Decarboxylation Of Fatty Acids Research Articles

Biochemical characterization of three new \u03b1-olefin-producing P450 fatty acid decarboxylases with a halophilic property

BackgroundThe CYP152 family member OleTJE from Jeotgalicoccus sp. ATCC 8456 has been well-known to catalyze the unusual one-step decarboxylation of free fatty acids towards the formation of terminal alkenes. Efforts to tune up its decarboxylation activity for better production of biological alkenes have been extensively explored via approaches such as site-directed mutagenesis and electron source engineering, but with limited success. To gain more insights into the decarboxylation mechanism and reaction bifurcation (decarboxylation versus hydroxylation), we turned to an alternative approach to explore the natural CYP152 resources for a better variety of enzyme candidates.ResultsWe biochemically characterized three new P450 fatty acid decarboxylases including OleTJH, OleTSQ and OleTSA, with respect to their substrate specificity, steady-state kinetics, and salt effects. These enzymes all act as an OleTJE-like fatty acid decarboxylase being able to decarboxylate a range of straight-chain saturated fatty acids (C8–C20) to various degrees. Site-directed mutagenesis analysis to the lower activity P450 enzyme OleTSA revealed a number of key amino acid residues within the substrate-binding pocket (T47F, I177L, V319A and L405I) that are important for delicate substrate positioning of different chain-length fatty acids and thus the decarboxylation versus hydroxylation chemoselectivity, in particular for the mid-chain fatty acids (C8–C12). In addition, the three new decarboxylases exhibited optimal catalytic activity and stability at a salt concentration of 0.5 M, and were thus classified as moderate halophilic enzymes.ConclusionThe P450 fatty acid decarboxylases OleTJE, OleTJH, OleTSQ and OleTSA belong to a novel group of moderate halophilic P450 enzymes. OleTJH from Jeotgalicoccus halophilus shows the decarboxylation activity, kinetic parameters, as well as salt tolerance and stability that are comparable to OleTJE. Site-directed mutagenesis of several key amino acid residues near substrate-binding pocket provides important guidance for further engineering of these P450 fatty acid decarboxylases that hold promising application potential for production of α-olefin biohydrocarbons.

Renewable diesel production by hydrothermal decarboxylation of fatty acids over platinum on carbon catalyst

For over a decade researchers have been investigating the potential to produce renewable diesel from fatty acid, possibly because it possesses good qualities such as very high cetane number, oxidative stability, and renewability, and can be produced and transported using existing refinery process facilities, making it a potential substitute for petroleum diesel. Most of these investigations required the use of organic solvents and hydrogen which might increase the cost of production. To avoid this, the current work was conducted in an aqueous medium without the addition of hydrogen, using hydrothermal decarboxylation of palmitic and oleic acids in the presence of 5% platinum on carbon catalyst. The performance of the primary products pentadecane and heptadecane obtained was optimized by determining the optimum operating conditions of temperature and residence time. The results showed that the highest molar yield of pentadecane from palmitic acid was 55.3% at the optimum conditions of 290 °C and 1.5 h, and that of heptadecane from oleic acid was 16.4% at 290 °C and 4 h. With these results the cost of production might be reduced and using a benign, environmentally friendly medium would help to reduce the risk associated with the use of organic solvents.

Mechanism of fatty acid decarboxylation catalyzed by a non-heme iron oxidase (UndA): a QM/MM study.

UndA is a non-heme iron enzyme that was recognized to catalyze the decarboxylation of medium chain (C10-C14) fatty acids to produce trace amounts of 1-alkenes. Owing to the electron imbalance during the oxidative decarboxylation of the substrate and the reduction of O2, only single turnover reactions were obtained in UndA in vitro assays. Unlike the general non-heme iron enzymes, the catalytic efficiency of UndA is quite low. According to the previous proposal, both FeIII-OO˙- and FeIV[double bond, length as m-dash]O complexes may abstract the β-H of fatty acids to trigger the oxidative decarboxylation reaction. Herein, on the basis of the crystal structures of UndA in complex with the substrate analogues, we constructed a series of computational models and performed quantum mechanics/molecular mechanics (QM/MM) calculations to explore the UndA-catalyzed decarboxylation using lauric acid as the substrate. Our calculation results reveal that only the FeIII-OO˙- complex can initiate the decarboxylation, and the substrate (lauric acid) should monodentately coordinate to the Fe center to facilitate the β-H abstraction. In addition, the monodentate coordination corresponds to higher relative energy than the bidentate mode, which may explain the low efficiency of UndA. It is also revealed that as long as the β-H is extracted by the FeIII-OO˙-, the decarboxylation of the substrate radical is quite easy, and an electron transfer from the substrate to the iron center is the prerequisite. For the FeIV[double bond, length as m-dash]O complex, since the β-H is far from the OFe atom and the angle of ∠Fe-O-H is 53.1°, the H-abstraction is calculated to be difficult.

