C1 Compounds Research Articles

Obtaining C2 and C3 Products from Methane Using Pd/C as Anode in a Solid Fuel Cell‐type Electrolyte Reactor

AbstractMethane was converted into C2 and C3 products under mild conditions using a single stage solid electrolyte reactor, using a proton exchange membrane fuel cell as a SER‐FC and Pd/C as an electrocatalyst prepared by the reduction method of sodium borohydride. This electrocatalyst has a cubic pattern of palladium centered on the face and an average size of nanoparticles close to 6.4 nm, according to the literature. Differential mass spectrometry reveals the chemical profile of species obtained from the oxidation of methane with ionic currents (Ii) at m/z=16, 28, 30, 32, 44, 46 and 60. In many cases, Ii can be assigned to more than one species; therefore, complementary ATR‐FTIR experiments were performed. The ATR‐FTIR spectra confirmed the presence of C2 and C3 compounds such as ethane, ethanol, acetaldehyde, acetic acid and propane. Considering the low amount of water in the reaction medium, these results may be associated with the use of Pd/C electrocatalysts responsible for the activation of the water molecule.

Genome sequencing and flavor compound biosynthesis pathway analyses of Bacillus licheniformis isolated from Chinese Maotai-flavor liquor-brewing microbiome

ABSTRACT Maotai- flavor liquor is one of the most popular distilled liquors in China that contains various flavor substances produced by a specialized brewing microbiome. Bacillus licheniformis is one of the major bacterial species in the Maotai-flavor liquor-brewing microbiome. However, the whole genome sequence of the B. licheniformis brewing strain has not been reported, which hampers further understanding of its effects on brewing. In this study, whole genome sequencing of B. licheniformis MT-B06 isolated from Maotai Daqu, a fermented wheat starter containing brewing microorganisms, was carried out using the Pacific Bioscience RS II platform. The sequence had a length of 4,440,765 bp with 45.7% GC content, encoding 5023 CDS sequences, 81 tRNAs, and 24 rRNAs. Next, genome annotation was performed based on four high-quality databases, including the COG, KEGG, GO/IPR, and Swiss-Prot databases. The genome sequence obtained was comparatively analyzed with that of B. licheniformis ATCC 14580, which is used for industrial enzyme production, which revealed that 69.95% of the differential genes are metabolically related, suggesting that these genes may be closely related to the flavor compounds biosynthesis. Therefore, the flavor compounds biosynthesis pathways and 26 relevant genes of B. licheniformis MT-B06 was analyzed, including alsS and alsD for 3-hydroxy-2-butanone synthesis, ispD, and ispE for terpenoids synthesis. This is the first report of high-quality whole genome sequencing of B. licheniformis MT-B06. Our results provide an important foundation for investigating metabolic pathways of desired compounds, such as C4 compounds and pyrazines, in Maotai-flavor liquor to improve its taste and quality.

Nanosized palladium loaded on porous ceria: A three-dimensional boosted electrocatalyst for electrooxidation of C1 compounds

The solution combustion synthesis was used for preparation of porous CeO2 with two different fuels; glucose and citric acid, for combustion. The samples of porous CeO2 are labeled as PCOGlu and PCOCit. The surface area of PCOCit and PCOGlu were estimated as 44.50 ± 0.12, and 47.72 ± 0.16 m2 g−1, respectively. The cavities acidity, OH groups on surface, and its bond strength to the active cerium sites are compared by measuring the pH of zero charges; that it was 11.95 ± 0.02, and 11.90 ± 0.03 for PCOCit and PCOGlu, respectively. The nanosized palladium (NPd) was loaded on PCOGlu and PCOCitvia wetness incorporation. As-prepared nano-microstructure electrocatalysts are utilized in the electrooxidation of C1 compounds, including methanol, formaldehyde, and formic acid. The NPd-PCOGlu presents higher electrocatalytic activity, stability and CO-tolerance ability for the electrooxidation of C1 compounds as compared to the NPd-PCOCit and NPd as non-supported palladium; So that, the performance of the modified electrodes increase in the order of NPd < NPd-PCOCit < NPd-PCOGlu. The PCO with porous structural network affected on the electrochemical surface area, dispersion, and durability of NPd. It is effective the capability of removing the poisoning species of the electrooxidation of C1 compounds on NPd through the lattice oxygen, and the activation of an oxidation−reduction cycle between the high and low chemical valences of cerium, leading to improve the electrocatalytic efficiency of NPd. Lastly, the conversion of methanol to formaldehyde, and then to formic acid during electrooxidation is confirmed by using cyclic voltammetry.

