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1.
Summary Six strains of Rhodopseudomonas capsulata were tested for their ability for anaerobic light-dependent hydrogen gas production from acetate in different incubation temperatures and light intensities.Certain strains show a higher efficiency of acetate conversion to H2 at higher temperatures and higher light intensities, others on the other hand are insensitive or even show the opposite effect.  相似文献   

2.
Dissolved hydrogen in an anaerobic digestion process was continuously measured by a voltammetric membrane electrode which consisted of a Pt-Pt black and Ag-AgCl covered FEP membrane with 0.1 M KCl and 0.1 M HCl. This sensor showed high reliability and sensitivity (i.e., detection limit: 50 nM) in distilled water. The sensor was not affected by several compounds in the anaerobic digestion media (e.g., inorganic salts, acetate, and propionate) except for sulfide. The indication in a sample containing 1.56 mM sulfide corresponded to that of 0.26 μM dissolved hydrogen. The sensor was also applied to measure the dissolved hydrogen in a laboratory-scale anaerobic reactor, and the dissolved hydrogen was continuously monitored for 565-h. The sensor was calibrated every 120-h, and the output signal was very stable during this period. The dissolved hydrogen concentration ranged from 0.5 to 3 μM, and H2 partial pressure from 2 to 7 Pa in the gas phase. A good correlation (r = 0.85) between theoretical values calculated with H2 partial pressure and the output signals was recognized. The actual dissolved hydrogen concentration was about 60-fold higher than the theoretical values calculated with H2 partial pressure.  相似文献   

3.
Summary Nitrogen fixing cultures of the cyanobacteriumNostoc muscorum lacked hydrogen evolution but cultures infected with cyanophage N-1 showed significant hydrogen evolution and inactive nitrogenase, suggesting that nitrogenase activity is not responsible for the observed oxygen-resistant photoproduction of hydrogen. Significant oxygen-resistant hydrogen production by nitrate or ammonium assimilating cultures deficient in both nitrogenase and uptake hydrogenase activity supports this conclusion. These findings suggest a role of uptake hydrogenase in blocking the production of hydrogen during aerobic photosynthetic conditions.  相似文献   

4.
Summary The transformation of hydrogen sulfide into elementary sulfur and sulfate was investigated in a photo-bioreactor using autotropic bacteriaChlorobium thiosulfatophilum. The accumulations of sulfur and sulfate in the reactor were found to be dependent on the light energy and the feed rate of H2S. The optimum operation lines were established to limit sulfide or sulfate. Immobilization of the whole cells in strontium-alginate matrix enhanced the conversion more than with the free cells.  相似文献   

5.
Summary Hydrogenases from Clostridium pasteurianum and Desulfovibrio desulfuricans were immobilized on solid supports with retention of 50% activity. The immobilized enzymes were more stable than the free enzymes and were active in the biophotolytic hydrogen production from water.  相似文献   

6.
Rupela  O. P.  Tauro  P. 《Biotechnology letters》1985,7(4):279-282
Summary The ability to retain hydrogen sulfide (H2S) inSaccharomyces cerevisiae is under nuclear gene control. Mutants with the ability to retain greater amounts of H2S than the parent have been isolated and characterised.  相似文献   

7.
Summary The fermentation of glucose byClostridium thermosaccharolyticum strains IMG 2811T, 6544 and 6564 was studied in batch culture in a complex medium at different temperatures in defined and free-floating pH conditions. All the strains ferment 5 g glucose.l–1 completely. The yield of the fermentation products turned out to be independent of the incubation temperature for strain IMG 2811T. Strain IMG 6544 produced at 60°C significantly more ethanol and less acetic acid, butyric acid, hydrogen gas and biomass than at lower temperatures. With strain IMG 6564, the opposite effect occurred: ethanol appeared to be the main fermentation product at 45°C; at 60°C less ethanol and more acetic acid, butyric acid and hydrogen gas was formed.Experiments, carried out with strain IMG 6564, at defined pH conditions (between 5.5 and 7) and different temperatures (45, 55 and 60°C) revealed no effect of the incubation temperature, but an important effect of the pH on the product formation. At pH 7, ethanol was the main fermentation product while minor amounts of hydrogen gas, acetic and butyric acid were produced. Lowering the pH gradually to 5.5 resulted in a decrease of ethanol and an increase of biomass, hydrogen gas, acetic, butyric and lactic acids. At pH higher than 7 no growth occurred. Similar conclusions could be drawn for strains IMG 2811T and 6544.  相似文献   

