Liquid Wax Esters Research Articles

Solvent-free synthesis of oleic acid-based wax esters using recyclable acidic deep eutectic solvent

Wax esters have been widely used in cosmetics and pharmaceutical products. Oleic acid wax esters can be used to replace spermaceti oil or jojoba oil. In this work, the acidic deep eutectic solvent (DES) composed of choline chloride and p-toluenesulfonic acid (1:4, mol/mol) was used as an efficient recyclable catalyst for the synthesis of oleic acid-based liquid wax esters through an esterification reaction. The esterification conversion of cetyl alcohol reached 99.1% under the following optimal reaction conditions: 5% DES as catalyst, molar ratio of fatty acid to alcohol of 1.3:1 and reaction temperature of 70 oC for 3h. The catalyst recovery experiments showed that this low-price acidic DES catalyst could be reused five times with uniform activity. Moreover, DES-catalyzed solvent-free esterification could be applied in the preparation of other oleic acid-based wax esters and excellent conversions (> 96%) could be obtained under such mild conditions.

Low-Temperature Esterification to Produce Oleic Acid-Based Wax Esters Catalyzed by 4-Dodecylbenzenesulfonic Acid

Synthesized oleic acid-based wax esters (e.g., cetyl oleate), which can replace spermaceti oil or jojoba oil, have been widely used in the cosmetic, pharmaceutical and other industries. In this work, 4-dodecylbenzenesulfonic acid (DBSA) has been successfully used as an efficient catalyst to synthesize oleic acid-based wax esters through esterification at 40 °C under solvent-free conditions. A 93.6% conversion rate of cetyl alcohol was obtained under optimal conditions: 10 mol% DBSA, a molar ratio of 1.3:1 oleic acid to alcohol, a reaction temperature 40 °C and a reaction time of 4 h. The effect of water content on esterification was investigated, and it was found that the inhibitory effect of water decreased significantly with increasing temperature. Moreover, DBSA-catalyzed esterification could be applied in the production of various oleic acid-based wax esters and excellent conversion (>90%) to esters was obtained under such mild conditions. DBSA-catalyzed low-temperature esterification is an efficient method for the production of liquid wax esters.

Synthesis, Characterization, Tribological and Rheological Properties of Oleyl Oleate Based Biolubricant

Oleyl oleate (liquid wax ester); is a principal component of sperm whale bubbler oil has an important industrial application such as cosmetic, pharmaceutical and biolubricant. In this work, synthesis of oleyl oleate was carried out through esterification between oleoyl alcohol and oleic acid using acidic heterogeneous catalyst, sodium hydrogen sulfate. About 95% of oleoyl oleate was produce at the optimal condition. The molecular structure of oleyl oleate has been confirmed by using FTIR, NMR and ESI-MS spectroscopies. The physicochemical properties of oleyl oleate were investigated. The results showed that the ester has pour point at -31 ± 1˚C, flash point at 320 ± 2˚C, viscosity index of 197.51 ± 1.4 and oxidative stability at 186.9 ˚C ± 1.8. Furthermore, tribological and rheological analysis of oleyl oleate were performed. Oleoyl oleate can be classified as a Newtonian fluid with having friction coefficient of 0.53 ± 0.08 at 100 ˚C operation condition. The presence of both ester functional group and long chain carbon moiety in oleyl oleate structure has a positive impact on wear protection thus plausible to be use as general purpose industrial biolubricant.