Light-Driven Enzymatic Decarboxylation of Fatty Acids.

The photoenzymatic decarboxylation of fatty acids to alkanes is proposed as an alternative approach for the synthesis of biodiesel. By using a recently discovered photodecarboxylase from Chlorella variabilis NC64A (CvFAP) we demonstrate the irreversible preparation of alkanes from fatty acids and triglycerides. Several fatty acids and their triglycerides are converted by CvFAP in near‐quantitative yield and exclusive selectivity upon illumination with blue light. Very promising turnover numbers of up to 8000 were achieved in this proof‐of‐concept study.

Catalytic decarboxylation of fatty acids to hydrocarbons over non‐noble metal catalysts: the state of the art

AbstractThe catalytic decarboxylation of fatty acids to yield hydrocarbons, for use as biofuel as a main target, is a topical reaction in which the main challenge is actually to control the selectivity while using the smallest amount of hydrogen possible (or even better, not using hydrogen at all) in order to optimize cost‐efficiency of the process. Herein, the focus is on the non‐noble mono‐, bi‐ and tri‐metallic catalysts used to carry out this reaction. Historically, several non‐noble monometallic catalysts based on Cu, Co, Ni supported on different types of supports were first studied. Among such materials, the Co‐based catalysts were not selective, while, Cu‐based catalysts were more or less selective to hydrocarbons or to olefins, depending on the support used. Among these three metals, the Ni‐based catalysts are the most widely described ones due to their specific ability to promote deoxygenation reactions. Combining Ni to a second metal yielded a synergistic effect toward better catalytic performances, with increases in both conversion and selectivity and also improvement of the resistance of the catalyst to carbon deposit, especially when adding non‐noble metals. For future prospects, it appears that the main challenge will be to be able to maintain good catalytic performances under inert gas in solvent‐free conditions, in order to yield a fully environmentally friendly and cost‐effective process. © 2018 Society of Chemical Industry

Metabolomics-based profiling of three terminal alkene-producing Jeotgalicoccus spp. during different growth phase

Production of terminal alkenes by microbes has gained importance due to its role as a chemical feedstock in commercial industries. Jeotgalicoccus species has been widely unexplored despite being well-known as a natural producer of terminal alkene, catalyzing the one-step fatty acid decarboxylation reaction by OleTJE cytochrome P450. In this study, widely targeted ion-pair LC-MS/MS was used to monitor central carbon metabolism of Jeotgalicoccus halotolerans JCM 5429, Jeotgalicoccus huakuii JCM 8176, and Jeotgalicoccus psychrophilus JCM 5429at logarithmic and stationary phases. Growth and production profile of terminal alkene, alcohols and organic acids were also measured. Among the three strains used in this study, J. halotolerans and J. psychrophilus showed higher terminal alkene production compared to J. huakuii. All strains achieved maximum terminal alkene production at logarithmic phase and therefore, detailed analysis of the metabolite profiles of the three strains were performed in logarithmic phase. PCA analysis showed that the strains were discriminated based on their ability to produce terminal alkene along PC1 and some of the important metabolites corresponding to this separation is the acetyl-CoA and 2-oxoglutarate. This study is the first report on metabolite profiling of three Jeotgalicoccus spp. in different growth phases. The results from this study can provide a better understanding of the changes that occur in the metabolome level during growth and production of terminal alkene in Jeotgalicoccus species.

Continuous Hydrothermal Decarboxylation of Fatty Acids and Their Derivatives into Liquid Hydrocarbons Using Mo/Al2O3 Catalyst.

