Spiral tubular bioreactors for hydrogen production by photosynthetic microorganisms

Spiral tubular bioreactors were constructed out of transparent PVC tubing for H2 production applications. Both a cyanobacterialAnabaena variabilis mutant that lacks uptake hydrogenase activity and the photosynthetic bacteriumRhodobacter sp. CBS were tested in the bioreactors. Continuous H₂ photoproduction at an average rate of 19 mL min^-2.h^-1 was observed using theA. variabilis mutant under an air atmosphere (without argon sparging or application of a partial vacuum). The cyanobacterial photobioreactor was run continuously for over one month with an average efficiency of light energy conversion to H₂ of 1.4%. Another H₂-producing approach employed a unique type of activity found in a strain of photosynthetic bacteria that shifts CO (and H₂O) into H₂ (and CO₂) in darkness. Continuous dark H₂ production byRhodobacter sp. CBS from CO (in anticipation of using synthesis gas as the future substrate) at rates up to 140 mL . g cdw^-1 . h^-1 was observed in a bubble-train bioreactor for more than 10 d.

     

Synthesis of a palladium(II) complex of a <Emphasis Type="Italic">N</Emphasis>-heterocylic carbene via transmetalation: crystal structure and antibacterial studies

An Ag(I)-N-heterocylic carbene (NHC) complex, [Ag(L)₂]PF₆ (L = 1-(2′-methylbenzyl)-3-(2″-propyl)benzimidazolium), was used as a transfer agent for the synthesis of a Pd(II)–NHC complex, formulated as [PdCl(L)₂(MeCN)]PF₆ (Pd1). The complex Pd1 was characterized by ¹H and ¹³C NMR, FTIR spectroscopy and elemental analysis. Single crystal X-ray diffraction analysis reveals that the Pd(II) atom has a square planar geometry. This complex was screened for its antibacterial potential against the Gram-negative bacteria Escherichia coli (ATCC 25922) and the Gram-positive bacteria Staphylococcus aureus (ATCC 12600). These results are compared with those obtained for a standard antibiotic, ampicillin, and also the corresponding Ag(I)–NHC complex.     

Electrochemical determination of hydrogen peroxide using o -dianisidine as substrate and hemoglobin as catalyst

A new electrochemical method for the determination of microamounts of hydrogen peroxide utilizing o-dianisidine (ODA) as substrate and hemoglobin (Hb) as catalyst is described in this paper. Hb can be used as mimetic peroxidase and it can catalyse the reduction of hydrogen peroxide with the subsequent oxidation of ODA. The oxidative reaction product is an azo compound, which is an electroactive substance and has a sensitive second-order derivative polarographic reductive peak at the potential of -0.58 V (vs. SCE) in pH 80 Britton-Robinson (B-R) buffer solution. The conditions of Hb-catalytic reaction and polarographic detection of the reaction product were carefully studied. By using this polarographic peak and under optimal conditions, the calibration curve for the H₂O₂ was constructed in the linear range of 2.0 x 10^-7 ∼ 10 x 10^-4 mol/l with the detection limit of 5.0 x 10^-8 mol/l. This method can also be used to the determination of Hb content in the range of 20 x 10^-9 ∼ 30 x 10^-7 mol/l with a detection limit of 10 x 10^-9 mol/l. The proposed method was further applied to the determination of the content of H₂O₂ in fresh rainwater with satisfactory results. The catalytic reaction mechanism and the electrode reductive process of the reaction product were carefully studied.     

Cathodic adsorption voltammetry of palladium(II)

The electrochemical behavior of palladium(II) was studied by differential pulse, linear sweep, and alternating-current square-wave voltammetry in HC1, HNO₃, H₂SO₄, and HC1O₄ solutions in the presence of dimethylglyoxime. A peak with a height linearly depending on the concentration of palladium(II) was observed in voltammograms. Typical relationships between the height and potential of a peak and pH, dimethylglyoxime concentration, the potential and time of adsorption accumulation suggested that the observed peak was due to the hydrogen liberation catalyzed by palladium(II) dimethylglyoximate adsorbed on the electrode surface. The detection limits for palladium(II) accumulated for 120 s at -0.2 V were 2 x 10^-8, 5 x 10^-9, and 8 x 10^-10 M for differential pulse, linear sweep, and alternating-current square-wave voltammetry, respectively.     

