Supercritical Technology Research Articles

Evaluation of Bioactive Compounds and Antioxidant and Cytotoxic Effects of Oil and Pulp without Açaí Fat (Euterpe oleracea) Obtained by Supercritical Extraction.

For bioactivity studies, it is necessary to use products with a high degree of purity, which may influence the cytotoxic effects. Supercritical technology presents itself as an alternative to obtain these products. Therefore, the objective of this work was to obtain the bioactive compounds of oil and pulp of açaí fat-free supercritical technology and evaluate the cytotoxicity of products in MRC-5 and VERO cells in vitro. The açaí pulp was subjected to extraction with supercritical CO2 to obtain the oil and pulp without fat, under conditions of 323.15 K at 35 MPa, 333.15 K at 42 MPa, and 343.15 K at 49 MPa. The largest yields (51.74%), carotenoids (277.09 µg/g), DPPH (2.55 μmol TE/g), ABTS (2.60 μmol TE/g), and FRAP (15.25 μm of SF/g) of oil and ABTS (644.23 μmol TE/g) of pulp without fat were found in the condition 343.15 K at 49 MPa. The highest levels of compounds phenolics (150.20 mg GAE/g), DPPH (414.99 μmol TE/g), and FRAP (746.2 μm SF/g) of the pulp without fat were found in the condition of 323.15 K to 35 MPa. The fat-free pulp presented high levels of anthocyanins without significant variation in cytotoxicity. The developed process was efficient in obtaining oil rich in carotenoids, and the supercritical technology elucidated an efficient way to obtain açaí fat-free pulp.

Supercritical Technology as an Efficient Alternative to Cold Pressing for Avocado Oil: A Comparative Approach.

Avocado oil is rich in nutrients beneficial to human health, such as monounsaturated fatty acids, phenolic compounds, tocopherol, and carotenoids, with numerous possibilities for application in industry. This review explores, through a comparative approach, the effectiveness of the supercritical oil extraction process as an alternative to the conventional cold-pressing method, evaluating the differences in the extraction process steps through the effect of temperature and operating pressure on bioactive quality and oil yield. The results reveal that supercritical avocado oil has a yield like that of mechanical cold pressing and superior functional and bioactive quality, especially in relation to α-tocopherol and carotenoids. For better use and efficiency of the supercritical technology, the maturation stage, moisture content, fruit variety, and collection period stand out as essential factors to be observed during pre-treatment, as they directly impact oil yield and nutrient concentration. In addition, the use of supercritical technology enables the full use of the fruit, significantly reducing waste, and adds value to the agro-industrial residues of the process. It produces an edible oil free of impurities, microorganisms, and organic solvents. It is a green, environmentally friendly technology with long-term environmental and economic advantages and an interesting alternative in the avocado market.

Streamlining Skin Regeneration: A Ready-To-Use Silk Bilayer Wound Dressing.

Silk proteins have been highlighted in the past decade for tissue engineering (TE) and skin regeneration due to their biocompatibility, biodegradability, and exceptional mechanical properties. While silk fibroin (SF) has high structural and mechanical stability with high potential as an external protective layer, traditionally discarded sericin (SS) has shown great potential as a natural-based hydrogel, promoting cell-cell interactions, making it an ideal material for direct wound contact. In this context, the present study proposes a new wound dressing approach by developing an SS/SF bilayer construct for full-thickness exudative wounds. The processing methodology implemented included an innovation element and the cryopreservation of the SS intrinsic secondary structure, followed by rehydration to produce a hydrogel layer, which was integrated with a salt-leached SF scaffold to produce a bilayer structure. In addition, a sterilization protocol was developed using supercritical technology (sCO2) to allow an industrial scale-up. The resulting bilayer material presented high porosity (>85%) and interconnectivity while promoting cell adhesion, proliferation, and infiltration of human dermal fibroblasts (HDFs). SS and SF exhibit distinct secondary structures, pore sizes, and swelling properties, opening new possibilities for dual-phased systems that accommodate the different needs of a wound during the healing process. The innovative SS hydrogel layer highlights the transformative potential of the proposed bilayer system for biomedical therapeutics and TE, offering insights into novel wound dressing fabrication.

