A Novel N-Doped Nanoporous Bio-Graphene Synthesized from Pistacia lentiscus Gum and Its Nanocomposite with WO3 Nanoparticles: Visible-Light-Driven Photocatalytic Activity

This paper reports the synthesis of a new nitrogen-doped porous bio-graphene (NPBG) with a specific biomorphic structure, using Pistacia lentiscus as a natural carbon source containing nitrogen that also acts as a bio-template. The obtained NPBG demonstrated the unique feature of doped nitrogen with a 3D nanoporous structure. Next, a WO₃/N-doped porous bio-graphene nanocomposite (WO₃/NPBG-NC) was synthesized, and the products were characterized using XPS, SEM, TEM, FT-IR, EDX, XRD, and Raman analyses. The presence of nitrogen doped in the structure of the bio-graphene (BG) was confirmed to be pyridinic-N and pyrrolic-N with N1 peaks at 398.3 eV and 400.5 eV, respectively. The photocatalytic degradation of the anionic azo dyes and drugs was investigated, and the results indicated that the obtained NPBG with a high surface area (151.98 m²/g), unique electronic properties, and modified surface improved the adsorption and photocatalytic properties in combination with WO₃ nanoparticles (WO₃-NPs) as an effective visible-light-driven photocatalyst. The synthesized WO₃/NPBG-NC with a surface area of 226.92 m²/g displayed lower bandgap and higher electron transfer compared with blank WO₃-NPs, leading to an increase in the photocatalytic performance through the enhancement of the separation of charge and a reduction in the recombination rate. At the optimum conditions of 0.015 g of the nanocomposite, a contact time of 15 min, and 100 mg/L of dyes, the removal percentages were 100%, 99.8%, and 98% for methyl red (MR), Congo red (CR), and methyl orange (MO), respectively. In the case of the drugs, 99% and 87% of tetracycline and acetaminophen, respectively, at a concentration of 10 mg/L, were removed after 20 min.     

Biosynthesis of Poly-(3-hydroxybutyrate) under the Control of an Anaerobically Induced Promoter by Recombinant Escherichia coli from Sucrose

Poly-(3-hydroxybutyrate) (PHB) is a polyester with biodegradable and biocompatible characteristics and has many potential applications. To reduce the raw material costs and microbial energy consumption during PHB production, cheaper carbon sources such as sucrose were evaluated for the synthesis of PHB under anaerobic conditions. In this study, metabolic network analysis was conducted to construct an optimized pathway for PHB production using sucrose as the sole carbon source and to guide the gene knockout to reduce the generation of mixed acid byproducts. The plasmid pMCS-sacC was constructed to utilize sucrose as a sole carbon source, and the cascaded promoter P_3nirB was used to enhance PHB synthesis under anaerobic conditions. The mixed acid fermentation pathway was knocked out in Escherichia coli S17-1 to reduce the synthesis of byproducts. As a result, PHB yield was improved to 80% in 6.21 g/L cell dry weight by the resulted recombinant Escherichia coli in a 5 L bed fermentation, using sucrose as the sole carbon source under anaerobic conditions. As a result, the production costs of PHB will be significantly reduced.     

Insoluble carbonaceous materials as electron shuttles enhance the anaerobic/anoxic bioremediation of redox pollutants: Recent advances

Carbonaceous materials can accelerate extracellular electron transfer for the biotransformation of many recalcitrant, redox-sensitive contaminants and have received considerable attention in fields related to anaerobic bioremediation. As important electron shuttles(ESs), carbonaceous materials effectively participate in redox biotransformation processes, especially microbially-driven Fe reduction or oxidation coupled with pollutions transformation and anaerobic fermentation for energy and by-pro...     

