Methanethiol Research Articles

Investigation of volatile sulfur compound level and halitosis in patients with gingivitis and periodontitis

This study aimed to measure the levels of volatile sulfur compounds and investigate the occurrence of halitosis in patients with gingivitis and periodontitis. Additionally, the incidence rates of gingivitis and periodontitis in patients with halitosis were investigated. Through various statistical analyses, we attempted to determine the relationship between periodontal disease and halitosis. One-hundred-and-four participants (52 females and 52 males, mean age: 46.49 ± 16.03 years) were enrolled in this cross-sectional study, comprising 33 healthy controls, 43 patients with gingivitis, and 28 patients with periodontitis. Gas chromatography was used to measure hydrogen sulfide (H2S) and methyl mercaptan (CH3SH), which are representative VSCs. The VSC cut-off values for diagnosing halitosis were 65.79 ppb for women and 79.94 ppb for men. Total VSC level was significantly higher in the gingivitis than the healthy control group (186.72 ± 374.83 ppb vs. 19.80 ± 40.19 ppb, p = 0.035). There was no significant difference between the gingivitis and periodontitis (153.79 ± 278.51 ppb) groups. H2S level was significantly higher in the gingivitis (100.51 ± 183.69 ppb) and periodontitis (91.57 ± 132.06 ppb) groups than in healthy controls (14.97 ± 31.22 ppb), and CH3SH level was significantly higher in gingivitis group (29.31 ± 59.16 ppb) than in the healthy control (5.73 ± 14.10 ppb) (all p < 0.05). Halitosis was found in 3% of healthy controls and 39.5% and 42.9% of patients with gingivitis and periodontitis patients, respectively, making it significantly higher in the gingivitis and periodontitis groups than the healthy controls (p = 0.005). Conversely, among participants with halitosis, 53.1% had gingivitis, 37.5% had periodontitis, and 90.6 incidence had periodontal disease. Multivariate logistic regression analysis to predict the presence of halitosis, found periodontal disease was a significant predictor of halitosis (OR = 3.607, 95% CI 1.023–12.718, p = 0.046). Considering area under curve value for halitosis, the cut-off value of healthy control (H2S:61.5 ppb, CH3SH:3.5 ppb), gingivitis (H2S:50.0 ppb, CH3SH:6 ppb), and periodontitis (H2S:62.0 ppb, CH3SH:3.5 ppb) were (all p < 0.05). Our results emphasize the close and strong relationship between periodontal disease and halitosis through human clinical evidence based on the high co-occurrence rate of mutual diseases. Additionally, the presence of periodontal disease increased the probability of halitosis by 3.607 times. These results suggest that H2S can be used as a biomarker of halitosis in patients with periodontal disease.

Volatile Sulfur Compounds Produced by the Anaerobic Bacteria Porphyromonas spp. Isolated from the Oral Cavities of Dogs.

Porphyromonas spp. are oral anaerobic Gram-negative bacteria that form black-pigmented colonies on blood agar and produce volatile sulfur compounds (VSCs), such as hydrogen sulfide (H2S), methyl mercaptan (CH3SH), and dimethyl sulfide ((CH3)2S), which cause halitosis and the destruction of periodontal tissues. P. gulae is considered the main pathogen involved in periodontal disease in dogs. However, the characteristics of the VSCs produced by P. gulae are unknown. In the present study, VSCs were measured in 26 isolates of P. gulae and some isolates of the other Porphyromonas spp. obtained from the oral cavities of dogs with periodontal disease using an in vitro assay with an Oral ChromaTM gas chromatograph. The results demonstrated that P. gulae was able to produce large amounts of H2S and CH3SH, and the dominant product was CH3SH (CH3SH/H2S was approximately 2.2). Other Porphyromonas spp. that were also obtained from the oral cavities of dogs with periodontal disease indicated similar levels of production of H2S and CH3SH to those of P. gulae. It is strongly suggested that the high levels of H2S and CH3SH produced by P. gulae and other Porphyromonas spp. contribute to halitosis and the destruction of periodontal tissues during the progression of periodontal disease in dogs.