Foaming of thermoplastic polyurethane using supercritical CO2 AND N2: Antishrinking strategy

The transformation of thermoplastic polyurethanes into polymeric foams is attracting great interest nowadays. However, this technology has some challenges that it is necessary to resolve, being one of the most important the shrinkage suffered by the polymeric foams over time. For that reason, this work explores several alternatives to mitigate this phenomenon. These alternatives are divided into two groups: on the one hand, the refoaming of the shrunken foams using supercritical CO2 and N2 was explored; on the other hand, the foaming using mixtures of supercritical CO2 and N2 as foaming agents was carried out. After experiments, it was seen that, the refoaming with N2 of shrunken foams obtained by supercritical CO2 technology can increase and keep constant the initial expansion ratio of the shrunken foams. Moreover, it was also observed that ratios of CO2/N2 between 80/20 and 60/40 can avoid the shrinking issues suffered by the polymeric foams after foaming using supercritical technology.

Supercritical Technology Applied to Food, Pharmaceutical, and Chemical Industries

Everyday life has caused consumers to feel genuine concern about the origin of the products they consume [...]

Analysis of Adaptability and Application Potential of Supercritical Multi-Source Multi-Component Thermal Fluid Technology for Offshore Heavy Oil in China

Supercritical multi-source, multi-component thermal fluid is a heavy oil thermal recovery method independently developed by China National Offshore Oil Co., Ltd (Beijing, China). It uses waste liquid at the production end of the production well as the water source, the injection medium temperature exceeds 374 °C, 22.1 MPa, and all the produced flue gas is re-injected. Compared with steam huff and puff technology, supercritical technology has the advantages of high enthalpy value, high heat utilization rate, good oil displacement effect, and being green and pollution-free. In addition, its oil–water treatment cost is low, it can realize the reuse of organic matter, it has a good cost advantage of water treatment under the background of low carbon, and it is a thermal recovery method with great application potential for offshore heavy oil. Therefore, it is necessary to carry out research on the adaptability and application potential of supercritical multi-source, multi-heat flow thermal recovery technology in the sea. Based on the laboratory one-dimensional displacement experiment, this paper reveals the mechanism of heavy oil supercritical multi-source multi-component thermal fluid displacement and the contribution of supercritical components to the displacement effect, and establishes the supercritical multi-source, multi-component thermal fluid numerical simulation characterization method. Combined with the characteristics of offshore heavy oil reserves, the main control factors affecting supercritical multi-source, multi-component thermal fluid development were established by numerical simulation and orthogonal test methods, and the adaptive screening method of offshore supercritical technology was established. The application potential of 670 million tons of offshore heavy oil reserves was evaluated and sorted, and KL 10-2 oilfield was selected as the pilot test oilfield. The results show that supercritical technology has great advantages in oil displacement and water treatment cost reduction, and the results play an important guiding significance for the development of offshore heavy oil technology system and the iteration of new technology.

Obtaining oil and fermentable sugars from olive pomace using sequential supercritical fluid extraction and enzymatic hydrolysis

Olive pomace has high economic potential and the supercritical technology for extraction produces oil with potential use in the food and biofuels industries. The remaining solid can be used to obtain fermentable sugars from the hydrolysis. The present work aims to evaluate the effect of supercritical fluid extraction (SFE) of pomace olive oil at 60 and 40 °C and 18 and 22 MPa on oil yield and composition. Furthermore, use the remaining solid of SFE to obtain fermentable sugars from enzymatic hydrolysis. Kinetic curves were obtained for SFE, with the best oil yields 19.36 ± 2.43 wt% obtained at 40 °C / 22 MPa. The antioxidant activity was better for (60 °C / 22 MPa) presenting 137.87 ± 1.04 µmol TEAC / g am. dry. The highest yield of fermentable sugar (YFS) was 41.02 ± 4.79 g defatted olive pomace (DOP) for 26 Filter Paper Unit (FPU) / 1% solid loading (CS).