Electrode reactions of tungstate ions in the presence of carbon monoxide

Tungstate ions may be reversibly reduced at platinum, rhodium and mercury electrodes in phosphoric acid according to the reaction WO₄^2-+e^- ? WO₄^3-. The specific rate constants (k_s) on Pt, Rh and Hg are 1.2.10^-2, 7.0.10^-3, and 6.5.10^-4 cm/sec, respectively. In the presence of carbon monoxide, hydrogen evolution at Pt and Rh is blocked while the electron transfer for tungstate reduction is unhindered. This is used as a criterion for a surface dissociation or recombination step in an electrochemical reaction. Two methods may be used with platinum or rhodium electrodes for the determination of tungstate, either rotating the electrode at a constant speed and measuring the diffusion current, or measuring the reduction peak height at a constant potential scan rate.     

Preparation and properties of substituted iron tungstates

Polycrystalline samples of members of the systems Fe_2?xCr_xWO₆ and Fe_1?xMn_xWO₄ were prepared and single crystals of Fe_1?xMn_xWO₄ were grown by chemical vapor transport. Their crystallographic parameters and electrical properties were characterized. Fe₂WO₆ crystallizes with the tri-α-PbO₂ structure and is an n-type semiconductor. For 0.3 ≤ x ≤ 2, the system Fe_2?xCr_xWO₆ crystallizes with the inverse trirutile structure and is nonconducting due to blocking of iron(II)-iron(III) conduction paths by chromium(III). For 0 ≤ x ≤ 1, the system Fe_1?xMn_xWO₄ crystallizes with the wolframite structure and shows p-type semiconducting behavior. The nature of the variation of resistivity with x of Fe_1?xMn_xWO₄ suggests that interchain electron transfer may occur in this structure.     

Synthesis and electrocatalytic properties of microsized Ag2WO4 and nanoscaled MWO4 (M=Co, Mn)

Microstructured Ag₂WO₄ with shuttle-like shape was synthesized via a precipitation process with assistance of Arabic gum. MWO₄ (M=Co and Mn) nanocrystals were prepared facilely via a hydrothermal procedure. The as-prepared samples were identified and characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy, respectively. The resultant samples were used directly as electrocatalysts modified on a glassy carbon electrode for p-nitrophenol, K₂CrO₄ and H₂O₂ reduction in a basic solution. The results showed that all peak currents increased markedly but the corresponding peak potential decreased by using CoWO₄, MnWO₄ and Ag₂WO₄ in turn by comparing to a bare glassy carbon electrode, and Ag₂WO₄, CoWO₄ and MnWO₄ exhibited enhanced electrocatalytic activity for p-nitrophenol reduction. Ag₂WO₄ also showed effective electrocatalytic activity for K₂CrO₄ and H₂O₂ reduction, but both CoWO₄ and MnWO₄ almost displayed very weak electrocatalytic properties for K₂CrO₄ and H₂O₂ reduction in basic solution.     

X-Ray and Electron Microscopy Studies of Rare-Earth Tungsten Bronzes

Rare-earth tungsten bronzes, RE_xWO₃, of perovskite tungsten-bronze (PTB) type, formed by conventional solid-state synthesis, have been studied by X-ray powder diffraction, electron diffraction in combination with microanalysis, and high-resolution transmission electron microscopy (HRTEM). The X-ray patterns indicated cubic PTB type structure with a≈3.83 Å (subcell), while the electron microscopy study indicated a lowering of the subcell symmetry and a complex superstructure. The upper phase composition limit, x≤0.25, for the RE_xWO₃ bronzes with PTB-related structures was established from the microanalysis study. Ordered, disordered and microtwinned superstructures were revealed by electron diffraction patterns and HRTEM images taken along 〈110〉_p. The superstructure is due to filling of the interstices in the WO₃ structure with the rare-earth ions. A hypothetical model of the superstructure based on the contrast features in the HRTEM images has been deduced. The relationships between the RE_xWO₃ bronzes formed by solid-state synthesis under high- and ambient-pressure conditions are presented.     

