Hydrophobic Deep Eutectic Solvents Research Articles

Experiment and microscopic analysis for the separation of isopropanol‐water using hydrophobic deep eutectic solvents

AbstractIn this study, a method for separating isopropanol from wastewater using hydrophobic deep eutectic solvents (DESs) synthesized from terpenes and capric acid was proposed. The distribution coefficient and selectivity value of isopropanol (IPA) in the solvents were determined by liquid–liquid extraction experiments, and the extraction performances of the solvents at different molar ratios and temperatures were studied. From the perspective of molecular dynamics simulations, the experimental results were verified by mechanism analysis, the contribution of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) to the selective separation of isopropanol was explained. The interaction energies, radial distribution functions, normal density distribution, and mean square deviations between the atoms were used to analyze the interactions between the components of the DESs and IPA/water. It was observed that the DESs have a good extraction effect on IPA, which verifies the good application prospects of DESs in wastewater solutions containing alcohol compounds.

Removal of Propylparaben in an Aqueous System using Magnetite-Silica Ferrofluids of Hydrophobic Deep Eutectic Solvent

A novel sorbent based on ferrofluid hydrophobic deep eutectic solvent magnetite silica (Fe3O4@SiO2@mSiO2- HDES) was successfully synthesized by adding menthol-fatty acid as carrier liquid onto Fe3O4@SiO2@mSiO2 composite. The crystallinity, morphological, functional group and magnetic properties of the materials were characterized by x-ray diffraction, scanning electron microscopy-EDX, Brunauer–Emmett–Teller, vibrating sample magnetometer, thermogravimetric analysis and Fourier Transform-infrared spectroscopy. The adsorption performance of parabens was evaluated as model water pollutants. The Fe3O4@SiO2@mSiO2-HDES ferrofluid was used as a ferrofluid sorbent of parabens prior to spectrophotometry UV-Vis. The effect of several contribution parameters was optimized including ferrofluid volume, pH, stirring time and ionic strength. Under the optimum conditions, a combination of Fe3O4@SiO2@mSiO2-menthol/palmitic acid was achieved as the best ferrofluid with % removal values ranging from 81.00% to 98.62%. The ferrofluid Fe3O4@SiO2@mSiO2-HDES demonstrated high efficiency for the adsorption paraben in the water system which suggests a great potential alternative method for the adsorption of water contaminants in the aquatic system.

Green recovery of platform chemicals from hydrothermal carbonization process water

This study explores the side-recovery of platform chemicals in the hydrothermal carbonization waste-to-energy chain. Up to 90 % of target chemicals, furfural and 5-hydroxymethylfurfural, were green extracted from the process waters using the hydrophobic deep eutectic solvent decanoic acid/thymol. Wheat straw and rice husk reacted (1/4 solid/water ratio) for up to 120 min and at 180 and 230 °C. The dissolved chemicals built up to 5.9 g/L, accounting for 12 % of the total carbon. Extractions from the process waters and those from reference solutions behaved similarly. The solvent affinity toward furfural is 3.5 times higher than that of 5-hydroxymethylfurfural. The aqueous raffinates chromatographic outline demonstrated the recyclability for prosecuting the HTC. Focused experiments mimicked the functioning of an industrial cascade of two crosscurrent mixer settlers. Extraction yields were 90.7 and 65.8 % for furfural and 5-hydroxymethylfurfural. The counterflow arrangement, simulated by the Kremser method, gave corresponding higher yields, 96.9 and 73.4 %, respectively.

Simultaneous and selective extraction of different polarity bioactive substances from Ligustri Lucidi Fructus based on a designable biphasic deep eutectic solvent

