Enzymatic hydrolysis of mercerized and unmercerized sisal pulp

Enzymatic saccharification of sisal cellulosic pulp has been investigated. Brazil leads global production of lignocellulosic sisal fiber, which has high cellulose content, an important property for producing glucose via saccharification. Hence, sisal pulp can be a good alternative for use in biorefineries. Prior to enzymatic hydrolysis, the starting pulp [85 ± 2% α-cellulose, 15 ± 2% hemicelluloses, 1.2 ± 2% insoluble lignin, viscometric average molar mass (MMvis) 19,357 ± 590 g mol^?1, crystallinity index (CI) 74%] was pretreated with alkaline aqueous solution (mercerization, 20 g of pulp L^?1, 20% NaOH, 50 °C). The changes in the properties of the cellulosic pulp during this pretreatment were analyzed [α-cellulose content, MMvis, CI, pulp fiber dimensions, and scanning electron microscopy (SEM)]. The unmercerized and mercerized (97.4 ± 2% α-cellulose, 2.6 ± 2% hemicelluloses, 0.3 ± 0.1% insoluble lignin, MMvis 94,618 ± 300 g mol^?1, CI 68%) pulps were subjected to enzymatic hydrolysis (48 h, commercial cellulase enzymes, 0.5 mL g^?1 pulp); during the reactions, aliquots consisting of unreacted pulp and liquor were withdrawn from the medium at certain times and characterized (unreacted pulp: MMvis, CI, fiber dimensions, SEM; liquor: high-performance liquid chromatography). The changes in pulp properties observed during mercerization facilitated access of enzymes to cellulose chains, and the yield of the hydrolysis reaction increased from 50.2 (unmercerized pulp) to 89.0% (mercerized pulp). These initial results for enzymatic hydrolysis of sisal pulp indicate that it represents a good alternative biomass for bioethanol production.     

Thermal behavior of carbon nanotubes decorated with gold nanoparticles

Three different forms of carbon, i.e., multi-walled carbon nanotubes (CNTs), single-walled CNTs, and soot, were decorated with gold nanoparticles by a new method. In this method C₁₀H₈ ⁻ ions transfer electrons to the CNTs or soot. These electrons on the carbon surface can then reduce Au³⁺ species to form supported Au nanoparticles with a narrow particle size distribution. Thermogravimetric/differential thermal analyses (TG/DTA), XRD, Raman, and TEM show that naphthalene molecules remain trapped inside the Au nanoparticles and can only be removed by treatment at ca. 300 °C. Remarkable effect of the Au nanoparticles on the oxidation of carbon by O₂ is also observed by TG/DTA, i.e., on-set oxidation temperature and activation energy (E _a). It is shown that as the Au particle size decreases from 25 to 2 nm a linear decrease of the oxidation temperature is observed. Au particles larger than 25 nm do not produce any significant effect on carbon oxidation. These results are discussed in terms of spillover catalytic effect where Au nanoparticles activate O₂ molecules to produce active oxygen species which oxidize the different carbon supports.     

NMR property calculations and experimental study of the 1,6-epoxycarvone and α-epoxypinene: a comparison of models

This work aims at using theoretical calculations of shielding tensors (σ) through different methods [gauge-independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM)] and spin-spin coupling constants J using GIAO method to compare these methods and to corroborate the data obtained with the assignment of all of (1)H and (13)C NMR signals and the relative stereochemistry of the 1,6-epoxycarvone and the α-epoxypinene. All the (1)H and (13)C NMR signals were assigned unequivocally. The stereochemistry for the epoxides is trans and the B3LYP theory level with CSGT and IGAIM methods is the best choice to evaluate theoretical chemical shifts for compounds studied.     

Antinociceptive and anti-inflammatory effects of a lectin-like substance from Clitoria fairchildiana R. Howard seeds

Lectins are proteins that have the ability to bind specifically and reversibly to carbohydrates and glycoconjugates, without altering the structure of the glycosyl ligand. They are found in organisms such as viruses, plants and humans, and they have been shown to possess important biological activities. The objective of this study was to purify and characterize lectins in the seeds of Clitoria fairchildiana, as well as to verify their biological activities. The results indicated the presence of a lectin (CFAL) in the glutelin acid protein fraction, which agglutinated native rabbit erythrocytes. CFAL was purified by column chromatography ion-exchange, DEAE-Sephacel, which was obtained from a peak of protein retained in the matrix by applying 0.5 M NaCl using the step-wise method. Electrophoretic analysis of this lectin in SDS-PAGE indicated a two band pattern protein molecular mass of approximately 100 and 116 kDa. CFAL proved to be unspecific to all carbohydrates/glycoconjugates in common use for the sugar inhibition test. This lectin showed no significant cytotoxicity to human red blood cells. It was observed that CFAL has anti-inflammatory activity in the paw edema induced by carrageenan model, in which a 64% diminution in edema was observed. Antinociceptive effects were observed for CFAL in the abdominal writhing test (induced by acetic acid), in which increasing doses of the lectin caused reduction in the number of contortions by up to 72%. It was concluded that the purified and characterized lectin from the seeds of Clitoria fairchildiana has anti-inflammatory and antinociceptive activity, and is not cytotoxic to human erythrocytes.     

Thermal,structural and rheological properties of starch from avocado seeds (Persea americana,Miller) modified with standard sodium hypochlorite solutions

The avocado (Persea americana, Miller) is a tree that is native to Central/North America (Mexico) and it is very popular worldwide due to its food applications. Its seeds contain an important amount of starch and there is lack of study and understanding regarding the physico-chemical properties of this biopolymer. In this research, starch granules were extracted from avocado seeds and oxidised with standard sodium hypochlorite solutions at 0.5, 1.0 and 2.0 %. Untreated and modified samples were investigated using the following techniques: simultaneous thermogravimetry–differential thermal analysis, differential scanning calorimetry, non-contact atomic force microscopy, rapid viscoamylographic analysis and X-ray powder patterns diffractometry. The main purpose was to investigate the thermal, structural and rheological behaviour of native and oxidised avocado starch, and it was verified that the treated samples showed a decrease in gelatinisation enthalpy and average roughness as well as in the degree of relative crystallinity and pasting properties.     

Gamma to alpha phase transformation in FeCoV alloys

The effects of filing FeCoV alloys with equiatomic FeCo and up to 14 at% V is studied by Mössbauer spectroscopy and X-ray diffraction. We observed that filing eliminates the paramagnetic component observed in samples in the form of plates. The filed material also presents a linear increase of the lattice parameter and a linear decrease of the average hyperfine field of the alpha phase due to extra low-field satellites with increasing vanadium contents. This indicates that filing produces a gamma to alpha phase transformation, which increases the amount of vanadium in solid solution in the FeCo alpha phase.