Continuous enzymatic interesterification of lard and soybean oil blend: Effects of different flow rates on physical properties and acyl migration

Continuous enzymatic interesterification is an alternative to chemical interesterification for lipid modification technology which is economically viable for large scale use. A blend of 70% lard and 30% soybean oil was submitted to continuous enzymatic interesterification in a glass tubular bioreactor at flow rate ranging from 0.5 to 4.5 mL/min. The original mixture and the reaction products obtained were examined to determine melting and crystallization behavior by DSC, and analyzed for regiospecific fatty acid distribution. Continuous enzymatic interesterification changed the mixture, forming a new triacylglycerol composition, verified by DSC curves and variation in enthalpy of melting values. The regiospecific distribution of fatty acids was changed by flow variations in the reactor. In the continuous enzymatic interesterification reaction the flow rate of 4.5 mL/min, was more advantageous than slower flow rates, reducing acyl migration and increasing process productivity. (C) 2011 Elsevier B.V. All rights reserved.

EDGE-PRESERVING SPECKLE TEXTURE REMOVAL BY INTERFERENCE-BASED SPECKLE FILTERING FOLLOWED BY ANISOTROPIC DIFFUSION

Ultrasonography has an inherent noise pattern, called speckle, which is known to hamper object recognition for both humans and computers. Speckle noise is produced by the mutual interference of a set of scattered wavefronts. Depending on the phase of the wavefronts, the interference may be constructive or destructive, which results in brighter or darker pixels, respectively. We propose a filter that minimizes noise fluctuation while simultaneously preserving local gray level information. It is based on steps to attenuate the destructive and constructive interference present in ultrasound images. This filter, called interference-based speckle filter followed by anisotropic diffusion (ISFAD), was developed to remove speckle texture from B-mode ultrasound images, while preserving the edges and the gray level of the region. The ISFAD performance was compared with 10 other filters. The evaluation was based on their application to images simulated by Field II (developed by Jensen et al.) and the proposed filter presented the greatest structural similarity, 0.95. Functional improvement of the segmentation task was also measured, comparing rates of true positive, false positive and accuracy. Using three different segmentation techniques, ISFAD also presented the best accuracy rate (greater than 90% for structures with well-defined borders). (E-mail: fernando.okara@gmail.com) (C) 2012 World Federation for Ultrasound in Medicine & Biology.

Effects of tannery sludge application on physiological and fatty acid profiles of the soil microbial community

The impact of tannery sludge application on soil microbial community and diversity is poorly understood. We studied the microbial community in an agricultural soil following two applications (2006 and 2007) of tannery sludge with annual application rates of 0.0,2.3 and 22.6 Mg ha(-1). The soil was sampled 12 and 271 days after the second (2007) application. Community structure was assessed via a phospholipid fatty acid analysis, and the physiological profile of the soil microbial community via the Biolog method. Tannery sludge application changed soil chemical properties, increasing the soil pH and electrical conductivity as well as available P and mineral N concentrations. The higher sludge application rate changed the community structure and the physiological profile of the microbial community at both sampling dates. However, there is no clear link between community structure and carbon substrate utilization. According to the Distance Based Linear Models Analysis, the fatty acids 16:0 and 117:0 together contributed 84% to the observed PLFA patterns, whereas the chemical properties available P, mineral N, and Ca, and pH together contributed 54%. At 12 days, tannery sludge application increased the average well color development from 0.46 to 0.87 after 48 h, and reduced the time elapsed before reaching the midpoint carbon substrate utilization (s) from 71 to 44 h, an effect still apparent nine months after application of the higher sludge application rate. The dominant signature fatty acids and kinetic parameters (r and s) were correlated to the concentrations of available P. Ca, mineral N, pH and EC. (c) 2012 Elsevier B.V. All rights reserved.

