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•Pig manure and ensiled meadow grass were examined in co-digestion process.•Mechanical pretreatment increased the methane yield by 6.4%.•Coprothermobacter proteolyticus was firmly ...bounded to the digested grass.•Clostridium thermocellum was enriched in the firmly attached grass samples.•The abundance of methanogens was higher in the liquid fraction of digestate.
Mechanical pretreatment is considered to be a fast and easily applicable method to prepare the biomass for anaerobic digestion. In the present study, the effect of mechanical pretreatment on lignocellulosic silages biodegradability was elucidated in batch reactors. Moreover, co-digestion of the silages with pig manure in continuously fed biogas reactors was examined. Metagenomic analysis for determining the microbial communities in the pig manure digestion system was performed by analysing unassembled shotgun genomic sequences. A comparative analysis allowed to identify the microbial species firmly attached to the digested grass particles and to distinguish them from the planktonic microbes floating in the liquid medium. It was shown that the methane yield of ensiled grass was significantly increased by 12.3% due to mechanical pretreatment in batch experiments. Similarly, the increment of the methane yield in the co-digestion system reached 6.4%. Regarding the metagenomic study, species similar to Coprothermobacter proteolyticus and to Clostridium thermocellum, known for high proteolytic and cellulolytic activity respectively, were found firmly attached to the solid fraction of digested feedstock. Results from liquid samples revealed clear differences in microbial community composition, mainly dominated by Proteobacteria. The archaeal community was found in higher relative abundance in the liquid fraction of co-digestion experiment compared to the solid fraction. Finally, an unclassified Alkaliphilus sp. was found in high relative abundance in all samples.
Individual highly magnified stars have been recently discovered at lookback times of more than half the age of the universe, in lensed galaxies that straddle the critical curves of massive galaxy ...clusters. Having established their detectability, it is now important to carry out systematic searches for them in order to establish their frequency, and in turn learn about the statistical properties of high-redshift stars and of the granularity of matter in the foreground deflector. Here we report the discovery of a highly magnified star at redshift z = 0.94 in a strongly lensed arc behind a Hubble Frontier Field (HFF) galaxy cluster, MACS J0416.1-2403, discovered as part of a systematic archival search. The bright transient (dubbed "Warhol") was discovered in Hubble Space Telescope data taken on 2014 September 15 and 16. The point source faded over a period of two weeks, and observations taken on 2014 September 1 show that the duration of the microlensing event was at most four weeks in total. The magnified stellar image that exhibited the microlensing peak may also exhibit slow changes over a period of years at a level consistent with that expected for microlensing by the stars responsible for the intracluster light of the cluster. Optical and infrared observations taken near peak brightness can be fit by a stellar spectrum with moderate host-galaxy extinction. A blue supergiant matches the measured spectral energy distribution near peak, implying a temporary magnification of at least several thousand. The short timescale of the event and the estimated effective temperature indicate that the lensed source is an extremely magnified star. Finally, we detect the expected counterimage of the background lensed star at an offset by ∼0 1 in a deep coaddition of HFF imaging.
The core-collapse supernova of a massive star rapidly brightens when a shock, produced following the collapse of its core, reaches the stellar surface. As the shock-heated star subsequently expands ...and cools, its early-time light curve should have a simple dependence on the size of the progenitor
and therefore final evolutionary state. Measurements of the radius of the progenitor from early light curves exist for only a small sample of nearby supernovae
, and almost all lack constraining ultraviolet observations within a day of explosion. The several-day time delays and magnifying ability of galaxy-scale gravitational lenses, however, should provide a powerful tool for measuring the early light curves of distant supernovae, and thereby studying massive stellar populations at high redshift. Here we analyse individual rest-frame exposures in the ultraviolet to the optical taken with the Hubble Space Telescope, which simultaneously capture, in three separate gravitationally lensed images, the early phases of a supernova at redshift z ≈ 3 beginning within 5.8 ± 3.1 hours of explosion. The supernova, seen at a lookback time of approximately 11.5 billion years, is strongly lensed by an early-type galaxy in the Abell 370 cluster. We constrain the pre-explosion radius to be Formula: see text solar radii, consistent with a red supergiant. Highly confined and massive circumstellar material at the same radius can also reproduce the light curve, but because no similar low-redshift examples are known, this is unlikely.
