title: Impact of the hydrogen partial pressure on lactate degradation in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1.
abstract: In this study, the impact of the hydrogen partial pressure on lactate degradation was investigated in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1. To impose a change of the hydrogen partial pressure, formate was added to the reactor. Hydrogen results from the bioconversion of formate besides lactate in the liquid phase. In the presence of a hydrogen-consuming methanogen, this approach allows for a better estimation of low dissolved hydrogen concentrations than under conditions where hydrogen is supplied externally from the gas phase, resulting in a more accurate determination of kinetic parameters. A change of the hydrogen partial pressure from 1,200 to 250 ppm resulted in a threefold increase of the biomass-specific lactate consumption rate. The 50 % inhibition constant of hydrogen on lactate degradation was determined as 0.692 ± 0.064 μM dissolved hydrogen (831 ± 77 ppm hydrogen in the gas phase). Moreover, for the first time, the maximum biomass-specific lactate consumption rate of Desulfovibrio sp. G11 (0.083 ± 0.006 mol-Lac/mol-XG11/h) and the affinity constant for hydrogen uptake of Methanobrevibacter arboriphilus DH1 (0.601 ± 0.022 μM dissolved hydrogen) were determined. Contrary to the widely established view that the biomass-specific growth rate of a methanogenic coculture is determined by the hydrogen-utilizing partner; here, it was found that the hydrogen-producing bacterium determined the biomass-specific growth rate of the coculture grown on lactate and formate.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, The Netherlands, h.junicke-2@tudelft.nl.
authors.forename: H
authors.initials: H
authors.lastname: Junicke
authors.forename: H
authors.initials: H
authors.lastname: Feldman
authors.forename: M C M
authors.initials: MC
authors.lastname: van Loosdrecht
authors.forename: R
authors.initials: R
authors.lastname: Kleerebezem
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D001711:Biotransformation; D003470:Culture Media / Q000737:chemistry*; D003901:Desulfovibrio / Q000254:growth & development / Q000378:metabolism*; D005561:Formates / Q000378:metabolism; D006859:Hydrogen / Q000032:analysis*; D019344:Lactic Acid / Q000378:metabolism*; D041581:Methanobrevibacter / Q000254:growth & development / Q000378:metabolism*; D010313:Partial Pressure
chemical_list: D003470:Culture Media; D005561:Formates; C030544:formic acid; D019344:Lactic Acid; D006859:Hydrogen