Dimethyl Disulfide Production Research Articles

Hydrogen sulfide production during early yeast fermentation correlates with volatile sulfur compound biogenesis but not thiol release.

Yeasts undergo intensive metabolic changes during the early stages of fermentation. Previous reports suggest the early production of hydrogen sulfide (H2S) is associated with the release of a range of volatile sulfur compounds (VSCs), as well as the production of varietal thiol compounds 3-sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA) from six-carbon precursors including (E)-hex-2-enal. In this study, we investigated the early H2S potential, VSCs/thiol output, and precursor metabolism of 11 commonly used laboratory and commercial Saccharomyces cerevisiae strains in chemically defined synthetic grape medium (SGM) within 12 hours after inoculation. Considerable variability in early H2S potential was observed among the strains surveyed. Chemical profiling suggested that early H2S production correlates with the production of dimethyl disulfide, 2-mercaptoethanol, and diethyl sulfide, but not with 3SH or 3SHA. All strains were capable of metabolizing (E)-hex-2-enal while the F15 strain showed significantly higher residue at 12 h. Early production of 3SH, but not 3SHA, can be detected in the presence of exogenous (E)-hex-2-enal and H2S. Therefore, the natural variability of early yeast H2S production contributes to the early output of selected VSCs, but the threshold of which is likely not high enough to contribute substantially to free varietal thiols in SGM.

Control of damping-off in tomato seedlings exerted by Serratia spp. strains and identification of inhibitory bacterial volatiles in vitro

Serratia marcescens can be a plant growth promoting bacteria (PGPB) and an opportunistic human and plant pathogen. We have identified and characterized strains of related species of Serratia and evaluated their biological control of damping-off of tomato seeds caused by Pythium cryptoirregulare. Serratia ureilytica, S. bockelmannii and S. nevei were identified by phylogenetic analysis of partial gyrB gene sequence and average nucleotide identity (ANI). Tomato seeds inoculated with S. ureilytica ILBB 145 showed higher germination percentage and reduced damping-off in greenhouse experiment resembling a commercial operation, and volatiles produced by this strain caused the nearly complete inhibition in vitro of P. cryptoirregulare. Analysis of volatile organic compounds (VOCs) showed that ILBB 145 produced dimethyl disulfide (DMDS), which can partially account for this inhibition. Serratia bockelmannii ILBB 162 performance against damping-off was intermediate and the inhibition of P. cryptoirregulare in vitro was lower and explained by volatile and diffusible metabolites. Both strains augmented DMDS production in the presence of P. cryptoirregulare, suggesting this compound may play a role in the context of interspecific competition. Serratia nevei ILBB 219 showed the lowest inhibition of P. cryptoirregulare in vitro, no DMDS production, and no biocontrol in planta. Draft genomes of the three strains were annotated and individual genes and biosynthesis gene clusters were identified in relation with the observed phenotypes. We report S. ureilytica – a low risk species- with activity as a biological control agent and DMDS produced by this bacterial species putatively involved in seed and seedling protection against P. cryptoirregulare.

Adsorption and thermal reactivity of dimethyl trisulfide on a Au(111) single-crystal surface

We investigated the adsorption and thermal reactivity of dimethyl trisulfide (DMTS, CH3SSSCH3) on a Au(111) single-crystal surface. X-ray photoelectron spectroscopy results indicated that at exposure temperatures of 100–300 K, DMTS dissociatively adsorbed as CH3S and CH3SS. That the dissociative adsorption rate was independent of exposure temperature suggested that DMTS dissociation on Au proceeded without an energy barrier at >100 K. In contrast, the thermal reactions of the adsorbed CH3S and CH3SS varied strongly with formation temperature. Specifically, after CH3S and CH3SS formed on Au(111) at 100 K, increasing the temperature resulted in associative desorption of CH3S as dimethyl disulfide (CH3SSCH3) and coupling reaction of CH3SS to ethane and atomic sulfur. In contrast, after CH3S and CH3SS formed at 150 K, increasing the temperature resulted not only in these two reactions but also in production of dimethyl disulfide and atomic sulfur by reaction between CH3S and CH3SS. At formation temperatures of 200 and 300 K, the only reaction observed was that between CH3S and CH3SS. These results suggest that the surface structure of the adsorbed species formed by DMTS dissociation on Au(111) depended on formation temperature. Specifically, at 100 K, dissociation of DMTS resulted in formation of CH3S and CH3SS islands on the Au(111) surface, whereas the two species were randomly adsorbed at higher formation temperatures.

Evaluation of clay aggregate biotrickling filters for treatment of gaseous emissions from intensive pig production

Treatment of ventilation air from livestock production by biological airfiltration has emerged as a cost-effective technology for reduction of emissions of odorants and ammonia. Volatile sulfur compounds from livestock production include H2S and methanethiol, which have been identified as potentially important odorants that are not removed sufficiently by biological air filters. Light-expanded clay aggregates (Leca®) is a biotrickling filter material that contains iron oxides, which can oxidize H2S and methanethiol, and thus potentially may help to remove these two compounds in biological air filters. This study used on-line PTR-MS measurements to investigate the performances of two Leca® biotrickling filters (abraded Leca® filter and untreated Leca® filter) for removal of odorants and ammonia emitted from an experimental pig house. The results indicated that the abraded Leca® filter had a similar or slightly better capability for removing odorants than the untreated Leca® filter. This may be due to the enlargement of the surface area by the friction process. The volatile sulfur compounds, however, were not removed efficiently by either of the two Leca® filters. Kinetic analysis of a ventilation controlled experiment during the first period indicated that Grau second-order kinetics could be applied to analyze the removal of sulfur compounds and other odorants, whereas the Stover-Kincannon model could only be applied to analyze the removal of odorants other than sulfur compounds, partly due to the limitation of mass transfer of these compounds in the biotrickling filters. In the last measurement period, a production of dimethyl disulfide and dimethyltrisulfide coinciding with strongly enhanced removal of methanethiol was observed for the untreated filter. This was assumed to be enhanced by an incidence of low local air velocity in the filter and indicated involvement of iron-catalyzed reactions in the removal of sulfur compounds.

