Purification and Characterisation of a Thermostable β-Xylosidase from <Emphasis Type="Italic">Aspergillus niger</Emphasis> van Tieghem of Potential Application in Lignocellulosic Bioethanol Production

A locally isolated strain of Aspergillus niger van Tieghem was found to produce thermostable β-xylosidase activity. The enzyme was purified by cation and anion exchange and hydrophobic interaction chromatography. Maximum activity was observed at 70–75 °C and pH 4.5. The enzyme was found to be thermostable retaining 91 and 87% of its original activity after incubation for 72 h at 60 and 65 °C, respectively, with 52% residual activity detected after 18 h at 70 °C. Available data indicates that the purified β-xylosidase is more thermostable over industrially relevant prolonged periods at high temperature than those reported from other A. niger strains. Maximum activity was observed on p-nitrophenyl-β-d-xylopyranoside and the enzyme also hydrolysed p-nitrophenyl β-d-glucopyranoside and p-nitrophenyl α-l-arabinofuranoside. The purified enzyme acted synergistically with A. niger endo-1,4-β-xylanase in the hydrolysis of beechwood xylan at 65 °C. During hydrolysis of pretreated straw lignocellulose at 70 °C using a commercial lignocellulosic enzyme cocktail, inclusion of the purified enzyme resulted in a 19-fold increase in the amount of xylose produced after 6 h. The results observed indicate potential suitability for industrial application in the production of lignocellulosic bioethanol where thermostable β-xylosidase activity is of growing interest to maximise the enzymatic hydrolysis of lignocellulose.     

Thermodynamic properties and functions of condensed Bi<Subscript>8</Subscript>O<Subscript>11</Subscript>

The values of ΔH°₂₉₈, S°₂₉₈, H°₂₉₈–H°₀, T, ΔH _fus, and C _p(T), as well as the temperature dependences of the Gibbs energy function, are calculated for Bi₈O₁₁ oxide by proven computational methods.     

Potential of Mangrove-Associated Endophytic Fungi for Production of Carbohydrolases with High Saccharification Efficiency

The endophytic fungi represent a potential source of microorganisms for enzyme production. However, there have been only few studies exploiting their potential for the production of enzymes of industrial interest, such as the (hemi)cellulolytic enzymatic cocktail required in the hydrolysis of lignocellulosic biomass. Here, a collection of endophytic fungi isolated from mangrove tropical forests was evaluated for the production of carbohydrolases and performance on the hydrolysis of cellulose. For that, 41 endophytic strains were initially screened using a plate assay containing crystalline cellulose as the sole carbon source and the selected strains were cultivated under solid-state fermentation for endoglucanase, β-glucosidase, and xylanase enzyme quantification. The hydrolysis of a cellulosic material with the enzymes from endophytic strains of the Aspergillus genus resulted in glucose and conversion values more than twofold higher than the reference strains (Aspergillus niger F12 and Trichoderma reesei Rut-C30). Particularly, the enzymes from strains A. niger 56 (3) and A. awamori 82 (4) showed a distinguished saccharification performance, reaching cellulose conversion values of about 35% after 24 h. Linking hydrolysis performance to the screening steps played an important role towards finding potential fungal strains for producing enzymatic cocktails with high saccharification efficiency. These results indicate the potential of mangrove-associated endophytic fungi for production of carbohydrolases with efficient performance in the hydrolysis of biomass, thus contributing to the implementation of future biorefineries.     

Thermodynamic Properties of Zincate-Manganites of LaM<Subscript>2</Subscript> <Superscript>II</Superscript>ZnMnO<Subscript>6</Subscript> (М<Superscript>II</Superscript> = Mg,Ca, Sr,Ba) Composition

Temperature dependences of the heat capacity of new zincate-manganites of LaM₂^IIZnMnO₆ (M^II = Mg, Ca, Sr, Ba) composition are studied via experimental calorimetry in the interval of 298.15–673 K. It is found that all compounds have λ-shape effects on the curve of dependence C_p° ~ ?(T) with respect to phase transitions of the second kind. Equations for the temperature dependence of the heat capacity are derived with allowance for phase transition temperatures, and thermodynamic functions H°(T) ? H°(298.15), S°(T) and Φ^xx(T) are calculated on the basis of experimental data on C_p°(T) and the calculated S°(298.15) value.     

