Long-chain Fatty Acid Esters Research Articles

ChemInform Abstract: Metathesis of Functionalized Acyclic Olefins

Abstract The metathesis of functionally substituted olefins, i.e olefins containing one or more heteroatoms, affords interesting prospects in the synthesis of valuable organic products. Since the first report on the successful metathesis of certain functional olefins, viz. longchain fatty acid esters, much research has been done into the possibilities of this reaction. It appears that many types of functionalized olefins undergo metathesis in the presence of a suitable catalyst. Despite the fact that many metathesis catalysts are inactive, interesting results have been obtained in the past with two catalyst systems, viz. the homogeneous system WCl6-Sn(CH3)4 and the heterogeneous system Re2O7/Al2O3-Sn(CH3)4. The scope of the reaction of functionalized olefins has been studied for a number of groups. The functional groups suited for metathesis include -COOR, -OCOR, -COR, -OR, -CN, -OSiR3, -Cl etc. Unsaturated carboxylic acids and alcohols can be metathesized by introducing a protecting group, e.g. a trimethylsilyl group. New homogeneous catalyst systems developed in recent years are nearly all based on tungsten compounds. Generally, however, the heterogeneous rhenium-based catalyst system turns out to be more attractive. The catalyst is active even at room temperature and can be recovered easily. In addition it is active towards certain compounds, especially allyl compounds, that are inactive with the tungsten catalysts. An important development was the access to the metathesis of unsaturated nitriles. Here, the system Re2O7/Al2O3-SnR4 in particular gives good results. Higher activities than those observed for the Re2O7/ Al2O3 catalysts can be achieved using modified rhenium catalysts. Thus, noteworthy results were obtained when a third metal oxide was incorporated and when a different support was used, e.g. silica-alumina. These developments are the subject of further study at the present time and will lead to catalysts with activities of practical interest.

High-cell-density batch fermentation of Rhodococcus opacus PD630 using a high glucose concentration for triacylglycerol production

Biodiesel, monoalkyl esters of long-chain fatty acids with short-chain alcohols derived from triacylglycerols (TAGs), can be produced from renewable biomass sources. Recently, there has been interest in producing microbial oils from oleaginous microorganisms. Rhodococcus opacus PD630 is known to accumulate large amounts of TAGs. Following on these earlier works we demonstrate that R. opacus PD630 has the uncommon capacity to grow in defined media supplemented with glucose at a concentration of 300 g l −1 during batch-culture fermentations. We found that we could significantly increase concentrations of both glucose and (NH 4) 2SO 4 in the production medium resulting in a dramatic increase in fatty acid production when pH was controlled. We describe the experimental design protocol used to achieve the culture conditions necessary to obtain both high-cell-density and TAG accumulation; specifically, we describe the importance of the C/N ratio of the medium composition. Our bioprocess results demonstrate that R. opacus PD630 grown in batch-culture with an optimal production medium containing 240 g l −1 glucose and 13.45 g l −1 (NH 4) 2SO 4 (C/N of 17.8) yields 77.6 g l −1 of cell dry weight composed of approximately 38% TAGs indicating that this strain holds great potential as a future source of industrial biodiesel on starchy cellulosic feedstocks that are glucose polymers.

Burning characteristics of palm-oil biodiesel under long-term storage conditions

The influences of oxidative variables on the burning characteristics of palm-oil biodiesel were investigated experimentally in this study. Biodiesel, which is composed of monoalkyl esters of long-chain fatty acids, generally has an inferior oxidative stability than petrodiesel. Hence, the long-term oxidative stability of palm-oil biodiesel has received much industry attention because it is used widely as an alternative to pure diesel fuel. Palm-oil biodiesel was stored in a constant-temperature water bath at either 60 °C or 20 °C continuously for 3000 h to observe the variation in its oxidative degradation and burning characteristics, such as carbon residue and the amount of heat released, with storage time. The effect of antioxidant addition on the burning characteristics was also investigated. The experimental results reveal that the palm-oil biodiesel suffered greater oxidative degradation at higher storage temperatures and in the absence of an antioxidant, which resulted in a faster decrease in the amount of heat released as the storage time elapsed. The addition of the chain-breaker antioxidant BHT effectively broke the peroxidation reaction mechanism and hence significantly retarded the decrease in heat release. The oxidative stability of the palm-oil biodiesel was worst at a higher storage temperature, a longer storage time, and in the absence of an antioxidant, which caused the more extensive formation of sediments of oxidative products and hence a larger carbon residue after burning. The greater oxidative degradation also caused the more extensive decomposition of unsaturated fatty acids into oxidative products, which decreased the flash point and the cetane index of the fuel.