In this study, we report a single-step continuous production of straight-chain liquid hydrocarbons from oleic acid and other fatty acid derivatives of interest including castor oil, frying oil, and palm oil using Mo, MgO, and Ni on Al2O3 as catalysts in subcritical water. Straight-chain hydrocarbons were obtained via decarboxylation and hydrogenation reactions with no added hydrogen. Mo/Al2O3 catalyst was found to exhibit a higher degree of decarboxylation (92%) and liquid yield (71%) compared to the other two examined catalysts (MgO/Al2O3, Ni/Al2O3) at the maximized conditions of 375 °C, 4 h of space time, and a volume ratio of 5:1 of water to oleic acid. The obtained liquid product has a similar density (0.85 kg/m3 at 15.6 °C) and high heating value (44.7 MJ/kg) as commercial fuels including kerosene (0.78–0.82 kg/m3 and 46.2 MJ/kg), jet fuel (0.78–0.84 kg/m3 and 43.5 MJ/kg), and diesel fuel (0.80–0.96 kg/m3 and 44.8 MJ/kg). The reaction conditions including temperature, volume ratio of water-to-feed, and space time were maximized for the Mo/Al2O3 catalyst. Characterization of the spent catalysts showed that a significant amount of amorphous carbon deposited on the catalyst could be removed by simple carbon burning in air with the catalyst recycled and reused.

Deactivation and regeneration studies of activated carbon during continuous decarboxylation of oleic acid in subcritical water

Decarboxylation of fatty acids using sub or supercritical water is a renewable pathway for producing fuel range hydrocarbons with high selectivity without an added external source of H2. Activated carbon (AC) has been shown as an effective catalyst for decarboxylation of fatty acids to fuels but it has limited life and an unknown surface chemistry for this catalysis. This study investigates the stability (time on stream) and surface chemistry of AC for the decarboxylation of oleic acid in a bench scale continuous reactor system at 400 °C, 2 h of space time and water to oleic acid ratio of 4:1. AC was found to be effective until 30 h time on stream (out of 45 h), providing 91% degree of decarboxylation constantly. The degree of decarboxylation declined afterwards, dropping from 91 to 50% after 45 h time on stream due to deactivation. The thermal regeneration of deactivated AC was examined using potassium hydroxide (KOH) treatment at 750 °C which helped to regain the physical and catalytic properties of AC. The degree of decarboxylation of oleic acid using fresh and regenerated AC were 91% and 87%, respectively. On the other hand, the selectivity of heptadecane obtained using fresh and regenerated activated carbon was 89.3% and 81.2%, respectively. Decarboxylated liquid products using fresh and regenerated activated carbon gave a similar density and HHV’s as commercial fuels, showing the utility of this approach.

Decarboxylation of Fatty Acids on Anisotropic Au(110) Surfaces

Lowering the oxygen content in biofuels is of vital importance, since high oxygen level content leads to low stability, low heat value, and corruption in engines. Here we report on the thermally activated decarboxylation of fatty acids, raw materials for biofuel production, on an anisotropic Au(110) surface. Due to the one-dimensional (1D) geometrical constraint of the surface reconstruction, linear fatty acid molecules (C30H60O2) are decarboxylated and polymerized at their terminal ends at mild temperatures, resulting in the formation of oxygen-free aliphatic hydrocarbons. Different reaction stages of the decarboxylation were monitored by high-resolution scanning tunneling microscopy and X-ray photoemission spectroscopy. On the basis of density functional theory calculations, a two-step process was proposed for the fatty acid decarboxylation. Our work demonstrates a novel strategy for deoxygenation of fatty acids on a 1D constrained surface as a model catalytic system for producing low oxygen content biofuels.

Structure and function of the cytochrome P450 peroxygenase enzymes

The cytochromes P450 (P450s or CYPs) constitute a large heme enzyme superfamily, members of which catalyze the oxidative transformation of a wide range of organic substrates, and whose functions are crucial to xenobiotic metabolism and steroid transformation in humans and other organisms. The P450 peroxygenases are a subgroup of the P450s that have evolved in microbes to catalyze the oxidative metabolism of fatty acids, using hydrogen peroxide as an oxidant rather than NAD(P)H-driven redox partner systems typical of the vast majority of other characterized P450 enzymes. Early members of the peroxygenase (CYP152) family were shown to catalyze hydroxylation at the α and β carbons of medium-to-long-chain fatty acids. However, more recent studies on other CYP152 family P450s revealed the ability to oxidatively decarboxylate fatty acids, generating terminal alkenes with potential applications as drop-in biofuels. Other research has revealed their capacity to decarboxylate and to desaturate hydroxylated fatty acids to form novel products. Structural data have revealed a common active site motif for the binding of the substrate carboxylate group in the peroxygenases, and mechanistic and transient kinetic analyses have demonstrated the formation of reactive iron-oxo species (compounds I and II) that are ultimately responsible for hydroxylation and decarboxylation of fatty acids, respectively. This short review will focus on the biochemical properties of the P450 peroxygenases and on their biotechnological applications with respect to production of volatile alkenes as biofuels, as well as other fine chemicals.

