title: Kinetic and stoichiometric characterization of organoautotrophic growth of Ralstonia eutropha on formic acid in fed-batch and continuous cultures.
abstract: Formic acid, acting as both carbon and energy source, is a safe alternative to a carbon dioxide, hydrogen and dioxygen mix for studying the conversion of carbon through the Calvin-Benson-Bassham (CBB) cycle into value-added chemical compounds by non-photosynthetic microorganisms. In this work, organoautotrophic growth of Ralstonia eutropha on formic acid was studied using an approach combining stoichiometric modeling and controlled cultures in bioreactors. A strain deleted of its polyhydroxyalkanoate production pathway was used in order to carry out a physiological characterization. The maximal growth yield was determined at 0.16 Cmole Cmole(-1) in a formate-limited continuous culture. The measured yield corresponded to 76% to 85% of the theoretical yield (later confirmed in pH-controlled fed-batch cultures). The stoichiometric study highlighted the imbalance between carbon and energy provided by formic acid and explained the low growth yields measured. Fed-batch cultures were also used to determine the maximum specific growth rate (μmax  = 0.18 h(-1) ) and to study the impact of increasing formic acid concentrations on growth yields. High formic acid sensitivity was found in R eutropha since a linear decrease in the biomass yield with increasing residual formic acid concentrations was observed between 0 and 1.5 g l(-1) .
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Bldg. 68-370, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA; Department of Biotechnology, Beuth Hochschule für Technik Berlin, 13353, Berlin, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Grunwald
authors.forename: Alexis
authors.initials: A
authors.lastname: Mottet
authors.forename: Estelle
authors.initials: E
authors.lastname: Grousseau
authors.forename: Jens K
authors.initials: JK
authors.lastname: Plassmeier
authors.forename: Milan K
authors.initials: MK
authors.lastname: Popović
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Uribelarrea
authors.forename: Nathalie
authors.initials: N
authors.lastname: Gorret
authors.forename: Stéphane E
authors.initials: SE
authors.lastname: Guillouet
authors.forename: Anthony
authors.initials: A
authors.lastname: Sinskey
mesh_terms: D052818:Autotrophic Processes; D019149:Bioreactors / Q000382:microbiology*; D020118:Cupriavidus necator / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*; D005561:Formates / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D054813:Polyhydroxyalkanoates / Q000378:metabolism
chemical_list: D005561:Formates; D054813:Polyhydroxyalkanoates; C030544:formic acid