Sulfur Research Articles

Computational modeling of petroleum purification for removal of sulfur compounds: Process analysis for reduction of environmental impacts and material costs

In the course of this investigation, three machine learning models (Gaussian Process Regression, Decision Tree Regression, and Kernel Ridge Regression) were examined for determining the correlation between the input variables (x and y) which are spatial coordinates of model’s geometry, and the content of species in adsorption for sulfur capture. For the process modeling, mass transfer was analyzed, and the concentration distribution of sulfur compound was obtained via numerical solution of mass transfer equations, and then used for machine learning models. The machine learning models were trained using a dataset of 19,000 observations, and their performance was assessed through metrics including R2 score, MAE, and RMSE. Analysis of the results reveals that Decision Tree Regression surpassed the other two models in performance, with an R2 score of 0.9989, MAE of 6.64405E-01, and RMSE of 1.1277E+00. Gaussian Process Regression had an R2 score of 0.97106, MAE of 3.65541E+00, and RMSE of 5.6821E+00, while Kernel Ridge Regression had an R2 score of 0.86347, MAE of 8.26121E+00, and RMSE of 1.1330E+01. The Clonal Selection Algorithm was used for hyper-parameter optimization for all models. These findings demonstrate the potential of machine learning techniques for accurately and reliably predicting the concentration of chemical species and highlight the importance of considering the choice of model and hyper-parameter optimization for optimal performance.

Size-dependent influences of nano- and micro-plastics exposure on feeding, antioxidant systems, and organic sulfur compounds in ciliate Uronema marinum

Protozoa play a pivotal role in the microbial cycle, and ciliated protozoan grazing habits are associated with dimethyl sulfide (DMS) cycle. Many studies have explored the impacts of nanoplastics (NPs) and microplastics (MPs) on ecotoxicological effects of ciliates. However, limited research exists on NPs and MPs influences on the production of organic sulfur compounds. The impact of NPs and MPs on the production of dimethyl sulfoxide (DMSO) and carbonyl sulfide (COS) remains unclear. Therefore, we examined the impacts of three concentrations (1 × 105, 5 × 105, and 1 × 106 items/mL) of polystyrene (PS) NPs (50 nm) and MPs (1 and 5 μm) on the ecotoxicology and DMS/dimethylsulfoniopropionate (DMSP)/DMSO/COS production in the ciliate Uronema marinum. NPs and MPs exposure were found to reduce the abundance, growth rate, volume, and biomass of U. marinum. Additionally, NPs and MPs increased the superoxide anion radical (O2˙─) production rates and malondialdehyde (MDA) contents (24 h), leading to a decline in glutathione (GSH) content and an ascend in superoxide dismutase (SOD) activity to mitigate the effects of reactive oxygen species (ROS). Exposure to PS NPs and MPs decreased the ingestion rates of algae by 7.5–14.4%, resulting in decreases in DMS production by 56.8–85.4%, with no significant impact on DMSO production. The results suggest a distinct pathway for the production of DMSO or COS compared to DMS. These findings help us to understand the NPs and MPs impacts on the marine ecosystem and organic sulfur compound yield, potentially influencing the global climate.

Investigating the Irreversible Poisoning of Methanol Synthesis Catalysts – A Setup Construction Guide

AbstractWhen utilizing industrial exhaust gases for methanol synthesis, catalyst poisoning is an important issue. Long‐term in‐situ poisoning under industrially relevant conditions with sulfur‐containing molecules co‐fed into the feed gas flow and supplemented by extensive post‐mortem characterization of the catalyst bed is an efficient way to deepen the understanding of the poisoning mechanism and the different poisoning strengths of H2S, thiophene, and COS reported in literature. Unfortunately, such studies are rare due to the corrosive effects of sulfur compounds on typical lab‐scale flow setups. Therefore, this communication provides a detailed description of a setup built for poisoning studies using sulfur‐containing molecules under industrially relevant methanol synthesis conditions.

