Hydrogenation Of Linoleic Acid Research Articles

Functional characterization of a fatty acid double-bond hydratase from Lactobacillus plantarum and its interaction with biosynthetic membranes

Hydrogenation of linoleic acid and other polyunsaturated fatty acids is a detoxification mechanism that is present in the Lactobacillus genus of lactic bacteria. The first stage in this multi-step process is hydration of the substrate with formation of 10-hydroxy-9-cis-octadecenoic acid due to fatty-acid hydratase activity that has been detected only in the membrane-associated cell fraction; however, its interaction with the cell membrane is unknown. To provide information in this respect we characterized the homotrimeric 64.7kDa-native protein from Lactobacillus plantarum; afterwards, it was reconstituted in proteoliposomes and analyzed by confocal fluorescence microscopy. The results showed that hydratase is an extrinsic-membrane protein and hence, the enzymatic reaction occurs at the periphery of the cell. This location may be advantageous in the detoxifying process since the toxic linoleic acid molecule can be bound to hydratase and converted to non-toxic 10-hydroxy-9-cis-octadecenoic acid before it reaches cell membrane. Additionally, we propose that the interaction with membrane periphery occurs through electrostatic contacts. Finally, the structural model of L. plantarum hydratase was constructed based on the amino acid sequence and hence, the putative binding sites with linoleic acid were identified: site 1, located in an external hydrophobic pocket at the C-terminus of the protein and site 2, located at the core and in contact with a FAD molecule. Interestingly, it was found that the linoleic acid molecule arranges around a methionine residue in both sites (Met154 and Met81, respectively) that acts as a rigid pole, thus playing a key role in binding unsaturated fatty acids.

Shape and Transition State Selective Hydrogenations Using Egg-Shell Pt-MIL-101(Cr) Catalyst

The use of the metal organic framework MIL-101(Cr) as support for Pt nanoparticles is evaluated in three selective hydrogenation reactions. Homogenous Pt nanoparticles of ∼4 nm can be formed inside the porosity of MIL-101(Cr) in close contact with the Cr trimers in an egg-shell configuration by a wet impregnation procedure combined with sonication. The catalyst is applied in the selective hydrogenations of olefin mixtures, benzonitrile, and linoleic acid. In the case of an olefin mixture, 1-octene is selectively hydrogenated over 1-hexadecene, attributed to diffusion limitations that favor the hydrogenation of the smaller substrate. In the case of benzonitrile hydrogenation, benzylamine is selectively formed over dibenzylamine attributed to transition state selectivity. In the hydrogenation of linoleic acid, selectivities were similar to that for platinum on alumina.

Characterization of the disappearance and formation of biohydrogenation intermediates during incubations of linoleic acid with rumen fluid in vitro1

Dietary unsaturated fatty acids are extensively hydrogenated in the rumen, resulting in the formation of numerous intermediates that may exert physiological effects and alter the fat composition of ruminant-derived foods. A batch culture method was used to characterize the hydrogenation of linoleic acid (LeA) by strained rumen fluid in vitro. Incubations (n=5) were performed in 100-mL flasks maintained at 39°C containing 400mg of grass hay, 50mL of buffered rumen fluid, and incremental amounts of LeA (0, 1.0, 2.5, 5.0, or 10.0mg) for 0, 1.5, 3.0, 4.5, 6.0, and 9.0h. The fatty acid composition of flask contents was determined using complimentary silver-ion thin-layer chromatography, gas chromatography mass-spectrometry, and silver-ion high-performance liquid chromatography. Linoleic acid was extensively (98.1, 97.6, 98.0, and 89.8% for additions of 1.0, 2.5, 5.0, and 10.0mg of LeA, respectively) hydrogenated over time. Complete reduction of LeA to 18:0 was inhibited in direct relation to the amount of added substrate, the extent of which was greatest for the highest amount of LeA addition. Recoveries of 1.0, 2.5, 5.0, and 10.0mg of added LeA as 18:0 averaged 73.6, 65.0, 57.3, and 10.7%, respectively. Incubation of incremental amounts of LeA resulted in a time-dependent accumulation of geometric isomers of 9,11 and 10,12 conjugated linoleic acid, several nonconjugated 18:2 isomers, and a wide range of cis 18:1 and trans 18:1 intermediates. Several unusual intermediates including cis-6,cis-12 18:2; cis-7,cis-12 18:2; and cis-8,cis-12 18:2, were found to accumulate in direct relation to the amount of added LeA, providing the first indications that hydrogenation of LeA by ruminal bacteria may also involve mechanisms other than hydrogen abstraction or isomerization of the cis-12 double bond. Fitting of single-pool, first-order kinetic models to experimental data indicated that the rate of LeA disappearance decreased with increases in substrate availability. Reduction of 18:1 and 18:2 intermediates occurred at much lower rates compared with conjugated linoleic acid and nonconjugated 18:2 isomer formation. In conclusion, the extent of LeA biohydrogenation in vitro was shown to be time- and dose-dependent with evidence that LeA is hydrogenated by ruminal bacteria via several distinct metabolic pathways. The accumulation of several unusual 18:2 isomers indicates that biohydrogenation of LeA also proceeds via mechanisms other than isomerization of the cis-12 double bond.