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•Long term biological biogas upgrading reactor system was monitored.•Biogas upgrading performance reached 99% methane content after two-year operation.•Dominant methanogen changed ...from Methanoculleus sp. to Methanothermobacter sp.•Increment in abundance of homoacetogens was correlated to high acetate production.
Microbial dynamics in an upgrading biogas reactor system undergoing a more than two years-period at stable operating conditions were explored. The carbon dioxide generated during biomass degradation in the first reactor of the system was converted to methane into the secondary reactor by addition of external hydrogen. Considering the overall efficiency, the long-term operation period resulted in an improved biogas upgrading performance (99% methane content). However, a remarkable accumulation of acetate was revealed, indicating the enhancement of homoacetogenic activity. For this reason, a shift in the anaerobic digestion microbiome was expected and evaluated by 16S rRNA amplicon analysis. Results demonstrated that the most abundant archaeal species identified in the first time point, Candidatus Methanoculleus thermohydrogenotrophicum, was replaced by Methanothermobacter thermautotrophicus, becoming dominant after the community adaptation. The most interesting taxonomic units were clustered by relative abundance and six main long-term adaptation trends were found, characterizing functionally related microbes (e.g. homoacetogens).
•Bioaugmentation with Clostridium thermocellum and Melioribacter roseus was examined.•C. thermocellum enhanced the anaerobic biodegradability of wheat straw up to 34%.•M. roseus had limited ...efficiency and boosted the methane yield by only 11%.•C. thermocellum can be used to extract the residual methane of the reactor.•Bioaugmentation did not alter markedly the indigenous microbial communities.
Bioaugmentation with hydrolytic microbes was applied to improve the methane yield of bioreactors fed with agricultural wastes. The efficiency of Clostridium thermocellum and Melioribacter roseus to degrade lignocellulosic matter was evaluated in batch and continuously stirred tank reactors (CSTRs). Results from batch assays showed that C. thermocellum enhanced the methane yield by 34%. A similar increase was recorded in CSTR during the bioaugmentation period; however, at steady-state the effect was noticeably lower (7.5%). In contrast, the bioaugmentation with M. roseus did not promote markedly the anaerobic biodegradability, as the methane yield was increased up to 10% in batch and no effect was shown in CSTR. High-throughput 16S rRNA amplicon sequencing was used to assess the effect of bioaugmentation strategies on bacterial and archaeal populations. The microbial analysis revealed that both strains were not markedly resided into biogas microbiome. Additionally, the applied strategies did not alter significantly the microbial communities.
•Biological coupling of CO2 and H2 was evaluated in up-flow reactors.•Biomethanation efficiency was increased using Raschig rings as packing material.•Hydrogenotrophic community was majorly resided ...by Methanothermobacter methanogens.•Potential syntrophic acetate oxidizers were localized in the up-flow reactors.
Gas fermentation for the production of building block molecules and biofuels is lately gaining attention as a means to eliminate the greenhouse gases emissions. Especially CO2 capture and recycling are in focus. Thus, the biological coupling of CO2 and H2 is of high interest. Therefore, the focus of the present work was to evaluate the performances of two up-flow reactors for CO2 and H2 assimilation. Process monitoring showed that the gas-liquid H2 transfer was highly affected by reactor design. A reactor filled with Raschig rings could lift up gases utilization leading to a CH4 content of 81% at 6 h gas retention time and 8.8 L/LR.h gas recirculation rate. In contrast, limited biomethanation was achieved in the absence of Raschig rings highlighting the positive role of packing material to the performance of up-flow-reactors. Additionally, high-throughput 16S rRNA sequencing revealed that the microbial community was ultimately resided by Methanothermobacter methanogens.