Degradation of Triclosan under Aerobic, Anoxic, and Anaerobic Conditions

Triclosan (2, 4, 4??-trichloro-2??-hydroxyl diphenyl ether) is a broad-spectrum antimicrobial agent present in a number of house hold consumables. Aerobic and anaerobic enrichment cultures tolerating triclosan were developed and 77 bacterial strains tolerating triclosan at different levels were isolated from different inoculum sources. Biodegradation of triclosan under aerobic, anoxic (denitrifying and sulphate reducing conditions), and anaerobic conditions was studied in batch cultures with isolated pure strains and enrichment consortium developed. Under aerobic conditions, the isolated strains tolerated triclosan up to 1?g/L and degraded the compound in inorganic-mineral-broth and agar media. At 10?mg/L level triclosan, 95?±?1.2% was degraded in 5?days, producing phenol, catechol and 2, 4-dichlorophenol as the degradation products. The strains were able to metabolize triclosan and its degradation products in the presence of monooxygenase inhibitor 1-pentyne. Under anoxic/anaerobic conditions highest degradation (87%) was observed in methanogenic system with acetate as co-substrate and phenol, catechol, and 2, 4-dichlorophenol were among the products. Three of the isolated strains tolerating 1?g/L triclosan were identified as Pseudomonas sp. (BDC 1, 2, and 3).     

Obligately anaerobic bacteria in biotechnology

New obligately anaerobic bacteria are being discovered at an accelerating rate and it is becoming very evident that the diversity of anoxic biotransformations has been greatly underestimated. Furthermore, among contemporary anaerobes there are many that thrive in extreme environments including, for example, an impressive array of both archaebacterial and eubacterial hyperthermophiles. Free energy for growth and reproduction may be conserved not only via fermentations but also by anoxygenic photophosphorylation and other modes of creating transmembrane proton potential. Thus forms of anaerobic respiration in which various inorganic oxidants (or indeed carbon dioxide) serve as terminal electron acceptors have greatly extended the natural habitats in which such organisms may predominate. Anaerobic bacteria are, however, often found in nature as members of close microbial communities (consortia) that, although sustained by syntrophic and other relations between component species, are liable to alter their composition and character in response to environmental changes, e.g., availability of terminal oxidants. It follows that the biotechnological exploitation of obligately anaerobic bacteria must be informed by knowledge both of their biochemical capacities and of their normal environmental roles. It is against this background that illustrative examples of the activities of anaerobic bacteria are considered under three heads:

1. Biodegradation/Bioremediation, with special reference to the anaerobic breakdown of aromatic and/or halogenated organic substances;
2. Biosynthesis/Bioproduction, encompassing normal and modified fermentations; and
3. Biotransformations, accomplished by whole or semipermeabilized organisms or by enzymes derived therefrom, with particular interest attaching to the production of chiral compounds by a number of procedures, including electromicrobial reduction.

     

Potent Activity of a High Concentration of Chemical Ozone against Antibiotic-Resistant Bacteria

Background: Health care-associated infections (HAIs) are a significant public health problem worldwide, favoring multidrug-resistant (MDR) microorganisms. The SARS-CoV-2 infection was negatively associated with the increase in antimicrobial resistance, and the ESKAPE group had the most significant impact on HAIs. The study evaluated the bactericidal effect of a high concentration of O₃ gas on some reference and ESKAPE bacteria. Material and Methods: Four standard strains and four clinical or environmental MDR strains were exposed to elevated ozone doses at different concentrations and times. Bacterial inactivation (growth and cultivability) was investigated using colony counts and resazurin as metabolic indicators. Scanning electron microscopy (SEM) was performed. Results: The culture exposure to a high level of O₃ inhibited the growth of all bacterial strains tested with a statistically significant reduction in colony count compared to the control group. The cell viability of S. aureus (MRSA) (99.6%) and P. aeruginosa (XDR) (29.2%) was reduced considerably, and SEM showed damage to bacteria after O₃ treatment Conclusion: The impact of HAIs can be easily dampened by the widespread use of ozone in ICUs. This product usually degrades into molecular oxygen and has a low toxicity compared to other sanitization products. However, high doses of ozone were able to interfere with the growth of all strains studied, evidencing that ozone-based decontamination approaches may represent the future of hospital cleaning methods.     