The potential linkage between sediment oxygen demand and microbes and its contribution to the dissolved oxygen depletion in the Gan River.

The role of sediment oxygen demand (SOD) in causing dissolved oxygen (DO) depletion is widely acknowledged, with previous studies mainly focusing on chemical and biological SOD separately. However, the relationship between the putative functions of sediment microbes and SOD, and their impact on DO depletion in overlying water, remains unclear. In this study, DO depletion was observed in the downstream of the Gan River during the summer. Sediments were sampled from three downstream sites (YZ, Down1, and Down2) and one upstream site (CK) as a control. Aquatic physicochemical parameters and SOD levels were measured, and microbial functions were inferred from taxonomic genes through analyses of the 16S rRNA gene. The results showed that DO depletion sites exhibited a higher SOD rate compared to CK. The microbial community structure was influenced by the spatial variation of Proteobacteria, Chloroflexi, and Bacteroidota, with total organic carbon (TOC) content acting as a significant environmental driver. A negative correlation was observed between microbial diversity and DO concentration (p < 0.05). Aerobic microbes were more abundant in DO depletion sites, particularly Proteobacteria. Microbes involved in various biogeochemical cycles, such as carbon (methane oxidation, methanotrophs, and methylotrophs), nitrogen (nitrification and denitrification), sulfur (sulfide and sulfur compound oxidation), and manganese cycles (manganese oxidation), exhibited higher abundance in DO depletion sites, except for the iron cycle (iron oxidation). These processes were negatively correlated with DO concentration and positively with SOD (p < 0.05). Overall, the results highlight that aerobic bacteria's metabolic processes consume oxygen, increasing the SOD rate and contributing to DO depletion in the overlying water. Additionally, the study underscores the importance of targeting the removal of in situ microbial molecular mechanisms associated with toxic H2S and CH4 to support reoxygenation efforts in rehabilitating DO depletion sites in the Gan River, aiding in identifying factors controlling DO consumption and offering practical value for the river's restoration and management.

Enhancing oxidative desulfurization using sludge-derived ferrate (VI) for dibenzothiophene: An optimization study

Sulfur emissions pose a substantial threat to human health and the environment. To address this, stringent regulations limit sulfur content in fuels, and innovative desulfurization technologies are under active investigation. Oxidative desulfurization (ODS) employs oxidants to convert sulfur compounds into more readily recoverable sulfones. This study explores high-shear mixing in ODS, known as mixing-assisted oxidative desulfurization (MAOD), focusing on dibenzothiophene (DBT) oxidation in model fuels and pyrolysis oil. Fe(VI) derived from drinking water treatment sludge via wet oxidation is utilized in the MAOD process. The research evaluates the impact of ferrate concentration (400–600 ppm), phase transfer agent (PTA) concentration (100–300 mg per 50 mL of fuel), agitation speed (4,400 to 10,800 rpm), and temperature (40–60 °C) on % DBT conversion. Experimental sulfur conversions range from 63.4 % to 99.6 %. Through response surface methodology, optimal parameters of 537 ppm Fe(VI), 114 mg PTA per 50 mL of model fuel, 8,157 rpm agitation speed, and 41.7 °C are determined. These parameters are applied to pyrolysis oil, achieving a desulfurization efficiency of 53.2 %. Notably, increasing Fe(VI) concentration, agitation speed, and temperature significantly enhances sulfur reduction. The study underscores the potential of using potassium ferrate derived from drinking water treatment sludge in MAOD for effective desulfurization and provides insights into the impact of operating conditions on desulfurization efficiency. Ultimately, the research contributes to advancing environmentally friendly and cost-effective desulfurization technologies.

