Acta Vet. Brno 2012, 81: 145-151
Decarboxylase activity test of the genus Enterococcus isolated from goat milk and cheese
Biogenic amines are aliphatic, aromatic or heterocyclic alkalic substances with a biological impact on live organisms. They may cause serious problems to sensitive persons in combination with some medicaments or in case of higher intake. They are present in non-fermented food, usually coming from contaminating microflora, and especially in fermented food where biogenic amines might be produced by microbiota used for procedure. The genus Enterococcus spp. can occur in cheese because their resistance to pasteurizing temperatures is much higher compared to other mesophilic microorganisms. Previous studies have targeted the occurrence and problems of enterococci isolated from cow and sheep milk. The aim of this study was to detect decarboxylase activity of enterococci isolated from goat milk and cheese and to see how the particular temperatures involve decarboxylase activity using a rapid and inexpensive screening method. In this study, bacteria Enterococcus faecium, E. mundtii, E. durans were isolated from 9 samples of goat milk and cheeses. Colonies of bacteria were inoculated on diagnostic medium fortified with amino acids (lysine, arginine, phenylalanine, histidine, tyrosine and tryptophan) and acidity indicator. Changes in colour detected decarboxylase activity of enterococci. The only positive reactions were determined in samples containing arginine and tyrosine. Cultivation of bacteria was confirmed by PCR. All of the tested microorganisms showed significant activity of tyrosindecarboxylase and arginindecarboxylase which was regulated by temperature and influenced by duration of cultivation. The test of decarboxylase activity using colour changes is suitable for a relatively rapid and inexpensive detection of microorganisms that are able to produce biogenic amines.