Most plants contain hydrophilic and hydrophobic bioactive compounds, traditional organic solvent extraction processes can often only extract one of the components, resulting in a cumbersome process and a waste of resources. To make full use of the active resources in Ligustri Lucidi Fructus, a biphasic deep eutectic solvent (DES) system was established. By adjusting the polarity, oleanolic acid (OA) and ursolic acid (UA) were enriched in the hydrophobic phase, and flavonoids and procyanidine (PAC) in the hydrophilic phase, respectively. Established with a 1:1 vol ratio of hydrophobic DES MIA (DL-menthol: isopropyl alcohol, 1:1) and hydrophilic DES CBE (choline chloride: betaine: ethylene glycol, 1:1:2). The biphasic system had the highest extraction rate. The response surface method was used to further optimize the extraction conditions. After optimization, the extraction yields of OA and UA were 10.96 ± 0.35 mg/g and 11.67 ± 0.26 mg/g in the MIA phase, and the extracted yields of flavonoids and PAC in the CBE phase were 77.38 ± 0.62 mg/g and 5.20 ± 0.03 mg/g, respectively. Compared with the conventional single-phase extraction with organic solvents, the biphasic system provided higher extraction rate and selectivity and the extracts showed stronger antioxidant activity. Compared to the single-phase extraction utilizing conventional organic solvents, the results demonstrated significant improvement. Consequently, by adjusting the polarity of the biphasic DES system, this study supplies an argument for increasing the extraction efficiency of plant resources. This expands the application of the biphasic DES system and contributes to the high-value exploitation of natural commodities.

Efficient selective leaching of ytterbium and lutetium oxides by new hydrophobic deep eutectic solvents

This research reports the first study of selective leaching of ytterbium-lutetium oxides mixture with hydrophobic deep eutectic solvents (DESs), and high-efficiency and simple-prepared were used to separate and beneficiate lutetium. With hydrophobic DESs, which were formed with hydrophobic salicylic acid (SA) or 3,5-dinitrosalicylic acid (DNS) as the hydrogen bond donor (HBD) and hydrophobic tri-n-octyl phosphine oxide (TOPO) as the hydrogen bond acceptor (HBA), powdered eutectic mixtures of ytterbium-lutetium oxides were leached. The separation factor of ytterbium-lutetium was concluded to reached 2.11 with a solid-liquid (S/L) ratio of 1/50 g/ml, a temperature of 90 °C and a 4 h leaching time, and the experimental conditions, such as the S/L ratio, temperature and reaction time, were explored. The formation of intermolecular hydrogen bonds between the HBD and HBA was revealed through multiple methods, such as IR (disappearance of OH characteristic peaks), 1H NMR (formation of sharp peaks not present for intramolecular hydrogen bonds) and 31P NMR (shift of P = O peaks to higher fields). The lattice energies of the intermolecular hydrogen bonds and the solid oxide lattice energies, which were calculated with Gaussian 16 software (0.87 eV for SA/TOPO = 1:1 and 0.94 eV for DNA/TOPO = 1:1) and the Born–Haber cycle (12957.56 kJ/Mol for Yb2O3 and 12993.59 kJ/Mol for Lu2O3), provided a theoretical illustration of preferential Yb/Lu dissolution leading to separation. The stripping, regeneration and recycling capabilities of the DESs were investigated with stripping and recirculation experiments. Based on these results, the new DES as the leaching agent to separation of ytterbium lutetium oxide is identified as a new efficient mothed with industrialization potential.

Terpenes based hydrophobic deep eutectic solvents for dispersive liquid-liquid microextraction of aliphatic aldehydes in drinking water and alcoholic beverages

Aliphatic aldehydes are a class of organic compounds containing aldehyde groups, which are widespread, and closely related to people's daily life and health. In this work, a series of terpenes based hydrophobic deep eutectic solvents were designed and synthesized using hexafluoroisopropanol as hydrogen bond donor and menthol/thymol as hydrogen bond acceptor. Then they are used as extraction solvent in dispersive liquid-liquid microextraction for extracting and determining seven aliphatic aldehydes from drinking water and alcoholic beverage combined with high performance liquid chromatography-ultraviolet. Due to the fact that these hydrophobic deep eutectic solvents are liquid at the room temperature, a density greater than that of water, a lower viscosity (≤26.10 mPa s, 25 °C), after extraction and centrifugation, the microvolume DES-rich phase in the bottom is convenient for collection and direct analysis without further dissolution or dilution with organic solvents. Some factors affecting the extraction recovery were optimized by one-variable-at-a-time and response surface methodology. Under the optimal conditions, the enrichment factors for the seven aliphatic aldehydes were 48–56. The method had good performance: linear ranges of 1.0–200, 0.5–200, 0.2–200, 0.4–400, 1.0–400, 0.4–400 and 0.4–400 μg L−1 for seven aliphatic aldehydes (r2 ≥ 0.9949), limits of detection of 0.1–0.5 μg L−1, intra-day and inter-day precisions <4.9%. The recoveries of seven aliphatic aldehydes ranged from 76.0 to 119.0%. The proposed dispersive liquid-liquid microextraction method is simple, rapid, highly efficient, and green, which effectively reduces the amount of toxic chemical reagents used and their impact on the environment. Rapid and efficient detection of aliphatic aldehydes helps ensure a healthy diet and has great application prospects in food safety analysis.

