Effect of pro‐oxidants on biodegradation of polyethylene (LDPE) by indigenous fungal isolate,Aspergillus oryzae

Proxidant additives represent a promising solution to the problem of the environment contamination with polyethylene film litter. Pro‐oxidants accelerate photo‐ and thermo‐oxidation and consequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. In the present study, fungal strain, Aspergillus oryzae isolated from HDPE film (buried in soil for 3 months) utilized abiotically treated polyethylene (LDPE) as a sole carbon source and degraded it. Treatment with pro‐oxidant, manganese stearate followed by UV irradiation and incubation with A. oryzae resulted in maximum decrease in percentage of elongation and tensile strength by 62 and 51%, respectively, compared with other pro‐oxidant treated LDPE films which showed 45% (titanium stearate), 40% (iron stearate), and 39% (cobalt stearate) decrease in tensile strength. Fourier transform infrared (FTIR) analysis of proxidant treated LDPE films revealed generation of more number of carbonyl and carboxylic groups (1630–1840 cm⁻¹ and 1220–1340 cm⁻¹) compared with UV treated film. When these films were incubated with A. oryzae for 3 months complete degradation of carbonyl and carboxylic groups was achieved. Scanning electron microscopy of untreated and treated LDPE films also revealed that polymer has undergone degradation after abiotic and biotic treatments. This concludes proxidant treatment before UV irradiation accelerated photo‐oxidation of LDPE, caused functional groups to be generated in the polyethylene film and this resulted in biodegradation due to the consumption of carbonyl and carboxylic groups by A. oryzae which was evident by reduction in carbonyl peaks. Among the pro‐oxidants, manganese stearate treatment caused maximum degradation of polyethylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biodegradation of montmorillonite filled oxo‐biodegradable polyethylene

Oxo‐biodegradation of polyethylene has been well studied with different pro‐oxidants and it has been shown that pro‐oxidants have limited role in the oxidation of polyethylene and do not have any role in microbial growth. However, in few recent studies, montmorillonite clay has been reported to promote the growth of microbes by keeping the pH of the environment at levels conducive to growth. In an attempt to improve the overall oxo‐biodegradation of polyethylene, montmorillonite nanoclay has been used in this study along with a pro‐oxidant. Film samples of oxo‐biodegradable polyethylene (OPE) and oxo‐biodegradable polyethylene nanocomposite (OPENac) were subjected to abiotic oxidation followed by microbial degradation using microorganism Pseudomonas aeruginosa. The progress of degradation was followed by monitoring the chemical changes of the samples using high‐temperature gel permeation chromatography (GPC) and infrared spectroscopy (FTIR). The growth of bacteria on the surface of the polymer was monitored using environmental scanning electron microscopy. GPC data and FTIR results have shown that the abiotic oxidation of polyethylene is influenced significantly by the pro‐oxidant but not by nanoclay. But, the changes in molecular weight distribution and FTIR spectra for the biodegraded samples indicate that the growth rate of P. aeruginosa on OPENac is significantly greater than that on OPE. It indicates that nanoclay, by providing a favourable environment, helps in the growth of the microorganism and its utilisation of the polymer surface and the bulk of the polymer volume. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nitro-Oleic Acid Reduces J774A.1 Macrophage Oxidative Status and Triglyceride Mass: Involvement of Paraoxonase2 and Triglyceride Metabolizing Enzymes

