Cometabolism of citrate and glucose by Enterococcus faecium FAIR-E 198 in the absence of cellular growth.
Citrate metabolism by Enterococcus faecium FAIR-E 198, an isolate from Greek Feta cheese, was studied in modified MRS (mMRS) medium under different pH conditions and glucose and citrate concentrations. In the absence of glucose, this strain was able to metabolize citrate in a pH range from constant pH 5.0 to 7.0. At a constant pH 8.0, no citrate was metabolized, although growth took place. The main end products of citrate metabolism were acetate, formate, acetoin, and carbon dioxide, whereas ethanol and diacetyl were present in smaller amounts. In the presence of glucose, citrate was cometabolized, but it did not contribute to growth. Also, more acetate and less acetoin were formed compared to growth in mMRS medium and in the absence of glucose. Most of the citrate was consumed during the stationary phase, indicating that energy generated by citrate metabolism was used for maintenance. Experiments with cell-free fermented mMRS medium indicated that E. faecium FAIR-E 198 was able to metabolize another energy source present in the medium.
Vaningelgem
Frederik
F
Research Group of Industrial Microbiology, Fermentation Technology and Downstream Processing, Department of Applied Biological Sciences and Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
Ghijsels
Veerle
V
Tsakalidou
Effie
E
De Vuyst
Luc
L
D002611:Cheese / Q000382:microbiology*; D002951:Citrates / Q000378:metabolism*; D003470:Culture Media; D016984:Enterococcus faecium / Q000254:growth & development* / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology
D002951:Citrates; D003470:Culture Media; D005947:Glucose