Addition Of Cosolvent Research Articles

Silica hydrogel composites as a platform for soft drug formulations and cosmetic compositions

In this work, silica hydrogels are considered as potential basis for the development of new soft drug formulations and cosmetic products. For this purpose, the hydrogel drug-silica composites having pH ∼7 were synthesized by two-step sol-gel method under different synthesis conditions (concentration of acidic catalyst, addition of co-solvent (DMSO), drug loading). Lipoamide, a powerful antioxidant, was used as the drug. Since biomedical functionality of the hydrogel materials is largely determined by their mechanical properties, response of the hydrogels to deformation under compression, tension and shear was measured, and their thixotropic behavior was also studied. The release kinetics of the drug from the hydrogel composites was investigated in vitro. It was shown that the synthesis conditions influenced significantly on the indicated properties of the synthesized hydrogels. The compression Young's moduli and the thixotropic indexes decreased with increasing catalyst concentration and drug loading due to the destabilizing effect of these factors on microstructure of the hydrogels. However, DMSO promoted improvement of the mechanical properties of the hydrogels. The tensile properties of the hydrogels were very low. It was found that the drug release from the hydrogel composites followed zero order kinetic for two days due to mechanism of anomalous diffusion. The drug release from the hydrogel composites prepared using the highest catalyst concentration and high drug loading is characterized by higher rate constants.

Development of combined therapy of metronidazole and ibuprofen using in situ microgels for the treatment of periodontitis

This study aimed to develop thermosensitive in-situ microgels loaded with the antimicrobial agent metronidazole (MTN) and the nonsteroidal anti-inflammatory drug ibuprofen (IBU) as adjunctive therapy for periodontitis. The MTN-IBU microgels were prepared by combining IBU-Microemulsions with MTN solution prepared with Pluronic® F127 (F127) hydrogel. The effect of various cosolvents and Pluronic F68 (F68) on the thermo-rheological properties (sol-gel transition temperature (Tsol→gel), viscosity, and viscoelastic properties) of MTN-IBU microgels was studied. The physicochemical properties of microgels were characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). The in vitro release and stability studies of microgels were investigated. An HPLC method was developed for the simultaneous quantification of MTN and IBU. Results showed that microgels were thermosensitive exhibiting Tsol→gel of 25–37 °C, pseudoplastic flow, and viscoelastic properties. The thermo-rheological properties of microgels were dependent on the concentration of F127, IBU-Microemulsion, cosolvents, and F68. Stability studies demonstrated that the thermo-rheological properties of microgels decreased after six months, except microgels containing F68 that were able to maintain their strength and undergo the phase transition. Microgels provided a complete MTN release after 8 h and a sustained IBU release for 24–48 h. This study highlighted the significance of in-situ microgels for delivering a combined therapy of MTN and IBU using two drug delivery systems (IBU-microemulsion and F127 sol) and the ability to modulate the thermo-rheological properties of microgels via the addition of various cosolvents and F68 to F127-based microgels as potential platforms for periodontitis.

Hydrogen bonding in ternary mixtures of N-Methyl morpholine Oxide, water and Dimethyl sulfoxide for enhanced cellulose dissolution capabilities

N-Methylmorpholine-N-oxide (NMMO) is the solvent of choice in the lyocell process because of the interesting biodegradable, non-toxic and non-ecotoxic features that the full recovery of NMMO provides to the process. NMMO is used in its monohydrate form (1NMMO:1H2O) and cellulose dissolution occurs via hydrogen bond (HBs) formation between the oxygen at the oxide group (as the HB acceptor, HBA) and the hydroxyl groups of the cellulosic units (as the HB donor, HBD). Interestingly, H2O is a serious competitor for NMMO to form HBs with cellulose so the number of H2O-cellulose-HBs should be kept under control. Addition of co-solvents has become a common practice and the challenge is studying the capability of this additional co-solvent to balance the NMMO-cellulose-HBs versus H2O-cellulose-HBs and thus modify the solvent capabilities of the resulting ternary mixture. Herein, we prepared ternary mixtures by addition of the respective equivalents of H2O and DMSO (e.g., 1:0.5, 1:1 and 0.5:1) to anhydrous NMMO to obtain 1NMMO:1H2O:0.5DMSO, 1NMMO:1H2O:1DMSO and 1NMMO:0.5H2O:1DMSO. We correlated the solvent capability with the HB formed among the components in the different three ternary mixtures. 1NMMO:0.5H2O:1DMSO controlled the number of H2O-cellulose-HBs better than the other two mixtures and this helped to maintain the resulting cellulose solution in the liquid form at room temperature.

