title: Possible occurrence of a Crabtree effect in the production of lactic and butyric acids by a floc-forming bacterial consortium.
abstract: Lactic and butyric acid production by bacterial flocs in a continuous culture obeyed different physiological constraints. The butyric acid rate of production was constant and independent of the growth rate [0.012 +/- 0.001 gBUT/(L.h)], whereas lactic fermentation occurred only beyond a critical growth rate (0.25 +/- 0.05 h(-1)) and was apparently associated with an abrupt drop in biomass. Principles of modeling used to describe a Crabtree effect in Saccharomyces cerevisiae were found to apply to lactic acid production by flocs. A rank of "physiological unit" (or "metabolic unit") can be attributed to the bacterial floc. From a practical point of view, the production of fermentation products by stable flocs, naturally resistant to contamination, opens the possibility of industrial production by continuous cultivation by using flocs-forming consortia.
authors.affiliation: Université Libre de Bruxelles, Faculté des Sciences-Section interfacultaire d' Agronomie, Laboratoire de Physiologie et Ecologie microbiennes (UPEM), Brussels, Belgium.
authors.forename: Jacques
authors.initials: J
authors.lastname: Thierie
authors.forename: Michel J
authors.initials: MJ
authors.lastname: Penninckx
mesh_terms: D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D020148:Butyric Acid / Q000378:metabolism*; D003013:Clostridium / Q000254:growth & development / Q000378:metabolism; D017753:Ecosystem; D004754:Enterobacter / Q000254:growth & development / Q000378:metabolism; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism; D005285:Fermentation; D005427:Flocculation; D005947:Glucose / Q000378:metabolism; D007218:Industrial Microbiology / Q000379:methods; D019344:Lactic Acid / Q000378:metabolism*; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism; D008954:Models, Biological; D010101:Oxygen Consumption; D011514:Proteus vulgaris / Q000254:growth & development / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000378:metabolism
chemical_list: D020148:Butyric Acid; D019344:Lactic Acid; D005947:Glucose