Desulfurization of dibenzothiophene, benzothiophene, and other thiophene analogs by a newly isolated bacterium, Gordonia alkanivorans strain 1B

A novel bacterium, Gordonia alkanivorans strain 1B, was isolated from hydrocarbon-contaminated soil. Assessment of the biodegradation of distinct organic sulfur-compounds, such as dibenzothiophene (DBT), benzothiophene (BT), DBT sulfone, and alkylated tiophenic compounds, as the sole source of sulfure was investigated. G. alkanivorans strain 1B was able to remove selectively the sulfur from DBT while keeping intact the remaining carbon-carbon structure. Orthophenyl phenol (2-hydroxybiphenyl) was the only detected metabolic product. The bacterial desulfurization activity was repressed by sulfate. G. alkanivorans straini 1B consumed 310 μM DBT after 120 h of cultivation, corresponding to a specific desulfurization rate of 1.03 μmol/(g of dry cells·h). When an equimolar mixture of DBT/BT was used as a source of sulfur in the growth medium, G. alkanivorans strain 1B assimilated both compounds in a sequential manner, with BT as the preferred source of sulfur. Only when BT concentration was decreased to a very low level was DBT utilized as the source of sulfur for bacterial growth. Thespecific desulfurization overall rates of BT and DBT obtained were 0.954 and 0.813 μmol/(g of dry cells·h), respectively. The newly isolated G. alkanivorans strain 1B has good potential for application in the biodesulfurization of fossil fuels.     

Biological decomposition of Na<Subscript>2</Subscript>S<Subscript>2</Subscript>O<Subscript>3</Subscript> into sulfur by a newly isolated facultative thermophilic alkaline desulphuricant strain

A facultative thermophilic alkaline desulphuricant strain named GDJ-3 was isolated from neutral soils, enriched on sulfur synthetic medium, and detected in previous work. Conventional and chemotaxonomic analyses and 16s RNA gene sequencing showed that the strain was in good agreement with Alpha proteobacterium sp. (97%) and ochrobactrum sp. (98%). The regenerative processes of the solution containing sulfur compounds (SCS) from the strain through an orthogonal test were investigated to get the optimum regenerative condition. The results showed that regenerative temperature, air flow, and stirring speed of the agitator were the main three variables influencing the regenerative processes of the SCS. The optimum regenerative efficiency of the SCS from the strain was obtained when temperature, air flow, and stirring speed of the agitator were 318.2 K, 3.0 L/min, and zero r/min, respectively. Under this condition, when the cell concentration of the strain was adjusted to 10⁷/mL, the concentrations of Na₂S₂O₃ and Na2S in the SCS decreased from 112.68 g/L to 96.88 g/L and from 0. 87 g/L to 0.11 g/L in 9.5 h. Meanwhile, XRD spectrum shows that sulfur was formed in the regeneration process. These results suggest that the strain has potential application to the regeneration of the industrial solution containing sulfur compounds. Supported by Yongfeng Boyuan Industry Co., Ltd., Jiangxi Province, China     

Conversion of hydrogen sulfide to elemental sulfur byChlorobium thiosulfatophilum in a CSTR with a sulfur-settling separator

Chlorobium thiosulfatophilum may be used for the bioconversion of hydrogen sulfide to elemental sulfur or sulfate. Sulfur is the preferred product because of problems in the disposal of sulfate. A CSTR with a sulfur-settling separator has been used to preferentially produce and recover elemental sulfur. The simple nutritional requirements of the bacterium and differences in densities and average cell and sulfur particle sizes make a CSTR with a sulfur-settling separator attractive. A bench-scale study has been carried out to determine the optimum process conditions to maximize H₂S conversion, cell growth, elemental sulfur production, and to minimize sulfate production. The liquid effluent typically contained about 425–550 mg/L elemental sulfur. The sulfate concentration was maintained at levels below 100 mg/L. It was possible to remove up to 57 Μmol min⁻¹ L⁻¹ of H₂S from the gas stream. An experiment over a period of 392 h showed stable performance. For Presentation at the Fifteenth Symposium on Biotechnology for Fuels and Chemicals, Colorado Springs, CO.     

