Synthetic detergents from animal fats. VI. Polymerizable esters of alpha-sulfonated fatty acids

Summary Sodium allyl α-sulfopalmitate and sodium allyl α-sulfostearate, prepared by esterification of an α-sulfonated fatty acid with allyl alcohol, resemble sodium alkyl α-sulfopalmitates and stearates in surface-active and detergent properties and stability to hydrolysis. The allyl esters are easily converted to a new type of water-soluble polymer. The polymers may be thickening and emulsifying agents and may have other uses yet to be discovered. Presented at the meeting of American Oil Chemists’ Society, Philadelphia, Pa., October 10–12, 1955. A laboratory of the Eastern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Enzymatic synthesis of steryl esters of polyunsaturated fatty acids

Steryl esters of long-chain fatty acids have water-holding properties, and polyunsaturated fatty acids (PUFA) have various physiological functions. Because steryl ester of PUFA can be expected to have both features, we attempted to synthesize steryl esters of PUFA by enzymatic methods. Among lipases used, Pseudomonas lipase was the most effective for the synthesis of cholesteryl docosahexaenoate. When a mixture of cholesterol/docosahexaenoic acid (3:1, mol/mol), 30% water, and 3000 units/g of lipase was stirred at 40°C for 24 h, the esterification extent attained 89.5%. Under the same reaction conditions, cholesterol, cholestanol, and sitosterol were also esterified efficiently with docosahexaenoic, eicosapentaenoic, arachidonic, and γ-linolenic acids.     

Alpha sulfo fatty esters in biologically soft detergent formulations

Salts of α-sulfo tallow and coconut esters were subjected to river die-away, activated sludge and Warburg tests, and results show these derivatives to be biologically soft detergents with disappearance curves approximating those of the fatty alcohol sulfates. Selection of the proper fatty acid starting material, alcohol of esterification, and alkali for neutralization provides for a high degree of flexibility in tailor-making biologically soft surface active agents for a wide range of applications. Selected compounds have been found which exhibit remarkable foaming, lime soap dispersing, fabric and hard surface detergency, wetting and related surface-active properties. These properties allow the formulation of a variety of synthetic and soap-synthetic combinations. Primary emphasis is given to the presentation of data on surfactant formulation application studies. Salts of short chain alkyl esters of α-sulfo tallow acid are ideally suited for “combo” soap bar and built heavy-duty detergent applications. Salts of short chain alkyl esters of selected coconut fatty acids are uniquely suitable for light duty liquids, cosmetic and related surfactant applications. An improved process for the manufacture of these sulfo esters has been developed which produces high yield, high purity and light colored products, and which should provide for their acceptance on a large scale in the detergent field. Presented at the 37th Annual AOCS Meeting, Minneapolis, Minn. Oct. 1, 1963.     

Synthesis of alkyl glycoside fatty acid esters in non-aqueous media byCandida sp. lipase

Alkyl glycoside fatty acid esters were successfully synthesized by lipase-catalyzed transesterification of methyl glucoside, methyl glucoside, methyl galactoside and octyl glucoside with methyl oleate. The experiments were carried out in organic media with lipase enzymes fromCandida sp. as biocatalysts. Time course and the effects of temperature, solvent type, substrate concentration, added water and of immobilizedvs. nonimmobilized enzyme were studied. The optimal conditions for the enzymatic synthesis of alkyl glycoside fatty acid esters were: a molar ratio of alkyl glycoside and methyl oleate of 1:4, an immobilized lipase, SP382 fromCandida sp.; benzene/pyridine (2:1, vol/vol) with no added water; temperature, 55°C; reaction time, 48 h; and shaking at 200 rpm. Acceptable levels of oleic acid incorporation (58.6–100 mol%) onto the alkyl glycosides were achieved.     

α-Sulfonated fatty acid esters: I. Structural effects of sodium α-sulfonated fatty acid higher alcohol esters on surface-active properties and emulsification ability

The surface-active properties and emulsification ability of sodium α-sulfonated fatty acid esters, C_mH_2m+1CH-(SO₃Na)COOC_nH_2n+1, were studied as a function of the hydrophobic alkyl chainlength in the fatty acid (m=8−16) and the alcohol (n=8−18). As a result, it was discovered that sodium α-sulfonated fatty acid esters have a structural effect on the Krafft point different from that of amphiphiles with short alkyl chains. Moreover, some of the α-sulfonated fatty acid esters have quite low interfacial tensions, as well as non-foaming properties, which depend upon the total (m+n) number of carbon atoms in the alkyl chains.     