Nitro‐fatty acids possess anti‐atherogenic properties, but their effects on macrophage oxidative status and lipid metabolism that play important roles in atherosclerosis development are unclear. This study compared the effects of nitro‐oleic acid (OLA‐NO₂) with those of native oleic acid (OLA) on intracellular reactive oxygen species (ROS) generation, anti‐oxidants and metabolism of triglycerides and cholesterol in J774A.1 macrophages. Upon incubating the cells with physiological concentrations of OLA‐NO₂ (0–1 µM) or with equivalent levels of OLA, ROS levels measured by 2, 7‐dichlorofluorescein diacetate, decreased dose‐dependently, but the anti‐oxidative effects of OLA‐NO₂ were significantly augmented. Copper ion addition increased ROS generation in OLA treated macrophages without affecting OLA‐NO₂ treated cells. These effects could be attributed to elevated glutathione levels and to increased activity and expression of paraoxonase2 that were observed in OLA‐NO₂vs OLA treated cells. Beneficial effects on triglyceride metabolism were noted in OLA‐NO₂vs OLA treated macrophages in which cellular triglycerides were reduced due to attenuated biosynthesis and accelerated hydrolysis of triglycerides. Accordingly, OLA‐NO₂ treated cells demonstrated down‐regulation of diacylglycerol acyltransferase1, the key enzyme in triglyceride biosynthesis, and increased expression of hormone‐sensitive lipase and adipose triglyceride lipase that regulate triglyceride hydrolysis. Finally, OLA‐NO₂vs OLA treatment resulted in modest but significant beneficial effects on macrophage cholesterol metabolism, reducing cholesterol biosynthesis rate and low density lipoprotein influx into the cells, while increasing high density lipoprotein‐mediated cholesterol efflux from the macrophages. Collectively, compared with OLA, OLA‐NO₂ modestly but significantly reduces macrophage oxidative status and cellular triglyceride content via modulation of cellular anti‐oxidants and triglyceride metabolizing enzymes.     

Model Development and Parameter Estimation for the Oxidation of Pyrrhotite‐Containing Rock Surfaces

A novel experimental method was developed for the evaluation of the biotic oxidation rate of waste rock containing sulphide minerals. Sized waste rock samples were inoculated with an Acidithiobacillus ferrooxidans suspension and sparged with discontinuing humidified air to yield the oxygen consumption rate. A kinetic/mass transport model was proposed based on oxidation of pyrrhotite. Bayesian statistical analysis using the Metropolis‐Hastings algorithm showed that at ambient oxygen concentration the mean (i.e., estimated) values of the initial oxygen flux, the reaction order, the oxygen diffusion coefficient through the oxidation product layer, and the surface reaction rate constant were 1.3×10^?7 mol/m².s, 0.55, 2.91×10^?13 m²/s and 3.23×10^?7 mol^0.45/m^0.35.s, respectively.     

On the kinetics of the autoxidation of fats. II. Monounsaturated substrates

The autoxidation of methyl oleate and oleic acid shows some differences as compared to the autoxidation of linoleate,e.g., the formation of water at an early stage. Linearization of experimental data on the autoxidation to high oxidation degrees of methyl oleate and other monounsaturated substrates shows that the rate equations previously derived for methyl linoleate in the range of 1–25% oxidation are valid, provided the correct expression for the remaining unreacted substrate is used. With monounsaturated substrates, part of the oxygen is consumed by a secondary oxidation reaction almost from the beginning, and only a certain constant fraction α of the total O₂ consumption is consumed in hydroperoxide formation. The fraction α is different for methyl oleate, oleyl alcohol, oleic acid andcis 9-octadecene, but the rate constant for the hydroperoxide formation is the same for all of them when experimental conditions are the same. The main difference between oleate and linoleate autoxidation is the much faster decomposition of the oleate hydroperoxides relative to their slow formation.     

Photodegradation and biodegradation by bacteria of mulching films based on ethylene‐vinyl acetate copolymer: Effect of pro‐oxidant additives

