Oxydation de composés phénoliques par les laccases de Trametes sp. et Myceliophthora thermophila en milieu hydro organique biphasique : application à la préparation des colonnes

Abstract : The oxidation of some phenolic compounds by laccase from Myceliophtho1"a thermophila and Trametes sp. was studied in aqueous and hydro organic biphasic medium (ethyl acetate and phosphate buffer). ln aqueous medium and at the same pH, the two laccases give identical products. They have the same substrate specificity but they show high affinity to phenolic compounds bearing methoxyl groups in particularly ferulic and sinapic acid. ln hydro organic biphasic medium, the rate of oxidation reaction that takes place in the aqueous phase decreases steeply. Although at neutral pH the majority of phenolic substrates are soluble in the organic phase, the decrease of enzymatic activity is independent of the diffusionallimitation. The hydro organic biphasic medium doesn't modify the specificity of laccases but the intermediate products, which polymerize quickiy in aqueous medium, are prevented from doing so in biphasic medium due to their transfer into the organic solvent. Theretore, their stability is enhanced in this medium. The oxidation of ferulic acid by laccase from Myceliophthora thermophila in a biphasic hydro-organic system resulted in stable yellow intermediate products only soluble in the organic phase of this system. We identified one of theses colored products as the decarboxyled 8-8 '-y-dehydro-lactone diferulate. The oxidation of sinapic acid causes the appearance of a red color in the two phases of the biphasic medium. The oxidation of phenolic compounds by the laccase in a biphasic hydro-organic medium illustrates an interesting potential significandy enhanced for preparation and separation of new colored products.
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Theses
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http://docnum.univ-lorraine.fr/prive/INPL_T_2005_MUSTAFA_R.pdf
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Submitted on : Thursday, March 29, 2018 - 12:35:37 PM
Last modification on : Monday, April 16, 2018 - 10:41:22 AM

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Rana Mustafa. Oxydation de composés phénoliques par les laccases de Trametes sp. et Myceliophthora thermophila en milieu hydro organique biphasique : application à la préparation des colonnes. Alimentation et Nutrition. Institut National Polytechnique de Lorraine, 2005. Français. ⟨NNT : 2005INPL049N⟩. ⟨tel-01749999⟩

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