The Influence of Probiotics in Halitosis and Cariogenic Bacteria: A Systematic Review and Meta-Analysis

Background: The aim of this systematic review was to evaluate the therapeutic potential of probiotics in patients with halitosis and to assess whether probiotics can also be implemented as a preventative tool in oral health. Secondary objectives included the effect of probiotics on oral-health-related quality of life, as well as their safety. Materials and methods: An electronic literature search in Medline (PubMed), Scopus, Web of Science, and the Cochrane library was carried out for the identification and selection of relevant randomized controlled trials. Eligibility was based on inclusion criteria, which included RCTs published after 2013, and the outcome variables were volatile sulfur compound (VSC) levels, organoleptic scores, plaque, or saliva samples to assess cariogenic bacteria counts and/or pH levels. Results: Out of 192 identified records, 16 randomized controlled trials were included. Ten of those studied the effects of probiotics on halitosis and the other six analyzed the effect of probiotics on oral health parameters, such as cariogenic bacteria counts, pH levels, and salivary flow and quality. A total of 921 patients were evaluated. The risk of bias was assessed using the Cochrane risk-of-bias assessment tool version 2. Conclusions: Probiotics exhibit the potential for oral health management by reducing VSC levels, improving saliva quality, and enhancing oral-health-related quality of life. Combining probiotics with tongue scraping may sustain VSC reduction, while symbiotics show potential in reducing tongue coating. However, different bacterial strains have been used in the included studies; hence, the conclusions cannot be generalized, being one of the main limitations of this review. Future research should explore the probiotics’ potential to persist in the oral cavity post-treatment and employ standardized methodologies for conclusive efficacy assessment.

Improvement of the Oxidative Desulfurization Performance Using MoO3/CuO‐Modified Hierarchical HY Zeolite

AbstractThe presence of sulfur compounds in the chemical industry poses significant environmental and economic problems, including endangering human and animal lives and damaging equipment. For this purpose, hierarchical HY zeolite (Hie‐Y) with a SiO2/Al2O3 molar ratio 10 was successfully synthesized through sequential desilication‐dealumination using NH4OH treatment. A weak alkaline media with surfactant cetyltrimethylammonium bromide (CTAB) facilitates mesoporosity formation and preserves the zeolite structure. Metal oxide (CuO, MoO3) ‐ hierarchical HY zeolite nanocomposites have been prepared by one or a combination of 3 methods: 1) ion exchange, 2) precipitation, and 3) calcination. The obtained catalysts were characterized using XRD, FT‐IR, FESEM, UV‐Vis, EDS, and BET techniques. The formation of a hierarchical structure is associated with structure preservation, but partial destruction occurs based on the entering Cu in the zeolite pores. These catalysts have been studied in the oxidative desulfurization (ODS) reaction. Several parameters, including temperature, catalyst amount, DBT concentration, and reaction time, were evaluated in ODS using the Taguchi Design of Experiments. Catalytic activity order was obtained as Y&lt;Hie‐Y&lt;Hie‐Y/CuO&lt;Hie‐Y/MoO3&lt;Hie‐Y/MoO3/CuO. Results indicate an activity increase for the Hie‐Y/MoO3/CuO hierarchical structure owing to synergistic effects of secondary mesoporosity and metal oxides. The catalyst was recoverable and reused for five consecutive runs with preservation of catalytic activity.

Supersulfide formation in the sinus mucosa of chronic rhinosinusitis.

Disruption of the oxidative stress defense system is involved in developing various diseases. Sulfur compounds such as glutathione (GSH) and cysteine (CysSH) are representative antioxidants in the body. Recently, supersulfides, including reactive persulfide and polysulfide species, have gained attention as potent antioxidants regulating oxidative stress and redox signaling. However, their involvement in the pathogenesis of chronic rhinosinusitis (CRS) remains unclear. To clarify the changes in sulfur compounds within the sinus mucosa of each CRS subtype, we measured sulfur compound levels in the sinus mucosa of control individuals (n = 9), patients with eosinophilic CRS (ECRS) (n = 13), and those with non-ECRS (nECRS) (n = 11) who underwent sinus surgery using mass spectrometry. GSH and CysSH levels were significantly reduced, and the glutathione disulfide (GSSG)/GSH ratio, an oxidative stress indicator, was increased in patients with ECRS. Despite the absence of notable variations in supersulfides, patients with ECRS and nECRS exhibited a significant reduction in glutathione trisulfide (GSSSG), which serves as the precursor for supersulfides. This study is the first quantitative assessment of supersulfides in normal and inflamed sinus mucosa, suggesting that sulfur compounds contribute to the pathogenesis of CRS. N/A.