Comparison of conjugated linoleic acid (CLA) content in milk of ewes and goats with the same dietary regimen

Milk fat is an important source of potential anticarcinogens named conjugated linoleic acid (CLA). The c9, t11-CLA is the major isomer and it is produced by ruminal hydrogenation of linoleic acid that leads first to vaccenic (11t-18:1) and finally to stearic acid (18:0). An alternative CLA pathway is related to the action of the mammary Δ9-desaturase enzyme on 11t-18:1. Diet is considered the main factor that influence the CLA concentration in milk fat...

Continuous mode linoleic acid hydrogenation on Pd/sibunit catalyst

Catalytic hydrogenation of linoleic acid and oleic acid to stearic acid over palladium on mesoporous carbon sibunit (Pd/sibunit) catalyst was studied in a continuous trickle-bed reactor with the weight hourly space velocity 5.4 h−1 at 120°C and 30 bar using tall oil fatty acid (TOFA) as reactor feed. Stearic acid preparation using TOFA as a raw material is of industrial importance. Pd/sibunit catalysts with spherical particle shape of the size 1.62 mm were synthesized with the palladium loadings 0.5, 1, and 2 wt %. The metal dispersion (%), metal particle size (nm), as well as metallic surface area (m2/g metal) of the three synthesized Pd/Sibunit samples were measured by CO chemisorption. The Pd/C catalysts were tested in linoleic acid hydrogenation, showing promising behavior in terms of activity, selectivity and stability to be used in fixed bed applications. The product stream from the fixed bed reactor was saved and analyzed by X-ray fluorescence (XRF) and direct current plasma (DCP) spectroscopy. The catalyst activity increased with the Pd loading. The lowest metal loading of 0.5 wt % gave the least prone to initial deactivation and thus the most stable catalyst. This catalyst can be recommended for farther pilot testing.

Direct Isomerization of Linoleic Acid to Conjugated Linoleic Acids (CLA) using Gold Catalysts

AbstractSupported gold catalysts, e.g., Au on Al2O3, Fe2O3, CeO2, MnO2, TiO2, ZrO2, activated carbon, titanium silicalite TS‐1, were prepared and used for the isomerization of linoleic acid (cis‐9,cis‐12‐octadecadienoic acid) to conjugated linoleic acids (CLA) in the presence of hydrogen at 165 °C in a batch reactor. The best results were obtained using a catalyst with 2 wt % Au on TS‐1, which exhibits a high selectivity (78 %) towards CLA. The two biologically active target CLA isomers, i.e., cis‐9,trans‐11‐CLA and trans‐10,cis‐12‐CLA, were the main products. During the isomerization of linoleic acid to CLA, consecutive reactions also took place. These were the hydrogenation of linoleic acid and CLA to monounsaturated octadecenoic acids and the further hydrogenation of monounsaturated acids to stearic acid. Thus, gold catalysts are capable of isomerizing linoleic acid to CLA and hydrogenating their double bonds to an extent that depends on the Au catalyst used.

Kinetics of linoleic acid hydrogenation on Pd/C catalyst

The hydrogenation of linoleic acid was investigated in semi-batch slurry reactors over 5 wt% palladium on carbon (Pd/C) catalyst in temperature and H 2 pressure ranges of 40–100 °C and 0.5–20 bar using n -decane as a solvent. A reaction network and mechanisms were proposed and corresponding kinetic equations were derived. The parameters of the mechanistic kinetic models were determined by using non-linear regression analysis. The hydrogenation of linoleic acid was investigated in semi-batch slurry reactors over 5 wt% palladium on carbon (Pd/C) catalyst in temperature and H 2 pressure ranges of 40–100 °C and 0.5–20 bar using n -decane as a solvent. The reaction network involves hydrogenation of linoleic acid to monoenoic acid isomers, predominantly oleic acid, and further hydrogenation of monoenoic acids to stearic acid. The reaction kinetics was established in conditions free from diffusional limitations. The rate was temperature and pressure dependent. A reaction network and mechanisms were proposed and corresponding kinetic equations were derived. The parameters of the mechanistic kinetic models were determined by using non-linear regression analysis. The concentrations of linoleic acid, monoenoic acids, and stearic acid were used in parameter estimation. Data fitting allowed discrimination between rival mechanistic models, more specifically the influence of the hydrogen addition. The kinetic models described the formation of the products with satisfying accuracy.

