Unsaturated Products Research Articles

Development of unsaturated fatty acid production from transgenic microalgae

Development of unsaturated fatty acid production from transgenic microalgae

Effect of silylated triarylphosphine ligands on rhodium‐catalyzed hydrosilylation

A series of silylated triarylphosphines was synthesized. Hydrosilylation reactions of styrene with triethoxysilane catalyzed by RhCl3/silylated triarylphosphine complexes were investigated. The complexes RhCl3/phenylbis(4‐trimethylsilylphenyl)phosphine and RhCl3/tris(4‐trimethylsilylphenyl)phosphine exhibited higher activity as well as greater β‐adduct selectivity, and no unsaturated product was obtained. The results suggest that the silyl moieties have a significant impact on the catalytic process. Copyright © 2016 John Wiley & Sons, Ltd.

ChemInform Abstract: Highly Convergent Synthesis of Intensively Blue Emissive Furo[2,3‐c]isoquinolines by a Palladium‐Catalyzed Cyclization Cascade of Unsaturated Ugi Products.

AbstractAn approach to the unusual furo[2,3‐c]isoquinoline scaffold is presented.

Product distribution change in the early stages of carbon monoxide hydrogenation over cobalt magnesium Fischer-Tropsch catalyst

The catalytic hydrogenation of carbon monoxide, known as the Fischer-Tropsch process, is a technologically important, complex multipath reaction which produces long chain hydrocarbons. In order to access the initial kinetics and the mechanism, we developed a reactor that provides information under non-steady state conditions. We tested a CoMgO catalyst and monitored the initial product formation within 2s of exposure to CO as well as the time dependence of high molecular weight products (in a 60s window) and found drastic changes in the product selectivity. The probability for forming branched isomers (C4 and C5) peaks in the first 25s, and within that time frame no unsaturated products were detected. The subsequent decline (at ∼35 to 40s) of branched isomers coincides with the detection of olefins (fromC2 to C5) and the change in carbon coverage at the surface of the catalyst. This indicates a change in the reaction pathway.

Membrane engineering via trans unsaturated fatty acids production improves Escherichia coli robustness and production of biorenewables

Constructing microbial biocatalysts that produce biorenewables at economically viable yields and titers is often hampered by product toxicity. For production of short chain fatty acids, membrane damage is considered the primary mechanism of toxicity, particularly in regards to membrane integrity. Previous engineering efforts in Escherichia coli to increase membrane integrity, with the goal of increasing fatty acid tolerance and production, have had mixed results. Herein, a novel approach was used to reconstruct the E. coli membrane by enabling production of a novel membrane component. Specifically, trans unsaturated fatty acids (TUFA) were produced and incorporated into the membrane of E. coli MG1655 by expression of cis-trans isomerase (Cti) from Pseudomonas aeruginosa. While the engineered strain was found to have no increase in membrane integrity, a significant decrease in membrane fluidity was observed, meaning that membrane polarization and rigidity were increased by TUFA incorporation. As a result, tolerance to exogenously added octanoic acid and production of octanoic acid were both increased relative to the wild-type strain. This membrane engineering strategy to improve octanoic acid tolerance was found to require fine-tuning of TUFA abundance. Besides improving tolerance and production of carboxylic acids, TUFA production also enabled increased tolerance in E. coli to other bio-products, e.g. alcohols, organic acids, aromatic compounds, a variety of adverse industrial conditions, e.g. low pH, high temperature, and also elevated styrene production, another versatile bio-chemical product. TUFA permitted enhanced growth due to alleviation of bio–product toxicity, demonstrating the general effectiveness of this membrane engineering strategy towards improving strain robustness.

Highly Convergent Synthesis of Intensively Blue Emissive Furo[2,3-c]isoquinolines by a Palladium-Catalyzed Cyclization Cascade of Unsaturated Ugi Products.

A convergent and diversity-oriented approach to the unusual furo[2,3-c]isoquinoline scaffold is presented. This serendipity-driven approach is characterized by an Ugi multicomponent reaction, which gives the substrate for a palladium-catalyzed insertion-alkynylation-cycloisomerization cascade to provide the furo[2,3-c]isoquinolines in moderate to high yield. Upon UV excitation, all representatives are intensively blue luminescent, as observed by the naked eye, and quantitative fluorescence spectroscopy reveals a considerable effect of the substitution pattern on the quantum yields. The electronic structure is semiquantitatively rationalized by DFT and time-dependent DFT calculations.

