Enhanced Xylose Recovery from Oil Palm Empty Fruit Bunch by Efficient Acid Hydrolysis

Oil palm empty fruit bunch (EFB) is abundantly available in Malaysia and it is a potential source of xylose for the production of high-value added products. This study aimed to optimize the hydrolysis of EFB using dilute sulfuric acid (H₂SO₄) and phosphoric acid (H₃PO₄) via response surface methodology for maximum xylose recovery. Hydrolysis was carried out in an autoclave. An optimum xylose yield of 91.2 % was obtained at 116 °C using 2.0 % (v/v) H₂SO₄, a solid/liquid ratio of 1:5 and a hydrolysis time of 20 min. A lower optimum xylose yield of 24.0 % was observed for dilute H₃PO₄ hydrolysis at 116 °C using 2.4 % (v/v) H₃PO₄, a solid/liquid ratio of 1:5 and a hydrolysis time of 20 min. The optimized hydrolysis conditions suggested that EFB hydrolysis by H₂SO₄ resulted in a higher xylose yield at a lower acid concentration as compared to H₃PO₄.     

Optimizing Phosphoric Acid plus Hydrogen Peroxide (PHP) Pretreatment on Wheat Straw by Response Surface Method for Enzymatic Saccharification

Wheat straw was pretreated by phosphoric acid plus hydrogen peroxide (PHP), in which temperature, time, and H₃PO₄ proportion for pretreatment were investigated by using response surface method. Results indicated that hemicellulose and lignin removal positively responded to the increase of pretreatment temperature, H₃PO₄ proportion, and time. H₃PO₄ proportion was the most important variable to control cellulose recovery, followed by pretreatment temperature and time. Moreover, these three variables all negatively related to cellulose recovery. Increasing H₃PO₄ proportion can improve enzymatic hydrolysis; however, reduction on cellulose recovery results in decrease of glucose yield. Extra high temperature or long time for pretreatment was not beneficial to enzymatic hydrolysis and glucose yield. Based on the criterion for minimizing H₃PO₄ usage and maximizing glucose yield, the optimized pretreatment conditions was 40 °C, 2.0 h, and H₃PO₄ proportion of 70.2 % (H₂O₂ proportion of 5.2 %), by which glucose yielded 299 mg/g wheat straw (946.2 mg/g cellulose) after 72-h enzymatic hydrolysis.     

Analysis of Dye Components in Red Ballpoint Pen Inks by Nonaqueous Micellar Electrokinetic Chromatography with LIF Detection

An effective and economical nonaqueous micellar electrokinetic chromatography (NAMEKC) method was developed for the analysis of dye components with similar structure in red ballpoint pen inks. The new NAMEKC method using sodium dodecyl sulfate (SDS) micelle as pseudo-stationary phase in formamide/H₂O medium provided higher resolution and better selectivity than other conventional capillary electrophoresis methods. In this study, the experimental parameters including solvent medium, acid concentration, SDS concentration, separation voltage and temperature, were optimized. The optimized conditions were formamide/H₂O (90/10, v/v) with SDS at concentration of 100 mmol and 3.5 % acetic acid (v/v). The separation voltage and temperature were of 20 kV and 25 °C, respectively. Under the optimized conditions, a good separation of three red color dyes with similar structure was achieved. This method was successfully used to analyze several red ballpoint pen inks from different manufacturers with satisfactory result. Therefore, the proposed method could be useful for the discrimination of red ballpoint pen inks in questioned documents examination.     