α-Oxidative decarboxylation of fatty acids catalysed by cytochrome P450 peroxygenases yielding shorter-alkyl-chain fatty acids

Shorter-alkyl-chain fatty acids such as tridecanoic acid or lauric acid were produced from myristic acid by CYP152 peroxygenases.

A Distal Loop Controls Product Release and Chemo- and Regioselectivity in Cytochrome P450 Decarboxylases.

Cytochrome P450 OleT utilizes hydrogen peroxide (H2O2) to catalyze the decarboxylation or hydroxylation of fatty acid (FA) substrates. Both reactions are initiated through the abstraction of a substrate hydrogen atom by the high-valent iron-oxo intermediate known as Compound I. Here, we specifically probe the influence of substrate coordination on OleT reaction partitioning through the combined use of fluorescent and electron paramagnetic resonance (EPR)-active FA probes and mutagenesis of a structurally disordered F-G loop that is distal from the heme-iron active site. Both probes are efficiently metabolized by OleT and efficiently trigger the formation of Compound I. Transient fluorescence and EPR reveal a slow product release step, mediated by the F-G loop, that limits OleT turnover. A single-amino acid change or excision of the loop reveals that this region establishes critical interactions to anchor FA substrates in place. The stabilization afforded by the F-G loop is essential for regulating regiospecific C-H abstraction and allowing for efficient decarboxylation to occur. These results highlight a regulatory strategy whereby the fate of activated oxygen species can be controlled at distances far removed from the site of chemistry.

Effect of water, fat, and protein in raw pork from swine carcasses on the pyrolytic gaseous and liquid product distribution

Pyrolysis is an effective way to dispose livestock carcasses. Pork is selected as meat from a representative carcass and the effect of its components (water, fat and protein) on the gaseous and liquid pyrolytic product distribution is investigated. Water has a significant influence on the amount of gaseous products formed, and its presence in raw pork (RP) leads to greater CO, H2, and CH4 yields through the steam gasification and steam reforming reactions. In addition, the presence of water results in higher conversion of N containing compounds into NH3, rather than HCN. Tar yields were mostly determined by the products obtained from the pyrolysis of fat, which include compounds derived from the cracking, decarboxylation, and decarbonylation of long chain fatty acids. The decomposition of protein led to the formation of small molecules like NH3, HCN, and phenols. In addition, protein and fat pyrolysis products react to form long chain amides and nitriles, increasing the tar yield. More toxic heterocyclic compounds are obtained in pyrolytic tar through the cyclisation of long chain hydrocarbons and nitriles under higher temperatures.

Continuous low pressure decarboxylation of fatty acids to fuel-range hydrocarbons with in situ hydrogen production

Fatty acids are considered as a renewable feedstock for the production of high value products such as fuel-range hydrocarbons. Decarboxylation can produce high quality fuels from fatty acids, although either high pressure or additional hydrogen is required. This study investigated a low pressure (<500psi) continuous decarboxylation process examining oleic acid in a continuous fixed bed reactor using activated carbon, which gave surprisingly high quality fuel-like hydrocarbons with no external hydrogen. The results showed that activated carbon performed as a catalyst for both decarboxylation and in situ hydrogen production. The reaction parameters for maximum degree of decarboxylation (91%) was found to be 400°C, 2h and water-to-oleic acid ratio of 4:1. To determine the degree of decarboxylation and reaction mechanism, the formed liquid products were examined by ATR-FTIR, Raman and GC-FID analysis, respectively. The liquid product was found to consist of mainly saturated hydrocarbons containing heptadecane (89.3% selectivity) as the major compound. The liquid product was found to have a similar density and higher heating value (HHV) to commercial diesel and jet fuel. The mechanism for decarboxylation reaction along with in situ hydrogen formation was proposed in this study.

Decarboxylation of Fatty Acids with Triruthenium Dodecacarbonyl: Influence of the Compound Structure and Analysis of the Product Mixtures.

