Presence Of Deep Eutectic Solvents Research Articles

Analysis of the Behavior of Deep Eutectic Solvents upon Addition of Water: Its Effects over a Catalytic Reaction.

This study presents the potential role of deep eutectic solvents (DESs) in a lipase-catalyzed hydrolysis reaction as a co-solvent in an aqueous solution given by a phosphate buffer. Ammonium salts, such as choline chloride, were paired with hydrogen bond donors, such as urea, 1,2,3-propanetriol, and 1,2 propanediol. The hydrolysis of p-nitrophenyl laureate was carried out with the lipase Candida antarctica Lipase B (CALB) as a reaction model to evaluate the solvent effect and tested in different DES/buffer phosphate mixtures at different % w/w. The results showed that two mixtures of different DES at 25 % w/w were the most promising solvents, as this percentage enhanced the activities of CALB, as evidenced by its higher catalytic efficiency (kcatKM). The solvent analysis shows that the enzymatic reaction requires a reaction media rich in water molecules to enable hydrogen-bond formation from the reaction media toward the enzymatic reaction, suggesting a better interaction between the substrate and the enzyme-active site. This interaction could be attributed to high degrees of freedom influencing the enzyme conformation given by the reaction media, suggesting that CALB acquires a more restrictive structure in the presence of DES or the stabilized network given by the hydrogen bond from water molecules in the mixture improves the enzymatic activity, conferring conformational stability by solvent effects. This study offers a promising approach for applications and further perspectives on genuinely green industrial solvents.

Unraveling the Role of Deep Eutectic Solvents with Varying Hydrogen-Bond Acceptors on the Thermoresponsive Polymer Poly(N-isopropylacrylamide).

Deep eutectic solvents (DESs) have emerged as promising tools for crafting polymeric materials across diverse domains. This study delves into the impact of a series of DESs on the phase behavior of poly(N-isopropylacrylamide) (PNIPAM) in aqueous environments, presenting compelling insights into their performance. Specifically, we explore the conformational phase behavior of PNIPAM in the presence of four distinct lactic acid (LA)-based DESs: LA-betaine (LA-BET), LA-proline (LA-PRO), LA-choline chloride (LA-CC), and LA-urea (LA-U). By maintaining a consistent hydrogen-bond donor (HBD) while varying the hydrogen-bond acceptor (HBA), we unravel how different DES compositions modulate the phase transition behavior of PNIPAM. Our findings underscore the profound influence of DESs comprising LA as the HBD and diverse HBAs-BET, PRO, CC, and U on the thermoresponsive behavior of PNIPAM. Employing spectroscopic techniques such as ultraviolet-visible (UV-vis) spectroscopy, steady-state fluorescence, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), ζ-potential, and transmission electron microscopy (TEM), we elucidate the preferential interactions between the HBA groups within DESs and the hydration layer of PNIPAM. Notably, temperature-dependent DLS analyses reveal a discernible decrease in the lower critical solution temperature (LCST) of PNIPAM with increasing DES concentration, ultimately disrupting the hydrogen-bond interactions and resulting in early hydrophobic collapse of the polymer, which can be clearly seen in the TEM micrographs. Furthermore, the formation of polymer composites within the mixed system leads to notable alterations in the physiochemical properties of PNIPAM, as evidenced by shifts in its LCST value in the presence of DESs. This perturbation disrupts hydrogen-bond interactions, inducing hydrophobic collapse of the polymers, a phenomenon vividly captured in TEM micrographs. In essence, our study sheds new light on the pivotal role of varying HBA groups within DESs in modulating the conformational transitions of PNIPAM. These insights not only enrich our fundamental understanding but also hold immense promise for the development of smart polymeric systems with multifaceted applications spanning bioimaging, biomedical science, polymer science, and beyond.

