Abstract
Bioprocesses converting carbon dioxide with molecular hydrogen to methane (CH4) are currently being developed to enable a transition to a renewable energy production system. In this study, we present a comprehensive physiological and biotechnological examination of 80 methanogenic archaea (methanogens) quantifying growth and CH4 production kinetics at hyperbaric pressures up to 50 bar with regard to media, macro-, and micro-nutrient supply, specific genomic features, and cell envelope architecture. Our analysis aimed to systematically prioritize high-pressure and high-performance methanogens. We found that the hyperthermophilic methanococci Methanotorris igneus and Methanocaldococcoccus jannaschii are high-pressure CH4 cell factories. Furthermore, our analysis revealed that high-performance methanogens are covered with an S-layer, and that they harbour the amino acid motif Tyrα444 Glyα445 Tyrα446 in the alpha subunit of the methyl-coenzyme M reductase. Thus, high-pressure biological CH4 production in pure culture could provide a purposeful route for the transition to a carbon-neutral bioenergy sector.
Highlights
Bioprocesses converting carbon dioxide with molecular hydrogen to methane (CH4) are currently being developed to enable a transition to a renewable energy production system
Most biogenic CH4 is emitted by methanogenic archaea[2], with minor amounts originating from cyanobacteria[3] and marine microorganisms[4]
Pure culture CO2-BMP is regarded as a key technology combining chemical energy storage, CO2 utilization and biofuel production
Summary
Bioprocesses converting carbon dioxide with molecular hydrogen to methane (CH4) are currently being developed to enable a transition to a renewable energy production system. Methanogens convert short chain organic acids and one-carbon compounds to CH4 through their energy and carbon metabolism[2,5,6] Their metabolic capability is important for anaerobic organic matter degradation in environments with low concentrations of sulfate, nitrate, manganese, or iron[5]. Ex situ pure culture biomethanation exhibits high volumetric CH4 productivity and offers a straightforward bioprocess control by utilizing biochemically and biotechnologically well-characterized microorganisms in pure culture[12]. The CO2-BMP bioprocess can be operated as a gas transfer limited process[12] when a proper feeding strategy is applied[24] In this case, the kinetic limiting step is the mass transfer of H2 to the liquid phase. The influence of pressure on substrate uptake, growth, and production kinetics of methanogens is an important parameter in CO2-BMP. A systematic biotechnological survey with regard to nutritional demands of methanogens across different temperature regimes in the same cultivation conditions and at different pressure levels has not yet been the focus of any study
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