Removal from the plasma of the free and esterified forms of cholesterol and transfer of lipids to HDL in type 2 diabetes mellitus patients

Background: The aim was to investigate new markers for type 2 diabetes (T2DM) dyslipidemia related with LDL and HDL metabolism. Removal from plasma of free and esterified cholesterol transported in LDL and the transfer of lipids to HDL are important aspects of the lipoprotein intravascular metabolism. The plasma kinetics (fractional clearance rate, FCR) and transfers of lipids to HDL were explored in T2DM patients and controls, using as tool a nanoemulsion that mimics LDL lipid structure (LDE). Results: C-14- cholesteryl ester FCR of the nanoemulsion was greater in T2DM than in controls (0.07 +/- 0.02 vs. 0.05 +/- 0.01 h(-1), p = 0.02) indicating that LDE was removed faster, but FCR H-3- cholesterol was equal in both groups. Esterification rates of LDE free-cholesterol were equal. Cholesteryl ester and triglyceride transfer from LDE to HDL was greater in T2DM (4.2 +/- 0.8 vs. 3.5 +/- 0.7%, p = 0.03 and 6.8 +/- 1.6% vs. 5.0 +/- 1.1, p = 0.03, respectively). Phospholipid and free cholesterol transfers were not different. Conclusions: The kinetics of free and esterified cholesterol tended to be independent in T2DM patients and the lipid transfers to HDL were also disturbed. These novel findings may be related with pathophysiological mechanisms of diabetic macrovascular disease.

High dosage folic acid supplementation, oral cleft recurrence and fetal growth

Objectives: To evaluate the effects of folic acid supplementation on isolated oral cleft recurrence and fetal growth. Patients and Methods: The study included 2,508 women who were at-risk for oral cleft recurrence and randomized into two folic acid supplementation groups: 0.4 and 4 mg per day before pregnancy and throughout the first trimester. The infant outcome data were based on 234 live births. In addition to oral cleft recurrence, several secondary outcomes were compared between the two folic acid groups. Cleft recurrence rates were also compared to historic recurrence rates. Results: The oral cleft recurrence rates were 2.9% and 2.5% in the 0.4 and 4 mg groups, respectively. The recurrence rates in the two folic acid groups both separately and combined were significantly different from the 6.3% historic recurrence rate post the folic acid fortification program for this population (p = 0.0009 when combining the two folic acid groups). The rate of cleft lip with palate recurrence was 2.9% in the 0.4 mg group and 0.8% in the 4 mg group. There were no elevated fetal growth complications in the 4 mg group compared to the 0.4 mg group. Conclusions: The study is the first double-blinded randomized clinical trial (RCT) to study the effect of high dosage folic acid supplementation on isolated oral cleft recurrence. The recurrence rates were similar between the two folic acid groups. However, the results are suggestive of a decrease in oral cleft recurrence compared to the historic recurrence rate. A RCT is still needed to identify the effect of folic acid on oral cleft recurrence given these suggestive results and the supportive results from previous interventional and observational studies, and the study offers suggestions for such future studies. The results also suggest that high dosage folic acid does not compromise fetal growth

Effects of pretreatment on morphology, chemical composition and enzymatic digestibility of eucalyptus bark: a potentially valuable source of fermentable sugars for biofuel production – part 1

