Performance Evaluation and Site Application of a Hydrophobic Long-Chain Ester-Based CO2 Fracturing Fluid Thickener

Nowadays, there are a wide variety of thickeners developed for dry CO2 fracturing worldwide, but numerous problems remain during in situ testing. To address problems in CO2 fracturing fluid operation (high frictional drag, low viscosity, low proppant-carrying capacity, narrow reservoir fractures, etc.), the authors have synthesized the novel hydrophobic long-chain ester thickener, studied viscosity, frictional drag, and proppant-carrying capacity of CO2 fracturing fluid and core damage by CO2 fracturing fluid by varying the temperature, pressure, and level of injection of the novel thickener and explored the thickening mechanism for this thickener in CO2. Based on the study results, as the temperature, pressure, and amount of injected thickener increased, fracturing fluid viscosity increased steadily. In the case of shearing for 125 min under conditions of 170 S−1, 40°C, and 20 MPa, when the thickener level increased from 1% to 2%, fracturing fluid viscosity increased and then decreased, varying within 50–150 mPa·s, and the viscosity-enhancing effect was evident; under conditions of 20°C and 12 MPa, as the flow rate increased, drag reduction efficiency reached 78.3% and the minimal proppant settling speed was 0.09 m/s; under conditions of 40°C and 20 MPa, drag reduction efficiency reached 77.4% and the proppant settling speed was 0.08 m/s; with the increases in temperature, pressure, and injection amount, core damage rates of the thickener varied within 1.77%–2.88%, indicating that basically no damage occurred. This study is of significant importance to the development of CO2 viscosity enhancers and CO2 fracturing operation.

Expression, Characterisation and Homology Modelling of a Novel Hormone-Sensitive Lipase (HSL)-Like Esterase from Glaciozyma antarctica

Microorganisms, especially those that survive in extremely cold places such as Antarctica, have gained research attention since they produce a unique feature of the protein, such as being able to withstand at extreme temperature, salinity, and pressure, that make them desired for biotechnological application. Here, we report the first hormone-sensitive lipase (HSL)-like esterase from a Glaciozyma species, a psychrophilic yeast designated as GlaEst12-like esterase. In this study, the putative lipolytic enzyme was cloned, expressed in E. coli, purified, and characterised for its biochemical properties. Protein sequences analysis showed that GlaEst12 shared about 30% sequence identity with chain A of the bacterial hormone-sensitive lipase of E40. It belongs to the H group since it has the conserved motifs of Histidine-Glycine-Glycine-Glycine (HGGG)and Glycine-Aspartate-Serine-Alanine-Glycine (GDSAG) at the amino acid sequences. The recombinant GlaEst12 was successfully purified via one-step Ni-Sepharose affinity chromatography. Interestingly, GlaEst12 showed unusual properties with other enzymes from psychrophilic origin since it showed an optimal temperature ranged between 50–60 °C and was stable at alkaline pH conditions. Unlike other HSL-like esterase, this esterase showed higher activity towards medium-chain ester substrates rather than shorter chain ester. The 3D structure of GlaEst12, predicted by homology modelling using Robetta software, showed a secondary structure composed of mainly α/β hydrolase fold, with the catalytic residues being found at Ser232, Glu341, and His371.

Functionalizing benzothiadiazole with non-conjugating ester groups as side chains in a donor–acceptor polymer improves solar cell performance

Side chain ester substitution on donor–acceptor based conjugated polymers used as solar harvesters in a bulk-heterojunction (BHJ) polymer solar cell (PSC) can improve harvesting properties, phase separation in the active layer and PSC performance.

Changes in Free Amino Acid Content in the Flesh and Peel of ‘Cavendish’ Banana Fruit as Related to Branched-chain Ester Production, Ripening, and Senescence

The concentrations of free amino acids in the peel and pulp of banana (Musa sp., AAA group, Cavendish subgroup, cv. Valery) fruit during ripening at 22 °C were measured. All 20 amino acids were quantified at seven distinct ripening stages as defined by measures of internal ethylene, O2, and CO2 concentrations, aroma volatile emissions, and peel color. Volatile production commenced 2 days after the peak in ethylene production and 1 day following the climacteric peak in internal CO2. The maximum rate of branched-chain ester synthesis occurred 2 to 3 days after its onset. Production of 2-methylpropyl and 3-methylbutyl esters was much higher in the pulp compared with the peel, confirming that the pulp, rather than the peel, is the primary site of banana aroma synthesis. Of the amino acids measured, only leucine, valine, and cysteine increased concomitantly with ester formation. This was observed in the pulp, but not in the peel. The data suggest the metabolic pathways for valine and leucine formation also support, respectively, the synthesis of 2-methylpropyl and 3-methylbutyl esters. It is not clear how leucine and valine can accumulate despite the fact that they act as feedback inhibitors of their respective synthetic pathways. There was a slight peak in the formation of several other amino acids in the pulp (e.g., alanine, arginine, asparagine, glutamine, and methionine) coinciding with the climacteric respiratory peak in CO2, but a similar pattern was not seen for the peel. These data are the first to demonstrate distinct differences in amino acid metabolism in the peel and pulp of banana related to their role in ripening and aroma biosynthesis.

The Pear Aroma in the Austrian Pinot Blanc Wine Variety: Evaluation by Means of Sensorial-Analytical-Typograms with regard to Vintage, Wine Styles, and Origin of Wines

The perceived pear aroma in wines was associated with various short- and medium-chain ester compounds. A consumer study confirmed this assumption. In total, eight ester compounds from a series of 100 aromatic substances were associated with the pear aroma. In this study, a valid stable isotope dilution assay headspace solid-phase microextraction gas chromatography mass spectroscopy (SIDA-HS-SPME-GC-MS) method was developed for the analysis of these compounds, and 102 Austrian Pinot blanc wines of vintages 2013–2016 were analysed. They were assessed with regard to vintage and origin influences as well as wine styles. However, an attempt was made to capture the synergies of these compounds for the pear aroma. With the detection of ethyl (E,Z)-2,4-decadienoate and methyl (E)-geranoate, two volatile compounds were measured which had not previously been detected in Austrian wines. The eight analysed esters were perceived very differently. Therefore, specific odour activity values for the various sensations could be calculated with a mathematical combination of the analyses and the results of the sensory studies. A vintage influence on the sensorial descriptor “overripe pear” and a relationship between wine style and total pear aroma were determined.

An exploration of O—H...O and C—H...π interactions in a long-chain-ester-substituted phenylphenol: methyl 10-[4-(4-hydroxyphenyl)phenoxy]decanoate

An understanding of the driving forces resulting in crystallization vs organogel formation is essential to the development of modern soft materials. In the molecular structure of the title compound, methyl 10-[4-(4-hydroxyphenyl)phenoxy]decanoate (MBO10Me), C23H30O4, the aromatic rings of the biphenyl group are canted by 6.6 (2)° and the long-chain ester group has an extended conformation. In the crystal, molecules are linked by O—H...O hydrogen bonds, forming chains along [10\overline{3}]. The chains are linked by C—H...O hydrogen bonds, forming layers parallel to the ac plane. The layers are linked by C—H...π interactions, forming a three-dimensional supramolecular structure. The extended structure exhibits a lamellar sheet arrangement of molecules stacking along the b-axis direction. Each molecule has six nearest neighbors and the seven-molecule bundles stack to form a columnar superstructure. Interaction energies within the bundles are dominated by dispersion forces, whereas intercolumnar interactions have a greater electrostatic component.