Membrane environment and endocannabinoid signaling

Membrane environment and endocannabinoid signaling

Synthesis of N-Activated Aziridines of Long-Chain Fatty Acid Esters

An alternative one-step synthesis of N-activated aziridines of naturally occurring fatty acid esters from olive oil and sunflower oil has been achieved. N-Tosylaziridine derivatives were obtained in yields ranging from 8.5 to 97.5%. Methyl cis- and trans-8-(3-octyl-1-tosylaziridin-2-yl)octanoates were formed with transesterified olive oil as substrate, and methyl cis- and trans-(Z)-11-(3-pentyl-1-tosylaziridin-2-yl)undec-9-enoates were produced when transesterified sunflower oil was the substrate.

Sarcolemmal fatty acid uptake vs. mitochondrial β-oxidation as target to regress cardiac insulin resistanceThis paper is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process.

Cardiomyopathy and heart failure are frequent comorbid conditions in type-2 diabetic patients. However, it has become increasingly evident that insulin resistance, type-2 diabetes, and cardiomyopathy are not independent variables, and are linked through changes in metabolism. Specifically, elevated intracellular levels of long-chain fatty acid (LCFA) metabolites are a central feature in the development of cardiac insulin resistance, and their prolonged accumulation is an important cause of heart failure. In the insulin-resistant heart, the abundance of the LCFA transporters CD36 and FABPpm at the sarcolemma of cardiac myocytes appears to be markedly increased. Because circulating LCFA levels are increased in insulin resistance, the cardiac LCFA metabolizing machinery is confronted with drastic increases in substrate supply. Indeed, LCFA esterification into triacylglycerol and other lipid intermediates is increased, as is beta-oxidation and reactive oxygen species production. Therapeutic strategies to normalize the cardiac LCFA flux would be most successful when the target is the rate-limiting step in cardiac LCFA utilization. Carnitine palmitoyltransferase (CPT)-I has long been considered to be this rate-limiting site and, accordingly, pharmacological inhibition of CPT-I, or beta-oxidation enzymes, has been proposed as an insulin-resistance-antagonizing strategy. However, recent evidence indicates that, instead, sarcolemmal LCFA transport mediated by CD36 in concert with FABPpm provides a major site of flux control. In this review, it is proposed that a pharmacologically imposed net internalization of CD36 and FABPpm is the preferable strategy to limit LCFA entry and accumulation of LCFA metabolites, to regress cardiac insulin resistance and, eventually, prevent diabetic heart failure.

Preparation and properties of sulfonated carbon–silica composites from sucrose dispersed on MCM-48

Abstract Sulfonated carbon–silica composites with surface areas of over 600 m 2 /g and pore sizes of 1.5–2.2 nm were prepared by incompletely carbonizing sucrose dispersed on MCM-48 and sulfonating the obtained carbon/MCM-48 composites. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, N 2 adsorption, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The catalytic activities of these composites were studied in the esterification of acetic acid with n-butyl alcohol. The pore sizes and catalytic activities of the sulfonated carbon–silica composites were adjustable by changing the amount of sucrose loadings, and the composites exhibited enhanced hydrothermal stability and amphiphilic property. When the sucrose loading was close to the monolayer dispersion capacity of sucrose on MCM-48 (1.1 g sucrose/g MCM-48), the resulting sulfonated carbon–silica composites exhibited surface areas of 700–724 m 2 /g and n-butyl acetate yields of 90.4–98.7% in the esterification of acetic acid with n-butyl alcohol. They also showed obvious catalytic activities in the esterification of long-chain fatty acids with ethanol. The expensive MCM-48 could be easily recycled by simply calcining the sulfonated carbon–silica composites in air.