Abstract Background In recent years, the growing demand for biofuels has encouraged the search for different sources of underutilized lignocellulosic feedstocks that are available in sufficient abundance to be used for sustainable biofuel production. Much attention has been focused on biomass from grass. However, large amounts of timber residues such as eucalyptus bark are available and represent a potential source for conversion to bioethanol. In the present paper, we investigate the effects of a delignification process with increasing sodium hydroxide concentrations, preceded or not by diluted acid, on the bark of two eucalyptus clones: Eucalyptus grandis (EG) and the hybrid, E. grandis x urophylla (HGU). The enzymatic digestibility and total cellulose conversion were measured, along with the effect on the composition of the solid and the liquor fractions. Barks were also assessed using Fourier-transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR), X-Ray diffraction, and scanning electron microscopy (SEM). Results Compositional analysis revealed an increase in the cellulose content, reaching around 81% and 76% of glucose for HGU and EG, respectively, using a two-step treatment with HCl 1%, followed by 4% NaOH. Lignin removal was 84% (HGU) and 79% (EG), while the hemicellulose removal was 95% and 97% for HGU and EG, respectively. However, when we applied a one-step treatment, with 4% NaOH, higher hydrolysis efficiencies were found after 48 h for both clones, reaching almost 100% for HGU and 80% for EG, in spite of the lower lignin and hemicellulose removal. Total cellulose conversion increased from 5% and 7% to around 65% for HGU and 59% for EG. NMR and FTIR provided important insight into the lignin and hemicellulose removal and SEM studies shed light on the cell-wall unstructuring after pretreatment and lignin migration and precipitation on the fibers surface, which explain the different hydrolysis rates found for the clones. Conclusion Our results show that the single step alkaline pretreatment improves the enzymatic digestibility of Eucalyptus bark. Furthermore, the chemical and physical methods combined in this study provide a better comprehension of the pretreatment effects on cell-wall and the factors that influence enzymatic digestibility of this forest residue.

Protein turnover, amino acid requirements and recommendations for athletes and active populations

Skeletal muscle is the major deposit of protein molecules. As for any cell or tissue, total muscle protein reflects a dynamic turnover between net protein synthesis and degradation. Noninvasive and invasive techniques have been applied to determine amino acid catabolism and muscle protein building at rest, during exercise and during the recovery period after a single experiment or training sessions. Stable isotopic tracers (13C-lysine, 15N-glycine, ²H5-phenylalanine) and arteriovenous differences have been used in studies of skeletal muscle and collagen tissues under resting and exercise conditions. There are different fractional synthesis rates in skeletal muscle and tendon tissues, but there is no major difference between collagen and myofibrillar protein synthesis. Strenuous exercise provokes increased proteolysis and decreased protein synthesis, the opposite occurring during the recovery period. Individuals who exercise respond differently when resistance and endurance types of contractions are compared. Endurance exercise induces a greater oxidative capacity (enzymes) compared to resistance exercise, which induces fiber hypertrophy (myofibrils). Nitrogen balance (difference between protein intake and protein degradation) for athletes is usually balanced when the intake of protein reaches 1.2 g·kg-1·day-1 compared to 0.8 g·kg-1·day-1 in resting individuals. Muscular activities promote a cascade of signals leading to the stimulation of eukaryotic initiation of myofibrillar protein synthesis. As suggested in several publications, a bolus of 15-20 g protein (from skimmed milk or whey proteins) and carbohydrate (± 30 g maltodextrine) drinks is needed immediately after stopping exercise to stimulate muscle protein and tendon collagen turnover within 1 h.

Environmental assessment of residues generated after consecutive acid-base pretreatment of sugarcane bagasse by advanced oxidative process

Abstract Background Biofuels produced from sugarcane bagasse (SB) have shown promising results as a suitable alternative of gasoline. Biofuels provide unique, strategic, environmental and socio-economic benefits. However, production of biofuels from SB has negative impact on environment due to the use of harsh chemicals during pretreatment. Consecutive sulfuric acid-sodium hydroxide pretreatment of SB is an effective process which eventually ameliorates the accessibility of cellulase towards cellulose for the sugars production. Alkaline hydrolysate of SB is black liquor containing high amount of dissolved lignin. Results This work evaluates the environmental impact of residues generated during the consecutive acid-base pretreatment of SB. Advanced oxidative process (AOP) was used based on photo-Fenton reaction mechanism (Fenton Reagent/UV). Experiments were performed in batch mode following factorial design L9 (Taguchi orthogonal array design of experiments), considering the three operation variables: temperature (°C), pH, Fenton Reagent (Fe2+/H2O2) + ultraviolet. Reduction of total phenolics (TP) and total organic carbon (TOC) were responsive variables. Among the tested conditions, experiment 7 (temperature, 35°C; pH, 2.5; Fenton reagent, 144 ml H2O2+153 ml Fe2+; UV, 16W) revealed the maximum reduction in TP (98.65%) and TOC (95.73%). Parameters such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), BOD/COD ratio, color intensity and turbidity also showed a significant change in AOP mediated lignin solution than the native alkaline hydrolysate. Conclusion AOP based on Fenton Reagent/UV reaction mechanism showed efficient removal of TP and TOC from sugarcane bagasse alkaline hydrolysate (lignin solution). To the best of our knowledge, this is the first report on statistical optimization of the removal of TP and TOC from sugarcane bagasse alkaline hydrolysate employing Fenton reagent mediated AOP process.

