Transformation Of Sulfur Compounds Research Articles

Transformation of sulfur compounds in two typical atmospheric residues in hydrotreating via ESI FT-ICR MS

The atmospheric residue (AR) hydrotreating (HDT) process attracts more and more attention because it provides quality feedstock for downstream catalytic cracking. The compositional analysis of feeds and products is a key step to improve our understanding of HDT process. In this study, two ARs representing a low (LSAR) and a high sulfur content (HSAR) were hydrotreated in a fixed-bed flow reactor. With increased process severity, we employed electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) to monitor the evolution of the sulfur families in HDT. The results suggest that although the properties and molecular composition of sulfur classes in ARs vary, the evolution of the sulfur compounds is quite similar. Further analysis indicated that the removal difficulty of S1 and S2 species was positively correlated with the number of aromatic rings.

Radical-mediated C-S bond cleavage in C2 sulfonate degradation by anaerobic bacteria

Bacterial degradation of organosulfonates plays an important role in sulfur recycling, and has been extensively studied. However, this process in anaerobic bacteria especially gut bacteria is little known despite of its potential significant impact on human health with the production of toxic H2S. Here, we describe the structural and biochemical characterization of an oxygen-sensitive enzyme that catalyzes the radical-mediated C-S bond cleavage of isethionate to form sulfite and acetaldehyde. We demonstrate its involvement in pathways that enables C2 sulfonates to be used as terminal electron acceptors for anaerobic respiration in sulfate- and sulfite-reducing bacteria. Furthermore, it plays a key role in converting bile salt-derived taurine into H2S in the disease-associated gut bacterium Bilophila wadsworthia. The enzymes and transporters in these anaerobic pathways expand our understanding of microbial sulfur metabolism, and help deciphering the complex web of microbial pathways involved in the transformation of sulfur compounds in the gut.

Asgard archaea: Diversity, function, and evolutionary implications in a range of microbiomes.

Elucidating the diversity of the Archaea has many important ecological and evolutionary implications. The Asgard superphylum of the archaea, described recently from metagenomic data, has reignited the decades-old debate surrounding the topology of the tree of life. This review synthesizes recent findings through publicly available genomes and literature to describe the current ecological and evolutionary significance of the Asgard superphylum. Asgard archaea have been found in a diverse range of microbiomes across the globe, primarily from sedimentary environments. Within these environments, positive correlations between specific members of the Asgard archaea and Candidate Division TA06 bacteria have been observed, opening up the possibility of symbiotic interactions between the groupings. Asgard archaeal genomes encode functionally diverse metabolic pathways, including the Wood-Ljungdahl pathway as a carbon-fixation strategy, putative nucleotide salvaging pathways, and novel mechanisms of phototrophy including new rhodopsins. Asgard archaea also appear to be active in nitrogen cycling. Asgard archaea encode genes involved in both dissimilatory nitrate reduction and denitrification, and for the potential to use atmospheric nitrogen or nitrite as nitrogen sources. Asgard archaea also may be involved in the transformation of sulfur compounds, indicating a putative role in sulfur cycling. To date, all Asgard archaeal genomes identified were described as obligately anaerobic. The Asgard archaea also appear to have important evolutionary implications. The presence of eukaryotic signature proteins and the affiliation of Asgard archaea in phylogenetic analyses appears to support two-domain topologies of the tree of life with eukaryotes emerging from within the domain of archaea, as opposed to the eukaryotes being a separate domain of life. Thus far, Heimdallarchaeota appears as the closest archaeal relative of eukaryotes.

The life sulfuric: microbial ecology of sulfur cycling in marine sediments.

SummaryAlmost the entire seafloor is covered with sediments that can be more than 10 000 m thick and represent a vast microbial ecosystem that is a major component of Earth's element and energy cycles. Notably, a significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. Sulfur cycling, which is primarily driven by sulfate reduction, is tightly interwoven with other important element cycles (carbon, nitrogen, iron, manganese) and therefore has profound implications for both cellular‐ and ecosystem‐level processes. Sulfur‐transforming microorganisms have evolved diverse genetic, metabolic, and in some cases, peculiar phenotypic features to fill an array of ecological niches in marine sediments. Here, we review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasise how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate‐rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deep‐subsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle.

