Lower Viscosity Values Research Articles

Effect of doping by enantiomers with the different absolute configuration and phase sequence on mesomorphic, helical and electro-optical properties of highly tilted chiral anticlinic mixture

The main objective of the present work is to contribute to better understanding of the effect of the absolute configuration and phase sequences of dopants on the self-assembling and physicochemical properties as well as on the electro-optical parameters of a specific liquid crystalline mixture with a broad temperature range of the antiferroelectric phase. In order to establish this effect, the mesomorphic behaviour, helical pitch length and its handedness, spontaneous polarization and tilt angle, as well as electro-optical performance for all design mixture, are determined. The results show a broad temperature range of the antiferroelectric phase and very low melting points in all mixtures. Mixtures doped with (R) enantiomers exhibit longer helical pitch lengths, lower values of spontaneous polarization and rotational viscosity, comparable values of a tilt angle but also longer switch off times in comparison to similar mixtures doped with (S) enantiomers. The doping by the enantiomers exhibiting isotropic-ferroelectric-antiferroelectric phase sequence reveals the most significant impact on properties of the base mixture. The knowledge gained will very advantageous while designing new multicomponent liquid crystalline mixtures exhibiting the chiral tilted smectic mesophases for application in surface stabilized modes with passive and active matrix drive for utilization in photonics and optoelectronics.

Properties and Skin Compatibility of Films Based on Poly(Lactic Acid) (PLA) Bionanocomposites Incorporating Chitin Nanofibrils (CN).

Nanobiocomposites suitable for preparing skin compatible films by flat die extrusion were prepared by using plasticized poly(lactic acid) (PLA), poly(butylene succinate-co-adipate) (PBSA), and Chitin nanofibrils as functional filler. Chitin nanofibrils (CNs) were dispersed in the blends thanks to the preparation of pre-nanocomposites containing poly(ethylene glycol). Thanks to the use of a melt strength enhancer (Plastistrength) and calcium carbonate, the processability and thermal properties of bionanocomposites films containing CNs could be tuned in a wide range. Moreover, the resultant films were flexible and highly resistant. The addition of CNs in the presence of starch proved not advantageous because of an extensive chain scission resulting in low values of melt viscosity. The films containing CNs or CNs and calcium carbonate resulted biocompatible and enabled the production of cells defensins, acting as indirect anti-microbial. Nevertheless, tests made with Staphylococcus aureus and Enterobacter spp. (Gram positive and negative respectively) by the qualitative agar diffusion test did not show any direct anti-microbial activity of the films. The results are explained considering the morphology of the film and the different mechanisms of direct and indirect anti-microbial action generated by the nanobiocomposite based films.

Study on rheological behavior of Micro/Nano-silicon Carbide Particles in Ethanol by Selecting Efficient Dispersants.

A colloidal stability study of a nonaqueous silicon carbide suspension is of great significance for preparing special silicon carbide ceramics by colloidal processing. In this paper, three different chemical dispersants, which are amphiphilic, acidophilic, and alkaliphilic, are selected to compare their ability to stabilize nonaqueous slurries of silicon carbide. The analysis of the flow index factor is first used to estimate the colloidal stability of the suspensions. The results show that the addition of only 5 wt.% polyvinylpyrrolidone (PVP) forms a silicon carbide slurry with a low viscosity value of 17 mPa⋅s at 25 s−1. In addition, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS)measurements indicate that the PVP molecule is successfully adsorbed on the surface of silicon carbide. The different adsorption models are fitted, and the adsorption of PVP molecules on the surface of silicon carbide belongs to the Langmuir single-layer adsorption model. At the optimal PVP amount, the volume content of the suspension is as high as 22.27 vol.%, a Newtonian-like fluid still appears, and no agglomerate structure is formed in the system. After the volume content exceeds 22.27 vol.%, the flow index factor of the slurry begins to plummet, indicating that the slurry begins to transform from a Newtonian-like fluid to a shear-thinning fluid. The particles undergo inevitable agglomeration accompanied by the emergence of yield stress. Finally, a maximum solid loading of the system is predicted to be 46 vol.%, using the Krieger-Dougherty model.