Palmitoleic acid (n-7) increases white adipocyte lipolysis and lipase content in a PPARα-dependent manner

We investigated whether palmitoleic acid, a fatty acid that enhances whole body glucose disposal and suppresses hepatic steatosis, modulates triacylglycerol (TAG) metabolism in adipocytes. For this, both differentiated 3T3-L1 cells treated with either palmitoleic acid (16:1n7, 200 μM) or palmitic acid (16:0, 200 μM) for 24 h and primary adipocytes from wild-type or PPARα-deficient mice treated with 16:1n7 (300 mg•kg(-1)•day(-1)) or oleic acid (18:1n9, 300 mg•kg(-1)•day(-1)) by gavage for 10 days were evaluated for lipolysis, TAG, and glycerol 3-phosphate synthesis and gene and protein expression profile. Treatment of differentiated 3T3-L1 cells with 16:1n7, but not 16:0, increased basal and isoproterenol-stimulated lipolysis, mRNA levels of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) and protein content of ATGL and pSer(660)-HSL. Such increase in lipolysis induced by 16:1n7, which can be prevented by pharmacological inhibition of PPARα, was associated with higher rates of PPARα binding to DNA. In contrast to lipolysis, both 16:1n7 and 16:0 increased fatty acid incorporation into TAG and glycerol 3-phosphate synthesis from glucose without affecting glyceroneogenesis and glycerokinase expression. Corroborating in vitro findings, treatment of wild-type but not PPARα-deficient mice with 16:1n7 increased primary adipocyte basal and stimulated lipolysis and ATGL and HSL mRNA levels. In contrast to lipolysis, however, 16:1n7 treatment increased fatty acid incorporation into TAG and glycerol 3-phosphate synthesis from glucose in both wild-type and PPARα-deficient mice. In conclusion, palmitoleic acid increases adipocyte lipolysis and lipases by a mechanism that requires a functional PPARα

Dynamics of follicular growth and progesterone concentrations in cyclic and anestrous suckling Nelore cows (Bos indicus) treated with progesterone, equine chorionic gonadotropin, or temporary calf removal