Synthesis and heat capacity of NdVO<Subscript>4</Subscript> in the temperature range of 384–859 K

Heat capacity of NdVO₄ was determined in the temperature range of 384–859 K using differential scanning calorimetry. The thermodynamic functions (H°(T)–H°(384 K), S°(T)–S°(384 K), and Φ°) of neodymium orthovanadate were calculated using the experimental C_p = f(T) values. The structure of NdVO₄ was studied at 298 and 973 K.     

Thermodynamic Properties of Polyphenylquinoxaline in the Temperature Range of <Emphasis Type="Italic">T</Emphasis> → 0 to 570 K

The thermodynamic properties of amorphous polyphenylquinoxaline in the temperature range of 6 to 570 K are studied via precision adiabatic vacuum calorimetry and differential scanning calorimetry. The thermodynamic characteristics of glass transition are determined. Standard thermodynamic functions C^°_p, H°(T) ? H°(0), S°(Т) ? S°(0), and G°(T) ? H°(0) in the range of T → 0 to 570 K and the standard entropy of formation at T = 298.15 K are calculated. The low-temperature (T ≤ 50 K) heat capacity is analyzed using a multifractal model for the processing of heat capacity, fractal dimension D values are determined, and conclusions on the topological structure of the compound are drawn.     

Thermodynamic properties of first- and third-generation carbosilane dendrimers with terminal phenyldioxolane groups

The heat capacities of first- and third-generation carbosilane dendrimers with terminal phenyldioxolane groups are studied as a function of temperature via vacuum and differential scanning calorimetry in the range of 6 to 520 K. Physical transformations that occur in the above temperature range are detected and their standard thermodynamic characteristics are determined and analyzed. Standard thermodynamic functions C_p^ο(T), [H°(T) ? H°(0)], [S°(T) ? S°(0)], and [G°(T) ? H°(0)] in the temperature range of T → 0 to 520 K for different physical states and the standard entropies of formation of the studied dendrimers at T = 298.15 K are calculated, based on the obtained experimental data.     

Synthesis and study of high-temperature heat capacity of erbium orthovanadate

Orthovanadate ErVO₄ has been prepared by solid-phase synthesis from a stoichiometric mixture of high pure V₂O₅ and chemically pure Er₂O₃ by multistage calcination in air in the temperature range 873–1273 K. The effect of temperature (380–1000 K) on the heat capacity of orthovanadate ErVO₄ was studied by hightemperature calorimetry. Thermodynamic properties of erbium orthovanadate (enthalpy change H°(T)–H°(380 K), entropy change S°(T)–S°(380 K), and reduced Gibbs energy Φ°(T)) have been calculated from the experimental C_p = f(T) data. It has been shown that the specific heat varies in a row of oxides and orthovanadates of Gd-Lu naturally depending on the radius of the R³⁺ ion within the third and fourth tetrads.     

Thermodynamic properties of triphenylantimony dibenzoate

The temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph₃Sb(OC(O)Ph)₂ is studied in the range of 6–480 K by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry. The melting of the compound is observed in this temperature range, and its standard thermodynamic characteristics are identified and analyzed. Ph₃Sb(OC(O)Ph)₂ is obtained in a metastable amorphous state in a calorimeter. The standard thermodynamic functions of Ph₃Sb(OC(O)Ph)₂ in the crystalline and liquid states are calculated from the obtained experimental data: C_p^°(T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) for the region from T → 0 to 480 K. The standard entropy of formation of the compound in the crystalline state at T = 298.15 K is determined. Multifractal processing of the low-temperature (T < 50 K) heat capacity of the compound is performed. It is concluded that the structure of the compound has a planar chain topology.     

Thermodynamics of the terpolymer of carbon monoxide,ethylene, and 1-butene

The heat capacity and the temperatures and enthalpies of physical transformations of the alternating terpolymer of carbon monoxide, ethylene, and 1-butene (the content of butene units is 10.7 mol.%) were studied by adiabatic and differential scanning calorimetry in the temperature range from 6 to 520 K. The energy of terpolymer combustion was measured at 298.15 K on an calorimeter with an isothermal shell and static bomb. The standard thermodynamic functions C°_p(T), H°(T)–H°(0), S°(T)–S°(0), and G°(T)–H°(0) for the range from Т → 0 to 400 K, the standard enthalpy of combustion, and the thermodynamic parameters of formation of the partially crystalline CO—ethylene—1-butene terpolymer at 298.15 K, as well as the thermodynamic characteristics of its synthesis in the range from T → 0 to 400 K were calculated.     