Measurements of Surfactant Adsorption on Sandstone in the Presence of Deep Eutectic Solvents

Measurements of Surfactant Adsorption on Sandstone in the Presence of Deep Eutectic Solvents

Local and cooperative structural transitions of double-stranded DNA in choline-based deep eutectic solvents

The possibility of using deep eutectic solvents (DESs) as co-solvents for stabilizing and preserving the native structure of DNA provides an attractive opportunity in the field of DNA biotechnology. The rationale of this work is a systematic investigation of the effect of hydrated choline-based DES on the structural stability of a 30-base-pair double-stranded DNA model via a combination of spectroscopic experiments and MD simulations. UV absorption and CD experiments provide evidence of a significant contribution of DESs to the stabilization of the double-stranded canonical (B-form) DNA structure. Multi-wavelength synchrotron UV Resonance Raman (UVRR) measurements indicate that the hydration shell of adenine-thymine pairs is strongly perturbed in the presence of DESs and that the preferential interaction between H-bond sites of guanine residues and DESs is significantly involved in the stabilization of the dsDNA. Finally, MD calculations show that the minor groove of DNA is significantly selective for the choline part of the investigated DESs compared to the major groove. This finding is likely to have a significant impact not only in terms of thermal stability but also in the modulation of ligand-DNA interactions.

Investigation of Babassu Mesocarp Dissolution in the Presence of Deep Eutectic Solvents

Investigation of Babassu Mesocarp Dissolution in the Presence of Deep Eutectic Solvents

Understanding the intricacy of protein in hydrated deep eutectic solvent: Solvation dynamics, conformational fluctuation dynamics, and stability

Deep eutectic solvents (DESs) are potential biocatalytic media due to their easy preparation, fine-tuneability, biocompatibility, and most importantly, due to their ability to keep protein stable and active. However, there are many unanswered questions and gaps in our knowledge about how proteins behave in these alternate media. Herein, we investigated solvation dynamics, conformational fluctuation dynamics, and stability of human serum albumin (HSA) in 0.5 Acetamide/0.3 Urea/0.2 Sorbitol (0.5Ac/0.3Ur/0.2Sor) DES of varying concentrations to understand the intricacy of protein behaviour in DES. Our result revealed a gradual decrease in the side-chain flexibility and thermal stability of HSA beyond 30 % DES. On the other hand, the associated water dynamics around domain-I of HSA decelerate only marginally with increasing DES content, although viscosity rises considerably. We propose that even though macroscopic solvent properties are altered, a protein feels only an aqueous type of environment in the presence of DES. This is probably the first experimental study to delineate the role of the associated water structure of the enzyme for maintaining its stability inside DES. Although considerable effort is necessary to generalize such claims, it might serve as the basis for understanding why proteins remain stable and active in DES.

Mesoporous cobalt oxide nanoparticles synthesized by a sonochemical method in the presence of a deep eutectic solvent for oxidative sonophotocatalytic decomposition of caffeine

Herein, for the first time, we have prepared mesoporous Co3O4 nanoparticles (NPs) by the ultrasound-assisted method in the presence of deep eutectic solvent (DES) for sonophotocatalytic degradation of caffeine (CAF). The porosity, crystallinity, and morphology of the as-synthesized NPs were investigated by using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The as-prepared NPs were applied in sonophotocatalytic, photocatalytic, and sonocatalytic degradation of CAF in low energy and low-frequency ultrasound at neutral pH. The sonophotocatalytic process was the most effective in degrading CAF, reaching about 99.5 % in less than an hour with a pseudo-first-order rate constant of 0.0902 min−1. The photocatalytic and sonocatalytic processes degraded 83.4 % and 22.7 % of CAF, respectively, with lower rate constants of 0.0288 and 0.0049 min−1. Notably, the simultaneous application of UV light and ultrasound irradiation in a sonophotocatalytic decomposition process had a positive synergy effect of about 62.64 %. The commercial tablet was degraded by the optimum sonophotocatalytic process to prove the applicability of the catalyst. The reusability test of the NPs was examined, and after four consecutive uses, the NPs had negligible fading of their sonophotocatalytic performance. Due to the excellent sonophotocatalytic performance of the NPs, it is a suitable candidate for a broad range of environmental and remediation applications.