Enzymatic synthesis of coconut oil based wax esters by immobilized lipase EQ3 and commercial lipozyme RMIM

Liquid wax esters are widely used in cosmetic as well as pharmaceutical and other industries. The demand of organic and natural products is increasing nowadays. Coconut oil contains benefit fatty acids and has been mainly used for oil-based and moisturizer products. Liquid wax esters from coconut oil and unsaturated fatty alcohol can be synthesized by enzymatic reaction; and it is interesting for using as an alternative natural ingredient in these industries. Optimal condition for coconut oil based wax ester synthesis by immobilized lipase EQ3 was 10 U of enzyme, temperature at 30°C and molar ratio of coconut oil to oleyl alcohol at 1:3 (mol/mol) (0.33X) dissolved in isooctane for 12 h, while for Lipozyme RM IM optimal condition was 10 U of enzyme, temperature at 45°C and oil/alcohol molar ratio at 1:3 (0.33X) dissolved in isooctane for 3 h. Percentage of wax esters synthesized by both lipases reached more than 88%. Both immobilized lipases catalyzed high yield of wax esters within the 2nd batch; after that, the immobilized lipases showed reduced activity and synthesized < 60% of wax esters from the 3rd to 5th batch. The main composition of wax esters was ~ 48% oleyl laurate with 10% degradation at ~ 250°C. The liquid wax ester synthesis by commercial Lipozyme RM IM had higher effect than immobilized lipase EQ3, but both catalysts were stable within 2 batches in the optimum condition. The characteristic properties of wax esters showed potential for use as components in cosmetics and skin care products. Ungcharoenwiwat P, H-Kittikun A. Enzymatic synthesis of coconut oil based wax esters by immobilized lipase EQ3 and commercial lipozyme RMIM. Electron J Biotechnol 2020;47. https://doi.org/10.1016/j.ejbt.2020.06.005

Transcriptome Analysis of Jojoba (Simmondsia chinensis) during Seed Development and Liquid Wax Ester Biosynthesis.

Jojoba is one of the main two known plant source of natural liquid wax ester for use in various applications, including cosmetics, pharmaceuticals, and biofuel. Due to the lack of transcriptomic and genomic data on lipid biosynthesis and accumulation, molecular marker breeding has been used to improve jojoba oil production and quality. In the current study, the transcriptome of developing jojoba seeds was investigated using the Illunina NovaSeq 6000 system, 100 × 106 paired end reads, an average length of 100 bp, and a sequence depth of 12 Gb per sample. A total of 176,106 unigenes were detected with an average contig length of 201 bp. Gene Ontology (GO) showed that the detected unigenes were distributed in the three GO groups biological processes (BP, 5.53%), cellular component (CC, 6.06%), and molecular functions (MF, 5.88%) and distributed in 67 functional groups. The lipid biosynthesis pathway was established based on the expression of lipid biosynthesis genes, fatty acid (FA) biosynthesis, FA desaturation, FA elongation, fatty alcohol biosynthesis, triacylglycerol (TAG) biosynthesis, phospholipid metabolism, wax ester biosynthesis, and lipid transfer and storage genes. The detection of these categories of genes confirms the presence of an efficient lipid biosynthesis and accumulation system in developing jojoba seeds. The results of this study will significantly enhance the current understanding of wax ester biology in jojoba seeds and open new routes for the improvement of jojoba oil production and quality through biotechnology applications.

G_Fe3O4/Ag supporting Candida rugosa lipase for the “green” synthesis of pomegranate seed oil derived liquid wax esters

Wax esters were obtained through hydrolysis/esterification of pomegranate seed oil (PSO) with cetyl alcohol in the presence of Candida rugosa lipase (CRL) immobilized on G_Fe3O4/Ag@OA (oleic acid-coated magnetic nano-hybrid) catalyst. Lipase was immobilized successfully on the as-produced nanoparticles with an efficiency, depending on the operating conditions, up to ∼94%. The immobilized CRL shows very high activity on the respect of the free counterpart, which can be attributed to the lipase conformational structure modification related to interfacial activation. The immobilized lipase was used for the wax esters synthesis from PSO in a solvent-free system. A conversion of ∼83% was observed after 12 h alcohol/FFA molar ratio 1:1, it increases up to ∼95% with an alcohol/FFA molar ratio of 2:1. After the first three cycles of use, no significant reduction of the lipase activity was observed. Analyses of wax esters properties compared with jojoba oil evidence the feasibility of the produced wax ester for different applications. Iodine number of ∼209 (gI2/100 g oil) was obtained indicating a high degree of anti-oxidant and moisturizing properties.

