Qualitative detection of amine formation in decarboxylase assay
mediumwas tested by inoculating each strain in the decarboxylase
medium described by Bover-Cid and Holzapfel (1999). The medium
contained the corresponding precursor amino acid at 0.5% final
concentration (L-histidine monohydrochloride, tyrosine di-sodium
salt, L-ornithine monohydrochloride and L-arginine monohydrochloride),
pyridoxal-5-phosphate, growth factors, buffer compounds
and purple bromocresol as pH indicator. The pH was
adjusted to 5.3 and the medium was autoclaved. The precursor
amino acids were purchased from Sigma (St. Louis, MO, USA). A
bacterial suspension (109 CFU/mL)was made from a plate culture in
decarboxylase medium without amino acids. An aliquot of the
suspension (0.2 mL) was inoculated into 2 mL of the same medium
with and without amino acids (as control). After 7 days incubation
at 30 C under anaerobic conditions, the medium was centrifuged
and the supernatant was kept at 20 C until biogenic amines
analysis.