Recently, the decarboxylation of oleic acid (9(Z)-octadecenoic acid) catalyzed by triruthenium dodecacarbonyl, Ru3(CO)12, to give a mixture of heptadecenes with concomitant formation of other hydrocarbons, heptadecane and C17 alkylbenzenes, was reported. The product mixture, consisting of about 77% heptadecene isomers, 18% heptadecane, and slightly >4% C17 alkylbenzenes, possesses acceptable diesel fuel properties. This reaction is now applied to other fatty acids of varying chain length and degree of saturation as well as double-bond configuration and position. Acids beyond oleic acid included in the present study are lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadecanoic), stearic (octadecanoic), petroselinic (6(Z)-octadecenoic), elaidic (9(E)-octadecenoic), asclepic (11(Z)-octadecenoic), and linoleic (9(Z),12(Z)-octadecadienoic) acids. Regardless of the chain length and degree of unsaturation, a similar product mixture was obtained in all cases with a mixture of alkenes predominating. Monounsaturated fatty acids, however, afforded the alkane with one carbon less than the parent fatty acid as the most prominent component in the mixture. Alkylbenzenes with one carbon atom less than the parent fatty acid were also present in all product mixtures. The number of isomeric alkenes and alkylbenzenes depends on the number of carbons in the chain of the parent fatty acid. With linoleic acid as the starting material, the amount of alkane was reduced significantly with alkenes and alkylaromatics enhanced compared to the monounsaturated fatty acids. Two alkenes, 9(E)-tetradecene and 1-hexadecene, were also studied as starting materials. A similar product mixture was observed but with comparatively minor amount of alkane formed and alkene isomers dominating at almost 90%. The double-bond position and configuration in the starting material do not influence the pattern of alkene isomers in the product mixture. The results underscore the multifunctionality of the Ru3(CO)12 catalyst, which promotes a reaction sequence including decarboxylation, isomerization, desaturation, hydrogenation, and cyclization (aromatization) to give a mixture of hydrocarbons simulating petrodiesel fuels. A reaction pathway is proposed to explain the existence of these products, in which alkenes are dehydrogenated to alkadienes and then, under cyclization, to the observed alkylaromatics. The liberated hydrogen can then saturate alkenes to the corresponding alkane.

Enabling the synthesis of medium chain alkanes and 1-alkenes in yeast

Microbial synthesis of medium chain aliphatic hydrocarbons, attractive drop-in molecules to gasoline and jet fuels, is a promising way to reduce our reliance on petroleum-based fuels. In this study, we enabled the synthesis of straight chain hydrocarbons (C7–C13) by yeast Saccharomyces cerevisiae through engineering fatty acid synthases to control the chain length of fatty acids and introducing heterologous pathways for alkane or 1-alkene synthesis. We carried out enzyme engineering/screening of the fatty aldehyde deformylating oxygenase (ADO), and compartmentalization of the alkane biosynthesis pathway into peroxisomes to improve alkane production. The two-step synthesis of alkanes was found to be inefficient due to the formation of alcohols derived from aldehyde intermediates. Alternatively, the drain of aldehyde intermediates could be circumvented by introducing a one-step decarboxylation of fatty acids to 1-alkenes, which could be synthesized at a level of 3mg/L, 25-fold higher than that of alkanes produced via aldehydes.

In vitro oxidative decarboxylation of free fatty acids to terminal alkenes by two new P450 peroxygenases

BackgroundP450 fatty acid decarboxylases represented by the unusual CYP152 peroxygenase family member OleTJE have been receiving great attention recently since these P450 enzymes are able to catalyze the simple and direct production of 1-alkenes for potential applications in biofuels and biomaterials. To gain more mechanistic insights, broader substrate spectra, and improved decarboxylative activities, it is demanded to discover and investigate more P450 fatty acid decarboxylases.ResultsHere, we describe for the first time the expression, purification, and in vitro biochemical characterization of two new CYP152 peroxygenases, CYP-Aa162 and CYP-Sm46Δ29, that are capable of decarboxylating straight-chain saturated fatty acids. Both enzymes were found to catalyze the decarboxylation and hydroxylation of a broad range of free fatty acids (C10–C20) with overlapping substrate specificity, yet distinct chemoselectivity. CYP-Sm46Δ29 works primarily as a fatty (lauric) acid decarboxylase (66.1 ± 3.9% 1-undecene production) while CYP-Aa162 more as a fatty (lauric) acid hydroxylase (72.2 ± 0.9% hydroxy lauric acid production). Notably, the optical spectroscopic analysis of functional CYP-Sm46Δ29 revealed no characteristic P450 band, suggesting a unique heme coordination environment. Active-site mutagenesis analysis showed that substitution with the proposed key decarboxylation-modulating residues, His85 and Ile170, enhanced the decarboxylation activity of CYP-Aa162 and P450BSβ, emphasizing the importance of these residues in directing the decarboxylation pathway. Furthermore, the steady-state kinetic analysis of CYP-Aa162 and CYP-Sm46Δ29 revealed both cooperative and substrate inhibition behaviors which are substrate carbon chain length dependent.ConclusionsOur data identify CYP-Sm46Δ29 as an efficient OleTJE-like fatty acid decarboxylase. Oxidative decarboxylation chemoselectivity of the CYP152 decarboxylases is largely dependent upon the carbon chain length of fatty acid substrates and their precise positioning in the enzyme active site. Finally, the kinetic mode analysis of the enzymes could provide important guidance for future process design.

