (González-Rodríguez
et al.
2002
; Cardinal et al.
2004
), research has focused on selection of antagonistic
LAB strains from the processed products.
L. monocytogenes
can be inhibited by
carnobacteria cultures that do not produce bacteriocins, partly due to glucose deple-
tion (Nilsson et al.
2005
). However, LAB strains producing bacteriocins (mainly
Carnobacterium
and
Lactobacillus
species) may be superior for biopreservation
compared to non-bacteriocinogenic strains. Examples of trials carried out with
antagonistic bacteria in CS foods (such as CSS, cold-smoked salmon-trout, or cold-
smoked surubim) included antagonistic strains of
C. piscicola
,
C. divergens
,
Lactobacillus sakei
,
Lactobacillus casei
,
Lactobacillus curvatus
,
Lactobacillus del-
brueckii
,
Lactobacillus plantarum
,
Pediococcus acidilactici
or
E. faecium
(Leisner
et al.
2007
; Calo-Mata et al.
2008
; Galvez et al.
2008
; Rihakova et al.
2009
; Tomé
et al.
2008
; Tahiri et al.
2009b
).
C. piscicola
is often isolated as the naturally dominant LAB species on CSS
( Paludan-Müller et al.
1998
). Therefore, CSS may be a good source for isolation of
bacteriocin-producing LAB. The strains
C. piscicola
A9b (producer of carnobacte-
riocin B2) and
C. piscicola
CS526 (producer of piscicolin CS526) showed anti-
Listeria activity in salmon juice and in CSS, respectively (Nilsson et al.
2004
;
Yamazaki et al.
2003
). Also, the strains
C. divergens
V41 and
C. piscicola
V1 from
processed seafoods were reported to be highly effective against
L. monocytogenes
in co-culture experiments carried out in a simulated cold smoked fi sh system at 4 °C
(Duffes et al.
1999b
). In cold-smoked surubim (a native Brazilian freshwater fi sh),
inhibition of
L. monocytogenes
by the bacteriocinogenic strain
C. piscicola
C2 iso-
lated from vacuum-packed cold-smoked surubim and by other
C. piscicola
strains
isolated from CSS was reported (Alves et al.
2005
). Strong inhibition was detected
both in fi sh peptone model systems and in cold-smoked fi sh juices. Although the
carnobacteria grew poorly on cold-smoked surubim at 10 °C, the strains were able