Investigation of aqueous and organic co-solvents roles in fabricating seawater reverse osmosis membrane

The addition of co-solvents in aqueous or organic phases of interfacial polymerization is a feasible strategy to tune the performance of aromatic polyamide (PA) thin-film composite (TFC) membrane for brackish water desalination, however, limited progress has been made in developing co-solvent-tailored seawater reverse osmosis (SWRO) membrane. Herein, SWRO membranes were prepared by adding various types of aqueous and organic co-solvents to reveal their impacts on the formation of the PA crumples. It was found that the aqueous/organic co-solvents affected the solubility parameter distance and interfacial tension between two immiscible phases, facilitating the diamine diffusion rate and resulting in a significant change in PA structure. The PA layer with modulated microstructure and varied surface features such as widened void structure, rougher surface, better wettability, and controlled cross-linking degree can be derived from the high interfacial instability that existed between the co-solvent and initial PA film due to the close mutual affinity. Besides, the additional polyvinyl alcohol coating layer atop the PA membrane successfully further enhanced the membrane selectivity. Overall, the mechanistic insights attained in this study revealed the relationship of diamine diffusion, physicochemical properties of PA layer and membrane separation performance for co-solvent-assisted membrane fabrication to render resultant SWRO membrane with more comparable permselectivity. The optimized TFC-SWRO membranes exhibited pure water permeability of 2.2 and 3.2 L m −2 h −1 bar −1 upon the assistance of aqueous and organic co-solvents, respectively, while maintaining excellent NaCl rejection of approximately 99% under seawater desalination tests. ✓ Aqueous or organic co-solvents were used aiming to flexibly design high-performance SWRO membrane. ✓ The synergistic impacts of solubility parameter and interfacial tension were established to elucidate diamine diffusion behavior. ✓ The relationship of “monomer diffusion - structure property - separation performance” was elaborated. ✓ The formation of a PVA coating layer enhanced the selectivity of co-solvent-assisted SWRO membrane.

Validation of UV spectrophotometric method for ketoprofen multicomponent crystals with malic acid and tartaric acid

These multicomponent crystals are formed by two chemical substances, between ketoprofen and their co-formers, which are malic acid and tartaric acid. Analysis of multicomponent crystals showed a possibility of interference between constituents. To determine interference between pure drugs and their co-formers, a validated, fast, easy, efficient, and adequate analysis method is required. This study aims to evaluate and develop an analytical method validation that is accurate, specific, and reproducible on ketoprofen multicomponent crystals using UV-Vis spectrophotometry. The study was conducted by the dissolving of phosphate buffer with 7.4 pH with the addition of ethanol co-solvent to obtain calibration curve solution. The calibration curve was analyzed for linearity, accuracy, and precision. Meanwhile, the placebo interference parameter was measured on an equimolar ratio of 1:1 between ketoprofen and co-former. Validation result on the wavelength of 260.5 nm with a range of 1-16.834 µg/mL showed the linearity of R2 = 0.999 and intercept P-value > 0.05, accuracy of Recovery = 100.652%, precision of RSD = 0.568%, and placebo interference of 0%. Based on the results of this study, the UV-Vis spectrophotometer method for ketoprofen multicomponent crystals fulfilled the validation standard.

Intensification of supercritical fluid in the extraction of flavonoids: A comprehensive review

The utilization of highly toxic, expensive, and eco-unfriendly organic solvents for the extraction process has been replaced by carbon dioxide (CO2) in its supercritical state. The most significant advantage of supercritical CO2 extraction is after the extraction process there was no trace amount of solvent present in extracted compounds since the residual CO2 can be easily depressurized and vented. Supercritical CO2 attracts interest because of its high compressibility, non-toxic, non-flammable, and physiological compatibility. This insight is a compilation of research works related to flavonoids extraction using a supercritical fluid. The significant parameters that affect the extraction process are temperature, pressure, solvent flow rate, and extraction time. These are the adjustable parameters that were optimized predominantly to improve the yield of the flavonoids extraction. The density of supercritical CO2 is attained by tuning temperature and pressure. The addition of co-solvents enhances the extraction of polar compounds. The residence time of CO2 in the extractor should be sufficient such that the solute reaches the saturation conditions in the fluid phase. This review article will give immense knowledge on the insights about the parameter that needs to be determined to scale up the extraction process.