Formation and characterization of Cu<Subscript>x</Subscript>S layers on polyethylene film using the solutions of sulfur in carbon disulfide

Results of the formation of copper sulfide layers using the solutions of elemental sulfur in carbon disulfide as precursor for sulfurization are presented. Low density polyethylene film can be effectively sulfurized in the solutions of rhombic (α) sulfur in carbon disulfide. The concentration of sulfur in polyethylene increases with the increase of the temperature and concentration of sulfur solution in carbon disulfide and it little depends on the duration of sulfurization. Electrically conductive copper sulfide layers on polyethylene film were formed when sulfurized polyethylene was treated with the solution of copper (II/I) salts. Cu_xS layer with the lowest sheet resistance (11.2 Ω cm⁻²) was formed when sulfurized polyethylene was treated with copper salts solution at 80°C. All samples with formed Cu_xS layers were characterized by X-ray photoelectron spectroscopy. XPS analysis of obtained layers showed that on the layer’s surface and in the etched surface various compounds of copper, sulfur and oxygen are present: Cu₂S, CuS, CuO, S₈, CuSO₄, Cu(OH)₂ and water. The biggest amounts of CuSO₄ and Cu(OH)₂ are present on the layer’s surface. Significantly more copper sulfides are found in the etched layers.     

New photocatalysts based on cadmium and zinc sulfides for hydrogen evolution from aqueous Na<Subscript>2</Subscript>S-Na<Subscript>2</Subscript>SO<Subscript>3</Subscript> solutions under irradiation with visible light

Noble metal-free, Cd_{1 − x} Zn _x S-based photocatalysts for hydrogen evolution from aqueous solutions of sodium sulfide and sodium sulfite upon irradiation with visible light (λ > 420 nm) have been synthesized and characterized by a complex of physicochemical methods. The effects of pH and catalyst and substrate concentrations on the rate of photocatalytic hydrogen evolution have been investigated. Under the optimal conditions, the quantum efficiency of the process is up to 12.9%.     

Biotransformation of (−)β-pinene by Aspergillus niger ATCC 9642

The main objective of this work was to investigate the biotransformations of (−)α-pinene, (−)β-pinene, and (+) limonene by Aspergillus niger ATCC 9642. The culture conditions involved—concentration of cosolvent (EtOH), substrate applied, and sequential addition of substrates—were investigated. Adaptation of the precultures with small amounts of substrate was also studied. The experiments were performed in conical flasks with liquid cultures. This strain of A. niger was able to convert only (−)β-pinene into α-terpineol. An optimum conversion of (−)β-pinene into α-terpineol of about 4% was obtained when the substrate was applied as a diluted solution in EtOH and sequential addition of substrate was used.     

Bioaccumulation and biosorption of stable strontium and <Superscript>90</Superscript>Sr by <Emphasis Type="Italic">Oscillatoria homogenea</Emphasis> cyanobacterium

The ability of living filamentous cells of the cyanobacterium Oscillatoria homogenea to separate stable strontium and ⁹⁰Sr from aqueous solution is demonstrated in this study. On a basis of filamentous cell biovolume, the removal were 43.78 nM·ml·(mm³)⁻¹ and 3129.48 mBq·ml·(mm³)⁻¹ after 240 hour incubation. The optimum pH for strontium uptake is 9±0.3. The increasing biovolume of the blue-green alga elevates sorption. In the liquid culture containing 21.2 mm³·ml⁻¹ filamentous cells and 1000 nM·ml⁻¹ initial strontium concentration, the maximum strontium removal was 455.34 nM·ml·(mm³)⁻¹. At 1200 Lux illumination, the maximum removal value was 58.62 nM·ml·(mm³)⁻¹, and at the initial strontium concentration of 6590 nM·ml⁻¹, 235.40 nM·ml·(mm³)⁻¹ removal was observed. The experimental data fitted to Langmuir isotherm and the model parameters and correlation coefficient (R ²) were q _max = 7.143 μg·(mm³)⁻¹, b = 0.003 and 0.99, respectively.     

Nature of the silver precipitation obtained by cementation from thiosulphate solutions

The morphology and composition of the deposits formed on the surface of magnesium disk during cementation from thiosulphate solutions (0.0025–0.1M) [Ag(S₂O₃)₂]³⁻ + 0.5M S₂O₃ ²⁻ have been studied. A porous deposit with low adhesion is formed on the surface of the magnesium metal substrate. Within a wide range of [Ag(S₂O₃)₂]³⁻ ion concentrations, sulfur as well as silver are constituents of the deposit at the initial stages of cementation and at the end of the reaction. This is attributed to the electrochemical behaviour of magnesium in thiosulphate solutions resulting in the exceeding of current limit on cathode for pure silver reduction. Hence, parallel electrochemical reactions take place that are very close in their values to the standard redox potentials of reduction of [Ag(S₂O₃)₂]³⁻ ions to Ag⁰ and S₂O₃2− ions to S²⁻. Sulfur content in the cement deposits increases with the decrease in [Ag(S₂O₃)₂]³⁻ ion concentration and increase in cementation time. This tendency is also observed with the decreasing solution temperature.     