SRAP and SSR marker-assisted genetic diversity, population structure analysis and sex identification in Jojoba (Simmondsia chinensis)

Simmondsia chinensis (Link) Schneider, commonly known as Jojoba is a woody, dioecious shrub, cultivated all over the globe mainly for its commercially important seed oil (liquid wax ester). Investigations were carried out to analyze genetic diversity and population structure of 57 Jojoba genotypes belonging to 3 different eco-geographical regions of India (Gujarat, Jodhpur, and Jaipur) employing sequence-related amplified polymorphism (SRAP) and simple sequence repeat (SSR) markers. SRAP markers produced higher mean values of polymorphic bands (6.22), polymorphism information content (PIC: 0.47), effective multiplex ration (EMR: 5.36) and marker index (MI: 2.59) compared to SSR markers (5.87, 0.38, 5.26 and 2.23 respectively). Higher % polymorphism (86.30%) and resolving power (RP: 8.76) were detected by SSR markers than SRAP markers (82.30% and 8.71 respectively). Total genetic diversity (Ht) and genetic diversity within populations (Hs) in Jojoba genotypes were found to be very high (0.47 and 0.45 respectively). AMOVA analysis also revealed higher genetic variation within populations (77%) than among populations (23%). Very low genetic differentiation (Gst: 0.04) and high gene flow (Nm: 10.57) among different populations were observed. The Jojoba population of Gujarat region was observed to be highly diverse (h: 0.48), and that of Jaipur was least polymorphic (h: 0.40). Jojoba male genotypes were found to be more polymorphic (h: 0.46) compared to females (h: 0.44). UPGMA, Neighbor-Joining tree, and population structure analysis divided Jojoba populations into two main clusters, first comprising of Gujarat and Jodhpur populations and second including Jaipur population. Genetic diversity in different Jojoba populations was found to be strongly negatively and significantly correlated with the longitude factor. For sex identification in Jojoba, one SRAP primer combination, 'Em14/Me10' amplified a DNA fragment of 396 bp specific to male genotypes of Jaipur population. This male-specific marker was further positively validated on different genotypes growing in Jodhpur and Gujarat regions and sequenced.

Synthesis of Bio‐Based Polyurethanes from Jojoba Oil

Jojoba grows easily in harsh conditions and is the only plant species known to use liquid wax esters as a primary seed storage reserve. Jojoba oil is composed by two mono unsaturated hydrocarbon chains linked by an ester moiety and represents 50% of the weight of seeds. Hence, this atypical oil is, for the first time, dedicated to the synthesis of innovative polymer materials. Novel partially biobased polyurethanes materials are obtained with various structures. New biobased diol is first achieved by addition of mercaptoethanol by thiol‐ene coupling on jojoba oil and characterized by 1H NMR and 13C NMR. The functionalized oil is used to synthesize polyurethane prepolymers by catalyst‐free reaction with various diisocyanates: 1,6‐hexamethylene diisocyanate and 4,4‐methylene diphenyl diisocyanate. After the addition of chain extenders, the obtained polyurethane materials are characterized by 1H NMR, TGA, DSC, and DMA analyses. Various PUs are obtained in terms of flexibility and thermal stability.Practical Applications: The synthesized jojoba oil‐based PUs exhibit a good flexibility. Hence, these biobased PUs could replace petroleum‐based polyurethanes in industry and particularly as coatings, binders or compounds for automotive and aircraft industries.Innovative greener polyurethanes are achieved from jojoba oil with one‐step thiol‐ene reaction and various diisocyanates.

