Degradation Of Dimethyl Sulfide Research Articles

Advancement of visible light-driven photocatalytic degradation of dimethyl sulfide by Zn doped rGO/TiO2

In this study, visible light-driven photocatalytic degradation of dimethyl sulfide (DMS) by nanocomposite photocatalyst was achieved through doping TiO2 with reduced graphene oxide (rGO) and various contents of Zn via solvothermal method. Doping of Zn led to formation of oxygen defects and presence of Ti3+ which further promoted photocatalytic activity. After modification, formation of lower level band gap between VB and CB reduced required energy for electron excitation and accelerated light energy utilization. Besides, the presence of surface oxygen vacancies enhanced photocatalytic activity via adsorption of exoteric oxygen. The best DMS conversion (almost 50 %) was performed by 0.1rGO/Zn1TiO2 under typical indoor environment at 60 % RH. Declining of relative humidity to below 10 % improved photocatalytic degradation of DMS due to lower competitive adsorption of water vapor. The best fitting by Langmuir-Hinshelwood kinetics model 4 also supported the occurrence of competitive adsorption with water vapor. Moreover, detection of generated intermediates was used in development of proposed reaction mechanism. Thus, the discussion on DMS photocatalytic degradation over Zn/rGO/TiO2 could be comprehensively conducted from the preparation, characterization, stability test, proposed reaction mechanism, and kinetic study.

Measurement of the Intramolecular Hydrogen-Shift Rate Coefficient for the CH3SCH2OO Radical between 314 and 433 K.

The intramolecular hydrogen-shift rate coefficient of the CH3SCH2O2 (methylthiomethylperoxy, MSP) radical, a product formed in the oxidation of dimethyl sulfide (DMS), was measured using a pulsed laser photolysis flow tube reactor coupled to a high-resolution time-of-flight chemical ionization mass spectrometer that measured the formation of the DMS degradation end product HOOCH2SCHO (hydroperoxymethyl thioformate). Measurements performed over the temperature range of 314-433 K yielded a hydrogen-shift rate coefficient of k1(T) = (2.39 ± 0.7) × 109 exp(-(7278 ± 99)/T) s-1 Arrhenius expression and a value extrapolated to 298 K of 0.06 s-1. The potential energy surface and the rate coefficient have also been theoretically investigated using density functional theory at the M06-2X/aug-cc-pVTZ level combined with approximate CCSD(T)/CBS energies yielding k1(273-433 K) = 2.4 × 1011 × exp(-8782/T) s-1 and k1(298 K) = 0.037 s-1 in fair agreement with the experimental results. Present results are compared with the previously reported values of k1(293-298 K).

RGO doped S0.05N0.1/TiO2 accelerated visible light driven photocatalytic degradation of dimethyl sulfide and dimethyl disulfide

In this study, modification of TiO2 was carried out by doping of non-metal elements (S and N) and various contents of reduced graphene oxide (rGO) for photocatalytic degradation of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS). Among the tested photocatalyst, 0.1wt%rGO/S0.05N0.1TiO2 had the best photocatalytic degradation efficiencies for both DMS and DMDS. Reduction of band gap and increment in surface area might be related to the improvement in photocatalytic activity. Examination was followed by the study of various parameters influence, reaction kinetics, and proposed reaction mechanism using 0.1wt%rGO/S0.05N0.1TiO2. Dry and 1% relative humidity in gases promoted photocatalytic activity yet higher water vapor contents led to adsorption competition and reduced DMS and DMDS conversion. Langmuir-Hinshelwood kinetics model 4 presented the best suited result for photocatalytic degradation of DMS and DMDS using 0.1wt%rGO/S0.05N0.1TiO2. Furthermore, proposed reaction mechanism for each type of pollutant was assembled from byproducts analysis during the reaction.

Microorganisms associated with Sporobolus anglicus, an invasive dimethylsulfoniopropionate producing salt marsh plant, are an unrecognized sink for dimethylsulfide.

