An airlift-recycle fermenter for microbial desulfurization of coal

Summary An airlift-external recycle fermenter has been constructed and used for the removal of pyritic sulfur from coal samples (4% initial total sulfur) by the thermophilic, sulfur oxidizing organism Sulfolobus acidocaldarius. The airlift fermenter behaved as a well mixed reactor. Approximately, 30% of initial pyritic sulfur has been removed from a 5% coal slurry of ~125 particle size, at a maximum rate of 1.8 mg S/l.h.     

Biological oxidation of thianthrene,thioxanthene and dibenzothiophene by the thermophilic organismSulfolobus acidocaldarius

Summary Microbial oxidation of some model aromatic organic sulfur compounds such as thianthrene, thioxanthene and dibenzothiophene by the thermophilic organismSulfolobus acidocaldarius has been studied. Sulfate ions released as an oxidation product were measured to quantify the oxidations. The oxidation of the aforementioned refractory aromatic sulfur compounds byS. acidocaldarius may have applications in organic sulfur removal from hydrocarbon fuels such as coal and oil.     

Physiological adsorption of Sulfolobus acidocaldarius on coal surfaces

Summary The adsorption of Sulfolobus acidocaldarius on bituminous coal surfaces and the respiration rate during adsorption at 70° C were enhanced at pH 1.0–2.0, in comparison with those at pH 3.0–5.0. The maximum number of bacterial cells adsorbed per unit area of coal attained a maximum (1.4 × 10¹¹ cells/m²) at pH 2.0. The rate of desulphurization at pH 2.2–2.5 was higher than at other pHs tested. Micrographs of S. acidocaldarius obtained by TEM and SEM indicated that the cells were adsorbed to the coal surfaces by extracellular slime. Specific inhibitors of membrane-bound ATPase (NaF, 20 mm) and respiration (NaN₃, 1 mm; KCN, 1 mm) had pronounced effects on suppressing adsorption. The amount of S. acidocaldarius adsorbed decreased when the coal particles were leached in advance with 2.0 m HNO₃. These facts lead to the conclusion that the adsorption of S. acidocaldarius on coal surfaces requires physiological activity relatd to respiration or energy conversion. Offprint requests to: V. B. Vitaya     

Sulfur cycling in a forested Sphagnum bog in northern Minnesota

The mass balance and internal cycle of sulfur within a small forested,Sphagnum bog in northern Minnesota are presented here based on a 4-year record of hydrologic inputs and outputs (precipitation, throughfall, streamflow, upland runoff) and a 3-year measurement of plant growth and sulfur uptake. Concentrations and accumulation rates of inorganic and organic sulfur species were measured in porewater. The bog is a large sink for sulfur, retaining 37% of the total sulfur input. Because of the relatively large export of organic S (21% of inputs), retention efficiency for total-S (organic S + SO ₄ ⁼ ; 37%) is less than that for SO ₄ ⁼ (58%). There is a dynamic cycle of oxidation and reduction within the bog. Annual oxidation and recycling of S is equal to total inputs in the center of the bog. Plants receive 47% of their uptake requirement from atmospheric deposition, 5% from retranslocation from foliage, and the remainder from sulfur remineralized from peat. Mineralization is most intense in the aerobic zone above the water table. Inorganic sulfur species comprise <5% of the total sulfur burden within the peat.     

Biological removal of pyritic sulfur from coal by the thermophilic organism Sulfolobus acidocaldarius

More than 90% of initial pyritic sulfur was removed from bituminous coal samples (containing 2.1% pyritic sulfur) using the thermophilic organism Sulfolobus acidocaldarius. Microbial desulfurization rate was improved nearly ten fold by adjusting the N/P and N/Mg ratios in the nutrient medium. Environmental conditions were optimized. The optimal values of temperature and pH were 70 degrees C and 1.5, respectively. The influence of certain process variables (such as coal pulp density, particle size, and initial cell number density) on the rate of pyritic sulfur removal were determined. A pulp density of 20%, particle size of D (p) < 48 mum, and an initial cell number density of 10(12) cells/g pyrite in coal were found to be optimal. The carbon dioxide enriched air did not improve the rate of pyritic sulfur removal compared to pure air at 10% pulp density of coal samples containing 2.1% pyritic sulfur. The kinetics of microbial leaching of pyritic sulfur from coal was investigated. The rate of leaching was found to be first order with respect to pyritic sulfur concentration in the reaction medium.     