Transformation of Sulfur Compounds in the Hydrotreatment of Supercritical Fluid Extraction Subfractions of Saudi Arabia Atmospheric Residua

Atmospheric residue from Saudi Arabia (SZAR) was subjected to supercritical fluid extraction fractionation (SFEF) experiments. Four extractable subfractions (SFEF 1–4) and an unextractable end-cut were obtained. SFEF 1–4 were subjected to a hydrotreating (HDT) test in a mini-tubular reactor packed with commercial hydrodemetallization (HDM) and hydrodesulfurization (HDS) catalysts in order to determine the structural composition transformation of sulfur-containing compounds. Experiments were undertaken at a temperature of 360 °C, a hydrogen pressure of 14.7 MPa, a liquid hour space velocity (LHSV) of 0.25 h–1, and a H2/feed ratio of 650:1 (m3/m3). The SFEF subfractions and their products were subjected to analysis of their sulfur and nitrogen contents, using an ANTEK 7000S analyzer, and their saturates, aromatics, resins, and asphaltenes (SARA) compositions were analyzed using open column liquid chromatography. The detailed molecular composition of sulfur heteroatom species was determined by methylation, f...

Vertical physico-chemical gradients with distinct microbial communities in the hypersaline and heliothermal Lake Ursu (Sovata, Romania)

The effect of vertical physico-chemical stratification on the planktonic microbial community composition of the deep, hypersaline and heliothermal Lake Ursu (Sovata, Romania) was examined in this study. On site and laboratory measurements were performed to determine the physical and chemical variables of the lake water, and culture-based and cultivation-independent techniques were applied to identify the members of microbial communities. The surface of the lake was characterized by a low salinity water layer while the deepest region was extremely saline (up to 300 g/L salinity). Many parameters (e.g. photosynthetically active radiation, dissolved oxygen concentration, pH, redox potential) changed dramatically from 2 to 4 m below the water surface in conjunction with the increasing salinity values. The water temperature reached a maximum at this depth. At around 3 m depth, there was a water layer with high (bacterio) chlorophyll content dominated by Prosthecochloris vibrioformis, a phototrophic green sulfur bacterium. Characteristic microbial communities with various prokaryotic taxa were identified along the different environmental parameters present in the different water layers. Some of these bacteria were known to be heterotrophic and therefore may be involved in the decomposition of lake organic material (e.g. Halomonas, Idiomarina and Pseudoalteromonas) while others in the transformation of sulfur compounds (e.g. Prosthecochloris). Eukaryotic microorganisms identified by molecular methods in the lake water belonged to genera of green algae (Mantionella and Picochlorum), and were restricted mainly to the upper layers.

Modeling of the Transformation of Sulfur Compounds in Oxygen Gasification of Coal Dust

It is shown that, owing to the presence of a large amount of Ca and Fe in the mineral part of a fuel, it is possible to substantially reduce the sulfur content in the gaseous phase and, hence, improve ecological indexes of the process under the following conditions: the content of O2 is close to the stoichiometric value for fuel gasification, the temperature is ≈(1600–1800) K, and the pressure is ≈ 10 atm or higher.

Studies on Causes and Measures for the Growth Disorders of Early Planting Rice in the Northern District of Shiga Prefecture (Part3) : Transformation of Sulfur Compounds in Paddy Soils Causing Growth Disorders in Rice and Their Present Status in Soils

Studies on Causes and Measures for the Growth Disorders of Early Planting Rice in the Northern District of Shiga Prefecture (Part3) : Transformation of Sulfur Compounds in Paddy Soils Causing Growth Disorders in Rice and Their Present Status in Soils

Transformation of sulfur compounds by an abundant lineage of marine bacteria in the alpha-subclass of the class Proteobacteria.

