title: Growth, biogenic amine production and tyrDC transcription of Enterococcus faecalis in synthetic medium containing defined amino acid concentrations.
abstract: OBJECTIVE
  The tyraminogenic potential of the strains Enterococcus faecalis EF37 and ATCC 29212 was investigated in a synthetic medium containing defined amounts of tyrosine and phenylalanine at different temperatures.
  
  
  RESULTS
  Enterococci growth and the production of biogenic amines (BA) were evaluated in relation to their pre-growth in medium containing tyrosine. Significant differences between the two strains were evidenced at metabolic level. Both the pre-adapted strains grew faster in all the tested conditions, independently of the presence of the precursor. Temperatures of 30 and 40°C positively affected the growth parameters. The tyrosine decarboxylase (tyrDC) activity of the strain EF37 was positively affected by pre-adaptation, while ATCC 29212 showed a faster and higher tyramine accumulation with not-adapted cells. The expression analysis of the gene tyrDC confirmed the influence of the growth conditions on gene transcription.
  
  
  CONCLUSIONS
  The small differences found between the two strains in the maximum transcript level reached rapidly after the inoculum and the different behaviour in the tyramine accumulation suggested the possible involvement of complex regulation mechanisms on the tyrDC or on the membrane transport systems, which could affect the different BA accumulation trend.
  
  
  CONCLUSIONS
  This study gives deeper insight into the metabolic regulation of tyrDC activity of enterococci.
authors.affiliation: Department of Agricultural and Food Sciences, University of Bologna, Cesena (FC), Italy.
authors.forename: E
authors.initials: E
authors.lastname: Bargossi
authors.affiliation: Interdepartmental Center for Industrial Agri-Food Research, University of Bologna, Cesena (FC), Italy.
authors.forename: G
authors.initials: G
authors.lastname: Tabanelli
authors.affiliation: Interdepartmental Center for Industrial Agri-Food Research, University of Bologna, Cesena (FC), Italy.
authors.forename: C
authors.initials: C
authors.lastname: Montanari
authors.affiliation: Department of Biotechnology, University of Verona, Verona (VR), Italy.
authors.forename: V
authors.initials: V
authors.lastname: Gatto
authors.affiliation: Department of Agricultural and Food Sciences, University of Bologna, Cesena (FC), Italy.
authors.forename: F
authors.initials: F
authors.lastname: Chinnici
authors.affiliation: Department of Agricultural and Food Sciences, University of Bologna, Cesena (FC), Italy.|Interdepartmental Center for Industrial Agri-Food Research, University of Bologna, Cesena (FC), Italy.
authors.forename: F
authors.initials: F
authors.lastname: Gardini
authors.affiliation: Department of Biotechnology, University of Verona, Verona (VR), Italy.
authors.forename: S
authors.initials: S
authors.lastname: Torriani
mesh_terms: D001679:Biogenic Amines / Q000096:biosynthesis*; D003470:Culture Media; D013293:Enterococcus faecalis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D014158:Transcription, Genetic; D014439:Tyramine / Q000096:biosynthesis; D014443:Tyrosine / Q000378:metabolism; D014445:Tyrosine Decarboxylase / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D001679:Biogenic Amines; D003470:Culture Media; D014443:Tyrosine; D010649:Phenylalanine; D014445:Tyrosine Decarboxylase; D014439:Tyramine
keywords: fermentation biotechnology; fermented foods; food safety; gene expression; lactic acid bacteria; metabolic processes