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.

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

“…One interpretation of the broad scope of the phenotypic changes occurring in response to the cooA deletion is that central metabolism has been perturbed. Possibly hydrogen oxidation (part of the "hydrogen transient" when D. vulgaris is grown with organic acids (Noguera et al, 1998)) could be preferentially inhibited by CO causing an increase in hydrogen concentration that prohibits lactate degradation, already thermodynamically unfavourable ( Junicke, Feldman, van Loosdrecht, & Kleerebezem, 2014). Rajeev and co-workers successfully complemented the deletion of cooA with a wild-type cooA encoded on a plasmid restoring growth with lactate/sulphate in the presence of CO .…”

Limitation of syntrophic coculture growth by the acetogen

“…This study showed experimental evidence for the previously formulated concept by Junicke et al () that the acetogen can be the growth‐limiting partner in a syntrophic methanogenic coculture on lactate. This defined coculture study, illustrates the need for an accurate measurement of individual biomass amounts, as otherwise the distribution of biomass‐specific fluxes would lack a final proof.…”

“…To investigate whether the partial reactions shown in Table are thermodynamically favorable under the prevailing experimental conditions, the actual Gibbs energy change (Δ G 1 ) was calculated according to where Δ G 01 is the Gibbs energy change at 310.15 K and pH 7.0, Y i denotes the stoichiometric coefficient and c i the concentration of compound i. T denotes the temperature in Kelvin and R the gas constant (8.314 J/K/mol). A more detailed model description is given in Junicke et al ().…”

“…The q Form,max,G11 was taken as 0.175 ± 0.018 mol‐Form/mol‐ X G11 /h and was obtained from a coculture of Desulfovibrio sp. G11 and non‐formate utilizing Methanobrevibacter arboriphilus DH1 on lactate and formate (Junicke et al, ).…”

“…A recent study, indicated that the acetogen limited biomass‐specific growth rate in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1 on lactate and formate (Junicke et al, ). These findings were based on a yield‐based model but individual biomass concentrations were not measured, and thus, final experimental proof is still lacking.…”