Photochemical synthesis of cadmium sulfide nanoparticles

The formation of cadmium sulfide nanoparticles upon UV irradiation of aqueous solutions of cadmium thiosulfates was established on the basis of spectroscopic and macroscopic data. The yield and size of the cadmium sulfide nanoparticles depend on the ratio of cadmium to thiosulfate ions in solution, the concentration of the solution, and the irradiation duration. The cadmium sulfide nanoparticles with a diameter of 4 nm were obtained by the photolysis of solutions with a concentration of 10⁻³ mol L⁻¹ at the ratio S₂O₃ ²⁻: Cd²⁺ = 2: 1.     

A Novel Glutamate Transport System in Poly(γ-Glutamic Acid)-Producing Strain <Emphasis Type="Italic">Bacillus subtilis</Emphasis> CGMCC 0833

Bacillus subtilis CGMCC 0833 is a poly(γ-glutamic acid) (γ-PGA)-producing strain. It has the capacity to tolerate high concentration of extracellular glutamate and to utilize glutamate actively. Such a high uptake capacity was owing to an active transport system for glutamate. Therefore, a specific transport system for l-glutamate has been observed in this strain. It was a novel transport process in which glutamate was symported with at least two protons, and an inward-directed sodium gradient had no stimulatory effect on it. K _m and V _m for glutamate transport were estimated to be 67 μM and 152 nmol⁻¹ min⁻¹ mg⁻¹ of protein, respectively. The transport system showed structural specificity and stereospecificity and was strongly dependent on extracellular pH. Moreover, it could be stimulated by Mg²⁺, NH₄⁺, and Ca²⁺. In addition, the glutamate transporter in this strain was studied at the molecular level. As there was no important mutation of the transporter protein, it appeared that the differences of glutamate transporter properties between this strain and other B. subtilis strains were not due to the differences of the amino acid sequence and the structure of transporter protein. This is the first extensive report on the properties of glutamate transport system in γ-PGA-producing strain.     

Sulfurization of polymers

Polyethylene is exhaustively sulfurized by elemental sulfur at 160–365 °C to release hydrogen sulfide and form black lustrous powders (sulfur content ≈80%) that possess electric conductivity (10⁻⁶–10⁻⁸ S cm⁻¹ when doped with I₂). Elemental analysis data, IR spectra, X-ray patterns, DSC-TGA. derivatographic data, electric conductivity, and mass spectrometric characteristics of the polymers synthesized suggest the presence of fused polythienothiophene and polynaphthothienothiophene blocks in the polymers. For Part 1, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 865–871, May, 2000.     

Vanadophosphoric Acid as a Modified Reagent for the Spectrophotometric Determination of Certain Cephalosporins and their Dosage Forms

Summary.  Vanadophosphoric acid in acidic medium is proposed as a modified reagent for the spectrophotometric determination of cephalexin, cephaprine sodium, cefazolin sodium, and cefotaxime in pure samples and in pharmaceutical preparations. The method is based on acid hydrolysis of cephalosporins and subsequent oxidation with vanadophosphoric acid. The resulting solution exhibits maximum absorption at about 516 nm. The effects of reaction conditions were investigated. Lambert-Beer’s law was obeyed over a concentration range of about 0.4–45 μg · cm⁻³. For more accurate results, Ringbom optimum concentration ranges were obtained, and the molar absorptivities and Sandell sensitivities were derived. The proposed method was applied to the determination of the drugs in pharmaceutical formulations; the results demonstrated that the proposed method is as accurate, pecise, and reproducible as the official methods. Received August 13, 1999. Accepted (revised) December 7, 1999     

Sulfurization of polymers

Polyethylene exhaustively sulfurized with elemental sulfur shows paramagnetic (spin concentration 2.7–9.7·10¹⁹ sp g⁻¹,g=2.0041–2.0045, ΔH=0.53–0.62 mT) and redox properties, which was demonstrated by both voltammetric and chemical methods (sodium reduction in liquid ammonia). The high concentration of unpaired electrons, the character of the electrochemical activity, and the chemical properties are in agreement with the presence in the polymers of polyconjugated ladder polythiophene and parquet polynaphtho-thienothiophene structures along with polyene-polysulfide blocks. The use of the polymers under consideration as an active cathode material in lithium batteries enables their repeated cycling with a specific charge capacitance of 150–340 mA hg⁻¹.     