Adipocere formation via hydrogenation of linoleic acid in a victim kept under dry concealment

Adipocere formation is well known as a later post-mortem change. We experienced a female victim who had been sealed up in a clothes box for approximately 4 years. We collected several subcutaneous fats as well as visceral fats from the victim to investigate adipocere formation. Fresh subcutaneous fats of one female and five male victims who suddenly died were used as the control. These samples were homogenized and the lipids were extracted with chloroform and methanol followed by injection into gas chromatography–mass spectrometry and gas chromatography. We detected a hydroxy fatty acid in the fat of the case, but not in the controls. Using standard synthetic hydroxy fatty acid, the lipid extract component was identified as 10-hydroxyoctadecanoic acid (10-OH 18:0) and this concentration was quantified. Consequently we confirmed that adipocere was formed much slowly in dry concealment. In addition, the fatty acid composition was compared with the control. Most of the linoleic acid (18:2) disappeared and a peak developed instead. Using standard synthetic fatty acid, this peak was identified as cis-12-octadecenoic acid ( cis-12-18:1). This suggests that linoleic acid is hydrogenated to cis-12-octadecenoic acid in the process of adipocere formation.

Isomerization of linoleic acid over supported metal catalysts

Heterogeneous supported metal catalysts were applied for the isomerization reaction of linoleic acid ( cis-9, cis-12-octadecadienoic acid) to conjugated linoleic acid (CLA) between 80 and 120 °C in a diluted system. Ru, Ni, Pd, Pt, Rh, Ir, Os, and bimetallic Pt-Rh supported by activated carbon, Al 2O 3, SiO 2Al 2O 3, MCM-22, H-MCM-41, H-Y, and H-β were screened. Catalyst characterization was done by XRD, X-ray fluorescence, XPS, H 2-TPD, DCP-AES, and nitrogen adsorption techniques. The isomerization reaction was conducted batchwise in both 1-octanol and n-decane as solvents. Reactions taking place were the isomerization of linoleic acid to CLA, hydrogenation of linoleic acid and CLA to monounsaturated octadecenoic acids (oleic acid, elaidic acid, cis-vaccenic acid, and trans-vaccenic acid), as well as the further hydrogenation of monounsaturated acids to stearic acid ( n-octadecanoic acid) with isomerization and hydrogenation being two competing parallel reactions. The isomerization reaction was enhanced by catalyst preactivation under hydrogen. The presence of chemisorbed hydrogen increased the conversion but reduced the isomerization selectivity. Ru and Ni showed the best isomerization properties whereas Pd favored the double bond hydrogenation reaction.

Heterogeneously Catalytic Isomerization of Linoleic Acid over Supported Ruthenium Catalysts for Production of Anticarcinogenic Food Constituents

Although research interest on anticarcinogenic and other physiological effects of the cis-9,trans-11 and trans-10,cis-12 positional and geometric conjugated dienoic isomers of linoleic acid (cis-9,cis-12-octadecadienoic acid) on animals and humans has been growing explosively for the past decade, no strikingly efficient process for conjugated linoleic acid (CLA) synthesis has been reported. After development of a new heterogeneously catalytic pathway for isomerization of linoleic acid, several supported metal catalysts have been screened, and in present paper the conjugation reaction of linoleic acid to cis-9,trans-11- and trans-10,cis-12-CLA over 5 wt% Ru/C and 5 wt% Ru/Al 2 O 3 catalysts in a diluted system was studied in the temperature range 76-165°C. Catalyst characterization was done by X-ray powder diffraction, hydrogen temperature-programmed desorption (H 2 -TPD), and nitrogen adsorption techniques. Reactions taking place were isomerization of linoleic acid to CLA, hydrogenation of linoleic acid and CLA to monounsaturated octadecenoic acids (oleic acid, elaidic acid, and cis- and trans-vaccenic acid), and further hydrogenation of monounsaturated acids to stearic acid (n-octadecanoic acid), with conjugation and hydrogenation being two competing parallel reactions. Rate enhancement was obtained by applying a technique of catalyst preactivation under hydrogen, but increased coverage of hydrogen on the Ru surface also restrained the isomerization selectivity. At similar conditions, Ru/C showed a higher turnover frequency than Ru/Al 2 O 3 , 0.000327 and 0.000153 s -1 , respectively, and H 2 -TPD measurements indicated that the former had a higher hydrogen storage capacity than the latter. Ru/Al 2 O 3 , on the other hand, exhibited a higher selectivity for the cis-9,trans-11- and trans-10,cis-12-CLA isomers than Ru/C. The selectivities were very sensitive to the reactant to catalyst mass ratio, and experiments over varied particle size ranges indicated that the conjugation reactions were close to the intrinsic kinetic regime. Hydrogenation selectivity and competitive adsorption between reactant and solvent were minimized by the use of nonpolar solvents such as n-nonane and n-decane, whereas protic solvents such as 1-propanol and 1-octanol exhibited lowered selectivity toward CLA. The CLA isomer composition was studied for the use of pure linoleic acid and cis-9,trans-11-, trans-10,cis-12-, and trans-9,trans-11-CLA isomers as reactants. The surface area of Ru/C decreased slightly from 841 to 749 m 2 /g while repeating the isomerization reaction over the same catalyst sample five times, and the catalytic performance did not indicate any deactivation.

