Biomedical Engineering Reference
In-Depth Information
Spain), and a mixture of lactic cultures and species extract (Biamex-01, Laboratorios
Amerex S.A., Madrid, Spain) were tested on fresh salmon in combination with a dry
salt-sugar mix and stored at 8 °C (Montiel et al.
2013
). All antimicrobials tested
were effective in inhibiting growth of
L. monocytogenes
. After 7 days of storage, the
biopreservative based on
P. acidilactici
strongly inhibited growth of the pathogen,
with counts 3.6 and 1.5 log CFU/g lower than in the control and salt-sugar mix-
treated samples, respectively (Montiel et al.
2013
).
Research in enterococci from seafoods has gained interest for biocontrol of
L. monocytogenes
in the processed products, and bacteriocin-producing strains
have been isolated from seafoods such as
E. faecium
and
Enterococcus mundtii
strains producers of unknown bacteriocins (Campos et al.
2006
; Hosseini et al.
2009
; Valenzuela et al.
2010
), or
E. faecium
strains producers of enterocin P (Arlindo
et al.
2006
) or enterocin B (Pinto et al.
2009
).
Enterococcus
isolates from sea bass
and sea bream showed broad antimicrobial activities (against
Carnobacterium
sp.,
Bacillus
sp.,
L. monocytogenes
,
Aeromonas salmonicida
,
Aeromonas hydrophila
and
Vibrio anguillarum
) and carried enterocin genes (including enterocins A, B,
L50 and P), strengthening the potential applications of these LAB strains to the
biopreservation of minimally-processed seafood products (Chahad et al.
2012
).
Also, enterococci from other sources have been suggested for application in sea-
foods. An
E. mundtii
strain isolated from soil with strong anti-
Listeria
activity was
tested in vacuum-packed CSS stored at 5 °C (Bigwood et al.
2012
). This strain
inhibited the growth of
L. monocytogenes
on the CSS during its 4 week shelf life.
When
L. monocytogenes
(ca. 3.4 log CFU/cm
2
) was co-inoculated with
E. mundtii
(7 log CFU/cm
2
), growth of the pathogen was reduced compared to the control samples
with an approximate 3 log CFU/cm
2
difference in concentration after 4 weeks incuba-
tion (Bigwood et al.
2012
). The inhibitory effect was found to be dependent on the
initial inoculum of enterococci. The
E. mundtii
isolate was able to grow at 5 °C in
culture medium, but not on the CSS, and for that reason a high inoculum of enterococci
was required in order to achieve a strong inhibition of the listeriae. The study con-
cluded that
E. mundtii
could control the growth of
L. monocytogenes
at low tempera-
tures, indicating a potential application in controlling this pathogen in chilled foods.
While most studies have focused on inhibition of
L. monocytogenes
in seafood
products, other pathogenic bacteria (such as
Vibrio parahaemolyticus
,
Vibrio vulni-
fi cus
and
Vibrio cholerae
,
Clostridium botulinum
, histamine-producing bacteria,
and post-contaminating bacteria, such as
S. aureus
or
Salmonella
sp.) or spoilage
bacteria (such as
Shewanella putrefaciens
,
Photobacterium phosphoreum
,
Aeromonas
spp. and
Pseudomonas
spp.) are still a matter of concern (Gram and
Dalgaard
2002
; Calo-Mata et al.
2008
). Therefore, there is a growing interest to
extend the spectrum of inhibition of bacteriocins in combination with other hurdles
and also on isolation of LAB strains with broader spectrum of inhibitory activity.
One study reported that treatment of whole shrimp with potassium sorbate in com-
bination with
Bifi dobacterium breve
cells extended the product microbiological
shelf life (Al-Dagal and Bazaraa
1999
). Also, treatment of plaice fi llets with a prep-
aration of
Bifi dobacterium bifi dum
cells and thymol combined with low storage
temperature and anoxia/hypoxia, showed a great effi cacy against the main fresh
