This work investigates the production of fatty acid ethyl esters from soybean oil in sub-and supercritical ethanol. The experiments were performed in a tubular reactor in the temperature range of 473-648 K, from 7 to 20 MPa, adopting the oil-to-ethanol molar ratio interval from 1:10 to 1:100. Results showed that temperature and pressure below the solvent critical point led to very low reaction conversions while appreciable yields were verified around 623 K and 20 MPa using an oil-to-solvent molar ratio of 1:40 and with a reaction time of approximately 15 min. A pseudo-first-order kinetic modeling was employed in representing the experimental alcoholysis data with a satisfactory agreement between experimental and calculated conversion values.

a b s t r a c tPervaporation experiments with PDMS membrane have been performed in a plate and frame module to investigate its ability to concentrate volatile compounds identified in an industrial soluble coffee solution. Eight compounds were chosen to depict key aroma of soluble coffee. The effect of feed flow rate, temperature and permeate pressure on the pervaporation performance has been analyzed. Concentration polarization phenomena was not identified in the feed flow rate studied. The temperature effect showed a good agreement with the nonlinear Arrhenius equation. The permeate pressure followed the solution-diffusion model behavior. Results showed that pervaporation is a promising alternative to concentrate aroma compounds from soluble coffee.

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Natural fruity aroma was produced during submerged fermentation by Pichia fermentans using sugarcane molasses as a cultivation broth. The aroma compounds were recovered from the fermentation by a pervaporation process using a polydimethylsiloxane membrane (Pervap 4060-Sulzer). Isoamyl acetate, a characteristic compound associated with fruity aromas, was the major compound produced. The pervaporation module was fed at three different temperatures to test the best conditions to recover the natural fruity aroma. The total flux (J ), partial fluxes of each component (J), and enrichment factors (β) were determined within the tested ranges. The process was performed at 45 °C, a feed flow of 1.5 mL/min and 0.1 kPa, for a duration of 13 h to concentrate the natural flavor. The pervaporation process can concentrate the isoamyl acetate from fermented broth from 9 to 61.8 mg/L in the first hour of pervaporation. As a single step of downstream operation, pervaporation was efficient for recovering and concentrating the natural fruity aroma. The obtained product was colorless and had a characteristic banana flavor.

PII proteins are important regulators of nitrogen metabolism in a wide variety of organisms: the binding of the allosteric effectors ATP, ADP, and 2-oxoglutarate (2-OG) to PII proteins affects their ability to interact with target proteins. We modeled the simultaneous binding of ATP, ADP, and 2-OG to one PII protein, namely GlnB of Escherichia coli, using a modeling approach that allows the prediction of the proportions of individual binding states. Four models with different binding rules were compared. We selected one of these models (that assumes that the binding of the first nucleotide to GlnB makes it harder for subsequent nucleotides to bind) and used it to explore how physiological concentrations of ATP, ADP, and 2-OG would affect the proportions of those states of GlnB that interact with the target proteins ATase and NtrB. Our simulations indicate that GlnB can, as suggested by previous researchers, act as a sensor of both 2-OG and the ATP:ADP ratio. We conclude that our modeling approach will be an important tool in future studies concerning the PII binding states and their interactions with target proteins.

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SummaryThis work aims at characterizing linseed oil obtained using different extraction methods (hexane, subcritical propane and pressurized ethanol), and comparing the results with commercial linseed oil extracted by cold mechanical press method. An experimental design helped to evaluate temperature and pressure effects on the oil extraction using propane and ethanol. Gas chromatography assisted in evaluating the essential fatty acids. There were no significant differences among the ω-3, 6 and 9 fatty acids from linseed oil obtained using the different extraction methods. Only the acidity of linseed oil extracted by subcritical propane (0.956%) showed significant differences among the physicochemical parameters. Extraction using organic solvent (Soxhlet) gave a 36.12% yield. Extraction using subcritical propane at 107 Pa and 40 °C for 1.5 h gave a better yield (28.39%) than pressurized ethanol (8.05%) under similar conditions. Linseed oil extraction using subcritical propane was economically viable, resulting in a 124.58 US$/L product cost. The results present subcritical propane extraction as a promising alternative for obtaining linseed oil at mild temperature and pressure conditions, without losing quality and quantity of fatty acids such as ω-3, 6 and 9.