Production of biogenic amines by Enterococci

Abstract

Enterococci were presented in all tested samples of raw cow milk (six samples) at the level 10³–10⁵ CFU/ml, fresh cheeses (five samples) at the level 10²–10⁶ CFU/g and semi-hard cheeses (five samples) at the level 10³–10⁵ CFU/g. All 33 isolated Enterococcus strains were screened for decarboxylase activity by usage differential growth medium and 20 of them possessed tyrosine decarboxylase activity. A collection of eight strains with the strongest decarboxylase activity were identified by species specific PCR as E. faecium (Z3, Z4, Br4 and 6/4D strains) and E. faecalis (Ž4, 3/3C and 4/1A strains). Enterococcus spp. Z1 strain was not identified at the species level by used methods, but the genus was confirmed by PCR method. Their tyrosin decarboxylase activity was confirmed by TLC and detection of tdc gene. Z1, Z3 and Z4 strains showed also histidine decarboxylase activity on the differential growth medium with histidine, but this activity was evaluated by TLC as a false positive reaction of medium.