Distinct Structural Elements Dictate the Specificity of the Type III Pentaketide Synthase from Neurospora crassa

The fungal type III polyketide synthase 2'-oxoalkylresorcylic acid synthase (ORAS) primes with a range of acyl-Coenzyme A thioesters (C4-C20) and extends using malonyl-Coenzyme A to produce pyrones, resorcinols, and resorcylic acids. To gain insight into this unusual substrate specificity and product profile, we have determined the crystal structures of ORAS to 1.75 A resolution, the Phe-252-->Gly site-directed mutant to 2.1 A resolution, and a binary complex of ORAS with eicosanoic acid to 2.0 A resolution. The structures reveal a distinct rearrangement of structural elements near the active site that allows accommodation of long-chain fatty acid esters and a reorientation of the gating mechanism that controls cyclization and polyketide chain length. The roles of these structural elements are further elucidated by characterization of various structure-based site-directed variants. These studies establish an unexpected plasticity to the PKS fold, unanticipated from structural studies of other members of this enzyme family.

Mediation of oviposition responses in the malaria mosquito Anopheles stephensi Liston by certain fatty acid esters

The chemical factors involved in oviposition site selection by mosquitoes have become the focus of interest in recent years, and considerable attention is paid to the chemical cues influencing mosquito oviposition. Studies on synthetic oviposition attractants/repellents of long-chain fatty acid esters against Anopheles stephensi are limited. Screening and identification of chemicals which potentially attract/repel the gravid females to/or from oviposition site could be exploited for eco-friendly mosquito management strategies. The ester compounds demonstrated their ability to repel and attract the gravid A. stephensi females in the treated substrates. Significant level of concentration-dependent negative oviposition response of mosquitoes to octadecyl propanoate, heptadecyl butanoate, hexadecyl pentanoate, and tetradecyl heptanoate were observed. In contrast, decyl undecanoate, nonyl dodecanoate, pentyl hexadecanoate, and propyl octadecanoate elicited concentration-dependent positive oviposition responses from the gravid mosquitoes. Forcing a female to retain her eggs due to unavailability of a suitable oviposition site and attracting them to lay the eggs in a baited ovitraps shall ensure effective control of mosquito breeding and population buildup because the oviposition bioassay target the most susceptible stage of an insect life cycle. Treating relatively smaller natural breeding sites with an effective repellent and placing ovitraps containing an attractant in combination with insect-growth regulator (IGR)/insecticide would be a promising method of mosquito management.

Oviposition responses of Aedes aegypti and Aedes albopictus to certain fatty acid esters

Laboratory studies were carried out to observe the oviposition responses of Aedes aegypti (L.) and Aedes albopictus (Skuse) to several C21 fatty acid esters. The oviposition activity of these dengue and chikungunya vectors to the long-chain fatty acid esters of C21 length have not been reported earlier. From the multiple choice experiments on oviposition activity in standard mosquito cages, it was observed that compounds hexadecyl pentanoate, tetradecyl heptanoate and tridecyl octanoate presented significant oviposition repellent activity against the two mosquito species, while one compound propyl octadecanoate was found to attract A. aegypti to the treated oviposition substrate at 1- and 10-ppm concentrations. The possible utilization of these esters in integrated vector management is discussed.

Aggregate formation in the intercalation of long-chain fatty acid esters into liposomes

Various hydrophobic benzenediacetic esters, the corresponding benzenedipropionic esters, and branched alkyl esters were intercalated into DMPC liposomes, where the molar ratio ( n/ n) of ester:DMPC was 1:5. In the case of the very long-chain derivatives, double carbonyl peaks were observed in the 13C NMR spectrum. This doubling phenomenon was observed only for the carbonyl peaks, whose chemical shift is most sensitive to solvent polarity, and disappeared when the ester:DMPC molar ratio drops below 1:15. This doubling reflects the presence of two populations in these samples: one group includes those molecules which are intercalated within the liposome and feel the polarity corresponding to the liposomal microenvironment; the other consists of aggregates of these long-chain derivatives located in the extra-liposomal aqueous phase.

