Inulin-containing biomass for ethanol production

The use of stalks instead of tubers as a source of carbohydrates for ethanol production has been investigated. The inulin present in the stalks of Jerusalem artichoke was extracted with water and the effect of solid-liquid ratio, temperature, and acid addition was studied and optimized in order to attain a high-fructose fermentable extract. The maximum extraction efficiency (corresponding to 35 g/L) of soluble sugars was obtained at 1/6 solidliquid ratio. Fermentations of hydrolyzed extracts by baker's yeast and direct fermentation by an inulinease activity yeast were also performed and the potential to use this feedstock for bioethanol production assessed. The results show that the carbohydrates derived from Jerusalem artichoke stalks can be converted efficiently to ethanol by acidic hydrolysis followed by fermentation with Saccharomyces cerevisiae or by direct fermentation of inulin using Kluyveromyces marxianus strains. In this last case about 30 h to complete fermentation was required in comparison with 8–9 h obtained in experiments with S. cerevisiae growth on acid extracted juices.     

Properties of two polymerisable surfactants aqueous solutions: dodecylethylmethacrylatedimethylammonium bromide and hexadecylethylmethacrylatedimethylammonium bromide. II. Partial molar volume and micelle hydration

The partial molar volume and hydration number of two micellised polymerisable surfactants (dodecylethylmethacrylatedimethylammonium bromide (C₁₂PS) and hexadecylethylmethacrylatedimethylammonium bromide (C₁₆PS)) were determined. Results support marginally the annular conformation of the polar head group (N⁺(CH₃)₂-CH₂-CH₂-O-CO-C(CH₃)(=CH₂)) proposed in the literature.     

On the importance of carbohydrate-aromatic interactions for the molecular recognition of oligosaccharides by proteins: NMR studies of the structure and binding affinity of AcAMP2-like peptides with non-natural naphthyl and fluoroaromatic residues

The specific interaction of a variety of modified hevein domains to chitooligosaccharides has been studied by NMR spectroscopy in order to assess the importance of aromatic-carbohydrate interactions for the molecular recognition of neutral sugars. These mutant AcAMP2-like peptides, which have 4-fluoro-phenylalanine, tryptophan, or 2-naphthylalanine at the key interacting positions, have been prepared by solid-phase synthesis. Their three-dimensional structures, when bound to the chitin-derived trisaccharide, have been deduced by NMR spectroscopy. By using DYANA and restrained molecular dynamics simulations with the AMBER 5.0 force field, the three-dimensional structures of the protein-sugar complexes have been obtained. The thermodynamic analysis of the interactions that occur upon complex formation have also been carried out. Regarding binding affinity, the obtained data have permitted the deduction that the larger the aromatic group, the higher the association constant and the binding enthalpy. In all cases, entropy opposes binding. In contrast, deactivation of the aromatic rings by attaching fluorine atoms decreases the binding affinity, with a concomitant decrease in enthalpy. The role of the chemical nature of the aromatic ring for establishing sugar contacts has been thus evaluated.     

Tin(IV), titanium(IV) and vanadium(IV) chloride complexes with 2-aminobenzimidazole and 2(2′-aminophenyl) benzimidazole

Summary 2-Aminobenzimidazole (abi) and 2(2-aminophenyl)benzimidazole (apbi) react with tin, titanium and vanadium tetrachlorides to yield complexes of formulae: [MCl₄(abi)](M=Sn or Ti), [TiCl₄(abi)₂], [VCl₃(abi-H)] ((abi-H) being the deprotonated ligand) and [MCl₄(apbi)] (M=Sn, Ti or V).Abi is monodentate, with the metal in a pseudooctahedral environment, so that a dimeric structure is proposed for [SnCl₄(abi)] and [TiCl₄(abi-], monomeric for [TiCl₄(abi)₂] and polymeric for [VCl₃(abi-H)]. Apbi acts as a bidentate ligand in all complexes showing a hexacoordinated environment for the metal.     

Ethanol production from olive oil extraction residue pretreated with hot water

The olive pulp fraction contained in the residue generated in olive oil extraction by a two-step centrifugation process can be upgraded by using the cellulose fraction to produce ethanol and recovering high value phenols (tyrosol and hydroxytyrosol). Olive pulp was pretreated in a laboratory scale stirred autoclave at different temperatures (150–250°C). Pretreatment was evaluated regarding cellulose recovery, enzymatic hydrolysis effectiveness ethanol production by a simultaneous saccharification and fermentation process (SSF), and phenols recovery in the filtrate. The pretreatment of olive pulp using water at temperatures between 200°C and 250°C enhanced enzymatic hydrolysis. Maximum ethanol production (11.9 g/L) was obtained after pretreating pulp at 210°C in a SSF fed-batch procedure. Maximum hydroxytyrosol recovery was obtained in the liquid fraction when pretreated at 230°C.     