Quantifying Total Apparent Hydraulic Fracture Conductivity and Its Significant Degradation from Systematic Bottomhole Pressure Measurements in Permian Wells

SummaryHydraulic fractures play a central role in the performance of multistage fractured horizontal wells (MFHWs) in tight and shale reservoirs. Fracture conductivity variations and connection quality between fractures and wellbore (i.e., choking skins) strongly affect well productivity. However, convincing and high-quality evaluations of hydraulic fractures for these reservoirs are rare in literature because quantifying fracture properties requires decoupling them from fracture geometry and formation properties, a difficult task in most field conditions. A data gathering and hypothesis testing program was implemented using six multifractured horizontal wells in a pad in the Delaware Basin to improve our ability to reliably forecast well performance. A systematic approach utilizing production, shut-ins, and bottomhole pressure measurements (BHP) was conducted and used to evaluate the apparent flow capacity of hydraulic fractures. Two independent techniques were used in the data analyses to characterize the hydraulic fractures; namely, pressure transients for individual wells and significant well-to-well interference signals. Both techniques render similar decline rate interpretations for the sets of fracture conductivity/permeability from analysis of the pressure data, but there is a large difference in the uncertainty of the estimated results from these two methods.The first method used a radial/linear flow regime in successive pressure buildups in three of the six wells. Simulations and theoretical analysis show that this flow regime allows decoupling fracture conductivity from fracture geometry and matrix properties. This flow regime yields the total apparent fracture conductivity (TAFC), which represents the lump sum effect of fracture conductivity. In addition, this technique characterizes the connection condition between the dominant fractures and borehole, which can be estimated from the early derivative horizontal line in pressure transient log-log diagnostic plots with minimum assumptions. Specifically, the estimated TAFC ranges from 1,140 to 1,630 md-ft at early time of well life to 525 to 855 md-ft after 100 to 139 days in production, or about a 45 to 61% reduction among these wells.The second method uses time-lag of pulse interference responses between an active and observation well. With assumptions of low, mid, and high values of fracture porosity, fracture compressibility, and fluid viscosity, characteristic fracture permeability can be estimated. Because of the large uncertainty related to the assumed fracture porosity and fracture compressibility, the pulse interference method is not likely to deliver the same certainty range as successive pressure buildups using the radial/linear flow regime.The results of this work provide a better understanding of the mechanisms of flow transport inside hydraulic fractures and at the connection between the hydraulic fractures and wellbore. The estimated TAFC and its significant decline help improve hydraulic fracturing designs and build representative reservoir models for more reliable well performance modeling and forecasting.

Processing of Zn-Substituted calcium silicate layers on Y-Tzp bioceramics by dip coating

Ceramic layers based on calcium silicate non-substituted and substituted by Zn with different thickness, were developed by immersing porous Y-TZP disks into SiO2–CaO–ZnO–P2O5 glass suspensions with ZnO contents in the range of 0–20 mol%. The effect of the disk surface porosity and the slip solid loading on the formation of the dip coated layer was investigated. Special emphasis was given to the ZnO content of the dip coating slurries and its influence on the thickness and composition of the sintered layer. The greater chemical stability of the 20 mol% ZnO-substituted glass powder during aqueous colloidal processing resulted in slips with low viscosity values; whereas the high dissolution rate of the glass having 10 mol% ZnO significantly increased the slip viscosity. The liquid entrainment mechanism at the initial stage was accelerated either by using 10 mol% ZnO-substituted glass slips or by increasing the slip solid loading. The casting rate for longer immersion times markedly increased by increasing the surface porosity of Y-TZP disks. Sintered layers with thickness ~30–70% lower were produced using the glass dip coating slip with 20 mol% ZnO in comparison to 10 mol% ZnO. The main crystalline phase of the coated sintered layers was Ca3Si3O9, Ca2ZnSi2O7 and ZnSiO4 for the glasses with 0, 10 and 20 mol% ZnO, respectively.

