Reverse Micellar System Research Articles

Effect of CHAPS on the selective synthesis of (S)-n-octyl ibuprofen ester in AOT reverse micelle catalyzed by lipase

CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate), a biocompatible zwitterionic surfactant derived from bile salt, has attracted great attention due to its distinct molecular structure and aggregation behavior. Addition of a low level of CHAPS to AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reverse micelles has been found to be able to enhance the catalytic activity of the solubilized lipase. In this study, the effect of CHAPS on the lipase-catalyzed selective synthesis of (S)-n-octyl ibuprofen ester was investigated in AOT reverse micelles at 37 °C. The results demonstrate that the presence of CHAPS in AOT reverse micelle enhances both the yield and the enantiomeric excess (ee) value of (S)-n-octyl ibuprofen ester, especially at low water content. With 8 mM CHAPS in AOT reverse micelle ([AOT] = 100 mM, [H2O]/[AOT] = 12, pH = 7.0), a 48-hour yield of 34.2 % could be obtained, which is approximately twice that without CHAPS. In addition, the ee value of the product is increased from 89.1 % to 98.2 %. To understand the mechanism of the CHAPS effect, dynamic light scattering, fluorescence emission spectroscopy and Fourier transform infrared spectroscopy techniques were used to characterize the size of the reverse micelle, the conformation of the solubilized lipase and the activity of the bulk water in the reverse micelle. It reveals that at low water content, the addition of CHAPS enlarges the size of AOT reverse micelle, stabilizes the lipase conformation and reduces the nucleophilicity of bulk water in AOT reverse micelle. The synergistic effect of the aforementioned factors results in the improvement of the enzymatic synthesis of the ester. The above research provides scientific support for the lipase-based preparation of chiral acids/alcohols in the reverse micellar system.

Limonene biosolvent-based non-aqueous dyeing medium for salt-free and alkali-free rhamnolipid (RL) biosurfactant reverse micellar dyeing of cotton fabric with reactive dyes

The feasibility of using different forms of limonene biosolvents as dyeing medium in rhamnolipid (RL) biosurfactant-based reverse micellar dyeing system for cotton fabrics is investigated, with different dyeing profiles. Experimental results reveal that limonene-dyed fabrics can achieve generally higher colour yield than water-dyed fabrics while samples dyed by one-step dyeing method could obtain higher colour yield, but poorer relative unlevelness index (RUI) values when compared with samples dyed by two-step method. The CIE L*a*b* value and reflectance of water-dyed and limonene-dyed samples were examined. The pH value of aqueous and non-aqueous dye liquor was measured. SEM images of limonene-dyed cotton fabrics and TEM images of reverse micelle morphology were evaluated. Washing and crocking fastness of the dyed samples were also assessed. The resulting evidence validate that limonene is feasible for reverse micellar reactive dyeing of cotton fabric with the use of RL biosurfactant and it can be one of the alternative solvents, making the dyeing process more natural, more biodegradable and environmentally more sustainable.

A Study of Color Fixation Agents in Secondary Alcohol Ethoxylate-Based Reverse Micellar Cotton Dyeing System with Reactive Dyes

ABSTRACT Influence of color fixation agent (CFA) and dyebath pH in secondary alcohol ethoxylate (SAE)-based reverse micellar dyeing system of cotton with reactive dyes was investigated and compared with water-based dyeing system using different alkali (i.e. CFA) such as: (i) sodium bicarbonate (NaHCO3), (ii) sodium carbonate (Na2CO3) and (iii) sodium hydroxide (NaOH). The color, tensile strength, fastness and surface morphological properties of dyed samples were examined. Experimental results showed that samples dyed with Na2CO3 can achieve the highest color yield, followed by NaHCO3 and NaOH in both water-based and reverse micellar dyeing system. The color yield and reflectance percentage of the dyed cotton samples were found to be closely related to the dyebath pH value. Relative unlevelness indices (RUI) also reflected that cotton samples dyed with NaOH in reverse micellar dyeing system have a higher chance of color unlevelness when compared with NaHCO3 and Na2CO3. Tensile strength results affirm that higher alkalinity of dyebath could cause higher strength loss to the colored cotton samples. Both cotton samples dyed by water and SAE approach showed good to excellent color fastness properties while scanning electron microscopic (SEM) images exhibit that the use of different alkalis may cause some damage to the cotton fiber.