Sulfhydrolase Activity in Sediments of Wintergreen Lake, Kalamazoo County, Michigan

The hydrolysis of p-nitrophenyl sulfate, p-nitrocatechol sulfate, and [³⁵S]sodium dodecyl sulfate was examined in anoxic sediments of Wintergreen Lake, Michigan. Significant levels of sulfhydrolase activity were observed in littoral, transition, and profundal sediment samples. Rates of sulfate formation suggest that the sulfhydrolase system would represent a major source of sulfate within these sediments. Sulfate formed by ester sulfate hydrolysis can support dissimilatory sulfate reduction as shown by the incorporation of ³⁵S from labeled sodium dodecyl sulfate into H₂³⁵S. Sulfhydrolase activity varied with sediment depth, was greatest in the littoral zone, and was sensitive to the presence of oxygen. Estimations of ester sulfate concentrations in sediments revealed large quantities of ester sulfate (~30% of total sulfur). Both total sulfur and ester sulfate concentrations varied with the sediment type and were two to three orders of magnitude greater than the inorganic sulfur concentration.     

Reduction of Sulfur Compounds in the Sediments of a Eutrophic Lake Basin

Concentrations of various sulfur compounds (SO₄²⁻, H₂S, S⁰, acid-volatile sulfide, and total sulfur) were determined in the profundal sediments and overlying water column of a shallow eutrophic lake. Low concentrations of sulfate relative to those of acid-volatile sulfide and total sulfur and a decrease in total sulfur with sediment depth implied that the contribution of dissimilatory sulfur reduction to H₂S production was relatively minor. Addition of 1.0 mM Na₂³⁵SO₄ to upper sediments in laboratory experiments resulted in the production of H₂³⁵S with no apparent lag. Kinetic experiments with ³⁵S demonstrated an apparent K_m of 0.068 mmol of SO₄²⁻ reduced per liter of sediment per day, whereas tracer experiments with ³⁵S indicated an average turnover time of the sediment sulfate pool of 1.5 h. Total sulfate reduction in a sediment depth profile to 15 cm was 15.3 mmol of sulfate reduced per m² per day, which corresponds to a mineralization of 30% of the particulate organic matter entering the sediment. Reduction of ³⁵S⁰ occurred at a slower rate. These results demonstrated that high rates of sulfate reduction occur in these sediments despite low concentrations of oxidized inorganic compounds and that this reduction can be important in the anaerobic mineralization of organic carbon.     

Measurement of organic-35S and organic-S in lake sediments: Methodological considerations

Three protocols for the determination of inorganic and organic sulfur fractions were tested for their suitability to estimate total indigenous organic sulfur (S_org) and³⁵S_org formed from added³⁵SO₄ ^2– in sediments of chemically dilute lakes in the ELA. The protocols tested have all been reported in the literature. It was found that two protocols involving sequential analyses for S fractions following acid treatment gave estimates of both S_org and³⁵S_org up to 87% lower than a non-sequential protocol. The low estimates were largely due to hydrolysis and solubilization of solid phase S which was then removed in a rinsing step. The non-sequential protocol, in which total reduced inorganic sulfur and total sulfur were determined on separate aliquots, is recommended as the most reliable of the three. Individual analyses in this protocol were verified for these lake sediments using a variety of S standards.     