LIQUID ASPHALT BINDERS IN CYLINDRICAL TUBE IN TERMS OF THE OSTWALD-DE WAELE MODEL

The liquid asphalt binder in a cylindrical tube is described in terms of the Ostwald-de Waele model. The dependence of the liquid flow rate on the pressure drop; dependencies are obtained for radial distribution of the flow rate and viscosity. The medium structuring, which is most noticeable at low values of nonlinearity leads to the almost uniform profile of the core flow rate, which is typical to the plastic flow. The liquid pseudoplastic media with a law nonlinearity is characterized by the presence of a highly viscous core and a narrow region of the near-wall flow with low values of effective viscosity. With increasing in medium consistency, the average viscosity increases. This effect is most pronounced for flow motions at a small pressure drop. For low values of the pressure drop, the non-Newtonian properties of the medium lead to a significant hydraulic resistance due to the presence of the inner structure. With increasing pressure drop, hydraulic resistance decreases due to the medium destruction.

Flat Wall Proximity Effect on Micro-Particle Sedimentation in Non-Newtonian Fluids

We investigate the sedimentation of colloidal micro-spheres and red blood cells (RBCs) in non-Newtonian fluid - silicone oil with different viscosities. We use digital holographic microscopy (DHM) to obtain volumetric information of the sedimenting micro-objects. Especially, the numerical refocusing feature of DHM is used to extract the depth information of multiple particles moving inside the fluid. The effects of proximity to a flat wall and the non-Newtonian behavior on the sedimenting micro-spheres and RBCs are studied by trajectory analyzing and velocimetry. We observe that for lower viscosity values the proximity effect is more pronounced. The variation rate of the particle falling velocities versus their distance to the flat wall decreases by increasing the viscosity of the fluid. For RBCs, however, the decreasing of the velocity variations have a smoother trend. The experimental results verify the theoretical prediction that, similar to Newtonian case, a correction factor in Stokes’ law suffices for describing the wall effect.

Kinetics and microwave-assisted extractive transesterification studies of high octane methyl esters (HOME) from karanja and chicken lard oil using protic deep eutectic solvent

The bio-conversion of fatty oils recovered from chicken waste and Karanja by both enzymatic and microwave-assisted transesterification (MATE) into fatty acid methyl esters (FAME) were performed in the present investigation. Evaluation of physicochemical properties and yield of biodiesel produced reveals the production of esters from chicken waste oil to be effective than the counterparts obtained from karanja oil. Intensification of transesterification process with chicken waste oil was carried out by employing protic deep eutectic solvents (pDES) for production of high octane methyl esters (HOME). The thermophysical evaluation of synthesized pDES show low values of density, viscosity and refractive index which decrease with the further increase in temperature. The use pDES reduces the mass transfer limitation in formation of biodiesel formation at the lowest acyl acceptor ratio of 1:4. Response surface methodology based optimization for microwave-assisted biodiesel production indicate the usage of the lowest power of 1.4 kW with a minimum volume of pDES (8%) at the optimal time of 25 min yields 96.4% pure biodiesel. The composition of obtained biodiesel was evaluated with GC–MS. The resulting biodiesel obtained is suitable additive to mineral based fuels.

Effect of different processing methods on chemical and pasting properties of tamarind (<i>Tamarindus indica</i> L.) seed flours

This study investigated the effect of autoclaving, boiling and roasting methods on the chemical and pasting properties of tamarind seed flour. The flours were analyzed for proximate composition, functional properties, selected mineral contents, anti-nutrients and pasting properties. Results indicated that there were significant (p < 0.05) differences in the moisture, protein, fat, fibre, ash and carbohydrate contents of the flour samples with values that ranged from 10.26-11.36, 19.64-24.23, 2.26-4.13, 3.25-4.55, 3.48-3.98 and 52.59-59.86%, respectively. Significant (p < 0.05) differences were also observed in the values of selected functional properties and minerals (sodium, magnesium, potassium and phosphorus). Boiling method relatively reduced some of the anti-nutrients more effectively than others. Flour from boiled T. indica seeds could withstand heating and shear stress compared to other processed samples because of its low breakdown viscosity value. However, flour from roasted seeds had highest setback viscosity value among others and might withstand retrogradation better than others. Overall results indicated that autoclaved, boiled and roasted seed flours could be useful in pasta, noodle and bakery industries.Keywords: boiling, flour, pasting properties, tamarind seed flours, tamarind seeds, viscosity

Comparison of the Effects of Different Food-Grade Emulsifiers on the Properties and Stability of a Casein-Maltodextrin-Soybean Oil Compound Emulsion.