(Deep eutectic solvent-ionic liquid)-based ferrofluid a new class of magnetic colloids for determination of tamoxifen and its metabolites in human plasma samples

In this research, a novel category of magnetic colloid was created by immobilizing an ionic liquid on the surface of silica-coated magnetic particles. This was followed by utilizing a natural hydrophobic deep eutectic solvent as a carrier. This magnetic colloid served as an adsorbent in dispersive solid-phase microextraction, combined with liquid chromatography-UV detection, for analyzing tamoxifen and its three active metabolites in plasma samples. After optimizing the effective variables in the analysis, the method underwent validation. Linearity was observed in the calibration model between 0.2 and 5.0 µg/L. The range of the detection limit was found to be 0.2–200.0 µg/L. Assessing the method's precision involved evaluating the intra- and inter-day precision at three analyte concentrations, which determined less than 7.5 % and 11.2 %, respectively. Moreover, the accuracy fell between 94.3 % and 105.1 %. The method's feasibility was evaluated using human plasma samples that ranged in concentrations of tamoxifen, N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen, respectively, from 28.3 to 39.7, 25.9–42.7, ≈1.3, and 3.4–7.2 μg L-1. Among the many benefits of this approach is the removal of the requirement for additional electronic accessories and dispersive solvents. It also minimizes the sample size, making it easily automatable. The method's applicability was demonstrated using human plasma samples, which provided quantification ranges for various tamoxifen metabolites. This technique has a lot of potential for studying the pharmacodynamics, therapeutic drug monitoring, andpharmaceutical kineticsof tamoxifen and its metabolites in bodily fluids, which will help with clinical research and drug analysis.

Natural hydrophobic deep eutectic solvent based dispersive liquid-liquid microextraction followed by liquid chromatography with tandem mass spectrometry analysis of multi-class metabolites of pesticides, phthalates, and polycyclic aromatic hydrocarbons in animal-originated foods

Demonstrated a new natural hydrophobic deep eutectic solvent (NADES) based dispersive liquid-liquid microextraction (DLLME) approach/method to extract and enrich 37 multi-class metabolites (MCM) such as pesticides, phthalates, and polycyclic aromatic hydrocarbons metabolites from a complex animal- originated food matrices. The extraction solvent (NADES) synthesized from an equimolar mixture of the terpenes, thymol and menthol. The analysis was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) employing electrospray ionization, and an enzymatic deconjugation of metabolites was carried out with β-glucuronidase. The parameters were optimized using the design of experiments (DoE). Further, the method was validated, and measurement uncertainty was also calculated. The detection and quantitation limits of the method were 0.03 to 0.4 ng/mL and 0.1 to 1.32 ng/mL, respectively. Recovery and expanded uncertainty ranged from 81.3 to 112.3 % and 8.9 to 19.7 %. The pertinence of the method was proven in identifying/finding metabolites in egg and meat samples ranging from 0.31 to 7.83 ng/g and 0.51 to 9.78 ng/mL in milk samples.

Sustainable production of nanoemulsions by membrane-assisted nanoemulsification using novel aroma-based hydrophobic deep eutectic solvents for enhanced antifungal activities

Hydrophobic deep eutectic solvents (DESs), a recent class of green solvents, offer 100% atom economy, low cost, potential biodegradability, negligible toxicity and promising bioactivities. In this work, novel aroma-based therapeutic hydrophobic DESs were prepared and dispersed in aqueous media as nanoemulsions to potentiate biomedical applications, where polar media is encountered.A reusable microengineered stainless-steel isoporous membrane was fabricated by laser drilling technique. Three hydrophobic DESs, namely DES A (menthol and vanillin), DES B (menthol and raspberry ketone), and DES C (thymol and raspberry ketone) were prepared and emulsified in aqueous media by sustainable membrane emulsification technique. The optimised nanoemulsion (DES C-in-water) exhibited a monomodal size distribution with Zavg (size average) of 147 nm and polydispersity index of 0.22.From the application perspective, the formulated DES-in-water nanoemulsions and their constituents were evaluated for their antibacterial properties against Escherichia coli and Staphylococcus aureus. Additionally, antifungal properties of the DES-based emulsions were reported for the first time by testing them against four fungal strains, Aspergillus fumigatus, Candida albicans, Candida krusei, and Trichophyton mentagrophytes. The nanoemulsions were found to be exhibit antimicrobial effect and lesser quantities of individual compounds were needed in nanoemulsified state to show similar effects. Different 1D and 2D NMR techniques were successfully used to investigate the structural orientation and the inter and intramolecular interactions in the DES and emulsion systems, which revealed a probable cause for higher antimicrobial activity of DES C-based emulsions compared to its peers. Lastly, a synergistic effect of the components in nanoemulsions led to enhanced antimicrobial activities.