One-pot synthesis of polyhydroquinoline-1,2,3-triazole hybrids in deep eutectic solvent as anti-leishmanial agents and molecular modeling studies

The novel hybrids with 1,2,3-triazole and polyhydroquinoline scaffolds were successfully synthesized by multicomponent reaction of propargyloxybenzaldehyde, 1,3-cyclohexadione, ethylacetoacetate and ammonium acetate followed through click reaction in the presence of deep eutectic solvent ChCl/ZnCl2 as an efficient catalyst. Their anti-leishmanial activity was evaluated against amastigote and promastigote forms of L. tropica, L. major, and two different species of L. infantum. Furthermore, to determine the cytotoxicity of the hybrids, they were evaluated against the murine macrophage cell line J774.A1. Based on the results, three hybrids showed the highest antileishmanial activity. However, they revealed low cytotoxicity. Hybrid 6j was the most potent compound against both the forms of all leishmanial types, with IC50 = 13.5 and 11.9 µg/mL for L. major, 37.5 and 25 µg/mL for L. tropica, 17.5 and 20 µg/mL for L. infantum (MCAN/IR//96/LON49) and 35.5 and 30 µg/mL for L. infantum (MCAN/ES/98/LIM-877), respectively. Finally, molecular docking and molecular dynamics simulations were also performed to identify possible mechanism antileishmanial activity. Communicated by Ramaswamy H. Sarma

Analysis of Fe2+ and Mn2+ ions in DES and water: A theoretical study using molecular dynamic simulations, QTAIM and NCI-RDG

This work was essential to analyze the behavior of Fe2+ and Mn2+ ions in water and deep eutectic solvent (DES) based on choline chloride and ethylene glycol (1ChCl:2EG (choline chloride and ethylene glycol, DES)) to evaluate the electrodeposition of metallic ions. Due to their low toxicity, high solubility, biodegradability and thermal stability, DES have shown promise as alternatives to traditional solvents such as water in various applications, including biological studies. They also dissolve insoluble substances in other types of solvents, working from the purification of chemicals to the manufacture of semiconductor devices. Water, choline and ethylene glycol molecules were optimized by Density Functional Theory (DFT) through B3LYP/6–311 +G(d,p) model implemented with the Gaussian 09 W software. Molecular Dynamics (MD) simulations were performed by GROMACS software 2020.04 in a cubic box of dimensions 8 nm × 8 nm × 8 nm. Quantum Theory of Atoms in Molecules (QTAIM) and analysis of Non-covalent Interactions (NCI) used Multiwfn 3.8 software. The preliminary results of MD simulations showed that gradually adding water increased the interaction between the metal center and water. Fe2+ and Mn2+ ions were placed in water (OW) and 1ClCh:2EG, indicating that the interaction between the cations and the chloride anion in DES was strong, followed by the ethylene glycol molecules (O1, O2). In the presence of water, however, Fe-OW and Mn-OW interactions were more substantial in all systems, either with the ions alone or in a mixture. Electrostatic forces acting on the electrons in the last filled layer of the iron atom provided the formation of shorter and stronger bonds than the Mn2+ ions. When placed in a 1:1 equimolar mixture, they showed little difference from when they were isolated. Thus, the Mn-Cl interaction was more significant in the presence of a eutectic solvent than the Fe-Cl interaction. QTAIM analysis showed for the FeDES and MnDES systems that the Electron Localization Function (ELF) values increased for the Fe-(O1, O2) and Mn-(O1, O2) interactions but decreased for the Fe-Cl and Mn-Cl interactions in the metal mixture. It revealed strong hydrogen bonding interactions between the water molecules, Fe2+ and Mn2+, which may affect their chemical reactivity, as the Fe-Cl interaction in DES was stronger than Fe-Cl in any water. The Laplacians of the electronic densities were positive, and so were the ELF values, indicating a predominance of non-covalent interactions of the van der Waals forces type. Considering the two metal ions alone, in the presence of DES, the interaction strength followed Fe-Cl > Mn-Cl > Fe-(O1, O2) > Mn-(O1, O2). In the mixture, Fe-Mn followed the pattern Mn-Cl > Fe-Cl > Fe-(O1, O2) > Mn-(O1, O2). Thus, comparing the 3 systems, the interaction strength was Fe-Cl > Mn-Cl > Mn-Clmixture > Fe-Cl mixture e Fe-(O1, O2) mixture > Fe-(O1, O2) > Mn-(O1, O2)mixture > Mn-(O1, O2). The interaction strength for the systems with water was Fe-Clmixture > Fe-Cl > Mn-Cl > Mn-Clmixture. However, for the interaction with OW, the observed behaviors were: W300, Mn-OW > Fe-OWmixture > Mn-OWmixture > Fe-OWmixture; W600, Mn-OWmixture > Fe-OWmixture > Mn-OW > Fe-OW; W900, Mn-OW > Fe-OW > Mn-OWmixture > Fe-OWmixture; W1200, Mn-OW > Mn-OWmixture > Fe-OWmixture > Fe-OWmixture; W5580, Mn-OW > Fe-OW > Mn-OWmixture > Fe-OWmixture. The mixtures in the 1:1 molar ratio of the cations presented a little discrepant from their isolated ions, suggesting a new approach to observing the behavior of these systems and the coordination possibilities. One of the prospects for expanding the study will be temperature variation, modification of metal ions and molar proportions, and the effects of these changes.