The improvement of food-grade emulsifiers in the properties and stability of complex emulsion has attracted much interest. In this study, the effects of six food-grade emulsifiers with a hydrophilic–lipophilic balance (HLB) range of 3.4–8.0 on a casein-maltodextrin-soybean oil compound emulsion were investigated by centrifugal precipitation rate (CPR), emulsifying activity index (EAI), microrheological properties, zeta potential, average particle size, and Turbiscan stability index (TSI). The optimal amounts of added succinylated monoglyceride (SMG) and polyglycerol fatty acid ester were 0.0025% and 0.1% (w/w), respectively, while that of the other four emulsifiers was 0.2% (w/w), according to the CPR. Thereinto, the SMG-stabilized emulsion exhibited the highest emulsifying activity and the lowest viscosity value and possessed the highest stability over 14 days of storage, which was indicated by the lowest TSI value and the smallest change in delta backscattering signal, relative to those of the other groups. Moreover, the emulsion stabilized by SMG displayed better emulsion stability than the control under a range of pH (6.0–8.0) and calcium ion concentrations (0–10 mM), which was attributed to the increased zeta potential value and the decreased average particle size of droplets with the addition of SMG. The present study provides a basic understanding for SMG improving the properties and stability of the complex emulsion.

Optimization of the technology for the production of foam glass aggregate

The article presents the results of a study of the state of production of a foam glass and the nomencla-ture of its products. It is shown that it is expedient to use the recycled glass obtained from the bottle battle, the defective glass and the double-glazed windows as a raw material for the production of the foam-glass. The re-quirements are formulated for glasses, which should have low viscosity values in the range of foaming tempera-tures. The features of the technology for the production of the foam glass aggregate at the specialized lines are outlined. The technology features are the composition of the charge and temperature conditions of burning. The mixture for the production of the foam glass aggregate consists of glass flour, organomineral blowing agent con-taining water and food glycerin, as distinct from the slab foam glass, where soot or coke is used as a blowing agent. The results confirm the effectiveness of the use of the foam glass aggregate as a soundproofing backfill for floors. Currently, about 70% of the foam glass aggregate is used for roofs and stylobates; the rest is used in landscape design, road construction, foundations and major repair. In the future, the areas of application of the foam glass aggregate can be significantly expanded in the direction of building systems, lightweight aggregates, etc., which involves in-depth studies of the properties of this material.

Effect of particle size distribution on rheological properties of chocolate.

This study focused on the influence of the particle size distribution (PSD) of ingredients used for chocolate preparation (cocoa powder and sugar) on viscosity of model chocolates with different fat contents. Model chocolates with varying PSDs and two particle size ratios (cocoa particles : sugar of 1 : 4 and 1 : 6) were prepared by mixing highly defatted cocoa powder as a fine fraction and sugar as coarse fraction in several proportions. Samples containing spherical quartz beads were included as a reference to gain insight into the role of particle properties. Comparing chocolate samples with the same composition, but different particle size ratio, the largest difference in viscosity was found at a proportion of coarse fraction of 0.6. This shows that at this proportion of coarse particles, the highest maximum packing fraction was reached, which is in accordance with theoretical predictions. However, for the investigated chocolate samples, the lowest viscosity values were obtained at a proportion of the coarse fraction of 0.8 or 1. This could be attributed to parameters other than PSD, such as a decrease in surface area with an increasing amount of coarse particles. Also the morphology and surface properties were shown to influence viscosity. Compared to cocoa and sugar particles, spherical and smooth quartz beads led to an improved particle packing, and therefore a lower viscosity. The addition of lecithin led to a decrease in viscosity due to a decrease in particle-particle interactions, particularly for hydrophilic sugar particles. The knowledge obtained in this study provides possible approaches on how to reduce fat content of chocolates.

