Effect of manganese peroxidase on the decomposition of cellulosic components: Direct cellulolytic activity and synergistic effect with cellulase

•Previously unknown MnP activity on cellulose decomposition was demonstrated.•MnP directly decomposed various cellulosic components to produce reducing sugar.•MnP-driven MnIII-acetate complex seemed to be essential for cellulolytic activity.•In addition, MnP boosted cellulase activity on carboxymethyl cellulose and Avicel®.•The results would contribute to construct economically feasible biorefinery system. Herein, it was unearthed that manganese peroxidase (MnP) from Phanerochaete chrysosporium, a lignin-degrading enzyme, is capable of not only directly decomposing cellulosic components but also boosting cellulase activity. MnP decomposes various cellulosic substrates (carboxymethyl cellulose, cellobiose [CMC], and Avicel®) and produces reducing sugars rather than oxidized sugars such as lactone and ketoaldolase. MnP with MnII in acetate buffer evolves the MnIII-acetate complex functioning as a strong oxidant, and the non-specificity of MnIII-acetate enables cellulose-decomposition. The catalytic mechanism was proposed by analyzing catalytic products derived from MnP-treated cellopentaose. Notably, MnP also boosts cellulase activity on CMC and Avicel®, even considering the cellulolytic activity of MnP itself. To the best of the authors’ knowledge, this is the first report demonstrating a previously unknown fungal MnP activity in cellulose-decomposition in addition to a known delignification activity. Consequently, the results provide a promising insight for further investigation of the versatility of lignin-degrading biocatalysts.