Enhancement of activity and selectivity in lipase‐catalyzed transesterification in ionic liquids by the use of additives

BACKGROUND: Seven ionic liquids (ILs) based on 1-alkyl-3-methylimidazolium cation in combination with hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions were tested as reaction media for lipase-catalyzed transesterification in low water conditions. With the aim of improving the activity and/or selectivity of the lipase, various treatments were applied to ionic liquid media such as equilibration with aqueous solutions of salts, NaHCO₃ or Na₂CO₃, or the addition of a catalytic amount of a non-reactive organic base to the reaction mixture, triethylamine. RESULTS: The treated ionic liquids were shown to be excellent media for lipase-catalyzed ester synthesis by transesterification compared with conventional organic solvents, such as n-hexane. All treatments were found to enhance the synthetic activity of the enzyme, the best results being achieved with the addition of triethylamine. The addition of a catalytic amount of this base to the ILs resulted in a significant increase in both the synthetic activity and selectivity values. For instance, the synthetic activity in [emim⁺][TfN₂⁻] was enhanced more than 12 times and the selectivity increased from 86% to 95% when triethylamine was used. CONCLUSION: These treatments could be easy-to-use approaches to improve the efficiency of enzymatic reactions in ionic liquids when the reaction does not proceed smoothly. Copyright © 2007 Society of Chemical Industry     

Highly selective transport of transesterification reaction compounds through supported liquid membranes containing ionic liquids based on the tetrafluoroborate anion

We previously reported the selective simultaneous separation of the substrates and products of a transesterification reaction (vinyl butyrate, 1-butanol, butyl butyrate and butyric acid) through supported liquid membranes (SLMs) based on 1-n-alkyl-3-methylimidazolium cations combined with tetrafluoroborate, hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions. The best results were obtained by the use of tetrafluoroborate based ionic liquids, which led us to further investigate the use of these new supported liquid membranes for the selective separation of different substrates and products of transesterification reactions. With this aim, the permeability of sixteen different organic compounds (vinyl esters, aliphatic esters, alcohols and carboxylic acids) through SLMs containing tetrafluoroborate based ionic liquids ([bmim⁺][BF₄⁻] and [omim⁺][BF₄⁻]) were evaluated. It was found that permeability increased as the alkyl chain length decreased for the same organic functional group. In addition, significant permeability differences were found between the different organic functional groups.As regards the operational stability of these SLMs, they were seen to be very stable when tested over eight continuous cycles of 48 h each.     

Polychlorinated biphenyls and organochlorine pesticides in seafood from the Gulf of Naples (Italy)

Seven target polychlorinated biphenyls (PCBs; IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) and the organochlorine pesticides (OCPs) hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane (DDT) and its related metabolites (p,p'-DDT, p,p'-DDE, and p,p'-DDD) were quantified in edible tissues from seven marine species (European hake, red mullet, blue whiting, Atlantic mackerel, blue and red shrimp, European flying squid, and Mediterranean mussel) from the Gulf of Naples in the southern Tyrrhenian Sea (Italy). PCBs 118, 138, and 153 were the dominant congeners in all the species examined. The concentrations of all PCBs (from not detectable to 15,427 ng g(-1) fat weight) exceeded those of all the DDTs (from not detectable to 1,769 ng g(-1) fat weight) and HCB (not detectable to 150.60 ng g(-1) fat weight) in the samples analyzed. The OCP concentrations were below the maximum residue limits established for fish and aquatic products by the Decreto Ministerale 13 May 2005 in all the samples analyzed; therefore the OCPs in the southern Tyrrhenian Sea species are unlikely to be a significant health hazard. Conversely, the mean concentrations of PCBs exceeded (greatly in some cases) the current limits (200 ng(-1) fat weight) set by the European Union for terrestrial foods. Although the manufacture and use of PCBs are banned or highly restricted, these compounds still are important persistent chemical contaminants in the Gulf of Naples.     