Fundamental insight on how carbon chain length affects per-and polyfluoroalkyl substances adsorption onto hydrophobic deep eutectic solvents

In this study, our focus lies on hydrophobic deep eutectic solvents (HDES) as we explore their potential for the adsorption of short-chain per- and polyfluoroalkyl substances (PFAS) from water. This investigation utilizes Conductor-like Screening MOdel for Real Solvents (COSMO-RS) to fundamentally evaluate HDES for the adsorption of perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), perfluorohexanesulfonic acid (PFHxS), and perfluorohexanoic acid (PFHxA). By analyzing sigma surfaces, sigma profiles, and sigma potentials, it was observed that the PFAS compounds possess sufficiently strong nonpolar and hydrogen bond donating sites, having affinity towards hydrogen bond acceptor surfaces. According to the thermodynamic adsorption studies, short-chain PFAS exhibit higher affinity towards 5 main HBAs (trioctylphosphine oxide, tetrabutylammonium bromide, tetraoctylammonium chloride, tetraoctylammonium bromide, trihexyltetradecylphosphonium chloride) and 2 HBDs (camphor and L-arginine), with activity coefficients being as low as −13.07. Excess enthalpy analysis reveals that nonpolar interactions play a dominant role in the exchanges between HDES and PFAS compounds, suppressing hydrogen bonding interactions by an order of magnitude. TOPO: L-arginine (1:1) showed the lowest excess enthalpy of mixing for PFBS at −13.43 kJ/mol. The same HDES showed values of −10.60 kJ/mol, −15.14 kJ/mol, and −12.27 kJ/mol for PFBA, PFHxS, and PFHxA, respectively. Lastly, the best-performing solvent combinations underwent virtual models for property evaluation of chemicals within a global architecture (VEGA) analysis to assess their impact on human and environmental toxicity aspects such as mutagenicity, carcinogenicity, bioaccumulation, and acute toxicity. The outcome reveals that the best performing HDES components listed above present minimal toxicity and pose negligible environmental risks.

Novel hydrophobic acetanilide-based deep eutectic solvents. Preparation, properties, their applications in liquid–liquid extraction

Novel hydrophobic deep eutectic solvents (DESs) based on tetrabutylammonium bromide (TBAB) as a hydrogen bond acceptor and acetanilide (ACN) as a hydrogen bond donor were prepared at different TBAB:ACN molar ratios. In order to screening of molar ratios of the DES formation, TBAB and acetanilide with 1:0.12, 1:0.25, 1:0.35, 1:0.5, 1:0.75, 1:1, 1:1.25, 1:1.33, 1:1.5, 1:2, 1:2.5, 1:3, 1:4, 1:5 and 1:8 molar ratios were investigated and their stability and thermal behaviors were studied. It was found that among all the investigated mixtures five molar ratios 1:1, 1:1.25, 1:1.33, 1:1.5 and 1:2 gave stable liquids at room temperature and the DESs with molar ratios 1:1, 1:1.33 and 1:2 were selected and their physicochemical properties, thermal behaviors and applications in liquid–liquid extractions were investigated. Thermal behavior of the prepared DESs was investigated by the DSC method. The Wilson, NRTL and regular solution activity coefficient models were used for the correlation of the solid–liquid equilibria phase diagram data of the investigated systems. In order to study the chemical structure and occurrence the hydrogen bond formation between the DES constituents, the FT-IR, 1H NMR and 1C NMR analysis were carried out. The physical properties including melting point, density, speed of sound, refractive index and electrical conductivity of the prepared DESs were investigated at different temperatures. Although TBAB is soluble and acetanilide is slightly soluble in water, the prepared TBAB:ACN DESs are hydrophobic and insoluble in water, indicate the high stability in aqueous samples and they can be used for liquid–liquid extraction in aqueous samples. The prepared DESs were successfully used for efficient extraction of congo red and methyl orange from aqueous solutions. The effects of amount of DES, concentration and type of dye, sample/solvent weight ratio and HBA/HBD molar ratio on the extraction efficiency were investigated.

