Alternative Pathways of Acetogenic Ethanol and Methanol Degradation in the Thermophilic Anaerobe Thermacetogenium phaeum

Growth of the anaerobic thermophile Thermacetogenium phaeum with methanol, ethanol, ethanolamine, and acetate was investigated in axenic cultures and in syntrophic cultures with Methanothermobacter thermautotrophicus. Microcompartment genes were identified in the T. phaeum genome, and presence of microcompartments was confirmed by transmission electron microscopy and proteome analysis. These genes were expressed only during growth with ethanolamine. Proteome data were compared after growth with all four substrates, and activities of key enzymes of the Wood–Ljungdahl pathway and of enzyme systems leading to production or degradation of acetaldehyde such as alcohol dehydrogenase, aldehyde:ferredoxin oxidoreductase, acetate kinase, and phosphate acetyltransferase were measured in cytoplasmic fractions. Accounting of fermentation stoichiometries and growth yields with all four substrates showed that ethanol and methanol oxidation follow the same stoichiometries as in Acetobacterium woodii. On the other hand, the pathways of ethanol and methanol degradations vary between both organisms. Growth yields of T. phaeum were substantially lower than reported for A. woodii. Since T. phaeum has no Rnf complex encoded in its genome, the mechanisms of ATP synthesis have to be different from those of A. woodii. In addition to the central degradation pathways also found in A. woodii, T. phaeum maintains enzyme systems that compensate for the absence of an Rnf-complex but which on the other hand cause a loss of energy. On the basis of our data, pathways of methanol and ethanol degradation in T. phaeum are discussed

Effects of biochar on dry matter production and competitive ability of Rumex obtusifolius L.

Der Stumpfblättrige Ampfer (Rumex obtusifolius L.) ist ein gefürchtetes Unkraut im intensiv bewirtschafteten Grünland. In dieser Studie wurde untersucht, ob die Biokohle durch eine Verminderung des pflanzenverfügbaren N-Gehaltes im Boden für die Ampfer-Regulierung ein­gesetzt werden kann. Dazu wurde ein Gefäßversuch im Freien durchgeführt. Der Stumpfblättrige Ampfer und zwei Gräser, Italienisches Raygras (Lolium multiflorum) und Wiesen-Knaulgras (Dactylis glomerata), wuchsen in Reinkultur. R. obtusifolius wurde auch in Mischungen mit L. multiflorum angesät. Die Zufuhr von Biokohle zum Boden bewirkte eine Verminderung der Konzentration an N, S, Ca und Mg in der oberirdischen Phytomasse bei allen Arten. Dies dürfte auf einen Verdünnungseffekt zurückzuführen sein. Die K-Konzentration nahm nur beim Stumpfblättrigen Ampfer im Vergleich zur Kontrolle zu. Der höhere K-Gehalt im Boden infolge Biokohle-Zufuhr dürfte dafür verantwortlich sein. Beim Stumpfblättrigen Ampfer war K und nicht N das wachstumslimitierende Nährelement. Ein hoher pflanzenverfügbarer K-Gehalt im Boden dürfte die Massenvermehrung des Stumpfblätt­rigen Ampfers im Grünland deutlich fördern. Durch die Zufuhr von Biokohle und dem daraus resultierenden höheren K-Gehalt im Boden hat das durchschnittliche Spross-Trockengewicht beim Stumpfblättrigen Ampfer um 247%, beim Italienischen Raygras um 65% und beim Wiesen-Knaulgras um 108% im Vergleich zur Kontrolle zugenommen. Durch interspezifische Konkurrenz mit L. multiflorum wurde R. obtusifolius im Sprosswachstum deutlich gehemmt. Die Biokohle hat die Wettbewerbs­fähigkeit des Stumpfblättrigen Ampfers nicht vermindert und kann daher auch nicht zur Ampfer-Regulierung eingesetzt werden. Die vorliegenden Untersuchungsergebnisse können als Grundlage für vorbeugende Maßnahmen zur Ampfer-Regulierung dienen. DOI: 10.5073/JfK.2016.08.03, https://doi.org/10.5073/JfK.2016.08.03Rumex obtusifolius L. (broad-leaved dock) is one of the most troublesome weeds in intensively managed grassland. This study investigated the potential of biochar (BC), produced from woody green waste residues, to support its control. For this purpose, a pot experiment was conducted out of doors in Austria. It was expected that R. obtusifolius could be controlled by reducing available N content in the soil. R. obtusifolius and two grass species, Lolium multiflorum and Dactylis glomerata, were grown from seeds in monocultures, respectively. Moreover, R. obtusifolius was grown in mixtures with L. multiflorum. Due to a pure BC addition to soil (3% by wt), the concentrations of N, S, Ca and Mg in the shoot biomass decreased relative to the control in all three species, suggesting a dilution effect. The K concentration, however, increased only in R. obtusifolius, indicating its high absorp­tion capacity for K. In R. obtusifolius, K rather than N was the most growth-limiting nutrient element. The K level in soil appears to be important in controlling its distribution. To prevent Rumex infestation and/or to reduce existing infestations, a high soil K supply should be avoided. The average shoot dry weight of all three species was significantly higher when BC was applied (by 247%, 65% and 108%, in R. obtusifolius, L. multiflorum and D. glomerata, respectively), presumably because of a better K supply in soil. R. obtusifolius responded to interspecific competition with L. multiflorum by a density-dependent reduction of its shoot growth. BC did not decrease the competitive ability of Rumex in mixtures with Lolium. It is concluded that the addition of woody green waste BC to soil is no successful strategy for controlling R. obtusifolius in grassland. However, the results of this study can serve as a basis for preventive measures to Rumex control. DOI: 10.5073/JfK.2016.08.03, https://doi.org/10.5073/JfK.2016.08.0

