Pedro C. Simões

Supercritical fluid extraction of lipids from the heterotrophic microalga Crypthecodinium cohnii

Microalgae biomass can be a feasible source of ω‐3 fatty acids due to its stable and reliable composition. In the present study, the Crypthecodinium cohnii growth and docosahexaenoic acid (DHA, 22:6ω3) production in a 100 L glucose‐fed batch fermentation was evaluated. The lipid compounds were extracted by supercritical carbon dioxide (SC‐CO2) from C. cohnii CCMP 316 biomas, was and their fatty acid composition was analysed. Supercritical fluid extraction runs were performed at temperatures of 313 and 323 K and pressures of 20.0, 25.0 and 30.0 MPa. The optimum extraction conditions were found to be 30.0 MPa and 323 K. Under those conditions, almost 50% of the total oil contained in the raw material was extracted after 3 h and the DHA composition attained 72% w/w of total fatty acids. The high DHA percentage of total fatty acids obtained by SC‐CO2 suggested that this extraction method may be suitable for the production of C. cohnii value added products directed towards pharmaceutical purposes. Furthermore, the fatty acid composition of the remaining lipid fraction from the residual biomass with lower content in polyunsaturated fatty acids could be adequate for further uses as feedstock for biodiesel, contributing to the economy of the overall process suggesting an integrated biorefinery approach.

Phase equilibria of natural flavours and supercritical solvents

Abstract To study the possibility of separation of cineole from limonene (two of the main components of eucalyptus oil) we measured the vapour-liquid equilibrium of the systems containing either d-limonene or 1, 8-cineole in the supercritical solvents carbon dioxide (at 318.2 and 323.2 K) and an azeotropic mixture of ethane+carbon dioxide (at 303.2 K). The results obtained show that both solutes have similar solubilities in the supercritical solvents studied here.

Synthesis of fatty acid methyl esters via direct transesterification with methanol/carbon dioxide mixtures from spent coffee grounds feedstock

The feasibility of in situextraction and transesterification of spent coffee ground oil into fatty acid methyl esters with supercritical methanol has been investigated in the temperature range 473–603 K, and in the pressure range 10.0–30.0 MPa. At 30.0 MPa and 603 K, a fatty acid methyl esters (FAME) yield of 84.9% was obtained. Carbon dioxide was added to methanol with the aim of reducing the operating temperature and pressure. It was demonstrated that at a reaction temperature of 573 K, pressure of 10.0 MPa and a CO2/MeOH molar ratio of 0.11, a FAME yield of 93.4% was obtained.

Production of polyhydroxyalkanoates from spent coffee grounds oil obtained by supercritical fluid extraction technology

Spent coffee grounds (SCG) oil was obtained by supercritical carbon dioxide (scCO2) extraction in a pilot plant apparatus, with an oil extraction yield of 90% at a 35kgkg(-1) CO2/SCG ratio. Cupriavidus necator DSM 428 was cultivated in 2L bioreactor using extracted SCG oil as sole carbon source for production of polyhydroxyalkanoates. The culture reached a cell dry weight of 16.7gL(-1) with a polymer content of 78.4% (w/w). The volumetric polymer productivity and oil yield were 4.7gL(-1)day(-1) and 0.77gg(-1), respectively. The polymer produced was a homopolymer of 3-hydroxybutyrate with an average molecular weight of 2.34×10(5) and a polydispersity index of 1.2. The polymer exhibited brittle behaviour, with very low elongation at break (1.3%), tensile strength at break of 16MPa and Youngs Modulus of 1.0GPa. Results show that SCG can be a bioresource for polyhydroxyalkanoates production with interesting properties.

Phase equilibria of the ternary system methyl oleate/squalene/carbon dioxide at high pressure conditions

Abstract Vapor–liquid equilibrium data are reported for the ternary system methyl oleate–squalene–carbon dioxide in the temperature range of 313–343 K and in the pressure range of 11–21 MPa. Experiments were performed in a continuous-type equilibrium apparatus by using a static mixer ensemble to promote the equilibrium between the gas and liquid phases. High selectivity of carbon dioxide towards methyl oleate was obtained. Equilibrium data were correlated using the Soave–Redlich–Kwong equation of state with the Mathias–Klotz–Prausnitz mixing rule. The binary interaction parameters were optimized by minimizing the deviations between the calculated and experimentally determined vapor and liquid phase compositions and distribution coefficients of each substance. A fairly good correlation of the data could be obtained with an average absolute deviation (AAD) of 1.3×10 −2 .