Reverse Micellar Dyeing of Cotton Fabric with Reactive Dye Using Biodegradable Non-Ionic Surfactant as Nanoscale Carrier: An Optimisation Study by One-Factor-at-One-Time Approach.

This study investigates the feasibility of using biodegradable secondary alcohol ethoxylate (SAE) non-ionic surfactant as a building block for the formation of reverse micelles, functioning as reactive dye carriers for the dyeing of cotton fabric in non-aqueous octane medium. Ten dyeing parameters were optimised, by a one-factor-at-a-time approach, namely: (i) effect of colour fixation agent; (ii) surfactant-to-water mole ratio; (iii) surfactant-to-co-surfactant mole ratio; (iv) volume of soda ash; (v) volume of dye; (vi) solvent-to-cotton ratio; (vii) dyeing temperature; (viii) dyeing time; (ix) fixation time; (x) soda-ash-to-cotton ratio. The colour properties, fastness properties and physical properties of SAE-dyed samples were experimentally compared with the conventional water-dyed samples. The optimised condition was found when SAE samples were dyed as follows: (a) 1:20 surfactant-to-water ratio; (b) 1:8 surfactant-to-co-surfactant ratio; (c) 10:1 solvent ratio; (d) 40 min dyeing time; (e) 60 min fixation time; and (f) 70 °C dyeing and fixation temperature. The results showed that SAE-dyed samples have better colour strength, lower reflectance percentage and comparable levelness, fastness and physical properties than that of water-dyed samples. SEM images revealed that the dyed cotton fibres had no severe surface damage caused by an SAE-based reverse micellar dyeing system. The TEM image depicts that the reverse micelle was of nanoscale, spherical-shaped and had a core-shell structure, validating the presence of reverse micelle as a reactive dye carrier and the potential of an SAE-based reverse micellar system for dyeing of cotton fabrics.

Potential Role of Bromelain in Wound Healing Application: A Review

Bromelain is a proteolytic enzyme derived from the pineapple plant (Ananas comosus). Bromelain can be extracted from pineapple stems and fruits. Additionally, it can be derived from pineapple wastes such as the core, crown, and peel. Various extraction and purification methods such as reverse micellar system, aqueous two-phase system, chromatographic techniques, and membrane filtration have been used in order to produce high-qualitybromelain. Bromelain has been used clinically since 1876 and was first introduced as a therapeutic agent in 1957. Bromelain has gained increasing acceptance and compliance among patients as a phytotherapeutic drug due to its safety and lack of undesirable side effects. Bromelain is regarded as a nutrient that promotes wound healing due to the presence of several closely related proteinases that exhibit anti-inflammatory, fibrinolytic, and debridement properties.

Dyeing of Linen Fabrics in Supercritical CO2 Using a Reverse Micellar System with Ionic Liquid Domains

ABSTRACT In order to realize the anhydrous dyeing of linen fabric with reactive dyes in supercritical CO2, a supercritical CO2 ionic liquid reverse micelle system was constructed, and the dyeing process of linen fabric in this system was studied. In this system, linen fabric can be dyed with reactive dyes without special pretreatment. The results show that the dyeing depth of linen fabric can be significantly improved by increasing the amount of surfactant. With the increase in temperature, the dyeing depth first increases and then decreases. The dyeing pressure displays little effect on the dyeing depth. After dyeing, there are a lot of floating colors on the surface of the fabric. Increasing the temperature and prolonging the dyeing time are conducive to dye fixation on the fabric. Adding a certain amount of dimethyl sulfoxide (DMSO) to the system can improve the dyeing performance significantly. In this paper, the best dyeing conditions of linen fabric are as follows: w, 1.2; surfactant conc. 3.5 × 10−2 g/mL; T, 90°C; t, 180 min; p, 21MPa; DMSO concentration, 76.8 mmol/L.