Design of oscillatory helical baffled reactor and dual functional mesoporous catalyst for oxidative desulfurization of real diesel fuel

Enhancing real diesel fuel properties by expelling pollutants using a new design has received considerable interest in the present day. This work investigates the conversion of sulfur compounds via oxidation reaction with peracetic acid as an oxidant. For this purpose, a dual functional mesoporous catalyst was synthesized via loading active metal (iron oxide) nanoparticles over mesopore γ-alumina-anatase titanium oxide prepared via the impregnation procedure (IWI) and precipitation methods, respectively. The novel design of the mesoporous catalyst represents the dual functional catalyst in the oxidative desulfurization process (ODS). The mesoporous catalyst that was formulated underwent a comprehensive analysis using various characterization techniques such as physical adsorption-desorption under N2, X-ray diffraction-XRD, Fourier transforms infrared spectroscopy-FTIR, Field Emission Scanning Electron Microscopy-FESEM, Energy dispersive X-ray analyzer-EDX, and thermogravimetric analysis-TGA. A newly designed laboratory pilot plant for an oscillatory helical baffled reactor (OHBR) was developed and utilized for the ODS process to evaluate the performance of the synthesized mesopore catalyst. The investigated rapid conversion for sulfur removal was found to be 98.42 % under ambient operating conditions such as oscillation of frequency 2 Hz, oscillation of amplitude 8 mm, temperature of oxidation 80°C, and residence time of 9 min. It is clearly observed that the new design of OHBR and mesoporous catalyst highly affected sulfur removal, resulting in a clean diesel.

New Ethylated Derivatives of Sulfur- and Nitrogen-Containing Artifacts from Tenodera sinensis Egg Pod and Their Anti-Renal Fibrosis.

Three pairs of enantiomers and one achiral molecule that are new ethylated derivatives of sulfur and nitrogen-containing compounds named mantidisamides E-H (1-4), along with twenty known ones (5-24), were derived from the ethanol extract of Tenodera sinensis Saussure. The structures of these new compounds and their absolute configurations were assigned on the basis of spectroscopic analyses and computational methods. The assessment of activities in NRK-52e cells induced by TGF-β1 demonstrated that the previously undescribed compounds 1 and 2 exhibited a significant capacity to inhibit the expression of proteins (fibronectin, collagen I, and α-SMA). Moreover, the biological activity of these compounds was found to increase with rising concentrations. Notably, compounds 1-4 should be artifacts; however, undescribed compounds 1 and 2, which possessed obvious biological activity, might be attractive for chemists and biologists due to the potential for more detailed exploration of their properties. It is worth mentioning that compounds 1 and 2 remain novel structures even in the absence of the ethoxy group.

Removal of Thiophenol from Water Using Sepiolite

Crude oil and petroleum products contain various types of sulfur compounds: aliphatic and aromatic mercaptans, hydrogen sulfide, sulfides, disulfides, thiophene derivatives, etc. Some of these may dissolve in water only slightly, but their toxicity and corrosiveness indicate that even these small amounts should be eliminated from water. This work examines, for the first time, the removal of thiophenol (synonyms: benzenethiol, phenyl mercaptan) from water using sepiolite. This clay mineral (evaluated by SEM analysis) is an attractive natural sorbent characterized by its microporosity, which results from its crystalline structure and large specific surface area. Because the structure of thiophenol changes depending on the pH of the aqueous solution (due to the loss of a proton), the research was conducted at pH 4, 7 and 9. The detection of thiophenol in aqueous solution was investigated using UV spectroscopy. It was found that the adsorption of thiophenol is possible, but it occurs only in an acidic environment (pH 4). No sorption is observed at pH 7 or 9. The adsorption of thiophenol at pH 4 does not change significantly after changing the ionic strength of the aqueous solution (distilled water, 0.01 NaCl and 0.1 NaCl). The adsorption capacity of sepioliteis approximately 0.23–0.34 mg/g. Studies using infrared spectroscopy and fitting of Freundlich and Langmuir isotherm models to the results of adsorption experiments indicate that adsorption on unmodified sepiolite follows a physisorption mechanism. Additionally, to understand the behavior of thiophenol in the presence of sepiolite across different pH ranges, DFT/PCM/B3LYP/Aug-CC-pVDZ calculations were used to analyze the charge distribution on particular atoms in its structure.