Control of Oxidative Sulfur Metabolism of Chlorobium limicola forma thiosulfatophilum

A metered blend of anaerobic-grade N₂, CO₂, and H₂S gases was introduced into an illuminated, 800-ml liquid volume, continuously stirred tank reactor. The system, described as an anaerobic gas-to-liquid phase fed-batch reactor, was used to investigate the effects of H₂S flow rate and light energy on the accumulation of oxidized sulfur compounds formed by the photoautotroph Chlorobium limicola forma thiosulfatophilum during growth. Elemental sulfur was formed and accumulated in stoichiometric quantities when light energy and H₂S molar flow rate levels were optimally adjusted in the presence of nonlimiting CO₂. Deviation from the optimal H₂S and light energy levels resulted in either oxidation of sulfur or complete inhibition of sulfide oxidation. Based on these observations, a model of sulfide and sulfur oxidases electrochemically coupled to the photosynthetic reaction center of Chlorobium spp. is presented. The dynamic deregulation of oxidative pathways may be a mechanism for supplying the photosynthetic reaction center with a continuous source of electrons during periods of varying light and substrate availability, as in pond ecosystems where Chlorobium spp. are found. Possible applications for a sulfide gas removal process are discussed.     

A dynamic mathematical model for microbial removal of pyritic sulfur from coal

A dynamic mathematical model has been developed to describe microbial desulfurization of coal by Thiobacillus ferrooxidans. The model considers adsorption and desorption of cells on coal particles and microbial oxidation of pyritic sulfur on particle surfaces. The influence of certain parameters, such as microbial growth rate constants, adsorption-descrption constants, pulp density, coal particle size, initial cell and solid phase substrate concentration on the maximum rate of pyritic sulfur removal, have been elucidated. The maximum rate of pyritic sulfur removal was strongly dependent upon the number of attached cells per coal particle. At sufficiently high initial cell concentrations, the surfaces of coal particles are nearly saturated by the cells and the maximum leaching rate is limited either by total external surface area of coal particles or by the concentration of pyritic sulfur in the coal phase. The maximum volumetric rate of pyritic sulfur removal (mg S/h cm(3) mixture) increases with the pulp density of coal and reaches a saturation level at high pulp densities (e.g. 45%). The maximum rate also increases with decreasing particle diameter in a hyperbolic form. Increases in adsorption coefficient or decreases in the desorption coefficient also result in considerable improvements in this rate. The model can be applied to other systems consisting of suspended solid substrate particles in liquid medium with microbial oxidation occurring on the particle surfaces (e.g., bacterial ore leaching). The results obtained from this model are in good agreement with published experimental data on microbial desulfurization of coal and bacterial ore leaching.     

Sulfate Reduction in Peat from a New Jersey Pinelands Cedar Swamp

Microbial sulfate reduction rates in acidic peat from a New Jersey Pine Barrens cedar swamp in 1986 were similar to sulfate reduction rates in freshwater lake sediments. The rates ranged from a low of 1.0 nmol cm⁻³ day⁻¹ in February at 7.5- to 10.0-cm depth to 173.4 nmol cm⁻³ day⁻¹ in July at 5.0- to 7.5-cm depth. The presence of living Sphagnum moss at the surface generally resulted in reduced rates of sulfate reduction. Pore water sulfate concentrations and water table height also apparently affected the sulfate reduction rate. Concentrations of sulfate in pore water were nearly always higher than those in surface water and groundwater, ranging from 26 to 522 μM. The elevated pore water sulfate levels did not result from the evapotranspiratory concentration of infiltrating stream water or groundwater, but probably resulted from oxidation of reduced sulfur compounds, hydrolysis of ester sulfates present in the peat, or both. The total sulfur content of peat that had no living moss at the surface was 164.64 ± 1.5 and 195.8 ± 21.7 μmol g (dry weight)⁻¹ for peat collected from 2.5 to 5.0 and 7.5 to 10.0 cm, respectively. Organosulfur compounds accounted for 84 to 88% of the total sulfur that was present in the peat. C-bonded sulfur accounted for 91 to 94% of the organic sulfur, with ester sulfate being only a minor constituent. Reduced inorganic sulfur species in peat from 2.5 to 7.5 cm were dominated by H₂S-FeS (68%), while pyritic sulfide was the predominant inorganic sulfur species in the peat from depths of 7.5 to 10.0 cm (75%).     