Preparation of Porous Ga‐Doped TiO2 Composite Aerogel and Its Bactericidal Activity against Escherichia coli and Staphylococcus aureus

In this work, a novel strategy for preparing Ga‐doped TiO2 composite aerogel antibacterial agent through the sol–gel method and supercritical technology is demonstrated. The specific surface area of the samples is as high as 175 m2 g−1 and exhibits a 3D network structure with a multistage pore distribution. The obtained antibacterial agent combines the phototoxicity of TiO2, photo‐independent toxicity of Ga3+, and structural properties of aerogels, showing a synergistic antibacterial effect. On the one hand, TiO2 produces reactive oxygen species in the presence of light, thus destroying the structure of bacteria. On the other hand, Ga3+ competitively replaces Fe3+ and hinders the metabolic process of bacteria. Moreover, the structural properties of aerogels promote superior antimicrobial performance of antibacterial agents. Their antibacterial properties against Escherichia coli and Staphylococcus aureus bacteria are mainly investigated through the inhibition zone and natural colony counting method. In the results, it is shown that the structure and bactericidal activity of TiO2 aerogel is effectively optimized with Ga3+ doping. The maximum zone of inhibition of the composite aerogel against E. coli and S. aureus is 17.5 and 16 mm, and the bactericidal rate is as high as 98.57% and 96.60%, which exhibit outstanding bactericidal performance.

Encapsulation of Olive (Olea europaea L.) Pruning Waste Particles by Supercritical CO2 Technology.

Olive leaves (Olea europaea L.) contain a multitude of bioactive compounds such as sterols, carotenes, triterpenic alcohols and phenolic compounds. These compounds have been shown to exhibit antiviral, antioxidant, candida-growth-inhibitory, anticancer, antifungal, anti-inflammatory and antibacterial activities. In this sense, submicron particles from olive leaves with antioxidant activity were precipitated by supercritical antisolvent extraction in a previous work. Moreover, encapsulation enables the delayed release of compounds and avoids the first-step effect in medical therapies. Therefore, this work focused on encapsulation of particles with a certain antioxidant capacity from olive pruning waste using supercritical technology. A variety of experiments were carried out to test how the different operating variables (pressure, temperature and extract-polymer ratio) affect. Morphology was analyzed by SEM microscopy, obtaining encapsulates between 1 and 5 microns in size. The antioxidant capacity was determined by the DPPH assay, with most of the encapsulates having AAI values between 0.5 and 1 (moderate antioxidant capacity). An increase in polyphenol content was observed in the 1:3 ratio tests. The release of the compounds in gastric simulated medium was retarded by the polymeric encapsulation, while in intestinal fluid, the solubility was improved compared to the unencapsulated particles. Overall, the supercritical encapsulation process for the natural extract of olive pruning residues has proven to be effective in obtaining antioxidant particles with different release profiles.

Experimental and thermodynamic investigation of gemifloxacin solubility in supercritical CO2 for the production of nanoparticles

The effective use of the supercritical technology in the production of new pharmaceutical formulations with greater bioavailability requires the determination of the solubility of pharmaceutical substances in supercritical CO2 (scCO2) at different conditions. In the current work, the solubility of an antibacterial compound, Gemifloxacin, was measured at various temperatures (308 to 338 K), and pressures (120 to 300 bar). This compound has a poor solubility in scCO2 (0.02 × 10−4 to 0.67 × 10−4 mole fraction or 0.0156 to 0.5891 g.kg−1). Furthermore, some popular empirical models and three thermodynamic approaches (SRK and PR equations of state, and the regular solution model) were applied to correlate and predict the solubility of Gemifloxacin in scCO2. The regular solution model with temperature-dependent solubility parameter (mean AARD% = 2.32–4.34) and the SRK-based model (mean AARD% = 7.47), exhibited the highest accuracy in fitting the experimental data.

Simulation and Optimization: A New Direction in Supercritical Technology Based Nanomedicine.