Oxidative and Thermal Instability of Biodiesel

The term biodiesel means the monoalkyl esters of long-chain fatty acids made from biolipids such as vegetable oils, animal fats, or algae. Chemical reactivity of biodiesel can be divided into oxidative and thermal instability. Many of the biolipids contain polyunsaturated fatty acid chains in that their double bonds have high chemical reactivity. The oxidative and thermal degradation occurs on the double bonds of unsaturated aliphatic carbons chains in biolipids. Oxidation of biodiesel results in the formation of hydroperoxides. The formation of the hydroperoxide follows a well-known peroxidation chain mechanism. The olefinic unsaturated fatty acid oxidation is a multi-step reaction process where primary products (conjugated diene hydroperoxides) decompose and chemically interact with each other to form numerous secondary oxidation products. The oxidative and thermal instability are determined by the amount and configuration of the olefinic unsaturation on the fatty acid chains. The viscosity of biodiesel increases with the increase of thermal degradation degree due to the trans-isomer formation on double bonds. The decomposition of biodiesel and its corresponding fatty acids linearly increases from 293 K to 625 K. The densities of biodiesel fuels decreased linearly with temperatures from 293 K to 575 K. The combustion heat of biodiesel partially decreases with the increase of thermal degradation degree.

Lower Emissions from Biodiesel Combustion

Biodiesel has been defined as the monoalkyl esters of long-chain fatty acids derived from renewable feedstocks, such as vegetable oils or animal fats, for use in compression-ignition (diesel) engines. Biodiesel has become more attractive because of its environmental benefits and the fact that it is made from renewable resources. Biodiesel is the first and only alternative fuel to petroleum diesel to have a complete evaluation of emission results. The emission-forming gasses, such as carbon dioxide and carbon monoxide from combustion of biodiesel hydrocarbons, generally are less than diesel fuel. Sulfur emissions are essentially eliminated with pure biodiesel. The exhaust emissions of sulfur oxides and sulfates from biodiesel were essentially eliminated compared to diesel. The smog-forming potential of biodiesel hydrocarbons is less than diesel fuel. The ozone-forming potential of the speciated hydrocarbon emissions was 50% less than that measured for diesel fuel.

MCM-48 Supported Tungstophosphoric Acid: An Efficient Catalyst for the Esterification of Long-Chain Fatty Acids and Alcohols in Supercritical Carbon Dioxide

Tungstophosphoric acid (HPW) and MCM-48-supported HPW catalysts are potential catalysts for the esterification of long-chain fatty acids and alcohols in supercritical CO2 medium even at low temperature (100 °C) and a short reaction period (6 h). The high performances of HPW in sc-CO2 medium are due to the effective mass transfer of reactants and products for the catalysis under the conditions. The yields of esters were enhanced with the increase in the chain length of acids and alcohols in the esterification in sc-CO2 medium. The MCM-48-supported HPW catalysts were active even after several recycle experiments.

A New Lipase Isolated from Oleaginous Seeds from Pachira aquatica (Bombacaceae)

A new lipase from seeds of Pachira aquatica was purified to homogeneity by SDS-PAGE obtaining an enzyme with a molecular weight of approximately 55 kDa. The purified lipase exhibited maximum activity at 40 degrees C and pH 8.0, for an incubation time of 90 min. Concerning temperature stability, at the range from 4 to 50 degrees C, it retained approximately 47% of its original activity for 3 h. The enzyme activity increased in the presence of Ca(++) and Mg(++), but was inhibited by Hg(++), Mn(++), Zn(++), Al(+++) and various oxidizing and reducing agents. The lipase was highly stable in the presence of organic solvents, and its activity was stimulated by methanol. The values of K(m) and V(max) were 1.65 mM and 37.3 micromol mL(-1) min(-1), respectively, using p-nitrophenylacetate as substrate. The enzyme showed preference for esters of long-chain fatty acids, but demonstrated significant activity against a wide range of substrates.

