Kinetic and stoichiometric characterization of organoautotrophic growth of Ralstonia eutropha on formic acid in fed-batch and continuous cultures

Stephan Grunwald (1, 2) , Alexis Mottet (3) , Estelle Grousseau (3, 1) , Jens K Plassmeier (1) , Milan K Popovic (2) , Jean-Louis Uribelarrea (3) , Nathalie Gorret (3) , Stéphane Guillouet (3) , Anthony Sinskey (1, 4, 5)

1 Department of Biology
2 Department of Biotechnology
3 LISBP - Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés
4 Division of Health Sciences and Technology
5 Engineering Systems Division [Cambridge , USA]

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 Ralstoniaeutropha 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 ((max)=0.18h(-1)) and to study the impact of increasing formic acid concentrations on growth yields. High formic acid sensitivity was found in Reutropha since a linear decrease in the biomass yield with increasing residual formic acid concentrations was observed between 0 and 1.5gl(-1).

Domaines: Biotechnologies

Stephan Grunwald, Alexis Mottet, Estelle Grousseau, Jens K Plassmeier, Milan K Popovic, et al.. Kinetic and stoichiometric characterization of organoautotrophic growth of Ralstonia eutropha on formic acid in fed-batch and continuous cultures. Microbial Biotechnology, 2015, 8 (1), pp.155-163. ⟨10.1111/1751-7915.12149⟩. ⟨hal-01269231⟩