Dyeing of polyamide fabrics with a reverse micellar system using soybean oil as a solvent

AbstractThe current study reports the results of non‐aqueous dyeing on polyamide fabrics based on a reverse micellar system composed of a stable emulsion of soybean oil, a co‐surfactant, a nonionic surfactant and acid dyes. The system does not make use of water or electrolytes and significantly reduces the dyebath volume. The influence of the hydrophilic lipophilic balance of the surfactants was evaluated, and it was found that the more hydrophilic the surfactant, the better the interaction of the reverse micellar emulsion with the substrate and, consequently, the greater the resulting colour strength. The co‐surfactant plays an important role in the system, as its proportion to the surfactant/oil mixture is directly related to better exhaustion of the dyebath. The results were compared with those from a conventional water‐based dyeing system. Colour matching was performed using the CIELab colour difference formula (ΔE) measured by a reflectance spectrophotometer.

Wormlike reverse micelles loaded with aqueous extracts of Psidium guajava leaves: Performance evaluation by rheology and Raman microscopy methods

Phenolic compounds are molecules that provide health benefits. However, they present problems for their use. The use of wormlike reverse micelles to load aqueous extracts of Psidium guajava (guava) was carried out. Different solutions (i.e., content variation of canola oil, oleic acid, soy lecithin; stirring time, stirring speed) were obtained by incorporation of water by ultrasound and centrifugation. The behavior of the wormlike micelles was evaluated with optical microscopy, simple shear tests, and Raman microscopy with and without aqueous extract of guava leaves. The wormlike reverse micelles solution were adjusted to the Carreau-Yasuda model. Influence of the aqueous extracts of guava leaves were observed in the parameters of Carreau-Yasuda model, related with changes in the packing of the hydroxyl groups and high order of packing in wormlike reverse micellar system.

Lipase B from Candida antarctica in Highly Saline AOT-Water-Isooctane Reverse Micelle Systems for Enhanced Esterification Reaction

Butyl oleate synthesis by the lipase B from Candida antarctica (CalB) under extreme halophilic conditions was investigated in the present research through the AOT/Water/Isooctane reverse micellar system. The impact of aqueous content (Wo=H2OSurfactant) and NaCl variation on the enzymatic activity of CalB in the butyl oleate reaction in reverse micelles was explored. The results indicated that, based on the increase of NaCl, it is remarkable to achieve higher enzymatic activity up to 444.85 μmolmin at 5 M NaCl and Wo = 10, as the best esterification conditions at pH 7.2 and 30 °C. However, it was clear that butyl oleate synthesis by lipase CalB increased based on the reduction in the average reverse micelle size, where reverse micelle sizes were determined by dynamic light scattering (DLS). This increase in butyl oleate synthesis demonstrated the potential of reverse micelles as systems that enhance mass transport phenomena in heterogeneous biocatalysis. Furthermore, reverse micelles are promising systems for extreme halophilic lipases research.

Comparison of water-based dyeing system and alkyl polyglucoside (APG) surfactant-based reverse micellar dyeing system with reactive dyes for cotton

Comparison of water-based dyeing system and alkyl polyglucoside (APG) surfactant-based reverse micellar dyeing system with reactive dyes for cotton

Rhamnolipid (RL) microbial biosurfactant-based reverse micellar dyeing of cotton fabric with reactive dyes: A salt-free and alkali-free one-bath one-step approach

The viability of reverse micelles, using rhamnolipid (RL) microbial biosurfactant as the building block, for dyeing of cotton fabrics with reactive dyes has been studied. This novel and sustainable dyeing system not only can achieve salt-free, but also alkali-free under optimised dyeing parameters. Experimental results reveal that RL-based reverse micellar dyeing system can be achieved in one-bath one-step dyeing approach, which is environmentally friendly, time and energy saving, with better colour yield, lower reflectance when compared with conventional water-based dyeing system. RL-dyed samples can obtain comparable colour levelness, washing and rubbing fastness to water-dyed samples. No significant chemical damage of cotton fibre surface was observed from scanning electron microscopic (SEM) investigation. The dye-encapsulated reverse micelle was justified as spherical-like morphology from transmission electron microscopic (TEM) observation. The outcome of the study validates the potential and applicability of RL, as a substitute of synthetic surfactant, in non-aqueous reactive dyeing of cotton fabrics.