Effect of K/Na ratio on adsorption of sweetened gas in dehydration packed bed adsorber: A Monte Carlo simulation study of single and multicomponent gas mixture

The input feed of natural gas dehydration units often contains significant quantities of mercaptan. To effectively separate water from the sweet gas stream, it is crucial to select an appropriate molecular sieve. Mercaptan adsorption can cause issues in later stages of the process. In this research, the Grand Canonical Monte Carlo (GCMC) method was employed to investigate the adsorption behavior of methane, ethane, water, methyl mercaptan, and carbonyl sulfide as both single and multicomponent gas mixtures on LTA zeolite with varying K/Na ratios. The obtained data were modeled using the Langmuir and Sips models, with the Sips model exhibiting better agreement with the simulation results. Gas adsorption simulations were conducted across temperatures of 323 K, 313 K, 303 K, and 333 K, a pressure range of 1–70 bar. The findings indicate that increasing temperature diminishes adsorption on LTA zeolite, while increasing pressure has an incremental effect on adsorption. Adsorption studies were performed for both wet and dry gas mixtures. A rise in the number of potassium ions within the zeolite structure resulted in decreased component adsorption, potentially due to the reduction in zeolite cavity size. The results emphasize that the sodium-to-potassium ratio plays a crucial role in mercaptan adsorption or depletion within the packed bed tower. For a gas mixture, it is not recommended to utilize LTA zeolite with a potassium content lower than 55% for gas adsorption due to its propensity to adsorb mercaptan.

Effects of Administration of Prebiotics Alone or in Combination with Probiotics on In Vitro Fermentation Kinetics, Malodor Compound Emission and Microbial Community Structure in Swine

The objective of this study was to evaluate the effect of Lactobacillus amylovorus, L. plantarum, galacto-oligosaccharide (GOS) and their synbiotic formulations on pH, volatile fatty acids (VFA), malodor, and microbial ecological profiles through a 24-h in vitro fermentation model. Inclusion of GOS alone and in synbiotic combination with either probiotic resulted in consistently lower pH and higher total gas volumes at 12 and 24 h of incubation. Notably, concentrations of odorous compounds (hydrogen sulfide, H2S and methyl mercaptan, CH3SH) in the total gas produced were significantly lower in these GOS-containing treatments relative to the controls and probiotic-only-treated groups. However, although ammonia showed an initial relative reduction at 12 h, concentrations did not differ among treatments at 24 h. Further, the GOS-containing treatments had remarkably higher total and individual VFAs, including acetate, propionate, and butyrate, relative to controls and the probiotic-only treatments. Analysis of microbial composition and diversity showed clustering of GOS-containing treatments away from the controls and probiotic-only treatments at 12 and 24 h of incubation. Our study suggests that GOS supplementation (alone or in combination with L. amylovorus or L. plantarum probiotic strains) has the potential to increase VFA production in the swine gut while lowering emissions of malodorous compounds, except ammonia, in their manure.

The Effect of Subacute Oral Folic Acid Treatment on Growth of Porphyromonas gulae in Dogs.

Periodontitis is one of the most prevalent infectious diseases in humans and animals. It is a multifactorial disease resulting in attachment loss and tooth loss. Therefore, preventive dentistry, such as daily teeth cleaning or providing dental chews from puppyhood is essential. This study aimed to find an alternative option for preventive dentistry by examining both in vitro and clinically, the antibacterial, antihalitosis, and anti-inflammatory effects of folic acid (FA) in dogs with periodontal disease. The antibacterial and antihalitosis responses of FA were evaluated in vitro using Porphyromonas gulae, a bacterium that plays a significant role in the development of periodontal disease in dogs. Anti-inflammatory responses, such as secretion of IL-1β, IL-6, and IL-8 induced by P. gulae infection in human gingival epithelium have been studied. This study used dogs with P. gulae-associated periodontal diseases and was conducted by providing a dental chew containing 0.13% FA for 28 days. The viability and halitosis production (hydrogen sulfide and methyl mercaptan) of P. gulae was significantly inhibited by FA in a dose and time-dependent manner. IL-1β, IL-6, and IL-8 secretion were also significantly suppressed by FA treatment in a dose-dependent manner. In vitro bactericidal, antihalitosis, and anti-inflammatory effects of FA were confirmed in dogs with P. gulae-associated periodontal disease. One month of oral treatment with 0.13% FA-containing dental chews significantly reduced halitosis as well as P. gulae activity. This study suggests that oral treatment with FA can be a preventive option for periodontal disease in dogs as well as humans.