Synergistic effect of dual hydrogen-donor deep eutectic solvent for performance improvement of fracturing-oil expulsion fluids

Petroleum remains the main source of energy consumption over the past decade. The development of rich unconventional oil reservoirs is a huge challenge. Clean fracturing fluids (CFFs) have gained considerable attention for the unconventional reservoir development, owing to their integrated capabilities of fracturing and oil expulsion. Performance of CFFs is a vital factor in enhancing oil recovery. In this work, a ternary deep eutectic solvent (DES) with dual hydrogen donors (HBDs) was developed as a novel and green medium for improving CFF performance. With the hydrogen-bonding interactions, the ternary DES enable a robust micelle network, thereby strengthening the rheological property, temperature resistance and drag reduction performance of CFFs. The salt resistance performance was improved due to the ion–dipole interaction between HBDs and salt cations, decreasing the interactions between salt cations and surfactants. The DES also increase the imbibition efficiency from 30.7 % in 98 h to 43.7 % in 62 h. Besides, the gel breaking performance and reusability of gel-breaking fluid were enhanced in the presence of DES. The ternary DES showed more effective reinforcement for CFF properties as compared with binary DES, due to the synergistic effect of dual HBDs. This work will provide a promising alternative for intensifying CFF performance.

Enzymatic hydrolysis for the removal of 3- monochloropropanediol esters in edible oils using Candida rugosa lipase in the presence of deep eutectic solvents and nanocellulose

3-monochloropropanediol ester (3-MCPDE) is identified as a food-borne contaminant in edible oils and are classified as a possible carcinogen. This study reports an efficient enzymatic technique for the removal of 3-MCPDE from extra virgin olive oil (EVO) using Candida rugosa lipase (CRL) as the biocatalyst in the presence of choline chloride and fructose-based natural deep eutectic solvent (NADES) and nanocellulose (NC) extracted from almond shells. The validity of the method was confirmed by gas chromatography mass spectrometry (GC-MS) showing adequate precision with relative standard deviation values ≤ 2.37%. The quantification and detection limit are within the permissible levels of 3-MCPD in edible oils. Under optimized conditions of 30 min at 90 °C with 60 µL of phenylboronic acid (PBA), the enzymatic hydrolysis resulted in the removal of 79.8% of spiked 3-MCPD in EVO. No adverse effects of the EVO were detected from this technique with respect to the oil quality testing. The application of DESs and NCs as the support material for the CRL biocatalyst for the removal of 3-MCPDE has yet to be explored. This could have a significant impact on the edible oil industry for producing oils of higher quality free from 3-MCPDE.

A Bird's‐Eye View on Deep Eutectic Solvent‐Mediated Multicomponent Synthesis of N‐Heterocycles

AbstractMulticomponent reactions are crucial for operating organic synthesis. In today's world, chemists concentrate on greener methodologies that cater to rising environmental concerns. Most conventional organic solvents are harsh on the environment, which can be addressed by environmentally and pocket‐friendly Deep eutectic solvents (DES). Organic synthesis via MCR in the presence of DES has resulted in the blend of green methodology and green solvent for organic transformations. Forasmuch as addressing the environmental concerns and developing higher heterocycles, our review focuses on the literature published on the DES‐mediated Multicomponent synthesis of N‐Heterocyclic compounds.

Tyrosinase Magnetic Cross-Linked Enzyme Aggregates: Biocatalytic Study in Deep Eutectic Solvent Aqueous Solutions.