A review on thermo-physical properties of bio, non-bio and hybrid nanofluids

The pressure drop and thermal performance of various nanofluids can be affected by their thermo-physical properties. However, there are many different parameters that need to be considered when determining the thermo-physical properties of nanofluids. This paper highlights a detail reviews on the thermo-physical properties of nanofluids with different material type and effect of some process parameters (such as material type, temperature and concentration) on the thermo-physical properties of nanofluids. Four thermo-physical properties mainly density, viscosity, thermal conductivity and specific heat capacity from different literatures were summarized, discussed and presented. The lowest viscosity value of nanofluids in literature was mango bark water-based nanofluid (0.81cP). On the other hand, the maximum thermal conductivity value of nanofluids in the literature was GNP-Ag water-based nanofluid (0.69W/mK). The density and specific heat capacity are strongly dependent on the material type. Meanwhile, the viscosity and thermal conductivity are greatly affected by temperature and concentration. The most influential parameters on thermo-physical properties of nanofluids are material type followed by temperature. Most of the literatures confirmed bio nanofluids have low viscosity value and hybrid have high thermal conductivity values.

KARAKTERISTIK MUTU BUBUK OKARA HASIL KERAGAMAN PERLAKUAN HIDROTERMAL DAN SUHU PENGERINGAN

The present study aimed to investigate the influences of experimental variables, i.e. hydrothermal treatments (whithout and treated) and convective drying temperatures (70, 80 and 90°C) on the quality characteristics of okara powders. The quality parameters of the okara powder studied in this experiment consisted of color attributes, particle density, water absorption capacity, oil absorption capacity, pH, viscosity, and non-enzymatic browning. The results showed that the quality of okara powders varied depending on the experimental variables. Hydrothermal treatment and drying of okara at lower temperatures could increase the brightness (L value) from 62.37 to 70.23, and increased the b value of okara powder color from 43.65 to 49.16. However, the particle density (1.04-1.35 g/cm3) and pH value (6.48-6.78) of okara powders were not significantly affected by hydrothermal treatment. The okara powder solution with hydrothermal treatment (2.10-4.50 cP) showed a lower average viscosity value compared to okara powder without hydrothermal treatment ((2.60-4.80 cP). The study also concluded that okara powder absorbed significantly more water rather than absorbing oil, as indicated by the value of water absorption capacity (4.7-5.7 mL/g), which greater than oil absorption capacity (1.1-1.4 mL/g). Non-enzymatic browning occurrence on okara powder samples (OD = 0.52-0.66) was more affected by the drying temperature than hydrothermal treatment.
 Keywords: convective drying, hydrothermal treatment, okara powder quality

Impact of fuel injection pressure on the engine characteristics of CRDI engine powered by pine oil biodiesel blend

Optimization of fuel injection strategies can maximize the utilization of biodiesel by addressing the issues concern with fuel consumption, engine performance, and exhaust gas emission. In the midst of the pervasiveness of plant-based biofuel, this paper focused on maximizing the pine oil biodiesel usage in a diesel engine having common rail direct injection (CRDI) system without any engine modifications. Pine oil derived from pine tree resins, has shown impressive fuel properties such as lower viscosity, flash point, boiling point and comparable calorific value to diesel. In this study, the impact of high fuel injection pressure on the engine characteristics of a diesel engine fueled by 30% pine oil biodiesel blend (P30) was analyzed. At standard 200 bar fuel injection pressure, the brake thermal efficiency (BTE) of P30 biodiesel blend was decreased compared to sole diesel. To improve the utilization and performance of the P30 blend, fuel injection pressure increased from 200 bar to 350 bar at a step of 50 bar. The results show that BTE and combustion characteristics are improved with an increase in injection pressure. The P30 fuel exhibits maximum BTE of 26.1% at 350 bar which is 6.9% higher the BTE of diesel at 200 bar. Exhaust emissions (CO, HC & Smoke) decreased gradually with increase in fuel injection pressure due to high atomization of fuel, faster evaporation, and formation of the better air fuel mixture. At 100% load condition, the P30 blend shows a maximum decrease in CO and HC emission at 300 bar, which is 16.6% and 13.1% less respectively compared to sole diesel at 200 bar injection pressure. The NOx is increased by about 9.4% for P30 blend at 350 bar when compared to that of Diesel at 200 bar. Thus, the blending ratio of pine oil biodiesel in the diesel can be extended by increasing the fuel injection pressure.