Sulfur cycling in a forested Sphagnum bog in northern Minnesota

The mass balance and internal cycle of sulfur within a small forested,Sphagnum bog in northern Minnesota are presented here based on a 4-year record of hydrologic inputs and outputs (precipitation, throughfall, streamflow, upland runoff) and a 3-year measurement of plant growth and sulfur uptake. Concentrations and accumulation rates of inorganic and organic sulfur species were measured in porewater. The bog is a large sink for sulfur, retaining 37% of the total sulfur input. Because of the relatively large export of organic S (21% of inputs), retention efficiency for total-S (organic S + SO ₄ ⁼ ; 37%) is less than that for SO ₄ ⁼ (58%). There is a dynamic cycle of oxidation and reduction within the bog. Annual oxidation and recycling of S is equal to total inputs in the center of the bog. Plants receive 47% of their uptake requirement from atmospheric deposition, 5% from retranslocation from foliage, and the remainder from sulfur remineralized from peat. Mineralization is most intense in the aerobic zone above the water table. Inorganic sulfur species comprise <5% of the total sulfur burden within the peat.     

Histone-like protein in the Archaebacterium Sulfolobus acidocaldarius

The Archaebacterium Thermoplasma acidophilum contains a basic chromosomal protein remarkably similar to the histones of eukaryotes. Therefore, it was of interest to examine a different Archaebacterium for similar proteins. We chose to examine Sulfolobus acidocaldarius because it is thermophilic, like T. acidophilum, but nevertheless the two organisms are not particularly closely related. Two major chromosomal proteins were found in S. acidocaldarius. The smaller of these was soluble in 0.2 M H₂SO₄ and had a molecular weight of 14500. The larger was acid-insoluble and had a molecular weight of about 36000. Together, the proteins protected about 5% of the DNA against nuclease digestion and stabilized about 50% against thermal denaturation. Overall, the properties of these proteins were intermediate between those of the Escherichia coli protein HU and T. acidophilum protein HTa.     

Kinetics of the Removal of Iron Pyrite from Coal by Microbial Catalysis

Different strains of Thiobacillus ferrooxidans and Thiobacillus thiooxidans were used to catalyze the oxidative dissolution of iron pyrite, FeS₂, in nine different coal samples. Kinetic variables and parametric factors that were determined to have a pronounced effect on the rate and extent of oxidative dissolution at a fixed Po₂ were: the bacterial strain, the nitrogen/phosphorus molar ratio, the partial pressure of CO₂, the coal source, and the total reactive surface area of FeS₂. The overall rate of leaching, which exhibited a first-order dependence on the total surface area of FeS₂, was analyzed mathematically in terms of the sum of a biochemical rate, ν₁, and a chemical rate, ν₂. Results of this study show that bacterial desulfurization (90 to 98%) of coal samples which are relatively high in pyritic sulfur can be achieved within a time-frame of 8 to 12 days when pulp densities are ≤20% and particle sizes are ≤74 μm. The most effective strains of T. ferrooxidans were those that were isolated from natural systems, and T. ferrooxidans ATCC 19859 was the most effective pure strain. The most effective nutrient media contained relatively low phosphate concentrations, with an optimal N/P molar ratio of 90:1. These results suggest that minimal nutrient additions may be required for a commercial desulfurization process.     