Lipase-mediated synthesis of alkyl ricinoleates and 12-hydroxy stearates and evaluation of the surfactant properties of their sulfated sodium salts

An efficient and simple lipase-mediated synthesis of alkyl ricinoleates and 12-hydroxy stearates was performed by transesterification of methyl ricinoleate/12-hydroxy stearate and various alcohols in a solvent-free system without estolide formation. The reaction conditions were optimized by varying the temperature, pressure, and dosage of lipase. Sulfates of alkyl ricinoleates/12-hydroxy stearates were evaluated for surfactant properties such as surface tension, critical micelle concentration, emulsifying properties, foaming power, and calcium tolerance. The surfactant properties of sulfated alkyl ricinoleates were found to be superior to the sulfated alkyl 12-hydroxy series. The surfactant properties of the above two series of compounds were then compared with sodium dodecyl sulfate, and the properties of sulfated dodecyl ricinoleate and sulfated dodecyl 12-hydroxy stearate were found to be comparable with sodium dodecyl sulfate.     

Comparison of bio- and autocatalytic esterification of oils using mono- and diglycerides

The purpose of this study was to investigate enzymatic and autocatalytic esterification of FFA in rice bran oil (RBO), palm oil (PO), and palm kernel oil (PKO), using MG and DG as esterifying agents. The reactions were carried out at low pressure (4–6 mm Hg) either in the absence of any added catalyst at high temperature (210–230°C) or in the presence of Mucor miehei lipase at low temperature (60°C). The reactions were carried out using different concentrations of MG, and the optimal FFA/MG ratio and time were 2∶1 (molar) and 6 h, respectively, in both auto- and enzyme-catalyzed processes. With DG as the esterifying agent in the autocatalytic process, the optimal temperature was 220°C, and the optimal FFA/DG ratio was 1∶1.25. For both MG and DG, the enzymatic process was more effective in reducing FFA and produced more favorable levels of unsaponifiable matter and color in the final product. The PV of the final products were also lower (1.8–2.9 mequiv/kg) by using the enzymatic process. To produce edible-grade oil, a single deodorization step would be required after enzymatic esterification; whereas, alkali refining, bleaching, and deodorization would be required after autocatalytic treatment.     

Enzymatic production of fatty acid alkyl esters with a lipase preparation from Candida sp. 99‐125

A lipase preparation developed from Candida sp. 99‐125 was used for fatty acid alkyl ester synthesis by both enzymatic esterification of fatty acids, and transesterification of oils and fats. The lipase preparation was chosen based on screening of lipases from commercial sources as well as those produced in the laboratory. The effects of enzyme dosage, solvent types, water absorbent additions, inhibition of short‐chain alcohols, alcohol and acid types, molar ratio of substrates, and reusability of the lipase preparation in esterification were studied. Degree of esterification between oleic acid and methanol under optimal conditions reached 92%. Purity of the methyl ester after washing with water and distillation was 98%. Half‐life of the lipase preparation was calculated to be approximately 340 h. For transesterification of rapeseed oil with the same lipase preparation, the amount of methanol and mode of methanol addition to the reaction were also conducted. Transesterification of the oil with stepwise methanol addition reached 83% after 36 h reaction time.     

Utilization of acid oils in making surface-active compounds by lipase-catalyzed hydrolysis and esterification reactions

Nonionic surface-active molecules were made from acid oils such as mustard, sunflower, rice bran, soybean, coconut, and polyethylene glycols (PEG) of varying molecular weights (200, 300, 400, 600), using processes based on lipasecatalyzed hydrolysis with Candida cylindracea lipase and esterification with Mucor miehei lipase. Both the PEG molecular weight and the acid oil influence the yield of ester. Molar concentration of reatants also influences the rate and yield of ester. Surface tension values of ester products reveal that maximal lowering of surface tension of water occurs in the case of PEG 600 and coconut acid oil ester. This work demonstrates an important technological advance in the synthesis of nonionic surfactants of the alkyl ethoxylate type from a variety of acid seed oils in high yields by using lipase technology involving first hydrolysis and then esterification with another lipase.     

Lactic Acid Extraction and Enzymatic Esterification for the Ethyl Lactate Production from Rice

Polylactic acid has received much attention because of its biodegradable characteristics. However, to produce the polylactic acid, enormous energy is required at the current purification processes developed up to now. In this work, in order to reduce energy consumption, we proposed a novel purification method which combines lactic acid extraction and enzyme esterification instead of the dehydration and the chemical esterification which are conventionally used. As a result, the new purification method is found to be excellent as the solvents used in this work. It revealed that some solvents (diethyl ether, tert-butyl methyl ether, and methy isobuthyl ketone) have excellent abilities for both lactic acid extraction and enzymatic esterification.     