The photodegradation (432 h under irradiation of Xe‐Lamp‐solar filter) of an ethylene vinyl acetate (EVA) copolymer with vinyl acetate content of 9% was studied, and the effect of iron and calcium stearates was evaluated using different techniques such us attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), gel permeation chromatography (GPC), and thermal analysis methods (DSC and TGA). A re‐arrangement in crystallization and consequent decrease in thermal stability were found through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), which were in agreement with the chain scission tendency. The presence of Ca and Fe pro‐oxidants additives in EVA films increased the ketone carbonyl formation and decreased the ester absorption band of the acetate respect to the pure EVA, as it was evidenced by the significant changes in Carbonyl Indexes found by FTIR. The activity of stearates has been also evaluated by chemiluminescence, where the temperature‐ramping tests under nitrogen showed the formation of a peroxide peak at lower temperature. The lower stability of the films containing pro‐oxidants was evidenced by the values of oxidation induction time (OIT) determined by DSC. The results were supported by GC‐MS, where the concentration of extracted products identified in the EVA containing pro‐oxidants was significant and a much greater decrease in molecular weight was determined by GPC, which confirmed the development of degradation for EVA with Ca and Fe stearates in comparison to pure EVA. Biodegradation of photodegraded EVA films were studied at 45°C during 90 days using a mixture of Bacillus (MIX) (B. cereus, B. megaterium, and B. subtilis) and, in parallel, by Brevibacillus borstelensis as reference strain. Biodegradation of EVA‐films was studied by Chemiluminescence, ATR‐FTIR and GC‐product analysis and the data confirm more efficient biodegradation on the materials containing pro‐oxidants. The chemiluminescence emissions due to decomposition of oxidation species was observed at lower temperatures on the biodegraded samples. Also, the drastic decrease of carbonyl index and the disappearance of photogenerated low molecular products with biodegradation were more efficient on the biodegraded films containing pro‐oxidants. EVA mineralization was evaluated by carbon dioxide measurement using indirect impedance technique. Biodegradation by B. borstelensis and MIX at 45°C was similar and exhibited a pronounced difference between the pure photodegraded EVA film (around 15% of mineralization) and the corresponding photodegraded films containing Ca and Fe stearates where biodegradation extent reached values of 23‐26% of biodegradation after 90 days. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Wear resistance of low‐temperature plasma‐polymerized organosilica deposited on poly(ethylene terephthalate): The effect of discharge powers

An investigation was conducted into plasma polymerization of transparent organosilica (SiO_xC_y) onto flexible transparent polyethylene terephthalate (PET) substrates for improving wear resistance. The plasma‐polymerized SiO_xC_y with tetramethylsilane (TMS) and oxygen (O₂) gases in room temperature (23°C) was proven to highly enhance the wear resistance from the completely worn of untreated PET substrates to no worn of TMS‐oxygen plasma‐polymerized PET substrates at higher discharge powers, while the wear test of 300 cycles at 300 g loading with a steel wool was applied. The performance of wear resistance on PET substrates was found to be strongly dependent on the surface characteristics of PET substrates. The surface hardness of PET substrates was determined by the pencil test. The surface morphology of PET substrate was observed by atomic force microscopy (AFM). The atomic compositions and chemical bondings of TMS‐oxygen plasma‐polymerized organosilicas were analyzed by means of X‐ray photoelectron spectroscopy (XPS). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New Insights into the Anti‐Inflammatory and Antioxidant Properties of Nitrated Phospholipids