Effect of Sources and Levels of Carbohydrates on Fermentation Characteristics and Hydrogenation of Linoleic Acid by Rumen Bacteria In Vitro

Effect of Sources and Levels of Carbohydrates on Fermentation Characteristics and Hydrogenation of Linoleic Acid by Rumen Bacteria In Vitro

Conjugated linoleic acid in cows milk: independent effects of dietary linoleic and linolenic fatty acids

It is desirable to increase the level of conjugated linoleic acid (CLA) in milk as a health benefit in human nutrition. CLA has been shown to affect carcinogenesis, atherosclerosis, diabetes, the immune system, bone mineralization, body fat accretion and nutrient partitioning. The predominant CLA isomer present in foods from ruminants is cis-9, trans-11 CLA. It is formed in the rumen by anaerobic bacteria as an intermediate in the hydrogenation of linoleic acid. Recent evidence has shown that CLA can also be produced in the mammary gland by desaturation of trans-11 C18:1. Previous researchers have used various oils or oil seeds to try and elevate CLA levels in milk. A problem with this approach is that most oils contain mixtures of fatty acids so responses cannot be attributed to individual acids. Up to now there has been no report looking at how individual fatty acids affect CLA production. The objective of this work was to separate the effects of linoleic and linolenic acids on CLA production in dairy cows.

ルーメン微生物によるトリグリセリドの加水分解とリノール酸の水素添加に及ぼすエタノールの影響

ルーメン微生物によるトリグリセリドの加水分解とリノール酸の水素添加に及ぼすエタノールの影響

Influence of particle size and surface area onin vitrorates of gas production, lipolysis of triacylglycerol and hydrogenation of linoleic acid by sheep rumen digesta orRuminococcus flavefaciens

SummaryParticulate fractions prepared from meadow hay, ranging in size from 0·1 to 2 mm, were incubated with rumen digesta from four cannulated Romney sheep fed the same hay. The rates of gas production, lipolysis of corn oil and hydrogenation of linoleic acid were measured.The rate of gas production per g fermentable particles (FP) was approximately 30% lower with 1–2 mm than with the 0·1–0·4 mm particles. However, per m2surface area the rate for the larger particles was found to be approximately 600% greater.The rates of lipolysis of triacylglycerols and hydrogenation of linoleic acid were respectively 25 and 60% higher per g FP and 1100 and 1200% higher per m2FP surface area with the 1–2 mm particulate fraction.The same hay particulate fractions were incubated with pure cultures ofRuminococcus flavefaciens, since this organism is active in both lipid metabolism and cellulose fermentation. The rate of gas production and the number of organisms adhering to the particles were determined.The effects of particle size on gas production were similar to those found when incubations were carried out with rumen digesta. Per g FP the rate was 40% lower with 1–2 mm than with 0·1–0·4 mm particles. However, per m2surface area the rate was found to be approximately 450% greater with the former.It was further found that although the density of the bacterial population on 1–2 mm particles was 600% higher than on the 0·1–0·4 mm particles, the rate of gas production per 109bacteria remained unchanged.We conclude that per m2surface area fermentation, lipolysis and hydrogenation were more rapid with particles ranging from 1 to 2 than from 0·1 to 0·4 mm in size. This was due, at least in part, to microbial population density.

Hydrogenation of linoleic acid by a rumen spirochete.

Borrelia sp. B(2)5, when grown in a medium containing [1-(14)C] linoleic acid in an atmosphere of CO(2), was found to hydrogenate linoleic acid to trans-11-octadecenoic acid.

Use of hydrazine as a reducing agent for unsaturated compounds. III. hydrogenation of linoleic acid

AbstractLinoleic acid can be hydrogenated by hydrazine and, under suitable experimental conditions, the reaction, as measured by the decrease in iodine value, is 90% complete in 8 hours. The reaction in its initial stages proceeds more rapidly with linoleic acid than with oleic and other mono‐ethenoid acids indicating that the rate of hydrogenation varies with the degree of unsaturation and the concentration of unsaturated acids.

(303)リノール酸の水素添加(第1報)共軛リノール酸石鹸の水素添加

(303)リノール酸の水素添加(第1報)共軛リノール酸石鹸の水素添加

(352)リノール酸の水素添加について(第2報)リノール酸メチルの水素添加

(352)リノール酸の水素添加について(第2報)リノール酸メチルの水素添加