Anaerobic Production of Methanethiol and Other Compounds by Brassica Vegetables

Methanethiol (MT) is a volatile compound responsible for the unpleasant odor evolved when fresh broccoli (Brassica oleracea L., Italica group) is held under anaerobic conditions. Inductive atmospheres can develop in storage, transportation containers, or modified atmosphere packages, resulting in reduced quality. To determine if related vegetables are capable of producing MT, 12 different vegetables from the genus Brassica were cut into ready-to-eat forms. Fifty-gram samples were sealed in 500-mL glass jars and flushed with N2. After 24 h in the dark at 20 °C, headspace samples from the jars were analyzed for MT and other volatiles. Headspace concentration of MT was greatest in broccoli florets, followed by pak choi (Brassica rapa L., Chinensis group) leaf blades, savoy cabbage (Brassica oleracea L., Capitata group), broccoflower (Brassica oleracea L., Botrytis group), and green and red cabbage (Brassica oleracea L., Capitata group). Broccoli stems, kale (Brassica oleracea L., Acephala group), Brussels sprouts (Brassica oleracea L., Gemmifera group), pak choi petioles, rutabaga (Brassica napus L., Napobrassica group) root, cauliflower (Brassica oleracea L., Botrytis group) florets, Chinese cabbage (Brassica rapa L., Pekinensis group), and kohlrabi (Brassica oleracea L., Gongylodes group) tubers produced <3% of the MT produced by broccoli florets. Green tissues appeared to have a greater capacity to produce MT than nongreen tissues. Anaerobic production of CO2 and ethanol did not relate to the vegetable's ability to produce MT. The production of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) were also induced by the anaerobic conditions. Green cabbage produced the greatest concentration of DMDS, followed by savoy cabbage and broccoli florets. Production of DMTS was similar to the pattern observed for MT, but DMDS production was not highly correlated with MT production.

MODELING THE GENERATION AND DISPERSION OF ODORS FROM MUSHROOM COMPOSTING FACILITIES

An odor source generation model and an odor dispersion model were developed to predict the local distribution of odors emanating from mushroom composting facilities. The odor source generation model allowed for simulation of various composting wharf configurations and odor source strengths. This model was linked to a Gaussianplume diffusion model that predicted odor dispersion. Dimethyl disulfide production at a rate of 1760 g/h was simulated by the source generation model and six different atmospheric conditions were analyzed to demonstrate the effect of wind speed, atmospheric stability, and source generation on the dispersion of this odor producing compound. Detectable levels of dimethyl disulfide were predicted to range from less than 100 m from the source during very unstable conditions to almost 5000 m during very stable conditions.

Methyl mercaptan and dimethyl disulfide production from methionine by Proteus species detected by head-space gas-liquid chromatography

Head-space gas-liquid chromatography and mass spectrometry were used to detect and identify products formed by Proteus vulgaris, P. mirabilis, P. morganii, and P. rettgeri from a defined medium supplemented with either phenylalanine, methionine, valine, leucine, histidine, lysine, ornithine, threonine, asparagine, aspartic acid, or tryptophan. In a detailed study of the products formed by 68 strains of Proteus spp. from L-methionine, the production of large amounts of both dimethyl disulfide and methyl mercaptan was found to be a characteristic of the genus. Both sulfur products appeared within a few hours of inoculation. Dimethyl disulfide was a more sensitive indicator of growth than the spectrometric determination of optical density. This suggests that it could be useful for the rapid, automated detection of any species of Proteus.

Development of specific tests for rapid detection of Escherichia coli and all species of Proteus in urine

Proteus mirabilis was distinguishable from Escherichia coli and from several other species that may be associated with urinary tract infections when grown in a nutrient medium supplemented with 0.1 M L-methionine by the formation of large amounts of dimethyl disulfide and methyl mercaptan, which were detected by head-space gas-liquid chromatography (HS-GLC). E. coli could be detected by the same HS-GLC technique by ethanol production from methionine peptone water enriched with 1% either lactose or arabinose but not by any product from 10 amino acids tested. Ethanol from lactose was detected early in the exponential phase of growth. Significant numbers, 10(5) or more per ml, of E. coli in urine could be detected in about 5 h by ethanol production from an unshaken culture of urine in lactose methionine peptone water buffered at pH 7.2 (urine test medium); only a trace of dimethyl disulfide was produced. Significant numbers of P. mirabilis in urine could be detected in 4 h by dimethyl disulfide production and in 5 h by methyl mercaptan production from a shaken culture of urine in urine test medium; no ethanol was produced. Incubation of urine specimens in the test medium followed by examination by HS-GLC is proposed as a rapid method of detecting whether or not the urine contains significant numbers of E. coli or a species of Proteus.