Polyethylene Glycol (PEG) Non-Ionic Surfactant-Based Reverse Micellar Dyeing of Cotton Fabric with Hot Type Trichloropyrimidine (TCP)-Based Reactive Dyes

ABSTRACT This work aims to examine the feasibility of using poly(ethylene glycol) (PEG)-based reverse micellar dyeing system for dyeing cotton fabric with the use of hot type trichloropyrimidine (TCP)-based reactive dyes and to evaluate the possibility of saving the dyeing energy used during the dyeing process. Experimental results show that fabrics dyed in reverse micellar system at 90°C can achieve higher color yield than the conventional water-based system at the same temperature. Further experiments using reverse micellar system for dyeing cotton at 80°C (a reduction of working temperature of 10°C) provided color yield comparable to that of conventional water-based system except the use of yellow dye. Both water-dyed and octane-dyed samples had good to excellent levelness, washing and rubbing fastness and 98.5% of octane could be recycled after distillation. Reflectance curves were identical in shape and the SEM images showed neither of the dyeing systems caused any significant damage to cotton fibers. These findings validated the possibility of using reverse micellar dyeing system for hot type TCP-based reactive dyeing of cotton fabrics at lower coloration temperature and energy consumption.

Lactoperoxidase partitioning from whey using the reverse micelles of non‐ionic/ionic mixed surfactants: Improvement of back extraction

AbstractThe reverse micellar system formed with a mixture of ionic and non‐ionic surfactants, AOT (Sodium bis[2‐ethyl hexyl] sulfosuccinate)/Tween 80 in isooctane, was studied for the selective extraction of Bovine Lactoperoxidase (LP) from acid whey. The effect of pH and ionic strength of acid whey and surfactant concentrations were studied and a maximum of 86% LP was extracted from acid whey at pH 9.5 with the addition of 0.2 M KCl to the reverse micelles formed with AOT (115 mM)/Tween 80 (23 mM). The back extraction of LP was studied at different aqueous stripping phase pH, ionic strength and concentration of counter‐ionic surfactant Cetyltrimethylammonium bromide (CTAB). The back extraction of 112% with 80% LP recovery was achieved when the stripping phase pH was 10.5 with 1.5 M KCl and 60 mM CTAB. The antimicrobial activity of the extracted LP showed reduction in colony‐forming units of S. aureus.Novelty impact statementThe reverse micelles formed with AOT/Tween 80 surfactant mixture minimize the pH‐dependent denaturation of LP and widen the pH window (7.5–9.5) for LP extraction. The back extraction of LP from the reverse micellar phase to aqueous stripping phase was improved by the addition of CTAB as counter‐ionic surfactant. A purification fold of 11.26 achieved with minimal loss in activity of LP by retaining the native Antimicrobial characteristic.

CTAB Reverse Micelles as Catalysts for the Oxidation of Ascorbic Acid by K3[Fe(CN)6

The oxidation of ascorbic acid by K3[Fe(CN)6] was studied in reverse micellar systems composed of CTAB (Cetyltrimethylammonium bromide), and it was found the observed first order (k1(aq) = 5.2×10−5 s−1, k1(rev) = 61.4×10−4 s−1) rate constant in reverse micellar medium is around forty times higher compared to aqueous medium under identical conditions. The rate enhancement (k2(aq) = 0.9×10−5 mole−1.dm3.sec−1, k2(rev) = 1.75×10−3 mole−1.dm3.sec−1) is attributed to the large concentration effect and lower dielectric constant in the reverse micelles. The rate of the reaction increases with increase in W = {[H2O]/[surfactant]} which is explained in terms of ionic strength of the water pool. The effect of surfactant concentration on rate was explained on the basis of Berezin pseudo phase model. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