Two bifunctional enzymes from the marine protist Thraustochytrium roseum: biochemical characterization of wax ester synthase/acyl-CoA:diacylglycerol acyltransferase activity catalyzing wax ester and triacylglycerol synthesis

BackgroundTriacylglycerols (TAGs) and wax esters (WEs) are important neutral lipids which serve as energy reservoir in some plants and microorganisms. In recent years, these biologically produced neutral lipids have been regarded as potential alternative energy sources for biofuel production because of the increased interest on developing renewable and environmentally benign alternatives for fossil fuels. In bacteria, the final step in TAG and WE biosynthetic pathway is catalyzed by wax ester synthase/acyl coenzyme A (acyl-CoA):diacylglycerol acyltransferase (WS/DGAT). This bifunctional WS/DGAT enzyme is also a key enzyme in biotechnological production of liquid WE via engineering of plants and microorganisms. To date, knowledge about this class of biologically and biotechnologically important enzymes is mainly from biochemical characterization of WS/DGATs from Arabidopsis, jojoba and some bacteria that can synthesize both TAGs and WEs intracellularly, whereas little is known about WS/DGATs from eukaryotic microorganisms.ResultsHere, we report the identification and characterization of two bifunctional WS/DGAT enzymes (designated TrWSD4 and TrWSD5) from the marine protist Thraustochytrium roseum. Both TrWSD4 and TrWSD5 comprise a WS-like acyl-CoA acyltransferase domain and the recombinant proteins purified from Escherichia coli Rosetta (DE3) have substantial WS and lower DGAT activity. They exhibit WS activity towards various-chain-length saturated and polyunsaturated acyl-CoAs and fatty alcohols ranging from C10 to C18. TrWSD4 displays WS activity with the lowest Km value of 0.14 μM and the highest kcat/Km value of 1.46 × 105 M−1 s−1 for lauroyl-CoA (C12:0) in the presence of 100 μM hexadecanol, while TrWSD5 exhibits WS activity with the lowest Km value of 0.96 μM and the highest kcat/Km value of 9.83 × 104 M−1 s−1 for decanoyl-CoA (C10:0) under the same reaction condition. Both WS/DGAT enzymes have the highest WS activity at 37 and 47 °C, and WS activity was greatly decreased when temperature exceeds 47 °C. TrWSD4 and TrWSD5 are insensitive to ionic strength and reduced WS activity was observed when salt concentration exceeded 800 mM. The potential of T. roseum WS/DGATs to establish novel process for biotechnological production of WEs was demonstrated by heterologous expression in recombinant yeast. Expression of either TrWSD4 or TrWSD5 in Saccharomyces cerevisiae quadruple mutant H1246, which is devoid of storage lipids, resulted in the accumulation of WEs, but not any detectable TAGs, indicating a predominant WS activity in yeast.ConclusionsThis study demonstrates both in vitro WS and DGAT activity of two T. roseum WS/DGATs, which were characterized as unspecific acyltransferases accepting a broad range of acyl-CoAs and fatty alcohols as substrates for WS activity but displaying substrate preference for medium-chain acyl-CoAs. In vivo characterization shows that these two WS/DGATs predominantly function as wax synthase and presents the feasibility for production of WEs by heterologous hosts.

Study of phase separation and anomalous molecular behavior of Jojoba oil using dielectric spectroscopy

Jojoba oil is composed almost entirely of liquid wax ester. Because growing conditions, harvesting and storage treatment can affect the composition of these waxes. Broadband dielectric spectroscopy and differential scanning calorimetry are complementary combined to study the molecular dynamics at the phase transitions, and in between, over temperatures range from −100 up to 100°C. Two different trends are found up and down a non-equilibrium or meta-stable state region. In addition, The rheological behavior and physicochemical properties of jojoba oil was studied, which revealed that the jojoba oil has a Newtonian behavior at low shear rate but it has non-Newtonian at high shear rate; it has also effective in controlling the oxidative deterioration. The chemical identification of jojoba oil using gas chromatography technique indicates that the main components were eicosenic and docosenic acids; it was concluded that the jojoba oil contained little or no glycerin and that most of its components fell in the chain-length range of C36–42.

