Effect of an electro-Fenton process on the biodegradation of lignin by Trametes versicolor

A synergistic effect was found between the electro-Fenton (E-Fenton) process and a white-rot enzyme (Trametes versicolor) system relative to the degradation of dealkaline lignin. The hydrogen peroxide produced by the E-Fenton process reacted with Fe2+ on the cathode to generate a large number of hydroxyl radicals. These hydroxyl radicals directly degraded various functional groups in lignin, which led to the quick initiation of lignin peroxidase (LiP) and manganese peroxidase (MnP) enzymatic hydrolysis and accelerated the progress of lignin biodegradation. In addition, the hydroxyl radicals produced by the Fenton reaction converted nonphenolic lignin into phenolic lignin, further promoting the ability of manganese peroxidase and laccase to degrade the lignin. Additionally, the Fe3+ secreted by white-rot fungi accelerated the regeneration of Fe2+ on the composite cathode, which sustained the lignin degradation system. In the synergistic system, mycelium growth was significantly improved, with the maximum growth amount reaching 2.3 g and the lignin degradation rate reaching 84.5%, the activity of the three enzymes increased with the increase of currents over 96 h. Among them, the activity of MnP increased significantly to 402 U/L.