A review on reverse micellar approach for natural fiber dyeing

AbstractThis study reviews the need and importance of non‐aqueous dyeing systems in the chemical processing industry, especially using the reverse micellar system in the dyeing of natural fibres. When it comes to conventional dyeing systems, which use large quantities of water, chemical, and energy, cause a lot of effluent load to the environment. Again the effluent water has to be treated well to eliminate all the harmful substances in it. To overcome the issues, a lot of research has been carried out in this area to minimise the use of water and chemicals in the dyeing process. Like use of low material to liquor ratio (M:L) in dyeing, dyes with high fixation at lower temperatures, low/salt less dyeing in case of reactive dyeing with cotton, cottonseed oil dyeing, microwave‐assisted dyeing, and use of supercritical carbon dioxide in case of polyester dyeing and many more. All the above said methods are aqueous‐based and, after the completion of dyeing, results in wastewater generation, which requires further treatment to reduce the harmful chemicals. Therefore, to further minimise the use of water and chemicals in the dyeing of natural fibres reverse micellar system has been introduced with the help of surfactants of both Ionic and nonionic in nature. As of today, a lot of work has been carried out in the dyeing of natural fibres with this system by employing ionic, nonionic, and mixed surfactants. Fascinating results were obtained in the dyeing with good levelness, high exhaustion, and fixation values, and results were compared with conventional dyeing. Computer colour matching studies were also done better to understand the applicability of these systems in the industry and found nearer results.

PHOTOPHYSICAL ASPECTS OF POLARITY SENSITIVE FLUOROPHORE IN CATIONIC REVERSE MICELLES

In recent years, the field of reverse micelles has witnessed a significant growth of interest, partly due to the finding that proteins, other biopolymers, and even bacterial cells can be solubilized in the reverse micellar systems. Among surfactants capable of forming water in oil microemulsion, the cationic surfactant cetyltrimethylammonium bromide (CTAB) has received particular attention because of its ability to solubilize relatively large amount of water in a variety of hydrophobic organic solvents. Due to versatile photochemical and photophysical properties of Ru(II) complexes, Ru(II)- phenanthroline and its derivatives were used in this present work to form CTAB cationic reverse micelles and studied to characterise their photophysical properties such as absorption, emission and excited state life time. The findings from the spectral data observed in the present study proves that the excited state properties of Ru(II)-phenanthroline complexes are dramatically altered in the presence of reverse micelle. Specifically reverse micelle encapsulation of [Ru(dpphen)3]2+ complex in restricted environment causes blue shift in the emission maximum as well as have longer radiative lifetime. The blue shift in the emission maximum in the case of [Ru(dpphen)3]2+ indicates that the probes are near the water in oil reverse micellar interface, tightly bound and are not displaced towards the water pool of the micelle even at the highest water loading W0=50, which reveals the increased hydrophobicity. This highest fluorescence lifetime can serve as an excellent indicator to point out the location of the probe in a microheterogeneous system/environment.

Enhanced Hydrodynamic Radius of AOT/n-heptane/Water Reverse Micellar System Through Altered Electrostatic Interactions and Molecular Self-Assemblies.

We have demonstrated a unique approach to alter the aqueous pool size of an AOT/n-heptane/water reverse micellar system. A positively charged dye Rhodamine B (RhB) and negatively charged Rose Bengal (RB) were incorporated in the reverse micellar pool to investigate the effect of electrostatic interactions and stacking effects among the dye molecules on the AOT/n-heptane/water interface. Dynamic light scattering revealed increase in reverse micellar pool size in presence of positively charged dye aggregates at the oil-water interface. However, less expansion was observed in presence of negatively charged dye aggregates (RB). This confirms the role of electrostatic interaction in modulating the hydrodynamic radius. A head-to-tail type of stacking of RhB molecules at the interface favors this expansion. The differences in stacking of the two dyes inside the reverse micelles and their torsional mobility indicated the role of the reverse micellar interface and H-bonding ability of the microenvironment on dye aggregation. Conductivity measurements demonstrated a significant drop in percolation temperature of the reverse micellar system in presence of dye aggregates. This confirms the effect of dye aggregation and electrostatic interaction on such expansion. This strategy can be exploited for solubilizing greater amounts and a wider variety of drug molecules in microemulsions.