Synthesis of oleyl oleate wax esters in Arabidopsis thaliana and Camelina sativa seed oil.

Seed oil composed of wax esters with long-chain monoenoic acyl moieties represents a high-value commodity for industry. Such plant-derived sperm oil-like liquid wax esters are biodegradable and can have excellent properties for lubrication. In addition, wax ester oil may represent a superior substrate for biodiesel production. In this study, we demonstrate that the low-input oil seed crop Camelina sativa can serve as a biotechnological platform for environmentally benign wax ester production. Two biosynthetic steps catalysed by a fatty alcohol-forming acyl-CoA reductase (FAR) and a wax ester synthase (WS) are sufficient to achieve wax ester accumulation from acyl-CoA substrates. To produce plant-derived sperm oil-like liquid wax esters, the WS from Mus musculus (MmWS) or Simmondsia chinensis (ScWS) were expressed in combination with the FAR from Mus musculus (MmFAR1) or Marinobacter aquaeolei (MaFAR) in seeds of Arabidopsis thaliana and Camelina sativa. The three analysed enzyme combinations Oleo3:mCherry:MmFAR1∆c/Oleo3:EYFP:MmWS, Oleo3:mCherry:MmFAR1∆c/ScWS and MaFAR/ScWS showed differences in the wax ester molecular species profiles and overall biosynthetic performance. By expressing MaFAR/ScWS in Arabidopsis or Camelina up to 59% or 21% of the seed oil TAGs were replaced by wax esters, respectively. This combination also yielded wax ester molecular species with highest content of monounsaturated acyl moieties. Expression of the enzyme combinations in the Arabidopsis fae1 fad2 mutant background high in oleic acid resulted in wax ester accumulation enriched in oleyl oleate (18:1/18:1 > 60%), suggesting that similar values may be obtained with a Camelina high oleic acid line.

Early Diagnosis of Sex in Jojoba, Simmondsia chinensis (Link) Schneider by Sequence Characterized Amplified Region Marker

Simmondsia chinensis (Link) Schneider is a dioecious shrub in which female plants are economically more important than the male plants, as seeds produced by the female plants store liquid wax ester that is extensively used in cosmetic industry. Sex of jojoba individuals can be determined only at flowering stage which comes after 3–4 years of seeding. Since, population of jojoba is male biased, so, to identify female plants at seedling stage, more reliable and robust male-specific sequence characterized amplified region marker was developed from male-specific inter-simple sequence repeat marker. During homology searching, no DNA sequence with significant similarity to male-specific inter-simple sequence repeat marker was found in non-redundant database of National Center for Biotechnology Information. Sequence characterized amplified region primer pair designed, based on the sequence of inter-simple sequence repeat marker, (GenBank accession no. HQ166029.1) amplified a fragment approx. 1000 bp in male plants only. This fragment was completely absent in female plants. Authentication of marker was done by using samples taken from two provinces of India.

Molecular Characterization of the Fatty Alcohol Oxidation Pathway for Wax-Ester Mobilization in Germinated Jojoba Seeds