A new hydrophobic deep eutectic solvent composed of menthol and tris(2-ethylhexyl) phosphate for solvent bar microextraction of parabens from biological fluids

Parabens are antimicrobial preservatives with extensive applications in cosmetics, toiletries, pharmaceuticals, and food. Considering the legitimate concerns relating to their potential to disrupt multiple endocrine functions, it becomes imperative to prioritize the development of innovative bioanalytical techniques for effectively monitoring their presence in biological samples. In this study, an efficient solvent bar microextraction (SBME) was established, utilizing new hydrophobic deep eutectic solvents (DEs) to determine methylparaben and propylparaben in urine and plasma samples. The DEs comprising menthol and tris(2-ethylhexyl) phosphate (M-TEHP) at various molar ratios were synthesized for the first time to enhance the extraction capacity and promote the eco-friendliness of the DE used as an extraction solvent. Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopies were employed to confirm and investigate the properties of the successful synthesis (M-TEHP) DE at a molar ratio of 1:1. The synthesized DE exhibits low microbial toxicity and can be considered an eco-friendly solvent for extraction. Furthermore, quantum-chemical calculations were utilized to predict synthesized DE's structure and interaction energy with selected parabens. The influential operational factors of DE-SBME on the extraction efficiency (EE%) of both parabens were evaluated using response surface methodology based on central composite design, and a total of 30 extraction tests were conducted to determine the optimal conditions. The optimized DE-SBME, in combination with HPLC-DAD, exhibited low detection limits (0.54–0.91 μg L−1), excellent linearity (R2 ≥ 0.9993), precise results (RSDs ≤7.6 %), satisfactory recoveries (92–97 %) and negligible matrix effects. Hence, it had remarkable effectiveness and applicability in determining selected parabens in real urine and plasma samples.

Lignin derived hydrophobic deep eutectic solvents for the extraction of nanoplastics from water

As a growing concern in aqueous systems, micro- and nano-plastics, especially nanoplastics (NPs), have been widely detected in the environment and organisms, posing a potential threat to ecosystems and human health. Hydrophobic deep eutectic solvents (HDESs) have emerged as environmentally friendly solvents that have shown promise for extracting pollutants from water, either for detection or removal purposes. Herein, we investigated the extraction of polystyrene (PS) and polyethylene terephthalate (PET) NPs from aqueous solution using lignin based HDESs as sustainable solvents. Rapid extraction of both PET and PS NPs was observed with the high extraction efficiency achieved (> 95%). The extraction capacities for PET and PS could reach up to 525.877 mg/mL and 183.520 mg/mL, respectively, by the Thymol-2,6-dimethoxyphenol 1:2 HDES. Moreover, the extraction mechanism was studied using various techniques including Fourier-transform infrared analysis, contact angle measurements, molecular dynamics simulation, kinetics, and isotherm studies. This work lays a foundational basis for the future development of innovative HDES-based technologies in the detection and remediation of NPs as part of the grand challenge of plastic pollution.

Effective removal of personal care product residues from aqueous media using hydrophobic deep eutectic solvents: Experimental and computational approach

Personal care product (PCP) residues - classified under micropollutants (MPs)- are widely found in aquatic environments, posing trace-level toxicity. Traditional water treatment techniques struggle to remove these toxins effectively. Deep eutectic solvents (DESs), the liquid mixtures typically composed of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs), have recently emerged as a viable alternative for extracting pollutants from water. Among DESs, hydrophobic deep eutectic solvents (HDESs) exhibit low water miscibility and unique solvent properties. The main objective of this study is to synthesize HDESs to effectively eliminate 2-naphthol and methylparaben- two of the significant chemical contaminants in PCPs- from aqueous media. HDESs were prepared by mixing different terpenes (menthol and thymol) and long-chain carboxylic acids at varying molar ratios. They were characterized using different spectroscopic and thermal techniques. The density and viscosity of the pure DESs were measured as afunction of temperature. Experimental studies were carried out using the liquid–liquid extraction (LLE) method, and the factors influencing the efficiency of extraction were optimized.Considering the limited number of studies on the extraction mechanism of MPs from aqueous media, this study employs comprehensive computational methods, including density functional theory (DFT) and the COnductor-like Screening MOdel for Real Solvents (COSMO-RS), to provide a detailed interpretation of the extraction mechanism. A series of successive extractions were conducted to reduce the DES usage to ensure economic viability. The reusability of the best-performed DES was explored. Additionally, the regeneration of one of the DESs was accomplished through activated carbon-based recovery.---------------------------------------------------------------------------------------------------------------------

