Diversity of volatile organic compound production from leucine and citrate in Enterococcus faecium

• Published in: Applied microbiology and biotechnology Vol. 104; no. 3; pp. 1175 - 1186
• Main Authors: D’Angelo, Matilde, Martino, Gabriela P., Blancato, Victor S., Espariz, Martín, Hartke, Axel, Sauvageot, Nicolas, Benachour, Abdellah, Alarcón, Sergio H., Magni, Christian
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-02-2020; Springer; Springer Nature B.V
• Subjects: Acetoin; Amino acids; Applied Genetics and Molecular Biotechnology; Aroma compounds; Biodegradation; Biomedical and Life Sciences; Biotechnology; Butanol; Cell culture; Citric acid; Diacetyl; Enterococcus faecium; Fermentation; Fermented food; Flavor; Gas chromatography; Isopentyl alcohol; Leucine; Life Sciences; Mass spectrometry; Mass spectroscopy; Metabolism; Microbial Genetics and Genomics; Microbiology; Milk; Organic compounds; Phenotypes; Principal components analysis; Pyruvic acid; Solid phase methods; Solid phases; Strains (organisms); VOCs; Volatile organic compounds; Argentina; Citrate; Aroma compound; Rational strain selection; Leucine; Enterococcus faecium
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-019-10277-4

Enterococcus faecium
is frequently isolated from fermented food; in particular, they positively contribute to the aroma compound generation in traditional cheese. Citrate fermentation is a desirable property in these bacteria, but this feature is not uniformly distributed among
E. faecium
strains. In the present study, three selected
E. faecium
strains, IQ110 (
cit
−
), GM70 (
cit
+
type I), and Com12 (
cit
+
type II), were analyzed in their production of aroma compounds in milk. End products and volatile organic compounds (VOCs) were determined by solid-phase micro-extraction combined with gas chromatography mass spectrometry (SPME-GC-MS). Principal component analysis (PCA) of aroma compound profiles revealed a different VOC composition for the three strains. In addition, resting cell experiments of
E. faecium
performed in the presence of leucine, citrate, or pyruvate as aroma compound precursors allowed us to determine metabolic differences between the studied strains. GM70 (
cit
+
type I) showed an active citrate metabolism, with increased levels of diacetyl and acetoin generation relative to Com12 or to citrate defective IQ110 strains. In addition, in the experimental conditions tested, a defective citrate-fermenting phenotype for the Com12 strain was found, while its leucine degradation and pyruvate metabolism were conserved. In conclusion, rational selection of
E. faecium
strains could be performed based on genotypic and phenotypic analyses. This would result in a performing strain, such as GM70, that could positively contribute to flavor, with typical notes of diacetyl, acetoin, 3-methyl butanal, and 3-methyl butanol in an adjuvant culture.