Arthospira sp. intensive cultures for food and biogas purification

Summary The main contaminants (CO₂ and H₂S) in biogas produced by anaerooic digestion can be removed by an intensive mass culture of Arthospira sp.. At the same time productivities of 26–34 g dry mass/m² -d were reached.     

Bioconversion of hydrogen sulfide by free and immobilized cells ofChlorobium thiosulfatophilum

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.     

The effect of temperature and light intensity on hydrogen gas production by different Rhodopseudomonas capsulata strains

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.     

Direct and maternal genetic effects on body weight maturing patterns in mice

Summary Direct and maternal genetic effects were evaluated for maturing patterns of body weight in mice using a crossfostering design. Crossfostering was performed in one group using dams from populations selected for rapid growth rate (M16 and H₆) and their reciprocal F₁. crosses. A second crossfostering group consisted of dams from the respective control populations (ICR and C₂) and their reciprocal F₁. 's. Population differences were partitioned into direct and maternal effects due to genetic origin, correlated selection responses, heterosis and cytoplasmic or sex-linked effects. Degree of maturity was calculated at birth, 12, 21, 31 and 42 days of age by dividing body weight at each age by 63-day weight. Absolute and relative maturing rates were calculated in adjacent age intervals between birth and 63 days. Genetic origin effects (ICR vs. C₂; M16 vs. H₆) were significant for many maturity traits, with average direct being more important than average maternal genetic effects. In general, correlated responses to selection for maturity traits were larger in the M16 population (M16 vs. ICR) than in the H₆ population (H₆ vs. C₂) and correlated responses in average direct effects were larger than average maternal effects. Positive correlated responses in average direct effects were found for relative maturing rates at all ages and for absolute maturing rates from 31 to 63 days. Apparent correlated responses in degree of maturity were negative for M16 and H₆. However, further analysis suggested that the correlated response for degree of maturity in H₆ may be positive at later ages and negative at earlier ages. Direct and maternal heterosis for degree of maturity was positive in the selected and control crosses. Absolute and relative maturing rates showed positive heterosis initially, followed by negative heterosis. Reciprocal differences due to the cytoplasm or sex-linkage were not important for patterns of maturity.Paper No. 5244 the Journal Series of the North Carolina Agricultural Experiment Station, Ealeigh, Animal Research Institute Contribution No. 683 and Agricultural University at Wageningen Contribution No. 654–490–12On leave from the Animal Research Institute, Agriculture Canada at Ottawa, OntarioOn leave from the Department of Animal Husbandry, Agricultural University at Wagenitgen, the Netherlands     

Isolation and characterization of low hydrogen sulphide producing wine yeast

Variants of the wine yeast Saccharomyces cerevisiae var. montrachet no. 522 which retain more and excrete less hydrogen sulphide (H₂S) into the growth medium have been isolated and characterized. Wine produced using these low excretors has been found to contain less H₂S.     

Thermophilic methanogenesis from sugar beet pulp by a defined mixed bacterial culture

Summary Thermophilic degradation of sugar beet pulp was studied in batch cultures at 55°C by different associations of bacteria, includingClostridium thermocellum,Methanobacterium sp. andMethanosarcina MP.C. thermocellum produced acetate, succinate, methanol, ethanol, H₂ and CO₂. The coculture ofC. thermocellum andMethanobacterium sp. produced trace amounts of ethanol and succinate; acetate concentration was about three times higher than in theC. thermocellum monoculture. The association of this coculture withMethanosarcina MP produced 5.5 mmol CH₄/g dry weight sugar beet pulp.     

The effect of the H2 partial pressure on the metabolite pattern ofLactobacillus casei,Escherichia coli andClostridium butyricum

Summary The metabolite pattern of batch cultures ofLactobacillus casei LMG 6400,Clostridium butyricum LMG 1213t1 andEscherichia coli LMG 2093 was effected only for the latter organism when the H₂ partial pressure was below 1 atmosphere: high hydrogen partial pressures increased the formate formation, low pressures gave rise to increased acetate production and higher cell yields.     

Utilization of free and immobilized Desulfovibrio hydrogenase in hydrogen photoproduction : Coupling efficiency of cytochrome C3, ferredoxin and flavodoxin

Summary Hydrogen photoproduction has been achieved by coupling free or immobilized hydrogenases from Desulfovibrio species to illuminated chloroplasts through different electron mediators. Whereas D. gigas flavodoxin or ferredoxin I cannot directly mediate the electron flux from chloroplasts to hydrogenase, the addition of these mediators considerably enhances the H₂ photoproduction of a system including cytochrome C₃. These immobilized hydrogenases exhibit good stability under working conditions and can be re-used.     