BackgroundSaltmarshes are hotspots of organosulfur compound cycling due to production of dimethylsulfoniopropionate (DMSP) by benthic microorganisms, macroalgae, and saltmarsh vegetation. Degradation of DMSP is a source of dimethylsulfide (DMS), an important precursor for formation of secondary organic aerosol. Microorganisms degrading DMS play a role in controlling the amount of DMS available for emission into the atmosphere. Previous work has implicated sediment microbial populations as a major sink for DMS. Here, we show that Sporobolus anglicus (previously known as Spartina anglica), a widely distributed saltmarsh plant, is colonized by DMS-degrading microorganisms.MethodsDimethylsulfide degradation potential was assessed by gas chromatography and 13C-DMS stable isotope probing, microbial community diversity and functional genetic potential in phyllosphere and rhizosphere samples was assessed by high-throughput sequencing of 16S rRNA gene amplicons, cloning and sequencing of methanethiol oxidase genes, and by metagenomic analysis of phyllosphere microbial communities.ResultsThe DMS degradation potential of microbial communities recovered from phyllosphere and rhizosphere samples was similar. Active DMS-degraders were identified by 13C-DMS stable isotope probing and included populations related to Methylophaga and other Piscirickettsiaceae in rhizosphere samples. DMS-degraders in the phyllosphere included Xanthomonadaceae and Halothiobacillaceae. The diversity in sediment samples of the methanethiol oxidase (mtoX) gene, a marker for metabolism of methanethiol during DMS and DMSP degradation, was similar to previously detected saltmarsh mtoX, including those of Methylophaga and Methylococcaeae. Phyllosphere mtoX genes were distinct from sediment mtoX and did not include close relatives of cultivated bacteria. Microbial diversity in the phyllosphere of S. anglicus was distinct compared to those of model plants such as rice, soybean, clover and Arabidopsis and showed a dominance of Gammaproteobacteria rather than Alphaproteobacteria.ConclusionThe potential for microbial DMS degradation in the phyllosphere and rhizosphere of Sporobolus anglicus suggest that DMS cycling in saltmarshes is more complex than previously recognised and calls for a more detailed assessment of how aboveground activities affect fluxes of DMS.

Assembling UiO-66@TiO2 nanocomposites for efficient photocatalytic degradation of dimethyl sulfide

• DMS efficiently degraded by UiO-66@TiO 2 synthesized through a solvothermal method. • UiO-66 served as adsorbent, support and photocatalyst in UiO-66@TiO 2 composite. • Highest photodegradation efficiency of DMS observed at 60% relative humidity. • U1T3 showed advantageous photodegradation and cycling performance. • Photocatalytic mechanism and degradation kinetics of DMS were illustrated. The photocatalytic activity of titanium dioxide (TiO 2 ) for the purification of odour pollutants, containing reduced sulfur compounds (RSCs), could be largely improved by the coupling of porous materials. Herein, UiO-66@TiO 2 nanocomposites with different blending ratios were synthesized via a readily solvothermal method and characterized experimentally by XRD (X-ray diffraction), SEM (scanning electron microscope), FTIR (Fourier transform infrared spectrum), N 2 isotherms, and UV–vis DRS (diffuse reflectance spectra). The photodegradation performance of dimethyl sulfide (DMS) by synthesized UiO-66@TiO 2 was investigated under various photodegradation conditions, including photocatalyst dosage, DMS concentrations and relative humidity. The results showed that the U1T3 (UiO-66:TiO 2 = 1:3) composites exhibited the highest photocatalytic activity, which was about 17.8 and 7.1 times higher than that of pristine UiO-66 and TiO 2 , respectively. This indicates that the intimate contact interfaces between UiO-66 and TiO 2 could promote the separation and migration efficiency of photogenerated electron-hole pairs. When relative humidity increased from 0% to 60%, the photocatalytic activity was enhanced because the moisture could assist to produce more hydroxyl radicals. However, when the relative humidity was further increased to 90%, the excessive water would compete with DMS on the surface of UiO-66 and subsequently weaken the photocatalytic effects. During the cycling experiments, U1T3 showed a stable photocatalytic performance, and the plausible photocatalytic reaction mechanism and reaction pathways of DMS were proposed. With a significant enhancement of photocatalytic performance, UiO-66@TiO 2 nanocomposites could promote the practical applications of MOF-based photocatalysts for the degradation of DMS.