Predissociation lifetime of the 1σ g 2 2σ g diabatic state of He 2 + : a one-channel approach

Summary This work is concerned with the application of a one-channel model to obtaining predissociation lifetimes and transition rates in a system of crossing diabatic states. The calculation focuses on the first shape resonance of the 1 _g ² 2 _g diabatic state of He ₂ ⁺ , which is relatively stable with respect to tunneling. This resonance predissociates as a result of the 1 _g ² 2 _g state being crossed by the 1 _g 1 _u ² dissociative diabatic state near the resonance level. We have estimated its predissociation lifetime to be of the order of 10^–11 s.     

Glutamate production from CO2 by Marine CyanobacteriumSynechococcus sp.

A photobioreactor was constructed in the form of a Perspex column 900 mm tall with an internal diameter of 70 mm. The reactor volume was 1.8 L and the light source consisted of a metal-halide lamp to reproduce sunlight. Light was distributed through the culture using a new type of optical fiber that diffuses light out through its surface, perpendicular to the fiber axis. A cluster of 661 light-diffusing optical fibers (LDOFs) pass from the light source through the reactor column (60-cm culture depth) and are connected to a mirror at the top of the reactor. This biosolar reactor has been used for the production of glutamate from CO₂ by the marine cyanobacterium Synechococcus sp. NKBG040607. We present here details of the construction of the biosolar reactor and characterization of its properties. The effect of light intensity on glutamate production was measured. Carbon dioxide-to-glutamate conversion ratios were determined at different cell densities: the maximum conversion ratio (28%) was achieved at a cell density of 3x10⁸ cells/mL. A comparison of glutamate production using the LDOF biosolar reactor described here with production by batch culture using free or immobilized cells showed that use of an optical-fiber biosolar reactor increased glutamate-production efficiency 6.75-fold. We conclude that as a result of its high surface-to-volume ratio (692/m) increased photoproduction of useful compounds may be achieved. Such a system is generally applicable to all aspects of photobiotechnology.     

Cultivating <Emphasis Type="BoldItalic">Chlorella</Emphasis> sp. in a Pilot-Scale Photobioreactor Using Centrate Wastewater for Microalgae Biomass Production and Wastewater Nutrient Removal

This study is concerned with a novel mass microalgae production system which, for the first time, uses “centrate”, a concentrated wastewater stream, to produce microalgal biomass for energy production. Centrate contains a high level of nutrients that support algal growth. The objective of this study was to investigate the growth characteristics of a locally isolated microalgae strain Chlorella sp. in centrate and its ability to remove nutrients from centrate. A pilot-scale photobioreactor (PBR) was constructed at a local wastewater treatment plant. The system was tested under different harvesting rates and exogenous CO₂ levels with the local strain of Chlorella sp. Under low light conditions (25 μmol·m^-2s^-1) the system can produce 34.6 and 17.7 g·m^-2day^-1 biomass in terms of total suspended solids and volatile suspended solids, respectively. At a one fourth harvesting rate, reduction of chemical oxygen demand, total Kjeldahl nitrogen, and soluble total phosphorus were 70%, 61%, and 61%, respectively. The addition of CO₂ to the system did not exhibit a positive effect on biomass productivity or nutrient removal in centrate which is an organic carbon rich medium. The unique PBR system is highly scalable and provides a great opportunity for biomass production coupled with wastewater treatment.     

Development of an electrochemical sensor for potassium ions based on KSr2Nb5O15 modified electrode

In the work described by this paper, we studied the development of a selective potassium ion sensor constituted of a carbon paste electrode modified (CPEM) with a novel KSr₂Nb₂O₁₅. The material KSr₂Nb₂O₁₅ is an oxide with the tetragonal tungsten bronze structure (TTB) type are in forefront both in the area of research as well as in industrial applications. The sensor response to potassium ions was linear in the concentration range 1.26 x 10^-5 at 1.62 x 10^-3 mol L^-1 (E (mV) = 32.7 + 51.1 log [K⁺]). The sensor based KSr₂Nb₂O₁₅, of the TTB-type presented very good potentiometric response, with a slope of 51.1 mV/dec (at 25 °C) and detection limit for the potassium ions of 7.27 x 10^-5 mol.L^-1.     