34S tracer study of pollutant sulfate behaviour in a lowland peatland

Field experiments were carried out in order to assess the practicality and application of ³⁴SO₄ ^2? as a tracer of the physical and geochemical fate of aerially derived sulfur in peat. Six enclosures were isolated in a lowland peat with high historical acid sulfate inputs at Thorne Moors, UK, and treated with regular additions of 99.9% pure ³⁴SO₄ ^2? for 12 months. The total ³⁴S sulfate addition resulted in negligible change to the sulfate concentration, but allowed unequivocal change to the isotopic composition of sulfate inputs relative to pre-experiment control data set. Migration and biogeochemical transformations of the ³⁴S tracer were monitored via depth-specific sampling of surface and pore-waters every 6 weeks, and sacrificial sampling of solid peat at 12, 24, and 48 week intervals. Tracer incorporation into the various sulfur forms within the surface and pore-waters, vegetation, organic and inorganic fractions of the peat was apparent through strong positive deviation of δ³⁴S from natural values (in comparison with 18 months control data set for the same site). Consistency within enclosures is good and a detailed model of sulfur cycling within each enclosure can be established but natural variability in the control data and differences between replicate enclosures prevents more quantitative assessment. The ³⁴S tracer was initially rapidly removed from surface waters. The majority of uptake was by living vegetation (5.7–33% of tracer added, mean 17.6%), or through transformation to the organic fraction of the upper peat (25 cm) after rapid bacterial reduction of sulfate to sulfide. Despite penetration of ³⁴S labelled sulfate to deeper pore-waters over time, there was no significant reduction to sulfide or subsequent incorporation into organic or inorganic fraction at these depths (>25 cm); organic and inorganic sulfur, and pore-water sulfide retained their initial unlabelled isotopic compositions. This limitation on sulfur cycling at relatively shallow depth may be attributed to diminished labile organic matter inhibiting the activity of sulfate reducing bacteria or poisoning of sulfate reducers by high dissolved sulfide, after long-term sulfur pollution of this ecosystem.     

Impact of Atmospheric Sulfur Deposition on Sulfur Metabolism in Plants: H2S as Sulfur Source for Sulfur Deprived Brassica oleracea L.

Brassica oleracea L. was rather insensitive to atmospheric H₂S: growth was only negatively affected at ≥0.4 μl I^?1. Shoots formed a sink for H₂S and the uptake rate showed saturation kinetics with respect to the atmospheric concentration. The H₂S uptake rate was high in comparison with other species, which may reflect the high sulfur need of Brassica. The net uptake of sulfate by roots of hydroponically grown plants was substantially reduced after one week of exposure to 0.25 μl l^?1 H₂S, indicating that plants switched in part from sulfate to H₂S as sulfur source for plant growth. Plants were sulfur deficient after two weeks of sulfur deprivation, illustrated by reduced growth, which was more pronounced for shoots than for roots, and in enhanced shoot dry matter content. The latter could for the greater part be attributed to enhanced levels of soluble sugars and starch. Sulfur deficiency was further characterized by a low pigment content, extremely low levels of sulfate and water-soluble non-protein thiols, and by enhanced levels of nitrate and free amino acids, particularly in the shoots. Furthermore, sulfur deficient plants contained a lower total lipid content in shoots, whereas its content in roots was unaffected. The level of sulfolipids was decreased in both roots and shoots. When sulfur deprived plants were exposed to 0.25 μl I^?1 H₂S for one week, all sulfur deficiency symptoms were abolished and growth was restored. Furthermore, plants were able to grow with 0.4 μl I^?1 H₂S as the sole sulfur source. Water-soluble non-protein thiol content was enhanced in both shoots and roots of H₂S exposed plants, irrespective of the sulfate supply to the roots, whereas plants grown with H₂S as sole sulfur source contained very low sulfate levels. The interaction between atmospheric and pedospheric sulfur nutrition in plants is discussed.     

Enhanced removability of odorous sulfur-containing gases by mixed cultures of purified bacteria from peat biofilters