Simultaneous biodegradation of dimethyl sulfide and 1-propanethiol by Pseudomonas putida S-1 and Alcaligenes sp. SY1: "Lag" cause, reduction, and kinetics exploration.

Simultaneous biodegradation of malodorous 1-propanethiol (PT) and dimethyl sulfide (DMS) by Pseudomonas putida S-1 and Alcaligenes sp. SY1 was investigated and the interactions implicated were explored. Results showed that PT was completely degraded in 33 h, while a lag of 10 h was observed for DMS degradation alone, and the lag was even extended to 81 h in the binary mixture. Mechanism analysis found that the lag was mainly attributed to the exposure of DMS degrader (Alcaligenes sp. SY1), rather than PT metabolites and PT degrader. The exposure time and PT concentration also influenced the lag duration much. Citric acid could effectively reduce the lag. Pseudo-first-order model was proved suitable for the description of PT degradation, revealing that PT degradation could be enhanced in presence of DMS with a concentration of < 50 mg L-1. A modified Gompertz model, incorporated the lag phase, was developed for the description of DMS degradation in the mixture, revealing that DMS degradation depended on the initial PT concentration, and when the lag was not considered, PT with low-concentration could promote DMS biodegradation, while a higher concentration (> 20 mg L-1) cast negative effect.

Co-substrate-Assisted Dimethyl Sulfide Degradation and Electricity Generation in a Microbial Fuel Cell

Co-substrate-Assisted Dimethyl Sulfide Degradation and Electricity Generation in a Microbial Fuel Cell

Diversity of dimethylsulfide-degrading methanogens and sulfate-reducing bacteria in anoxic sediments along the Medway Estuary, UK.

Methane is a powerful greenhouse gas but the microbial diversity mediating methylotrophic methanogenesis is not well-characterized. One overlooked route to methane is via the degradation of dimethylsulfide (DMS), an abundant organosulfur compound in the environment. Methanogens and sulfate-reducing bacteria (SRB) can degrade DMS in anoxic sediments depending on sulfate availability. However, we know little about the underlying microbial community and how sulfate availability affects DMS degradation in anoxic sediments. We studied DMS-dependent methane production along the salinity gradient of the Medway Estuary (UK) and characterized, for the first time, the DMS-degrading methanogens and SRB using cultivation-independent tools. DMS metabolism resulted in high methane yield (39%-42% of the theoretical methane yield) in anoxic sediments regardless of their sulfate content. Methanomethylovorans, Methanolobus and Methanococcoides were dominant methanogens in freshwater, brackish and marine incubations respectively, suggesting niche-partitioning of the methanogens likely driven by DMS amendment and sulfate concentrations. Adding DMS also led to significant changes in SRB composition and abundance in the sediments. Increases in the abundance of Sulfurimonas and SRB suggest cryptic sulfur cycling coupled to DMS degradation. Our study highlights a potentially important pathway to methane production in sediments with contrasting sulfate content and sheds light on the diversity of DMS degraders.

Reaction of DMS and HOBr as a Sink for Marine DMS and an Inhibitor of Bromoform Formation

Recently, we suggested that hypobromous acid (HOBr) is a sink for the marine volatile organic sulfur compound dimethyl sulfide (DMS). However, HOBr is also known to react with reactive moieties of dissolved organic matter (DOM) such as phenolic compounds to form bromoform (CHBr3) and other brominated compounds. The reaction between HOBr and DMS may thus compete with the reaction between HOBr and DOM. To study this potential competition, kinetic batch and diffusion-reactor experiments with DMS, HOBr, and DOM were performed. Based on the reaction kinetics, we modeled concentrations of DMS, HOBr, and CHBr3 during typical algal bloom fluxes of DMS and HOBr (10-13 to 10-9 M s-1). For an intermediate to high HOBr flux (≥10-11 M s-1) and a DMS flux ≤10-11 M s-1, the model shows that the DMS degradation by HOBr was higher than for photochemical oxidation, biological consumption, and sea-air gas exchange combined. For HOBr fluxes ≤10-11 M s-1 and a DMS flux of 10-11 M s-1, our model shows that CHBr3 decreases by 86% compared to a lower DMS flux of 10-12 M s-1. Therefore, the reaction between HOBr and DMS likely not only presents a sink for DMS but also may lead to suppressed CHBr3 formation.