Nitro‐fatty acids (NO₂‐FA) have been widely studied with regard to their identification, structural characterization, and biological actions. NO₂‐FA could also be present endogenously esterified to phospholipids (PL), and NO₂‐PL were already detected in cardiac mitochondria from diabetic rats and cardiomyoblasts subjected to starvation. However, the biological actions of NO₂‐PL have been overlooked. In this study, we evaluate the antioxidant and anti‐inflammatory potential of the nitrated 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (POPC) formed in vitro by incubation with NO₂BF₄, in a well‐recognized mimetic model of nitroxidative stress. Nitrated POPC showed anti‐radical ability to reduce both 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH^?) (IC₂₀ = 225 ± 4 μg/mL; Trolox equivalent (TE) = 86 ± 6 μmol Trolox/g lipid) and 2,2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulfonic acid radical cation (ABTS^?+) (IC₅₀ = 124 ± 2 μg/mL; TE = 152 ± 9 μmol Trolox/g lipid). Also, higher lag times were achieved in oxygen radical absorbance capacity (ORAC) assay for nitrated POPC, indicating a faster reaction with oxygen‐derived radicals (TE = 1.03 ± 0.22 and TE = 1.30 ± 0.16 mmol Trolox/g lipid for nonmodified and nitrated POPC, respectively). Nitrated POPC showed the ability to inhibit lipid oxidation induced by the hydroxyl radical generated under Fenton reaction conditions, monitored by electrospray ionization (ESI) mass spectrometry (MS) using phosphatidylcholine (PtdCho) liposomes as a model of cell membrane. Nitrated POPC showed anti‐inflammatory potential, as assessed by the inhibition of inducible nitric oxide synthase (iNOS) expression in RAW 264.7 macrophages activated by the Toll‐like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) in a well‐described in vitro model of inflammation. Altogether, this study provides new clues regarding the antioxidant and anti‐inflammatory potential of nitrated POPC, which should be explored in depth.     

Aerobic Oxidation of Cyclohexane using N‐Hydroxyphthalimide Bearing Fluoroalkyl Chains

The N‐hydroxyphthalimide derivatives, F₁₅‐ and F₁₇‐NHPI, bearing a long fluorinated alkyl chain, were prepared and their catalytic performances were compared with that of the parent compound, N‐hydroxyphthalimide (NHPI). The oxidation of cyclohexane under 10 atm of air in the presence of fluorinated F₁₅‐ or F₁₇‐NHPI, cobalt diacetate [Co(OAc)₂], and manganese diacetate [Mn(OAc)₂] without any solvent at 100 °C afforded a mixture of cyclohexanol and cyclohexanone (K/A oil) as major products along with a small amount of adipic acid. It was found that F₁₅‐ and F₁₇‐NHPI exhibit higher catalytic activity than NHPI for the oxidation of cyclohexane without a solvent. However, for the oxidation in acetic acid all of these catalysts afforded adipic acid as a major product in good yield and the catalytic activity of NHPI in acetic acid was almost the same as those of F₁₅‐ and F₁₇‐NHPI. The oxidation by F₁₅‐ and F₁₇‐NHPI catalysts in trifluorotoluene afforded K/A oil in high selectivity with little formation of adipic acid, while NHPI was a poor catalyst under these conditions, forming K/A oil as well as adipic acid in very low yields. The oxidation in trifluorotoluene by F₁₅‐ and F₁₇‐NHPI catalysts was considerably accelerated by the addition of a small amount of zirconium(IV) acetylacetonate [Zr(acac)₄] to the present catalytic system to afford selectively K/A oil, but no such effect was observed in the NHPI‐catalyzed oxidation in trifluorotoluene.     

Oxidation kinetics in olive oil triacylglycerols under accelerated shelf‐life testing (25–75 °C)

A kinetic study of the autoxidation reaction in olive oil triacylglycerols stored in darkness at different temperatures (25, 40, 50, 60 and 75 °C), in absence of pro‐ and antioxidant compounds to avoid confounding effects, is described. After the induction period (IP) the decrease in the oxidizing substrate and the formation of primary oxidation products followed a pseudo‐zero‐order kinetic, and the calculated E_a from the Arrhenius equation for the formation of hydroperoxides was 32.1 kJ·mol^?1. The formation of secondary oxidation products followed a pseudo‐first‐order kinetic whose rate reaction constant also increased exponentially with temperature. The first oxidation index to exceed the upper limit in the EU regulations was PV, followed by K₂₃₂ and K₂₇₀. The time required reaching these limits and the rancidity threshold showed a potential dependence on temperature, and therefore with accelerated storage at 75 °C, POO shelf‐life in ambient conditions (25 °C) can be predicted. Finally, there was a good linear relationship between the time required to reach the rancidity threshold and the IP of the formation of the 2,4‐decadienal, and hence this instrumental determination could be useful to measure sensory recognition of the rancid defect in POO.     