In recent years, nanomedicines prepared using supercritical technology have garnered widespread research attention due to their inherent attributes, including structural stability, high bioavailability, and commendable safety profiles. The preparation of these nanomedicines relies upon drug solubility and mixing efficiency within supercritical fluids (SCFs). Solubility is closely intertwined with operational parameters such as temperature and pressure while mixing efficiency is influenced not only by operational conditions but also by the shape and dimensions of the nozzle. Due to the special conditions of supercriticality, these parameters are difficult to measure directly, thus presenting significant challenges for the preparation and optimization of nanomedicines. Mathematical models can, to a certain extent, prognosticate solubility, while simulation models can visualize mixing efficiency during experimental procedures, offering novel avenues for advancing supercritical nanomedicines. Consequently, within the framework of this endeavor, we embark on an extensive review encompassing the application of mathematical models, artificial intelligence (AI) methodologies, and computational fluid dynamics (CFD) techniques within the medical domain of supercritical technology. We undertake the synthesis and discourse of methodologies for calculating drug solubility in SCFs, as well as the influence of operational conditions and experimental apparatus upon the outcomes of nanomedicine preparation using supercritical technology. Through this comprehensive review, we elucidate the implementation procedures and commonly employed models of diverse methodologies, juxtaposing the merits and demerits of these models. Furthermore, we assert the dependability of employing models to compute drug solubility in SCFs and simulate the experimental processes, with the capability to serve as valuable tools for aiding and optimizing experiments, as well as providing guidance in the selection of appropriate operational conditions. This, in turn, fosters innovative avenues for the development of supercritical pharmaceuticals.

Production of Exopolysaccharide-Based Porous Structures for Biomedical Applications: A Review.

Exopolysaccharides, obtained from microorganisms as fermentation products, are interesting candidates for biomedical applications as scaffolds: they are biocompatible, nontoxic, antimicrobial, antitumor materials. To produce exopolysaccharide-based scaffolds, sol-gel technology could be used, which ends with the removal of the liquid phase from the polymeric network (i.e., the drying step). The aim of this review is to point out the most relevant strengths and weaknesses of the different drying techniques, focusing attention on the production of exopolysaccharide-based porous structures. Among these drying processes, supercritical carbon dioxide-assisted drying is the most promising strategy to obtain dried gels to use in the biomedical field: it produces highly porous and lightweight devices with outstanding surface areas and regular microstructure and nanostructure (i.e., aerogels). As a result of the analysis carried out in the present work, it emerged that supercritical technologies should be further explored and applied to the production of exopolysaccharide-based nanostructured scaffolds. Moving research towards this direction, exopolysaccharide utilization could be intensified and extended to the production of high added-value devices.

Green Sustainable Textile Supercritical Dyeing Process Using CO2 Madder (Rubia tinctorum L.) Extract

ABSTRACT Waterless or reduced water consumption dyeing methods based on supercritical technologies are of interest to fabric manufacturers. The study was aimed at developing a dyeing method for natural fibers, in particular linen and silk, by pressure supercritical impregnation using madder alizarin (R. tinctorum) coloring compound produced by supercritical extraction method as an ecological alternative to conventional dyeing methods. A comparative test of fabric dyeing using supercritical and conventional methods was also carried out. In these dyeing technologies, the pre-treatment process plays an important role in the color intensity. The tests were performed using fabrics without and with mordants, and the results were compared using the color analysis method. The colors of the dyed samples obtained in the supercritical technology are more in shades of carmine, and in the traditional method in duller reds. The proposed modern and ecological dyeing technology guarantees a good resistance to washing and light. Antibacterial activity tests were also performed using supercritical and ethanol extracts. Dyed fabrics play health-promoting and protective roles for their users. Linen fabrics showed antimicrobial activity and positive effects on the skin, which was more moisturized. Waterless technologies should be developed in conjunction with user and environmental impact studies.