EFFECT OF DIDODECANOYL PEROXIDE ON TRANSFORMATIONS OF HIGH-SULFUR VACUUM RESIDUE COMPONENTS IN THE PROCESS OF INITIATED CRACKING

This paper presents the results of the study of the composition of cracking products of high-sulfur tar obtained from oil of Zyuzeyevskoye field in the presence of radical-forming additive – didodecanoyl peroxide. Thermal treatment of the mixture of vacuum residue with different amounts of didodecanoyl peroxide was carried out at a temperature of 500 °C. The duration of the process was 15 min. Characteristic features of changes in the material balance of the process, group composition of liquid cracking products, qualitative and quantitative composition of newly formed sulfur compounds were established. The use of additive in the amount of 0.5 – 0.75%wt. allows to reduce thermal stability of high-molecular components of tar (resins and asphaltenes), and also promotes change in direction of reactions. Processes of condensation of resins and asphaltenes into solid coke-like products are slowed down, and cracking reactions are initiated with formation of low-molecular components, which fall into the composition of oils, as a result of which it is possible to obtain additional amounts of distillate fractions. It is shown that thiophene, benzo- and dibenzothiophene derivatives, which are absent in the initial tar, are intensively formed and accumulated in the composition of liquid cracking products, which worsens the quality of the obtained distillate fractions. Among the identified sulfur compounds benzothiophene homologs prevail. It was found that cracking of tar in the presence of additive didodecanoyl peroxide promotes deep destruction of sulfur-containing fragments of vacuum residue and asphaltene molecules. Sulfur compounds formed under these conditions not only get into the composition of oils, but also participate in condensation reactions with the formation of solid products, which leads to an increase in the degree of sulfur removal from the composition of liquid cracking products. For citation: Goncharov A.V., Krivtsov E.B. Effect of didodecanoyl peroxide on transformations of high-sulfur vacuum residue components in the process of initiated cracking. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 121-128. DOI: 10.6060/ivkkt.20246708.15t.

Comparative evaluation of sensory and instrumental flavor profiles of four edible microalgae: Spirulina platensis, Chlorella pyrenoidosa, Chlamydomonas reinhardtii, and Haematococcus pluvialis

Microalgae sensory features are an important parameter to consider in food applications. The current study comparatively evaluated the flavor profiles of four commercial edible microalgae species, i.e., Spirulina platensis, Chlorella proteinosa, Chlamydomonas reinhardtii, and Haematococcus pluvialis through sensory evaluation by a trained expert panel (n = 15) and chemical profiling of flavor compounds, with multivariate statistical methods used to correlate descriptive taste and odor analysis with non-volatile and volatile compounds. S. platensis displayed characteristic salty and umami tastes arising from inorganic ions and 5′-nucleotides, respectively, as well as “muddy” and “floral” odor attributes mainly associated with sulfur compounds and ketones. C. proteinosa and C. reinhardtii shared the taste attributes of sweetness and bitterness mainly contributed by free amino acids, as well as the odor attributes of “seaweed” and “mushroom” in association with aldehydes and alcohols. H. pluvialis had a typical sour taste owning to the presence of abundant organic acids, and smelled “fatty”, “phenolic”, “licorice”, and “fruity” due to aromatic ester and phenolic compounds. Overall, our results provide fundamental insights into the sensory features of common edible microalgae to guide future food applications.