Jojoba (Simmondsia chinensis) is the only plant species known to use liquid wax esters (WEs) as a primary seed storage reserve. Upon germination, WE hydrolysis releases very-long-chain fatty alcohols, which must be oxidized to fatty acids by the sequential action of a fatty alcohol oxidase (FAO) and a fatty aldehyde dehydrogenase (FADH) before they can be β-oxidized. Here, we describe the cloning and characterization of genes for each of these two activities. Jojoba FAO and FADH are 52% and 68% identical to Arabidopsis (Arabidopsis thaliana) FAO3 and ALDH3H1, respectively. The genes are expressed most strongly in the cotyledons of jojoba seedlings following germination, but transcripts can also be detected in vegetative tissues. Proteomic analysis indicated that the FAO and FADH proteins can be detected on wax bodies, but they localized to the endoplasmic reticulum when they were expressed as amino-terminal green fluorescent protein fusions in tobacco (Nicotiana tabacum) leaves. Recombinant jojoba FAO and FADH proteins are active on very-long-chain fatty alcohol and fatty aldehyde substrates, respectively, and have biochemical properties consistent with those previously reported in jojoba cotyledons. Coexpression of jojoba FAO and FADH in Arabidopsis enhanced the in vivo rate of fatty alcohol oxidation more than 4-fold. Taken together, our data suggest that jojoba FAO and FADH constitute the very-long-chain fatty alcohol oxidation pathway that is likely to be necessary for efficient WE mobilization following seed germination.

Influence of Temperature on the Phase Behaviors and Techniques Toward Formation of Palm Oil Esters Nanoemulsion

Palm oil esters (POEs), which are newly synthetic liquid wax esters with HLB value of 9.34, were proposed as a lipophilic phase for formation of nanoemulsion. Phase diagrams show domination of two-phase regions at all emulsification temperatures ranging from 30 to 80°C. Spontaneous and temperature-induced emulsification, high-shear and high pressure homogenization were utilized to form nanoemulsion. However, only high pressure homogenization successfully produced droplets sizes in the nano range. Thus, it was used to optimize the stability properties of POEs nanoemulsion. The manipulation of processing temperatures during the formation of emulsions could be used in lowering the droplets size of the emulsion.

Development of coating materials from liquid wax esters for wood top-based coating

Of late, UV-curable products are gaining attention in the wood industry because of the effectiveness and efficiency of this method. UV-curable surface coatings are widely used because of their excellent properties and because they are environmentally friendly products. In this study, immobilized Candida antarctica lipase B was used to catalyze formation of liquid wax esters, such as adipate esters, via a solvent-free process. The adipate esters formed were then used as UV-curable reactants in the wood coating formulations, consisting of epoxy acrylate, additives, and a photoinitiator. The performance of the products was evaluated by coating them onto glass tiles (using gel content, hardness, and scratch resistance tests) and wood panels (using adhesion, impact, and heat resistance tests). The coated film from this formulation performed well during the evaluation tests. The gel content exhibited more than 90% polymerization, while the pendulum hardness gave a value of 55.25%. Both analyses were significant in determining the effect of irradiation cycles. A scratch test was also carried out to verify the resistance of the coating. The maximum weight load which can be resisted by the wax esters formulation is 4.5 N.

Kinetics of Enzymatic Synthesis of Liquid Wax Ester from Oleic Acid and Oleyl Alcohol

The kinetics of wax ester synthesis from oleic acid and oleyl alcohol using immobilized lipase from Candida antartica as catalyst was studied with different types of impeller (Rushton turbine and AL-hydrofoil) to create different mixing conditions in 2l stirred tank reactor. The effects of catalyst concentration, reaction temperature, and impeller tip speed on the synthesis were also evaluated. Rushton turbine impeller exhibited highest conversion rate at lower impeller tip speed as compared to AL-hydrofoil impeller. A second-order reversible kinetic model from single progress curve for the prediction of fractional conversion at given reaction time was proposed and the corresponding kinetic parameter values were calculated by non-linear regression method. The results from the simulation using the proposed model showed satisfactory agreement with the experimental data. Activation energy shows a value of 21.77 Kcal/mol. The thermodynamic parameters of the process, enthalpy and entropy, were 21.15 Kcal/mol and 52.07 cal/mol.K, respectively.