Syntheses and characterization of xylan esters

A series of low-molecular weight and high-molecular weight xylan esters with different alkyl chain lengths (C2–C12) were synthesized by heterogeneous and homogeneous reactions, respectively. Structure elucidation of these xylan esters was obtained by NMR analysis. The solubility of xylan in CHCl₃ improved after esterification. DSC results did not show a melting peak for all samples. However, WAXD diffractograms show the presence of diffraction peaks. The proposed structural model for xylan ester films is presented. TGA suggested that the thermal stability of xylan increased after esterification. Xylan esters with longer alkyl chains had higher decomposition temperatures. The mechanical properties of the xylan esters were dependent on the alkyl chain length. The tensile strength and elongation at break of these xylan esters ranged from 8 to 29 MPa and from 19 to 44%, respectively. Xylan esters in HFIP can be electrospun into nanofibers.     

Enzymatic synthesis of l-menthyl esters in organic solvent-free system

l-Menthol has been widely used as a food additive and an ingredient of cosmetics, and it is esterified to moderate the strong flavor. We attempted esterification of l-menthol with long-chain unsaturated fatty acid in an organic solvent-free enzymatic system. Commercially available lipases were screened, and Candida rugosa lipase was selected as a catalyst. Several factors affecting the esterification were investigated, and the reaction conditions were determined as follows: A reaction mixture of l-menthol/fatty acid (1:3, mol/mol), 30% water, and 700 units of the lipase per gram of reaction mixture was incubated at 30°C with stirring. After 24 h under these conditions, the esterification extents of l-menthol with oleic, linoleic, and α-linolenic acids reached 96, 88, and 95%, respectively. The structure of the esterified product was confirmed by mass, infrared, and nuclear magnetic resonance spectroscopies. Bacause Candida lipase acted strongly on l-menthol and very weakly on d-menthol, dl-menthol was esterified with oleic acid under the same conditions. The reaction showed high enantioselectivity; the enantiomeric ratio (E) was 31, and enantiomeric excess (ee) of l-menthyl oleate reached 88% after 32 h.     

Enzyme‐catalyzed regioselective synthesis of sucrose‐based esters

Sucrose‐based esters are nonionic biosurfactants, which can be synthesized from the enzyme‐catalyzed esterification/transesterification of sucrose. The multi‐hydroxyl groups of sucrose and the immiscibility of sucrose with the acyl donors are the main bottlenecks in obtaining highly regioselective sucrose‐based esters. In this mini‐review, the effects of reaction conditions such as biocatalysts, design of solvent systems used as reaction media, modification and denaturation of substrates, and coupling with external auxiliary physical fields such as microwave irradiation and ultrasonic waves on the yield of sucrose esters and regioselectivity of products are highlighted. The existing problems in the field of enzymatic synthesis of sucrose esters as well as its future perspectives were pointed out. Copyright © 2011 Society of Chemical Industry     

Lipase‐catalyzed synthesis of quinate and glucuronate fatty esters

The lipase‐catalyzed synthesis of fatty alcohol esters of quinic and glucuronic acid was investigated. The results showed that although a direct esterification process was possible, a strategy involving short‐chain alkyl ester intermediates was advantageous. 2‐Methyl‐2‐butanol was chosen as solvent and parameters such as substrate ratios and concentrations were optimized. Octyl, decyl and hexadecyl esters of quinic and glucuronic acids could be obtained with this process. However, reaction rates were rather slow and it could be shown that the completely chemically catalyzed synthesis of the same products using ion exchange resins was advantageous.     

Enzymatic fractionation of fatty acids: Enrichment of γ-linolenic acid and docosahexaenoic acid by selective esterification catalyzed by lipases

Immobilized lipase preparations from seedlings of rape (Brassica napus L.) andMucor miehei (lipozyme) used as biocatalysts in esterification and hydrolysis reactions discriminate strongly against γ-linolenic and docosahexaenoic acids/acyl moieties. Utilizing this property, γ-linolenic acid contained in fatty acids of evening primrose oil has been enriched seven to nine-fold, from 9.5 to almost 85% by selective esterification of the other fatty acids with butanol. Similarly, docosahexaenoic acid of cod liver oil has been enriched four to five-fold, from 9.4 to 45% by selective esterification of fatty acids (other than docosahexaenoic acid) with butanol. As long as the reaction is stopped before reaching equilibrium, very little of either γ-linolenic acid or docosahexaenoic acid are converted to butyl esters, which results in high yields of these acids in the unesterified fatty acid fraction.     