Arcobacteraceae are ubiquitous mixotrophic bacteria playing important roles in carbon, nitrogen, and sulfur cycling in global oceans.

Mixotrophy is an important trophic strategy for bacterial survival in the ocean. However, the global relevance and identity of the major mixotrophic taxa remain largely elusive. Here, we combined phylogenetic, metagenomic, and metatranscriptomic analyses to characterize ubiquitous Arcobacteraceae based on our deep-sea in situ incubations and the global data. The phylogenomic tree of Arcobacteraceae is divided into three large clades, among which members of clades A and B are almost all from terrestrial environments, while those of clade C are widely distributed in various marine habitats in addition to some terrestrial origins. All clades harbor genes putatively involved in chitin degradation, sulfide oxidation, hydrogen oxidation, thiosulfate oxidation, denitrification, dissimilatory nitrate reduction to ammonium, microaerophilic respiration, and metal (iron/manganese) reduction. Additionally, in clade C, more unique pathways were retrieved, including thiosulfate disproportionation, ethanol fermentation, methane oxidation, fatty acid oxidation, cobalamin synthesis, and dissimilatory reductions of sulfate, perchlorate, and arsenate. Within this clade, two mixotrophic Candidatus genera represented by UBA6211 and CAIJNA01 harbor genes putatively involved in the reverse tricarboxylic acid pathway for carbon fixation. Moreover, the metatranscriptomic data in deep-sea in situ incubations indicated that the latter genus is a mixotroph that conducts carbon fixation by coupling sulfur oxidation and denitrification and metabolizing organic matter. Furthermore, global metatranscriptomic data confirmed the ubiquitous distribution and global relevance of Arcobacteraceae in the expression of those corresponding genes across all oceanic regions and depths. Overall, these results highlight the contribution of previously unrecognized Arcobacteraceae to carbon, nitrogen, and sulfur cycling in global oceans.IMPORTANCEMarine microorganisms exert a profound influence on global carbon cycling and ecological relationships. Mixotrophy, characterized by the simultaneous utilization of both autotrophic and heterotrophic nutrition, has a significant impact on the global carbon cycling. This report characterizes a group of uncultivated bacteria Arcobacteraceae that thrived on the "hot time" of bulky particulate organic matter and exhibited mixotrophic strategy during the in situ organic mineralization. Compared with clades A and B, more unique metabolic pathways were retrieved in clade C, including the reverse tricarboxylic acid pathway for carbon fixation, thiosulfate disproportionation, methane oxidation, and fatty acid oxidation. Global metatranscriptomic data from the Tara Oceans expeditions confirmed the ubiquitous distribution and extensive transcriptional activity of Arcobacteraceae with the expression of genes putatively involved in carbon fixation, methane oxidation, multiple sulfur compound oxidation, and denitrification across all oceanic regions and depths.

Olfactory-chemical establishment using odour wheels and fingerprints to manage odor pollution for the petrochemical industry

The odor nuisance may cause major environmental issues, so identifying the odor characteristics is important for odor management and traceability in the petrochemical industry. In this study, odour wheels and fingerprints were applied to manage odor pollution in the petrochemical industry. First, the odor profile method and portable electronic nose evaluation were applied to analyze the flavour sensory profiles of five upstream and downstream petrochemical plants, in order to grasp the odor natures of plants. Second, 375 organized and unorganized samples of 5 plants were analyzed by gas chromatography-mass spectrometry (GC–MS) technology, and a total of 583 odorants were obtained, including sulfur compounds, alcohols, esters, aldehydes, ketones, acids, alkanes, alkenes, halogenated hydrocarbons, aromatic hydrocarbons, nitrogen compounds, and other compounds. Third, the key odorants were identified by gas chromatography-olfactory (GC-O) and odor activity value (OAV) analysis. Fourth, the fingerprint spectras were developed by the identification of key odorants and process sources through principal component analysis. For plant A, 21 odorants were confirmed, including naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1-methylindene, and 2-methylindene. Methyl methacrylate, acetophenone, isobutene, 4-vinyl-1-cyclohexene, acrylonitrile, and styrene were key element for plant B. The fingerprint factor of plant C had 20 odorants, including methanol, butanol, 2-ethylhexanol, acetic acid, and ammonia. And there were 21 odorants for plant D and 14 odorants for plant E, respectively, with similar substance types, including 2-ethyl-2-hexenal, 3-methyl-4-heptanone, isobutyl butyrate, and 1,2,3,5-tetraethylbenzene. Finally, the odor wheels were established by the correlation analysis between odorants and malodor, and compounds in fingerprint spectra weaker related to malodor of plants were removed. Hence, the characteristic odorants of each plant were further clarified, and the odors were associated with compounds, achieving rapid diagnosis and traceability of odor pollution in the petrochemical park. This provided new ideas and technical methods for odor pollution monitoring and identification.