Techno-economic analysis of unsaturated polyester production from waste PET

Techno-economic analysis of unsaturated polyester production from waste PET

Prospects for applications of electron beams in processing of gas and oil hydrocarbons

Waste-free processing of oil and oil gases can be based on electron-beam technologies. Their major advantage is an opportunity of controlled manufacturing of a wide range of products with a higher utility value at moderate temperatures and pressures. The work considers certain key aspects of electron beam technologies applied for the chain cracking of heavy crude oil, for the synthesis of premium gasoline from oil gases, and also for the hydrogenation, alkylation, and isomerization of unsaturated oil products. Electronbeam processing of oil can be embodied via compact mobile modules which are applicable for direct usage at distant oil and gas fields. More cost-effective and reliable electron accelerators should be developed to realize the potential of electron-beam technologies.

Palmitic acid (16:0) competes with omega-6 linoleic and omega-3 ɑ-linolenic acids for FADS2 mediated Δ6-desaturation

Sapienic acid, 16:1n-10 is the most abundant unsaturated fatty acid on human skin where its synthesis is mediated by FADS2 in the sebaceous glands. The FADS2 product introduces a double bond at the Δ6, Δ4 and Δ8 positions by acting on at least ten substrates, including 16:0, 18:2n-6, and 18:3n-3. Our aim was to characterize the competition for accessing FADS2 mediated Δ6 desaturation between 16:0 and the most abundant polyunsaturated fatty acids (PUFA) in the human diet, 18:2n-6 and 18:3n-3, to evaluate whether competition may be relevant in other tissues and thus linked to metabolic abnormalities associated with FADS2 or fatty acid levels. MCF7 cells stably transformed with FADS2 biosynthesize 16:1n-10 from exogenous 16:0 in preference to 16:1n-7, the immediate product of SCD highly expressed in cancer cell lines, and 16:1n-9 via partial β-oxidation of 18:1n-9. Increasing availability of 18:2n-6 or 18:3n-3 resulted in decreased bioconversion of 16:0 to 16:1n-10, simultaneously increasing the levels of highly unsaturated products. FADS2 cells accumulate the desaturation-elongation products 20:3n-6 and 20:4n-3 in preference to the immediate desaturation products 18:3n-6 and 18:4n-3 implying prompt/coupled elongation of the nascent desaturation products. MCF7 cells incorporate newly synthesized 16:1n-10 into phospholipids. These data suggest that excess 16:0 due to, for instance, de novo lipogenesis from high carbohydrate or alcohol consumption, inhibits synthesis of highly unsaturated fatty acids, and may in part explain why supplemental preformed EPA and DHA in some studies improves insulin resistance and other factors related to diabetes and metabolic syndrome aggravated by excess calorie consumption.

High-sensitivity HPGe gamma-spectrometry analysis of radionuclides in Martian meteorites

Analysis of cosmogenic radionuclides in Martian meteorites is a great radioanalytical challenge because of the high scientific value of these meteorites, and necessity to apply non-destructive methods of analysis, e.g., low-level gamma-ray spectrometry. The measured 54Mn, 22Na, and 26Al levels in two fragments of the Tissint meteorite, a recent fall (18 July 2011), were 0.9, 1.1 and 0.6 Bq/kg in average. The high 22Na/26Al activity ratio (1.89 ± 0.05) measured in the larger sample (908.7 g) indicates an unsaturated production of 26Al in the Tissint meteorite.

Optimum conditions determination of methyl methacrylate obtaining over tungsten-containing catalyst

The main common methods of methyl methacrylate producing are acetoncyanohydrin method and oxidation of isobutylene and tert-butanol. Because of the significant drawbacks of these methods, it is important to develop new, alternative ways of methyl methacrylate obtaining, one of which could be aldol condensation of methyl propionate with formaldehyde in the gas phase. The actual task for today is to find out effective catalysts for this process. For this aim, methyl propionate condensation with formaldehyde was studied in the presence of B 2 O 3 -P 2 O 5 -WO 3 /SiO 2 catalyst, which previously has showed high activity in the condensation of propionic acid with formaldehyde to methacrylic acid. The paper also investigates the influence of methanol on the side reaction of methyl propionate hydrolysis; it was found that adding methanol causes a slight increase in MMA selectivity, but the yield of unsaturated products decreases, and therefore adding methanol to the reaction mixture for the MP condensation with FA over B 2 O 3 -P 2 O 5 -WO 3 /SiO 2 catalyst is impractical. The optimum conditions for MP condensation with FA, namely temperature 653 K and contact time 12 s were found. Under these conditions, in the presence of B 2 O 3 -P 2 O 5 -WO 3 /SiO 2 catalyst with an atomic ratio of components B:P:W 3:1:0.6 respectively total yield of MMA and MAA was 31.91% while their total selectivity was 32.3%.