Enzymatic Synthesis of l-Methionine Analogues and Application in a Methyltransferase Catalysed Alkylation Cascade.

Chemical modification of small molecules is a key step for the development of pharmaceuticals. S-adenosyl-l-methionine (SAM) analogues are used by methyltransferases (MTs) to transfer alkyl, allyl and benzyl moieties chemo-, stereo- and regioselectively onto nucleophilic substrates, enabling an enzymatic way for specific derivatisation of a wide range of molecules. l-Methionine analogues are required for the synthesis of SAM analogues. Most of these are not commercially available. In nature, O-acetyl-l-homoserine sulfhydrolases (OAHS) catalyse the synthesis of l-methionine from O-acetyl-l-homoserine or l-homocysteine, and methyl mercaptan. Here, we investigated the substrate scope of ScOAHS from Saccharomyces cerevisiae for the production of l-methionine analogues from l-homocysteine and organic thiols. The promiscuous enzyme was used to synthesise nine different l-methionine analogues with modifications on the thioether residue up to a conversion of 75 %. ScOAHS was combined with an established MT dependent three-enzyme alkylation cascade, allowing transfer of in total seven moieties onto two MT substrates. For ethylation, conversion was nearly doubled with the new four-enzyme cascade, indicating a beneficial effect of the in situ production of l-methionine analogues with ScOAHS.

Oral-malodor measurement and intention to quit smoking in men: A before-after study.

Few studies have examined the effect of feedback based on oral-malodor measurements on the motivation to quit smoking. Therefore, this study examined whether oral-malodor measurements were associated with the intention to quit smoking. This retrospective, uncontrolled before-after study invited smokers to a workplace health event in 2019 and 2020 to motivate them to quit smoking. They attended seminars on oral health and smoking cessation aids, and then underwent respiratory function and oral-malodor measurements using exhaled and oral cavity air, respectively. Intention to quit smoking was evaluated by answers to questions regarding the intention to quit in the next 1 or 6 months in questionnaires collected before and after the event. This study analyzed 241 men aged 20-54 years (mean: 33.2 ± 10.5) to examine factors associated with the intention to quit in multivariable logistic regression analyses for age, tobacco type (cigarettes and heated-tobacco products), and category of tobacco consumption. Before the event, 8.7%, 17.0%, and 74.3% of smokers had intended to quit in the next month, the next six months, or had no intention to quit, respectively. After the event, the respective percentages were 17.8%, 26.6%, and 55.6%. A higher methyl mercaptan concentration, a volatile sulfide component of oral malodor, was significantly associated with the intention to quit in the next month (adjusted odds ratio, AOR=4.24; 95% CI: 1.52-11.8, p=0.006). The participants with higher daily tobacco consumption were less likely to acquire the intention to quit in the next six months (AOR=0.37; 95% CI: 0.15-0.92, p=0.032). Other variables, such as lung age deficit, exhaled CO concentration, and hydrogen sulfide concentration (another component of oral malodor), were not significantly associated. Oral-malodor measurement feedback may help motivate men to quit smoking in the next 1 month rather than in the next six months.

An ultra-long stability of lanthanum (La) modified molecular sieve for catalytic degradation of typical sulfur-containing VOCs in a near-real environment

The catalytic degradation of typical sulfur-containing VOCs, ethyl mercaptan (C2H5SH), in a near-real environment remains a challenge task. In this study, an ultra-long stability of 600 h for degradation of C2H5SH was obtained over La doped ZSM-5, and the corresponding catalytic performance, reaction and deactivation mechanism were investigated by a series of ex situ and in situ characterizations. Furthermore, the influence law of other low-carbon mercaptans, such as methyl mercaptan (CH3SH), propyl mercaptan (C3H7SH), and butyl mercaptan (C4H9SH) as well as the moisture on their stability were investigated. The slight deactivation by designed experiment revealed a distinguished reversible moisture-induced deactivation mechanism, where moisture promoted the formation of carbonate related species that covers the active sites, while this deactivation could be recovered by a simple temperature-lifting strategy. This work provides a theoretical guidance for catalytic degradation of mixed sulfur-containing VOCs under the presence of moisture.