Obtaining oil, fermentable sugars, and platform chemicals from Butia odorata seed using supercritical fluid extraction and subcritical water hydrolysis

Butia odorata seeds (BOS) present high economical potential because they contain oil and lignocellulosic compounds. Oil extracted by supercritical technology may have potential use in the food industry and the remaining solid from the process can be used to produce second- generation ethanol from the hydrolysis of its carbohydrates to obtain fermentable sugars. This work evaluates the processing of BOS using supercritical fluid extraction (SFE), to obtain oil, and subsequent subcritical water hydrolysis (SWH) of SFE residue (BOSR), to obtain fermentable sugars and platform chemicals. Kinetic curves at temperatures of 40 °C and 60 °C, and pressures of 18, 20, and 22 MPa were obtained for SFE using CO2 as solvent, with the best oil yield of 29.05 ± 1.42 wt% at 60 °C and 22 MPa. In the SWH, the explored conditions were 230 °C and 260 °C for temperature, 50 and 100 for solvent to feed ratio (S/F) with a constant pressure of 15 MPa. The best results for the yields of fermentable sugars and platform chemicals were 5.78 ± 1.15 g/100 g and 2.90 ± 0.24 g/100 g, respectively, at 260 °C and S/F 50.

Use of Winemaking By-Products for the Functionalization of Polylactic Acid for Biomedical Applications.

The addition of naturally active compounds to implantable polymers is an efficient strategy against inflammation issues that might lead to rejection, while promoting controlled re-endothelialization of the tissues. This work proposes the use of winemaking by-products with high active properties of biomedical interest to obtain bioactive PLA by using supercritical technologies. First, two red grape pomace extracts, obtained by high-pressure extraction with supercritical CO2 and cosolvents (either ethanol or water-ethanol), have been studied. Second, two impregnation methods have been studied with both extracts, traditional supercritical CO2-assisted impregnation (SSI) and a novel pressurized soaking method (PSI). The amount of extract impregnated as well as the bioactivity levels achieved-i.e., antioxidant, antimicrobial, and anti-inflammatory properties- have been determined for each extract and impregnation method at different pressure and temperature conditions. Both extracts obtained had good antioxidant, anti-inflammatory, and antibacterial capacities, especially the hydroethanolic one (0.50 ± 0.03 mg TE/g versus 0.24 ± 0.03 mg TE/g, respectively). Regarding impregnated filaments, impregnation loadings depended especially on the extract and P/T conditions, providing up to 8% (extract mass/polymer mass) of impregnation. The antioxidant capacity increased noteworthily by using the ethanolic extract by PSI, with values near 100 µg TE/g PLA.

Experimental and Theoretical Investigation of Supercritical Processes: Kinetics of Phase Transitions in Binary “2-Propanol—CO2” System

Studies of phase transition kinetics are important for such supercritical processes as supercritical drying, adsorption, micronization, etc. In supercritical technologies, “organic solvent—CO2” systems are often formed, the properties of which strongly depend on the system parameters. In this article, the kinetic curves of phase transitions in the “2-propanol—CO2” system were investigated experimentally and theoretically. Experimental studies were carried out in a 250 mL high-pressure apparatus at temperatures of 313 and 333 K and pressures of 6.3 and 7.8 MPa with and without the addition of alginate porous gel. Theoretical studies were carried out using the mass transfer equation, the Peng-Robinson equation of state, and the Van der Waals mixing rules, with Python being used for the calculations. The mass transfer coefficients and equilibrium concentrations of CO2 in the liquid phase were determined using the BFGS optimization method.