Modeling of Electric Current Assisted Sintering: An extended fluid-like approach for the description of powders rheological behavior

A general theoretical framework for investigating the rheological behavior of powder undergoing electric current assisted consolidation is proposed in this work. The most relevant phenomena occurring during ECAS process are taken into account. Consolidating powders are assumed to behave as a viscous fluid. Specifically, powder viscosity is expressed by the Bird–Carreau–Yasuda’s model, which includes the power-law creep description typically adopted in the ECAS modeling literature. The proposed stress-strain constitutive law allows one avoiding a priori assumptions regarding the powder rheological behavior. The resulting system of differential equations cannot be solved analytically, so that the finite-element method (FEM) numerical technique is adopted.A numerical investigation of the effect of some representative model parameters on powder consolidation is performed and the possible different rheological regimes correspondingly taking place are identified. Influence of the applied mechanical load and zero-shear rate viscosity is studied and a suitable approach to map out the powder rheological behavior is presented. It is found that powder rheological response is not only determined by the intrinsic material properties but also depends upon the process operating conditions. As an example, high values of mechanical load along with low values of zero-shear rate viscosity induce a nonlinear viscous flow while Newtonian (linear) flow takes place for low values of mechanical load associated to high values of zero-shear rate viscosity.The proposed model should be considered as a first attempt to extend the rheological theory of sintering recently proposed in the field of electric current assisted consolidation to a broader range of shear rates, which, in turn, extends the application of this theory to a wider variety of materials and operating conditions.

Quality of the surface finish of self-compacting concrete

In this work, surface damage due to the presence of pores in self-compacting concrete specimens is studied and cataloged with the QSI method which simplifies the inspection of concrete samples with optimal results, even in curved areas. 48 test tubes distributed in a total of 12 mixtures were analyzed. The rheology of the concretes was analyzed and controlled. In concretes that obtain viscosities higher than 42 Pa s, a large number of large pores are detected on its surface, compared to concretes with lower viscosity and/or shear stress. The specimen with the worst surface finish that was manufactured (mixture nº. 11) had a viscosity of 58 Pa s and a shear stress of 26 Pa (QSI = 5.9%), compared to 14 Pa s and 15 Pa, respectively, of the concrete element that less surface area affected (QSI = 0.6%). The mixes H-2, H-3 and H-12 have the combination of lower values of viscosity and shear stress. This allows obtaining the best surface finishes, with average QSI values, respectively of 1.3% 1.6% and 1.6%. By increasing the flowability of the SCC, the number of pores and their size decrease. The values of viscosity and shear stress must be balanced to ensure an adequate flowability of the SCC.

An investigation into the sensitivity of postglacial decay times to uncertainty in the adopted ice history