Serious mismatches continue between science and policy in forest bioenergy

Abstract In recent years, the production of pellets derived from forestry biomass to replace coal for electricity generation has been increasing, with over 10 million tonnes traded internationally?primarily between United States and Europe but with an increasing trend to Asia. Critical to this trade is the classification of woody biomass as ?renewable energy? and thus eligible for public subsidies. However, much scientific study on the net effect of this trend suggests that it is having the opposite effect to that expected of renewable energy, by increasing atmospheric levels of carbon dioxide for substantial periods of time. This review, based on recent work by Europe's Academies of Science, finds that current policies are failing to recognize that removing forest carbon stocks for bioenergy leads to an initial increase in emissions. Moreover, the periods during which atmospheric CO2 levels are raised before forest regrowth can reabsorb the excess emissions are incompatible with the urgency of reducing emissions to comply with the objectives enshrined in the Paris Agreement. We consider how current policy might be reformed to reduce negative impacts on climate and argue for a more realistic science-based assessment of the potential of forest bioenergy in substituting for fossil fuels. The length of time atmospheric concentrations of CO2 increase is highly dependent on the feedstocks and we argue for regulations to explicitly require these to be sources with short payback periods. Furthermore, we describe the current United Nations Framework Convention on Climate Change accounting rules which allow imported biomass to be treated as zero emissions at the point of combustion and urge their revision to remove the risk of these providing incentives to import biomass with negative climate impacts. Reforms such as these would allow the industry to evolve to methods and scales which are more compatible with the basic purpose for which it was designed.Non peer reviewe

Anaerobic Microbial Degradation of Hydrocarbons: From Enzymatic Reactions to the Environment