In situ formation of natural deep eutectic solvent on membrane after fat hydrolysis for lindane isomers determination in peanut paste

In this work a sample pretreatment approach assumed liquid-liquid microextraction based on the in situ formation of a hydrophobic natural deep eutectic solvent on a hydrophobic membrane impregnated with natural terpenoid was developed. The procedure included alkaline hydrolysis of a food sample containing fat to form fatty acids, which acted as precursors for the in situ formation of the deep eutectic solvent with natural terpenoid. Two processes were observed on the membrane surface: in situ formation of the hydrophobic deep eutectic solvent and liquid-liquid microextraction of the target analytes. After microextraction, the membrane containing the analytes was easily removed from the sample solution. The developed approach was applied to the separation and preconcentration of hydrophobic organochlorine pesticides (ɑ-hexachlorocyclohexane and γ-hexachlorocyclohexane) from a hydrophobic sample matrix (peanut paste), followed by their determination by gas chromatography with electron capture detection. Under optimal conditions, the limits of detection and quantification for both analytes were 0.3 and 1.0 μg kg−1, respectively. The procedure allowed the separation of fat-soluble analytes from a complex sample matrix with a high content of fat. The extraction recoveries were in the range of 93–95 %.

Method Development and Optimization of Liquid-Liquid Microextraction Based on the Decomposition of Deep Eutectic Solvent for the Determination of Chromium (VI) in Spinach: Assessment of the Greenness Profile Using Eco-scale, AGREE, and AGREEprep

A simple, effective, and ligandless liquid-liquid microextraction (LLME) procedure based on the decomposition of hydrophobic deep eutectic solvents (HDES) was developed for the separation and pre-concentration of chromium (VI) ions in spinach leaves, before the determination by flame atomic absorption spectrophotometry. In the proposed study, the first stage involved the leaching of chromium (VI) from spinach leaves with 0.1 M Na2CO3, and in the second stage, chromium (VI) extract was preconcentrated with the LLME procedure using a DES prepared from the combination of DL-menthol and formic acid as a chelating agent and extraction solvent. The DES decomposed in an aqueous donor phase resulting in the dispersion of menthol and extraction of Cr (VI) ions. Under optimal experimental conditions, the limits of detection (LOD) and quantification (LOQ) were 0.63 and 2.1 µg L−1, respectively. The relative standard deviation (RSD) was less than 7%, and the pre-concentration factor (PF) was found to be 31.25. The accuracy of the present methodology was tested by recovery experiments. The greenness of the developed method was assessed using three quantitative green metrics tools: Analytical Eco-scale, AGREE, and AGREEprep, with only Analytical Eco-scale qualifying the proposed method as green.

Deacetylation of Mannosylerythritol Lipids in Hydrophobic Natural Deep Eutectic Solvents

AbstractMannosylerythritol lipids (MELs) are a promising group of biosurfactants due to their high fermentation yield, selfassembly and biological activity. During fermentation by Pseudozyma aphidis, a mixture of MELs with different levels of acylation is formed, of which the fully deacetylated form is the most valuable. In order to reduce the environmental impact of deacetylation, an enzymatic process using natural deep eutectic solvents (NADES) has been developed. We tested the deacetylation of a purified MELs mixture with immobilized Candida antarctica lipase B enzyme and 2‐ethylhexanol as co‐substrate in 140 h reactions with different NADES. We identified hydrophobic NADES systems with similar yields and kinetics as in pure 2‐ethylhexanol solvent. Our results indicate that deacetylation of MELs mixtures in NADES as a solvent is possible with yields comparable to pure co‐substrate and that hydrophobic NADES without carboxylic acid compounds facilitate the reaction to the greatest extent.