Removal of dimethyl sulfide by post-plasma catalysis over CeO2-MnOx catalysts and reaction mechanism analysis

The combination of a multistage rod plasma reactor and post CeO2-MnOx catalysts is studied to treat dimethyl sulfide (DMS). The physicochemical properties of all catalysts and the effect of the catalytic performance of CeO2-MnOx catalysts on DMS removal efficiency are studied. Placing CeO2-MnOx catalysts after the non-thermal plasma system can improve the capability of DMS degradation. The results exhibit that CeO2-MnOx (1:1) catalyst presents a higher catalytic activity than that of CeO2, MnOx, CeO2-MnOx (1:0.5) and CeO2-MnOx (1:3). At the power of 21.7 W, the combination of dielectric barrier discharge and CeO2-MnOx (1:1) catalyst could improve the DMS removal efficiency and CO2 selectivity by 16.2% and 18.2%, respectively. This result maybe closely related with its specific surface area, redox properties and oxygen mobility. In addition, the degradation mechanism of DMS over CeO2-MnOx catalysts is proposed. Finally, the stability of the CeO2-MnOx (1:1) catalyst is investigated, and the reason for the decreased activity of the used catalyst is analyzed.

Simultaneous methanethiol and dimethyl sulfide removal in a single-stage biotrickling filter packed with polyurethane foam: Performance, parameters and microbial community analysis.

The bio-treatment of methanethiol (MT) and dimethyl sulfide (DMS), the most common sulfur compounds in odorous gas, is difficult due to the inhibition of DMS degradation by MT. This article investigated the treatment of MT and DMS odorous gas using a single-stage biotrickling filter (BTF) packed with polyurethane foam cubes that were inoculated with activated sludge from a sewage treatment plant operating an anaerobic/aerobic/oxic (AAO) process. The BTF system lasted for 161 days (with 9 days to startup) under an empty gas residence time of 39s. The elimination capacities for MT and DMS were 85.2g/m3/h (removal efficiency=96.6%) and 6.4g/m3/h (removal efficiency=95.0%), respectively, and the maximal elimination capacities of MT and DMS were 119.7g/m3/h and 7.3g/m3/h, respectively. The optimal parameters were as follows: empty bed retention time, 39s; pH, 6.1; recirculation medium flow rate, ≥1.2m3/m2/h; temperature, 29-36°C; and SO42- concentration, < 2.0g-SO42-/L. Microbial community analysis revealed that spatial differentiation between MT-degrading bacteria and DMS-degrading bacteria enable the single-stage BTF can simultaneously remove MT and DMS. The activated sludge of AAO process can be used as the inoculation sludge to treating MT and DMS gas, which provides an important reference for the industrial application of treating odorous gas containing MT and DMS.

Fast Peroxy Radical Isomerization and OH Recycling in the Reaction of OH Radicals with Dimethyl Sulfide.

Dimethyl sulfide (DMS), produced by marine organisms, represents the most abundant, biogenic sulfur emission into the Earth's atmosphere. The gas-phase degradation of DMS is mainly initiated by the reaction with the OH radical forming first CH3SCH2O2 radicals from the dominant H-abstraction channel. It is experimentally shown that these peroxy radicals undergo a two-step isomerization process finally forming a product consistent with the formula HOOCH2SCHO. The isomerization process is accompanied by OH recycling. The rate-limiting first isomerization step, CH3SCH2O2 → CH2SCH2OOH, followed by O2 addition, proceeds with k = (0.23 ± 0.12) s-1 at 295 ± 2 K. Competing bimolecular CH3SCH2O2 reactions with NO, HO2, or RO2 radicals are less important for trace-gas conditions over the oceans. Results of atmospheric chemistry simulations demonstrate the predominance (≥95%) of CH3SCH2O2 isomerization. The rapid peroxy radical isomerization, not yet considered in models, substantially changes the understanding of DMS's degradation processes in the atmosphere.

