Purification and biochemical characterization of a new alkali-stable laccase from Trametes sp. isolated in Tunisia: role of the enzyme in olive mill waste water treatment.

A white-rot basidiomycete, isolated from decayed acacia wood (from Northwest of Tunisia) and identified as Trametes sp, was selected in a broad plate screening because of its ability to decolorize and dephenolize olive oil mill wastewater (OMW) efficiently. The major laccase was purified and characterized as a monomeric protein with apparent molecular mass of 61 kDa (SDS-PAGE). It exhibits high enzyme activity over broad pH and temperature ranges with optimum activity at pH 4.0 and a temperature of 60 °C. The purified laccase is stable at alkaline pH values. The enzyme retained 50 % of its activity after 90 min of incubation at 55 °C. Using ABTS, this laccase presented K and V values of 0.05 mM and 212.73 μmoL min mg, respectively. It has shown a degrading activity towards a variety of phenolic compounds. The purified laccase was partially inhibited by Fe, Zn, Cd and Mn, while Cu acted as inducer. EDTA (10 mM) and NaN (10 mM) were found to completely inhibit its activity. 73 % OMW was dephenolized after 315 min incubation at 30 °C with 2 U mL of laccase and 2 mM HBT. [ABSTRACT FROM AUTHOR]