The oxidized complex of nickel with 4-carboxy-1,2-cyclohexanedionedioxime in alkaline media

The reaction of oxygen with a nickel(II) complex of 4-carboxy-1,2-cyclohexanedionedioxime in alkaline media was studied spectrophotometrically, polarographically, and by spectrophotometric titrations with tin(II) chloride. Magnetic susceptibility measurements were also performed. The rate of formation of the oxidized complex was found to be first order at 25° and 50°. The average values obtained for the rate constant k'₁ are (2.71 ± 0.23) x 10^-2 h^-1 (25°), spectrophotometrically; (5.99 ± 0.83) x 10^-2 h^-1 (50°), polarographically; (4.98 ± 0.90) x 10^-2 h^-1 (50°), titrimetrically; (2.87 ± 0.29) x 10^-2 h^-1 (50°), curve fitting. The value obtained for the rate constant K'₂ is (1.59 ± 0.16) x 10^-2 h^-1 (50°), curve fitting, The effect of reducing agents on the formation of the oxidized complex was studied. It was found that tin(II) chloride, hydrazine sulfate, and hydroxylammonium chloride prevented the formation of the oxidized complex. A reaction mechanism for the formation and decomposition of the oxidized complex is proposed.     

Electrocatalytical Oxidation and Determination of Dopamine at Redox Polymer/Nafion Modified Electrodes

ABSTRACT

The modified glassy carbon electrodes prepared by simultaneously covering with [Os(bpy)₂(PVP)₁₀Cl]⁺ redox polymer and Nafion film exhibited excellent electrocatalytic activity for the oxidation of dopamine (DA). Dual linear regions between 1.0x10^?8-1.8x10^?5 M and 1.8x10^?5-4.0x10^?4 M with correlation coefficients of 0.998 and 0.995, respectively, were obtained for log-log plots of catalytic current versus DA concentration. The detection limit for DA determination was ca. 5 nM with 3σ. The dual-film modified electrodes eliminated efficiently the interference from AA presence in a 1000-fold concentration ratio and showed excellent reproducibility for the determination of DA. The modified electrodes have been used to determine DA concentration with both cyclic voltammetric and chronoamperometric techniques. Electrocatalytic kinetics have been studied using a rotating disk electrode. Both the addition of Nafion film and an increase in DA concentration resulted in a decrease in the electrocatalytic rate constant. An apparent Michaelis-Menten constant of 1.3 mM and maximum catalytic current of 88μA were evaluated from the chronoamperometric measurements.     

Coordination compounds and microorganisms,Part 12. Rhodium compounds of S-nicotine and their bacterial activity

Summary The activities of the nicotine complexes of rhodium(III)-[RhCl₃(nicH⁺)₃](PF₆)₃ andtrans-[RhCl₂(nic)₄](PF₆) (nicH⁺=monoprotonated S-nicotine, nic=unprotonated S-nicotine)—were studied onEscherichia coli B growing in a minimal glucose medium in both lag- and log-phases.[RhCl₃(nicH⁺)₃](PF₆)₃ at 50 ppm caused bacteriostasis, and at 100 ppm or more was bactericidal, whereastrans-[RhCl₂(nic)₄](PF₆) at 50 ppm or more was bactericidal in the lag-phase. However [RhCl₃(nicH⁺)₃](PF₆)₃ delayed cell division ofEscherichia coli B just entering the log phase by two generation times, whereby the bacteria transformed from the normal unicellular shape to filamentous forms. Cytotoxicities are reported.     

The PVT properties of concentrated aqueous electrolytes. IV. Changes in the compressibilities of mixing the major sea salts at 25°C

The speed of sound of mixtures of the six possible combinations of the major sea salt ions (Na⁺, Mg²⁺, Cl^–, and SO ₄ ^2– ) have been determined at I=3.0 and at 25°C. The results have been used to determine the changes in the adiabatic compressibility of mixing K_m the major sea salts. The values of K_m have been fit to the equation K_m=y₂y₃I²[k₀+k₁(1-2y₃)] where y_i is the ionic strength fraction of solute i, k₀ and k₁ are parameters related to the interactions of like-charged ions. The Young cross-square rule is obeyed to within ±0.04×10^–6 cm³-kg^–1-bar^–1. A linear correlation was found between the compressibility k₀ and volume v₀ interaction parameters (10⁴k₀=–0.24+3.999 v₀, s=0.15) in agreement with out earlier findings. Estimates of the sound speeds for the cross square mixtures (NaCl+MgSO₄ and MgCl₂+Na₂SO₄) were made using the equations of Reilly and Wood. The estimated sound speeds were found to agree on the average with the measured values to ±0.36 m-sec^–1.     