Enzyme‐catalyzed regioselective synthesis of sugar esters and related compounds

In this review, a comprehensive and illustrative survey is made of the regioselective synthesis of esters of sugars and related compounds using lipases. The main emphasis has been given to the screening and use of commercially available lipases for the enzymatic esterification of neutral monosaccharides, disaccharides, sugar alcohols and their selected ether and ester derivatives. The effect of solvents and solubilizing agents in improving the yields of the resultant sugar fatty acid esters has been incorporated. Further, solvent‐free esterification with molten fatty acids, use of ionic liquids and microwave radiations for improvement in the methodology have also been discussed. Copyright © 2006 Society of Chemical Industry     

Lipase-catalyzed synthesis and properties of estolides and their esters

Eight lipases were screened for their ability to synthesize estolides from a mixture that contained lesquerolic (14-hydroxy-11-eicosenoic) acid and octadecenoic acid. With the exception ofAspergillus niger lipase, all 1,3-specific enzymes (fromRhizopus arrhizus andRhizomucor miehei lipases) were unable to synthesize estolides.Candida rugosa andGeotrichum lipases catalyzed estolide formation at >40% yield, with >80% of the estolide formed being monoestolide from one lesquerolic and one octadecenoic acyl group:Pseudomonas sp. lipase synthesized estolides at 62% yield, but the product mixture contained significant amounts of monoestolide with two lesquerolic acyl groups as well as diestolide. ImmobilizedR. miehei lipase was chosen to catalyze the esterification of mono-and polyestolide, derived synthetically from oleic acid, with fatty alcohols or α,ω-diols. Yields were >95% for fatty alcohol reactions and >60% for diol reactions. In addition, the estolide linkage remained intact through the course of the esterification process. Esterification of estolides improved the estolide’s properties—for example, lower viscosity and higher viscosity index—but slightly raised the melting point. Estolides and, particularly, estolide esters may be suitable as lubricants or lubricant additives.     

<Emphasis Type="Italic">In situ</Emphasis> alkaline transesterification: An effective method for the production of fatty acid esters from vegetable oils

The production of simple alkyl FA esters by direct alkali-catalyzed in situ transesterification of the acylglycerols (AG) in soybeans was examined. Initial experiments demonstrated that the lipid in commercially produced soy flakes was readily transesterified during agitation at 60°C in sealed containers of alcoholic NaOH. Methyl, ethyl, and isopropyl alcohols readily participated in the reaction, suggesting that the phenomenon is a general one. Statistical experimental design methods and response surface regression analysis were used to optimize reaction conditions, using methanol as alcohol. At 60°C, the highest yields of methyl ester with minimal contamination by FFA and AG were predicted at a molar ratio of methanol/AG/NaOH of 226∶1∶1.6 with an approximately 8-h incubation. An increase in the amount of methanol, coupled with a reduced alkali concentration, also gave high ester yields with low FFA and AG contamination. The reaction also proceeded well at 23°C (room temperature), giving higher predicted ester yields than at 60°C. At room temperature, maximal esterification was predicted at a molar ratio of 543∶1∶2.0 for methanol/AG/NaOH, again in 8 h. Of the lipid in soy flakes, 95% was removed under such conditions. The amount of FAME recovered after in situ transesterification corresponded to 84% of this solubilized lipid. Given the 95% removal of lipid from the soy flakes and an 84% efficiency of conversion of this solubilized lipid to FAME, one calculates an overall transesterification efficiency of 80%. The FAME fraction contained only 0.72% (mass basis) FFA and no AG. Of the glycerol released by transesterification, 93% was located in the alcoholic ester phase and 75 was on the post-transesterification flakes.     

Enrichment of polyunsaturated fatty acids from sardine cannery effluents by enzymatic selective esterification

The sardine canning industry produces vast quantities of effluents that need expensive reprocessing. Their oily component contains valuable n−3 polyunsaturated fatty acids, namely EPA (5,8,11,14,17-eicosapentaenoic acid) and DHA (7,10,13, 16,19-docosahexaenoic acid), up to 10% each. Our aim was to develop a process allowing the recovery of these fatty acids. After removing solid particles, proteins, and peptides from the crude effluent, the obtained oil was hydrolyzed. EPA and DHA were enriched from the recovered free fatty acid fraction by selective enzymatic esterification. Lipases were used as biocatalysts: Lipozyme^TM allowed up to 80% DHA enrichment but gave no EPA enrichment. By immobilizing Candida rugosa lipase on Amberlite IRC50 cation-exchange resin, a 30% EPA enrichment was obtained.     

Rapid synthesis of fatty acid esters for use as potential food flavors

Lipase-catalyzed esterification has been performed in hexane to generate novel mixtures of fatty acid esters from specially chosen combinations of fatty acids and alcohols. By varying the alcohol and enzyme compositions in the enzymatic reactions, different ester mixtures were produced, which were further purified and analyzed for ester composition by gas chromatography-mass spectrometry. Depending on the combination of alcohols and enzymes used, the final ester mixture exhibited significant compositional variation. These mixtures could be manipulated at the synthesis step, thereby enabling a high degree of product control. Such manipulation over enzyme-catalyzed ester synthesis in mixtures may be useful in the preparation of ester flavors for use in the food industry.