title: Citrate catabolism and production of acetate and succinate by Lactobacillus helveticus ATCC 15807.
abstract: The citrate metabolism of Lactobacillus helveticus ATCC 15807 was studied under controlled-pH fermentations at pH 4.5 and pH 6.2. The micro-organism was able to co-metabolize citrate and lactose at both pH from the beginning of growth, which enhanced the rate of lactose consumption and lactic acid production, compared with cultures without citrate. The effect of citrate on cell growth was dependent on the balance between the ratio of dissociated to non-dissociated forms of the acetic acid produced and the extra ATP gained by the cells, both facts related to the citrate metabolism. The citrate catabolism determined a change in the fermentation pattern of L. helveticus ATCC 15807 from homolactic to a mixed-acid profile, regardless of the external pH. Within this new fermentation pattern, acetate was the major product formed (13-20 mM), followed by succinate (2.4-3.7 mM), while acetoine, dyacetile or butanediol were not detected. The mixed-acid profile displayed by L. helveticus ATCC 15807 was linked to NADH(2) oxidase activity rather than the acetate kinase enzyme.
authors.affiliation: Centro de Referencia para Lactobacilos (CERELA-CONICET), Chacabuco 145, S.M. de Tucumán, Tucumán 4000, Argentina.
authors.forename: M I
authors.initials: MI
authors.lastname: Torino
authors.forename: M P
authors.initials: MP
authors.lastname: Taranto
authors.forename: G
authors.initials: G
authors.lastname: Font de Valdez
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000093:Acetoin / Q000032:analysis; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D002072:Butylene Glycols / Q000032:analysis; D019343:Citric Acid / Q000378:metabolism*; D003931:Diacetyl / Q000032:analysis; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D052198:Lactobacillus helveticus / Q000254:growth & development / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism*
chemical_list: D002072:Butylene Glycols; D009097:Multienzyme Complexes; D019343:Citric Acid; D000255:Adenosine Triphosphate; D019802:Succinic Acid; D000093:Acetoin; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D007785:Lactose; D003931:Diacetyl; D019342:Acetic Acid