Improved Method for Efficient Production of Biodiesel from Palm Oil

Biodiesel (methyl esters of long-chain fatty acids) can be produced by methanolysis of vegetable oils using lipase as a biocatalyst. However, the lipase, such as immobilized Candida antarctica lipase B (Novozym 435), is poisoned as a result of the contact with insoluble methanol, reducing the lipase activity. To minimize the problem, a salt-solution-based controlled release system for methanol is developed. The developed method can easily minimize the problem by dissolving methanol in the salt solution and keeping an acceptable methanol concentration in vegetable oil, thereby increasing the lipase activity. The results of methanolysis of palm oil in the salt-solution-based methanol release system are compared to those in a salt-solution-free system, where methanol is added by the traditional method of three successive additions of methanol. The maximum biodiesel yields in both systems are the same (97%), but methanolysis in the developed method progresses 4-fold faster than that in the traditional method. It is found that a LiCl-saturated solution stabilizes Novozym 435 against heat-induced inactivation. The results suggest that the salt-solution-based methanol release system can be an acceptable substitution for the traditional method and provides an efficient method for biodiesel production.

Cardiac contractile dysfunction in insulin-resistant rats fed a high-fat diet is associated with elevated CD36-mediated fatty acid uptake and esterification

Aims/hypothesisChanges in cardiac substrate utilisation leading to altered energy metabolism may underlie the development of diabetic cardiomyopathy. We studied cardiomyocyte substrate uptake and utilisation and the role of the fatty acid translocase CD36 in relation to in vivo cardiac function in rats fed a high-fat diet (HFD).MethodsRats were exposed to an HFD or a low-fat diet (LFD). In vivo cardiac function was monitored by echocardiography. Substrate uptake and utilisation were determined in isolated cardiomyocytes.ResultsFeeding an HFD for 8 weeks induced left ventricular dilation in the systolic phase and decreased fractional shortening and the ejection fraction. Insulin-stimulated glucose uptake and proline-rich Akt substrate 40 phosphorylation were 41% (p < 0.001) and 45% (p < 0.05) lower, respectively, in cardiomyocytes from rats on the HFD. However, long-chain fatty acid (LCFA) uptake was 1.4-fold increased (p < 0.001) and LCFA esterification into triacylglycerols and phospholipids was increased 1.4- and 1.5-fold, respectively (both p < 0.05), in cardiomyocytes from HFD compared with LFD hearts. In the presence of the CD36 inhibitor sulfo-N-succinimidyloleate, LCFA uptake and esterification were similar in LFD and HFD cardiomyocytes. In HFD hearts CD36 was relocated to the sarcolemma, and basal phosphorylation of a mediator of CD36-trafficking, i.e. protein kinase B (PKB/Akt), was increased.Conclusions/interpretationFeeding rats an HFD induced cardiac contractile dysfunction, which was accompanied by the relocation of CD36 to the sarcolemma, and elevated basal levels of phosphorylated PKB/Akt. The permanent presence of CD36 at the sarcolemma resulted in enhanced rates of LCFA uptake and myocardial triacylglycerol accumulation, and may contribute to the development of insulin resistance and diabetic cardiomyopathy.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-007-0735-8) contains supplementary material, which is available to authorised users.

A cold-adapted esterase from psychrotrophic Pseudoalteromas sp. strain 643A

A psychrotrophic bacterium producing a cold-adapted esterase upon growth at low temperatures was isolated from the alimentary tract of Antarctic krill Euphasia superba Dana, and classified as Pseudoalteromonas sp. strain 643A. A genomic DNA library of strain 643A was introduced into Escherichia coli TOP10F', and screening on tributyrin-containing agar plates led to the isolation of esterase gene. The esterase gene (estA, 621 bp) encoded a protein (EstA) of 207 amino acid residues with molecular mass of 23,036 Da. Analysis of the amino acid sequence of EstA suggests that it is a member of the GDSL-lipolytic enzymes family. The purification and characterization of native EstA esterase were performed. The enzyme displayed 20-50% of maximum activity at 0-20 degrees C. The optimal temperature for EstA was 35 degrees C. EstA was stable between pH 9 and 11.5. The enzyme showed activity for esters of short- to medium-chain (C(4) and C(10)) fatty acids, and exhibited no activity for long-chain fatty acid esters like that of palmitate and stearate. EstA was strongly inhibited by phenylmethylsulfonyl fluoride, 2-mercaptoethanol, dithiothreitol and glutathione. Addition of selected divalent ions e.g. Mg(2+), Co(2+) and Cu(2+) led to the reduction of enzymatic activity and the enzyme was slightly activated ( approximately 30%) by Ca(2+) ions.