Polylactide nanoparticle impregnation with carbamazepine in supercritical media and its subsequent release in liquid solvents: insights from molecular simulation

A full-atomic classical molecular dynamics simulation of polylactide nanoparticle impregnation with carbamazepine in supercritical carbon dioxide was performed. The effect of temperature (333 K, 373 K), pressure (20 MPa, 40 MPa) and ethanol addition (1.7 mol.%) on the impregnation process was studied. Based on the solvent accessible surface area values it was concluded that a pressure increase and cosolvent addition have a positive effect on polymer swelling, and a temperature increase at a similar pressure value has a negative effect. It was demonstrated that carbamazepine gets adsorbed on the polymer nanoparticle surface and penetrates inside the polymer matrix. The main interaction sites were determined. The average number and lifetime of hydrogen bonds, the solute mobility before and after the impregnation process were estimated. The possibility of carbamazepine release from the polylactide nanoparticle in water, ethanol and dichloromethane was studied at 310 K and 0.1 MPa. Since the drug and polymer affinities to the solvents are not equal, their release behavior is completely different.

A tailor-made deep eutectic solvent for 2.2 V wide temperature-tolerant supercapacitors via optimization of N,N-dimethylformamide/water co-solvents

A high-performing electrolyte plays an imperative role in the pursuit of high energy density, green, low-cost, and safe supercapacitors. To this end, a novel deep eutectic solvent (DES) composed of N-methylacetamide and lithium perchlorate has been engineered by the addition of co-solvents including water and N,N -dimethylformamide (DMF). Interestingly, each co-solvent makes a specific contribution to DES performance as water for flame resistance and DMF for antifreeze. The optimized hybrid DES is tested as the electrolyte for symmetric supercapacitors with polyaniline/reduced graphene oxide composite electrodes (PANI-rGO). The hybrid DES with high ionic conductivity imparts a high operation voltage of 2.2 V to devices whereas the PANI-rGO electrode with the pseudocapacitive behavior provides the high capacitances. Due to the above synergistic effects, our device delivers the maximum energy density of 28.2 W h kg −1 at a power density of 1.1 kW kg −1 and shows moderate cyclic stability at room temperature. More importantly, the supercapacitors can well function in a low temperature range from −20 to 25 °C. The device operated at 25 °C achieves the maximum capacitance of 41.9 F g −1 due to improved ionic conductivity of the DES electrolyte. The current study opens a new route towards sustainable and affordable energy storage devices. • DES electrolyte with N,N -dimethylformamide as co-solvent shows 2.2V window. • PANI-rGO exhibits pseudocapacitive behavior in the hybrid DES electrolyte. • Fabricated symmetric supercapacitor has potential to operate from −20 to 70 °C. • It delivers an energy density of 28.2 W h kg −1 at a power density of 1.1 kW kg −1

Cellulose Membranes in the Treatment of Spent Deep Eutectic Solvent Used in the Recovery of Lignin from Lignocellulosic Biomass.

Ultrafiltration was employed in the purification of spent Deep Eutectic Solvent (DES, a mixture of choline chloride and lactic acid, 1:10, respectively) used in the extraction of lignin from lignocellulosic biomass. The aim of this was to recover different lignin fractions and to purify spent solvent. The results revealed that the commercial regenerated cellulose membranes—RC70PP and Ultracel 5 kDa UF membranes—could be used in the treatment of the spent DES. The addition of cosolvent (ethanol) to the spent DES decreased solvent’s viscosity, which enabled filtration. With two-pass ultrafiltration process with 10 kDa and 5 kDa membranes about 95% of the dissolved polymeric compounds (lignin and hemicelluloses) were removed from the spent DES. The utilized membranes also showed the capability to fractionate polymeric compounds into two fractions—above and under 10,000 Da. Moreover, the 10 kDa cellulose-based membrane showed good stability during a continuous period of three weeks exposure to the solution of DES and ethanol. Its pure water permeability decreased only by 3%. The results presented here demonstrate the possibility to utilize cellulose membranes in the treatment of spent DES to purify the solvent and recover the interesting compounds.

Two for one: propylene carbonate co-solvent for high performance aqueous zinc-ion batteries – remedies for persistent issues at both electrodes

We find that the addition of PC co-solvent suppresses parasitic reactions at both electrodes, and improves the cycling stability and coulombic efficiency of Zn-ion batteries.

On the formation of hydrogen peroxide in water microdroplets.