In the field of biocatalysis, the implementation of sustainable processes such as enzyme immobilization or employment of environmentally friendly solvents, like Deep Eutectic Solvents (DESs) are of paramount importance. In this work, tyrosinase was extracted from fresh mushrooms and used in a carrier-free immobilization towards the preparation of both non-magnetic and magnetic cross-linked enzyme aggregates (CLEAs). The prepared biocatalyst was characterized and the biocatalytic and structural traits of free tyrosinase and tyrosinase magnetic CLEAs (mCLEAs) were evaluated in numerous DES aqueous solutions. The results showed that the nature and the concentration of the DESs used as co-solvents significantly affected the catalytic activity and stability of tyrosinase, while the immobilization enhanced the activity of the enzyme in comparison with the non-immobilized enzyme up to 3.6-fold. The biocatalyst retained the 100% of its initial activity after storage at -20 °C for 1 year and the 90% of its activity after 5 repeated cycles. Tyrosinase mCLEAs were further applied in the homogeneous modification of chitosan with caffeic acid in the presence of DES. The biocatalyst demonstrated great ability in the functionalization of chitosan with caffeic acid in the presence of 10% v/v DES [Bet:Gly (1:3)], enhancing the antioxidant activity of the films.

The attenuating ability of deep eutectic solvents towards the carboxylated multiwalled carbon nanotubes induced denatured β-lactoglobulin structure.

The stabilization of proteins has been a major challenge for their practical utilization in industrial applications. Proteins can easily lose their native conformation in the presence of denaturants, which unfolds the protein structure. Since the introduction of deep eutectic solvents (DESs), there are numerous studies in which DESs act as promising co-solvents that are biocompatible with biomolecules. DESs have emerged as sustainable biocatalytic media and an alternative to conventional organic solvents and ionic liquids (ILs). However, the superiority of DESs over the deleterious influence of denaturants on proteins is often neglected. To address this, we present the counteracting ability of biocompatible DESs, namely, choline chloride-glycerol (DES-1) and choline chloride-urea (DES-2), against the structural changes induced in β-lactoglobulin (Blg) by carboxylated multiwalled carbon nanotubes (CA-MWCNTs). The work is substantiated with various spectroscopic and thermal studies. The spectroscopic results revealed that the fluorescence emission intensity enhances for the protein in DESs. Contrary to this, the emission intensity extremely quenches in the presence of CA-MWCNTs. However, in the mixture of DESs and CA-MWCNTs, there was a slight increase in the fluorescence intensity. Circular dichroism spectral studies reflect the reappearance of the native band that was lost in the presence of CA-MWCNTs, which is a good indicator of the counteraction ability of DESs. Further, thermal fluorescence studies showed that the protein exhibited extremely great thermal stability in both DESs as well as in the mixture of DES-CA-MWCNTs compared to the protein in buffer. This study is also supported by dynamic light scattering and zeta potential measurements; the results reveal that DESs were successfully able to maintain the protein structure. The addition of CA-MWCNTs results in complex formation with the protein, which is indicated by the increased hydrodynamic size of the protein. The presence of DESs in the mixture of CA-MWCNTs and DESs was quite successful in eliminating the negative impact of CA-MWCNTs on protein structural alteration. DES-1 proved to be superior to DES-2 over counteraction against CA-MWCNTs and maintained the native conformation of the protein. Overall, both DESs act as recoiling media for both native and unfolded (denatured by CA-MWCNTs) Blg structures. Both the DESs can be described as potential co-solvents for Blg with increased structural and thermal stability of the protein. To the best of our knowledge, this study for the first time has demonstrated the role of choline-based DESs in the mixture with CA-MWCNTs in the structural transition of Blg. The DESs in the mixture successfully enhance the stability of the protein by reducing the perturbation caused by CA-MWCNTs and then amplifying the advantages of the DESs present in the mixture. Overall, these results might find implications for understanding the role of DES-CA-MWCNT mixtures in protein folding/unfolding and pave a new direction for the development of eco-friendly protein-protective solvents.