MnO/C/Sepiolite 3D-network aerogel as electrode material for supercapacitors

With the gradual increase of people's demand for energy, the energy crisis is becoming increasingly severe. A new and efficient energy storage device must be urgently exploited to relieve the pressure brought by the energy crisis. In this paper, MnO/C/Sepiolite aerogel nanocomposites were prepared by supercritical technology and freeze-drying technology as electrode materials for supercapacitors. The morphology of MnO/C aerogel is granular nanospheres, and the particle size of the calcined MnO/C aerogel ranges from 80 nm to 100 nm. Sepiolite with the unique fibrous structure can provide a matrix for MnO/C aerogel to form a stable 3D-network aerogel, and then lead to more active sites to be exposed. As results, the specific capacity of MnO/C/Sepiolite aerogel can reach 103.9 mAh/g, while the specific capacity of MnO/C aerogel is only 55.7 mAh/g at the current density of 1 A/g. Furthermore, the specific capacitance of MnO/C/Sepiolite aerogel can reach 507.4 F/g at the scan rate of 5 mV/s, higher than that of MnO/C aerogel (365.8 F/g). After 1400 cycles of repetitive charge/discharge measurement at 20 A/g current density, it is find that the specific capacitance retention rate of MnO/C/Sepiolite aerogel (98.57% retention) is higher than that of MnO/C aerogel (95.71% retention). Therefore, the problems of particle agglomeration of MnO/C active substances and low degree of active site exposure were effectively improved by the introduction of sepiolite.

Solubility of palbociclib in supercritical carbon dioxide from experimental measurement and Peng–Robinson equation of state

Palbociclib is a poorly water-soluble medicine which acts against metastatic breast cancer cells. Among various techniques to improve the solubility of this medicine, applying supercritical technologies to produce micro- and nano-sized particles is a possible option. For this purpose, extraction of solubility data is required. In this research, the solubility of palbociclib in supercritical carbon dioxide (ScCO2) at different equilibrium conditions was measured at temperatures between 308 and 338 K and pressures within 12–27 MPa, for the first time. The minimum and maximum solubility data were found to be 8.1 × 10–7 (at 338 K and 12 MPa) and 2.03 × 10–5 (at 338 K and 27 MPa), respectively. Thereafter, two sets of models, including ten semi-empirical equations and three Peng–Robinson (PR) based integrated models were used to correlate the experimental solubility data. Bian’s model and PR equation of state using van der Waals mixing rules (PR + vdW) showed better accuracy among the examined semi-empirical and integrated models, respectively. Furthermore, the self-consistency of the obtained data was confirmed using two distinct semi-empirical models. At last, the total and vaporization enthalpies of palbociclib solubility in ScCO2 were calculated from correlation results of semi-empirical equations and estimated to be 40.41 and 52.67 kJ/mol, respectively.

Valorization of Cereal Byproducts with Supercritical Technology: The Case of Corn

Ethanol and starch are the main products generated after the processing of corn via dry grinding and wet milling, respectively. Milling generates byproducts including stover, condensed distillers’ solubles, gluten meal, and the dried distillers’ grains with solubles (DDGS), which are sources of valuable compounds for industry including lignin, oil, protein, carotenoids, and phenolic compounds. This manuscript reviews the current research scenario on the valorization of corn milling byproducts with supercritical technology, as well as the processing strategies and the challenges of reaching economic feasibility. The main products recently studied were biodiesel, biogas, microcapsules, and extracts of enriched nutrients. The pretreatment of solid byproducts for further hydrolysis to produce sugar oligomers and bioactive peptides is another recent strategy offered by supercritical technology to process corn milling byproducts. The patents invented to transform corn milling byproducts include oil fractionation, extraction of undesirable flavors, and synthesis of structured lipids and fermentable sugars. Process intensification via the integration of milling with equipment that operates with supercritical fluids was suggested to reduce processing costs and to generate novel products.

Applications and Challenges of Supercritical Foaming Technology.

With economic development, environmental problems are becoming more and more prominent, and achieving green chemistry is an urgent task nowadays, which creates an opportunity for the development of supercritical foaming technology. The foaming agents used in supercritical foaming technology are usually supercritical carbon dioxide (ScCO2) and supercritical nitrogen (ScN2), both of which are used without environmental burden. This technology can reduce the environmental impact of polymer foam production. Although supercritical foaming technology is already in production in some fields, it has not been applied on a large scale. Here, we present a detailed analysis of the types of foaming agents currently used in supercritical foaming technology and their applications in various fields, summarizing the technological improvements that have been made to the technology. However, we have found that today's supercritical technologies still need to address some additional challenges to achieve large-scale production.