The two-component system TtrRS boosts Vibrio parahaemolyticus colonization by exploiting sulfur compounds in host gut.

One of the greatest challenges encountered by enteric pathogens is responding to rapid changes of nutrient availability in host. However, the mechanisms by which pathogens sense gastrointestinal signals and exploit available host nutrients for proliferation remain largely unknown. Here, we identified a two-component system in Vibrio parahaemolyticus, TtrRS, which senses environmental tetrathionate and subsequently activates the transcription of the ttrRS-ttrBCA-tsdBA gene cluster to promote V. parahaemolyticus colonization of adult mice. We demonstrated that TsdBA confers the ability of thiosulfate oxidation to produce tetrathionate which is sensed by TtrRS. TtrRS autoregulates and directly activates the transcription of the ttrBCA and tsdBA gene clusters. Activated TtrBCA promotes bacterial growth under micro-aerobic conditions by inducing the reduction of both tetrathionate and thiosulfate. TtrBCA and TsdBA activation by TtrRS is important for V. parahaemolyticus to colonize adult mice. Therefore, TtrRS and their target genes constitute a tetrathionate-responsive genetic circuit to exploit the host available sulfur compounds, which further contributes to the intestinal colonization of V. parahaemolyticus.

Profiles of volatile sulfur compounds in various vegetables consumed in Korea using HS-SPME-GC/MS technique.

Volatile sulfur compounds (VSCs) are not only important for their therapeutic potential but also significantly influence the flavor profiles of agricultural products. VSCs exhibit various chemical structures due to their stability and volatility, and they may form or be altered as a result of enzymatic and chemical reactions during storage and cooking. This study has focused on profiles of VSCs in 58 different vegetable samples by using HS-SPME-GC/MS technique and chemometric analyses. The validation was carried out using cabbage juice as a vegetable matrix for VSCs analysis, showing satisfactory repeatability (RSD 8.07% ~ 9.45%), reproducibility (RSD 4.22% ~ 7.71%), accuracy and specificity. The established method was utilized on various vegetables, revealing that 21 VSCs such as sulfides, disulfides, trisulfides, isothiocyanates, sulfhydryls, and thiophenes were successfully identified and quantified. These compounds were found in a range of vegetables including Allium species, Cruciferae, Capsicum species, green leafy vegetables, and mushrooms. In particular, isocyanate and allyl groups were abundant in Cruciferae and Allium vegetables, respectively. Cooking conditions were shown to reduce the levels of certain sulfur compounds such as dimethyl sulfide and dimethyl trisulfide in vegetables like broccoli and cabbage, suggesting that heat treatment can lead to the volatilization and reduction of these compounds. The present study provides reliable insights into the compositions of VSCs in various vegetables and examines the changes induced by different cooking methods.