CRYSTALLIZATION SEGREGATION DSC STUDIES OF PP/PE COPOLYMERS

 The structural analysis of two PP/PE copolymer samples, I and 2, was conducted by using ¹³C-NMR, GPC and crystallization segregation DSC (CSDSC) techniques. A pure polypropylene sample was also used for comparison. It was found that the two copolymer samples are very close in composition (the ethylene mol content is 4.3% and 4.5%,respectively), stereoregularity (96% and 97%) and molecular weight (M_w, = 7.0 x 10⁴ and 7.3x10⁴; M_w/M_n = 5.0 and 6.1,respectively). While the CSDSC thermograms of the two samples are quite different from each other. Sample 1 shows a higher average melting temperature and a broader distribution of its thermogram. These phenomena were explained as an indication of a less uniform distribution of ethylene units along the PP chains for sample 1. It was noted that CSDSC is a very sensitive and convenient technique for structural studies of copolymers.     

Chemistry of a new antibiotic: lactivicin

A novel antibiotic, lactivicin (LTV), was isolated from the culture filtrates of two bacterial strains by various types of chromatography. LTV exists in aqueous solution as an equilibrium mixture of two epimers in a ratio of about 1:1. The chemical structure of LTV (C₁₀H₁₂N₂O₇) was determined to be 2-(4S-acetylamino-3-oxo-2-isoxazolidinyl)-5-oxo-tetrahydrofuran-2-carboxylic acid. The absolute configuration at the C-6 position was elucidated from the CD spectral data and X-ray crystallographic analysis of 4-amino-lactivinic acid obtained by the iminoether method. This compound is useful as a starting material for chemical modification. LTV showed antibacterial activity against Gram-positive and negative bacteria, susceptibility to β-lactamases, and affinity for penicillin-binding proteins. We therefore concluded that LTV is a novel skeleton antibiotic having β-lactam-like activities.     

Biosynthesis of the benz[α]anthraquinone antibiotic PD 116198

The labeling pattern obtained from incorporation of a mixture of sodium [1-¹³C]- and [s-¹³C]acetates has confirmed the irregular derivation of the benz[α]anthraquinone skeleton of the angucycline antibiotic PD 116198. Subsequent incorporation of sodium [1-¹³C, ¹⁸O₂]-, and [1-¹³C, 2-²H₃]acetates and of ¹⁸O₂ have revealed the origins of the hydrogen and oxygen atoms of the antibiotic. The possibility of a “two-chain” biosynthesis was tested by feeding ²H-labeled orsellinates; however, no incorporation was detected. PD 116198 seems most plausibly derived by rearrangement of an initially-formed linear tetracyclic intermediate.     

Aggregate, Polymer and Cluster Formation from Metal-Imino Carboxylate Complexes

Reaction of tris-(2-aminoethyl)amine (tren) andthe sodium salt of an -ketocarboxylic acid, typically sodium pyruvate, affordsin the presence of a lanthanide ion aseries of complexes and aggregates includingmononuclear, cyclic tetranuclear and polymerspecies of [L¹]^3- ([L¹]^3-=N[CH₂CH₂N=C(CH₃)COO^-]³).The aggregation of these and related d-block elementcomplexes with Na⁺ ions leadsto the formation of polymeric materials, and thefactors influencing the formation and controlof these various aggregation states are discussed.Metal cations also template the aggregationof the fragment [Ni(L²)] ([L²]^2- =CH₂[CH₂N = C(CH₃)COO^-]₂)to give, in high yield, the polynuclearaggregates {[Ni(L²)]₆M}^x+(M = Nd, Pr, Ce, La, x = 3; M = Sr, Ba, x = 2). The structures of{[Ni(L²)]₆M}^x+ show aninterstitial twelve co-ordinate, icosahedralcation M^x+ encapsulated by six [Ni(L²)]fragments. In the presence ofNa⁺, aggregation of [Ni(L²)] fragments affords {[Ni(L²)]₉Na₄(H₂O)(MeOH)(ClO₄)}³⁺ thestructure of whichshows four Na⁺ ions templating the formation ofa distorted tricapped trigonal prismatic[Ni(L²)]₉ cage. Thus, control overconstruction of various polynuclear cages viaself-assembly at octahedral junctions can beachieved using main group, transition metaland lanthanide ion templates.     