Ionic amphiphile stabilized reverse micellar systems and their implications for nanoencapsulation

HypothesisEncapsulation of core nanoparticles using reverse micelles is a widely used approach owing to its effective organization. Hence, it is of value to analyze the physicochemical mechanisms associated with the reverse micelle-based encapsulation for the choice of appropriate surfactant for the encapsulation process. The presence of ionic micelles, catalyst ions and surface charge of the core nanoparticles are expected to influence the stability of reverse micelles. Hence, it is of value to find the optimized conditions for stable reverse micelles formation through understanding the multiple double layer formation inside of ionic reverse micelles. ExperimentsReverse micelle systems stabilized by non-ionic, anionic and cationic surfactants are formulated with the presence of ammonia ions and negatively charged core nanoparticles. The structure of reverse micelles is studied by measuring its average hydrodynamic diameter and optical transmittance measurements. Shell encapsulation experiments are performed in stable and unstable reverse micellar structures. FindingsIonic surfactants help to form stable reverse micellar structures. Multiple double layers formation is explained in ionic reverse micelles for the first time. Magnetite@silica is chosen as a model system to demonstrate the observed effects. The results obtained could remove the complexity in understanding the ionic reverse micellar systems for the functionalization of nanoparticles.

Purification, characterization, and chemical modification of Bacillus velezensis SN-14 fibrinolytic enzyme

Fermented bean foods are a crucial source of fibrinolytic enzymes. The presented study aimed to purify, characterize, and chemically modify Bacillus velezensis SN-14 fibrinolytic enzyme. The fibrinolytic enzyme was purified using CTAB/isooctane/hexyl alcohol/n-butyl alcohol reverse micellar system, and the purified enzyme was chemically modified to improve its enzymatic activity and stability. Enzyme activity recovery and the purification fold for this enzyme were 44.5 ± 1.9% and 4.93 ± 0.05 fold, respectively. SDS-PAGE results showed that the molecular weight of the purified fibrinolytic enzyme was around 28 kDa. Besides, the optimum temperature and pH of the purified fibrinolytic enzyme were 37 °C and 8–9, respectively. Fe2+, mPEG5000, and pepsin were used for chemical modification and for improving the activity and stability of the purified enzyme. Thermal and acid-base stability of chemically modified enzymes increased significantly, whereas enzymatic activity increased by 7.3 times. After 30 d of frozen storage, the modified enzyme's activity was remarkably lower (33.2%) than the unmodified enzyme (60.6%). The current study on B. velezensis SN-14 fibrinolytic enzyme and chemical modification method using Fe2+, mPEG5000, and pepsin provide a reference for developing fibrinolytic drugs and foods.

Predicting the size of salt-containing aqueous Na-AOT reverse micellar water-in-oil microemulsions with consideration for specific ion effects

HypothesisReverse micellar solutions are thermodynamically stable systems in which surfactant molecules surround water droplets within a continuous organic phase. Among their many applications, they can be used for the synthesis of nanoparticles of controlled agglomeration. Here, we consider the role specific ion effects play in reverse micelle size reduction. ExperimentsDynamic light scattering measurements and the Gouy-Chapman electrical double layer model were combined to study water/AOT/isooctane reverse micellar systems (wo = 10). Linear relationships between the solvodynamic diameter (D) of reverse micelles containing various concentrations of FeSO4, Mg(NO3)2, CuCl2, Al(NO3)3, Fe(NO3)3, Y(NO3)3, NaBH4, ZrOCl2, and NH4OH, and their calculated Debye screening lengths, κ−1, were observed with decreasing D and increasing salt concentration (c). FindingsBy comparing the linear fits for reverse micelle size as a function of c−1/2, we determined the size can be described as a function of the Debye screening length, cation valency (z), and specific anion hydrated radius (ran), where D = 3.1z κ−1 + bi, and bi is linearly related to ran. Our model accurately predicts reverse micelle sizes with the addition of monovalent, divalent, and trivalent salts for which the primary hydrolyzed cation species has a charge that is equal to the cation valency.