8.
Photoproduction of hydrogen gas by the green alga Chlorella pyrenoidosa was studied in a large scale culture of 2.1. Hydrogen was produced by adding sodium hydrosulfite directly to an algal suspension after anaerobiosis in darkness for activation of hydrogenase. The hydrogen production rate showed a characteristic course of an initial burst of gas then steady production, and this course appeared most clearly at cell concentrations around 0.6–0.7 kg/m3. In the final third phase, the hydrogen production rate gradually decreased until evolution ceased. The steady hydrogen evolution was inhibited 75% by a herbicide, DCMU, which blocks electron flow through photosystem II, indicating that the electron donor for hydrogen production was mainly water. The average light intensity within the culture vessel was measured with a diffusing sphere photoprobe. The rate of hydrogen evolution increased hyperbolically with the average light intensity. The duration of hydrogen photoproduction was shorter at higher light intensity due to the inhibition of hydrogenase by concomitantly released oxygen. The duration was shorter also at higher concentrations of algal suspension. It was foudd that the optimum concentration of algae, about 0.7 kg/m3 in this system, must be selected to maximize the yield of hydrogen.  相似文献   

9.
10.
The production of deuterated methane by Methanobacterium thermoautotrophicum in H2O-D2O mixtures was examined by high-resolution mass spectrometry. The hydrogen in the methane arose solely from water and not from hydrogen gas. Hydrogen gas served only as an electron source in methanogenesis. A whole-cell product isotope discrimination of 1.5 favoring hydrogen over deuterium was observed in methane production in 81 atom% deuterated water. The distribution of deuterated methane species is described by a simple model of the overall reaction.  相似文献   

11.
Summary On-line estimation of ethanol concentration during a fermentation was carried out with a semiconductor gas sensor system using a semipermeable membrane to separate a gas stream from the fermentor broth. The system has the advantages of low-cost, in-situ steam sterilization and a relatively fast response time (1 min.). Good agreement was found between on-line and off-line measurements with fermentation of 25% glucose media using S.uvarum and Z.mobilis. However, significant deviations occurred with the fermentation of sugar-cane juice, grape-juice and molasses.  相似文献   

12.
We report experimental study on an indium?Ctin oxide (ITO)-coated surface plasmon resonance-based fiber-optic hydrogen gas sensor operating at room temperature. The sensor works on intensity modulation interrogation. Indium?Ctin oxide (In2O3?+?SnO2) films were grown on unclad core of the fiber by thermal evaporation technique. The surface plasmon resonance (SPR) spectra for 100?% nitrogen gas as well as for a mixture of 4?% hydrogen gas and 96?% nitrogen gas were obtained. In the case of mixture of hydrogen and nitrogen gases, a sharp dip in the SPR spectrum was observed implying that the hydrogen gas changes the dielectric properties of ITO. The performance of the sensor has been studied for different percentages of tin oxide in indium oxide and for different thicknesses of ITO film. Both the parameters have been optimized for the best performance of the sensor.  相似文献   

13.
Summary A gas phase explosion in a storage tower with semichemical pulp at a paper mill has possibly been caused by combustion of a mixture of hydrogen and air. The hydrogen was formed by microorganisms in the pulp. Ignition may be due to electric sparks in connection with an electric field in the mist above the pulp.  相似文献   

14.
15.
Liu Y  Tang F  Kang CJ  Cao X 《Luminescence》2012,27(4):274-278
Detection of hydrogen sulphide (H2S) was conducted based on cataluminescence (CTL) sensors, using alkaline‐earth metal carbonates as catalysts. Optimal working conditions, analytical characteristics and the response properties of the sensor were investigated. CTL intensity examination showed that sensors fabricated with CaCO3, SrCO3 or BaCO3 could be used to detect H2S gas sensitively. The optimal sensing temperature was about 320 °C. Under the sensing conditions with temperature at ca. 320 °C and gas flow rate in the range 180–200 mL/min, the linear range of CTL intensity vs H2S concentration was 25–500 ppm, with a detection limit of 2 ppm. The response and recovery times of the sensor were within 5 and 25 min, respectively. Also, the sensor had the property of high selectivity to H2S with very weak or no obvious response to 14 other gases, such as NO2, NH3, hydrocarbons and alcohol. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