Conductivity of composite materials based on Me2(WO4)3 and WO3 (Me = Sc,In)

Composites {Me₂(WO₄)₃ ? xWO₃} (Me = Sc, In) (x = 0.5–99%) are synthesized and characterized by XRD and electron microscopy methods and also by the density and specific surface measurements. Temperature dependences of the total conductivity of composites are measured. The contributions of σ_tot and σ_el are assessed by the $\sigma (a_{O_2 } )$ and EMF methods. The concentration dependences of conductivity and activation energy are plotted based on the σ_tot and σ_ion data. It is shown that (a) in the interval x = 0–30 vol % WO₃ (0–70 mol %), the conductivity is independent of composition and the ionic component prevails; (b) in the interval x = 60–94.5 vol % (90–99 mol %), the electron conductivity prevails and increases with the increase in x; (c) in the x interval of 30–60 vol % WO₃ (70–90 mol %), the conductivity is mixed, i.e., electron(n-type)-ionic; the latter region represents the transition interval from ionic to electron conductivity as x increases. These data are compared with the results obtained earlier for MeWO₄-WO₃ composites (Me = Ca, Sr, Ba). As regards the structural topology, the {Me₂(WO₄)₃ ? xWO₃} composites pertain to the randomly distributed type. It is shown that in contrast to {Me^IIWO₄ · xWO₃} composites, the composites under study do not form the nonautonomous interface phase with the high ionic conductivity. The possible reasons for the observed differences in the topology and the conduction type of composites based on MeWO₄ and Me₂(WO₄)₃ are analyzed.     

Structure and “oxidation behavior” of W24O70, a new member of the {103} CS series of tungsten oxides

Reduced tungsten trioxide crystals WO_3?x, formed by vapor transport from a preparation with bulk composition WO_?2.90, have been studied by X-ray diffraction and electron microscopy. A single-crystal X-ray investigation showed the existence of the ordered {103} CS-structure W₂₄O₇₀, a new member of the homologous series W_nO_3n?2. Electron diffraction patterns of crystal fragments, with a few exceptions, showed the presence of the W₂₄O₇₀ phase (composition WO_2.917). Lattice images, however, indicated a fairly ordered {103} CS-phase, W₂₄O₇₀, intergrown with slabs of WO₃ giving gross compositions of the examined crystals in the range WO_2.93WO_2.96. The wide WO₃ slabs were probably formed by an oxidation process during the preparation.     

The structures of intergrowth tungsten bronzes of Ba,Sn, Pb,and Sb

The structures of intergrowth tungsten bronzes (ITB) of compositions Ba_0.04WO₃, Sn_0.04WO₃, Pb_0.04WO₃, Sn_0.18WO₃, and Sb_0.25WO₃ have been deduced from high-resolution electron microscope images. Both the Pb_0.04, Sn_0.04, and Ba_0.04, ITB phases consist of single rows of hexagonal tunnels occupied by Pb, Sn, or Ba atoms intergrown in a WO₃-like matrix. The Sb_0.25, ITB phase is composed of similar rows of Sb-containing single hexagonal tunnels, the centers of which are separated by a WO₃-like matrix only two octahedra in thickness. The structure of the Sn_0.18, ITB phase consists of double rows of hexagonal tunnels containing Sn atoms joined by a single strip of WO₃-like octahedra. The structures are compared with the structures of other known ITB phases and the nonstoichiometric behavior of these phases is discussed.     

