Synergetic depolymerization of aspen CEL by pyranose 2-oxidase and lignin-degrading peroxidases

Abstract

Three enzymatic treatments were compared for the depolymerization of cellulolytic enzyme lignin (CEL) from aspen; these systems used pyranose 2-oxidase and lignin-degrading peroxidases. The "P" system was mainly composed of pyranose 2-oxidase, lignin peroxidase (LiP), and manganese peroxidase (MnP). Catalase and vitamin C were added to the P system to decompose H2O2 to control the H2O2 concentration. The system to which catalase was added was called the "C" system. The system to which catalase and vitamin C were added together was called the "V" system. Ultraviolet-visible (UV-Vis) spectra of supernatants after aspen CEL treatment by the P, C, or V system was used to monitor the amount of water-soluble lignin fragments that were generated, which increased with system treatment time. A gel permeation chromatography (GPC) analysis showed that after 12 h of system treatment, the molecular weight (Mw) of CEL was efficiently lowered; the maximum Mw reduction of aspen CEL was 20% when compared to the blank and control runs. The residual enzymatic activity of the supernatant after the CEL treatment by the P, C, or V system indicated that MnP and LiP activity for lignin degradation was dependent upon the H2O2 concentration. Therefore, it is advised that MnP and LiP be applied separately for effective lignin degradation.