Rapid dissolution of spruce cellulose in H<Subscript>2</Subscript>SO<Subscript>4</Subscript> aqueous solution at low temperature

Dissolution of cellulose is the key challenge in its applications. It has been discovered that spruce cellulose with high molecular weight (4.10 × 10⁵ g mol^?1) can be dissolved in 64 wt% H₂SO₄ aqueous solution at low temperature within 2 min, and the cellulose concentration in solution can reach as high as 5 % (w/v). FT-IR spectra and XRD spectra proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The cold H₂SO₄ aqueous solution broke the hydrogen bonds among cellulose molecules and the low temperature dramatically slowed down the hydrolysis, which led to the dissolution of cellulose. The resultant cellulose solution was relatively stable, and the molecular weight of cellulose only slightly decreased after storage at ?20 °C for 1 h. Due to the high molecular weight of cellulose, cellulose solution could form regenerated films with good mechanical properties and transparency at low concentration (2 % w/v). This work has not only provided the new evidence of cellulose dissolution which facilitated the development of cellulose solvent, but also suggested a convenient way to directly transfer cellulose with high molecular weight into materials without structure modifications.     

Environmentally Friendly and Highly Efficient Co(OAc)2-Catalyzed Aerobic Oxidation to Access 2,6-Di-Electron-Donating Group Substituted 4-Hydroxybenzaldehydes

A highly efficient and green aerobic oxidation has been developed for selectively preparing a series of valuable 2,6-dialkyl-, dialkoxyl-, and alkoxylalkyl-substituted 4-hydroxybenzaldehydes from corresponding 4-cresols in good to excellent yields, using a catalytic system of Co(OAc)₂ · 4H₂O (1.0 mol%)–NaOH (1.0 equiv)–O₂ (1.0 atm) in aqueous ethylene glycol (EG/H₂O = 20/1, v/v) at 50 °C. Furthermore, a plausible mechanism was proposed for the direct oxyfunctionalization of the aromatic methyl group into the aldehyde group.     

Electricity production from lignocellulosic biomass by direct coupling of a gasifier and a nickel/yttria-stabilized zirconia-based solid oxide fuel cell: influence of the H<Subscript>2</Subscript>S content of the syngas onto performances and aging

The aim of this work is to study the reactivity of a Ni-YSZ-based solid oxide fuel cell (SOFC) fueled with gaseous mixtures having the same composition as the syngas issued from a fixed-bed downdraft and staged gasification pilot. The syngas issued from the gasifier contains some ppm(v) of H₂S, and in order to adapt the purification process, the influence of this compound on the Ni-YSZ-based SOFCs is evaluated at 600 and 850 °C. The influence of H₂S depends on fuel composition, temperature but also of current density. In H₂–N₂ mixtures and only at 600 °C, a significant decrease of cell performances is observed for H₂S?>?4.5 ppm(v). For H₂–CO–CO₂–N₂ mixtures, the influence is more important since a small decrease of performance can be observed for 1 ppm(v) of H₂S even at 850 °C. Nevertheless, at 600 °C, it is possible to avoid damage by limiting the current density. Aging experiments, realized at 750 °C, show that the influence of 1 and 2 ppm(v) of H₂S is more important during the first 20 h and is reversible: at this temperature, after poisoning with 1 ppm(v) of H₂S during 72 h, the cell recovers 91% of its initial power density after 100 h in pure hydrogen, and after subsequent poisoning with 2 ppm(v) of H₂S during 77 h, the cell recovers 94% of its initial power density after 168 h in pure hydrogen.     

Development and Validation of Nonaqueous Capillary Electrophoresis Method for Simultaneous Estimation of Icariin,Icariside II,and Epimedin K in Epimedium Leaves

This paper describes a novel nonaqueous capillary electrophoresis method for the separation and determination of Icariin, Icariside II, and Epimedin K in Epimedium leaves. Three flavonoids were extracted by ultrasonication with EtOH-H₂O (70:30) followed by a HP 20 resin column cleanup procedure. The optimized electrophoretic conditions were obtained with the running solution of 8 mM borate MeCN/H₂O (60:40, v/v) (pH 11.40), separation voltage of +20 kV and detection wavelength of 270 nm. The limits of quantification ranged from 0.24 to 0.84 mg/kg (signal/noise = 3) for three flavonoids. Three flavonoids in 10 Epimedium leaves were successfully measured and evaluated.     