Feasibility of a Co Oxygen Carrier for Chemical Looping Air Separation: Thermodynamics and Kinetics

Chemical looping air separation (CLAS) is based on the chemical looping principle: oxygen carriers release oxygen to carrier gas in a reduction reactor and absorb oxygen from air in an oxidation reactor. High oxygen transport capacity, high reactivity in reduction and oxidation reactions, and resistance to attrition and agglomeration are some of the criteria that feasible oxygen carrier materials should fulfill. Thermodynamic analysis was applied to prove the potential of Co₃O₄ as oxygen carrier. ZrO₂ served as binder to improve the anti‐sintering property and reactivity. Kinetic experiments were performed to determine the reaction rate and conversion of the oxygen carrier. Stability and durability of the oxygen carrier were characterized before and after cyclic experiments. The Co/Zr oxygen carrier proved to be a suitable candidate for the CLAS process.     

Oxidation of alcohols with tert-butylhydroperoxide catalyzed by Mn (II) complexes immobilized in the pore channels of mesoporous hexagonal molecular sieves (HMS)

The oxidation of alcohols with tert-butylhydroperoxide (TBHP), in the presence of Mn²⁺ complexes immobilized in the pore channels of mesoporous hexagonal molecular sieves (HMS), were investigated. It was found that immobilized [Mn(bpy)₂]²⁺/HMS is an efficient catalyst for the oxidation of alcohols such as benzyl alcohol, n-hexanol and cyclohexanol. The effects of reaction time, amount of Mn²⁺ in the catalyst, type of substrates and oxidants in this catalysis system were investigated. At optimum conditions, TBHP is more efficient oxidant with respect to H₂O₂. Following order has been observed for the percentage of conversions of alcohols: benzylic >1° >2°.     

Stereoselective hydride transfer by aryl-alcohol oxidase, a member of the GMC superfamily

Primary alcohol oxidation by aryl‐alcohol oxidase (AAO), a flavoenzyme providing H₂O₂ to ligninolytic peroxidases, is produced by concerted proton and hydride transfers, as shown by substrate and solvent kinetic isotope effects (KIEs). Interestingly, when the reaction was investigated with synthesized (R)‐ and (S)‐α‐deuterated p‐methoxybenzyl alcohol, a primary KIE (≈6) was observed only for the R enantiomer, revealing that the hydride transfer is highly stereoselective. Docking of p‐methoxybenzyl alcohol at the buried crystal active site, together with QM/MM calculations, showed that this stereoselectivity is due to the position of the hydride‐ and proton‐receiving atoms (flavin N5 and His502 Nε, respectively) relative to the alcohol Cα‐substituents, and to the concerted nature of transfer (the pro‐S orientation corresponding to a 6 kcal mol^?1 penalty with respect to the pro‐R orientation). The role of His502 is supported by the lower activity (by three orders of magnitude) of the H502A variant. The above stereoselectivity was also observed, although activities were much lower, in AAO reactions with secondary aryl alcohols (over 98 % excess of the R enantiomer after treatment of racemic 1‐(p‐methoxyphenyl)ethanol, as shown by chiral HPLC) and especially with use of the F501A variant. This variant has an enlarged active site that allow better accommodation of the α‐substituents, resulting in higher stereoselectivity (S/R ratios) than is seen with AAO. High enantioselectivity in a member of the GMC oxidoreductase superfamily is reported for the first time, and shows the potential for engineering of AAO for deracemization purposes.     