A novel bacterial sulfur oxidation pathway provides a new link between the cycles of organic and inorganic sulfur compounds.

Dimethylsulfide (DMS) plays a globally significant role in carbon and sulfur cycling and impacts Earth's climate because its oxidation products serve as nuclei for cloud formation. While the initial steps of aerobic DMS degradation and the fate of its carbon atoms are reasonably well documented, oxidation of the contained sulfur is largely unexplored. Here, we identified a novel pathway of sulfur compound oxidation in the ubiquitously occurring DMS-degrader Hyphomicrobium denitrificans XT that links the oxidation of the volatile organosulfur compound with that of the inorganic sulfur compound thiosulfate. DMS is first transformed to methanethiol from which sulfide is released and fully oxidized to sulfate. Comparative proteomics indicated thiosulfate as an intermediate of this pathway and pointed at a heterodisulfide reductase (Hdr)-like system acting as a sulfur-oxidizing entity. Indeed, marker exchange mutagenesis of hdr-like genes disrupted the ability of H. denitrificans to metabolize DMS and also prevented formation of sulfate from thiosulfate provided as an additional electron source during chemoorganoheterotrophic growth. Complementation with the hdr-like genes under a constitutive promoter rescued the phenotype on thiosulfate as well as on DMS. The production of sulfate from an organosulfur precursor via the Hdr-like system is previously undocumented and provides a new shunt in the biogeochemical sulfur cycle. Furthermore, our findings fill a long-standing knowledge gap in microbial dissimilatory sulfur metabolism because the Hdr-like pathway is abundant not only in chemoheterotrophs, but also in a wide range of chemo- and photolithoautotrophic sulfur oxidizers acting as key players in global sulfur cycling.

Biogeochemistry of Dimethylsulfide, Dimethylsulfoniopropionate, and Acrylic Acid in the Changjiang Estuary and the East China Sea

AbstractThe distributions of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and acrylic acid (AA) were investigated in the Changjiang Estuary during winter (dry season) and summer (wet season) 2014 and in the East China Sea (ECS) during summer 2015. The rates of dissolved DMSP (DMSPd) degradation with DMS and AA production, DMS degradation, and AA degradation in the ECS were also studied. Significant seasonal variations in DMS(P) and AA concentrations were observed in the Changjiang Estuary with higher values during the wet season than during the dry season. The maximum ratio of AA/chlorophyll a (Chl a) occurred at the mouth of the Changjiang Estuary due to the combined effects of production from DMSP and terrestrial inputs from the Changjiang Estuary. The distributions of DMS(P) and AA in the ECS were dramatically influenced by the Kuroshio Current and the upwelling caused by the Taiwan Warm Current. The ratios of DMS(P)/Chl a and AA/Chl a exhibited similar patterns in the surface seawater of the ECS, which indicated that phytoplankton species and biomass might play important roles in controlling the distributions of DMS(P) and AA. In vertical profiles, high values of AA emerged in the upper water column and bottom seawater of the Changjiang Estuary. Meanwhile, the maxima of DMS(P) and AA generally appeared in the surface or euphotic layer, whereas their minima arose in the bottom seawater of the ECS. The degradation rates of DMSPd, DMS, and AA in the inshore waters were higher than those in the open sea.

A solid composite microbial inoculant for the simultaneous removal of volatile organic sulfide compounds: Preparation, characterization, and its bioaugmentation of a biotrickling filter

Volatile organic sulfide compounds (VOSCs) are usually resistant to biodegradation, thereby limiting the performance of traditional biotechnology dealing with waste gas containing such pollutants especially in mixture. In this study, a solid composite microbial inoculant (SCMI) was prepared to remove dimethyl sulfide (DMS) and propanethiol (PT). Given that the DMS degradation activity of Alcaligenes sp. SY1 is inducible and the PT-degradation activity of Pseudomonas putida S-1 is constitutive, different strategies are designed for cell cultivation to obtain high VOSC removal rates of SCMI. Compared with the microbial suspension, the prepared SCMI exhibited better storage stability at 4 and 25°C. Inoculation of the SCMI in biotrickling filters (BTFs) could effectively shorten the start-up period and enhance the removal performance. Microbial analysis by Illumina MiSeq indicated that Alcaligenes sp. SY1 and P. putida S-1 might be dominant and persistent among the microbial communities of the BTF during the operation.

