CENTRO DE REFERENCIA PARA LACTOBACILOS
Unidad Ejecutora - UE
Citrate metabolism by Enterococcus faecium and Enterococcus durans isolated from goats and ewes milk: Influence of glucose and lactose
MARIA EUGENIA CABRAL; MARÍA C. ABEIJÓN; ROXANA MEDINA; SILVIA GONZALEZ
CANADIAN JOURNAL OF MICROBIOLOGY
Lugar: Canada; Año: 2007 vol. 53 p. 607 - 607
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 utilised citrate as sole energy source E. faecium ET C9 showed diauxic growth in presence of limiting glucose concentration. None of these strains used citrate until glucose was fully metabolized. These strains showed co-metabolism citrate-lactose. Lactate, acetate, formate and flavour compounds (diacetyl, acetoin and 2,3-butanediol) were detected in both strains. The highest flavour compounds production was detected in media with citrateglucose and citrate-lactose by E. durans Ov 421. Citrate lyase was inducible for both strains. Acetate kinase activities presented the highest values in LAPTc medium, showing E. faecium ET C9 a specific activity 2.4-fold higher than E. durans. Highest levels of a-acetolactate synthase specific activity were detected in E. durans grown in LAPTc+g, which is in accordance with the highest levels of flavour compounds detected in this medium. Diacetyl/acetoin reductase showed lower specific activity values in presence of citrate. E. faecium and E. durans presented citrate lyase, acetate kinase, a-acetolactate synthase and diacetyl/acetoin reductase activities. These enzymes are necessary for conversion of citrate to flavour compounds important in fermented dairy products.