Comparative Study of Different Acidic Surface Structures in Solid Catalysts Applied for the Isobutene Dimerization Reaction.

Dimerization of isobutene (IBE) to C8s olefins was evaluated over a range of solid acid catalysts of diverse nature, in a fixed bed reactor working in a continuous mode. All catalytic materials were studied in the title reaction performed between 50–250 °C, being the reaction feed a mixture of IBE/helium (4:1 molar ratio). In all materials, both conversion and selectivity increased with increasing reaction temperature and at 180 °C the best performance was recorded. Herein, we used thermogravimetry analysis (TGA) and temperature programmed desorption of adsorbed ammonia (NH3-TPD) for catalysts characterization. We place emphasis on the nature of acid sites that affect the catalytic performance. High selectivity to C8s was achieved with all catalysts. Nicely, the catalyst with higher loading of Brønsted sites displayed brilliant catalytic performance in the course of the reaction (high IBE conversion). However, optimum selectivity towards C8 compounds led to low catalyst stability, this being attributed to the combined effect between the nature of acidic sites and structural characteristics of the catalytic materials used. Therefore, this study would foment more research in the optimization of the activity and the selectivity for IBE dimerization reactions.

Foliar application of phenylalanine plus methyl jasmonate as a tool to improve Grenache grape aromatic composition

The aromas of the grape are compounds that are directly related to the quality of the must and the wine. In this work, the effect of foliar application of phenylalanine (Phe), methyl jasmonate (MeJ) and a mixture of both (Phe + MeJ) on the content of volatile compounds in grapes of the Grenache variety has been studied. The results showed that the most effective treatment in order to improve the content of terpenoids and C13 norisoprenoids was MeJ; while, for enhancement of the benzenoid compounds and the total positive compounds was Phe. In the case of terpenoids and benzenoids, the treatment based on Phe + MeJ was the one that most potentiated their increase. C6 compounds, which contribute to the wine herbaceous aromas considered as negative, did not increase with any treatment. In conclusion, all treatments applied in the vineyard improved the content of volatile compounds in grapes of Grenache variety.

Supported Cobalt Catalysts for Acceptorless Alcohol Dehydrogenation.

The acceptor-less dehydrogenation of 2-octanol was tested over cobalt supported on Al2 O3 , C, ZnO, ZrO2 and various TiO2 substrates. The catalysts were characterized by ICP, XRD and TGA-H2 . For Co/TiO2 P25, the effects of passivation, aging (storage at room temperature), and in situ activation under H2 were investigated. The catalysts must be tested shortly after synthesis in order to prevent deactivation. Cobalt supported on TiO2 P25 was the most active and 69 % yield of 2-octanone was obtained, using decane as a solvent. Selectivities for 2-octanone were observed in the range of 90 % to 99.9 %. Small amounts of C16 compounds were also formed due to aldol condensation/dehydration reactions. The catalysts exhibited higher conversion in the dehydrogenation of secondary alcohols (65-69 %), in comparison to primary alcohols (2-10 %). The dehydrogenation of 1,2-octanediol led to 1-hydroxy-2-octanone, with a selectivity of 90 % and 69 % for Co/TiO2 P25 and Co/TiO2 P90, respectively.

From Extra Virgin Olive Oil to Refined Products: Intensity and Balance Shifts of the Volatile Compounds versus Odor.

