Citrate metabolism by Enterococcus faecium and Enterococcus durans isolated from goat's and ewe's milk: influence of glucose and lactose

• Published in: Canadian journal of microbiology Vol. 53; no. 5; pp. 607 - 615
• Main Authors: Cabral, M.E, Abeijón Mukdsi, M.C, Medina de Figueroa, R.B, González, S.N
• Format: Journal Article
• Language: English
• Published: Ottawa, ON National Research Council of Canada 01.05.2007; NRC Research Press; Canadian Science Publishing NRC Research Press
• Subjects: Animals; Animals, Domestic; Bacteria; Biological and medical sciences; carbohydrate metabolism; Carbon dioxide; Cells; Cheese; Cheese - microbiology; Chemical properties; citrate metabolism; Citrates; Citrates - metabolism; citric acid; cultured milk starters; Dairy products; Dextrose; Energy sources; enterococci; Enterococcus; Enterococcus durans; Enterococcus faecium; Enterococcus faecium - drug effects; Enterococcus faecium - growth & development; Enterococcus faecium - metabolism; enzyme activity; Enzymes; Evaluation; ewe milk; Female; flavor compounds; flavour; Food Microbiology; Fundamental and applied biological sciences. Psychology; Glucose; Glucose - metabolism; Glucose - pharmacology; goat milk; Goats; isolation; Kinetics; Lactose; Lactose - metabolism; Lactose - pharmacology; Metabolism; microbial physiology; Microbiology; Milk - enzymology; Milk - microbiology; métabolisme du citrate; Physiological aspects; saveur; Argentina; Glucose; Metabolism; Enterococcus durans; Streptococcaceae; Enterococcus faecium; Vertebrata; Ewe; Lactose; Mammalia; Bacteria; Micrococcales; Sheep; Goat; Artiodactyla; Ungulata; Milk
• ISSN: 0008-4166; 1480-3275
• DOI: 10.1139/W07-011

Citrate metabolism by Enterococcus faecium ET C9 and Enterococcus durans Ov 421 was studied as sole energy source and in presence of glucose or lactose. Both strains utilized citrate as the sole energy source. Enterococcus faecium ET C9 showed diauxic growth in the presence of a limiting concentration of glucose. Neither strain used citrate until glucose was fully metabolized. The strains showed co-metabolism of citrate and lactose. Lactate, acetate, formate, and flavour compounds (diacetyl, acetoin, and 2,3-butanediol) were detected in both strains. The highest production of flavour compounds was detected during growth of E. durans Ov 421 in media supplemented with citrate-glucose and citrate-lactose. Citrate lyase was inducible in both strains. Acetate kinase activities presented the highest values in LAPTc medium, with E. faecium ET C9 displaying a specific activity 2.4-fold higher than E. durans. The highest levels of α-acetolactate synthase specific activity were detected in E. durans grown in LAPTc+g, in accordance with the maximum production of flavour compounds detected in this medium. Diacetyl and acetoinreductases displayed lower specific activity values in the presence of citrate. Enterococcus faecium and E. durans displayed citrate lyase, acetate kinase, α-acetolactate synthase, and diacetyl and acetoin reductase activities. These enzymes are necessary for conversion of citrate to flavour compounds that are important in fermented dairy products.