Development and characterization of a thermoresponsive polysulfone membrane using an environmental friendly technology

A new and environmentally friendly technology has been used successfully to produce thermoresponsive polysulfone membranes with good performance in terms of valve mechanism in the pores, with a complete on-off control of water permeability. Membranes were prepared using a CO2-assisted phase inversion method and their pores were coated/impregnated with a thermoresponsive polymer – poly(N-isopropylacrylamide) – using a new methodology for the preparation of these type of structures. The coating/impregnation efficiency was assessed by SEM and XPS analysis that confirmed the presence of nitrogen due to the thermoresponsive hydrogel. Contact angle measurements and phosphate buffer solution permeability were determined in order to characterize the structure hydrophobicity variations with temperature. The on-off mechanism was tested using a model protein (BSA) as a proof of concept for the ability to control pore apertures by temperature stimulus. A diffusion model based on Ficks law and Langmuir adsorption was developed.

Quality assessment of refined olive oils by gas extraction

Abstract Olive oil is a vegetable oil that is extracted from olives by mechanical means. Fractions of the oil thus produced have a high content of free fatty acids and require refining. Conventional refining processes may, however, alter the nutritional qualities of the oil. In recent years, a study was carried out to evaluate the feasibility of deacidifying olive oil by supercritical carbon dioxide extraction. Extensive deacidification, resulting in low acid contents of the raffinates, was obtained. Results obtained for other quality aspects of the supercritical fluid refined oil are reported here. Raffinates were analysed to determine their overall ultraviolet absorbance, triglyceride profile by high-performance liquid chromatography and stigmasta-3,5-diene content by gas–liquid chromatography. The analyses made have shown that extraction with supercritical fluid did not alter the nutritional quality of the processed virgin olive oil.

Supported Ionic Liquid Membranes and Ion-Jelly® Membranes with [BMIM][DCA]: Comparison of Its Performance for CO2 Separation.

In this work, a supported ionic liquid membrane (SILM) was prepared by impregnating a PVDF membrane with 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]) ionic liquid. This membrane was tested for its permeability to pure gases (CO2, N2 and O2) and ideal selectivities were calculated. The SILM performance was also compared to that of Ion-Jelly® membranes, a new type of gelled membranes developed recently. It was found that the PVDF membrane presents permeabilities for pure gases similar or lower to those presented by the Ion-Jelly® membranes, but with increased ideal selectivities. This membrane presents also the highest ideal selectivity (73) for the separation of CO2 from N2 when compared with SILMs using the same PVDF support but with different ionic liquids.

Interfacial tension of edible oils in supercritical carbon dioxide

Interfacial properties essentially influence fluid-liquid separation processes. Thereby, interfacial tension is an important parameter that is associated with mass transfer and mutual solubility of participating compounds. For this reason, interfacial tension of a virgin olive oil with a known amount of free fatty acids was measured in supercritical carbon dioxide atmosphere at 313 K and 353 K and pressures up to 40 MPa. The obtained values were compared to different oils some of which contain appreciable amounts of volatile components. In general, interfacial tension behaviour is dominated by the effect of pressure, whereas differences between oil compositions are secondary. Besides mutual solubility interfacial tension is supposed to be associated with the compressibility of the dense fluid phase. For predicting mass transfer area some general comments on the colloidal behaviour of systems containing supercritical CO2 are made

Scale-up of a supercritical extraction unit for the deacidification of olive oil

Publisher Summary Olive oils with large quantities of free fatty acids must be refined to get a salable product. Deacidification is currently done by physical or chemical processes that may alter the organoleptic profile of the oil. Supercritical fluid deacidification of these oils has been suggested as a potential ecological alternative process, because it uses nontoxic solvents and low operating temperatures. The use of supercritical carbondioxide as a solvent for the deacidification of olive oils has shown the selective preference of carbon dioxide toward the free fatty acids (FFA) fraction and at the same time retaining the nutritional constituents of the oil. This chapter reviews a study carried out to evaluate the best operational conditions for the deacidification of olive oils by supercritical extraction (SCE) and to evaluate the design of an extraction unit. To assess the feasibility of the olive oil deacidification plant, an economical study that is described in the chapter was performed by simulating all the debits and credits involved in the industrial plant. The analysis was performed at constant prices instead of real prices and the units are in Portuguese escudos (PTE).