To explore relationships between the volatile organic compounds (VOCs) of different grades of olive oils (OOs) (extra virgin olive oil (EVOO), refined olive oil (ROO), and pomace olive oil (POO)) and odor quality, VOCs were measured in the headspace of the oils by proton transfer reaction quadrupole ion guide time-of-flight mass spectrometry. The concentrations of most VOCs differed significantly between the grades (EVOO > ROO > POO), whereas the abundance of m/z 47.012 (formic acid), m/z 49.016 (fragments), m/z 49.027 (fragments), and m/z 115.111 (heptanal/heptanone) increased in that order. Although the refined oils had considerably lower VOC abundance, the extent of the decline varied with the VOCs. This results in differences in VOCs proportions. The high VOC abundance in the EVOO headspace in comparison to ROO and POO results in a richer and more complex odor. The identified C5–C6 compounds are expected to contribute mainly to the green odor notes, while the identified C1–C4 and C7–C15 are mainly responsible for odor defects of OOs. Current results reveal that processing strongly affects both the quantitative and relative abundance of the VOCs and, therefore, the odor quality of the various grades of OOs.

Genome diversification in globally distributed novel marine Proteobacteria is linked to environmental adaptation

Proteobacteria constitute one of the most diverse and abundant groups of microbes on Earth. In productive marine environments like deep-sea hydrothermal systems, Proteobacteria are implicated in autotrophy coupled to sulfur, methane, and hydrogen oxidation, sulfate reduction, and denitrification. Beyond chemoautotrophy, little is known about the ecological significance of poorly studied Proteobacteria lineages that are globally distributed and active in hydrothermal systems. Here we apply multi-omics to characterize 51 metagenome-assembled genomes from three hydrothermal vent plumes in the Pacific and Atlantic Oceans that are affiliated with nine Proteobacteria lineages. Metabolic analyses revealed these organisms to contain a diverse functional repertoire including chemolithotrophic ability to utilize sulfur and C1 compounds, and chemoorganotrophic ability to utilize environment-derived fatty acids, aromatics, carbohydrates, and peptides. Comparative genomics with marine and terrestrial microbiomes suggests that lineage-associated functional traits could explain niche specificity. Our results shed light on the ecological functions and metabolic strategies of novel Proteobacteria in hydrothermal systems and beyond, and highlight the relationship between genome diversification and environmental adaptation.

RETRACTED: Characterization of the volatile profile of virgin olive oils of Koroneiki and Cypriot cultivars, and classification according to the variety, geographical region and altitude

Abstract This study aims to the investigation of the effects of the geographical region and the botanical origin of olive oils on the profile of volatile compounds (VCs) isolated from monovarietal virgin olive oils (VOOs) from Cypriot, and Koroneiki varieties cultivated in Cyprus in order to establish, for the first time, promising models for botanical and geographical classification. Sixty-four compounds were determined by HS-SPME, GC/MS for one hundred forty VOOs, and statistical analysis of data was performed using LDA and multivariate/univariate ANOVA. Successful categorization, up to 89.3% for the varieties, and 67.9% regarding the altitude classes were obtained. The results showed new markers for the classification of the VOOs according to variety, such as 1-methoxyhexane, and the group C5 compounds, (E)-2-dodecene+(E)-β-ocimene, 3-(4-methyl-3-pentenyl)furan+(E)-4,8-dimethyl-1,3,7nonatriene, which, along with hexyl acetate, group of esters and hydrocarbons exhibited the highest discriminant power among all volatiles/groups based on the different proportions found in VOOs.

Analysis of the Complete Genome Sequence of Strain Concept-8, a Novel Representative of the Genus Methylococcus

The complete genome sequence of a thermotolerant obligate methanotroph Methylococcus sp. Concept-8 was determined and analyzed. This strain was obtained by long-term storage, selection, and purification of an industrial culture of Methylococcus capsulatus BSV-874, which was used for methane-based protein biosynthesis in the Soviet Union. The size of the Concept-8 genome is 3.46 Mb. Genome annotation identified 3266 open reading frames that encode proteins. The closest phylogenetic relative of strain Concept-8 is Methylococcus capsulatus Bath (98.7% identity of 16S rRNA gene sequences). Comparison of the genomic sequences of these methanotrophs revealed 88.39% average nucleotide sequence identity, indicating that Concept-8 represents a novel species of the genus Methylococcus. The genomes of the strains Bath and Concept-8 both contain two copies of rRNA operons and pmoBAC operons for particulate methane monooxygenase, as well as a single copy of the soluble methane monooxygenase operon mmoXYBZDC. Growth on methanol was possible due to the presence of two complementary methanol dehydrogenases: MxaFJGIRACKLD and XoxF. The two methanotrophs also possess highly similar sets of genes encoding enzymes of the major pathways of the metabolism of C1 compounds. The genome of Methylococcus sp. Concept-8 was found to contain two regions associated with prophages of the family Siphoviridae. The prophage regions detected in the genome of Mc. capsulatus Bath are also homologous to viral sequences of the family Siphoviridae but differ from those identified in the genome of Concept-8.