A new quinoline-based chemosensor in ratiometric sensing of Hg2+ ions

A new quinoline-based chemosensor 1 has been designed and synthesised. Its metal ion-binding properties have been documented in organic and aqueous organic solvents. While chemosensor 1 recognises Hg²⁺ ions (K _a = 2.15 × 10⁴ M^? 1) by exhibiting ratiometric change in emission in CHCl₃/CH₃OH (1:1, v/v), under similar condition both Zn²⁺ and Cd²⁺ ions are sensed by significant non-ratiometric increase in emission with measurable red shift. In DMSO/H₂O (5:95, v/v), the sensor 1 exhibits a greater selectivity towards Hg²⁺ ions (K _a = 9.20 × 10³ M^? 1) over the other metal ions examined.     

Comparative potentiality of Kans grass (Saccharum spontaneum) and Giant reed (Arundo donax) as lignocellulosic feedstocks for the release of monomeric sugars by microwave/chemical pretreatment

Two-stage microwave (microwave/NaOH pretreatment followed by microwave/H₂SO₄ pretreatment) was used to release monomeric sugars from Kans grass (Saccharum spontaneum) and Giant reed (Arundo donax). The optimum pretreatment conditions were investigated, and the maximum monomeric sugar yields were compared. The microwave-assisted NaOH and H₂SO₄ pretreatments with a 15:1 liquid-to-solid ratio were studied by varying the chemical concentration, reaction temperature, and reaction time to optimize the amount of monomeric sugars. The maximum amounts of monomeric sugars released from microwave-assisted NaOH pretreatment were 6.8 g/100 g of biomass [at 80 °C/5 min, 5 % (w/v) NaOH for S. spontaneum and at 120 °C/5 min, 5 % (w/v) NaOH for A. donax]. Furthermore, the maximum amounts of monomeric sugars released from microwave-assisted H₂SO₄ pretreatment of S. spontaneum and A. donax were 33.8 [at 200 °C/10 min, 0.5 % (w/v) H₂SO₄] and 31.9 [at 180 °C/30 min, 0.5 % (w/v) H₂SO₄] g/100 g of biomass, respectively. The structural changes of S. spontaneum and A. donax were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy.     

Improved Procedure for Ruthenium‐Catalyzed Oxidative Cleavage of Alkenes With IO(OH)5

Oxidative cleavage of alkenes to carboxylic acids catalyzed by cis‐[RuCl₂(bipy)₂] · 2H₂O in the presence of IO(OH)₅ has been studied in a biphasic (CH₃CN‐CCl₄‐H₂O; 1∶1∶2 v/v) solvent system. Ruthenium tetraoxide seems to be the active catalyst species.     

Solid state of a new flavonoid derivative DA-6034

DA-6034 is a new synthetic flavonoid known to possess anti-inflammatory activity. The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of DA-6034. Six crystal forms, one hydrate form and five solvates, of DA-6034 have been isolated by recrystallization and characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and powder X-ray diffractometry (PXRD). From the DSC and TG data it was confirmed that Form 1 is monohydrate; Form 2 is DMSO solvate; Form 3 is 1/2 DMSO solvate; Form 4 is 1/2 methyl ethyl ketone solvate; Form 5 is 1.5 H₂O, 1/2 acetic acid solvate; Form 6 is 1/2 H₂O, 1/4 butanol solvate. The PXRD patterns of the six crystal forms were different respectively. In the dissolution studies in pH 6.8 ± 0.05 buffer at 37 ± 0.5 °C, the solubility of solvates was higher than that of Form 1.     