Oxygen vacancies mediated flower-like BiOX microspheres for photocatalytic purification of methyl mercaptan odor: Significant distinction induced by halogen elements

Odor pollution, represented by low-concentration volatile organic sulfur compounds (VOSCs), has become a difficult issue in the field of air pollution control. Photocatalytic oxidation technology is applicable for the treatment of low-concentration VOSCs. However, currently available photocatalysts often suffer from limited efficiency and severe deactivation. Herein, flower-like BiOX (X = Cl, Br, I) microspheres abundant with oxygen vacancies (OVs) were developed for the removal of the model pollutant CH3SH. BiOI exhibited the optimal CH3SH oxidation performance, with the removal efficiency stabilizing at 75% within 180-min simulated solar-light irradiation, while BiOCl and BiOBr deactivated from 38% and 55% to 20% and 22%, respectively. Mechanism analysis found, OVs and I- synergistically endowed BiOI with better CH3SH adsorption and activation, enhanced light harvesting, quicker charge transfer, and more affluent •OH and •O2- productions. Photogenerated e- and •OH took a predominantly irreplaceable part in CH3SH oxidation, followed by •O2- and h+. New pathways of CH3SH photocatalytic oxidation was proposed, and dimethyl trisulfide was firstly found as its oxidation product. Besides, the oxidation products SO42- was proved to be converted to •SO4- radicals to further promote CH3SH oxidation, and the largest production of •SO4- over BiOI might be responsible for its excellent performance. Furthermore, the strong adsorption and substantial accumulation of CH3SO3H on BiOCl and BiOBr might be the key cause of their rapid deactivation. This work would inspire the construction of more effective photocatalysts for the purification of VOSCs odor.

Cation Substitution Induced d‐Band Center Modulation on Cobalt‐Based Spinel Oxides for Catalytic Ozonation

AbstractCo3O4 spinel is a promising transition metal oxide (TMO) catalyst for the catalytic ozonation of volatile organic compounds (VOCs). Herein, metal–organic frameworks (MOFs)‐derived Ni‐ and Mg‐ substituted Co3O4 catalysts retain similar spinel structures, but display improved and reduced ozonation performance of methyl mercaptan (CH3SH), respectively. Remarkably, the NiCo2O4 catalyst can still ≈90% removal of CH3SH after running for 20 h at room temperature under an initial concentration of 50 ppm CH3SH and 40 ppm O3, relative humidity of 60%, and space velocity of 300 000 mL h−1 g−1, exceeding the reported values. Experimental characterizations have unveiled that the substitution of Ni and Mg into the Co3O4 spinel altered surface acidity, oxygen species mobility, and Co2+/Co3+ ratio. The in situ Raman spectra reveal the dynamic formation Co(III)‐Oad* via the transformation of O3 into surface atomic oxygen (Oad*) and peroxide species (O2*). Theoretical calculations verify that Ni‐substitution increases nonuniform charges and Fermi density, leading to a moderate increase in d‐band center energy levels, thereby promoting O3 specific adsorption/activation to convert Oad*/O2* and •OH/1O2/•O2−, which contributes to eliminate CH3SH and prevent poisoning. The concept of tuning the d‐band center can provide valuable insights for the design of other catalysts for catalytic ozonation.

Genetic and Physiological Probing of Cytoplasmic Bypasses for the Energy-Converting Methyltransferase Mtr in Methanosarcina acetivorans.