Qualitative effects of the addition of withered grapes to a freshly produced red wine: the traditional governo all'uso toscano practice

Background and Aims Governo all'uso toscano (GUT) is a traditional winemaking practice where withered grapes are added to a freshly fermented wine. This results in a second alcoholic fermentation and a distinctive wine, in which there is renewed interest. Grape withering is problematic for winemakers, however, both in terms of cost and risks. It is therefore important to determine the minimum amount of withered grapes needed to typify the wine in order to minimise risks and costs. Methods and Results During the trials, Sangiovese grapes were withered for 2 months in a dedicated room, a ‘fruttaio’, with a resulting mass loss of about 40%. Afterwards, withered grapes (5–20% berry mass/wine mass) were added to a Control wine to reproduce the GUT procedure. The GUT technique significantly changed the chemical profile of the wines. Ethanol, colour intensity and hue increased, while acidity decreased. Malolactic fermentation occurred simultaneously with the second alcoholic fermentation in all GUT wines, but not in the Control wines. The GUT practice significantly changed the volatile profile, including the concentration of several primary grape compounds, such as aromatic alcohols, C6 compounds and terpenoids, and of several fermentation compounds. Conclusion Under the experimental conditions, the optimal amount of withered grapes added to the base wine was 5%. Significance of the Study The study described the oenological effects of GUT and the optimisation of the amount of withered grapes required to make a wine with this characteristic winemaking practice clearly recognisable.

Electrochemical CO2 reduction reaction on cost-effective oxide-derived copper and transition metal–nitrogen–carbon catalysts

Abstract The electrochemical CO2 reduction reaction (CO2RR) either to generate multicarbon (C2+) or single carbon (C1) value-added products provides an effective and promising approach to mitigate the high CO2 concentration in the atmosphere and promote energy storage. However, cost-effectiveness of catalytic materials limits practical application of this technology in the short term. Herein, we summarize and discuss recent and advanced works on cost-effective oxide-derived copper catalysts for the generation of C2+ products (hydrocarbons and alcohols) and transition metal–nitrogen–doped carbon electrocatalytic materials for C1 compounds production from CO2RR. We think they represent suitable electrocatalyst candidates for scaling up electrochemical CO2 conversion. This short review may provide inspiration for the future design and development of innovative active, cost-effective, selective and stable electrocatalysts with improved properties for either the production of C2+ (alcohols, hydrocarbons) or carbon monoxide from CO2RR.

Changes in the volatile profile of ‘Fantasia’ nectarines [Prunus persica (L.) Batsch, var. nectarina] treated with an enhanced freshness formulation (EFF) containing hexanal

Postharvest technologies play a key role in enhancing shelf life and maintaining quality characteristics of tender fruits, such as nectarines (Prunus persica [L.] Batsch var. nectarina). This research investigated the effects of an enhanced freshness formulation (EFF), containing hexanal as the key ingredient, in enhancing the shelf life of field grown nectarines and its effects on the composition of volatile organic compounds (VOCs). ‘Fantasia’ nectarine fruits at two commercial orchards in the Niagara region were subject to preharvest sprays of 2% EFF (15 and 7 days preharvest) and stored at ambient conditions (25 °C) with volatile analyses conducted at 0, 3, 5, 7, and 11 days postharvest. The volatile analysis study indicated for the first time that hexanal is naturally present in nectarine fruit. This was confirmed by GC–MS analysis and validated with standards. GC–EIMS analyses of targeted VOCs validated with standards indicated reduced levels of VOCs associated with fruit ripening and fruity odor, such as lactones, in hexanal-treated fruit, and an increased level of C6 compounds associated with unripe fruit. Principal component analysis biplot with scores and loadings of the fruit VOCs and quality parameters indicated a tight association between TSS and lactones, which was inversely associated with firmness, ground color, acetates, and ester compounds. Pearson correlation coefficients also indicated a very high positive correlation between hexanal and levels of VOCs, such as 1-hexanol, E-2-hexanal, 3-hexanal, hexen-1-ol, and other C6 acetates. These findings may indicate a delay in the ripening process caused by hexanal formulation, which may be associated with modulated expression of key ripening-related volatile pathways, therefore enhancing the shelf life and quality of nectarines.