Novel 1,8-naphthalimide dye for multichannel sensing of H<Superscript>+</Superscript> and Cu<Superscript>2+</Superscript>

A novel 1,8-naphthalimide dye with simple structure has been produced by a facile synthetic method for colorimetric and fluorescent sensing of H⁺ and Cu²⁺. In CH₃CN/H₂O (1/1, v/v), the dye could monitor H⁺ using dual channels (ratiometric absorbance and fluorescence intensity change) from pH 6.2 to 12.0. Meanwhile, in the pH range of 1.9–5.2, the dye could also be used to detect Cu²⁺ using triple channels [ultraviolet–visible (UV–Vis) absorption, fluorescence intensity reduction, as well as fluorescence blueshift]. The detection limits for Cu²⁺ evaluated by colorimetric and fluorescent titration were 6.10 × 10^?7 and 2.62 × 10^?7 M, respectively. The dye exhibited specific selectivity and sensitivity for H⁺ and Cu²⁺ over various coexisting metal ions. Moreover, the sensing mechanism of the dye for H⁺ and Cu²⁺ was carefully examined.     

Hydrolysis of Tetraglycine by a Zr(IV)-Substituted Wells–Dawson Polyoxotungstate Studied by Diffusion Ordered NMR Spectroscopy

The use of diffusion ordered NMR spectroscopy (DOSY) for the analysis of complex reaction mixtures involving polyoxometalates (POMs) was demonstrated for the hydrolysis of the peptide tetraglycine by the K₁₅H[Zr(α₂-P₂W₁₇O₆₁)₂]·25H₂O Wells–Dawson type cluster. ¹H DOSY NMR studies have shown that severe signal overlap observed in the one-dimensional ¹H NMR spectrum of reaction mixtures containing a POM and peptides could be overcome by the two-dimensional character of a DOSY NMR measurement. A clear distinction between the ¹H NMR signals of the products formed during the hydrolysis of 5.0 mM of tetraglycine catalyzed by 1.0 mM of K₁₅H[Zr(α₂-P₂W₁₇O₆₁)₂]·25H₂O was observed based on the extra dimension containing information about diffusion coefficients that distinguishes a typical DOSY measurement from conventionally used 1D ¹H NMR. The spectrum clearly shows the presence of 5 species with diffusion coefficients of 3.71 × 10^?10 m²/s (3.91; 3.84; 3.82 and 3.62 ppm), 4.39 × 10^?10 m²/s (3.87; 3.76 and 3.61 ppm), 5.26 × 10^?10 m²/s (3.67 and 3.63 ppm), and 7.46 × 10^?10 m²/s (3.37 ppm) that are assigned to the non-hydrolyzed tetraglycine, the hydrolysis intermediate products triglycine and glycylglycine, and the end product of hydrolysis glycine, respectively. In addition, a signal assigned to cyclic glycylglycine, with a diffusion coefficient practically identical to the diffusion coefficient of glycylglycine was observed at 3.86 ppm. In addition, ¹H and ³¹P NMR spectroscopy were further used to study the binding of tetraglycine to K₁₅H[Zr(α₂-P₂W₁₇O₆₁)₂]·25H₂O and the solution speciation of K₁₅H[Zr(α₂-P₂W₁₇O₆₁)₂]·25H₂O.     

Application of UPLC-Quadrupole-TOF-MS Coupled with Recycling Preparative HPLC in Isolation and Preparation of Coumarin Isomers with Similar Polarity from Peucedanum praeruptorum

A strategy of ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS) coupled to recycling preparative HPLC was utilized to sensitively detect the minor constituents and preparatively isolate coumarin isomers from the petroleum ether extract of Peucedanum praeruptorum roots. UPLC-Q-TOF-MS was achieved on an Agilent ZORBAX Extend C-18 analytical column (50 mm × 2.1 mm i.d. 1.8 μm) using methanol:H₂O as the mobile phase, and three pairs of coumarin isomers with similar polarity were detected. Then recycling preparative HPLC was successfully used in one step for the isolation and purification of these six compounds with optimized mobile phases (methanol: H₂O, 73:27, 81:19, 78:22, v/v). The structures of six coumarins including three new coumarins named praeruptorin (F–H) (1, 3 and 6) were identified by spectroscopic analysis.     