Photoproduction of H2 and NADPH2 by polyurethane-immobilized cyanobacteria

Summary Cyanobacterial cells were grown in polyurethane foams (polyester or polyvinyl types). Chlorogloea fritschii, Nostoc muscorum and Mastigocladus laminosus remained immobilized in the foams and were used for continuous photoproduction of H₂ from ascorbate with methyl viologen (MV) and hydrogenase or Pt catalysts, for periods in excess of 9 days. Foam-immobilized N. muscorum continuously photoreduced exogenous NADP for at least 24 h in the presence of Fd-NADP reductase with ascorbate as electron donor.     

A thermo-stable dehalogenase in the extracts fromPseudomonas sp (strain 19S)

Summary A thermo-stable dehalogenase was demonstrated in the crude extracts fromPseudomonas sp (19S). The ability of the enzyme to catalyze the dehalogenation of various halogen-substituted organic acids was investigated and the highest activity was found with monochloroacetate. The enzyme followed Michaelis-Menten kinetics, and the K_m for monochloroacetate was 0.2mM. Maximum activity was found at pH 10.5 and 60°C. The enzyme activity in the cell-free extract was unaffected by EDTA or by Mn, Zn, or Cu ions, but was dramatically reduced by HgCl₂ (70%) and Pb (NO₃)₂ (80%).     

The tri–μ–hydrido–bis[(η5–C5Me5)aluminum(III)] theoretical study, the assets of sandwiched M2H3 (M of 13th group elements) stability

The stability of the tri–μ–hydrido–bis[(η⁵–C₅Me₅)aluminum], Cp*₂Al₂H₃, 1 is studied at B3LYP/6–311+G(d,p), CCSD(T)//B3LYP/6–311+G(d,p) and MP4//B3LYP/6–311+G(d,p) levels. The coordination between Al₂H₃ entity and both C₅(CH₃)₅ groups is ensured by strong electrostatic and orbital interactions. The orbital analysis of the interacting fragments shows that Al₂H₃ acceptor, which keeps its tribridged structure, implies the vacant ( \texta₁￠ ) \left( {{\text{a}}_1^\prime } \right) and five antibonding (a₂^￠￠ a_2^{\prime \prime } , e′ and e″) molecular orbitals to interact with two orbitals mixtures, b₁ and e" of the donors (C₅Me₅). When we take into account the solvent effect, the computation shows that 1 seems to be stable in condensed phase with a tribridged bond between the Al atoms [Cp*Al(μ-H)₃AlCp*], whereas in the gas phase, the monobridged Cp*AlH(μ-H)AlHCp* 4 is slightly favored (4 kcal mol⁻¹). We propose that 1 could be prepared thanks to Cp*Al (2) and Cp*AlH₂ (3) reaction in acidic medium. The experimental treatment of this type of metallocenes would contribute to the development of the organometallic chemistry of 13th group elements.      

Adenosine 5'-O(3-thiotriphosphate) in the control of phosphorylase activity

Rabbit muscle phosphorylase b (EC 2.4.1.1) is converted to a thio-analog of phosphorylase a by phosphorylase kinase, Mg²⁺ and adenosine 5′-O(3-thiotriphosphate)(ATPγS). Conversion proceeds at one-fifth the rate obtained with ATP though the extent of reaction and final level of activation of the enzyme are the same. However, the thiophosphorylase a produced is resistant to phosphorylase phosphatase and, therefore, behaves as a competitive inhibitor with a K_I of 3 μM, similar to the K_M obtained with normal phosphorylase a. ATPγS can also be utilized by protein kinase in the activation of phosphorylase kinase at a rate similar to that obtained with ATP. It is hydrolyzed at 5 to 10 times the normal rate by the sarcoplasmic reticulum ATPase. When added to a muscle glycogen-particulate complex in the presence of Ca²⁺ and Mg²⁺, ATPγS triggers an activation of phosphorylase with simultaneous inhibition of phosphorylase phosphatase as previously observed with ATP.     