Dispersed Fluorescence Spectroscopy and Transition Dipole Moment of HCO β 2A′-X̄2A′

Dispersed fluorescence spectra of β ²A′ - x? ²A′ transitions are measured on exciting HCO to the vibrational levels (0,0,0), (0,0,1), (0,1,0) and (1,0,0) of β ²A′ in a gas cell. Vibrational energies of bound and resonant states are determined for energy up to 17 500 cm^?1 from the ground vibrational level of the x? ²A′ state. Rotationally resolved spectra of the bands β ²A′ - x? ²A′ 2⁰₃3⁰₁, 2¹₄ and 2⁰₂3¹₂ were recorded and analyzed. Abnormal intensities in the P, Q and R branches are due to the mechanism of “axis switching”. From the ratios of emission intensity of a- and b-type transitions, without taking into account the varied lifetimes of rotational states of the upper electronic state, the directions of transition dipole moments of these bands are determined to be 39 ? 43° to the inertial a axis.     

123Sb NQR and 19F NMR study of potassium,rubidium, and cesium heptafluorodiantimonates(iii)

The dynamics of crystal lattices of potassium, rubidium, and cesium heptafluorodiantimonates(iii) and specific features of internal rotations of the Sb₂F₇ fluoride groups in these compounds were studied using ¹²³Sb NQR in the temperature interval from 77 to 325 K and ¹⁹F NMR in the temperature interval from 240 to 470 K in combination with X-ray diffraction and thermogravimetric analyses. The distinctions in the dynamic behavior of the fluoride ions with changing the size (polarizability) of outer-sphere cations are discussed. The structural phase transition in CsSb₂F₇ was revealed at 425—430 K accompanied by the appearance of a high ion conductivity ( 1.3·10^–3 S cm^–1 at 450 K). A second type phase change can exist at 220—270 K.     

Diminished Respirative Growth and Enhanced Assimilative Sugar Uptake Result in Higher Specific Fermentation Rates by the MutantPichia stipitis FPL-061

A mutant strain ofPichia stipitis, FPL-061, was obtained by selecting for growth on L-xylose in the presence of respiratory inhibitors. The specific fermentation rate of FPL-061, was higher than that of the parent,Pichia stipitis CBS 6054, because of its lower cell yield and growth rate and higher specific substrate uptake rate. With a mixture of glucose and xylose, the mutant strain FPL-061 produced 29.4 g ethanol/L with a yield of 0.42 g ethanol/g sugar consumed. By comparison, CBS 6054 produced 25.7 g ethanol/L with a yield of 0.35 gJg. The fermentation was most efficient at an aeration rate of 9.2 mmoles O₂ L^-1 h^-1. At high aeration rates (22 mmoles O₂ L^-1 h^-1), the mutant cell yield was less than that of the parent. At low aeration rates, (1.1 to 2.5 O₂ L^-1 h^-1), cell yields were similar, the ethanol formation rates were low, and xylitol accumulation was observed in both the strains. Both strains respired the ethanol once sugar was exhausted. We infer from the results that the mutant, P.stipitis FPL-061, diverts a larger fraction of its metabolic energy from cell growth into ethanol production.     

Measurements of the apparent rate constant for the reaction of iodine monoxide with chlorine monoxide to form iodine atoms

An apparatus for measuring the resonance fluorescence signals of iodine and chlorine atoms is constructed to study iodine monoxide reaction with chlorine monoxide. A technique using the reaction of chlorine atoms with C₂H₆ is developed to calibrate the sensitivity of the apparatus to chlorine atoms. The apparent rate constants for the reaction between 10^• and CIO^• radicals producing iodine atoms was measured at 295 K k_app = (2.62 ± 0.57) x 10-^-11 cm³ molecule^-1 s^-1.