Особенности применения методов определения общего содержания биологически активных веществ (полифенолов и флавоноидов, общей антиоксидантной активности) в присутствии глубоких эвтектических растворителей

Deep eutectic solvents (DES) are biologically safe solvents containing donors and acceptors of hydrogen bonds.They are considered promising alternative solvents used in the extraction of biologically active substances from plants.To characterize extracts, spectrophotometric methods based on various complexation reactions are used, such as quantitative determination of the total content of flavonoids, polyphenols, determination of the total antioxidant activity. However, the articles indicate calibration characteristics for aqueous or ethanol solutions of standard substances, and no calibration dependencies were found in the DES medium. The question of the validity of the application of calibration characteristics using ethanol solutions for DES remains open. Therefore, the aim of our work was to assess the effect of the presence of deep eutectic solvents on the applicability of methods for determining polyphenols, flavonoids and total antioxidant activity. In the course of the work, calibration dependences were obtained in the medium of deep eutectic solvents based on choline chloride and malonic, malic, citric and tartaric acids. It has been established that the nature of the solvent strongly influences the calibration coefficients, which indicates the need to use separate graduations for each type of solvent.

PERFORMANCE EVALUATION OF TETRABUTYLAMMONIUM BROMIDE-BASED DEEP EUTECTIC SOLVENTS IN ENHANCED OIL RECOVERY OF NIGERIAN HEAVY OIL

Deep eutectic solvent (DES) is used as a green solvent in science due to its benefits over ionic liquids, such as biocompatibility and biodegradability, chemical stability with water, ease of preparation, and non-toxicity.DES 1 was successfully synthesized in a 1:2 molar ratio of Tetrabutylammonium bromide (TBAB) and polyethylene glycol 400 (PEG 400), while the novel DES 2 and DES 3 were synthesized in a 1:6 molar ratio of TBAB/ dimethyl sulfoxide (DMSO), and TBAB/N,N-dimethyl formamide (DMF) respectively. The performance(s) of the three DESs in the enhancement of heavy Nigerian crude oil recovery at ambient temperature was investigated. DES 1 recovered additional 16.07 % oil from core flooding using Berea sandstone core sample, resulting in an overall recovery of 53.44 %. DES 1 also resulted in an incremental recovery of 35.94 % from Niger-Delta sandstone, with a high ultimate recovery of 85.94 %. The presence of DES 2 and DES 3 were also shown to result in additional oil recovery. A drastic IFT reduction from 5.19 to 2.46mN/m was observed between the oil and the DES2 phase. Thus the study confirms that the presence of TBAB-based DES promotes reduction in the viscosity of the heavy oil and results in more oil recovery. Keywords: Deep eutectic solvents (DES), enhanced oil recovery, interfacial tension, tetrabutylammoniumbromide (TBAB)

Deep eutectic solvents as modulator on the micellization behaviour of cationic surfactants and potential application in human serum albumin aggregation

Deep eutectic solvents (DESs) have been utilized in many important applications in interdisciplinary research areas including the investigation of self-assembly of surfactants. In present study, the micellization behaviour of two conventional cationic surfactants i.e., tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) are investigated in aqueous DESs solutions with the help of surface tension, conductivity, UV–vis spectroscopy, fluorescence and dynamic light scattering (DLS) techniques. The synthesis of the DESs is done by simply mixing of choline chloride (ChCl) and urea/ethylene glycol (EG) in 1 : 2 mol ratio at 353 K temperatureand it is characterized by using FTIR technique. Various interfacial parameters and thermodynamic properties are evaluated by using tensiometric and conductometric methods. A noteworthy decrease in the critical micelle concentration (CMC) and increase in the aggregation number (Nagg) are observed in presence of DESs. Thus signifying that the micellization process of the surfactants is much favored in the DESs solutions and these are further supported by DLS results. DLS results show an increase in the micellar size for all the micellar systems in aqueous DESs solutions. More importantly, the micellar systems of the cationic surfactants within DESs solutions were also utilized for the study of their interaction with human serum albumin (HSA) to see how this albumin protein is behaving within the cationic micellar solutions in presence of DESs. UV–vis spectroscopic evidences show attractive results. It is noteworthy that the albumin protein HSA shows stronger binding affinity towards the DES-surfactants systems. The present work may further enhance the potential application of these neoteric green solvent systems composed of water-surfactant-DESs in the field of colloids, protein biophysics, nanoscience, which in turn will be highly applicable in the fields of synthesis, catalysis, and pharmaceutics etc.