Reduced Glutathione Mediates Resistance to H2S Toxicity in Oral Streptococci

Periodontal disease is associated with changes in the composition of the oral microflora, where health-associated oral streptococci decrease while Gram-negative anaerobes predominate in disease. A key feature of periodontal disease-associated anaerobes is their ability to produce hydrogen sulfide (H₂S) abundantly as a by-product of anaerobic metabolism. So far, H₂S has been reported to be either cytoprotective or cytotoxic by modulating bacterial antioxidant defense systems. Although oral anaerobes produce large amounts of H₂S, the potential effects of H₂S on oral streptococci are currently unknown. The aim of this study was to determine the effects of H₂S on the survival and biofilm formation of oral streptococci. The growth and biofilm formation of Streptococcus mitis and Streptococcus oralis were inhibited by H₂S. However, H₂S did not significantly affect the growth of Streptococcus gordonii or Streptococcus sanguinis. The differential susceptibility of oral streptococci to H₂S was attributed to differences in the intracellular concentrations of reduced glutathione (GSH). In the absence of GSH, H₂S elicited its toxicity through an iron-dependent mechanism. Collectively, our results showed that H₂S exerts antimicrobial effects on certain oral streptococci, potentially contributing to the decrease in health-associated plaque microflora.     

Enhanced Synthesis and Diminished Degradation of Hydrogen Sulfide in Experimental Colitis: A Site-Specific,Pro-Resolution Mechanism

Hydrogen sulfide (H₂S) is produced throughout the gastrointestinal tract, and it contributes to maintenance of mucosal integrity, resolution of inflammation, and repair of damaged tissue. H₂S synthesis is elevated in inflamed and damaged colonic tissue, but the enzymatic sources of that synthesis are not completely understood. In the present study, the contributions of three enzymatic pathways to colonic H₂S synthesis were determined, with tissues taken from healthy rats and rats with colitis. The ability of the colonic tissue to inactivate H₂S was also determined. Colonic tissue from rats with hapten-induced colitis produced significantly more H₂S than tissue from healthy controls. The largest source of the H₂S synthesis was the pathway involving cysteine amino transferase and 3-mercaptopyruvate sulfurtransferase (an α-ketoglutarate-dependent pathway). Elevated H₂S synthesis occurred specifically at sites of mucosal ulceration, and was not related to the extent of granulocyte infiltration into the tissue. Inactivation of H₂S by colonic tissue occurred rapidly, and was significantly reduced at sites of mucosal ulceration. This correlated with a marked decrease in the expression of sulfide quinone reductase in these regions. Together, the increased production and decreased inactivation of H₂S at sites of mucosal ulceration would result in higher H₂S levels at these sites, which promotes of resolution of inflammation and repair of damaged tissue.     

Synthesis of Certain 4-Substituted-1-β-D-Ribofuranosyl-3-Hydroxypyrazoles Structurally Related to the Antibiotic Pyrazofurin

Abstract

Several 4-substituted-1-β-D-ribofuranosyl-3-hydroxypyrazoles were prepared as structural analogs of pyrazofurin. Glycosylation of the TMS derivative of ethyl 3(5)-hydroxypyrazole-4-carboxylate (3) with 1-0-acetyl-2,3,5-tri-0-benzoyl-D-ribofuranose in the presence of TMS-triflate gave predominantly ethyl 3-hydroxy-1-(2,3,5-tri-0-benzoyl-β-D-ribofuranosyl)pyrazole-4-carboxylate (4a), which on subsequent ammonolysis furnished 3-hydroxy-1-β-D-ribofuranosylpyrazole-4-carboxamide (5). Benzylation of 4a with benzyl bromide and further ammonolysis gave 3-benzyloxy-1-β-D-ribofuranosylpyrazole-4-carboxamide (8a). Catalytic (Pd/C) hydrogenation of 8a afforded yet another high yield route to 5. Saponification of the ester function of ethyl 3-benzyloxy-1-β-D-ribofuranosylpyrazole-4-carboxylate (7b) gave the corresponding 4-carboxylic acid (6a). Phosphorylation of 8a and subsequent debenzylation of the intermediate 11a gave 3-hydroxy-1-β-D-ribofuranosylpyrazole-4-carboxamide 5′-phosphate (11b). Dehydration of 3-benzyloxy-1-(2,3,5-tri-0-acetyl-β-D-ribofuranosyl)pyrazole-4-carboxamide (8b) with POCl₃ provided the corresponding 4-carbonitrile derivative (10a), which on debenzylation with Cl₃SiI gave 3-hydroxy-1-(2,3,5-tri-0-acetyl-β-D-ribofuranosyl)pyrazole-4-carbonitrile (13). Reaction of 13 with H₂S/pyridine and subsequent deacetylation gave 3-hydroxy-1-β-D-ribofuranosylpyrazole-4-thiocarboxamide (12b). Similarly, treatment of 13 with NH₂OH afforded 3-hydroxy-1-β-D-ribofuranosylpyrazole-4-carboxamidoxime (14a), which on catalytic (Pd/C) hydrogenation gave the corresponding 4-carboxamidine derivative (14b). The structural assignment of these pyrazole ribonucleosides was made by single-crystal X-ray analysis of 6a. None of these compounds exhibited any significant antitumor or antiviral activity in cell culture.     

