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Ayed L.,University of Monastir | Achour S.,Diagnostic Immunitaire Et Valorisation A Linstitut Superieur Of Biotechnologie | Khelifi E.,Center Urbain Nord | Cheref A.,Center de Biotechnologie de la Technopole de Borj-Cedria | Bakhrouf A.,University of Monastir
Chemical Engineering Journal | Year: 2010

Azo dyes are widely used in textile dyeing which contains toxic and carcinogens compounds. So they must be treated before their discharge into the receptor medium. In this aim, this work is focused on the aerobic decolorization of water soluble azo dye Congo Red (CR) by bacterial consortium (Sphingomonas paucimobilis, Bacillus sp. and Staphylococcus epidermidis). The effect of different combinations of these three strains cultivated in the pure culture in mineral salts medium (MSM) on the decolorization of Congo Red (cell density fixed at OD600=1 with the addition of 750ppm of the dye) was studied using equilateral triangle diagram and mixture experimental design to assess color and COD removal during species growth. Using software analysis (Minitab 14.0), the formulation of pure culture in MSM can be optimized for several responses and the best formulation can be obtained. The results suggested that the highest decolorization and chemical oxygen demand (COD) rates were 100% and 98%, respectively. Very high regression coefficient between the variables and the responses: decolorization and COD removal were R 2=32.69% and R 2=52.25%, respectively indicating an excellent evaluation of experimental data by polynomial regression model. FTIR (Fourier transform infrared) and UV-vis analysis confirmed the biodegradation of Congo Red by the bacterial consortium. The produced metabolites were extracted and their phytotoxicity study suggested their low toxicity. © 2010 Elsevier B.V.

Ayed L.,University of Monastir | Khelifi E.,Center Urbain Nord | Jannet H.B.,University of Monastir | Miladi H.,University of Monastir | And 3 more authors.
Chemical Engineering Journal | Year: 2010

The use of chemometric methods such as response surface methodology (RSM) based on statistical design of experiments (DOEs) is becoming increasingly widespread in several sciences such as analytical chemistry, engineering and environmental chemistry. In the present study, the decolorization and the degradation efficiency of Methyl Orange (MO) was studied using a microbial consortium. The microbial growth of Sphingomonas paucimobilis, Bacillus cereus ATCC14579, Bacillus cereus ATCC11778 is well in the presence of MO (750. ppm) within 48. h at pH 7 and 30 °C. In fact, these microorganisms were able to decolorize and to degrade MO to 92%. The degradation pathway and the metabolic products formed during the degradation were also predicted using UV-vis, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy analysis. Under optimal conditions, the bacterial consortium was able to decolorize completely (>84%) the dye within 48. h. The color and COD removal were 84.83% and 92.22%, respectively. A significant increase in azoreductase, lignin peroxidase and laccase activities in the cells were obtained after complete decolorization. Phytotoxicity study using plants showed no toxicity of the produced products. © 2010 Elsevier B.V.

Hadda H.,Center Urbain Nord | Hajji M.K.,National Engineering School of Tunis | Dridi N.,National Engineering School of Tunis
RAIRO - Operations Research | Year: 2015

In this paper we develop new elimination rules and discuss several polynomially solvable cases for the two-stage hybrid flow shop problem with dedicated machines. We also propose a worst case analysis for several heuristics. Furthermore, we point out and correct several errors in the paper of Yang [J. Yang, A two-stage hybrid flow shop with dedicated machines at the first stage. Comput. Oper. Res. 40 (2013) 2836-2843]. © EDP Sciences, ROADEF, SMAI 2015.

Hadda H.,Center Urbain Nord
International Journal of Production Economics | Year: 2015

In Allaoui H., Lamouri S., Artiba A., Aghezzaf E., Simultaneously scheduling n jobs and the preventive maintenance on the two-machine flow shop to minimize the makespan. International Journal of Production Economics 2008, 112, 161-167, several results are proposed. We show in this note that some of them are false. We also extend the analysis for some other results. © 2014 Elsevier B.V. All rights reserved.

In this paper we deal with the two-machine flow shop scheduling problem with several availability constraints on the first machine, under the resumable scenario. We first develop an improved algorithm with a relative worst-case error bound of 4/3. We then present a polynomially solvable case. © 2010 Springer-Verlag.

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