Four bacteria isolated from peat biofilters, Thiobacillus thioparus DW44, Thiobacillus sp. HA43, Xanthomonas sp. DY44 and Hyphomicrobium sp. I55, were selected to enhance the removal ratios of hydrogen sulfide (H₂S), methanethiol (MT) and dimethyl sulfide (DMS) in a mixed gas system. Two bacteria, DW44 and I55, which degrade H₂S, MT, DMS and dimethyl disulfide (DMDS), were mixed with DY44 or HA43 which degrade only H₂S and MT. Although DMS removal was significantly inhibited by the presence of H₂S and MT in a peat biofilter inoculated with the single bacterium, enhanced removability of H₂S, MT and DMS was observed by mixing Hyphomicrobium sp. I55 either with Thiobacillus sp. HA43 or Xanthomonas sp. DY44. The removal rate (g-S-kg-dry peat⁻¹·d⁻¹) by I55 after 8 d was 0.664 in total sulfur load, 0.827 g-S·kg-dry g-S·-kg-dry peat⁻¹·d⁻¹, but the rates by the mixed cultures of I55 plus HA43, and I55 plus DY44 were 0.760 and 0.801, respectively. In particular, DMS removability in mixed gases by a mixed culture of I55 and DY44 was almost equivalent to that by I55 when only DMS was supplied, suggesting that removal of H₂S and MT, which inhibited DMS removal, was preferentially conducted by DY44 and led to improved DMS removability by I55.     

Isolation of a strain of <Emphasis Type="Italic">Acidithiobacillus caldus</Emphasis> and its role in bioleaching of chalcopyrite

A moderately thermophilic and acidophilic sulfur-oxidizing bacterium named S₂, was isolated from coal heap drainage. The bacterium was motile, Gram-negative, rod-shaped, measured 0.4 to 0.6 by 1 to 2 μm, and grew optimally at 42–45°C and an initial pH of 2.5. The strain S₂ grew autotrophically by using elemental sulfur, sodium thiosulfate and potassium tetrathionate as energy sources. The strain did not use organic matter and inorganic minerals including ferrous sulfate, pyrite and chalcopyrite as energy sources. The morphological, biochemical, physiological characterization and analysis based on 16S rRNA gene sequence indicated that the strain S₂ is most closely related to Acidithiobacillus caldus (>99% similarity in gene sequence). The combination of the strain S₂ with Leptospirillum ferriphilum or Acidithiobacillus ferrooxidans in chalcopyrite bioleaching improved the copper-leaching efficiency. Scanning electron microscope (SEM) analysis revealed that the chalcopyrite surface in a mixed culture of Leptospirillum ferriphilum and Acidithiobacillus caldus was heavily etched. The energy dispersive X-ray (EDX) analysis indicated that Acidithiobacillus caldus has the potential role to enhance the recovery of copper from chalcopyrite by oxidizing the sulfur formed during the bioleaching progress.     

闽江河口互花米草入侵湿地土壤无机硫赋存形态及其影响因素

选择闽江河口鳝鱼滩的互花米草湿地为研究对象，基于时空互代法，探讨了不同互花米草入侵年限（SA1： 5-6 年；SA2： 8-10 年；SA3： 12-14年）湿地土壤的无机硫赋存形态及其主要影响因素。结果表明，随着互花米草入侵年限的增加，湿地土壤的水溶性硫（H₂O-S）含量整体呈增加趋势，而吸附性硫（Adsorbed-S）、盐酸可溶性硫（HCl-Soluble-S）和盐酸挥发性硫（HCl-Volatile-S）含量整体均呈降低趋势。相对于SA1，SA2、SA3土壤的H₂O-S含量分别增加了10.02%和2.68%，而其Adsorbed-S、HCl-Soluble-S和HCl-Volatile-S含量分别降低了9.02%、10.95%、7.57%和15.61%、32.89%、15.14%。湿地土壤的总无机硫（TIS）含量、TIS储量及其占全硫（TS）储量的比例均随互花米草入侵年限的增加而降低，且这种降低主要取决于Adsorbed-S、HCl-Soluble-S和HCl-Volatile-S的贡献。此外，随着互花米草入侵年限的增加，影响湿地土壤不同形态无机硫赋存的环境因子均发生了较大变化，其中土壤颗粒组成、EC和pH的改变对无机硫赋存形态的影响最为明显。研究发现，随着互花米草入侵年限的增加以及该区对互花米草定期刈割活动的进行，湿地土壤无机硫养分可能将继续降低并逐渐趋于缺乏状态，长期而言将减弱互花米草自身的入侵能力。