Structural studies of Myceliophthora Thermophila Laccase in the presence of deep eutectic solvents

In this work, we elucidated the interactions between Myceliophthora thermophila laccase and deep eutectic solvent (DES) by crystallographic and kinetics analyses. Four types of DESs with different hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD), including lactic acid: betaine, glycerol: choline chloride, lactic acid: choline chloride and glycerol: betaine was used. The results revealed that different DES have different effects on laccase activity. Lactic acid-betaine (2:1) DES has shown to enhance laccase activity up to 300 % at a concentration ranged from 2% to 8% v/v, while glycerol: choline chloride and lactic acid: choline chloride DES choline chloride-based DES have found to possess inhibitory effects on laccase under the same concentration range. Detailed kinetic study showed that glycerol: choline chloride DES is a S-parabolic-I-parabolic mixed non-competitive inhibitor, where conformational changes can occur. The crystal structures of laccase with lactic acid: choline chloride DES (LCDES) were obtained at 1.6 Å. Crystallographic analysis suggested that the addition of LCDES causes changes in the laccase active site, but the increase in water molecules observed in the resulting crystal prevented laccase from experiencing drastic structural change. Fluorescence and circular dichroism spectroscopies were also applied to determine the effects of DES on the structural conformation of laccase. The results have confirmed that the presence of DES can trigger changes in the local environments of the amino acids in the active site of laccase which contributes to the changes in its activity and stability.

Production of biodiesel through nanocatalytic transesterification of extracted oils from halophytic safflower and salicornia plants in the presence of deep eutectic solvents

In this work, biodiesel production through transesterification of extracted oil from the halophytic salicornia persica and safflower plants in the vicinity of calcium oxide catalyst are investigated. In this direction, to solve the main problems of calcium oxide catalyst, which includes inactivation of the catalyst in the presence of moisture and carbon dioxide and leaching of catalyst particles, deep eutectic solvents (DESs) and supported catalyst have been used. Response surface methodology (RSM) was used to optimize the important parameters (M/O molar ratio, ωCat, ωDES and reaction time). The optimum values for these parameters were 12, 9%, 14% and 3 h, respectively. In this condition, the reaction efficiency was 97.01. Effect of different deep eutectic solvents (ChCl:Ac, ChCl:U, ChCl:EG, ChCl:Gly, ChCl:TU, ChCl:1,2-PDO) were investigated on the reaction of safflower and S. persica oils with methanol in the presence of calcium oxide catalyst. The maximum yield for 95% S. persica oil was obtained using ChCl:EG solvent. To improve the biodiesel production, different catalysts (CCaO, SCaO, CCaO/Na-ZSM5 and SCaO/Na-ZSM5) were activated with ChCl/EG and used in transesterification reaction under optimum conditions. The obtained results showed S. persica oil was converted to biodiesel with 98.1% efficiency in the presence CaO/Na-ZSM5. The presented eco-friendly process is very important for minimizing the freshwater consumption and achieving a green and economical way with the ability to industrialize the biodiesel production.

Mechanochemical and thermal succinylation of softwood sawdust in presence of deep eutectic solvent to produce lignin-containing wood nanofibers

In this study, the effect of the deep eutectic solvent (DES) based on triethylmethylammonium chloride and imidazole on the mechanochemical succinylation of sawdust was investigated. The sawdust was ball milled in the presence of succinic anhydride and the effects of different amounts of the DES on the carboxylic acid content and particle size were studied with and without post-heating. The carboxylic acid content significantly increased with the addition of the DES and by using 1.5 mass excess of the DES compared to sawdust; milled sawdust with 3.5 mmol/g of carboxylic acid groups was obtained using 60 min post-heating at 100 °C. The particle size was found to depend strongly on DES-to-wood ratio and a change in size-reduction characteristics was observed related to fiber saturation point. After mechanochemical milling, three succinylated sawdust samples with different carboxylic acid contents were disintegrated into wood nanofibers and self-standing films were produced. Although the mechanical properties of the films were lower than the cellulose nanofibers, they were higher or in line with oil- and biobased polymers such as polypropene and polylactic acid, respectively. Because of their amphiphilic nature, wood nanofibers were found to be effective stabilizers of water–oil emulsions.