The role of the consumer in the reduction of Listeria monocytogenes in lettuces by washing at home

Lettuce is highly appreciated for its nutritional properties; however microbial contamination through the food chain and its raw consumption may jeopardize these known benefits to the diet. The objective of this study was to determine the role of the consumer at the stage of washing at home, in relation to the probability of illness due to the presence of Listeria monocytogenes in lettuce. Survival curves of L. monocytogenes after washing (dipping with and without addition of bleach, and washing under a running tap) were studied. A mathematical model for each washing method was calculated by fitting experimental data. The obtained models were used to estimate the probability of illness after washing at home. Results show that although consumers can only deal with low loads of L. monocytogenes, their role is essential to reduce the normal contamination level of lettuces and ensure their safety.     

Control system to counteract axial displacement during the welding of huge pipes

Development research has been carried out in order to solve a practical industrial problem: to counteract axial displacement (axial drift or axial creep) of workpieces during the welding process. Solutions found in the literature generally provide adequate results; however, they are mechanically complex with high purchase and maintenance costs. A mechanically simple and inexpensive solution is proposed in this paper. Axial drift is measured with a low-cost custom-built contact displacement sensor. This sensor can measure axial drift without calibration or set-up operations. It is highly robust in order to function correctly in industrial conditions. A pneumatic cylinder moves the idle turning roll along a rail, modifying the longitudinal position of the idle turning roll in order to counteract axial drift. The position of the idle turning roll is controlled by a control algorithm, which consists of a set of rules. Tests were carried out in order to validate the proposed solution, which can be applied to existing turning rolls thereby significantly reducing costs.     

Recovery and distribution of natural antioxidants (α-tocopherol,polyphenols and terpenic acids) after pan-frying of Mediterranean finfish in virgin olive oil

Samples of eight finfish representing the most popular fish species in Greece were pan-fried in virgin olive oil according to the Greek traditional culinary practice. Analyses for polyphenols, hydroxy pentacyclic triterpene acids (HPTA) and α-tocopherol were performed in the fresh and fried oils and fish. Polyphenols and HPTA were determined by GC/MS and α-tocopherol by HPLC. Nine polyphenols were determined in the frying oil samples; six of them were also found in fried fish. The terpenic acids oleanolic, maslinic and ursolic were also determined in frying oils and fried fish. No polyphenols and no HPTA were detectable in raw fish, while α-tocopherol was present in all samples. Besides water loss and oil absorption, pan frying caused the partial loss of all the antioxidants studied in the fried oils, as well as their enrichment in the fried fish. The overall retention of α-tocopherol in the fried oil and fish ranged from 30% to 80%, the respective values for polpyphenols and HPTA ranging between 51–87% and 46–88%. The polarity of the antioxidants studied, seems to affect to some extent their partition between the frying oil and the water-containing fish.     

L'anxiété face aux examens: Dimensionnalité, similitudes et différences chez les étudiants universitaires.

Scores were analyzed from two samples of undergraduate university students in the Toronto area who answered a questionnaire on exam anxiety (the "Test Anxiety Inventory": TAI). The samples (n = 645 and n = 462), which were both made up of women and men, some with English as their mother tongue and others having a mother tongue other than English, showed very comparable result patterns. Women reported a higher exam anxiety level than men on both dimensions of the questionnaire: Worry (TAIW) and Emotionality (TAIE). Students with a mother tongue other than English, an indicator of recent immigration--reported a higher level of anxiety than students whose mother tongue is English, for both the worry component and the emotionality component. Also, and moreover generally, the worry component of TAI (but not the emotionality component) appeared to have a negative correlation with the results obtained by the students in the final exam for the psychology introductory course in which they were registered. This correlation was not attenuated when a general intelligence test was taken into account. Finally, the TAI factorial structure was similar for both samples, with a model using two correlated factors showing better adjustment to the data than a unifactorial model. Given the strong correlation between the two factors, however, (r = 0,80), this hierarchical design of the TAI was supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)