Functional Characterization of a Dehydratase Domain from the Pikromycin Polyketide Synthase.

Metabolic engineering of polyketide synthase (PKS) pathways represents a promising approach to natural products discovery. The dehydratase (DH) domains of PKSs, which generate an α,β-unsaturated bond through a dehydration reaction, have been poorly studied compared with other domains, likely because of the simple nature of the chemical reaction they catalyze and the lack of a convenient assay to measure substrate turnover. Herein we report the first steady-state kinetic analysis of a PKS DH domain employing LC-MS/MS analysis for product quantitation. PikDH2 was selected as a model DH domain. Its substrate specificity and mechanism were interrogated with a systematic series of synthetic triketide substrates containing a nonhydrolyzable thioether linkage as well as by site-directed mutagenesis, evaluation of the pH dependence of the catalytic efficiency (V(max)/K(M)), and kinetic characterization of a mechanism-based inhibitor. These studies revealed that PikDH2 converts d-alcohol substrates to trans-olefin products. The reaction is reversible with equilibrium constants ranging from 1.2 to 2. Moreover, the enzyme activity is robust, and PikDH2 was used on a preparative scale for the chemoenzymatic synthesis of unsaturated triketide products. PikDH2 was shown to possess remarkably strict substrate specificity and is unable to turn over substrates that are epimeric at the β-, γ-, or δ-position. We also demonstrated that PikDH2 has a key ionizable group with a pK(a) of 7.0 and can be irreversibly inactivated through covalent modification by a mechanism-based inhibitor, which provides a foundation for future structural studies to elucidate substrate-protein interactions.

Reactivity Studies on a Binuclear Ruthenium(0) Complex Equipped with a Bridging κ(2)N,Ge-Amidinatogermylene Ligand.

The amidinatogermylene-bridged diruthenium(0) complex [Ru2{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(CO)7] (2; (i)Pr2bzam = N,N'-bis(iso-propyl)benzamidinate; HMDS = N(SiMe3)2) reacted at room temperature with (t)BuNC and PMe3 to give [Ru2{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(L)(CO)6] (L = (t)BuNC, 3; PMe3, 4), which contain the new ligand in an axial position on the Ru atom that is not attached to the amidinato fragment. At 70 °C, 2 reacted with PPh3, PMe3, dppm, and dppe to give the equatorially substituted derivatives [Ru2{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(L)(CO)6] (L = PPh3, 5; PMe3, 6) and [Ru2{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(μ-κ(2)P,P'-L2)(CO)5] (L2 = dppm, 7; dppe, 8). HSiEt3 and HSnPh3 were oxidatively added to complex 2 at 70 °C, leading to the coordinatively unsaturated products [Ru2(ER3)(μ-H){μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(CO)5] (ER3 = SiEt3, 9; SnPh3, 10), which easily reacted with (t)BuNC and CO to give the saturated derivatives [Ru2(ER3)(μ-H){μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}((t)BuNC)(CO)5] (ER3 = SiEt3, 11; SnPh3, 12) and [Ru2(ER3)(μ-H){μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(CO)6] (ER3 = SiEt3, 13; SnPh3, 14), respectively. Compounds 9-14 have their ER3 group on the Ru atom that is not attached to the amidinato fragment. In contrast, the reaction of 2 with H2 at 70 °C led to the unsaturated tetranuclear complex [Ru4(μ-H)2{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}2(CO)10] (15), which also reacted with (t)BuNC and CO to give the saturated derivatives [Ru4(μ-H)2{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}2(L)2(CO)10] (L = (t)BuNC, 16; CO, 17). All tetraruthenium complexes contain an unbridged metal-metal connecting two germylene-bridged diruthenium units. Under CO atmosphere, complex 17 reverted to compound 2. All of the coordinatively unsaturated products (9, 10, and 15) have their unsaturation(s) located on the Ru atom(s) that is(are) attached to the amidinato fragment(s). In the absence of added reagents, the thermolysis of 2 in refluxing toluene led to [Ru4{μ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}{μ3-κGe-Ge(HMDS)}(μ-κ(3)N,C,N'-(i)Pr2bzam)(μ-CO)(CO)8] (18), which contains two new ligands, a triply bridging germylidyne and a bridging benzamidinate, and that results from the condensation of two molecules of 2 and the activation of the Ge-N bond of the benzamidinatogermylene ligand of 2.

