Production assays were performed in liquid
media supplemented with the appropriate precursor amino
acid; culture supernatants were then tested for BA by (U)
HPLC. In addition, the presence of key genes involved in
the biosynthetic pathways of the target BA, including the
production of putrescine via the agmatine deiminase pathway,
was assessed by PCR. Twenty strains were shown to
have genes involved in the synthesis of BA; these belonged
to the species Lactobacillus brevis (4), Lactobacillus curvatus
(3), Lactococcus lactis (11) and Streptococcus thermophilus
(2). With the exception of the two S. thermophilus
strains, all those possessing genes involved in BA
production synthesized the corresponding compound.
Remarkably, all the putrescine-producing strains used the
agmatine deiminase pathway. Four L. brevis and two L.
curvatus strains were found able to produce both tyramine
and putrescine. There is increasing interest in the use of
autochthonous LAB strains in starter and adjunct cultures
for producing dairy products with ‘particular geographic
indication’ status. Such strains should not produce BA; the
present results show that BA production capacity should be
checked by (U)HPLC and PCR.