Hydrocarbons are abundant in anoxic environments and pose biochemical challenges to their anaerobic degradation by microorganisms. Within the framework of the Priority Program 1319, investigations funded by the Deutsche Forschungsgemeinschaft on the anaerobic microbial degradation of hydrocarbons ranged from isolation and enrichment of hitherto unknown hydrocarbon-degrading anaerobic microorganisms, discovery of novel reactions, detailed studies of enzyme mechanisms and structures to process-oriented in situ studies. Selected highlights from this program are collected in this synopsis, with more detailed information provided by theme-focused reviews of the special topic issue on 'Anaerobic biodegradation of hydrocarbons' [this issue, pp. 1-244]. The interdisciplinary character of the program, involving microbiologists, biochemists, organic chemists and environmental scientists, is best exemplified by the studies on alkyl-/arylalkylsuccinate synthases. Here, research topics ranged from in-depth mechanistic studies of archetypical toluene-activating benzylsuccinate synthase, substrate-specific phylogenetic clustering of alkyl-/arylalkylsuccinate synthases (toluene plus xylenes, p-cymene, p-cresol, 2-methylnaphthalene, n-alkanes), stereochemical and co-metabolic insights into n-alkane-activating (methylalkyl) succinate synthases to the discovery of bacterial groups previously unknown to possess alkyl-/arylalkylsuccinate synthases by means of functional gene markers and in situ field studies enabled by state-of-the-art stable isotope probing and fractionation approaches. Other topics are Mo-cofactor-dependent dehydrogenases performing O-2-independent hydroxylation of hydrocarbons and alkyl side chains (ethylbenzene, p-cymene, cholesterol, n-hexadecane), degradation of p-alkylated benzoates and toluenes, glycyl radical-bearing 4-hydroxyphenylacetate decarboxylase, novel types of carboxylation reactions (for acetophenone, acetone, and potentially also benzene and naphthalene), W-cofactor-containing enzymes for reductive dearomatization of benzoyl-CoA (class II benzoyl-CoA reductase) in obligate anaerobes and addition of water to acetylene, fermentative formation of cyclohexanecarboxylate from benzoate, and methanogenic degradation of hydrocarbons

Enhanced oxygen-tolerance of the full heterotrimeric membrane-bound [NiFe]-hydrogenase of ralstonia eutropha.

Hydrogenases are oxygen-sensitive enzymes that catalyze the conversion between protons and hydrogen. Water-soluble subcomplexes of membrane-bound [NiFe]-hydrogenases (MBH) have been extensively studied for applications in hydrogen-oxygen fuel cells as they are relatively tolerant to oxygen, although even these catalysts are still inactivated in oxidative conditions. Here, the full heterotrimeric MBH of Ralstonia eutropha, including the membrane-integral cytochrome b subunit, was investigated electrochemically using electrodes modified with planar tethered bilayer lipid membranes (tBLM). Cyclic voltammetry and chronoamperometry experiments show that MBH, in equilibrium with the quinone pool in the tBLM, does not anaerobically inactivate under oxidative redox conditions. In aerobic environments, the MBH is reversibly inactivated by O2, but reactivation was found to be fast even under oxidative redox conditions. This enhanced resistance to inactivation is ascribed to the oligomeric state of MBH in the lipid membrane

Fermentation of 2,3-butanediol by Pelobacter carbinolicus sp. nov. and Pelobacter propionicus sp. nov. and evidence for propionate formation from C2 compounds

From anaerobic enrichments with 2,3-butanediol as sole substrate pure cultures of new Gram-negative, strictly anaerobic, non-sporeforming bacteria were isolated. Similar isolates were obtained with acetoin as substrate. From marine muds in saltwater medium a short rod (strain Gra Bd 1) was isolated which fermented butanediol, acetoin and ethylene glycol to acetate and ethanol. The DNA base ratio of this strain was 52.3 mol % guanine plus cytosine. From freshwater sediments and sewage sludge, a different type of short rod (strain Ott Bd 1) was isolated in freshwater medium, which fermented butanediol, acetoin, ethanol, lactate and pyrnvate stoichiometrically to acetate and propionate. Propanol and butanol were oxidized to the respective fatty acids with concomitant reduction of acetate and bicarbonate to propionate. The DNA base ratio of strain Ott Bd 1 was 57.4mo1~ guanine plus cytosine, No other substrates were used by the isolates, and no other products could be detected. In cocultures with Acetobacterium woodii or Methanospirillum hungatei, strain Gra Bd I also grew on ethanol, propanol, and butanol by fermenting these alcohols to the respective fatty acids and molecular hydrogen. Cytochromes could not be detected in any of the new isolates. Since both types of bacteria can not be affiliated to any of the existing genera and species, the new species Pelobacter carbinolicus and Pelobacter propionicus are proposed. The mechanism of butanediol degradation and propionate formation from acetate as well as the ecological importance of both processes are discussed