Synthesis of monoclinic WO3 nanosphere hydrogen gasochromic film via a sol–gel approach using PS-b-PAA diblock copolymer as template

A monoclinic tungsten trioxide (WO₃) nanosphere film was synthesized via a sol–gel approach using an amphiphilic diblock copolymer polystyrene-b-polyacrylic acid (PS-b-PAA) as template in toluene. The morphology, surface area and crystal structure of as-synthesized WO₃ were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET (N₂) and powder X-ray diffraction (XRD). The XRD pattern of WO₃ nanosphere film can be identified as a pure monoclinic WO₃ phase. The WO₃ precursor nanospheres had diameters ranging from 20 to 150 nm and surface area of 78.8 m² g^?1. The hydrogen gasochromic experiments revealed that such WO₃ nanosphere film with high surface area had a rapid response (5 ～ 10 s) to pure hydrogen at room temperature.     

Isolation,Molecular Identification and Amino Acid Profiling of Single-Cell-Protein-Producing Phototrophic Bacteria Isolated from Oil-Contaminated Soil Samples

In the current study, soil samples were gathered from different places where petrol and diesel filling stations were located for isolation of photosynthetic bacteria under anaerobic conditions using the paraffin wax-overlay pour plate method with Biebl and Pfennig’s medium. The three isolated strains were named Rhodopseudomonas palustris SMR 001 (Mallapur), Rhodopseudomonas palustris NR MPPR (Nacahram) and Rhodopseudomonas faecalis N Raju MPPR (Karolbagh). The morphologies of the bacteria were examined with a scanning electron microscope (SEM). The phylogenetic relationship between R. palustris strains was examined by means of 16S rRNA gene sequence analysis using NCBI-BLAST search and a phylogenetic tree. The sequenced data for R. palustris were deposited with the National Centre for Biotechnology Research (NCBI). The total amino acids produced by the isolated bacteria were determined by HPLC. A total of 14 amino acids and their derivatives were produced by the R. palustris SMR 001 strain. Among these, carnosine was found in the highest concentration (8553.2 ng/mL), followed by isoleucine (1818.044 ng/mL) and anserine (109.5 ng/mL), while R. palustris NR MPPR was found to produce 12 amino acids. Thirteen amino acids and their derivatives were found to be produced from R. faecalis N Raju MPPR, for which the concentration of carnosine (21601.056 ng/mL) was found to be the highest, followed by isoleucine (2032.6 ng/mL) and anserine (227.4 ng/mL). These microbes can be explored for the scaling up of the process, along with biohydrogen and single cell protein production.     

One‐step electrodeposition of amorphous carbon films containing WO3 with high conductivity and good wettability

Tungsten trioxide‐incorporated hydrogenated amorphous carbon (WO₃/a‐C:H) films have been fabricated on a single‐crystal silicon wafer by liquid phase electrodeposition using methanol as carbon source and tungsten carbonyl as incorporated reagent. The morphology, composition and structure of the films have been investigated by SEM, XPS, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscope (TEM), respectively. The effects of WO₃ incorporation on the electrical and wetting properties were studied in detail. The characterization results showed that tungsten trioxide nanocrystalline particles with diameters in the range of 10–20 nm were homogenously embedded in the amorphous carbon films. Also, the electrical conductivity and wetting ability of the films were strongly improved due to the contribution of the tungsten trioxide. Copyright © 2010 John Wiley & Sons, Ltd.     

Microbial Degradation of Chlorogenic Acid by a <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. Strain

In order to elucidate the metabolism of chlorogenic acid by environmental microbes, a strain of Sphingomonas sp. isolated from tobacco leaves was cultured under various conditions, and chlorogenic acid degradation and its metabolites were investigated. The strain converting chlorogenic acid was newly isolated and identified as a Sphingomonas sp. strain by 16S rRNA sequencing. The optimal conditions for growth and chlorogenic acid degradation were 37 °C and pH 7.0 with supplementation of 1.5 g/l (NH₄)₂SO₄ as the nitrogen source and 2 g/l chlorogenic acid as the sole carbon source. The maximum chlorogenic acid tolerating capability for the strain was 5 g/l. The main metabolites were identified as caffeic acid, shikimic acid, and 3,4-dihydroxybenzoic acid based on gas chromatography-mass spectrometry analysis. The analysis reveals the biotransformation mechanism of chlorogenic acid in microbial cells isolated from the environment.     