Expression of Aspergillus niger IA-001 Endo-β-1,4-Xylanase in Pichia pastoris and Analysis of the Enzymic Characterization

The xylanaseB (XynB) (JX560731.1) gene of Aspergillus niger IA-001 was optimized according to the codon usage of Pichia pastoris and expressed in P. pastoris GS115. The optimized XynB expression level was increased 2.8 times relative to that of the wild-type XynB, and the dual-copy XynB (optimized) expression level was increased 1.9 times relative to that of the single-copy XynB (optimized). The activity of the dual-copy XynB ((XynB-opt)₂) was maximized at 15,158.23?±?45.11 U/mL after 120 h of shaking. The optimal temperature and pH of (XynB-opt)₂ were 50 °C and 5.0, respectively. (XynB-opt)₂ showed a high specific activity of 6,853.00?±?20.08 U/mg. IC analysis of the standard xylooligosaccharides showed that (XynB-opt)₂ was an endo-xylanase with X2 as the main degradation product. (XynB-opt)₂ was highly specific towards different natural xylans. After 24 h of hydrolysis, more than 90 % of the total hydrolysis products of xylan were X2 and X1, almost no X4?~?X6. In addition, the enzyme exhibited resistance to many metal ions and low pH values. The superior catalytic properties of (XynB-opt)₂ suggested its great potential as an effective additive in animal feed industry.     

Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters

We examine theoretically the three channels that are associated with the detachment of a single water molecule from the aqueous clusters of the alkaline earth dications, [M(H₂O) _n ]²⁺, M = Mg, Ca, Sr, Ba, n ≤ 6. These are the unimolecular water loss (M²⁺(H₂O) _n?1 + H₂O) and the two hydrolysis channels resulting the loss of hydronium ([MOH(H₂O) _n?2]⁺ + H₃O⁺) and Zundel ([MOH(H₂O) _n?3]⁺ + H₃O⁺(H₂O)) cations. Minimum energy paths (MEPs) corresponding to those three channels were constructed at the Møller–Plesset second order perturbation (MP2) level of theory with basis sets of double- and triple-ζ quality. We furthermore investigated the water and hydronium loss channels from the mono-hydroxide water clusters with up to four water molecules, [MOH(H₂O) _n ]⁺, 1 ≤ n ≤ 4. Our results indicate the preference of the hydronium loss and possibly the Zundel-cation loss channels for the smallest size clusters, whereas the unimolecular water loss channel is preferred for the larger ones as well as the mono-hydroxide clusters. Although the charge separation (hydronium and Zundel-cation loss) channels produce more stable products when compared to the ones for the unimolecular water loss, they also require the surmounting of high-energy barriers, a fact that makes the experimental observation of fragments related to these hydrolysis channels difficult.     

Acid Hydrolysis of Hemicellulose in Green Liquor Pre-Pulping Extract of Mixed Northern Hardwoods

Forest biomass is a promising resource for future biofuels and bioproducts. Pre-pulping extraction of hemicellulose by alkaline (Green Liquor) pretreatment produces a neutral-pH extract containing hemicellulose-derived oligomers. A near-term option for use of this extract is to hydrolyze the oligomers to fermentable monomer sugars. Chips of mixed northern hardwoods were cooked in a rocking digester at 160 °C for 110 min in Green Liquor at a concentration of 3% Na₂O equivalent salts on dry wood. The mass of wood extracted into the Green Liquor extract was approximately 11.4% of the debarked wood mass, which resulted in a dilute solution of oligomeric hemicelluloses sugars. The concentration of the extract was increased through partial evaporation prior to hydrolysis. Dilute sulfuric acid hydrolysis was applied at conditions ranging from 100 to 160 °C, 2% to 6% (w/v) H₂SO₄, and 2- to 258-min residence time. The maximum fermentable sugar concentration achieved from evaporated extract was 10.7 g/L, representing 90.7% of the maximum possible yield. Application of the biomass pretreatment severity function to the hydrolysis results proved to offer a relatively poor prediction of temperature and reaction time interaction. The combined severity function, which incorporates reaction time, temperature, and acid concentration, did prove to provide a useful means of trading off the combined effects of these three variables on total sugar yields.