Process improvement in the production of oleyl oleate, a liquid wax ester in stirred tank reactor

Lipase-catalyzed production of oleyl oleate, a liquid wax ester by esterification of oleic acid with oleyl alcohol was performed in 2 L stirred tank reactor (STR). Process improvement study in reactor operation was carried out in batch mode STR with single impeller mounted on the centrally located shaft. Rushton turbine impeller showed better performance in degree of mixing, as compared to AL Hydrofoil impeller, whereby a high Reynolds number of >104 was achieved at 400 rpm, which exhibit a turbulent flow pattern [1]. Homogenous enzyme particles suspension was obtained at lower impeller speed (≤200 rpm) by using AL Hydrofoil impeller. However, there was significant effect to the mixing improvement on the enzyme particles distribution by using 2 impellers system with spacing of 30 mm even at lower agitation speed (≤200 rpm). High stability of Novozym 435 was observed even in the presence of shear forces on the enzyme particles due to the mechanical agitation speed. Wax ester reaction mixture in STR follows Newtons’ law due to the linear relation between the shear stress (τ) and shear rate (dυ/dy) [2]. The process was successfully carried out to the highest amount of wax ester that can be produced in 2 L STR whereby, the production and productivity of oleyl oleate were improved from 295.39 g/L/h to 705.76 g/L/h and 310.16 g/h to 952.78 g/h, respectively.

High performance enzymatic synthesis of oleyl oleate using immobilised lipase from Candida antartica

High performance enzymatic synthesis of oleyl oleate, a liquid wax ester was carried out by lipase-catalysed esterification of oleic acid and oleyl alcohol. Various reaction parameters were optimised to obtain high yield of oleyl oleate. The optimum condition to produce oleyl oleate was reaction time; 5 min, organic solvents of log P ≥ 3.5, temperature; 40-50oC, amount of enzyme; 0.2-0.4 g and molar ratio of oleyl alcohol to oleic acid; 2:1. The operational stability of enzyme was maintained at >90% yield up to 9 cycles. Analysis of the yield of the product showed that at optimum conditions, >95% liquid wax esters were produced.

Optimisation study of large‐scale enzymatic synthesis of oleyl oleate, a liquid wax ester, by response surface methodology

AbstractAn optimisation study of the large‐scale enzymatic synthesis of a liquid wax ester from oleic acid and oleyl alcohol using Novozym 435 was carried out. Investigations were performed in batch mode with a stirred tank reactor (STR) with one multi‐bladed impeller. Response surface methodology (RSM) based on a five‐level, three‐variable central composite rotatable design (CCRD) was used to evaluate the interactive effects of various parameters. The parameters are amount of enzyme (A) (90–120 g), impeller speed (B) (100–400 rpm) and temperature (C) (40–60 °C). The optimum conditions derived via RSM at a fixed reaction time of 1 h were successfully optimised as A = 104 g, B = 388.0 rpm and C = 49.7 °C. The actual experimental yield was 96.7% under the optimum conditions, which compared well with the maximum predicted value of 97.6%. Copyright © 2005 Society of Chemical Industry

Phase Behavior of Oleyl Oleate with Nonionic Surfactants

Oleyl oleate (OE), a liquid wax ester, has been reported as a potential raw material for cosmetic and pharmaceutical uses but little is known about its phase behavior in ternary systems. Two types of nonionic surfactants were selected, namely, Tween‐60 (T60) and Span 20 (S20). Phase diagrams of OE/T60/water and OE/S20/water systems were constructed at 25.0±0.5°C. Ternary phase diagrams of OE/T60∶S20 (20∶80 and 60∶40)/water systems were then constructed at the same temperature. The ratios of 80∶20 and 60∶40 of T60∶S20 were selected due to different solubility points of the surfactants in water. The results showed that the oleyl oleate with mixed surfactants system, OE/T60∶S20 (20∶80 and 60∶40)/water, gave better performance than the individual surfactant systems. The high percent of T60 of 80∶20 in the T60∶S20 system contributes to enlargement of the isotropic region. In contrast, by increasing the percent of S20 of 60∶40 in T60∶S20 contributes to a larger liquid crystalline region.