The objective of this study was to investigate the effects of eCG and temporary calf removal (TCR) associated with progesterone (P4) treatment on the dynamics of follicular growth, CL size, and P4 concentrations in cyclic (n ¼ 36) and anestrous (n ¼ 30) Nelore cows. Cyclic (C) and anestrous (A) cows were divided into three groups. The control group received 2 mg of estradiol benzoate via intramuscular (IM) injection and an intravaginal device containing 1.9 g of P4 on Day 0. On Day 8, the device was removed, and the animals received 12.5 mg of dinoprost tromethamine IM. After 24 hours, the animals received 1 mg of estradiol benzoate IM. In the eCG group, cows received the same treatment described for the control group but also received 400 UI of eCG at the time of device removal. In the TCR group, calves were separated from the cows for 56 hours after device removal. Ultrasound exams were performed every 24 hours after device removal until the time of ovulation and 12 days after ovulation to measure the size of the CL. On the same day as the CL measurement, blood was collected to determine the plasma P4 level. Statistical analyses were performed with a significance level of P ≤ 0.05. In cyclic cows, the presence of the CL at the beginning of protocol resulted in a smaller follicle diameter at the time of device removal (7.4 ± 0.3 mm in cows with CL vs. 8.9 ± 0.4 mm in cows without CL; P ¼ 0.03). All cows ovulated within 72 hours after device removal. Anestrous cows treated with eCG or TCR showed follicle diameter at fixed-timed artificial insemination (A-eCG 10.2 ± 0.3 and A-TCR 10.3 ± 0.5 mm) and follicular growth rate (A-eCG 1.5 ± 0.2 and A-TCR 1.3 ± 0.1 mm/day) similar to cyclic cows (C-eCG 11.0 ± 0.6 and C-TCR 12.0 ± 0.5 mm) and (C-eCG 1.4 ± 0.2 and C-TCR 1.6 ± 0.2 mm/day, respectively; P ≤ 0.05). Despite the similarities in CL size, the average P4 concentration was higher in the A-TCR (9.6 ± 1.4 ng/mL) than in the A-control (4.0 ± 1.0 ng/mL) and C-TCR (4.4 ± 1.0 ng/mL) groups (P < 0.05). From these results, we conclude that eCG treatment and TCR improved the fertility of anestrous cows by providing follicular growth rates and size of dominant follicles similar to cyclic cows. Additionally, TCR increases the plasma concentrations of P4 in anestrous cows

Use of different commercial Artemia sp. Enrichements in Octopus Vulgaris, paralarval rearing at initial planctonic phase: effects on growth, survival and fatty acid composition of the paralarvae

[EN] Octopus "paralarvae", are planktonic, swim actively and have high metabolic rates, requiring large quantities of live prey of adequate motility and nutritional quality ( Iglesias et al., 2000; Navarro and Villanueva, 2000, 2003). During the planktonic phase, they undergo strong morphological changes, after which the octopuses start settling to the bottom. The potential of Octopus vulgaris as candiadate for diversification of marine aquacultures are mainly due to its high food conversion rate and fast growth.( Iglesias et al 2006). Despite the research effort taken until now, paralarval rearing of O. vulgaris still suffers high mortalities which limited the industrial culture of this species. The main problems in the paralarval rearing stages are the high mortality rates and poor growth. These are attributed to the lack of standardized culture techniques and nutritional deficiencies in the diet of paralarvae, especially in n-3 highly unsaturated fatty acids (n-3 HUFA). The objective if this experience was to test different commercial live prey enrichment to improve nutritional quality of the artemia.

Skeletal muscle myofibrillar and sarcoplasmic protein synthesis rates are affected differently by altitude-induced hypoxia in native lowlanders

[EN] As a consequence to hypobaric hypoxic exposure skeletal muscle atrophy is often reported. The underlying mechanism has been suggested to involve a decrease in protein synthesis in order to conserve O(2). With the aim to challenge this hypothesis, we applied a primed, constant infusion of 1-(13)C-leucine in nine healthy male subjects at sea level and subsequently at high-altitude (4559 m) after 7-9 days of acclimatization. Physical activity levels and food and energy intake were controlled prior to the two experimental conditions with the aim to standardize these confounding factors. Blood samples and expired breath samples were collected hourly during the 4 hour trial and vastus lateralis muscle biopsies obtained at 1 and 4 hours after tracer priming in the overnight fasted state. Myofibrillar protein synthesis rate was doubled; 0.041+/-0.018 at sea-level to 0.080+/-0.018%hr(-1) (p<0.05) when acclimatized to high altitude. The sarcoplasmic protein synthesis rate was in contrast unaffected by altitude exposure; 0.052+/-0.019 at sea-level to 0.059+/-0.010%hr(-1) (p>0.05). Trends to increments in whole body protein kinetics were seen: Degradation rate elevated from 2.51+/-0.21 at sea level to 2.73+/-0.13 micromolkg(-1)min(-1) (p = 0.05) at high altitude and synthesis rate similar; 2.24+/-0.20 at sea level and 2.43+/-0.13 micromolkg(-1)min(-1) (p>0.05) at altitude. We conclude that whole body amino acid flux is increased due to an elevated protein turnover rate. Resting skeletal muscle myocontractile protein synthesis rate was concomitantly elevated by high-altitude induced hypoxia, whereas the sarcoplasmic protein synthesis rate was unaffected by hypoxia. These changed responses may lead to divergent adaptation over the course of prolonged exposure.

Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

Nuovi catalizzatori per l'idrogenazione, l'idrogenolisi/ring-opening di composti aromatici policiclici

The removal of aromatic hydrocarbons from diesel has received considerable attention after environmental regulations that require petroleum refiners to raise cetane number and to limit aromatics in diesel fuel in order to improve combustion efficiency and reduce particulate and NOx emissions. An alternative is blending with Fischer–Tropsch (FT) gas-to-liquid diesel fuel; however, this option may not be economically viable solution in case of extensive blend. Another alternative is to incorporate in the diesel pool a greater fraction of the so-called light cycle oil (LCO). Due to its high aromatics content and its low cetane number (typically between 20 and 30), the incorporation of LCO may have a negative impact on the quality of diesel. Current technologies for LCO improvement are based on hydrogenation to adjust both sulphur and cetane number but while an important fraction of the aromatics present in LCO can be saturated in a deep hydrogenation process, the cetane number may still be lower than the target values specified in diesel legislations, so further upgrading is needed. An interesting technology for improving the cetane number of diesels and maintaining meanwhile high diesel yields is achieved by combining a complete hydrogenation process with a selective ring opening (SRO) reaction of the naphthenic rings. The SRO can be defined as naphthene ring-opening to form compounds with high cetane number, but without any carbon losses. Controlling the interconversion of six- and five- membered rings via an acid-catalyzed ring-contraction step is also of great importance, since selective conversion of six-membered to five-membered naphthene rings greatly influences ring-opening rates and selectivity. High intrinsic activity may be enhanced by deposition of noble metals on acidic, high surface area supports, because it is possible to arrange close proximity of the metal and acid sites. Moreover, in large-pore supports, the diffusion resistance of liquid reactants into the pores is minimized. In addition to metal centres, the acid sites of support also plays role in aromatics hydrogenation. However, the functions of different kinds of acid sites (Brønsted vs. Lewis acidity), and their optimal concentrations and strengths, remain unclear. In the present study we investigated the upgrading of an aromatic-rich feedstock over different type of metal supported on mesoporous silica-alumina. The selective hydrogenolysis and ring opening of tetrahydronaphthalene (THN or tetralin) was carried out as representative of LCO fractions after deep hydrogenation process. In this regards the aim of this study is to evaluate both the effect of metals and that of the supports characterized by different acid distribution and strength, on conversion and selectivity. For this purpose a series of catalysts were prepared by impregnation. The catalysts were characterized and conversion tests of THN were performed in a lab-scale plant operating in the pressure range from 7.0-5.0 MPa and in the temperature range from 300 to 360°C.

Biomass Gasification - Process analysis and dimensioning aspects for downdraft units and gas cleaning lines