Examining Reaction Specificity in PvcB, a Source of Diversity in Isonitrile-Containing Natural Products

Many bacteria produce isonitrile-containing natural products that are derived from aromatic amino acids. The synthetic clusters that control biosynthesis most commonly encode two enzymes, designated PvcA and PvcB, as well as additional enzymes that direct synthesis of the natural product. The PvcA enzyme installs the isonitrile moiety at the amino group of either tyrosine or tryptophan, as dictated by the particular pathway. The common pathway intermediate produced by PvcA is directed toward different ultimate products by PvcB, a member of the family of Fe(2+), α-ketoglutarate-dependent oxygenases. To continue our investigation of the structural and functional properties of the isonitrile biosynthetic pathways, we present here a study of the PvcB homologues from three organisms. Two pathways, derived from Pseudomonas aeruginosa and Xenorhabdus nematophila, produce known products. A third PvcB homologue from Erwinia amylovora is part of an uncharacterized pathway. Our results demonstrate the diversity of reactions catalyzed. Although all PvcB enzymes catalyze the hydroxylation of the tyrosine isonitrile substrate, the elimination of the hydroxyl in Pseudomonas and Erwinia is driven by deprotonation at Cα, resulting in the initial production of an unsaturated tyrosine isonitrile product that then cyclizes to a coumarin derivative. PvcB from Xenorhabdus, in contrast, catalyzes the same oxygenation, but loss of the hydroxyl group is accompanied by decarboxylation of the intermediate. Steady-state kinetic analysis of the three reactions and a docking model for the binding of the tyrosine isonitrile substrate in the PvcB active site highlight subtle differences between the PvcB homologues.

Stereoselective synthesis of (all-Z)-hentriaconta-3,6,9,12,15,19,22,25,28-nonaene.

Several microorganisms produce small quantities of polyunsaturated hydrocarbons and such natural products are of interest. Starting from the ethyl ester of eicosapentaenoic acid, the total synthesis of the natural product (all-Z)-hentriaconta-3,6,9,12,15,19,22,25,28-nonaene has been achieved in eight steps and 15% overall yield. The synthesis is based on a stereoselective Wittig reaction and confirms the all-Z-configuration of the nine double bonds in this highly unsaturated natural product.

Efficient base-catalyzed decomposition and in situ hydrogenolysis process for lignin depolymerization and char elimination

Serious char formation caused by the repolymerization of unsaturated decomposition products is a considerable challenge for current lignin utilization. Here, a novel and efficient base-catalyzed depolymerization and in situ hydrogenolysis process for lignin decomposition and char elimination was proposed using the synergic catalyst of NaOH coordinated with Ru/C. In which, lignin was first depolymerized to phenolic monomer and its oligomer, and then the oligomer was further converted to more stable aliphatic alcohols simultaneously. The results showed that more than 92.5% of lignin was converted, giving 12.69% phenolic monomer, 6.12% aliphatic alcohol and less than 14.03% residual solid. This residual solid selectivity was far lower than it from the single catalyst condition. Furthermore, the products were analyzed using GC–MS, GPC, HPLC–MS and 1H NMR. The synergistic effect between depolymerization and hydrogenolysis was also investigated through comparative analysis of the feedstock, products, and the recovered lignin.

Human blood glycosaminoglycans: isolation and analysis.

Glycosaminoglycans (GAGs) are linear polysaccharides having disaccharide building blocks consisting of an amino sugar (N-acetylglucosamine, or N-acetylgalactosamine) and a uronic acid (glucuronic acid or iduronic acid) or galactose. Glycosaminoglycans have sulfated residues at various positions except for hyaluronan, and those sulfated residues regulate the biological functions of a wide variety of proteins, primarily through high-affinity interactions mediated by specific patterns/densities of sulfation and sugar sequences. Alteration of GAG structure is associated with a number of disease conditions and therefore the analyses of GAG structures and their sulfation patterns are important for the development of disease biomarkers and for treatment options. Extensive structural and quantitative analyses of GAGs from human blood are largely unexplored which may be due to the exhaustive isolation process because of the presence of too much interfering proteins and lipids such as serum albumin. Therefore we established a new GAG isolation method using the least amount (~200 μl) of human blood, consisting of a combination of proteolytic digestion and selective ethanol precipitation of GAGs, digestion of GAGs recovered on the filter cup by direct addition of GAG lyase reaction solution, and subsequent high-pressure liquid chromatography of unsaturated disaccharide products that enable to analyze GAG structures and contents. This isolation method offers an 80 % recovery of GAGs and can be applied to analyze a minute GAG content (≥1 nmol) from the least amount of biological fluids. Hence the method could be useful for the development of disease biomarkers.