Coenzyme Coupling Boosts Charge Transport through Single Bioactive Enzyme Junctions.

SummaryOxidation of formate to CO2 is catalyzed via the donation of electrons from formate dehydrogenase (FDH) to nicotinamide adenine dinucleotide (NAD+), and thus the charge transport characteristics of FDH become essential but remain unexplored. Here, we investigated the charge transport through single-enzyme junctions of FDH using the scanning tunneling microscope break junction technique (STM-BJ). We found that the coupling of NAD+ with FDH boosts the charge transport by ∼2,100%, and the single-enzyme conductance highly correlates with the enzyme activity. The combined flicker noise analysis demonstrated the switching of the coenzyme-mediated charge transport pathway and supported by the significantly reduced HOMO-LUMO gap from calculations. Site-specific mutagenesis analysis demonstrated that FDH-NAD+ stably combined own higher bioactivity and boosts charge transport, and the coupling has been optimized via the natural selection. Our work provides evidence of hydrogen bond coupling in bioactivity but also bridges the charge transport through single-enzyme junctions and enzyme activities.

Dry Reforming of Methane under Mild Conditions Using Radio Frequency Plasma

Dry reforming of methane (DRM) is a challenging process wherein methane reacts with CO2 to give syngas. This reaction is strongly endothermic, typically requiring temperatures higher than 500 °C. Catalysts can be used, but the high temperatures (which are a thermodynamic requirement) often lead to catalyst deactivation. Herein, the reaction from another conceptual direction is approached, using low‐power radio frequency inductively coupled plasma (RF‐ICP). It is demonstrated that this system can give high conversions of methane and CO2 at near‐ambient temperatures. Importantly, the energy costs in this system are considerably lower compared with other plasma‐driven DRM processes. Furthermore, it is shown that the yield of hydrogen can be increased by minimizing the C2 compound formation. The factors that govern the DRM process and discuss Hα emission and its influence on H atom recycling in the process are examined.

Antioxidant activity of flavonoid compounds isolated from the petals of Hibiscus rosa sinensis

Hibiscus rosasinensis, medicinal plant known for its various medicinal properties. The present study was to identify and characterize the flavonoid compound from the petals of Hibiscus rosa sinensis. The antioxidant compounds were isolated by Silica Gel G Column chromatography. From the fractions, C5 shows the highest antioxidant activity compared to C3 & C4 compounds. DNA damage protection activity results indicated that two major bands super coiled DNA and open circular DNA was protected by the presence of different concentration (5 µg, 10 µg, 15 µg & 20 µg) of C5 compound isolated from the petals of Hibiscus rosa sinensis. IR absorptions peaks reveals the presence of functional groups alcohols, phenols, α,β unsaturated aldehyes, ketones and alkanes. The structure of compound was characterized as Hibiscetin-3-glucoside (C21H20O14) by Mass spectroscopy and NMR. The study emphasized flavanoid compounds have effective scavenging activities which may be due to its phenolics and flavonoid contents and can be used as anticancer agents.

Bioactive Sterol Derivatives Isolated from the Pleurotus djamor var. Roseus Induced Apoptosis in Cancer Cell Lines.

