Investigations on tyrosinase activity in melanin-free ink from Sepia officinalis: potential for food proteins cross-linking

Protein modification via enzymatic cross-linking is an attractive way for altering food structure so as to create products with increased quality and nutritional value. In this study, enzymatic cross-linking of β-casein was performed by tyrosinase activity, from melanin-free ink from Sepia officinalis, which was monitored by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) techniques. The melanin-free ink contains a strong tyrosinase activity with pH 7 and 58?°C as optima of pH and temperature, respectively. Such activity is stimulated by ferrous ions and strongly inhibited by Mn²⁺, EDTA, H₂O₂, arbutin, and p-coumaric acid. We also show that 2 Mercapto-ethanol (14?mM) quickly and completely inactivated sepia tyrosinase. The melanin-free ink exhibits a major protein on SDS–PAGE with an N-terminal sequence matching perfectly with an internal sequence of the sepia peroxidase. The zymogram confirmed the inactive state of this truncated protein and the presence of an active tyrosinase enzyme. Interestingly, this activity was able to cross-link the β-casein protein. The tyrosinase implication in reticulation was demonstrated by the addition of its inhibitors, with 2-mercaptoethanol being the most effective, followed by arbutin, p-coumaric acid, and hydrogen peroxide.     

A branch and bound enhanced genetic algorithm for scheduling a flowline manufacturing cell with sequence dependent family setup times

This paper addresses the permutation flowline manufacturing cell with sequence dependent family setup times problem with the objective to minimize the makespan criterion. We develop a cooperative approach including a genetic algorithm and a branch and bound procedure. The latter is probabilistically integrated in the genetic algorithm in order to enhance the current solution. Moreover, the application of the branch and bound algorithm is based upon the decomposition of the problem into subproblems. The performance of the proposed method is tested by numerical experiments on a large number of representative problems.     

Widgets Dedicated to User Interface Evaluation

In this article, evaluation-based widgets are proposed as a contribution to assist evaluators for early evaluation of user interfaces. This contribution imbricates the ergonomic quality evaluation process into widgets used for user-interface graphical composition. In other words, these widgets evaluate themselves according to a defined set of ergonomic guidelines. The proposed widgets indicate the possible interface design ergonomic inconsistencies as a notification to the designer. The guidelines set can be modified through an interface dedicated to guidelines definition into XML files. The proposed widgets are intended for the evaluation of different kind of user interfaces: WIMP, web, and mobile. An experimental evaluation, involving these evaluation-based widgets, is proposed to illustrate and to validate the approach.     

Hierarchical production planning with flexibility in agroalimentary environment: a case study

In this paper we address to the planning problem in the agroalimentary domain. In such industry, several specific constraints should be taken into account for planning task such as the constraints of interdependencies between the products and variable production modes. Furthermore, we present the relationship between two large fields as the production hierarchical planning and the flexibility. Especially, we show that the flexibility planning should be made a priori and then integrated in the hierarchical planning process. Indeed, we have established a mathematical model according to different production levels. While taking into account real capacities of the shop and the interdependencies between the products, the results of our formulation are satisfactory in terms of quality of solution and time requirements. It??s shown that our model is able to reach all optimal solutions for all treated models and for all system levels.     

Purification and Biochemical Characterization of Lipase from Tunisian Euphorbia peplus Latex

Lipases from vegetable sources have been the focus of intense and growing research. The use of enzymes from plants has the advantage of employing industrial waste products. The lipase activity of Euphorbia peplus L. (Euphorbiaceae) was investigated for the first time. The Euphorbia peplus latex lipase (EpLL) was purified after ammonium sulfate fractionation and anion exchange chromatography on a DEAE-Cellulose column leading to 12.57-fold purification. The EpLL displayed a probable molecular weight of about 40 kDa. The lipase activity was optimum at a temperature of 40 °C and pH 8, the specific activities of EpLL were found to be 249 ± 12.45 and 161.4 ± 8.07 U/mg when tributyrin (TC₄) and olive oil were used as substrate respectively. The enzyme retained 80 % of its activity when incubated for 1 h at 50 °C. The EpLL was strongly destabilised by divalent metal ions (Fe²⁺, Mg²⁺, Zn²⁺ and Cu²⁺). Lipase was slightly stimulated by Triton X-100 and Tween-80, while strongly inhibited by sodium dodecyl sulfate. A good stability of the enzyme in the presence of organic solvents was reveled suggesting its industrial utility.     