Determination of total arsenic in soil and arsenic-resistant bacteria from selected ground water in Kandal Province, Cambodia

Cambodia has geological environments conducive to generation of high-arsenic groundwater and people are at high risk of chronic arsenic exposure. The aims of this study are to investigate the concentration of total arsenic and to isolate and identify arsenic-resistant bacteria from selected locations in Kandal Province, Cambodia. The INAA technique was used to measure the concentration of total arsenic in soils. The arsenic concentrations in soils were above permissible 5 mg/kg, ranging from 5.34 to 27.81 mg/kg. Bacteria resistant to arsenic from two arsenic-contaminated wells in Preak Russey were isolated by enrichment method in nutrient broth (NB). Colonies isolated from NB was then grown on minimal salt media (MSM) added with arsenic at increasing concentrations of 10, 20, 30, 50, 100 and 250 ppm. Two isolates that can tolerate 750 ppm of arsenic were identified as Enterobacter agglomerans and Acinetobacter lwoffii based on a series of biochemical, physiological and morphological analysis. Optimum growth of both isolates ranged from pH 6.6 to 7.0 and 30–35 °C. E. agglomerans and A. lwoffii were able to remove 66.4 and 64.1 % of arsenic, respectively at the initial concentration of 750 ppm, within 72 h of incubation. Using energy dispersive X-ray technique, the percentage of arsenic absorbed by E. agglomerans and A. lwoffii was 0.09 and 0.15 %, respectively. This study suggested that arsenic-resistant E. agglomerans and A. lwoffii removed arsenic from media due to their ability to absorb arsenic.     

An In Situ Carbonization–Replication Method to Synthesize Mesostructured WO3/C Composite as Nonprecious‐Metal Anode Catalyst in PEMFC

A meostructured WO₃/C composite with crystalline framework and high electric conductivity has been synthesized by a new in situ carbonization–replication route using the block copolymer (poly(ethylene glycol)‐block‐poly(propylene glycol)‐block‐poly(ethylene glycol)) present in situ in the pore channels of mesoporous silica template as carbon source. X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetry differential thermal analysis, and N₂ adsorption techniques were adopted for the structural characterization. Cyclic voltammetry, chronoamperometry, and single‐cell test for hydrogen electrochemical oxidation were adopted to characterize the electrochemical activities of the mesoporous WO₃/C composite. The carbon content and consequent electric conductivity of these high‐surface‐area (108–130 m² g^?1) mesostructured WO₃/C composite materials can be tuned by variation of the duration of heat treatment, and the composites exhibited high and stable electrochemical catalytic activity. The single‐cell test results indicated that the mesostructured WO₃/C composites showed clear electrochemical catalytic activity toward hydrogen oxidation at 25 °C, which makes them potential non‐precious‐metal anode catalysts in proton exchange membrane fuel cell.     

An outline of the structure of new layered bismuth lanthanum tungstate,Bi2−xLaxWO6 (x = 0.4–1.1)

An outline of the structure of a continuous solid-solution series Bi_2?xLa_xWO₆ with x = 0.4–1.1 (space group P2/c and Z = 8) has been determined from a lattice imaging method of electron microscopy. A high-resolution lattice image of Bi_1.4La_0.6WO₆ selected as representative of the series showed that the structure consists of a regular stacking of Bi_1.4La_0.6O₂ layers interleaved with WO₄ layers. A structural model of Bi_2?xLa_xWO₆ was proposed and atomic coordinates were estimated on the basis of the model. The structural relations between Bi_2?xLa_xWO₆ and Bi₂WO₆ were discussed.