Dominance of Oscillospira and Bacteroides in the bacterial community associated with the degradation of high-concentration dimethyl sulfide under iron-reducing condition

Microbial consumption of high-concentration dimethyl sulfide (DMS) under various redox conditions was investigated with freshwater sediments as inoculum. After about 1-year cyclic static enrichment at an initial DMS concentration of 10 mM, it was found that addition of ferric iron can lead to better DMS degradation efficiency compared to bicarbonate, nitrate, and oxygen as the electron acceptors especially, significantly higher than sulfate addition. The rate constant of DMS degradation was only 0.01106 ± 0.00139 day−1 under sulfate reduction, but increased to 0.02355 ± 0.00173 day−1 under iron reduction. Enriched bacterial communities under both aerobic and iron-reducing conditions were highly organized. Thus, the specialized bacterial communities were responsible for the different degradation conditions. The genera Thiobacillus and Pseudomona, which had been found previously to be capable of DMS degradation, belong to the most abundant bacteria in the aerobic microbial community. In the iron-reducing community, the four genera Oscillospira, Bacteroides, Parabacteroides, and Petrimonas are dominant, and in total account for 88 % of the total bacterial sequences. Species from the four anaerobic genera might be involved in ferric reduction and/or high-concentration DMS degradation. Thus, sediments in eutrophic lakes might harbor a diverse of functionally specific bacteria for DMS degradation.

Influence of vitamin B12 availability on oceanic dimethylsulfide and dimethylsulfoniopropionate

Environmental context Cobalamin, or vitamin B12, is receiving increased attention as a critical trace nutrient in the growth and metabolic processes of oceanic phytoplankton and bacterial communities. We present evidence that indicates B12 has a more significant role in the biogeochemical cycling of the climatically important compounds dimethylsulfide and dimethylsulfoniopropionate than previously understood. Several possible mechanisms are examined that link cellular-level processes involving B12 to global-scale biogeochemical processes involving the oceanic cycling of dimethylsulfoniopropionate and dimethylsulfide. Abstract Evidence is presented showing that dissolved dimethylsulfoniopropionate (DMSPd) and dimethylsulfide (DMS) concentrations are influenced by the availability of vitamin B12 in two oceanographically distinct regions with different DMS production capacities, the central equatorial Pacific Ocean and the Ross Sea, Antarctica. In both locations, addition of B12 to incubation experiments resulted in decreases in DMS and, in some cases, DMSPd concentrations relative to unamended controls. In no case did increasing iron availability significantly (α=0.1) alter DMS concentrations relative to controls. The relative decreases in DMS between B12 addition and control experiments were significant (α=0.1) in five of seven experiments conducted at ambient iron levels. Overall, DMS concentrations were on average 33.4% (±15.1%; 1 standard deviation) lower, relative to unamended controls, by the end of incubation experiments when B12 was added. Declines in DMSPd were observed in three of five experiments. Similar trends were observed when B12 was added to iron-supplemented bottle incubation experiments (30.4±10.4% lower final DMS concentrations in +B12Fe treatments relative to +Fe treatments). Several possible molecular-level explanations exist for this link between B12 and DMS production, including potential B12 dependence of methyltransferase enzymes involved in both DMS and DMSP degradation. Although the enzymology of these reactions remains unclear, the relationships described here provide evidence for plausible mechanisms behind the microbial modulation of oceanic DMS.