Automated deep eutectic solvent-based chromatomembrane microextraction: Separation and preconcentration of bisphenols from aqueous samples

In this study, an automated, green deep eutectic solvent-based chromatomembrane microextraction approach was developed for separation and preconcentration of organic pollutants from aqueous samples. A design of a chromatomembrane cell (a polytetrafluoroethylene block coated with hydrophobic membranes) ensured automated and continuous liquid–liquid microextraction in deep eutectic solvent and separation of extract phase from aqueous sample phase. It was shown that hydrophobic deep eutectic solvents based on terpene and fatty alcohol/acid can be retained in micropores of the block and acted as a stationary phase in chromatomembrane process. Meanwhile, macropores in the block provide the penetration of aqueous phase and its movement through the block containing the liquid stationary phase (deep eutectic solvent). The large surface contact between the aqueous and deep eutectic solvent phases obtained in the block allowed to achieve on line separation (extraction recovery > 95 %) and preconcentration (enrichment factor > 10). The proposed approach was applied to microextraction of organic pollutants (bisphenols A, E and BP) from aqueous samples followed by their determination by high performance liquid chromatography with fluorometric detection. Under optimal conditions, the limits of detection for bisphenols were 0.03 µg/L. The developed microextraction sample preparation procedure is automated and compatible with liquid chromatography.

A novel strategy for extraction of intracellular poly(3-hydroxybutyrate) from engineered Pseudomonas putida using deep eutectic solvents: Comparison with traditional biobased organic solvents

Polyhydroxyalkanoates (PHAs) represent a category of microbial polyesters that offer both biodegradability and biocompatibility, if produced in sufficient quantities, they could serve as an alternative to many conventional plastics in use today. However, these microbial polymers are intracellularly stored, necessitating a more complex downstream extraction and purification process. Downstream processes often constitute the most financially burdensome stage in biomolecule production. One significant drawback of many existing extraction processes is their reliance on harsh organic solvents, such as chloroform, and high temperatures. This study presents and compares two novel downstream processes for the extraction and purification of poly(3-hydroxybutyrate) (PHB), a type of short-chain-length PHA, utilizing bio-based green solvents and natural deep eutectic solvents (NADES), respectively. The soil bacterium Pseudomonas putida, engineered to produce PHB from sugars, was adopted as a model for testing these extraction procedures. Initially, biomass was disrupted using a hypotonic buffer containing lysozyme to enhance the extraction efficiency in the downstream process. After extensive screening, the bio-based solvent ethyl acetate was selected for PHB extraction from P. putida biomass, yielding ∼ 95 wt% of the homo-polymer with a purity of ∼ 97 wt%, results comparable to those achieved with the traditional benchmark solvent, chloroform. Furthermore, a hydrophobic natural deep eutectic solvent (hydrophobic NADES) was synthesized, comprising L-menthol and acetic acid in a 1:3 M ratio, and employed as the extraction solvent in combination with methanol as the anti-solvent. The optimized extraction process resulted in a homo-polymer yield of ∼ 66 wt% with a high purity of ∼ 85 wt%. These results are promising considering the benefits associated with the use of NADES, they are less toxic and much easier to handle than ethyl acetate and have the potential to be recycled. Therefore, it represents a promising avenue for a more sustainable PHB extraction process, devoid of harmful organic solvents.

Comparison of green solvents for the revalorization of orange by-products: Carotenoid extraction and in vitro antioxidant activity

Orange peels contain a considerable number of bioactive compounds such as carotenoids, that can be used as ingredients in high-value products. The aim of this study was to compare orange peel extracts obtained with different green solvents (vegetable oils, fatty acids, and deep eutectic solvents (DES)). In addition, the chemical characterization of a new hydrophobic DES formed by octanoic acid and l-proline (C8:Pro) was performed. The extracts were compared in terms of carotenoid extraction, antioxidant activity by three methods, color, and environmental impact. The results confirmed that the mixture of C8:Pro is a DES and showed the highest carotenoid extraction (46.01 µg/g) compared to hexane (39.28 µg/g). The antioxidant activity was also the highest in C8:Pro (2438.8 µM TE/mL). Finally, two assessment models were used to evaluate the greenness and sustainability of the proposed extractions. These results demonstrated the potential use of orange peels in the circular economy and industry.