Characterization of a Defined Cellulolytic and Xylanolytic Bacterial Consortium for Bioprocessing of Cellulose and Hemicelluloses

Diminishing fossil fuel reserve and increasing cost of fossil hydrocarbon products have rekindled worldwide effort on conversion of lignocellloloses (plant biomass) to renewable fuel. Inedible plant materials such as grass, agricultural, and logging residues are abundant renewable natural resources that can be converted to biofuel. In an effort to mimic natural cellulolytic–xylanolytic microbial community in bioprocessing of lignocelluloses, we enriched cellulolytic–xylanolytic microorganisms, purified 19 monocultures and evaluated their cellulolytic–xylanolytic potential. Five selected isolates (DB1, DB2, DB7, DB8, and DB13) were used to compose a defined consortium and characterized by 16S ribosomal RNA gene sequence analysis. Nucleotide sequence blast analysis revealed that DB1, DB2, DB7, DB8, and DB13 were respectively similar to Pseudoxanthomonas byssovorax (99%), Microbacterium oxydans (99%), Bacillus sp. (99%), Ochrobactrum anthropi (98%), and Klebsiella trevisanii (99%). The isolates produced an array of cellulolytic–xylanolytic enzymes (filter paper cellulase, β-glucosidase, xylanase, and β-xylosidase), and significant activities were recorded in 30 min. Isolates DB1 and DB2 displayed the highest filter paper cellulase: 27.83 and 31.22 U mg⁻¹, respectively. The highest β-glucosidase activity (18.07 U mg⁻¹) was detected in the culture of isolate DB1. Isolate DB2 produced the highest xylanase activity (103.05 U mg⁻¹), while the highest β-xylosidase activity (7.72 U mg⁻¹) was observed with DB13. Use of microbial consortium in bioprocessing of lignocelluloses could reduce problems such as incomplete synergistic enzymes, end-product inhibition, adsorption, and requirement for high amounts of enzymes in direct use of enzymes.     

The nature of unsupported uranium-ruthenium bonds: a combined experimental and theoretical study

Four new uranium-ruthenium complexes, [(Tren(TMS))URu(η(5)-C(5)H(5))(CO)(2)] (9), [(Tren(DMSB))URu(η(5)-C(5)H(5))(CO)(2)] (10), [(Ts(Tolyl))(THF)URu(η(5)-C(5)H(5))(CO)(2)] (11), and [(Ts(Xylyl))(THF)URu(η(5)-C(5)H(5))(CO)(2)] (12) [Tren(TMS)=N(CH(2)CH(2)NSiMe(3))(3); Tren(DMSB)=N(CH(2)CH(2)NSiMe(2)tBu)(3)]; Ts(Tolyl)=HC(SiMe(2)NC(6)H(4)-4-Me)(3); Ts(Xylyl)=HC(SiMe(2)NC(6)H(3)-3,5-Me(2))(3)], were prepared by a salt-elimination strategy. Structural, spectroscopic, and computational analyses of 9-12 shows: i) the formation of unsupported uranium-ruthenium bonds with no isocarbonyl linkages in the solid state; ii) ruthenium-carbonyl backbonding in the [Ru(η(5)-C(5)H(5))(CO)(2)](-) ions that is tempered by polarization of charge within the ruthenium fragments towards uranium; iii) closed-shell uranium-ruthenium interactions that can be classified as predominantly ionic with little covalent character. Comparison of the calculated U-Ru bond interaction energies (BIEs) of 9-12 with the BIE of [(η(5)-C(5)H(5))(3)URu(η(5)-C(5)H(5))(CO)(2)], for which an experimentally determined U-Ru bond disruption enthalpy (BDE) has been reported, suggests BDEs of approximately 150 kJ mol(-1) for 9-12.     

Palladium- and nickel-catalyzed aminations of aryl imidazolylsulfonates and sulfamates

A nickel complex derived from dppf, along with NaOt-Bu as the base, allowed for challenging aminations of aryl sulfamates. An improved functional group tolerance is observed in novel palladium-catalyzed aminations of imidazolylsulfonates with rac-BINAP as the ligand.     

Metal-free direct arylations of indoles and pyrroles with diaryliodonium salts

Direct arylations of indoles and pyrroles with differently substituted diaryliodonium salts were shown to efficiently proceed in the absence of metal catalysts.     