Modification of cellulose fibers with functionalized silanes: Effect of the fiber treatment on the mechanical performances of cellulose–thermoset composites

Unsaturated polyester and epoxy resin matrices were filled with silane‐treated cellulose fibers and the ensuing composites were tested in terms of mechanical properties before and after accelerated aging consisting of their immersion into water. The coupling agents used were γ‐aminopropyltriethoxysilane (APS), γ‐methacrylopropyltrimethoxysilane (MPS), hexadecytrimethoxysilane, and γ‐mercaptopropyltrimethoxysilane (MRPS) and those containing reactive functions capable of reacting at one end with the fibers and at the other with the matrix, namely, APS, MPS, and MRPS, were more efficient in improving the mechanical properties of the composites. The immersion into water induced a drastic loss of mechanical properties of the materials. The water uptake of the composites was also studied and showed that the silane treatment was poorly efficient in preventing cellulose from water absorption. The fracture surfaces were inspected by scanning electron microscopy, which confirmed the quality of the interface. These observations were in agreement with the results obtained from the dynamic mechanical characterization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 974–984, 2005     

Nonlinear dynamic of the renewable energy cycle transition in Tunisia: Evidence from smooth transition autoregressive models

In this paper, we focus on the problem of the energy transition in Tunisia were we suggest to study and modeling the nonlinear dynamic of the endogenous renewable energy cycle.As today the socioeconomic development in Tunisia is too complicated and dependent on the adopted energetic strategy. Our contribution consists on recognizing exactly the main bases of this correlative development.In this context, we try to provide some theoretical and empirical studies for renewable energy politics especially under the chaotic transition in the post revolution period in Tunisia.All this work will be based on the application of the univariate STAR (smooth transition autoregressive) method composed by two transition process types the logistic STAR model (LSTAR) and the exponential STAR model (ESTAR). As results we found that the LSTAR process is more adequate for asymmetric data for our case. In this regard, our results indicated that the renewable energy can not only work as a possible factor for energetic strategy transition in Tunisia, but also, is a promising candidate for stability and socioeconomic development.     

Characterization of nanocrystalline Al-based alloy produced by mechanical milling followed by cold-pressing consolidation

In the present study high energy mechanical milling followed by high-pressing consolidation has been used to obtain bulk nanocrystalline aluminum based alloy. Fully dense disks with homogenous microstructure were obtained. X-ray analysis indicates that high strain imposed by mechanical milling and severe plastic deformation (SPD) processing causes microstructure showing a mixture of a significant lower value of the crystallite size (around 60 nm) and the creation of a large number of linear defects which induces microstrains (around 0.7%). In addition, the elevated value of hardness which was obtained for the consolidated disks and the favorable comparison with the value measured for the same as-received alloy confirm the potential of the SPD technique when it is collected with high energy mechanical milling for producing higher performance materials. On the basis of calorimetric measurements, as a function of consolidation stresses, we can say that the thermal behaviour was characterized by a significant heat release and grain growth during the heating cycle. Moreover, the noticed broad endothermic peak can be attributed to some precipitants containing magnesium.     

Effects of static magnetic fields on growth and membrane lipid composition of Salmonella typhimurium wild-type and dam mutant strains

This study was carried out to explore the adaptive mechanisms of S. typhimurium particularly, the implication of the Dam methyltransferase in the remodelling of membrane lipid composition to overcome magnetic field stress. With this aim, we focused our analyses on the increase in viable numbers and membrane lipid modifications of S. typhimurium wild-type and dam mutant cells exposed for 10h to static magnetic fields (SMF; 200 mT). For the wild-type strain, exposure to SMF induced a significant decrease (p<0.05) of CFU at 6h, followed by an increase between 8 and 10h. Growth of the dam mutant was significantly affected (p<0.05) after 6h and no recovery was observed until 10h, highlighting a different behavior of SMF stressed wild-type and dam mutant strains. SMF significantly affected the phospholipid proportions in the two strains. The most affected were those of the acidic phospholipids, cardiolipins (CL). In the dam strain the phospholipid response to SMF followed a globally similar trend as in the wild-type with however lower effects, leading mainly to an unusual accumulation of CL. This would in part explain the different behavior of the wild-type and the dam strain. Results showed a significant increase of membrane cyclic fatty acids Cyc17 and Cyc19 in the wild-type strain but only the Cyc17 in the dam strain and a meaningful increase of the total unsaturated fatty acids (UFAs) to total saturated fatty acids (SFAs) ratios of the exposed cells compared to controls from 3 to 9h (p<0.05) for both strains. The net increase of the total UFAs to total SFAs ratios seemed to result mainly from the increase of (C18:1) proportion (p<0.05) and to a lower extent from that of (C16:1) (p<0.05). These modifications of cyclic and unsaturated fatty acid proportions constitute an adaptive response to SMF stress in S. typhimurium wild-type and dam mutants to maintain an optimum level of membrane fluidity under SMF.     

Hypoelastic,hyperelastic, discrete and semi-discrete approaches for textile composite reinforcement forming

The clear multi-scale structure of composite textile reinforcements leads to develop continuous and discrete approaches for their forming simulations. In this paper two continuous modelling respectively based on a hypoelastic and hyperelastic constitutive model are presented. A discrete approach is also considered in which each yarn is modelled by shell finite elements and where the contact with friction and possible sliding between the yarns are taken into account. Finally the semi-discrete approach is presented in which the shell finite element interpolation involves continuity of the displacement field but where the internal virtual work is obtained as the sum of tension, in-plane shear and bending ones of all the woven unit cells within the element. The advantages and drawbacks of the different approaches are discussed.