Members of a group of marine bacteria that is numerically important in coastal seawater and sediments were characterized with respect to their ability to transform organic and inorganic sulfur compounds. Fifteen strains representing the Roseobacter group (a phylogenetic cluster of marine bacteria in the alpha-subclass of the class Proteobacteria) were isolated from seawater, primarily from the southeastern United States. Although more than one-half of the isolates were obtained without any selection for sulfur metabolism, all of the isolates were able to degrade the sulfur-containing osmolyte dimethyl sulfoniopropionate (DMSP) with production of dimethyl sulfide (DMS). Five isolates also degraded DMSP with production of methanethiol, indicating that both cleavage and demethylation pathways for DMSP occurred in the same organism, which is unusual. Five isolates were able to reduce dimethyl sulfoxide to DMS, and several isolates also degraded DMS and methanethiol. Sulfite oxygenase activity and methanesulfonic acid oxygenase activity were also present in some of the isolates. The ability to incorporate the reduced sulfur in DMSP and methanethiol into cellular material was studied with one of the isolates. A group-specific 16S rRNA probe indicated that the relative abundance of uncultured bacteria in the Roseobacter group increased in seawater enriched with DMSP or DMS. Because this group typically accounts for >10% of the 16S ribosomal DNA pool in coastal seawater and sediments of the southern United States, clues about its potential biogeochemical role are of particular interest. Studies of culturable representatives suggested that the group could mediate a number of steps in the cycling of both organic and inorganic forms of sulfur in marine environments.

Transformations of sulfur compounds in marsh-flat sediments

Measurements were made in mud-flat sediments from Flax Pond salt marsh to characterize the rates and mechanisms of sulfur cycling in an organic-rich coastal marine environment. Approximately 13 mmoles/m 2 of reduced sulfur are generated annually in the mud flat and the dominant-solid-phase product is pyrite. Ion activity products involving dissolved iron and sulfide species indicate approximate saturation with respect to metastable iron sulfide phases, showing that pyrite is not likely to be the first-formed Fe-bearing sulfide. Comparison of ΣH 2S vs. SO −− 4 relationships in anoxic incubation experiments with those occurring in the undisturbed sediment permits evaluation of possible mechanisms involved in the transformation of metastable iron monosulfides to pyrite. Oxidants ( e.g. MnO 2) that are introduced into the surface sediment, either by animal activity or physical events, are apparently necessary to cause major oxidation of FeS and ΣH 2S to pyrite and sulfate. Solid-phase sulfur analyses and net ΣH 2S accumulation in sediment pore waters are consistent with major sulfide oxidation, indicating that approximately 95% of the sulfide generated in the mud flat is reoxidized to sulfate and roughly half of this oxidation involves dissolved sulfide. The major factors limiting reduced sulfur burial are physical and biological disturbances and a low abundance of reactive solid-phase iron (2 wt%).

Ecology of some Species of Thiobacillus and Sulfate‐reducing Bacteria in the Middle Course of the River Guadalquivir (Spain)

AbstractDuring 1985, a study was made of the physical, chemical and biological characteristics of the River Guadalquivir. At the same time, the density of certain microorganisms involved in the transformation of sulfur compounds in the water was studied. The results obtained give the following numerical order of density:T. thioparus >sulfate reducers > T. denitrificans > T. thiooxidans. Urban waste was found to increase density levels of these microorganisms. Their relationship with certain environmental parameters is discussed in this study. Regression equations have been obtained of bacteria numbers for three of the four groups studied, using water temperature and permanganate oxidability as dependent variables.

Biochemical functions of persulfides.

In biological systems, persulfides (RSS-) are reactive, unstable intermediates in the transformations of sulfur compounds. Persulfides are also referred to as polysulfides, or alkyl/aryl hydrogen disulfides. The persulfide sulfur is commonly termed, “sulfane”, to designate sulfur covalently bonded only to other sulfur atoms. The scission of the sulfur-sulfur bond is enhanced by the joint action of electrophilic and nucleophilic groups1.KeywordsLipoic AcidBiochemical FunctionAldehyde OxidaseCyanogenic GlycosideMixed DisulfideThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.