Standard Thermodynamic Functions of Crystalline Arsenate Mg<Subscript>0.5</Subscript>Zr<Subscript>2</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>3</Subscript> in the Range from <Emphasis Type="Italic">T</Emphasis> → 0 to 670 K

The temperature dependence of heat capacity C^° _p = f(T) of crystalline arsenate Mg_0.5Zr₂(AsO₄)₃ was studied by precision adiabatic vacuum and differential scanning calorimetry in the temperature range 8?670 K. The standard thermodynamic functions C^° _p (T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) of the arsenate for the range from Т → 0 to 670 K and the standard formation entropy at Т = 298.15 K were calculated from the obtained experimental data. Based on the low-temperature capacity data (30–50 K) the fractal dimension D of the arsenate was determined, and the topology of its structure was characterized. The results were compared with the thermodynamic data for the structurally related crystalline phosphates M_0.5Zr₂(PO₄)₃ (M = Mg, Ca, Sr, Ba, Ni) and arsenate NaZr₂(AsO₄)₃.     

Production of ethanol from waste paper using immobilized yeasts

This work is aimed at a selection of yeast strains suitable for simultaneous saccharification and fermentation of waste paper. The waste paper, as a lignocellulosic material, represents an unconventional source for the production of ethanol which is a promising alternative fuel. The yeast strains Saccharomyces cerevisiae and Pichia kudriavzevii produced the highest amounts of ethanol at 30 °C and were also resistant at 40 °C during the first 92 h of fermentation. These two strains were immobilized by entrapment into poly(vinyl alcohol) hydrogel lens-shaped particles LentiKats^®. The immobilized S. cerevisiae was a better ethanol producer and retained higher metabolic activity in repeated batch fermentations than P. kudriavzevii. The immobilized S. cerevisiae was also suitable for a long-term storage, with 23% decrease in the ethanol production ability after 1-year storage of yeast cells.     

Ethanol Production from Starch Hydrolyzates using <Emphasis Type="Italic">Zymomonas mobilis</Emphasis> and Glucoamylase Entrapped in Polyvinylalcohol Hydrogel

The glucoamylase from Aspergillus niger, immobilized into poly(vinylalcohol) hydrogel lens-shaped capsules LentiKats®, was used for simultaneous saccharification and fermentation (SSF) with Zymomonas mobilis in free form. This system was stable in both the repeated batch and continuous mode of SSF. The microorganism was found to adsorb on the capsules with immobilized enzyme. This increased the ethanol productivity of the repeated batch system with 5% w/v of immobilized glucoamylase almost 2.1 times (7.2 g l^?1 h^?1) compared to free enzyme–free microorganism system (3.5 g l^?1 h^?1). The continuous SSF with the immobilized glucoamylase (11.5% w/v) tested for 15 days had productivity 10 g l^?1 h^?1, which is comparable to continuous experiments on semi-defined glucose medium (10 g l^?1 h^?1). These two systems were stable in both glucoamylase activity and microorganism productivity.     

A quantum-chemical study of the thermodynamic properties of the CNOH<Subscript>3</Subscript> isomers

The B3LYP/6-311++G(3df,3pd) DFT method was used to determine the geometry and vibrational frequencies for the formamide, formaldoxime, nitrosomethane, oxaziridine, and formimide. The potential energy functions of the hindered internal rotations were calculated. The conformers of formaldoxime and formimide were determined. For all the molecules, including the conformers, the thermodynamic characteristics Δ_f H° (298 K), S°(298 K), C _p(298 K), and Δ_f G° (298 K) were determined. The temperature dependences C _p(T) within 298–1500 K were represented in the form of cubic polynomials.     

Thermodynamic properties of a liquid crystal carbosilane dendrimer

The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6–370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C_p^°(T), H°(T) ? H°(0), S°(T) ? S°(0), and G°(T) ? H°(0) are calculated from the obtained experimental data for the region of Т → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at Т = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.     