Catalytic oxidation of solid carbon and carbon monoxide over cerium‐zirconium mixed oxides

A series of cerium‐zirconium mixed oxides was prepared and evaluated in the catalytic oxidation of solid coke with 10 vol % O₂ in He at 673 K using a thermogravimetric analyzer. The measured first order rate constant for coke oxidation was proportional to the catalyst loading when the mass ratio of catalyst to coke was low, which enabled the calculation of a surface area specific reaction rate. The validity of the normalization method was confirmed by performing CO oxidation over the cerium‐zirconium mixed oxides in a fixed bed reactor at 573 K. Although there was no correlation between the coke oxidation rate and the oxygen storage capacity or the reducibility of the catalysts, there was an excellent correlation to the CO oxidation rate. Kinetic studies of both coke and CO oxidation suggested an important role of surface lattice oxygen from the catalyst in the two reactions. © 2016 American Institute of Chemical Engineers AIChE J, 63: 725–738, 2017     

Behaviour of cod liver oil during the autoxidation process

Prostaglandin‐like compounds, called isoprostanes, are generated by free enzyme‐independent radical peroxidation of the acids arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic (DHA). Up to now, isoprostanes have been largely studied only in men and biological systems, but never in food. In this research, cod liver oil was used as a model system to study the oxidation mechanism in food containing high amounts of EPA and DHA. For comparison, under similar oxidation conditions, also the behaviour of a sunflower seed oil and an n‐3 long‐chain polyunsaturated fatty acid capsule supplement oil were studied. It was ascertained that EPA‐ and DHA‐derived compounds were formed during oxidation. These compounds were polar and easily isolatable by methanol from oxidised transmethylated oil. EPA and DHA oxidation derivatives showed maximal absorbance at 200 nm and were very potent pro‐oxidants at high temperatures. In oxidised sunflower oil, similar compounds did not form. Unfortunately, the chemical structures of the EPA and DHA oxidation derivatives were not discovered, but it is a realistic hypothesis that they could be isoprostane‐like compounds.     

Electrocatalysis and electrochemical promotion of CO oxidation in PEM fuel cells: the role of oxygen crossover

The electrochemical promotion of catalysis (or NEMCA effect) was studied for the CO oxidation and water gas shift reaction on a Pt anode in a polymer electrolyte membrane (PEM) fuel cell. It was found that this phenomenon plays a significant role in a normal fuel cell operation (fuel mixture – air) but not in a hydrogen pumping operation (fuel mixture – H₂). This implies that the role of oxygen crossover in the electropromotion (EP) of CO oxidation is vital. During fuel cell operation, the increase in the rate of CO consumption is 2.5 times larger than the electrochemical rate, I/2F of CO oxidation, while for oxygen bleeding conditions (fuel mixture + O₂−air) the increase is five times larger than I/2F. This shows that the catalytic properties of the Pt anode are significantly modified by varying the catalyst potential. In order to confirm the role of oxygen crossover, Nafion membranes (117, 1135) with different thickness, were studied. The results show that upon decreasing the membrane thickness the crossover is increased and thus the electrochemical promotion effect becomes more pronounced.     

Effect of Dopants on the Distribution of Aluminum and Oxygen Fluxes in Polycrystalline Alumina Under Oxygen Potential Gradients at High Temperatures

The oxygen permeability of Lu‐, Y‐, and Hf‐doped polycrystalline alumina wafers under steep oxygen potential gradients was evaluated at temperatures above 1773 K. Oxygen permeation occurred by the grain‐boundary (GB) diffusion of oxygen from the higher oxygen partial pressure (P_O2) surface to the lower P_O2 surface, and was coincident with GB diffusion of aluminum in the reverse direction. Lu‐ and Y‐doping both suppressed oxygen permeation to the same extent, owing to the decrease in oxygen mobility, but neither had any significant effect on aluminum mobility. Hf‐doping had the opposite effect. The fluxes of oxygen and aluminum at the inflow side in all wafers were significantly smaller than those at the outflow side, regardless of whether or not these dopants were added. Consequently, the intersection of the fluxes shifted to the lower P_O2 side upon Lu‐ and Y‐doping, and to the higher P_O2 side upon Hf‐doping. Furthermore, the effect of dopants on the mass transfer in scales formed by oxidation of FeCrAl‐based alloys at 1300–1500 K was analyzed through predictions of the flux distributions of oxygen and aluminum in the scales.     