Abstract At the centers of previously glaciated regions such as Hudson Bay in Canada and the Gulf of Bothnia in Fennoscandia, it has been observed that the sea level history follows an exponential form and that the associated decay time is relatively insensitive to uncertainty in the ice loading history. We revisit the issue of decay time sensitivity by computing relative sea level histories for Richmond Gulf and James Bay in Hudson Bay and Ångerman River in Sweden for a suite of reconstructions of the North American and Fennoscandian Ice Sheets and Earth viscosity profiles. We find that while some Earth viscosity models do indeed show insensitivity in computed decay times to the ice history, this is not true in all cases. Moreover, we find that the location of the study site relative to the geometry of the ice sheet is an important factor in determining ice sensitivity, and based on our set of ice sheet reconstructions, conclude that the location of James Bay is not well-suited to a decay time analysis. We describe novel corrections to the RSL data to remove the effects associated with the spatial distribution of sea level indicators as well as for other signals unrelated to regional ice loading (ocean loading, rotation and global mean sea-level changes) and demonstrate that they can significantly affect the inference of viscosity structure. We performed a forward modelling analysis based on a commonly adopted 2-layer, sub-lithosphere viscosity structure to determine how the solution space of viscosity models changes with the input ice history at the three study sites. While the solution spaces depend on ice history, for both Richmond Gulf and Ångerman River there are regions of parameter space where solutions are common across all or most ice histories, indicating low ice load sensitivity for these mantle viscosity parameters. For example, in Richmond Gulf, upper mantle viscosity values of (0.3–0.5)x1021 Pa s and lower mantle viscosity values of (5–50)x1021 Pa s tend to satisfy the data constraint consistently for most ice histories considered in this study. Similarly, the Ångerman River solution spaces contain a solution with an upper mantle viscosity of 0.3 × 1021 Pa s and lower mantle viscosity values of (5–50)x1021 Pa s common to 9 of the 10 ice histories considered there. However, the dependence of the viscosity solution space on ice history suggests that joint estimation of ice and Earth parameters is the optimal approach.

Overexpression of diacylglycerol acetyltransferase from Euonymus europaeus in Yarrowia lipolytica leads to the production of single-cell oil enriched with 3-acetyl-1,2-diacylglycerols.

The 3-acetyl-1,2-diacylglycerols (acTAGs) are the molecules that are structurally similar to triacylglycerols (TAGs). They are naturally produced by plants of the family Celastraceae and animals such as Cervus nippon and Eurosta solidaginis. The presence of acetate in the sn-3 position of the glycerol backbone confers advantages to these compounds, for example, lower viscosity and calorific value compared to classical TAGs. In this work, the gene EeDAcT, which encodes diacylglycerol acetyltransferase in a species of bush (Euonymus europaeus), was overexpressed in strains Po1d (capable of accumulating storage lipids) and JMY1877 (incapable of accumulating storage lipids) of Yarrowia lipolytica, to test the activity of the gene EeDAcT and the production of acTAGs in oleaginous and nonoleaginous genetic backgrounds. It was observed that both the strains containing the gene EeDAcT (YL33 and YL35 for Po1d and JMY1877 strains, respectively) produced acTAGs. The strain YL33 accumulated up to 20% intracellular lipids, 20% of which was acTAGs, and 40% was TAGs. On the other hand, the strain YL35, which showed interrupted TAGs accumulation, produced up to 10% acTAGs as the only storage lipid. Unfortunately, the quantity of acTAGs produced in YL35 was insignificant, as the overall lipid accumulated in the strain was not more than 4% of the biomass. The fatty acid profile of acTAGs produced by the YL33 strain was remarkably similar to TAGs, and both of these structures were rich in oleic (45%) and palmitic (25%) acids.

Influence of ionic plasticizers on the processing and viscosity of starch melts

Maize starch was plasticized by glycerol, choline chloride ([Chol][Cl]) and ionic liquids (Choline acetate ([Chol][Ace]), 1-Ethyl-3-methylimidazolium Chloride ([EMIM][Cl]) and 1-Ethyl-3-methylimidazolium acetate ([EMIM][Ace]). Melt rheology at 120 °C was assessed with a twin-screw micro-compounder used for processing small quantities (8−10 g), and with a capillary rheometer with pre-shearing (Rheoplast). Qualitative agreement was found between shear viscosities obtained by both rheometry devices, showing the interest of the micro-compounder for screening of plasticizers’ influence. The lower shear viscosity values were obtained in presence of [EMIM][Ace] whereas [Chol][Cl] led to the largest ones. Rather than processing induced macromolecular degradation, the glass transition temperature depressing effect of the plasticizers was found to better explain viscosity differences. This underlines the strong influence of the nature of the plasticizers on starch melt rheology. Finally, results from extensional viscosity shows the specific influence of [EMIM][Ace], suggesting that this plasticizer could be particularly relevant for thermoplastic starch processing.