Recent reports on the formation of hydrogen peroxide (H2O2) in water microdroplets produced via pneumatic spraying or capillary condensation have garnered significant attention. How covalent bonds in water could break under such mild conditions challenges our textbook understanding of physical chemistry and water. While there is no definitive answer, it has been speculated that ultrahigh electric fields at the air–water interface are responsible for this chemical transformation. Here, we report on our comprehensive experimental investigation of H2O2 formation in (i) water microdroplets sprayed over a range of liquid flow-rates, (shearing) air flow rates, and air composition, and (ii) water microdroplets condensed on hydrophobic substrates formed via hot water or humidifier under controlled air composition. Specifically, we assessed the contributions of the evaporative concentration and shock waves in sprays and the effects of trace O3(g) on the H2O2 formation. Glovebox experiments revealed that the H2O2 formation in water microdroplets was most sensitive to the air–borne ozone (O3) concentration. In the absence of O3(g), we could not detect H2O2(aq) in sprays or condensates (detection limit ≥250 nM). In contrast, microdroplets exposed to atmospherically relevant O3(g) concentration (10–100 ppb) formed 2–30 µM H2O2(aq), increasing with the gas–liquid surface area, mixing, and contact duration. Thus, the water surface area facilitates the O3(g) mass transfer, which is followed by the chemical transformation of O3(aq) into H2O2(aq). These findings should also help us understand the implications of this chemistry in natural and applied contexts.

Sensitivity of Isomerization Kinetics of 1,3,5-Triphenylformazan on Cosolvents Added to Toluene.

Formazan molecules exhibit photochromism because isomerization processes following excitation may occur in both the azo group and the hydrazone group; thus, each formazan may be present in various forms with different colors. The ratio of these forms depends on the illumination conditions and the environment of the formazan with a most incisive sensibility of the thermal anti-syn relaxation of the C═N toward slight traces of impurities in toluene solutions, as reported most prominently for 1,3,5-triphenylformazan. Here, we study the latter compound with transient absorption spectroscopy to investigate the role of these traces by adding small amounts of both protic and aprotic cosolvents. Whereas the activation barrier decreases if the binary solvent mixture has a higher polarity, the role of hydrogen bonding can have a reverse impact on the thermal isomerization rate. Both the addition of an aprotic cosolvent and the addition of a protic cosolvent can slow the reaction due to their hydrogen-bond accepting and hydrogen-bond donating properties, respectively. In the case of methanol as a cosolvent, this effect outweighed that of the polarity increase for small concentrations, which was not observed for the fluorinated alcohol hexafluoroisopropanol. The results are explained in the context of a competition between solute-cosolvent and cosolvent-cosolvent hydrogen bonding.

Berberis Vulgaris Fruit: Determination of Phenolic Compounds in Extracts Obtained by Supercritical CO2 and Soxhlet Methods Using HPLC.

Recently, research studies on nutraceutically important polyphenolic substances have attracted intensive attention. Berberis vulgaris is an important source of polyphenolic compounds and is often used in traditional medicine. In this study, the extraction of rutin and apigenin rich oil from Berberis vulgaris fruits was evaluated by supercritical carbon dioxide (Sc-CO2) extraction method with and without co-solvent. As valuable antioxidants, rutin and apigenin content of extracts were analyzed by HPLC, and their amounts were maximized via parametric optimization. The rutin compound studied in this research has the potential to be a drug against the COVID-19 virus. The operating conditions were considered in the range of 35–70 °C temperatures, 140–240 bar of pressures, 0.35–1.00 mm of mean particle sizes, 3–7 l/min of CO2 flow rates, and 0–8% w/w co-solvent. As a result of Sc-CO2 extractions, the amounts of rutin and apigenin were found as 173 ± 14.97 µg/g and 2.91 ± 0.11 µg/g, respectively, with the 8% (w/w) co-solvent addition. The amounts of rutin and apigenin obtained by Soxhlet extractions were found as 208.81 ± 8.48 µg/g and 6.55 ± 0.21 µg/g, respectively. When the Sc-CO2 method was compared with the Soxhlet method, it was seen that the fast and eco-friendly Sc-CO2 method was an ideal extraction method by providing 76.89% rutin and 44.53% apigenin recoveries. As a result of this study, the maximum extraction conditions for rutin and apigenin were obtained as 160 bar, 40 °C, 0.35 mm particle size, 3 l/min CO2, 8% w/w co-solvent ratio, and 120 min extraction period.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s12161-021-02136-8.