Effects of maturity on the pyrolytic fingerprint of coals from North Borneo

Pyrolysis-gas chromatography-mass spectrometry (Py-GC–MS) and thermally assisted hydrolysis and methylation (THM-GC–MS) were applied to 27 coal samples of lignite to high volatile bituminous rank (vitrinite reflectance %Ro=0.28–0.66) from the Malaysian states of Sabah and Sarawak on Borneo, to investigate rank effects on molecular properties. The molecular fingerprints of these coals appeared to be controlled by diagenetic and, to a smaller extent, early catagenetic transformations (%Ro 0.28–0.50). The molecular assemblages from immature coals consist mainly of lignin-derived material and long-chain (≥C24) ester-bound polymethylene chains, whereas mature coals are enriched in short (C10–C25) free and/or trapped (isoprenoid) hydrocarbons, alkylated phenols and resinite aromatic derivatives. By comparing a large suite of potential molecular proxies of maturation (indices of pristane formation, resin aromatization, lignin alteration stages, etc.) and other maturity proxies (%Ro, Tmax), rank effects on different coal constituents are illustrated, as well as the suitability of the proxies for specific rank ranges. The results highlight the importance of decarboxylation of long-chain fatty acids (%Ro 0.35–0.40) and the progressive accumulation of resistant aryl-O (probably diaryl ether) bonds at advanced stages of maturity. The coals from Pinangah in Sabah were more mature than those from Sarawak (Mukah and Balingian coalfields), whereas the molecular signature of other coals from northeastern Sabah (Sandakan area) and southeastern Sabah (Silimpopon and Maliau areas) varied across the rank range studied.

An algal photoenzyme converts fatty acids to hydrocarbons.

Although many organisms capture or respond to sunlight, few enzymes are known to be driven by light. Among these are DNA photolyases and the photosynthetic reaction centers. Here, we show that the microalga Chlorella variabilis NC64A harbors a photoenzyme that acts in lipid metabolism. This enzyme belongs to an algae-specific clade of the glucose-methanol-choline oxidoreductase family and catalyzes the decarboxylation of free fatty acids to n-alkanes or -alkenes in response to blue light. Crystal structure of the protein reveals a fatty acid-binding site in a hydrophobic tunnel leading to the light-capturing flavin adenine dinucleotide (FAD) cofactor. The decarboxylation is initiated through electron abstraction from the fatty acid by the photoexcited FAD with a quantum yield >80%. This photoenzyme, which we name fatty acid photodecarboxylase, may be useful in light-driven, bio-based production of hydrocarbons.

High Quality Biowaxes from Fatty Acids and Fatty Esters: Catalyst and Reaction Mechanism for Accompanying Reactions

Biowaxes are interesting materials for pharmaceutical industry and consumer goods. Here the production of waxes from alternative renewable resources has been evaluated on the basis of the ketonic decarboxylation of fatty acids. The latter converts carboxylic acids (or their derivatives) into ketones with almost double chain length. Hence, sunflower oil was employed as starting material and passed over monoclinic zirconium. A wax fraction of 43% yield was obtained, though high content of molecules with more than 30 carbon atoms was not achieved due to prevalent carbon chain degradation. However, reaction of methyl stearate over zirconium oxide gave 60% wax fraction. Together with the waxes, an almost oxygen-free diesel fraction was obtained in more than 25% yield. Labeling experiments showed that the ketone intermediate is degraded by a radical chain mechanism. It is further concluded that methyl stearate radical formation is induced by carbon–carbon bond scission at high temperature whereas the glycerol p...