Power-to-X (P2X) technologies will play a more important role in the conversion of electric power... more Power-to-X (P2X) technologies will play a more important role in the conversion of electric power to storable energy carriers, commodity chemicals and even food and feed. Among the different P2X technologies, microbial components form cornerstones of individual process steps. This review comprehensively presents the state-of-the-art of different P2X technologies from a microbiological standpoint. We are focusing on microbial conversions of hydrogen from water electrolysis to methane, other chemicals and proteins. We present the microbial toolbox needed to gain access to these products of interest, assess its current status and research needs, and discuss potential future developments that are needed to turn todays P2X concepts into tomorrow's technologies.
We present a simple protocol for the cost- and time-efficient profiling of methanogens based on T... more We present a simple protocol for the cost- and time-efficient profiling of methanogens based on T-RFLP fingerprinting of mcrA amplicons. Sequence data were compiled from mesophilic lab-scale and full-scale biogas reactors operated under various conditions and fed with various substrates. The database facilitates the rapid identification of methanogens, thus reducing the need of cloning and sequencing.
In order to better understand the effects of the substrate feeding regime on methanogenesis durin... more In order to better understand the effects of the substrate feeding regime on methanogenesis during anaerobic digestion in biogas reactors, four continuous stirred tank reactors operated under mesophilic conditions were investigated. In addition to standard physicochemical parameters, the stable isotopic signatures of CH4 and CO2 before and after daily feeding were analyzed. The activity of the methanogens was assessed by methyl coenzyme M reductase alpha-subunit (mcrA/mrtA) gene transcript analysis. Two different feeding regimes i.e. single vs. double consecutive feeding of the otherwise same daily maize silage load were investigated. During the first phase, a single feeding of the whole daily dose increased the biogas production within 70-80 min from around 0.5 to 2.0 L/h. This increase was associated with a transient increase of the acetic acid concentration and a corresponding decrease of the pH. Only moderate increase in biogas yield and VFA concentration (mainly acetate) was observed when the daily substrate was apportioned into two feedings. However, the overall daily gas production was similar in both cases. Regardless of the feeding regime, significantly depleted δ(13)CH4 and minor changes in the CO2 content of biogas were observed after feeding, which were followed by enrichment of δ(13)CH4. This period was associated with detectable changes in activity of methanogenic communities monitored by terminal restriction fragment length polymorphism analysis based on the transcripts of mcrA/mrtA genes. Methanoculleus and Methanobacterium spp. were the predominant methanogens in all reactors, while Methanosarcina spp. activity was only significant in two reactors. The activity of Methanoculleus and Methanosarcina spp. increased after the feeding in these reactors, which was followed by a depletion of δ(13)C in the produced gas. In both reactors, the less depleted isotopic values were detected before the second feeding, when Methanobacterium was the most active genus. Variations in reactor performance and methanogenic community characteristics were attributed to inoculum heterogeneity and stochastic factors during the reactor set up.
Power-to-X (P2X) technologies will play a more important role in the conversion of electric power... more Power-to-X (P2X) technologies will play a more important role in the conversion of electric power to storable energy carriers, commodity chemicals and even food and feed. Among the different P2X technologies, microbial components form cornerstones of individual process steps. This review comprehensively presents the state-of-the-art of different P2X technologies from a microbiological standpoint. We are focusing on microbial conversions of hydrogen from water electrolysis to methane, other chemicals and proteins. We present the microbial toolbox needed to gain access to these products of interest, assess its current status and research needs, and discuss potential future developments that are needed to turn todays P2X concepts into tomorrow's technologies.
We present a simple protocol for the cost- and time-efficient profiling of methanogens based on T... more We present a simple protocol for the cost- and time-efficient profiling of methanogens based on T-RFLP fingerprinting of mcrA amplicons. Sequence data were compiled from mesophilic lab-scale and full-scale biogas reactors operated under various conditions and fed with various substrates. The database facilitates the rapid identification of methanogens, thus reducing the need of cloning and sequencing.
In order to better understand the effects of the substrate feeding regime on methanogenesis durin... more In order to better understand the effects of the substrate feeding regime on methanogenesis during anaerobic digestion in biogas reactors, four continuous stirred tank reactors operated under mesophilic conditions were investigated. In addition to standard physicochemical parameters, the stable isotopic signatures of CH4 and CO2 before and after daily feeding were analyzed. The activity of the methanogens was assessed by methyl coenzyme M reductase alpha-subunit (mcrA/mrtA) gene transcript analysis. Two different feeding regimes i.e. single vs. double consecutive feeding of the otherwise same daily maize silage load were investigated. During the first phase, a single feeding of the whole daily dose increased the biogas production within 70-80 min from around 0.5 to 2.0 L/h. This increase was associated with a transient increase of the acetic acid concentration and a corresponding decrease of the pH. Only moderate increase in biogas yield and VFA concentration (mainly acetate) was observed when the daily substrate was apportioned into two feedings. However, the overall daily gas production was similar in both cases. Regardless of the feeding regime, significantly depleted δ(13)CH4 and minor changes in the CO2 content of biogas were observed after feeding, which were followed by enrichment of δ(13)CH4. This period was associated with detectable changes in activity of methanogenic communities monitored by terminal restriction fragment length polymorphism analysis based on the transcripts of mcrA/mrtA genes. Methanoculleus and Methanobacterium spp. were the predominant methanogens in all reactors, while Methanosarcina spp. activity was only significant in two reactors. The activity of Methanoculleus and Methanosarcina spp. increased after the feeding in these reactors, which was followed by a depletion of δ(13)C in the produced gas. In both reactors, the less depleted isotopic values were detected before the second feeding, when Methanobacterium was the most active genus. Variations in reactor performance and methanogenic community characteristics were attributed to inoculum heterogeneity and stochastic factors during the reactor set up.
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Papers by Marcell Nikolausz