Experimental Investigation and Optimization of Non-Catalytic In-Situ Biodiesel Production from Rice Bran Using Response Surface Methodology Historical Data Design

Rice bran oil (RBO)is claimed to be a potential feedstock for biodiesel production. Non-catalytic in-situ biodiesel production from a low-cost feedstock (rice bran) using subcritical ethanol-water mixture was investigated in this study. The influence of four independent variables, i.e., addition of co-solvent, ethanol concentration, temperature, and time of reactions, on the yield of biodiesel was examined. The results showed that the most effective co-solvent wasethyl acetate and the optimum ethanol concentration, temperature and reaction time were 80% v/v, 200 oC and 3 hours, respectively. The maximum yield of biodiesel was found to be around 80%. The optimization of operating conditions was carried out by response surface methodology (RSM) with historical data design (HDD). The statistical method also suggested similar optimum operating conditions, i.e., 78.44% (v/v) ethanol concentration, 200 oC, and 3.2 hours reaction time with ethyl acetate as a co-solvent. The predicted maximum biodiesel yield was also slightly lower, i.e., 76.98%. Therefore, this study suggests that biodiesel production from rice bran through a non-catalytic in-situ process using a subcritical ethanol-water mixture with ethyl acetate as a co-solvent is very feasible since the yield can reach 80%. The study also found that RSM with HDD can predict the optimum operating conditions with a good accuracy.

A DFT and molecular dynamics simulation study of single-walled carbon nanotube as a drug delivery system for few model nitrogen mustard drugs

• Optimized geometries of the model nitrogen mustards substituted with heterocycles, SWCNT and the complexes between them were calculated using DFT technique. • Interaction energies were calculated from the optimized structures. • HOMO, LUMO, DOS, NBO and various quantum chemical descriptors were calculated for the optimized complexes. • NCI plots were calculated to show the interactions between drug and SWCNT • Molecular dynamics simulations were performed to investigate the effect of EtOH solvents on the stability of the complexes between drug and SWCNT Current study mainly describes the delivery of three model nitrogen mustard drugs with heterocyclic substituents by single-walled carbon nanotube (SWCNT) as a drug delivery system. The electronic properties and interaction energies were calculated using density functional theory (DFT). Results suggest that the model drugs bind exothermically with SWCNT. HOMO-LUMO, DOS plots and non-covalent interaction (NCI) plots indicate that the interaction between the drugs and SWCNT are weak. Further, calculations of quantum mechanical descriptors suggest that electron migration takes place from SWCNT to the drug. Finally, molecular dynamics simulation was performed to investigate the effect of EtOH co-solvent on the stability of the drug-SWCNT complex. The results suggest that the complexes are most stable in a water environment and the addition of EtOH co-solvent makes it unstable. In summary, all the results suggest that SWCNT may successfully deliver the investigated model nitrogen mustard drugs and these systems are most stable in a water solvent.

Supercritical fluid chromatography for the analysis of natural dyes: From carotenoids to flavonoids.

Plant-derived natural dyes are used in a variety of formulated products, from food to cosmetics and pharmaceutics. In addition to their color, they also provide some bioactivity. While they are mostly analyzed with high-performance liquid chromatography, supercritical fluid chromatography was also employed for several dye families, mostly for carotenoids and chlorophylls, and more recently for anthraquinones and flavonoids. These supercritical fluid chromatography methods are described in this review. Because the dyes have different structures and structural variations (polarity, isomers, etc.), the best chromatographic system to achieve their separation is not always the same. Hydrophobic stationary phases are preferred for the most hydrophobic dyes (chlorophylls and carotenoids) while polar stationary phases are preferred for the polar dyes (anthraquinones and flavonoids). Regarding the mobile phase composition, chlorophylls and carotenoids are best eluted with moderate proportions of co-solvent in CO2 (about 40%), while the most polar glycosylated flavonoids require higher proportions of co-solvent and acidic additives. Because dyes are colorful, ultraviolet-visible detection is often sufficient, while mass spectrometry offers additional structural information. Furthermore, fundamental information can also be gained through chromatographic analysis of dyes: either solubility in supercritical fluids, in view of their extraction, or retention behavior providing an understanding of stationary phase properties.