Methanogenesis is a unique energy metabolism carried out by members of the domain Archaea. Unlike most other methanogens, which reduce CO2 to methane with hydrogen as the electron donor, Methanosarcina acetivorans is able to grow on methylated compounds, on acetate, and on carbon monoxide (CO). These substrates are metabolized via distinct yet overlapping pathways. For the use of any single methanogenic substrate, the membrane-integral, energy-converting N5-methyl-tetrahydrosarcinapterin (H4SPT):coenzyme M (HS-CoM) methyltransferase (Mtr) is required. It was proposed that M. acetivorans can bypass the methyl transfer catalyzed by Mtr via cytoplasmic activities. To address this issue, conversion of different energy substrates by an mtr deletion mutant was analyzed. No significant methyl transfer from H4SPT to HS-CoM could be detected with CO as the electron donor. In contrast, formation of methane and CO2 in the presence of methanol or trimethylamine was indicative of an Mtr bypass in the oxidative direction. As methane thiol and dimethyl sulfide were transiently produced during methylotrophic methanogenesis in the mtr mutant, involvement in this process of methyl sulfide-dependent methyltransferases (Mts) was analyzed in a strain lacking both the Mts system and Mtr. It could be unequivocally demonstrated that the Mts system is not involved in bypassing Mtr, thereby ruling out previous proposals. Conversion of [13C]methanol indicated that in the absence of Mtr M. acetivorans provides the reducing equivalents for methyl-S-CoM reduction to methane by oxidizing (an) intracellular compound(s) to CO2 rather than disproportioning the source of methyl groups. Thus, no in vivo Mtr bypass appears to exist in M. acetivorans. IMPORTANCE Methanogenic archaea possess only a limited number of chemiosmotic coupling sites in their respiratory chains. Among them, N5-methyl-H4SPT:HS-CoM methyltransferase (Mtr) is the most widely distributed. Previous observations led to the conclusion that Methanosarcina acetivorans is able to bypass this reaction via methyl sulfide-dependent methyltransferases (Mts). However, strains lacking Mtr are not able to produce methane from CO. Also, these strains are unable to oxidize methylated substrates to CO2, in contrast to observations in the close relative Methanosarcina barkeri. The results also highlight the sole function of the Mts system in methyl sulfide metabolism. Thus, no in vivo Mtr bypass appears to exist in M. acetivorans.

Insight into the poisoning effects and mechanisms of CH3SH, CH3CH2SH, CH3SCH3, and CH3CH2SCH2CH3 on Pt/C catalysts in fuel cell HOR

Trace amounts of sulphion can threaten the performance and lifespan of proton exchange membrane fuel cells (PEMFCs). The fuel mainly originates from refinery hydrogen, in which methyl mercaptan (MeSH), ethyl mercaptan (EtSH), dimethyl sulfide (DMS) and ethyl sulfide (EMS) inevitably exist. Herein, their negative effects are investigated on PEMFC and rotating disk electrode (RDE) levels, and the poisoning mechanisms are revealed by structural characterizations and density functional theory (DFT) calculations. The result indicates that MeSH and EtSH are 1.6 times more threatening than H2S, therefore, it is essential to limit the content of MeSH and EtSH. Nevertheless, the poisoning effect of DMS and EMS is weak enough to be tolerated. Moreover, the findings that the occupation of top site on Pt (111) weakly affects the hydrogen oxidation reaction (HOR) would contribute to the design of new catalysts with stronger toxicity resistance. This work is significant for the durability improvement of PEMFCs.

Highly efficient degradation of sulfur-containing volatile organic compounds by amorphous MnO2 at room temperature: Implications for controlling odor pollutants

Sulfur-Containing Volatile Organic Compounds (S-VOCs) are notorious for global air pollution due to their odorous characteristics and exhibiting adverse health effects. Nevertheless, the catalytic degradation of S-VOCs at low temperatures is still a tremendous challenge for air purification. In this study, methyl mercaptan (CH3SH), a typical S-VOCs contaminant, could be completely removed by amorphous MnO2 with high efficiency (100 %) for 40 h at room temperature, and demonstrating significantly enhanced stability (over 100 h) in the presence of 20 %RH (Relative humidity), which is far superior to the performance of previous reported catalysts. The amorphous MnO2 with surface-rich oxygen vacancies can trigger the formation of more reactive oxygen species (ROS) and stronger O2 adsorption capability comparing with the crystalline MnO2, the corresponding results are characterized by XPS and EPR. Moreover, In Situ-DRIFTS coupled with DFT calculations revealed that the CH3SH could be transformed into CO32-/SO42- by ROS. Unexpectedly, the amorphous MnO2 also displayed excellent activity and stability towards to other typical S-VOCs, which is beneficial for the actual industrial application. The findings can provide novel insights into the design of highly efficient and stable catalysts to eliminate odor gaseous pollutants over a broad operating concentration window at room temperature.

