Abstract: The influences of cell-free solutions (CFSs) of lactic
acid bacteria (LAB) on cadaverine and other biogenic amines
production by Listeria monocytogenes and Staphylococcus aureus
were investigated in lysine decarboxylase broth (LDB) using HPLC.
Cell free solutions were prepared from Lactococcus lactis subsp.
lactis, Leuconostoc mesenteroides subsp. cremoris, Pediococcus
acidilactici and Streptococcus thermophiles. Two different
concentrations that were 50% and 25% CFS and the control without
CFSs were prepared. Significant variations on biogenic amine
production were observed in the presence of L. monocytogenes and S.
aureus (P < 0.05). The function of CFS on biogenic amine production
by foodborne pathogens varied depending on strains and specific
amine. Cadaverine formation by L. monocytogenes and S. aureus in
control were 500.9 and 948.1 mg/L, respectively while the CFSs of
LAB induced 4-fold lower cadaverine production by L.
monocytogenes and 7-fold lower cadaverine production by S. aureus.
The CFSs resulted in strong decreases in cadaverine and putrescine
production by L. monocytogenes and S. aureus, although remarkable
increases were observed for histamine, spermidine, spermine,
serotonin, dopamine, tyramine and agmatine in the presence of LAB
in lysine decarboxylase broth.
Abstract: Dextran is a D-glucose polymer which is produced by
Leuconostoc mesenteroides grown in a sucrose-rich media. The
organism was obtained from the Persian Type Culture Collection
(PTCC) and was transferred in MRS broth medium at 30°C and pH
6.8 for 24 h. After preparation of inoculums, organisms were
inoculated into five liquid fermentation media containing either
molasses or cheese whey or different combinations of cheese whey
and molasses. After certain fermentation period, the produced
dextran was separated and dried. Dextran yield was calculated and
significant differences in different media were observed.
Furthermore, FT-IR analysis was performed and the results showed
that there were no significant differences in the produced dextran
structures.