Purification of structured lipids using SCCO 2 and membrane process

The aim of this study was to evaluate the combination of supercritical carbon dioxide (SCCO 2) and membrane separation technologies in the purification of structured lipids (SLs) previously obtained. The SLs (modified triacylglycerols) were obtained from enzymatic interesterification between medium-chain triacylglycerols (MCT) and ethyl esters of long-chain fatty acids (EtELCFA). This process generates by-products that must be removed from the reaction medium to obtain pure SLs. The purification process was carried out by extraction of the by-products from the reaction medium with supercritical CO 2 and further selective retention of SLs using membranes integrated within the extractor. Two nanofiltration membranes (Osmonics DL4040-C and HL4040-F) and one reverse osmosis membrane (DOW Chemical BW30-4040) were evaluated. Pressures of 9, 11 and 13 MPa were used in the retentate side, and transmembrane pressures (TMP) in the range 0.7–4 MPa were applied. All experiments were conducted at 40 °C. The effect of these pressures on selectivity during the reaction's by-product extraction and retention of SLs by the membrane were analyzed. Results showed that pressures on the retentate side and the TMP are very important parameters in the solubilization and permeation of triacylglycerols, fatty acids and ethyl esters of fatty acids. Retention of 100% of SLs and maximum permeation of reaction by-products were reached at pressure of 9 MPa and TMP of 0.7 MPa, using the BW30-4040 reverse osmosis membrane.

Structural characterization of natural rubber based on recent evidence from selective enzymatic treatments

A structural characterization of natural rubber (NR) was carried out by a combination of selective enzymatic treatment and high-resolution characterization techniques. The nitrogenous groups in NR from Hevea brasiliensis have been regarded as an important factor governing cured rubber properties, although there is no structural evidence to prove that relationship. The nitrogenous compounds in highly purified NR were characterized to determine the origin of the nitrogenous groups in NR. The rubber particles of fresh latex were purified by washing, i.e., a successive dilution of the cream fraction and concentration by centrifugation in the presence of a surfactant. The nitrogen content of the NR formed from the washed rubber particles decreased from 0.281% to 0.015% after washing 3-5 times; this content was similar to that of NR deproteinized by a proteolytic enzyme. The presence of 1-2 nitrogen atoms per rubber chain was estimated on the basis of nitrogen content and number-average molecular weight (Mn). The nitrogen content of fractionated rubber fractions from rubber particles washed for five times increased with increasing Mn. The nitrogenous groups in rubber chains are postulated to mostly originate from phospholipids associating with branch points and functional groups formed by oxidation and successive reactions in NR latex. An analysis of the structure of the chain end group (alpha-terminal) was carried out by treating the deproteinized NR (DPNR) latex with lipase, phosphatase, and phospholipases A(2), B, C and D. The enzymatic treatment of DPNR latex significantly decreased the long-chain fatty acid ester content in DPNR, and also the Mn and Higgins'k' constant, except for phospholipase D treatment. This indicates the presence of phospholipid molecules in NR, which connect rubber molecules together. (1)H-NMR results of rubber obtained from DPNR latex showed weak signals due to monophosphate, diphosphate and phospholipids at the alpha-terminal. Treating DPNR latex with lipase and phosphatase decreased the relative intensity of the (1)H-NMR signals corresponding to phospholipids; however, with the same treatment, no change in the signals due to mono- and diphosphates was observed. The presence of mono- and diphosphates as well as some phospholipid signals after lipase and phosphatase treatment indicates that mono- and diphosphate groups are directly linked to the modified structure at their alpha-terminals; such connections are considered to be due to the association or linkage of such groups with phospholipid.