Corteva sentenced for criminal negligence after incident

A Corteva Agriscience subsidiary has pleaded guilty to criminal negligence, 8 years after an accidental chemical release killed four employees and injured several others at a now-defunct insecticide plant in La Porte, Texas. On April 24, a US district judge ordered the subsidiary, EIDP Inc., formerly E. I. du Pont de Nemours and Company Inc., to pay a $12 million penalty and make a $4 million community service payment to the National Fish and Wildlife Foundation. EIDP must also serve 2 years of probation, during which time the company must provide the US Probation Office full access to all its operating locations. The accident, which occurred on Nov. 15, 2014, at what was then a DuPont facility, released nearly 11 metric tons of highly toxic methyl mercaptan after plant workers tried to clear a section of blocked piping. A US Chemical Safety and Hazard Investigation Board probe after the incident

Corteva sentenced for criminal negligence 8 years after a methyl mercaptan leak killed 4 employees

Corteva sentenced for criminal negligence 8 years after a methyl mercaptan leak killed 4 employees

Engineering O‐Succinyl‐L‐Homoserine Mercaptotransferase for Efficient L‐Methionine Biosynthesis by Fermentation‐Enzymatic Coupling Route

AbstractL‐Methionine is the unique sulfur‐containing amino acid essential for humans and animals, which is widely used in pharmaceutical, food and feed industries. Its green and efficient production has attracted a great deal of attention. Fermentation‐enzymatic coupling route is regarded to be promising for L‐methionine biosynthesis, while O‐succinyl‐L‐homoserine mercaptotransferase (MetZ) is the key biocatalyst. Exploring and engineering of MetZ with ideal catalytic properties is highly desired. Herein, the MetZ from Chromobacterium violaceum (CvMetZ) was screened and through in silico analyses, potential beneficial amino acid residues both at the access channel and around the oxygen anion holes were anchored for site‐saturation mutagenesis. The positive mutants were obtained with improved activity for L‐methionine biosynthesis using O‐succinyl‐L‐homoserine (OSH) and methyl mercaptan as substrate. The best mutant was further applied for L‐methionine production and supply of methyl mercaptan was optimized in a fed‐batch approach. The conversion of 100 g/L OSH reached 92% with L‐methionine yield of 62.6 g/L, which was well coupled with the OSH fermentation level.magnified image

EMERGING TOOL FOR CONTROLLING POLLUTION : A REVIEW ARTICLE

The term "biotechnology" refers to the use of living organisms in man-made systems. Effluent treatment and fermentation both benefit from the employment of microorganisms. The widespread use of these methods could have a significant economic influence in fields including the development of novel pharmaceuticals, foods, and chemicals, the enhancement of agricultural goods, and the degradation of toxic wastes in substantial quantities. When it comes to cleaning the air in factories and cities of unpleasant odors and harmful chemicals, biotechnology provides the most cost-effective and eco-friendly solution. The environment and human health are both negatively impacted by the emission of volatile organic compounds (VOCs) and inorganic odorants. Odor-causing substances in the environment include ammonia, amines, hydrogen sulfide, methyl mercaptan, dimethyl sulfide. The need for air pollution control systems to provide peaceful, breathing air is developing as a result of rising population density and the construction of new residential areas and industrial units. This article offers a survey of the several biotechnological strategies now in use for reducing air pollution and unpleasant odors. Legal restrictions necessitate the elimination of odors and volatile organic compounds (VOCs) due to public complaints about poor air quality on-site and emission monitoring by enforcement agencies. Keywords- volatile organic compound (VOC), biotechnology, air pollution control. Cite this article- Akshita Tiwari, Shweta Sharma, Shweta Sharma, Parul Singh and Nupur Raghav, 2023 “Emerging Tool for Controlling Pollution: A Review Article” Journal of Science Innovations and Nature of Earth, Vol. 3(1), page- 52-58 www.doi.org/10.59436/https://jsiane.com/archives3/12/74

Screening Physical Solvents for Methyl Mercaptan Absorption Using Quantum Chemical Calculation Coupled with Experiments.