The aim of the present study is to isolate and characterize the bioactive compounds from Pleurotus djamor against human breast cancer (MDA-MD-231) and mouse T cell lymphoma (EL4) cell lines. Sequential fractionization and column chromatography methods were involved in compound isolation. The structures of the isolated compound were determined by NMR, GC/MS, and X-ray crystallography studies. The isolated compounds 1- 4 [D-mannitol (C1), ergosta-5,7,22-trien-3β-ol (C2), 5,8- epidioxy-ergosta-6-22-dien-3β-ol (C3), and palmitic acid (C4)] are white crystal and amorphous powder in nature. All these compounds were isolated from this mushroom for the first time. In vitro lipid peroxidation activities of isolated compounds were determined by ferric thiocyanate (FTC) and thiobarbituric acid (TBA) method. The sterol derivatives C2 and C3 compounds displayed strong antioxidant activity and were not significantly different (p<0.05) to α-tocopherol. This finding elaborates on the isolation of a cytotoxic compound C2 and C3 from P. djamor via a rapid elution method. The compound C3 has exhibited better cytotoxic activity against MDA-MD-231 and EL4 cells. The present finding and data might provide new insights into the possible therapeutic and pharmaceutical use for the design of anti-cancer drugs from this edible mushroom.

Complete genome sequence of Paracoccus sp. strain AK26: Insights into multipartite genome architecture and methylotropy

The present study reports the functional annotation of complete genome of methylotrophic bacterium Paracoccus sp. strain AK26. The 3.6 Mb genome with average GC content of 65.7% was distributed across five replicons; including chromosome (2.7 Mb) and four extrachromosomal replicons pAK1 (471Kb), pAK2 (189Kb), pAK3 (129Kb) and pAK4 (84 Kb). Interestingly, nearly 23% of the Cluster of Orthologous Group (COG) of proteins were annotated on extrachromosomal replicons and 185Kb genome content was attributed to segregated 19 genomic island regions. Among the four replicons, pAK4 was identified as essential and integral part of the genome, as supported by codon usage, GC content (66%) and synteny analysis. Comparative genome analysis for methylotrophy showed mechanistic variations in oxidation and assimilation of C1 compounds among closely related Paracoccus spp. Collectively, present study reports the functional characterization and genomic architecture of strain AK26 and provides genetic basis for quinone and isoprenoid based secondary metabolites synthesis using strain AK26.

Isotopic evidence for quasi-equilibrium chemistry in thermally mature natural gases

Natural gas is a key energy resource, and understanding how it forms is important for predicting where it forms in economically important volumes. However, the origin of dry thermogenic natural gas is one of the most controversial topics in petroleum geochemistry, with several differing hypotheses proposed, including kinetic processes (such as thermal cleavage, phase partitioning during migration, and demethylation of aromatic rings) and equilibrium processes (such as transition metal catalysis). The dominant paradigm is that it is a product of kinetically controlled cracking of long-chain hydrocarbons. Here we show that C2+n-alkane gases (ethane, propane, butane, and pentane) are initially produced by irreversible cracking chemistry, but, as thermal maturity increases, the isotopic distribution of these species approaches thermodynamic equilibrium, either at the conditions of gas formation or during reservoir storage, becoming indistinguishable from equilibrium in the most thermally mature gases. We also find that the pair of CO2 and C1 (methane) exhibit a separate pattern of mutual isotopic equilibrium (generally at reservoir conditions), suggesting that they form a second, quasi-equilibrated population, separate from the C2 to C5 compounds. This conclusion implies that new approaches should be taken to predicting the compositions of natural gases as functions of time, temperature, and source substrate. Additionally, an isotopically equilibrated state can serve as a reference frame for recognizing many secondary processes that may modify natural gases after their formation, such as biodegradation.

Coupling of CH4 to C2 Hydrocarbons in a Packed Bed DBD Plasma Reactor: The Effect of Dielectric Constant and Porosity of the Packing

The conversion of methane was investigated in a packed-bed dielectric barrier discharge (DBD) plasma reactor operated at ambient conditions. High dielectric BaTiO3 was utilized as packing in comparison with γ-alumina, α-alumina, and silica-SBA-15. Results show a considerably lower conversion of CH4 and C2 yield for the BaTiO3 packed reactor, which is even less than that obtained for the nonpacked reactor. In contrast, the low dielectric alumina (γ and α) packed reactor improved the conversion of CH4 and C2 yield. Additionally, the alumina packed reactor shifted the distribution of C2 compounds towards C2H4 higher than that obtained for the nonpacked reactor and resulted in a higher energy efficiency compared to the BaTiO3 packed reactor. This is attributed to the small pore size of BaTiO3 (10–200 nm) and its high dielectric constant, whereas the polarization inside small pores does not lead to the formation of an overall strong electric field.