Effect of feeding rice bran lyso-phospholipids and rumen protected fat on feed intake, nutrient utilization and milk yield in crossbred cows

In vivo studies were conducted to observe the effect of feeding rice bran lyso-phospholipids (RBLP) and rumen protected fat (RPF) in 18 crossbred lactating Karan Fries (Holstein Friesian × Sahiwal) cows. They were randomly allocated to 3 treatment groups having 6 animals in each group. Group 1 was supplemented with 2.5% mustard oil, group 2 with 6% RBLP and group 3 with 3% RPF in the concentrate mixture. All the 3 diets were isocaloric and isonitrogenous. All the cows were given roughage: concentrate mixture (60: 40) ration and roughage comprised of berseem fodder (30%) and wheat straw (30%) as per requirements. Lactating Karan Fries cows averaging 12±2.5 kg of milk, 100±9 days in milk and 400±15 kg live weight, were stratified for milk yield, days in milk, age, stage of lactation and body weight. The dry matter intake (DMI) averaged 12.14, 11.77 and 11.88 kg/d in groups 1–3, respectively. The intake and digestibility of nutrients were not affected by different treatments, whereas the digestibility of EE increased by the supplementation of RBLP in the diet of cows. Milk yield remained unaltered, while 4% fat corrected milk (FCM) yield increased as a result of adding RBLP and RPF due to significant increase in fat per cent in the milk of groups 2 and 3 cows. The protein, lactose, total solids, and solids-not-fat were not affected by dietary treatments. The proportion of milk total unsaturated fatty acids production was increased in groups 2 and 3. The cost of feeding lactating cows in terms of `/kg milk and 4% FCM was 10.24, 8.83, 9.67 and 9.40, 7.88, 8.72 in groups 1, 2 and 3, respectively. Cows fed RBLP were more economical by 15.97 and 9.51% to produce whole milk and 19.30 and 10.70% to produce FCM in comparison to groups 1 and 3 cows, respectively. It was inferred that RBLP can be used @ 6% in the ration of dairy cows without any adverse effect on digestibility of nutrients and milk production and it can also replace the costlier sources of energy i.e. mustard oil and RPF in the diet of lactating animals.

Evidence of Highly Active Cobalt Oxide Catalyst for the Fischer–Tropsch Synthesis and CO2 Hydrogenation

Hydrogenations of CO or CO2 are important catalytic reactions as they are interesting alternatives to produce fine chemical feedstock hence avoiding the use of fossil sources. Using monodisperse nanoparticle (NP) catalysts, we have studied the CO/H2 (i.e., Fischer-Tropsch synthesis) and CO2/H2 reactions. Exploiting synchrotron based in situ characterization techniques such as XANES and XPS, we were able to demonstrate that 10 nm Co NPs cannot be reduced at 250 °C while supported on TiO2 or SiO2 and that the complete reduction of cobalt can only be achieved at 450 °C. Interestingly, cobalt oxide performs better than fully reduced cobalt when supported on TiO2. In fact, the catalytic results indicate an enhancement of 10-fold for the CO2/H2 reaction rate and 2-fold for the CO/H2 reaction rate for the Co/TiO2 treated at 250 °C in H2 versus Co/TiO2 treated at 450 °C. Inversely, the activity of cobalt supported on SiO2 has a higher turnover frequency when cobalt is metallic. The product distributions could be tuned depending on the support and the oxidation state of cobalt. For oxidized cobalt on TiO2, we observed an increase of methane production for the CO2/H2 reaction whereas it is more selective to unsaturated products for the CO/H2 reaction. In situ investigation of the catalysts indicated wetting of the TiO2 support by CoO(x) and partial encapsulation of metallic Co by TiO(2-x).

Unexpected Pyrolytic Behaviour of Substituted Benzo[c]thiopyran and Thieno[2,3-c]thiopyran S,S-dioxides

Flash vacuum pyrolysis (FVP) of benzo[c]thiopyran S,S-dioxide (1) results in formation of indene and 2-vinylbenzaldehyde as previously described. A range of eight analogues with various substitution patterns are found to behave differently. In general, there is no extrusion of SO2 to give products analogous to indene, but unsaturated carbonyl products analogous to 2-vinylbenzaldehyde are formed in most cases by way of ring expansion to a 7-membered ring sultine, extrusion of SO, and intramolecular hydrogen atom transfer. Other processes observed include formation of anthracene via an isomeric 7-membered sultine with loss of SO, CO and methane or butane, and formation of 4-ethylidene-4,5-dihydrocyclobuta[b]thiophenes by way of SO loss, a radical rearrangement, and extrusion of acetone. The analogues with a halogen substituent at position 8 on the benzene ring require a higher temperature to react and give naphthalene resulting from net elimination of HX and SO2. The X-ray crystal structure of 1 is also reported.