Halide, amide, cationic, manganese carbonylate, and oxide derivatives of triamidosilylamine uranium complexes

Treatment of the complex [U(Tren(TMS))(Cl)(THF)] [1, Tren(TMS) = N(CH(2)CH(2)NSiMe(3))(3)] with Me(3)SiI at room temperature afforded known crystalline [U(Tren(TMS))(I)(THF)] (2), which is reported as a new polymorph. Sublimation of 2 at 160 °C and 10(-6) mmHg afforded the solvent-free dimer complex [{U(Tren(TMS))(μ-I)}(2)] (3), which crystallizes in two polymorphic forms. During routine preparations of 1, an additional complex identified as [U(Cl)(5)(THF)][Li(THF)(4)] (4) was isolated in very low yield due to the presence of a slight excess of [U(Cl)(4)(THF)(3)] in one batch. Reaction of 1 with one equivalent of lithium dicyclohexylamide or bis(trimethylsilyl)amide gave the corresponding amide complexes [U(Tren(TMS))(NR(2))] (5, R = cyclohexyl; 6, R = trimethylsilyl), which both afforded the cationic, separated ion pair complex [U(Tren(TMS))(THF)(2)][BPh(4)] (7) following treatment of the respective amides with Et(3)NH·BPh(4). The analogous reaction of 5 with Et(3)NH·BAr(f)(4) [Ar(f) = C(6)H(3)-3,5-(CF(3))(2)] afforded, following addition of 1 to give a crystallizable compound, the cationic, separated ion pair complex [{U(Tren(TMS))(THF)}(2)(μ-Cl)][BAr(f)(4)] (8). Reaction of 7 with K[Mn(CO)(5)] or 5 or 6 with [HMn(CO)(5)] in THF afforded [U(Tren(TMS))(THF)(μ-OC)Mn(CO)(4)] (9); when these reactions were repeated in the presence of 1,2-dimethoxyethane (DME), the separated ion pair [U(Tren(TMS))(DME)][Mn(CO)(5)] (10) was isolated instead. Reaction of 5 with [HMn(CO)(5)] in toluene afforded [{U(Tren(TMS))(μ-OC)(2)Mn(CO)(3)}(2)] (11). Similarly, reaction of the cyclometalated complex [U{N(CH(2)CH(2)NSiMe(2)Bu(t))(2)(CH(2)CH(2)NSiMeBu(t)CH(2))}] with [HMn(CO)(5)] gave [{U(Tren(DMSB))(μ-OC)(2)Mn(CO)(3)}(2)] [12, Tren(DMSB) = N(CH(2)CH(2)NSiMe(2)Bu(t))(3)]. Attempts to prepare the manganocene derivative [U(Tren(TMS))MnCp(2)] from 7 and K[MnCp(2)] were unsuccessful and resulted in formation of [{U(Tren(TMS))}(2)(μ-O)] (13) and [MnCp(2)]. Complexes 3-13 have been characterized by X-ray crystallography, (1)H NMR spectroscopy, FTIR spectroscopy, Evans method magnetic moment, and CHN microanalyses.     

X-ray difffraction studies on samarium up to one megabar pressure

Abstract

High—pressure crystal structure studies have been performed on Sm up to 100 GPa using synchrotron x-radiation and a diamond anvil cell. The structural sequence Sm-dhcp-fcc-dist.fcc has been confirmed. There is no evidence of any volume collapse. The bulk modulus and its pressure derivative have been determined (B₀ = 30.7 GPa, B₀’ = 2.5).     

High-pressure study of neptunium and plutonium compounds

Abstract

Neptunium and plutonium monopnictides and monochalcogenides were studied by x-ray diffraction at pressures up to 57 GPa. All of them exhibit structural phase transitions under pressure. The arsenides and tellurides have a CsCl (B2) type high-pressure structure. Sb as an anion favours a tetragonal high-pressure structure. The compressibilities were determined for all of the compounds studied. The results are compared to those obtained for the corresponding thorium and uranium compounds.     

General diagram of the phase remtions of actinide metals under pressure

Abstract

The proposed diagram is based on the results of high-pressure X-ray diffraction work and visualizes the general trends in phase relations of actinide metals under pressure. The transition from dhcp to ccp, which occurs under the action of pressure in heavy actinides and light lanthanides, also occurs with decreasing atomic number at ambient pressure. The same structural sequence is found in the lanthanide and the actinide metals, but its first two members, hcp and Sm-type, are missing in the actinide metals, and the phase transitions are shifted to lower pressures and higher atomic numbers in the actinides.