Revising upper-ocean sulfur dynamics near Bermuda: new lessons from 3 years of concentration and rate measurements

Environmental context Microscopic marine organisms have the potential to influence the global climate through the production of a trace gas, dimethylsulfide, which contributes to cloud formation. Using 3 years of observations, we investigated the environmental drivers behind the production and degradation of dimethylsulfide and its precursor dimethylsulfoniopropionate. Our results highlight the important role of the microbial community in rapidly cycling these compounds and provide an important dataset for future modelling studies. Abstract Oceanic biogeochemical cycling of dimethylsulfide (DMS), and its precursor dimethylsulfoniopropionate (DMSP), has gained considerable attention over the past three decades because of the potential role of DMS in climate mediation. Here we report 3 years of monthly vertical profiles of organic sulfur cycle concentrations (DMS, particulate DMSP (DMSPp) and dissolved DMSP (DMSPd)) and rates (DMSPd consumption, biological DMS consumption and DMS photolysis) from the Bermuda Atlantic Time-series Study (BATS) site taken between 2005 and 2008. Concentrations confirm the summer paradox with mixed layer DMS peaking ~90 days after peak DMSPp and ~50 days after peak DMSPp:Chl. A small decline in mixed layer DMS was observed relative to those measured during a previous study at BATS (1992–1994), potentially driven by long-term climate shifts at the site. On average, DMS cycling occurred on longer timescales than DMSPd (0.43±0.35 v. 1.39±0.76 day–1) with DMSPd consumption rates remaining elevated throughout the year despite significant seasonal variability in the bacterial DMSP degrader community. DMSPp was estimated to account for 4–5% of mixed layer primary production and turned over at a significantly slower rate (~0.2 day–1). Photolysis drove DMS loss in the mixed layer during the summer, whereas biological consumption of DMS was the dominant loss process in the winter and at depth. These findings offer new insight into the underlying mechanisms driving DMS(P) cycling in the oligotrophic ocean, provide an extended dataset for future model evaluation and hypothesis testing and highlight the need for a reexamination of past modelling results and conclusions drawn from data collected with old methodologies.

Characterization of the novel dimethyl sulfide-degrading bacterium Alcaligenes sp. SY1 and its biochemical degradation pathway

Recently, the biodegradation of volatile organic sulfur compounds (VOSCs) has become a burgeoning field, with a growing focus on the reduction of VOSCs. The reduction of VOSCs encompasses both organic emission control and odor control. Herein, Alcaligenes sp. SY1 was isolated from active sludge and found to utilize dimethyl sulfide (DMS) as a growth substrate in a mineral salt medium. Response surface methodology (RSM) analysis was applied to optimize the incubation conditions. The following conditions for optimal degradation were identified: temperature 27.03°C; pH 7.80; inoculum salinity 0.84%; and initial DMS concentration 1585.39μM. Under these conditions, approximately 99% of the DMS was degraded within 30h of incubation. Two metabolic compounds were detected and identified by gas chromatography–mass spectrometry (GC–MS): dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS). The DMS degradation kinetics for different concentrations were evaluated using the Haldane–Andrews model and the pseudo first-order model. The maximum specific growth rate and degradation rate of Alcaligenes sp. SY1 were 0.17h−1 and 0.63gsgx−1h−1. A possible degradation pathway is proposed, and the results suggest that Alcaligenes sp. SY1 has the potential to control odor emissions under aerobic conditions.

Removal of Dimethyl Sulphide in a Biotrickling Filter under Thermophilic Conditions

Biotrickling filter (BTF) of odorous containing dimethyl sulfide (DMS) emitted from the sewage sludge drying under thermophilic conditions was investigated. DMS removal efficiencies in the BTF achieved 50%, 65%, 75% at 40, 50, 60°C , respectively. The elimination capacities at 60°C was higher than that of biotrickling filter at 50°C or 40°C. At a bed contact time of 34.4 s, the elimination capacities at 60°C in the BTF was 14 g-DMS.m-3.h-1, which was higher than that of mesophilic biofilter. Sulfur dioxide (SO2) has inhibitory effect to the microbial activity for dimethyl sulfide degradation. Bacterial communities in the BTF, which were assessed by PCR-DGGE, play the dominant role in the biological processes of metabolism, sulfur oxidation, sulfate-reducing and carbon oxidation under thermophilic conditions. These results show that thermophilic biotrickling filter is achievable and open new possibilities for applying BTF to hot odour gas streams from sewage sludge drying.