Antarctica is the coldest and driest continent on Earth, characterized by polyextreme environmental conditions, where species adapted form complex networks of interactions. Microbial communities ...growing in these harsh environments can form biofilms that help the associated species to survive and thrive. A rich body of knowledge describes environmental biofilm communities; however, most studies have focused on dominant community members rather than functional complexity and metabolic potential. To overcome these limitations, the present study used genome-centric metagenomics to describe two biofilm samples subjected to different temperature collected in Deception Island, Maritime Antarctica. The results unraveled a complex biofilm microbiome represented by 180 metagenome-assembled genomes. The potential metabolic interactions were investigated using metabolic flux balance analysis and revealed that purple bacteria are the community members with the highest correlations with other bacteria. Due to their predicted mixotrophic behavior, they may play a crucial role in the microbiome, likely supporting the heterotrophic species in biofilms. Metatranscriptomics results revealed that the chaperone system and proteins counteracting ROS and toxic compounds have a major role in maintaining bacterial cell homeostasis in sediments of volcanic origin.
•Pb and temperature were the abiotic factors that strongly influenced the biofilm.•The two biofilms showed remarkable differences of bacterial growth types.•Results based on 164 metagenome assembled genomes showed a complex microbiome network.•Flux balance analysis revealed purple bacteria with highest number of correlations.•Metatranscriptomics showed that chaperon system is essential for cell homeostasis in the biofilm.
Enzymatic biofuel cells have employed a variety of fuels, including: glucose, fructose, methanol, ethanol, glycerol, lactate, pyruvate and ethylene glycol. This review describes the wealth of fuel ...diversity in enzymatic biofuel cells, along with the use of multi‐enzyme cascades for deep or complete oxidation of biofuels at the anode of enzymatic biofuel cells. Deep or complete oxidation is a relatively new research area for enzymatic biofuel cells, but it is necessary to increase energy density and minimize product inhibition effects.
Summary
Methanococcoides burtonii is a member of the Archaea that was isolated from Ace Lake in Antarctica and is a valuable model for studying cold adaptation. Low temperature transcriptional ...regulation of global gene expression, and the arrangement of transcriptional units in cold‐adapted archaea has not been studied. We developed a microarray for determing which genes are expressed in operons, and which are differentially expressed at low (4°C) or high (23°C) temperature. Approximately 55% of genes were found to be arranged in operons that range in length from 2 to 23 genes, and mRNA abundance tended to increase with operon length. Analysing microarray data previously obtained by others for Halobacterium salinarum revealed a similar correlation between operon length and mRNA abundance, suggesting that operons may play a similar role more broadly in the Archaea. More than 500 genes were differentially expressed at levels up to ∼24‐fold. A notable feature was the upregulation of genes involved in maintaining RNA in a state suitable for translation in the cold. Comparison between microarray experiments and results previously obtained using proteomics indicates that transcriptional regulation (rather than translation) is primarily responsible for controlling gene expression in M. burtonii. In addition, certain genes (e.g. involved in ribosome structure and methanogenesis) appear to be regulated post‐transcriptionally. This is one of few experimental studies describing the genome‐wide distribution and regulation of operons in archaea.
This research details the isolation and purification of a new type of lactate dehydrogenase that is dependent upon the coenzyme pyrroloquinoline quinone (PQQ). PQQ-dependent enzymes have been of ...interest in the literature over the last decade due to the fact that many of them can undergo direct electron transfer (DET) at electrode surfaces which is of interest for biosensor and biofuel cell applications. In the paper, we detail the isolation of PQQ-dependent lactate dehydrogenase (PQQ-LDH) from two sources of Gluconobacter (Gluconobacter sp. 33 and Gluconobacter suboxydans). This paper also shows the first evidence that PQQ-LDH can undergo direct electron transfer at gold and carbon electrode surfaces for future use in biosensors and biofuel cells.
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