A Laccase of <Emphasis Type="Italic">Fomes durissimus</Emphasis> MTCC-1173 and Its Role in the Conversion of Methylbenzene to Benzaldehyde

A laccase has been purified from the liquid culture growth medium containing bagasse particles of Fomes durissimus. The method involved concentration of the culture filtrate by ultrafiltration and anion exchange chromatography on diethyl aminoethyl cellulose. The sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis both gave single protein band indicating that the enzyme preparation was pure. The molecular mass of the purified laccase determined from SDS-PAGE analysis was 75 kDa. Using 2,6-dimethoxyphenol as the substrate, the determined K _m and k _cat values of the laccase are 182 μM and 0.35 s⁻¹, respectively, giving a k _cat/K _m value of 1.92 × 10³ M⁻¹ s⁻¹. The pH and temperature optimum were 4.0 and 35 °C, respectively. The purified laccase has yellow colour and does not show absorption band around 610 nm found in blue laccases. Moreover, it transformed methylbenzene to benzaldehyde in the absence of mediator molecules, property exhibited by yellow laccases.     

Preparation of WO<Subscript>3</Subscript>-SBA-15 mesoporous molecular sieve and its performance as an oxidative desulfurization catalyst

The tungsten-containing mesoporous molecular sieve WO₃-SBA-15 (SBA: Santa Barbara Amorphous type materials) was prepared under conventional hydrothermal conditions in strong acidic solution using H₂WO₄ as tungsten source, tetraethyl orthosilicate as silicon source, and a mixture of P123 tri-block copolymer (EO₂₀PO₇₀EO₂₀) and cetyltrimethylammonium bromide as structure-directing agent. The catalyst was tested for oxidative desulfurization and characterized by X-ray diffraction and nitrogen adsorption–desorption. The catalyst had the highest desulfurization performance (i.e., 91.3%) after oxidation under the following reaction conditions: 20 mL gasoline with 540 ppm sulfur, 6 mol H₂O₂/sulfur, reaction temperature 333 K, reaction time 80 min, and three extraction cycles.     

Production of Lipids Containing High Levels of Docosahexaenoic Acid by a Newly Isolated Microalga, <Emphasis Type="Italic">Aurantiochytrium</Emphasis> sp. KRS101

In the present study, a novel oleaginous Thraustochytrid containing a high content of docosahexaenoic acid (DHA) was isolated from a mangrove ecosystem in Malaysia. The strain identified as an Aurantiochytrium sp. by 18S rRNA sequencing and named KRS101 used various carbon and nitrogen sources, indicating metabolic versatility. Optimal culture conditions, thus maximizing cell growth, and high levels of lipid and DHA production, were attained using glucose (60 g l⁻¹) as carbon source, corn steep solid (10 g l⁻¹) as nitrogen source, and sea salt (15 g l⁻¹). The highest biomass, lipid, and DHA production of KRS101 upon fed-batch fermentation were 50.2 g l⁻¹ (16.7 g l⁻¹ day⁻¹), 21.8 g l⁻¹ (44% DCW), and 8.8 g l⁻¹ (40% TFA), respectively. Similar values were obtained when a cheap substrate like molasses, rather than glucose, was used as the carbon source (DCW of 52.44 g l⁻¹, lipid and DHA levels of 20.2 and 8.83 g l⁻¹, respectively), indicating that production of microbial oils containing high levels of DHA can be produced economically when the novel strain is used.     

Dyeing behaviour of lyocell fabric: effect of NaOH pre-treatment

To understand the effect of alkali pre-treatment on the dyeing of lyocell fabrics, samples are pre-treated with 0.0–7.0 mol dm⁻³ NaOH using a pad-batch process and then dyed with different types of reactive dyes. Exhaustion, fixation, and visual colour strength (K/S values) are measured. It is observed that sodium hydroxide pre-treatment significantly improves the colour yield, exhaustion, and fixation for all dyes used. Highest K/S values are obtained when the fabrics are pre-treated with 2.0–2.5 mol dm⁻³ NaOH. Cross-sectional analysis shows that below this optimum concentration the core fibres in the yarn are not dyed; at optimum concentration all fibres in yarn cross-section are homogeneously dyed. Cross-sectional analysis shows that as the pre-treatment concentration of NaOH increases above 2.5 mol dm⁻³, the fibres change progressively from a circular to angular cross-section, forming a solid unit. The decrease in K/S above the treatment concentration of 2.5 mol dm⁻³, though the %E and %F remains almost constant, is attributed to the distribution of dye over a larger surface area of the outer fibres in the yarn cross section, forcing the K/S at λ_max to decrease. This paper was presented at the 2nd International Cellulose Conference, Tokyo, Japan, 24th October 2007.     