16.
Cellulose was mixed with the hydroxides of lithium and nickel and the mixture was milled, followed by heating to produce hydrogen. Several analytical methods of X-ray diffraction (XRD), thermogravimetry/mass spectrometry (TG/MS) and gas chromatography (GC) were used to characterize the samples. Hydrogen was emitted when heating the milled sample around 400 °C together with low concentrations of methane, carbon monoxide and carbon dioxide. It is understood that an interaction occurs between cellulose and lithium hydroxide to convert the carbon of cellulose into lithium carbonate and to emit hydrogen correspondingly. It is also found that nickel catalyst is required to facilitate the interaction and the behaviours of three different nickel compounds were compared. When high yield of hydrogen emission is available, the prepared samples can also serve the purpose of hydrogen storage.  相似文献   

17.
Summary The purified soluble NAD-dependent hydrogenase from Alcaligenes eutrophus was immobilized to porous glass beads according to the glutaraldehyde method retaining about 80% of its original activity. Entrapment of the purified hydrogenase in photo-crosslinkable prepolymers led to apparent activity yields of 10–80% dependent on the thickness of the gel film. The storage stability of entrapped hydrogenase (t/2 = 4 d) was considerably lower than that of glass-bound hydrogenase (t/2 = 150 d). During continuous production of NADH (turnover conditions), the half-life of entrapped hydrogenase was not longer than 10 h. Whole cells of A. eutrophus entrapped in a polyurethane matrix were used to produce NADH with hydrogen gas as electron donor. After 18 runs for 4h each and storage periods overnight the residual activity was still about 50%.  相似文献   

18.
The effect of -malic acid and sodium glutamate, which serve as the carbon and nitrogen source, respectively, on hydrogen production by Rhodobacter sphaeroides O.U.001 has been investigated in a batch water jacketed glass column photobioreactor (PBR), which has an inner volume of 400 ml. The PBR was operated at different carbon to nitrogen ratios at 32°C with a tungsten lamp at a light intensity of 200 W m−2. Carbon to nitrogen ratio was found to be an important parameter for bio-hydrogen production. Moreover, hydrogen gas production was dependent on certain threshold concentrations of sodium glutamate. -malic acid consumption was found to be first order with respect to -malic acid concentration, whereas sodium glutamate consumption was found to be second order with respect to glutamate concentration. It was concluded that there is a close relationship between the hydrogen production rate and substrate consumption rates. A kinetic model is developed, which relates hydrogen gas production per amount of biomass, -malic acid, and sodium glutamate concentrations.  相似文献   

19.
Scenedesmus obliquus and Chlorella vulgaris cells had active hydrogenase after dark anaerobic adaptation. Illumination of these algae with visible light led to an initial production of small quantities of hydrogen gas which soon ceased owing to production of oxygen by photolysis of water. The presence of oxygen-absorbing systems in a separate chamber, not in contact with the algae, gave only a slight stimulation of hydrogen production. Addition of sodium dithionite directly to the algae led to an extensive light-dependent production of hydrogen. This stimulation was due to oxygen removal by dithionite and not to its serving as an electron donor. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea, an inhibitor of photosystem II, abolished all hydrogen photoproduction. Hydrogen evolution was not accompanied by CO2 production and little difference was noted between autotrophically and heterotrophically grown cells. Hydrogen was not produced in a photosystem II mutant of Scenedesmus even in the presence of dithionite, establishing that water was the source of hydrogen via photosystems II and I. Hydrogen production was stimulated by the presence of glucose and glucose oxidase as an oxygen-absorbing system. Oxygen inhibited hydrogen photoproduction, even if oxygen was undetectable in the gas phase, if the algal solution did not contain an oxygen absorber. It was demonstrated that under these conditions hydrogenase was still active and the inability to produce hydrogen was probably due to oxidation of the coupling electron carrier.  相似文献   

20.
A coupled reactor system, consisting of one aerated stirred reactor and one anaerobic plug flow reactor was constructed. Circulation of microbial cells in this system, is chosen to represent the insufficient mixing conditions, present in a large scale vessel. Hereby it is shown, that oscillating oxygen concentrations, give effects on E.coli metabolism. The hydrogen production, resulting from mixed acid fermentation of anaerobically grown cells, is used to indicate the metabolic changes. These changes are measured as hydrogen concentration in the gas outlet of the aerated fermenter, with a Pd-MOS sensor. The dependency of the hydrogen evolution on the anaerobic residence time is shown, and the relevance of this model system for studies on the bioreactor performance, are discussed.  相似文献   

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