In such territories where food production is mostly scattered in several small / medium size or even domestic farms, a lot of heterogeneous residues are produced yearly, since farmers usually carry out different activities in their properties. The amount and composition of farm residues, therefore, widely change during year, according to the single production process periodically achieved. Coupling high efficiency micro-cogeneration energy units with easy handling biomass conversion equipments, suitable to treat different materials, would provide many important advantages to the farmers and to the community as well, so that the increase in feedstock flexibility of gasification units is nowadays seen as a further paramount step towards their wide spreading in rural areas and as a real necessity for their utilization at small scale. Two main research topics were thought to be of main concern at this purpose, and they were therefore discussed in this work: the investigation of fuels properties impact on gasification process development and the technical feasibility of small scale gasification units integration with cogeneration systems. According to these two main aspects, the present work was thus divided in two main parts. The first one is focused on the biomass gasification process, that was investigated in its theoretical aspects and then analytically modelled in order to simulate thermo-chemical conversion of different biomass fuels, such as wood (park waste wood and softwood), wheat straw, sewage sludge and refuse derived fuels. The main idea is to correlate the results of reactor design procedures with the physical properties of biomasses and the corresponding working conditions of gasifiers (temperature profile, above all), in order to point out the main differences which prevent the use of the same conversion unit for different materials. At this scope, a gasification kinetic free model was initially developed in Excel sheets, considering different values of air to biomass ratio and the downdraft gasification technology as particular examined application. The differences in syngas production and working conditions (process temperatures, above all) among the considered fuels were tried to be connected to some biomass properties, such elementary composition, ash and water contents. The novelty of this analytical approach was the use of kinetic constants ratio in order to determine oxygen distribution among the different oxidation reactions (regarding volatile matter only) while equilibrium of water gas shift reaction was considered in gasification zone, by which the energy and mass balances involved in the process algorithm were linked together, as well. Moreover, the main advantage of this analytical tool is the easiness by which the input data corresponding to the particular biomass materials can be inserted into the model, so that a rapid evaluation on their own thermo-chemical conversion properties is possible to be obtained, mainly based on their chemical composition A good conformity of the model results with the other literature and experimental data was detected for almost all the considered materials (except for refuse derived fuels, because of their unfitting chemical composition with the model assumptions). Successively, a dimensioning procedure for open core downdraft gasifiers was set up, by the analysis on the fundamental thermo-physical and thermo-chemical mechanisms which are supposed to regulate the main solid conversion steps involved in the gasification process. Gasification units were schematically subdivided in four reaction zones, respectively corresponding to biomass heating, solids drying, pyrolysis and char gasification processes, and the time required for the full development of each of these steps was correlated to the kinetics rates (for pyrolysis and char gasification processes only) and to the heat and mass transfer phenomena from gas to solid phase. On the basis of this analysis and according to the kinetic free model results and biomass physical properties (particles size, above all) it was achieved that for all the considered materials char gasification step is kinetically limited and therefore temperature is the main working parameter controlling this step. Solids drying is mainly regulated by heat transfer from bulk gas to the inner layers of particles and the corresponding time especially depends on particle size. Biomass heating is almost totally achieved by the radiative heat transfer from the hot walls of reactor to the bed of material. For pyrolysis, instead, working temperature, particles size and the same nature of biomass (through its own pyrolysis heat) have all comparable weights on the process development, so that the corresponding time can be differently depending on one of these factors according to the particular fuel is gasified and the particular conditions are established inside the gasifier. The same analysis also led to the estimation of reaction zone volumes for each biomass fuel, so as a comparison among the dimensions of the differently fed gasification units was finally accomplished. Each biomass material showed a different volumes distribution, so that any dimensioned gasification unit does not seem to be suitable for more than one biomass species. Nevertheless, since reactors diameters were found out quite similar for all the examined materials, it could be envisaged to design a single units for all of them by adopting the largest diameter and by combining together the maximum heights of each reaction zone, as they were calculated for the different biomasses. A total height of gasifier as around 2400mm would be obtained in this case. Besides, by arranging