Continuous Monitoring of Sulfur Dioxide with a Gas Permeation Denuder-Based System

 This study describes a continuous flow procedure for monitoring atmospheric sulfur dioxide using a planar gas permeation denuder (GPD) and a fiber optic spectrometer. When gaseous samples are directed through a GPD which consists of a gas-permeable membrane of poly(vinylidene) difluoride and two perspex blocks with engraved channels of mirror image, the fraction of sulfur dioxide passing the membrane is absorbed in a flowing stream of 5.0×10⁻⁴ mol L⁻¹ 5,5′-dithiobis(2,2′-dinitrobenzoic acid) (DTNB) in 0.025 mol L⁻¹ phosphate buffer of pH 7.0, and reacts with DTNB to yield a yellow product. This product is monitored spectrophotometrically at 410 nm with a miniature charge-coupled device (CCD) fiber optic spectrometer. The analytical range of sulfur dioxide is easily adjusted via the flow rate of DTNB solution, normally from 200 ppb to 94 ppm (v/v). The procedure is hardly interfered with by coexisting metal and non-metal species, except for hydrogen sulfide in the atmosphere. The error caused by hydrogen sulfide at a sulfur dioxide level (in ppm) of 2% is less than ±10%. With the proposed procedure, the result for a mimetic air sample is very close to that of the ultraviolet fluorescence method. Correspondence: College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China. e-mail: yli@chem.pku.edu.cn Received August 12, 2002; accepted November 9, 2002     

Electrochemical nanogravimetric studies of sulfur/sulfide redox processes on gold surface

Electrochemical quartz crystal microbalance, combined with cyclic voltammetric, chronoamperometric, and potentiostatic measurements, was used to study electrodeposition/dissolution phenomena at a gold electrode in solutions containing Na₂S. Spontaneous, open-circuit deposition processes as well as dissolution of the deposits in sulfide-free solutions have also been investigated. The potential range, scan rate, sulfide concentration, and pH have been varied. The results of the piezoelectric nanogravimetric studies are elucidated by a rather complex scheme involving underpotential deposition of sulfur at approximately −0.85 V vs. sodium calomel electrode, reductive dissolution of the deposited sulfur-containing layer at potentials more negative than approximately −0.9 V, and formation of a sulfur-containing multilayer at potentials more positive than −0.2 V. During the reduction of sulfur deposited on Au, a mass increase due to the formation of polysulfide species in the surface layer, accompanied by incorporation of Na⁺ counterions, can be observed that starts at approximately −0.4 V. This is a reversible process, i.e., during the reoxidation, counterions leave the surface layers. Frequency excursions during the electroreduction and reoxidation processes reveal existence of several competitive dissolution–deposition steps. Spontaneous interaction between Au and HS⁻ species results in a surface mass increase at the open-circuit potential, and it also manifests itself in the substantial decrease of the open-circuit potential after addition of Na₂S to the supporting electrolyte.     

Voltammetric determination of <Emphasis Type="Italic">D</Emphasis>-penicillamine based on its homogeneous electrocatalytic oxidation with potassium iodide at the surface of glassy carbon electrode

The electrooxidation of D-penicillamine (D-PA) has been studied in the presence of potassium iodide in various buffered aqueous solutions (4.00 ≤ pH ≤ 9.00) at the surface of glassy carbon electrode using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. It has been found that under optimum pH (pH 5.00) in cyclic voltammetry, the electrooxidation of D-PA in the presence of potassium iodide as a homogeneous mediator occurred at a potential about 220 mV less positive than that in absence of potassium iodide at the surface of glassy carbon electrode. The homogeneous electrocatalytic oxidation current wave of D-penicillamine was linearly dependent on the D-PA concentration and a linear calibration curve was obtained in the ranges 3.0 × 10⁻⁵−1.5 × 10⁻³ M and 9.0 × 10⁻⁶−1.2 × 10⁻⁴ M of D-PA with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (2σ) were determined as 3.0 × 10⁻⁵ and 3.5 × 10⁻⁶ M with CV and DPV, respectively. This method was also used for voltammetric determination of D-PA in pharmaceutical preparation by standard addition method.