Substrate-assisted antibody catalysis

A new strategy in transition-state analog design is demonstrated to elicit catalytic antibodies. The strategy is based on substrate-assisted antibody catalysis and utilizes analogs designed to mimic the transition-state for intramolecular catalysis and thereby favor antibodies that can recruit catalytic groups from substrate. The hydrolysis of the benzoyl ester of cocaine provides an illustration. The benzoyl ester of cocaine is distant from the protonated nitrogen in the stable chair conformer but proximate in the strained boat form. An antibody stabilizing the boat form and approximating ester and amine could catalyze ester hydrolysis. To mimic the transition-state for the intramolecular catalysis, we synthesized a cocaine analog that replaces this ester with a methylenephenylphosphinate bridge to the tropane nitrogen. This bridged analog elicited 85 cocaine esterases out of 450 anti-analog antibodies-a performance markedly superior to that of a simple phosphonate ester-based analog with an identical tether. The correspondence of the analog to a "high energy" conformer eliminated product inhibition. For certain polyfunctional targets, substrate assistance can be an effective strategy for eliciting catalytic antibodies.     

Characterization of crude oil biomarkers using comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry

Oil samples from Recôncavo basin (NE Brazil), previously analyzed by traditional techniques such as gas chromatography coupled to tandem mass spectrometry, were evaluated using comprehensive two‐dimensional gas chromatography coupled to quadrupole mass spectrometry and comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry along with simplified methods of samples preparation to evaluate the differences and advantages of these analytical techniques to better understand the development of the organic matter in this basin without altering the normal distribution of the compounds in the samples. As a result, the geochemical parameters calculated by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry described better the origin, maturity, and biodegradation of both samples probably by increased selectivity, resolution, and sensitivity inherent of the multidimensional technique. Additionally, the detection of the compounds such as, the C(14α‐) homo‐26‐nor‐17α‐hopane series, diamoretanes, nor‐spergulanes, C₁₉–C₂₆ A‐nor‐steranes and 4α‐methylsteranes resolved and detected by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry were key to classify and differentiate these lacustrine samples according to their maturity and deposition conditions.     

In silico identification of the protein disulfide isomerase family from a protozoan parasite

Protein disulfide isomerase (PDI) enzymes are eukaryotic oxidoreductases that catalyze the correct formation of disulfide bonds during protein folding. Structurally they are characterized by the presence of functional thioredoxin-like (Trx) domains. For the protozoan parasite causative of the human amebiasis (Entamoeba histolytica), the correct formation of disulfide bonds is important for an accurate folding of its proteins, including some virulence factors. However, little is known about the enzymes involved in this mechanism. We undertook a post-genomic approach to identify the PDI family of this parasite. The genome database survey revealed a set of 11 PDI-encoding sequences with predictable protein thiol/disulfide oxidoreductase activities.     

Screening of humic and fulvic acids in estuarine sediments by near-infrared spectrometry

Diffuse reflectance near-infrared spectroscopy (NIR) combined with partial least squares (PLS) data treatment has been employed for the rapid and nondestructive determination of sedimentary humic substances. Forty one samples of surface estuarine sediments, taken during distinct seasonal periods from different locations across Ria de Arousa (northwest of Spain), were scanned at wavelengths from 833 to 2,976 nm (12,000 to 3,360 cm⁻¹). Twenty four samples were randomly selected, from previous hierarchical cluster analysis of their NIR spectra, for the calibration set, and the 17 remaining samples were assigned to the validation set. NIR spectra of calibration samples were correlated to measured values of humic acids (HAs) and fulvic acids (FAs), which ranged from 1.53 to 28.17 mg/g and from 0.37 to 2.45 mg/g, respectively, using PLS regression and multiplicative scattering correction on the raw and first-derivative NIR spectra, respectively. Low root mean square error of prediction values of 4.3 mg HA/g sediment and 0.25 mg FA/g sediment were obtained. Good residual prediction deviation values of 1.16 and 1.2 were obtained for HA and FA, respectively, allowing the PLS models built to be considered as appropriate tools for screening purposes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Copper phosphotungstate-catalyzed microwave-assisted synthesis of 5-hydroxymethylfurfural in a biphasic system

In this paper, we have described a novel route to produce 5-hydroxymethylfurfural (HMF), a valuable platform molecule obtained from biomass. Metal-exchanged Keggin heteropolyacid salts were used as catalysts, in microwave-assisted reactions carried out in a water-ethyl acetate biphasic system. To avoid the use of homogenous Brønsted acid catalysts, which are corrosive and difficult to be reused, we have exchanged the protons of the Keggin heteropolyacids with transition metal cations. These salts were evaluated in the fructose dehydration, being the Cu_3/2PW₁₂O₄₀ the most active and selective catalyst, achieving 81% of HMF yield, after 15 min reaction at 413 K under microwave irradiation. The effects of metal cation, anion or heteropolyanion present in the catalyst were evaluated. The greatest efficiency of the Cu_3/2PW₁₂O₄₀ was attributed to its high Lewis acidic strength which allows its coordinates with the water molecules, consequently generating H₃O⁺ ions in the reaction medium. In addition, after assessing reactions of fructose dehydration in the presence of other Copper salts [i.e., CuCl₂ or Cu(NO₃)₂], we conclude the anion plays too a key role. The higher softness of phosphotungstic anion should stabilize protonate intermediates better than chloride or nitrate anions, favouring this way the reaction. Finally, although the catalyst has been soluble, it was easily reused by removing the aqueous phase and adding a new load of the substrate dissolved in ethyl acetate. The runs were successfully repeated without the loss of activity of the catalyst.

Graphical abstract