Nitric oxide emissions and temperature evolution during the char grate‐fired process

Understanding the char grate‐fired process is key to developing a low‐nitric oxide (NO) technology for industrial boilers. In this work, char combustion and NO emissions during a grate‐fired process were studied in a small‐scale one‐dimensional fixed‐bed system by adjusting the char/oxygen (O₂) ratio. Evolution of the surface temperature of the char bed was measured using an infrared temperature measurement system. As the char/O₂ ratio increased, a reaction layering of the char bed occurred. The char bed can be divided into oxygen‐absent and ‐present parts in time, and into reduction and oxidation layers in space. This kind of division was determined by the complete oxidation layer that could deplete all O₂. The reduction layer could reduce NO emissions well. With the increase of the char/O₂ ratio, the char mass proportion of the oxygen‐absent part increased, while that of the oxygen‐present decreased; and the NO emissions and conversion rate of char nitrogen decreased. When combustion began, char started to burn and released a large amount of heat, and the surface temperatures of both the oxidation and reduction layers increased, with a larger rise of the former of about 260 °C. As the reaction proceeded, the surface temperature of the oxidation layer gradually decreased, while that of the reduction layer increased until the char bed was burnt through.     

Contribution of the Internal and External Oxygen to the Oxidation of Microencapsulated Fish Oil

Microencapsulation aims to protect polyunsaturated fatty acids against oxidation by embedding oil droplets in a solid matrix. In such a system the internal (dissolved and entrapped) and external (in the environment) oxygen can be differentiated. The study aims to quantify the impact of both oxygen sources on the oxidation of microencapsulated fish oil. The impact of the solubilized oxygen in bulk fish oil is investigated by saturating the oil with nitrogen, synthetic air, and pure oxygen. Even though more dissolved oxygen results in more oxidation products, the difference between the oxidation of the nitrogen and air saturated oil is significant but low. For encapsulated fish oil powders, the internal oxygen is modified by preparing oil‐in‐water emulsions under atmospheric and inert conditions. The feed is atomized and spray dried with either nitrogen or air. Powders are stored under vacuum and in vials and the hydroperoxides and anisidine value are determined in the total‐ and encapsulated oil. The internal oxygen has a minor impact, whereas the external oxygen is the main determinant for autoxidation. Apart from oxidizing the non‐encapsulated oil, the external O₂ penetrates into the particle and reacts with the encapsulated oil. Practical Applications: Comparing the contribution of the internal and external oxygen to the oxidative stability shows that the internal O₂ plays a minor role and can be neglected. This means that the emulsion preparation as well as the spray drying process can be conducted under ambient conditions. An inert production is not extending the shelf life significantly as long as the external O₂ determines oxidation. The focus should be on optimizing the diffusion barrier properties of the wall matrix to reduce the penetration of the external oxygen into the particle system. Alternatively, packaging solution reducing the external O₂ will extend the shelf life of the microencapsulated oil.     

Enhancing co‐production of H2 and syngas via water splitting and POM on surface‐modified oxygen permeable membranes

In this article, we report a detailed study on co‐production of H₂ and syngas on La_0.9Ca_0.1FeO_3?δ (LCF‐91) membranes via water splitting and partial oxidation of methane, respectively. A permeation model shows that the surface reaction on the sweep side is the rate limiting step for this process on a 0.9 mm‐thick dense membrane at 990°C. Hence, sweep side surface modifications such as adding a porous layer and nickel catalysts were applied; the hydrogen production rate from water thermolysis is enhanced by two orders of magnitude to 0.37 μmol/cm²?s compared with the results on the unmodified membrane. At the sweep side exit, syngas (H₂/CO = 2) is produced and negligible solid carbon is found. Yet near the membrane surface on the sweep side, methane can decompose into solid carbon and hydrogen at the surface, or it may be oxidized into CO and CO₂, depending on the oxygen permeation flux. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4427–4435, 2016