(Invited) Enabling Fast Charging Lithium-Ion Batteries through Balancing Ion Transport and Solvation

The advent of novel electrolyte chemistries has shown significant improvements in fast-charging and extreme operation capabilities. As ionic transport in the electrolyte is a dominant contributor to the rate capability of lithium-ion batteries (LIBs), addition of low-viscosity co-solvent is the most common approach to improve the transport properties of carbonate electrolytes, leading to improved rate performance and widened operation temperature window. Recent work further moves to replace carbonates entirely with low-viscosity solvents. However, such solvents reduce the long-term stability of the cells, which must be addressed before practical use. While the development of localized high concentration electrolytes (LHCEs) has shown significantly improved high voltage and wide-T stability as well as Li metal cycling stability, the substantially decreased ionic conductivity compared with SOA electrolytes makes them challenging to support <15mins charging. Here, we discuss a class of partially fluorinated, ester-based electrolytes with balanced ion transport and critical solvation properties for practical LIBs that can operate at extreme conditions including fast charging, wide temperature (T) range and high voltage.

Supercritical fluid extraction of phytosterols from sugarcane bagasse: Evaluation of extraction parameters

Sugarcane bagasse, is one of the largest agriculture residues in the world and its chemical composition is interesting for several areas. Among one of the lipid components was found phytosterols. These are structurally and functionally similar to cholesterol, they are contributing to the reduction of cholesterol in the blood when consumed. Phytosterols were extracted with supercritical CO2 from sugarcane bagasse. In this work was evaluated the effect of temperature (40–80 °C), flowrate (6–10 ml min−1), pressure (200–400 bar) and co-solvent (0–10% ethanol) on extraction yield and phytosterols (β-sitosterol, campesterol and stigmasterol) concentration. The addition of co-solvent improves total phytosterols concentration at low pressure, but has no effect at high pressure. At optimal extraction conditions the yield was 0.92% and 0.300 mg total phytosterol g−1 dry material. The extract obtained presented a lipidic composition with possible cardiovascular health benefits due to phytosterols, policosanols and unsaturated fatty acids found.

Evaluation of hybrid solvents featuring choline chloride-based deep eutectic solvents and ethanol as extractants for the liquid\u2013liquid extraction of benzene from n-hexane: towards a green and sustainable paradigm

Deep eutectic solvents (DESs) have high viscosities, but known to be mitigated by addition of suitable co-solvent. The effect of such co-solvent on the extraction efficiency of the hybrid solvent is hardly known. This study examined the effect of ethanol on three choline chloride-based DESs (glyceline, reline, and ethaline) by mixing each in turn with ethanol in various volume proportions. The hybrid solvents were evaluated for the extraction of benzene from n-hexane. Pseudo-ternary liquid–liquid equilibrium data were obtained using the refractive index method at 303 K and 1 atm for the systems, n-hexane (1) + benzene (2) + hybrid solvent (glyceline/ethanol, ethaline/ethanol, reline/ethanol) (3), and used to evaluate distribution coefficient (D) and selectivity (S). Furthermore, the physicochemical properties of the hybrid solvents were also determined. The results indicate increase in selectivity with increasing ethanol addition up to 50% and decrease with further addition. All hybrid solvents with 50% ethanol outperform sulfolane and are suitable replacement for same as green and sustainable extractant for aromatics from aliphatics. The glyceline + 50% ethanol emerged the overall best with 49.73% elevation in selectivity and 41.15% reduction in viscosity relative to the neat glyceline. The finding of this study is expected to fillip the drive for paradigm shift in petrochemical industries.

Boosting the kinetic efficiency of formate dehydrogenase by combining the effects of temperature, high pressure and co-solvent mixtures

The application of co-solvents and high pressure has been shown to be an efficient means to modify the kinetics of enzyme-catalyzed reactions without compromising enzyme stability, which is often limited by temperature modulation. In this work, the high-pressure stopped-flow methodology was applied in conjunction with fast UV/Vis detection to investigate kinetic parameters of formate dehydrogenase reaction (FDH), which is used in biotechnology for cofactor recycling systems. Complementary FTIR spectroscopic and differential scanning fluorimetric studies were performed to reveal pressure and temperature effects on the structure and stability of the FDH. In neat buffer solution, the kinetic efficiency increases by one order of magnitude by increasing the temperature from 25° to 45 °C and the pressure from ambient up to the kbar range. The addition of particular co-solvents further doubled the kinetic efficiency of the reaction, in particular the compatible osmolyte trimethylamine-N-oxide and its mixtures with the macromolecular crowding agent dextran. The thermodynamic model PC-SAFT was successfully applied within a simplified activity-based Michaelis-Menten framework to predict the effects of co-solvents on the kinetic efficiency by accounting for interactions involving substrate, co-solvent, water, and FDH. Especially mixtures of the co-solvents at high concentrations were beneficial for the kinetic efficiency and for the unfolding temperature.