The use of a wide range of water miscible and immiscible ionic liquids (ILs) as reaction media for ABTS (2,2′-azino-bis(3ethylbenzothiazoline-6-sulfonic acid) diammonium salt) oxidation by Trametes versicolor laccase was studied. Thirteen ILs were shown to be suitable media for the laccase oxidation reaction, increasing the activity with respect to conventional media. Among them, the water-miscible IL choline dihydrogen phosphate [Chol][H 2 PO 4 ] allowed over-laccase activity with an enhancement rate of 451% at 25°C and pH 7.0. This ionic liquid improved the stability of the enzyme in the face of high temperature and high pH, while storage at room 10 temperature in aqueous medium was increased up to 4.5 times. Moreover, it was found that its use in the reaction medium for decolourizing dyes (antraquinonic and azoic) using laccase increased the decolourization rate by up to 216% and 137% for the azoic dyes Acid Black 1 and Remazol Brillant Blue R, respectively. A high decolorization rate was also obtained for a mix of dyes (80% within 8 h). To understand the effect of [Chol][H 2 PO 4 ] on the secondary protein structure of the laccase, several spectroscopic techniques were used 15 such as Circular Dichroism (CD), Fourier transform infrared (FT-IR) and Fluorescence, all of which demonstrated that the β sheets structure was affected. A shift to α-helix structure [Chol][H 2 PO 4 ] could be responsible of the enhancement of the enzyme activity observed at 300 mM 55properties of ILs, including their hydrophobicity, density, viscosity, melting point, polarity and solvent miscibility, can be finely tuned by selecting appropriate combinations of cations and anions, while an optimal IL can be designed for each specific enzymatic reaction system. Interest in these compounds, often 60 heralded as the green, high-tech media of the future, is still increasing rapidly, not only in biocatalysis but also in chemical catalysis, separation technology and analytical applications 13, 14 . Recently, the use of ILs with laccases has also been described as an efficient non-conventional catalyst system in applications such 65 as wood treatment and phenol degradation 3, 5 . On the other hand,Textile manufacturing involves the discharge of highly colored synthetic dye effluents which are aesthetically displeasing and can damage the receiving water body by impeding the penetration of light 15 . The strict environmental 70 legislation of European countries does not permit their release since they can have very severe consequences on river courses, including reducing photosynthetic activity and dissolved oxygen concentrations 16 . The great importance of effluent treatment has been underlined in many research-works 17 . In the textile 75 industry, a wide variety of dyes colors have been extensively used for textile industry, anthraquinonic and azoic dyes could be

Laccase activity was detected in a soil bacterium Stenotrophomonas maltophilia AAP56 identified by biochemical and molecular methods. It was produced in cells at the stationary growth phase in Luria Bertani (LB) medium added by 0.4 mM copper sulfate. The addition of CuSO(4) in culture medium improved production of laccase activity. However, one laccase enzyme was detected by native polyacrylamide gel electrophoresis. The enzyme showed syringaldazine (K (m) = 53 microM), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (K (m) = 700 microM), and pyrocatechol (K (m) = 25 microM) oxidase activity and was activated by addition of 0.1% (v/v) Triton-X-100 in the reaction mixture. Moreover, the laccase activity was increased 2.6-fold by the addition of 10 mM copper sulfate; the enzyme was totally inhibited by ethylenediaminetetraacetic acid (5 mM), suggesting that this laccase is a metal-dependant one. Decolorization activity of some synthetic dyes (methylene blue, methyl green, toluidine blue, Congo red, methyl orange, and pink) and the industrial effluent (SITEX Black) was achieved by the bacteria S. maltophilia AAP56 in the LB growth medium under shaking conditions.