air injecting nozzles at different levels along the reactor, gasification zone could be properly set up according to the particular material is in turn gasified. Finally, since gasification and pyrolysis times were found to considerably change according to even short temperature variations, it could be also envisaged to regulate air feeding rate for each gasified material (which process temperatures depend on), so as the available reactor volumes would be suitable for the complete development of solid conversion in each case, without even changing fluid dynamics behaviour of the unit as well as air/biomass ratio in noticeable measure. The second part of this work dealt with the gas cleaning systems to be adopted downstream the gasifiers in order to run high efficiency CHP units (i.e. internal engines and micro-turbines). Especially in the case multi–fuel gasifiers are assumed to be used, weightier gas cleaning lines need to be envisaged in order to reach the standard gas quality degree required to fuel cogeneration units. Indeed, as the more heterogeneous feed to the gasification unit, several contaminant species can simultaneously be present in the exit gas stream and, as a consequence, suitable gas cleaning systems have to be designed. In this work, an overall study on gas cleaning lines assessment is carried out. Differently from the other research efforts carried out in the same field, the main scope is to define general arrangements for gas cleaning lines suitable to remove several contaminants from the gas stream, independently on the feedstock material and the energy plant size The gas contaminant species taken into account in this analysis were: particulate, tars, sulphur (in H2S form), alkali metals, nitrogen (in NH3 form) and acid gases (in HCl form). For each of these species, alternative cleaning devices were designed according to three different plant sizes, respectively corresponding with 8Nm3/h, 125Nm3/h and 350Nm3/h gas flows. Their performances were examined on the basis of their optimal working conditions (efficiency, temperature and pressure drops, above all) and their own consumption of energy and materials. Successively, the designed units were combined together in different overall gas cleaning line arrangements, paths, by following some technical constraints which were mainly determined from the same performance analysis on the cleaning units and from the presumable synergic effects by contaminants on the right working of some of them (filters clogging, catalysts deactivation, etc.). One of the main issues to be stated in paths design accomplishment was the tars removal from the gas stream, preventing filters plugging and/or line pipes clogging At this scope, a catalytic tars cracking unit was envisaged as the only solution to be adopted, and, therefore, a catalytic material which is able to work at relatively low temperatures was chosen. Nevertheless, a rapid drop in tars cracking efficiency was also estimated for this same material, so that an high frequency of catalysts regeneration and a consequent relevant air consumption for this operation were calculated in all of the cases. Other difficulties had to be overcome in the abatement of alkali metals, which condense at temperatures lower than tars, but they also need to be removed in the first sections of gas cleaning line in order to avoid corrosion of materials. In this case a dry scrubber technology was envisaged, by using the same fine particles filter units and by choosing for them corrosion resistant materials, like ceramic ones. Besides these two solutions which seem to be unavoidable in gas cleaning line design, high temperature gas cleaning lines were not possible to be achieved for the two larger plant sizes, as well. Indeed, as the use of temperature control devices was precluded in the adopted design procedure, ammonia partial oxidation units (as the only considered methods for the abatement of ammonia at high temperature) were not suitable for the large scale units, because of the high increase of reactors temperature by the exothermic reactions involved in the process. In spite of these limitations, yet, overall arrangements for each considered plant size were finally designed, so that the possibility to clean the gas up to the required standard degree was technically demonstrated, even in the case several contaminants are simultaneously present in the gas stream. Moreover, all the possible paths defined for the different plant sizes were compared each others on the basis of some defined operational parameters, among which total pressure drops, total energy losses, number of units and secondary materials consumption. On the basis of this analysis, dry gas cleaning methods proved preferable to the ones including water scrubber technology in al of the cases, especially because of the high water consumption provided by water scrubber units in ammonia adsorption process. This result is yet connected to the possibility to use activated carbon units for ammonia removal and Nahcolite adsorber for chloride acid. The very high efficiency of this latter material is also remarkable. Finally, as an estimation of the overall energy loss pertaining the gas cleaning process, the total enthalpy losses estimated for the three plant sizes were compared with the respective gas streams energy contents, these latter obtained on the basis of low heating value of gas only. This overall study on gas cleaning systems is thus proposed as an analytical tool by which different gas cleaning line configurations can be evaluated, according to the particular practical application they are adopted for and the size of cogeneration unit they are connected to.