title: Amino acid conversions by coagulase-negative staphylococci in a rich medium: Assessment of inter- and intraspecies heterogeneity.
abstract: The ability of coagulase-negative staphylococci (CNS) to convert amino acids into volatile compounds and biogenic amines was investigated after 24h and 48 h of incubation in a rich medium (brain heart infusion). Volatile compounds were measured with static-headspace gas chromatography and mass spectrometry (SH-GC-MS); biogenic amine measurements were carried out with a newly developed method based on ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). In total, 56 CNS strains from five different species were used, namely Staphylococcus carnosus, Staphylococcus epidermidis, Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus xylosus. With respect to the production of volatile compounds, the leucine-derived 3-methyl butanol was produced over time by most CNS strains, up to 52 μM for S. xylosus W1-1 after 48 h of incubation. The average production by strains of S. xylosus was significantly higher than for strains of S. carnosus, whereas strains of S. epidermidis turned out to be poor producers. Yet, differences between species were blurred to a large degree because of the high strain variability. A few strains also produced 3-methyl butanal on top of the amount that was already present in the medium background, although most CNS led to a decrease of this compound. Concerning biogenic amines, the average total concentrations per species remained below 100 μM after 48 h of incubation. The most abundant variant was 2-phenylethylamine (PEA), especially within S. carnosus (average of 65 μM after 48 h of incubation). Yet, some individual strains were able to produce higher concentrations, as found for the PEA production of 295 μM by S. epidermidis ATCC 12228 after 48 h of incubation. The insights obtained during this study indicate heterogeneity and are of importance in view of both starter culture development and the evaluation of a spontaneously established CNS microbiota in artisan-type meat fermentations.
authors.affiliation: Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Despoina Angeliki
authors.initials: DA
authors.lastname: Stavropoulou
authors.affiliation: Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Borremans
authors.affiliation: Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: De Vuyst
authors.affiliation: Laboratory for Animal Nutrition and Animal Product Quality, Department of Animal Production, Ghent University, Melle, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: De Smet
authors.affiliation: Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium. Electronic address: fleroy@vub.ac.be.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Leroy
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001679:Biogenic Amines / Q000032:analysis; D003470:Culture Media / Q000737:chemistry; D005285:Fermentation; D005516:Food Microbiology; D008461:Meat Products / Q000382:microbiology; D013210:Staphylococcus / Q000201:enzymology / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D055549:Volatile Organic Compounds / Q000032:analysis
chemical_list: D000596:Amino Acids; D001679:Biogenic Amines; D003470:Culture Media; D055549:Volatile Organic Compounds
keywords: Biogenic amines; Coagulase-negative staphylococci; Meat fermentation; UPLC–MS/MS; Volatile compounds