This work presents a screening method of physical solvents for methyl mercaptan (MeSH) absorption using quantum chemical calculations. The absorption solubility and thermodynamic behaviors of dimethyl sulfoxide (DMSO), sulfolane (SUL), propylene carbonate (PC), N,N-dimethylformamide (DMF), and 1-methyl-2-pyrrolidinone (NMP) for MeSH were calculated and analyzed using the COSMO-RS model, and the absorption mechanism was probed combining the quantum theory of atoms in molecules (QTAIM) and reduced density gradient (RDG). Results show that the absorption solubility of the five solvents for MeSH by COSMO-RS model calculations follow the order of NMP > PC > DMSO > SUL > DMF, and the van der Waals forces and hydrogen bond forces determine the absorption solubility of physical solvents for MeSH. In addition, the experimental results of MeSH Henry coefficients in the above five solvents follow the same order as the calculated results. However, the calculated Henry coefficients' value largely deviates from the experimental value; therefore, we believe that this calculation method is only available for qualitative screening. This work provided a feasible approach to screening high-performance physical solvents for MeSH removal.

Synergy effects of Methylomonas koyamae and Hyphomicrobium methylovorum under methanethiol stress.

Methanotrophs are able to metabolize volatile organic sulfur compounds (VOSCs), excrete organic carbon during CH4 oxidation, and influence microbial community structure and function of the ecosystem. In return, microbial community structure and environmental factors can affect the growth metabolism of methanotrophs. In this study, Methylomonas koyamae and Hyphomicrobium methylovorum were used for model organisms, and methanethiol (MT) was chosen for a typical VOSC to investigate the synergy effects under VOSC stress. The results showed that when Hyphomicrobium methylovorum was co-cultured with Methylomonas koyamae in the medium with CH4 used as the carbon source, the co-culture had better MT tolerance relative to Methylomonas koyamae and oxidized all CH4 within 120h, even at the initial MT concentration of 2000mgm-3. The optimal co-culture ratios of Methylomonas koyamae to Hyphomicrobium methylovorum were 4:1-12:1. Although MT could be converted spontaneously to dimethyl disulfide (DMDS), H2S, and CS2 in air, faster losses of MT, DMDS, H2S, and CS2 were observed in each strain mono-culture and the co-culture. Compared with Hyphomicrobium methylovorum, MT was degraded more quickly in the Methylomonas koyamae culture. During the co-culture, the CH4 oxidation process of Methylomonas koyamae could provide carbon and energy sources for the growth of Hyphomicrobium methylovorum, while Hyphomicrobium methylovorum oxidized MT to help Methylomonas koyamae detoxify. These findings are helpful to understand the synergy effects of Methylomonas koyamae and Hyphomicrobium methylovorum under MT stress and enrich the role of methanotrophs in the sulfur biogeochemical cycle. KEY POINTS: • The co-culture of Methylomonas and Hyphomicrobium has better tolerance to CH3SH. • Methylomonas can provide carbon sources for the growth of Hyphomicrobium. • The co-culture of Methylomonas and Hyphomicrobium enhances the removal of CH4 and CH3SH.

Interstitial carbon-platinum electronic metal-support interaction structure boost synergistic removal of O3 and CH3SH via surface atomic oxygen

Carbon atoms in the interstitial sites of metal nanoparticles have strong influence on heterogeneous catalysis via electronic metal-support interactions (EMSI). Here, the Pt catalysts with interstitial C-Pt EMSI structures were first developed and identified to boost the removal of ozone (O3) and methyl mercaptan (CH3SH). Experimental results showed that the intrinsic activity of the catalysts with low Pt loading (wt%, 0.95 %) was 186 times higher than that of commercial MnO2. This excellent catalytic performance was attributed to dual-site catalytic structures to promote the adsorption/activation of O3 at interstitial C and capture/oxidation of CH3SH at Pt simultaneously. More importantly, the interstitial C sites retained surface atomic oxygen (*O) with excellent reactivity and lowered the energy barrier of CS bond breakage, thus achieving efficient decomposition of CH3SH into CO2/SO42-. This work provides high-performance catalysts and new mechanistic insights for the synergistic control of O3 and CH3SH.