Collective dynamics of liquid sulphur across the polymerisation transition temperature probed by inelastic x-ray scattering

Inelastic x-ray scattering (IXS) experiments on liquid sulphur were carried out below (140 ∘C) and above (180 ∘C) the polymerisation temperature T λ of about 159 ∘C to investigate changes in the collective dynamics of this unique liquid, that exhibits a liquid–liquid transition. As reported earlier, broad longitudinal acoustic excitation signals were observed at both temperatures, and only the width of the quasielastic peaks slightly decreased when the temperature crossed the transition temperature. A model analysis was performed using a generalised Langevin formalism with a memory function having one thermal and two viscoelastic decay channels with the help of simple sparse modelling, and large positive deviations from the hydrodynamic sound velocity by 51%–54% were observed. The fast viscoelastic relaxation time τ µ is close to the correlation times of intermolecular stretching and bending motions of local sulphur connections in both ring and chain structures, and is similar to those of other molecular liquids. The small contrasts in the IXS spectra across the λ transition result in large changes in only the slow viscoelastic decay time τ α of the memory function. The τ α value at 140 ∘C matches the mixed internal/external torsional modes of S8 molecules well, whereas that at 180 ∘C has no corresponding molecular motion mode. The kinematic viscosity values at the Q→0 limit are much smaller than the minimum values of macroscopic shear viscosity, indicating that large changes in relaxation dynamics are expected with Q in the GHz and MHz excitation regimes.

Real-time tracking of fish quality using a cellulose filter paper colorimetric indicator incorporated with prickly pear fruit betacyanins

In the present work, a freshness indicator was developed by immobilizing extracted betacyanins from prickly pear fruit (PFB) onto cellulose filter paper to visually determine fish spoilage. Various properties of the prepared indicator, including color stability, moisture uptake, sensivity to hydrogen sulfide (H2S) gas and pH changes, and chemical analysis were studied. The PFB-based indicator exhibited good color stability at various temperatures and times, with no significan color changes observed during storage at 25, 4, and −18 °C for 8 days. The moisture absorption of the indicator based on PFB was lower than that of cellulose paper, which is crucial for colorimetric indicators. Basic nitrogen and sulfur compounds are the main volatile compounds produced during fish spoilage. The results of the present study showed that both total volatile basic nitrogen (TVB-N) and H2S gas produced during fish spoilage contributed to the color changes of betacyanin-based colorimetric indicators. The prepared freshness indicators were pH-sensitive, with significant color changes due to TVB-N and H2S production during fish storage. A significant correlation was observed between fish quality (pH, TVB-N and total viable count) and the visible color changes of the indicators. The color of the designed indicator shifted from dark pink to pale pink/white during fish storage. These prepared freshness indicators were inexpensive, easy to use, and non-toxic, making them suitable for assessing the quality and shelf life of fish fillets.

Insights into Cis-Amide-Modified Carbon Nanotubes for Selective Purification of CH4 and H2 from Gas Mixtures: A Comparative DFT Study.

Among a plethora of mixtures, the methane (CH4) and hydrogen (H2) mixture has garnered considerable attention for multiple reasons, especially in the framework of energy production and industrial processes as well as ecological considerations. Despite the fact that the CH4/H2 mixture performs many critical tasks, the presence of other gases, such as carbon dioxide, sulfur compounds like H2S, and water vapor, leads to many undesirable consequences. Thus purification of this mixture from these gases assumes considerable relevance. In the current research, first-principle calculations in the frame of density functional theory are carried out to propose a new functional group for vertically aligned carbon nanotubes (VA-CNTs) interacting preferentially with polar molecules rather than CH4 and H2 in order to obtain a more efficient methane and hydrogen separations The binding energies associated with the interactions between several chemical groups and target gases were calculated first, and then a functional group formed by a modified ethylene glycol and acetyl amide was selected. This functional group was attached to the CNT edge with an appropriate diameter, and hence the binding energies with the target gases and steric hindrance were evaluated. The binding energy of the most polar molecule (H2O) was found to be more than six times higher than that of H2, indicating a significant enhancement of the nanotube tip's affinity toward polar gases. Thus, this functionalization is beneficial for enhancing the capability of highly packed functionalized VA-CNT membranes to purify CH4/H2 gas mixtures.