Studies on the mechanism of formation of the 5S,12S-dihydroxy-6,8,10,14(E,Z,E,Z)-icosatetraenoic acid in leukocytes

Incubation of peripheral blood leukocytes with arachidonic acid (and ionophore A23187) led to the formation of leukotriene B₄, Δ⁶-trans-leukotriene B₄, Δ⁶-trans-12-epi-leukotriene B₄, 5-hydroxy-icosatetraenoic acid, 12-hydroxy-icosatetraenoic acid and of 5S,12S-dihydroxy-6,8,10,14-(E,Z,E,Z)-icosatetraenoic acid (5S,12S-DiHETE). Incubation of leukocytes with leukotriene A₄ resulted in the formation of leukotriene B₄ and of its two Δ⁶-trans-isomers but not of the 5S,12S-DiHETE. ¹⁸O₂ labeling experiments have shown that the hydroxyl groups at C5 and C12 in the 5S,12S-DiHETE are derived from molecular oxygen. The tetraacetylenic analog of arachidonic acid was found to be a potent inhibitor of the formation of the 5S,12S-DiHETE whereas it potentiated the synthesis of the 5-hydroxy acid and of leukotriene B₄. Addition of the 12-hydroxy-icosatetraenoic acid to leukocytes, or of the 5-hydroxy-icosatetraenoic acid to a suspension of platelets caused the formation of the 5S,12S-DiHETE. It is concluded that the 5S,12S-DiHETE is not derived from leukotriene A₄ but is a product of the successive reactions of arachidonic acid with two lipoxygenases of different positional specificities.     

THE NMR CONFORMATION STUDY OF THE COMPLEXES OF DEOXYCYTIDINE KINASE (dCK) AND 2′-DEOXYCYTIDINE/2′-DEOXYADENOSINE

The structures of the bound ¹³C/²H double-labelled 2′(R/S), 5′(R/S)-²H₂-1′,2′,3′,4′,5′-¹³C₅-2′-deoxyadenosine and the corresponding 2′-deoxycytidine moieties in the complexes with human deoxycytidine kinase (dCK) have been characterized for the first time by the solution NMR spectroscopy, using Transferred Dipole-Dipole Cross-correlated Relaxation and Transferred nOe experiments. It has been shown that the ligand adopts a South-type sugar conformation when bound to dCK.     

CH4 production from H2 and CO2 byMethanobacterium thermoautotrophicum cells fixed on hollow fibers

Summary Methane was produced from H₂ and CO₂ byMethanobacterium thermoautotrophicum cells fixed on the surface of hollow fibers. The mineral solution permeated through the inside of fibers was consumed by the cells, while the gaseous substrate flowing outside the fibers was directly metabolized to methane. Methane production was proportional to hollow fiber length i.e., contact area between cell layer and gas phase. In repeated batch cultures, the production rates of methane and cell mass were 33.1 L/L reactor/day and 1.75 g cells/L reactor/day, respectively with 90% conversion rate.     

Production of 2,3-butanediol from HF-hydrolyzed aspen wood

Hydrolyzates from hydrogen fluoride (HF) treated aspenwood were predominantly composed of oligosaccharides which are not readily utilized by Klebsiella pneumoniae. Attempts at further hydrolyzing these oligosaccharides using a variety of glycolytic and xylanolytic enzymes (i.e., amylases, cellulases, and xylanases) were only partially successful. When a post-hydrolysis step was carried out using 3% H₂SO₄, significant amounts of the component monosaccharides were detected. Sugars released by acid or enzymatic hydrolysis of the HF treated aspenwood were utilized by K. pneumoniae for the production of butanediol and ethanol.     

Purification and structure of the host-specific toxin from Helminthosporium carbonum race 1

The host-specific toxin from Helminthosporiumcarbonum race 1 was purified from culture filtrates by solvent extraction, gel filtration, and high pressure liquid chromatography. High resolution mass spectrometry of the purified toxin gave a MW of 436.2318 and an elemental composition C₂₁H₃₂N₄O₆. Amino acid analysis and proton and¹³C-NMR indicated a peptide containing four amino acids. Their sequence was determined by gas chromatography mass spectrometry. Finally, digestion of the amino acids with D- and L-amino acid oxidases gave the complete structure cyclo[(L-2-amino-9, 10-epoxy-8-oxodecanoyl)-D-prolyl-L-alanyl-L-alanyl].