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Chaari A.,University of Versailles | Horchani H.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Frikha F.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Verger R.,Aix - Marseille University | And 2 more authors.
International Journal of Biological Macromolecules

Due to the involvement of α-Synuclein (α-Syn) in lipid transport and its role in the normal function and in the pathology of Parkinson disease, it is important to study first the surface properties of the protein at the air/water interface and second its behavior related to biological membranes. For this purpose, the monomolecular film technique was used as membrane model to compare the interactions with various phospholipids of monomeric and fibrillar forms of α-Syn. We have determined the equilibrium surface pressure of the two forms of α-Syn (monomeric and fibrillar form) at the air/water interface. The surface pressures reached by monomeric α-Syn were shown to be higher than the ones of fibrillar α-Syn and similar to the value obtained by mellitin, a lytic peptide of bee venom, which has been described as "protein detergent". The monomeric α-Syn adsorbed more rapidly at the air/water interface with a maximal adsorption rate at least 60-times higher than the fibrillar form. In the presence of a phospholipid monolayer, the surface activities of two α-Syn forms are much greater than observed at the air/water interface. Also we can show that the fibrillar form of α-Syn have a higher value of critical pressure than the monomeric one for the cow brain extract and the Phospatidyl Glycerol (an anionic phospholipid) which confirm its higher affinity for the anionic phospholipid than the monomeric form. According these results, we can suggest that this aggregate form have important implications for the pathological activity and, therefore, for the associated neurotoxicity which can results in layer disruption and cell leakage. © 2013. Source

Kharrat N.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Ali Y.B.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Marzouk S.,Laboratoire Of Chimie Industrielle Ii | Gargouri Y.-T.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Karra-Chaabouni M.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases
Process Biochemistry

Rhizopus oryzae lipase (ROL) was immobilized by physical adsorption onto silica aerogels. The functional properties of immobilized lipase were determined and compared to the soluble lipase ones. The optimum temperature for both free and immobilized lipase activities was 37 °C. We found that the immobilization of R. oryzae lipase onto silica aerogels increased remarkably its stability at high temperatures and within a wade pH range. Besides the immobilized enzyme exhibited a high tolerance to apolar solvent and retained its fully activity in suspension after 4 months of storage at 4 °C. This immobilized biocatalyst is applied in n-butyl oleate synthesis by esterification of oleic acid with n-butanol, using hexane as an organic solvent. The best conversion yield of the ester butyl oleate was obtained with the immobilized lipase (80% versus 35% with the free lipase). This catalytic esterification has been carried on the presence of hexane at 37 °C with oleic acid to butanol molar ratio of 1:1 and 450 IU of immobilized lipase. Furthermore, the reuse of the lipase immobilized by adsorption allowed us to observe that its can achieved 12 successive cycles, without a significant loss of its catalytic activity. Such results revealed good potential for recycling under non-aqueous system. © 2011 Elsevier Ltd. All rights reserved. Source

Aissa I.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Sellami M.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Kamoun A.,Laboratoire Of Chimie Industrielle Ii | Gargouri Y.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Miled N.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases
Current Chemical Biology

Wax esters have a variety of biotechnological usage in cosmetic and pharmaceutical products. Synthesized wax esters can be an alternative to sperm whale being rare. The ability of a non-commercial immobilized lipase from Rhizopus oryzae to catalyze the synthesis of wax esters was investigated in organic media. Wax esters were obtained by esterification of myristic, palmitic, stearic or oleic acids with cetyl alcohol. Response surface methodology was used to evaluate the effects of the temperature, the enzyme amount and the volume of hexane on the wax esters production yields. Under optimal conditions, high conversion yields (92-95%) of saturated fatty acids were reached within a reaction time of 30 min whereas a yield of 93.5% was obtained for cetyl oleate after 60 min. The synthesized esters were purified using a silica gel column. The immobilized Rhizopus oryzae lipase was successfully reused in 20 repeated cycles with no significant decrease in the final conversion yields. This makes it a promising candidate for the development of a highly effective set-up for the production of wax esters. © 2012 Bentham Science Publishers. Source

Aloui F.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Maazoun B.,The Factory Confiserie TRIKI Le Moulin | Gargouri Y.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Miled N.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases
Journal of Food Science and Technology

Oil bleeding during storage oleaginous seeds based confectionery products is a major problem affecting acceptance by consumers. Halva is a popular sweet food prepared from a sesame paste and a sugar mixture. The objective of this work was to improve the oil retention in this product by incorporating commercial fibers and emulsifiers: soya lecithin and monoglycerides (MG1 or MG2) during manufacturing. Oil retention yield was optimized on small batches, by response surface methodology using a central composite design applied with two factors, emulsifier concentration (0.25–2.25 %) and fibers concentration (0–2 %) at three levels. A centrifugation test was optimized to assess oil retention in halva samples. The experimental response (oil retention) was fitted with quadratic equations for each emulsifier, using multiple regression analysis. The emulsion stability increased with increasing the emulsifier concentration, particularly to 2.25 %. The oil bleeding assessed at 45 °C was slow but yielded similar results to those estimated by centrifugation test. The latter seems an attractive rapid method to quantify oil retention in oleaginous seeds and crops based food matrices. At an industrial scale, the increase of MG1 concentration to 2.25 % in halva enhances the oil retention of the product but does not affect its color or textural characteristics. Microscopic observations allowed us to explain high oil retention in this product by a homogeneous dispersion of oil droplets in the aqueous phase. © 2015 Association of Food Scientists & Technologists (India) Source

Smichi N.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Fendri A.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Chaabouni R.,Laboratoire Of Biochimie Et Of Genie Enzymatique Des Lipases | Rebah F.B.,Institute National Des Science Et Technologies Of La Mer | And 2 more authors.
Applied Biochemistry and Biotechnology

A lipolytic activity was located in the sardine digestive glands (pyloric caeca), from which a sardine digestive lipase (SaDL) was purified. Pure SaDL has a molecular mass of 43 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The enzyme was found to be more active on short-chain triacylglycerols than on long-chain ones. SaDL does not present the interfacial activation phenomenon. Control experiments were performed under the same experimental conditions, with dromedary and turkey pancreatic lipases and showed a positive interfacial activation phenomenon. Sodium deoxycholate (NaDC) has an inhibitory effect on the lipase activity. The pure enzyme lost 40% of its activity in presence of 8 mM NaDC. SaDL was found to be mostly stable at low pH values. Interestingly, no colipase was detected in the sardine pyloric caeca. Analogous results were reported for the scorpion and the crab digestive systems. This is in line with the idea that colipase might has evolved in mammal animals simultaneously with the appearance of an exocrine pancreas. No similarity was found between the NH2-terminal amino acid residues of SaDL and those of lipases from the digestive tract of other species. Altogether, these results suggest that SaDL is a member of a new group of lipases belonging to aquatic species. © 2010 Springer Science+Business Media, LLC. Source

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