Different fungal laccases were used as biocatalysts for the biotransformation of bisphenol A (BPA). The quantitative analysis by gas chromatography-mass spectrometry (GC-MS) showed that BPA is more rapidly oxidized by Coriolopsis gallica laccase among the different fungal laccases tested. Carboxylic acid derivatives such as tartaric acid was found as BPA degradation products resulting from reactions catalyzed by 1 U ml-1 of laccase from C. gallica in the presence of 1mM of the laccasemediator 1-hydroxybenzotriazole (HBT), while -hydroxybutyric acid resulted from oxidative reactions without HBT. BPA was completely removed within 3 h and pyroglutamic acid was found as a supplementary oxidative degradation product from HBT when identified by GC-MS. Laccase played a critical role in BPA biodegradation and catalyzed a cross-coupling reaction.
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 m and V max values of 0.05 mM and 212.73 μmoL min(-1) mg(-1), respectively. It has shown a degrading activity towards a variety of phenolic compounds. The purified laccase was partially inhibited by Fe(2+), Zn(2+), Cd(2+) and Mn(2+), while Cu(2+) acted as inducer. EDTA (10 mM) and NaN3 (10 mM) were found to completely inhibit its activity. 73 % OMW was dephenolized after 315 min incubation at 30 °C with 2 U mL(-1) of laccase and 2 mM HBT.
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