NH<Subscript>4</Subscript>V<Subscript>3</Subscript>O<Subscript>7</Subscript>: Synthesis,morphology, and optical properties

The effect of the method used for the synthesis of NH₄V₃O₇ on its morphology, textural parameters, and optical properties was studied. Ammonium vanadate NH₄V₃O₇ was prepared by treating NH₄VO₃ in the presence of citric acid under hydrothermal (4.0 ≤ pH ≤ 5.5, T = 180–200°C, 48 h) and microwave–hydrothermal (3.5 ≤ pH ≤ 5.0, T = 180–220°C, 20 min) conditions. Self-assembled NH₄V₃O₇ microcrystals crystallizing in monoclinic system with unit cell parameters a = 12.247(5) Å, b = 3.4233(1) Å, c = 13.899(4) Å, β = 89.72(3)°, and V = 582.3(4) ų (space group P2₁) were shown to be formed independently of the method used to treat the reaction mixture. The morphology of NH₄V₃O₇ particles was shown to depend on рН of the reaction mass and the method of synthesis. The structural features of NH₄V₃O₇ were studied by IR, UV, and Vis spectroscopy, and the optical bandgap was determined.     

X-ray diffraction and thermodynamic characteristics for tellurite of the composition Li<Subscript>2</Subscript>CeTeO<Subscript>5</Subscript>

Tellurite of the composition Li₂CeTeO₅ is synthesized by solid-phase method from cerium(IV) and tellurium(IV) oxides and lithium carbonate. The type of syngony, the unit cell parameters, and the compound’s X-ray and pycnometry densities are determined via X-ray diffraction analysis. The isobaric heat capacity of lithium–cerium tellurite is studied by means of dynamic calorimetry in the temperature range of 298.15–673 K; the results serve as the basis for deriving C _p ^° ~ f(T) dependency equations and determining the compound’s thermodynamic functions. λ-shaped anomalous effects, due probably to Type II phase transitions, are found on the C _p ^° ~ f(T) dependence.     

Thermodynamics of a third-generation poly(phenylene-pyridyl) dendron decorated with dodecyl groups in the range of <Emphasis Type="Italic">T</Emphasis> → 0 to 480 K

The heat capacity of a glassy third-generation poly(phenylene-pyridyl) dendron decorated with dodecyl groups is studied for the first time via high-precision adiabatic vacuum and differential scanning calorimetry in the temperature range of 6 to 520 K. The standard thermodynamic functions (molar heat capacity C_p^°, enthalpy H°(T), entropy S°(T), and Gibbs energy G°(T)-H°(0)) in the range of T → 0 to 480 K, and the entropy of formation at 298.15 K, are calculated on the basis of the obtained data. The thermodynamic properties of the dendron and the corresponding third-generation poly(phenylene-pyridyl) dendrimer studied earlier are compared.     

Catalytic removal of soot particles over MnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> catalysts prepared by the auto-combustion method

Soot removal for exhaust gas from diesel engine has been addressed due to the more stringent legislation and environmental concerns. MnCo₂O₄ catalysts were systematically prepared using glucose as a fuel via the auto-combustion method and applied for soot removal. The as-prepared samples were characterized by X-ray diffraction (XRD), O₂-temperature-programmed oxidation (TPO) reaction and H₂-temperature-programmed reduction reaction (H₂-TPR). The catalytic activities for soot combustion were evaluated by micro activity test (MAT) with a tight contact mode between soot and catalysts. Compared with catalysts prepared by the solid state method without glucose, auto-combustion method in the presence of glucose can decrease the synthetic temperature, avoiding high temperature treatment and sintering. The catalysts prepared with glucose could catalyze soot oxidation effectively and the derived values of T₁₀, T₅₀, and T₉₀ were 326, 408, and 468 °C in a tight contact mode, respectively, showing a significant drop of T₁₀, T₅₀, and T₉₀ by 156, 177, and 178 °C for non-catalytic reaction.     

High-pressure defect phase La<Subscript>x</Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

Perovskite-like nonstoichiometric oxide La _x Cu₃V₄O₁₂ (space group Im \(\bar 3\), Z = 2, a = 7.313–7.354 Å) with cation-site vacancies has been prepared for the first time at high pressures (p = 6.0–8.0 GPa) and high temperatures (T = 700–1100°C). The compound has metal-type conductivity and paramagnetic properties, and undergoes a phase transition.